USE OF ErbB RECEPTOR LIGANDS IN TREATING DIABETES

Abstract: The invention provides methods for treating pancreatic dysfunction, particularly diabetes, in mammals using ErbB receptor ligands, such as heregulin, betacellulin, and EGF. Methods of treating such conditions using anti-ErbB receptor agonist antibodies are further provided. The methods of the invention may be performed by direct administration of such therapeutically useful agents to mammals, or alternatively, by exposing certain pancreatic cell types to such agents in vitro and subsequently transplanting the treated cells to a mammal.

Description: LSE OF ErbB RECEPTOR LIGANDS IN TREATING DIABETES Field of the Invention This invention relates to the use of ErbB receptor hgands and ErbB receptor antibodies in treating diabetes and other conditions associated with pancreatic dysfunction Background of the Invention The ErbB Receptor and Ligand Family Transduction of signals that regulate cell growth and differentiation is regulated m part by phosphorylation of vanous cellular proteins Protein tyrosme kmases are enzymes that catalyze this process Receptor protem tyrosme kmases are believed to direct cellular growth via hgand-stimulated tyrosme phosphorylation of intracellular substrates The ErbB receptor family belongs to the subclass I receptor tyrosme kmase superfamily and includes four distmct receptors includmg epidermal growth factor receptor (EGFR or ErbB 1 ) ErbB2 (HER2 or pl 85 ne ° ). ErbB3 (HER3) and ErbB4 (HER4 or tyro2) EGFR or ErbB 1 has been causally implicated m human malignancy and. m particular, increased expression of thi- gene has been observed in more aggressive carcinomas of the breast, bladder, lung and stomach Increased EGFR expression has been reported to be often associated with increased production of the EGFR ligand. transforming growth factor-alpha (TGF-alpha). bv the same tumor cells, resulting m receptor activation by an autocπne stimulatory pathway [Baselga et al . Pharmac Ther 64 127-154 (1994)] Monoclonal antibodies directed against the EGFR, or its hgands TGF-alpha and EGF. have been evaluated as therapeutic agents m the treatment of such malignancies. [See. e g . Baselga et al . sup ra. Masui et al . Cancer Reseω ch 44 1002-1007 (1984). Wu et al . J Clin Invest 95 1897- 1905 ( 1995)] The second member of the class I subfamily, pl85 neu , was originally identified as the product of the transforming gene from neuroblastomas of chemically treated rats The neu gene (also called erbB2 and HER2) encodes a 185 kDa receptor protein tyrosme kmase Amplification and or overexpression of the human ErbB2 gene correlates with a poor prognosis in breast and ovaπan cancers [Slamon et al . Science 235 177-182 (1987), and Slamon et al . Science 244 707-712 (1989), US Patent 4,968.603] Overexpression of ErbB2 has been observed with other carcinomas including carcinomas of the stomach, endometrmm. salivary gland, lung, kidney colon and bladder Accordingly, Slamon et al in U S Patent No 4,968.603 describe and claim vanous diagnostic assavs for determining ErbB2 gene amplification or expression m tumor cells Antibodies directed against the rat pl85 neu and human ErbB2 gene products have been descnbed For instance. Drebin et al . Cell 41 695-706 (1985), Meyers et al , Methods En∑x 198 277-290 ( 1991). and WO 94/22478 descnbe antibodies directed against the rat gene product. pl85 neu Hudziak et al . Mo! Cell Biol 9 1 165- 1 172 (1989) descnbe the generation of a panel of antι-ErbB2 antibodies which were charactenzed using the human breast tumor cell line SKBR3 Other antι-ErbB2 antibodies have also been reported m the literature [See. e g , US Patents 5.821.337 and 5.783.186. WO 94/00136, Taghabue et al Ant J Cancel 47 933-937 (1991 ). McKenzie et al . Oncogene 4 543-548 ( 1989) Mater et al . Cancel Res 51 5361-5369 (1991 ). Bacus et al . Moleculai Cat cmogenesis 3 350-362 (1990). Xu et al . Int J Cancer 53 401-408 ( 1993), Kasprzyk et al . Cancel Reseai ch 52 2771-2776 ( 1992) Hancock et al . Cancel Research 51 4575-4580 ( 1991 ), Shawver et al . Cancer Research 54 1367-1373 (1994) Arteaga et al . Cancer Research 54 3758-3765 ( 1994). Harwerth et al . J Biol Chem 267 15160-15167 (1992)] A further related gene, called erbB3 or HER3, has also been described See U S Patent No 5.183,884 and 5.480.968. Kraus et al Pi oc Nat! Acad Sci USA 86 9193-9197 ( 1989). EP patent application number 444.961A1. and Kraus et al. Proc Nat I Acad Set USA 90.2900-2904 ( 1993) Kraus et al. (1989) discovered that markedly elevated levels of erbB3 mRNA were present in certain human mammary tumor cell lines indicating that erbB3. like erbBl and erbB2. may play a role in human malignancies. Also, Kraus et al.. supra (1993) showed that EGF- dependent activation of the ErbB3 catalytic domain of a chimeπc EGFR/ErbB3 receptor resulted in a proliferative response in transfected NIH-3T3 cells. This is now believed to be the result of endogenous ErbBl or ErbB2 m NIH- 3T3. Furthermore, these researchers demonstrated that some human mammary tumor cell lines display a significant elevation of steady-state ErbB3 tyrosme phosphorylation further indicating that this receptor may play a role in human malignancies. The role oferbB3 in cancer has been explored by others. It has been found to be overexpressed in breast [Lemoine et al.. Br J Cancer 66: 11 16-1 121 ( 1992)], gastrointestinal [Poller et al.. J. Pathol 168:275-280 (1992), Rajkumer et aL. Pathol 170.271-278 ( 1993). and Samdas et al., Int J Cancer 54.935-940 (1993)], and pancreatic cancers [Lemoine et al. J Pathol 168:269-273 (1992): Fness et al. Clinical Cancer Research 1.1413-1420 (1995)]. The class I subfamily of epidermal growth factor receptor protem tyrosme kmases has been further extended to include the ErbB4 receptor. [See EP patent application number 599.274: Plowman et al.. Proc Nαtl. Acαd Sci. USA 90: 1746-1750 (1993): and Plowman et al.. Nature 366:473-475 (1993)] Plowman et al. found that increased ErbB4 expression closely correlated with certain carcinomas of epithelial origin, including breast adenocarcmomas. Diagnostic methods for detection of human neoplastic conditions (especially breast cancers) which evaluate ErbB4 expression are described m EP Appln. No. 599.274 Vanous hgands which bind and/or activate such ErbB receptors have been descnbed in the literature. The hgands include the polypeptides referred to as EGF [Savage et al../. Biol. Chem. 247 ' ■ " '612-7 '621 (1972)]. TGF-alpha [Marquardt et al.. Science 223: 1079-1082 (1984)], amphiregulin [Shoyab et al.. Science 243: 1074-1076 (1989); Kimura et al, Nature 348:257-260 (1990): Cook et al., Mol. Cell. Biol. 11 :2547-2557 (1991)], hepann-bmding EGF (HB-EGF) [Higashiyama et al. Science 251:936-939 (1991)], betacellulin [Shmg et al. Science 259: 1604-1607 (1993)], andepiregulιn [Toyoda etal.J Biol Chem 270:7495-7500 (1995)]. ErbBl is bound by six different Hgands; epidermal growth factor (EGF). TGF-alpha. amphiregulin, HB-EGF. betacellulin. and epiregu n. [See also, e.g., Groenen et al, Growth Factors 1 1.235-257 (1994)]. A family of heregulin proteins resulting from alternative splicing of a single gene are hgands for ErbB3 and ErbB4. As discussed further below, the heregulin family includes NDFs. GGFs. and ARIA [Groenen et al.. Growth Factors 1 1 :235-257 (1994); Lemke. λlolec. & Cell Neurosc 7:247-262 ( 1996). Lee et al.. Pharm Rev. 47:51-85 ( 1995)] . Further ErbB hgands have been identified- neuregulιn-2 (NRG-2) which is reported to bind either ErbB3 or ErbB4 [Chang et al. Nature 387.509-512 ( 1997): Carraway et al., Nature 387.512-516 ( 1997)] and neuregulιn-3 which binds ErbB4 [Zhang et al. Proc Nαtl Acαd Sci 94-9562-9567 (1997)]. HB-EGF. betacellulin. and epiregulin also bmd to ErbB4 While EGF and TGF-alpha do not bind ErbB2. EGF stimulates ErbBl and ErbB2 to form a heterodimer, which activates ErbB l and results in transphosphorylation of ErbB2 in the heterodimer. Dimeπzation and/or transphosphorylation appears to activate the ErbB2 tyrosme kinase. Likewise, when ErbB3 is co-expressed with ErbB2. an active signaling complex is formed and antibodies directed against ErbB2 are capable of disrupting the complex. [Sliwkowski et al. J Biol Chem 269: 14661-14665 (1994)]. Additionally, the affinity of ErbB3 for heregulin is increased to a higher affinity state when co-expressed with ErbB2. [Leu et al.../ Ne roscience 15: 1329- 1340 (1995); Morπsey et aL. TOc Nαtl Acαd Su 92.1431-1435 ( 1995) and Lewis et al. Cancer Research 56: 1457- 1465 ( 1996) with respect to the ErbB2-ErbB3 protem complex], ErbB4. like ErbB3. forms an active signaling complex with ErbB2. [Carraway et al. Cell 78:5-8 ( 1994)] Holmes et al isolated and cloned a famtlv ot polypeptide activators for the ErbB2 receptor which they called heregulin-alpha (HRG-alpha) heregulm-beta 1 (HRG-betal ). hereguhn-beta2 (HRG-beta2), heregulιn-beta2-lιke (HRG-beta2-hke), and hereguhn-beta3 (HRG-beta3) [See Holmes et al , Science 256 1205-1210 (1992), WO 92/20798. and U S Patent No 5 367.060] The 45 kDa polypeptide. HRG-alpha, was punfied from the conditioned medium of the MDA-MB-231 human breast cancer cell line These researchers demonstrated the ability of the punfied heregulin polypeptides to activate tyrosme phosphorylation ol the ErbB2 receptor in MCF7 breast tumor cells Furthermore the mitogemc activity of the heregulin polypeptides on SK-BR-3 cells (which express high levels of the ErbB2 receptor) was illustrated While hereguhns are substantially identical in the first 213 ammo acid residues, they are classified into two major tvpes. alpha and beta based on two \anant EGF-like domams which differ in their C-terminal portions Nevertheless, these EGF-like domains are identical in the spacing of six cvsteine residues contained therein Based on an ammo acid sequence comparison. Holmes et al found that between the first and sixth cysteines in the EGF-like domain. HRGs were 45% similar to hepann-bmdmg EGF-like growth factor (HB-EGF), 35% identical to amphiregulin (AR), 32% identical to TGF-alpha and 27% identical to EGF The 44 kDa neu differentiation factor (NDF), which is the rat equivalent of human HRG. was first descnbed by Peles et al Cell. 69 205-216 ( 1992). and Wen et al , Cell, 69 559-572 ( 1992) Like the HRG polypeptides. NDF has an immunoglobulin (Ig) homology domam followed by an EGF-like domam and lacks a N-terminal signal peptide Subsequently. Wen et al . Mol Cell Biol , 14(3) 1909-1919 (1994) earned out "exhaustive cloning" to extend the family of NDFs This work revealed six distinct fibroblastic pro-NDFs Adopting the nomenclature of Holmes et al , the NDFs are classified as either alpha or beta polypeptides based on the sequences of the EGF-like domains These researchers conclude that different NDF isoforms are generated by alternative splicing and perform distmct tissue- specific functions See also EP 505 148, WO 93/22424, and WO 94/28133 concerning NDF Falls et al , Cell, 72 801-815 (1993) descnbe another member of the heregulm family which they call acetylcholme receptor inducmg activity (ARIA) polypeptide The chicken-denved ARIA polypeptide stimulates synthesis of muscle acetylcholme receptors See also WO 94/08007 ARIA is a type I heregulin with a beta type EGF domam Marchionni et al , Nature 362 312-318 ( 1993 ) identified several bovine-denv ed proteins which they call glial growth factors (GGFs) These GGFs share the Ig-hke domain and EGF-like domain with the other heregulin protems descnbed above, but also have an amino-termmal krmgle domain GGFs generally do not have the complete glycosylated spacer region between the Ig-hke domain and EGF-like domain Only one of the GGFs. GGFII, possessed a N-termmal signal peptide See also WO 92/18627 WO 94/00140 WO 94/04560. WO 94/26298. and WO 95/32724 which refer to GGFs and uses thereof Ho et al , in J Biol Chem 270(4) 14523-14532 (1995), describe another member of the heregulm family called sensory and motor neuron-derived factor (SMDF) This protem has an EGF-like domain charactenstic of all other heregulin polypeptides but a distinct N-termmal domam The maior structural difference between SMDF and the other heregulin polypeptides is that SMDF lacks the Ig-hke domain and the "glyco ' spacer charactenstic of all the other heregulin polypeptides Another feature of SMDF is the presence ot two stretches ol hydrophobic ammo acids near the N-terminus While heregulm polypeptides were first identified based on their ability to activate the ErbB2 receptor (see Holmes et al , supra), it was discovered that certain ovarian cells expressing neu and neu-transfected fibroblasts did not bind or cross-link to NDF nor did they respond to NDF to undergo tvrosine phosphorylation (Peles et al . EMBO J 12 961-971 (1993)) This indicated another cellular component was necessary for confemng full heregulm responsiveness Carraway et al subsequently demonstrated that " -rHRG β 1 , 77 _, 44 bound to NIH-3T3 fibroblasts stably transfected with bovine erb B3 but not to non-transfected parental cells Accordingly, the investigators suggested that ErbB3 is a receptor for HRG and mediates phosphorylation of mtnnsic tyrosme residues as well as phosphorylation of ErbB2 receptor in cells which express both receptors Carraway et al . J Biol Chem 269(19) 14303-14306 ( 1994) Sliwkowski et al , J Biol Chem 269(20) 14661-14665 ( 1994) found that cells transfected with ErbB3 alone show low affinities for heregulm. whereas cells transfected with both ErbB2 and ErbB3 show higher affinities This observation correlates with the "receptor cross-talking" described previously by Kokai et al . Cell 58 287-292 (1989). Stern etal . EMBOJ 7 995-1001 (1988). and King etal , 4 13-18 (1989) These researchers found that binding of EGF to the ErbB l resulted m activation of the ErbBl kmase domain and cross-phosphorylation of HER2 pi 85 This is believed to be a result of ligand- induced receptor heterodimeπzation and the concomitant cross- phosphorylation of the receptors within the heterodimer [Wada et al . Cell 61 1339-1347 (1990)] HΓR4 HΓR^ HFR . Plowman and his colleagues have similarly studied pi 85 ,pl 85 activation They expressedp 185 alone, pl85 HERJ alone, or the two receptors together in human T lymphocytes and demonstrated that heregulm is HFR4 HER^ capable of stimulating tyrosme phosphorylation of pl85 but could only stimulate pi 85 phosphorylation m cells expressing both receptors [Plowman et al . Nature 336 473-475 (1993)] Other Biological Roles of ErbB Receptor Ligands Other biological role(s) of vanous ErbB ligands have been investigated by several groups For example, betacellulin has been reported to exhibit growth-promoting activity m vascular smooth muscle cells and retmal pigment epithelial cells [Shmg et al . supiaf Falls et al , supra, found that ARIA plays a role m myotube differentiation, namely affecting the synthesis and concentration of neuro transmitter receptors m the postsynaptic muscle cells of motor neurons Corfas and Fischbach demonstrated that ARIA also increases the number of sodium channels m muscle [Corfas and Fischbach. J Neuroscience, 13(5) 2118-2125 (1993)] It has also been shown that GGFII is mitogemc for subconfluent quiescent human myoblasts and that differentiation of clonal human myoblasts m the continuous presence of GGFII results m greater numbers of myotubes after six days of differentiation [Sklar et al . J Cell Biochem , Abst W462. 18D. 540 (1994)] See also WO 94/26298 published November 24. 1994 Holmes et al . upia found that HRG exerted a mitogemc effect on mammary cell lines (such as SK-BR-3 and MCF-7) The mitogemc activity of GGFs on Schwann cells has also been reported [See. e g . Brockes et al . J Biol Chem 255( 18) 8374-8377 ( 1980). Lemke and Brockes, J New osci 4 75-83 ( 1984), Brockes et al . J Neuroscience 4( 1 ) 75-83 (1984) Brockes et al . Ann Neurol 20(3) 317-322 (1986), Brockes. J , Methods in Enzv 147 217-225 (1987) and Marchionm et al , supra] Pmkas-Kramarski et al found that NDF seems to be expressed in neurons and g al cells m embryonic and adult rat brain and pnmary cultures of rat bram cells, and suggested that it may act as a survival and maturation factor for astrocytes [Pinkas-Kramarski et al . PNAS, USA 91 9387-9391 (1994)] Meyer and Birchmeier. PNAS, USA 91 1064- 1068 ( 1994) analyzed expression of heregulin during mouse embryogenesis and in the perinatal animal usmg in situ hybndization and Rnase protection experiments See also Meyer etal .Development 124( 18) 3575-3586 (1997) Similarly, Damlenko et al . Abstract 3101. FASEB 8(4-5) A535 ( 1994) and Danilenko et al . Journal of Clinical Investigation 95(2) 842-851 ( 1995 ), found that the interaction of NDF and the ErbB2 receptor is important in directmg epidermal migration and differentiation during wound repair Ram et al . Joui nal ofCellulai Plnsiologv 163 589-596 (1995) evaluated the mitogemc activity of NDF on the immortalized human mammary epithelial cell line MCF- 10A Damlenko et al . J Chn Invest 95 842-851 ( 1995) investigated whether NDF would influence epidermal migration in an m vivo model of excistonal deep partial- thickness wound repair It is reported that there were no statistically significant differences m proliferating basal and superbasal keratinocytes in control wounds vs wounds treated with rhNDF-α - Mankovskv et al , Oncogene 10 1403-1411 (1995) studied the prohferativ e responses of an aneuploid BALB/MK continuous keratinocyte cell lme and evaluated the effects of α- and β- isoforms of NDF on epidermal keratinocytes The potential role(s) that the various ErbB ligands may play m pancreatic cell proliferation and differentiation has also been reported bv several investigators Islet cells (also referred to as Islets of Langerhans) m the pancreas are known to produce the hormones insulin and glucagon Such islet cells are believed to be denved from stem cells m the fetal ductular pancreatic endothe um [Pictet and Rutter, "Development of the embrvonic pancreas " ', Endocrinology Handbook of Phxsiologx, 1972. Amencan Physiological Society Washington D C . pages 25-66] In particular, dunng development, the pancreas forms a system of tubules composed of a single layer of undifferentiated cells, which may then differentiate into duct cells, acmar cells or islet cells [See. e g . LeDouann. Cell. 53 169-171 (1998). Tettelman. Recent Pi og Hormone Res 47 259-297 (1991)] There are several different types of islet cells which can be identified histologically. including cells referred to as alpha cells and beta cells Insulin is synthesized in the pancreatic islet by the beta cells In various circumstances, the islet beta cells mav fail to secrete sufficient amounts of insulin eventually leading to abnormally high levels of glucose in the blood (a condition often referred to as hyperglycemia) Control of insulin production at the cellular level is achieved in the beta cells through regulatory mechanisms operating at the transcπptional. trans lational. and post- translational levels [Sjoholm J hit Med . 239 211-220 (1996)] Insulin has a vanety of biological activities in mammals, some of which are tissue specific For instance, insulin may enhance milk production m the mammary gland, stimulate fat synthesis m the liver, promote the transport of glucose into muscle tissue and stimulate growth of connective tissues Insulin deficiency in mammals can result in senous pathological conditions For example, m Type I diabetes, the pancreas typically produces little or no insulin Type I diabetes is generally characterized as a T cell mediated autoimmune disease in which pancreatic beta cells are typically destroyed The disease usuallv affects children and adolescents, but may occur at anv age Vanous environmental triggers, e g , certain viruses or dietary components, have been proposed to initiate the autoimmune process, in which T cells are thought to plav an important role [Akerblom et al .Diabetes/Metabolism Reviews. 14 31-67 ( 1998)] Susceptibility or resistance to Type I diabetes may also be dependent upon the genetic makeup of the individual [Tisch et al . Cell. 85 291-297 ( 1996)] For a general review, see Rabmovitch et al . Prevention and Treatment of Diabetes and Its Complications. 82 7 39-755 (1998) In the condition known as Type II diabetes, the pancreas will generally produce some insulin, but the amount secreted is insufficient for the mammal to maintain physiologically acceptable glucose levels Type II diabetes is the more common type of diabetes and affects millions of individuals, many of whom are unaware that they have the condition This type of diabetes is usually characterized by three separate but interrelated defects An affected individual may have one or all of these defects and varying degrees These defects are insulin resistance, impaired insulin secretion, and mappropnate release of glucose bv the liver Yet another form of diabetes is referred to as gestational diabetes This type of diabetes is typically a diabetic condition that is first diagnosed m an individual dunng pregnancy and resolves after delivery The further complications of such diabetic conditions are varied and include small and large-caliber blood vessel damage and peripheral nerve damage which m turn can increase risks of heart attack stroke, blindness and kidney failure Vanous investigators have reported on the effects of particular EGF, heregulm and heregulin-related polypeptides on islet cells In WO 95/19785 published July 27. 1995 methods for treating diabetes mellitus are descnbed wherein a combination of a gastnn CCK receptor ligand and an EGF receptor ligand (e g , TGF-alpha) are administered in amounts sufficient to effect differentiation of pancreatic islet precursor cells to mature msulin- secreting cells WO 95/19785 teaches that the TGF-alpha polypeptide was not capable of stimulating differentiation ot the islet precursor cells when administered alone In WO 97/ 17086 published Mav 15 1997. it is reported that particular betacellulin proteins were capable of promoting differentiation of a pancreatic cell line. AR42J (rat cells derived from a chemically induced pancreatic tumor) mto insulm-producing beta cells In the WO 97/ 17086 application, it is also reported that other heregulin family members like EGF TGF-alpha and FGF failed to effectively induce such differentiation in the AR42J cells [See also. Ishiyama et al . Diabetologia. 41 623-628 ( 1998), Mashima et al . J Clin Invest 97 1647-1654 (1996)] The betacellulin proteins tested in such expenments. while showing some differentiation activity in the AR42J cells, did not have growth factor (pro ferative) activity [Ishiyama et al , supra ] The effects of such ligands on other pancreatic msulinoma cell lines have also been described in the literature Huotan et al report that betacellulin exhibited a mitogemc effect on INS- 1 cells in . iti o. while EGF. TGF-alpha and TGF-beta were inactive [Huotan et al . Endocrinology 139 1494- 1499 ( 1998) ] It was further reported that neither betacellulin. EGF TGF-alpha or TGF-beta affected the insulin content of the INS- 1 cells The betacellulin had no mitogemc effect on RINm5F cells, whereas EGF and TGF-alpha were slightly mitogemc [Huotan et al , supra ] Watada et al have investigated some of the transcnption factors believed to be important for insulin gene expression in islet cells [Watada et al . Diabetes 45 1826-1831 (1996) ] In particular, Watada et al examined the transcnption factor PDX- 1. a factor found to appear before insulin dunng ontogeny of the mouse pancreas and whose expression becomes restricted to pancreatic beta cells m the adult animal The PDX- 1 gene was introduced mto α TCI 6 cells and the changes m the gene expression pattern were observed when the cells were treated with vanous growth factors Watada et al report that betacellulin was capable of inducing endogenous insulin and glucokinase gene expressions m the PDX- 1 -expressing α TC 1 6 cells, but that the growth factors TFG-alpha. TFG- β, EGF. IGF-I and bFGF had no such effect Summary of the Invention The present invention concerns compositions and methods for treating pancreatic dysfunction, particularly diabetes, in mammals The invention is based in part, on the identification of ErbB receptor ligands testing positive m vanous assays for the expression or secretion of insulin or expression of transcnption factors or markers unique for pancreatic beta cells Thus the ErbB receptor ligands descnbed herein are thought to be useful drugs for the treatment of conditions associated with insulin deficiency In one embodiment, the invention provides methods of treating conditions in mammals associated with pancreatic dysfunction, and particularly treating conditions in mammals associated with impaired beta cell function In a preferred embodiment the condition being treated is diabetes, and even more preferabh Type I diabetes The methods include administering to a mammal in need of such treatment an effective amount of ErbB receptor ligand A preferred ligand for use m the methods is betacellulin Optionally, the methods of treatment compnse exposing mature beta cells or beta precursor cells to an effective amount of ErbB receptor ligand The cells treated vivo may then be administered to the mammal using suitable transplantation techniques In another embodiment, the invention provides methods of inducing or stimulating proliferation of beta precursor cells or mature beta cells. The methods include exposing beta precursor cells or mature beta cells to an effective amount of ErbB receptor ligand The invention further provides methods of inducing or stimulating beta precursor cell differentiation. In the methods, beta precursor cells or undifferentiated tissues containing such precursor cells are exposed to an effective amount of ErbB receptor ligand The invention also provides a composition comprising a ErbB receptor ligand and a carrier. Preferably, the earner is a pharmaceutically acceptable earner Methods of preparing such compositions are provided, and include admixing an effective amount of the ErbB receptor ligand with the earner The invention still further provides a pharmaceutical product or article of manufacture comprising a composition that includes an effective amount of ErbB receptor ligand. a container that includes such composition and a label affixed to the container, or a package insert, refernng to or providing instructions for use of said ErbB receptor ligand m the therapeutic methods disclosed herem. In any or all of the methods and compositions referred to above, the invention provides for the use and employment ot antibodies, preferably agonist antibodies, against one or more ErbB receptors Brief Description of the Drawings Figure 1 shows the results of the assay descnbed in Example 1 examining the effect of the ErbB receptor ligands. HB-EGF ("rh.HB-EGF"), heregulm ("rh.HRG"), amphiregulin ("rh.AR"), EGF ("rh.EGF"). TGF-alpha ("rh.TGF-a"). and betacellulin ("rh.BTC"), on expression of vanous markers (identified m the figure) m cultured primary munne fetal pancreatic cells Figure 2 shows a bar diagram illustrating the effect (measured as fold change of expression) of HB-EGF on marker expression - RPL19, NeuroD, Pax4, PDX-1 , insulin, Glut2, GLK. Pax6, Glucagon, ISL1. Amylase, Somatostatin. and Cytoker 19 Figure 3 shows a bar diagram illustrating the effect (measured as fold change of expression) of heregulin on marker expression - RPL19. NeuroD, Pax4. PDX-1, insulin, Glut2. GLK. Pax6. Glucagon. ISL1. Amylase, Somatostatin. and Cytoker 19 Figure 4 shows a bar diagram illustrating the effect (measured as fold change of expression) of amphiregulin on marker expression - RPL19. NeuroD. Pax4. PDX- 1. msulm. Glut2. GLK. Pax6. Glucagon. ISL1, Amylase. Somatostatin. and Cytoker 19 Figure 5 shows a bar diagram illustrating the effect (measured as fold change of expression) of EGF on marker expression - RPL19. NeuroD. Pax4. PDX-1. msulm, Glut2. GLK. Pax6, Glucagon. ISL1. Amylase, Somatostatm. and Cytoker 19 Figure 6 shows a bar diagram illustrating the effect (measured as fold change of expression) of TGF-alpha on marker expression - RPL19, NeuroD. Pax4. PDX-1. insulin. Glut2. GLK. Pax6. Glucagon, ISL1. Amylase. Somatostatin. and Cytoker 19 Figure 7 shows a bar diagram illustrating the effect (measured as fold change of expression) of betacellulin on marker expression - RPL19. NeuroD. Pax4. PDX- 1. msulm, Glut2. GLK. Pax6, Glucagon. ISL 1. Amylase, Somatostatin. and Cytoker 19 Figure 8 shows representative sections (at 20X) through pancreatic tissue from an untreated wild type animal (a), and a wild type (b), heregulm (-/-) (c), ErbB2 (+/-) (d). and ErbB3 (- -) animal (e) that received heregulm treatment The sections are from animals that received heregulm treatment for 14 days except m the case of the heregulm (- -) treated animal which was dosed only for 5-6 days The presence of ductal hyperplasia (shown by arrows) was most evident in the wild type and ErbB2 and ErbB3 (-<-) animal groups, possibly reflective of the longer exposure to heregulm Detailed Description of the Invention I.Definitions The term "ErbB receptor " as used herein refers to a receptor protein kinase which belongs to the ErbB receptor family and typically, in its native sequence form, compnses an extracellular domain, which may bmd to one or more ErbB ligands (defined below), a lipophihc transmembrane domain, an intracellular tyrosme kinase domam, and a carboxyl-termmal signaling domain having one or more tyrosme residues which can be phosphorylated The term "ErbB receptor " includes native sequence polypeptide receptors and ammo acid sequence vanants thereof The ErbB receptor may be isolated from a vanety of sources, such as from human tissue types or from another source, or prepared by recombinant and or synthetic methods ErbB receptors contemplated by the invention include but are not limited to. the EGFR. ErbB2. ErbB3. and ErbB4 receptors "ErbBl " and "EGFR" refer to the receptor disclosed m. for instance, Carpenter et al., Ann Rev Bwchem 56.881-914 (1987), including naturally occurring mutant forms thereof, such as the deletion mutant descnbed in Humphrey et al . Proc Nad Acad Sci 87 4207-421 1 (1990) ErbBl refers to the gene encoding the ErbBl protem "ErbB2 " and "HER2" refer to the receptor descnbed. for instance, in Semba et al , Proc Natl Acad Sci 82:6497-6501 ( 1985) and Yamamoto et al , -Vα.w-e 319.230-234 (1986) (GenBank accession number X03363) The term erbB2 refers to the gene encoding human ErbB2 and neu refers to the gene encoding rat pi 85"™. "ErbB3 " and "HER3" refer to the receptor as disclosed, for instance, m US Patents 5,183,884 and 5,480,968, as well as Kraus et al , Proc Natl Acad Sci 86:9193-9197 (1989) "ErbB4" and "HER4" refer to the receptor as disclosed, for mstance, in EP Patent Application 599,274, Plowman et al . Proc Natl Acad Sci 90- 1746-1750 (1993). and Plowman et al., Nature 366 473-475 (1993). An "ErbB heterodimer" as referred to herein means a noncovalently associated ohgomer compnsmg at least two different ErbB receptors. Such complexes may form when a cell expressing the two receptors is exposed to ErbB lιgand(s) and can be isolated by lmmunoprecipitation and analyzed by SDS-PAGE as descnbed in Sliwkowski et al . J Biol Chem 269 14661- 14665 (1994) Examples of such heterodimers include EGFR-ErbB2. ErbB2-ErbB3. and ErbB3-ErbB4 complexes The terms "ErbB receptor ligand" and "ErbB ligand" refer to a polypeptide which binds to and/or activates one or more ErbB receptors The term "ErbB ligand" includes native sequence polypeptide ligands and ammo acid sequence vanants thereof The ErbB ligand may be isolated from a vanety of sources, such as from human tissue types or from another source, or prepared by recombinant and/or synthetic methods Preferably, for use in the methods disclosed herein, the ErbB ligand is prepared by recombinant methods Binding of a candidate ErbB ligand to one or more ErbB receptors can be readily determined using known assays, such as those descnbed in WO 98/35036 published August 13. 1998 Activation of an ErbB receptor refers to signal transduction (e g.. that caused by an intracellular kinase domain of an ErbB receptor phosphorylating tyrosme residues m the ErbB receptor or a substrate polypeptide), mediated by ErbB ligand binding to an ErbB heterodimer comprising the ErbB receptor of interest Generally, this will involve binding of an ErbB ligand to an ErbB heterodimer which activates a kmase domain of one or more of the ErbB receptors in the heterodimer and thereby results in phosphorylation of tyrosme residues in one or more of the receptors, and/or phosphorylation of tyrosme residues in additional substrate polypeptιde(s) ErbB receptor phosphorylation can be quantified using vanous tyrosme phosphorylation assays. including those descnbed m WO 98/35036 published August 13. 1998 ErbB ligands contemplated by the invention include but are not limited to. the polypeptides referred to below and descnbed in. for example, the following respective journals and patents epidermal growth factor (EGF) [Savage et al . J. Biol Chem 247 7612-7621 ( 1972)]. transforming growth factor-alpha (TGF-alpha) [Marquardt et al . Science 223: 1079-1082 (1984)]: amphiregulin [also known as a Schwanoma derived growth factor or keratmocyte autocnne growth factor; Shoyab etal., Sconce 243 1074-1076 (1989). Kimura etal. Nature 348.257-260 (1990): Cook etal.Mol Cell. Biol 1 1.2547-2557 (1991)]. betacellulin [Shmg et al.. Science 259.1604-1607 ( 1993). Sasada et al . Biochem Biophvs Res Commun 190: 1173 (1993)]. hepann-bindmg epidermal growth factor (HB-EGF) [Higashiyama et al . Science 251 "936-939 (1991)], epιregulm [Toyoda etal..J -3.o/ Chem 270 7495-7500 ( 1995). Komurasaki et al.. Oncogene 15:2841-2848 (1997)]. neuregulm-2 (NRG-2) [Carraway et al., Nature 387 512-516 (1997)], neuregulm-3 (NRG-3) [Zhang et al, Proc Natl Acad Sci 94"9562-9567 (1997)]; and heregulm (HRG). an ErbB ligand polypeptide encoded by the heregulin gene product as disclosed in US Patent 5.641.689 or Marchionm et al. Nature 362:312-318 ( 1993) Included within the scope of HRG as that term is used herein are heregulin-alpha. heregulm-beta 1 , hereguhn-beta2, and heregulιn-beta3 [Holmes et al, Science 256: 1205-1210 (1992). US Patent 5.641.869]; NDF [Peles et al, Cell 69:205-216 (1992)]; ARIA [Falls et al., Cell 72:801 -815 ( 1993)] . GGF growth factor proteins [Marchionm et al., Nature 362 312-318 ( 1993); SMDF [Ho et al., J Biol Chem 270T4523-14532 (1995); and gamma-heregu n [Schaefer et al.. Oncogene 15: 1385-1394 (1997)]. A "native sequence" polypeptide refers to a polypeptide havmg the same ammo acid sequence as the polypeptide denved from nature. Such native sequence polypeptide may be isolated from nature or can be produced by recombinant and/or synthetic means. The term "native sequence" specifically encompasses naturally-occurring truncated or secreted forms (e.g., an extracellular domain sequence), naturally-occurnng variant forms (e.g., alternatively spliced forms) and naturally-occurnng allelic vanants An "ErbB ligand vanant" or "ErbB receptor ligand vanant" refers to a ligand polypeptide other than native sequence ErbB ligand which binds to and/or activates one or more ErbB receptors and has at least about 80% ammo acid sequence identity with its respective native sequence polypeptide. more preferably at least 90%. and even more preferably at least 95% ammo acid sequence identity ErbB receptor ligand variants include fragments of the native sequence ligand and having a consecutive sequence of at least 5. 10. 15, 20. 25. 30 or 40 ammo acid residues from the native ligand sequence: ammo acid sequence vanants wherein an ammo acid residue has been inserted N- or C- termmal to. or withm. the sequence or its fragment as defined above: and ammo acid sequence variants wherein one or more residues have been substituted by another residue ErbB ligand variants include those contammg predetermined mutations by. e.g.. site-directed or PCR mutagenesis. and denved from various animal species such as rabbit, rat, porcine, non-human primate, equine, muπne. and ovine "Percent (%) ammo acid sequence identity" with respect to the sequences identified herein is defined as the percentage of ammo acid residues in a candidate sequence that are identical with the ammo acid residues m the ErbB ligand polypeptide sequence, after aligning the sequences and introducing gaps, if necessar . to achieve the maximum percent sequence identity, and not considenng any conservative substitutions as part of the sequence identity. Methods for performing sequence alignment and determining sequence identity are known to the skilled artisan, may be performed without undue experimentation, and calculations of % identity values may be obtained with defimteness. For instance, the alignment may be performed using available computer programs, such as WU-BLAST-2 [Altschul et al . Methods in Ennmologi 266 460-480 ( 1996)] and Align 2 [authored by Genentech. Inc and filed with the US Copynght Office on December 10. 1991 ] One may optionally perform the alignment using set default parameters in the computer software programs "Isolated polypeptide" means a polypeptide. such as HRG, which has been identified and separate and/or recovered from a component of its natural environment Contaminant components of its natural environment are materials which would interfere with diagnostic or therapeutic uses tor the polypeptide, and may include proteins, hormones, and other substances In preferred embodiments, the polypeptide will be purified ( 1 ) to greater than 95% by weight of protem as determined by the Lowrv method or other validated protem determination method, and most preferably more than 99% by weight, (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal ammo acid sequence by use of the best commercially available ammo acid sequenator marketed on the filing date hereof, or (3) to homogeneity by SDS-PAGE using Coomassie blue or. preferably, silver stain Isolated polypeptide includes polypeptide in situ within recombinant cells since at least one component of the polypeptide natural environment will not be present Isolated polypeptide includes polypeptide from one species in a recombinant cell culture of another species since the polypeptide in such circumstances will be devoid of source polypeptides Ordmanly, however, isolated polypeptide will be prepared by at least one purification step "Antibodies" ( Abs) and "immunoglobulms' (Igs) are glycopro terns having the same structural charactenstics While antibodies exhibit binding specificity to a specific antigen, immunoglobulms include both antibodies and other antibody-like molecules which lack antigen specificity Polypeptides of the latter kmd are. for example, produced at low levels by the lymph system and at increased levels by myelomas Papain digestion of antibodies produces two identical antigen-binding fragments, called "Fab" fragments, each with a single antigen-binding site, and a residual "Fc" fragment, whose name reflects its ability to crystallize readily Pepsm treatment yields an F(ab '), fragment that has two antigen-combining sites and is still capable of cross- linking antigen "Fv" is the minimum antibody fragment which contains a complete antigen-recognition and -bmdmg site This region consists of a dimer of one heavy cham and one light chain variable domain in tight, non-covalent association It is m this configuration that the three hypervanable regions of each variable domain interact to define an antigen-bindmg site on the surface of the V π -V L dimer Collectively, the six hypervanable regions confer antigen- binding specificity to the antibodv However, even a single variable domain (or half of an F\ comprising only three hypervanable regions specific for an antigen) has the ability to recognize and bind antigen, although at a lower affinity than the entire binding site The Fab fragment also contains the constant domain of the light chain and the first constant domain (CHI) of the heavy chain Fab fragments differ from Fab' fragments by the addition of a few residues at the carboxyl terminus of the heavy chain CHI domain including one or more cysteιne(s) from the antibody hinge region F(ab') 2 antibody fragments ongrnally were produced as pairs of Fab' fragments which have hmge cystemes between them Other chemical couplings of antibody fragments are also known The "light chains' " of antibodies (immunoglobulms) from any vertebrate species can be assigned to one of two clearly distinct types, called kappa and lambda, based on the ammo acid sequences of their constant domains Dependmg on the ammo acid sequence of the constant domain of their heavy chains immunoglobulms can be assigned to different classes There are five major classes of immunoglobulms IgA, IgD. IgE. IgG, and IgM. and several of these may be further divided into subclasses (isotypes). e g , IgGl, IgG2. IgG3. IgG4, IgA. and IgA2 The subunit structures and three-dimensional configurations of different classes of immunoglobulms are well known The term "antibody" herein is used in the broadest sense and specifically covers monoclonal antibodies (includmg full length monoclonal antibodies), polvclonal antibodies, multispecific antibodies (e g , bispecific antibodies), and antibody fragments so long as they exhibit the desired agonistic activity discussed in the present application "Antibodv fragments" compnse a portion of a full length antibody, generally the antigen binding or vanable domam thereof Examples ot antibody fragments include Fab. Fab' F(ab * ),, and Fv fragments, diabodies. linear antibodies, smgle-cham antibody molecules, and multispecific antibodies formed from antibody fragments The term "monoclonal antibody" as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies. 1 e . the individual antibodies compnsmg the population are identical except for possible naturally occurnng mutations that may be present m minor amounts Monoclonal antibodies are highly specific, being directed against a single antigemc site Furthermore, in contrast to conventional (polvclonal) antibody preparations which typically include different antibodies directed against different determinants (epitopes) each monoclonal antibody is directed against a single determinant on the antigen The modifier "monoclonal"" indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requinng production of the antibody by any particular method For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybπdoma method first descnbed by Kohler et al . Nature 256 495 (1975), or may be made by recombinant DNA methods (see. e g , U S Patent No 4,816.567) The "'monoclonal antibodies" may also be isolated from phage antibody libraries using the techniques descnbed in Clackson et al . Nature 352 624-628 (1991) and Marks et al . J Mol Biol 222 581-597 (1991), for example The monoclonal antibodies herein specifically include "chimeπc" antibodies (immunoglobulms) m which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies denved from a particular species or belonging to a particular antibody class or subclass, while the remamder of the cham(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belongmg to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired agonistic activity [U S Patent No 4.816 567. and Morrison et al Pi oc had Acad Sci (75-4 81 6851-6855 (1984)] "Humanized" forms of non-human (e g . munne) antibodies are chimenc antibodies which contain minimal sequence denved from non-human -mrnunoglobulin For the most part humanized antibodies are human immunoglobulms (recipient antibody) in which hypervanable region residues of the recipient are replaced by hypervanable region residues from a non-human species (donor antibodv ) such as mouse, rat, rabbit or non-human primate having the desired specificity, affinity, and capacity In some instances, framework region (FR) residues of the human lmmunoglobulm are replaced by corresponding non-human residues Furthermore, humanized antibodies may compnse residues which are not found m the recipient antibody or in the donor antibody These modifications are made to further refine antibody performance In general, the humanized antibody will compnse substantially all of at least one. and typically two, variable domains, in which all or substantially all of the hypervanable regions correspond to those of a non-human -mrnunoglobulin and all or substantially all of the FRs are those of a human lmmunoglobulm sequence The humanized antibodv optionally also w ill compnse at least a portion of an immunoglobulm constant region (Fc). typically that of a human lmmunoglobulm For further details, see Jones et al . Nature 321 522-525 (1986). Reichmann et al . \atw e 332 323-329 ( 1988). and Presta. Cui i Op Struct Biol 2 593- 596 (1992) "Single-chain F\ "* or ' antibody fragments compnse the V, , and V, domains of antibody, wherem these domains are present m a single polypeptide chain Generally, the Fv polypeptide further comprises a polypeptide linker between the V H and V L domains w hich enables the sFv to form the desired structure for antigen binding For a review of sFv. see Pluckthun in the The Phai macologλ of Monoclonal Antibodies vol 113. Rosenburg and Moore eds Spnnger-Verla New York, pp 269-315 (1994) The term "diabodies " refers to small antibodv fragments with two antigen-bindmg sites, which fragments compnse a heavy chain variable domain ( V H ) connected to a light chain \ anable domain (V L ) in the same polypeptide chain (\ H - \ J By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites Diabodies are described more fullv m. for example, EP 404.097. WO 93/11161. and Holhnger etal . Proc Natl Acad Sci USA 90 6444-6448 ( 1993) The expression linear antibodies, when used throughout this application, refers to the antibodies descnbed m Zapata et al Pi otem Eng 8( 10) 1057- 1062 ( 1995) Briefly, these antibodies comprise a pair of tandem Fv segments (V H -C H 1 -\ -C H 1 ) which form a pair of antigen binding regions Linear antibodies can be bispecific or monospecific "ErbB receptor agonist antibody " ' as used herein refers to an antibody against one or more ErbB receptors which binds to and/ or activates one or more ErbB receptors Binding and/or activation of an ErbB receptor may be determined usmg known assays, such as descnbed herein The term "mature beta cell" refers to a differentiated epithelial cell which, in a normal physiological state, is capable of responding to changes in glucose concentration (between about 2 mM and 20 niM) by secretmg msulm The mature beta cell may further be charactenzed by the expression of insulin, glucokinase and/or PDX-1 The term "beta precursor cell " ' as used herein refers to an epithelial cell capable of division and differentiation into a mature beta cell The beta precursor cell may further be charactenzed by the expression of the gene markers PDX-1 and or Pa\4 and lack of expression of gene markers of non-epithelial ongm (such as vimentm) The terms "treating " ', "therapy" and "treatment" are used in the broadest sense and include prevention (prophylaxis), moderation, reduction and curing of the conditions described herein "An effective amount" refers to that amount of ErbB ligand or ErbB receptor agonist antibody which stimulates or induces proliferation of mature beta cells or beta precursor cells in xitro and/or in \ ivo. or stimulates or induces beta precursor cell differentiation in vitro and/or in vn o Administration "m combination with" one or more further therapeutic agents includes simultaneous (concurrent) and consecutive administration in any order The term "pancreatic dysfunction" refers generally to condιtιon(s) in mammals occurring as a result of a reduction or loss of beta cell function or by a reduction or loss of beta cell mass The pancreatic dysfunction may be more particularly characterized, for example, by deficient levels of msulm in the mammal, deficient means of secreting msulm in the mammal or as a metabolic syndrome The pancreatic dysfunction may be due. for instance, to insufficient differentiation of beta precursor cells mto mature beta cells or destruction of beta cells that can occur ιn. e g , insulitis or autoimmune disease The terms "diabetes"" and "diabetes melhtus" are use in a broad sense and refer generally to the condition or syndrome in mammals associated with msulm deficiency, and include the conditions known in the art as insulin- dependent diabetes (also referred to as Type I diabetes or IDDM), nomnsulm-dependent diabetes (also referred to as Type II diabetes or NIDDM), gestational diabetes, malnutrition-related diabetes (MRD) and matunty-onset diabetes of the young (also referred to as MODY) The term "mammal" refers to any animal classified as a mammal, includmg humans, domestic and farm animals, dogs, horses, cats, etc Preferably, the mammal is human. II. Methods and Compositions of the Invention Applicants have found that various ErbB receptor ligands effectively alter expression of pancreatic cell transcription factors or markers, descnbed in further detail below Generally, precursor (or relatively undifferentiated) cells are identified by the presence or absence of specific cell markers and functionally by their respective ability to differentiate into the appropπate cell type. Marker definition for beta precursor cells is denved. at least in part, by a histological characterization of their ongin and from transcnption factors that are needed for pancreatic formation Edlund. Diabetes 47 1817-1823 (1998). Bouwens, J Pathology 184 234-239 (1998) and Sander et al.. J Mol Med 75 327-340 (1997) provide reviews of pancreatic tissue development and discussions of pancreatic cell markers, particularly expression of the vanous transcription factor markers and the role of such markers as indicia of stages of pancreatic cell development and function It is presently believed that at least a subset of ductular epithelial cells in mammals is capable of givmg nse to functional endocrine cells (m both the fetal pancreas during embryogenesis and during adult life), and thus, the precursors would reasonably be expected to express, for instance, cytokeratm- 19. a marker associated with pancreatic ductal epithelial cells The transcription factor. PDX- 1. is typically expressed in a subset of gut endodermal cells in mammals and the temporal and spatial appearance of these cells is thought to be consistent with such cells being early pancreatic precursor cells. Also, genetic inactivation of PDX-1 may lead to the absence of a pancreas or pancreatic tissue in mammals. Accordingly, a beta precursor cell would reasonably be expected to express PDX-1. Absence of the transcnption factors Pax4. Pax6 and/or NeuroD may lead to the absence of mature beta cells and mature islets, and so likewise, beta precursor cells may reasonably be expected to express one or all of these markers Insulin, glucose transporter 2 (glut2), the transcnption factor ISL1, and glucokmase (GLK) are expressed in mature beta cells. They may also be expressed at a lower level in the beta precursor cells as such cells become committed to differentiation toward the mature beta cell phenotype In the mature islet, each endocrine cell type generally expresses only one of the major hormones - the beta cells express insulin, the alpha cells express glucagon, and the delta cells express somatostatin. In contrast, an islet precursor cell may express the genes encodmg more than one islet hormone Accordingly, the beta precursor cells may also express glucagon and somatostatin The gene encoding the nbosomal protem. RPL19 is expressed in a majonty of cell types and can be used, such as descnbed in the Examples, to represent changes in cell number It is believed that use of ErbB receptor ligands or ErbB receptor agonist antibodies to induce proliferation or growth of mature beta cells will be beneficial to increase msulm secretion in the mammal Expansion of beta cell mass may constitute an important means to compensate for loss or dysfunction of beta cells occurring, for example, in diabetes. As beta precursor cells also appear to be present throughout childhood and adult life in mammals, it is further believed that use of ErbB receptor ligands or ErbB receptor agonist antibodies to induce or stimulate differentiation of such precursor cells mto mature beta cells will be useful in treating conditions associated with insulin deficiency A. Preparation of ErbB Ligands The ErbB ligand (as well as ErbB receptor, which can be used for instance as an immunogen to prepare agonist antibodies) may be prepared by various techniques known in the art. including in vitro polypeptide synthetic methods or m recombinant cell culture using host-vector systems such as descnbed below Optionally, mammalian host cells will be employed, and such hosts may or may not contain post- translational systems torprocessing ErbB ligand preprosequences in the normal fashion If the host cells contain such systems, then it will be possible to recover natural subdomam fragments from the cultures If not. then the proper processmg can be accomplished by transforming the hosts with the required enzyme(s) or by supplying them in an in vitro method However, it is not necessary to transform cells with the complete prepro or structural genes for a selected polypeptide when it is desired to only produce fragments ot the sequences For example, a start codon can be gated to the 5' end ot DNA encoding a ErbB ligand polypeptide. this DNA is used to transform host cells and the product expressed directly as the Met N-termmal lorm (if desired, the extraneous Met may be removed in vitro or by endogenous N- terminal demethionylases) Alternativel . ErbB ligand can be expressed as a fusion with a signal sequence recognized by the host cell which will process and secrete the mature ErbB ligand as is further described below Ammo acid sequence variants of native sequence ErbB ligand can be produced in the same way 1. Isolation of DNA The DNA encoding ErbB ligand may be obtained from any cDNA library prepared from tissue believed to possess ErbB ligand mRNA and to express it at a detectable level An ErbB ligand gene thus may be obtained from a genomic library Libranes can be screened with probes designed to identify the gene of interest or the protein encoded by it For cDNA expression libranes. suitable probes mclude monoclonal or polyclonal antibodies that recognize and specifically bmd to the ligand. oligonucleotides of about 20-80 bases in length that encode known or suspected portion of ErbB ligand cDNA from the same or different species, and/or complementary or homologous cDNAs or fragments thereof that encode the same or a similar gene Appropnate probes for screenmg genomic DNA libranes mclude, but are not limited to. oligonucleotides, cDNAs or fragments thereof that encode the same or a similar gene, and/or homologous genomic DNAs or fragments thereof Screenmg the cDNA or genomic library with the selected probe may be conducted using standard procedures as descnbed in chapters 10-12 of Sambrook et al . Molecular Cloning A Laboratory Manual. (New York Cold Spnng Harbor Laboratory Press (1989) An alternative means to isolate the gene encoding ErbB ligand is to use polymerase chain reaction (PCR) methodology, as descnbed in section 14 of Sambrook et al , supra This method requires the use of oligonucleotide probes that will hybndize to ErbB ligand Strategies for selection of oligonucleotides are descnbed below Another alternative method tor obtaining the gene of interest is to chemically synthesize it using one of the methods descnbed in Engels et al Agneu Chem lnt Ed Engl 28 216-734( 1989) These methods include tπester, phosphite, phosphoramidite and H-Phosphonate methods. PCR and other autopnmer methods, and oligonucleotide syntheses on solid supports These methods may be used if the entire nucleic acid sequence of the gene is known, or the sequence of the nucleic acid complementary to the coding strand is available, or alternatively, if the target ammo acid sequence is known, one may infer potential nucleic acid sequences using known and preferred coding residues for each ammo acid residue An optional method is to use carefully selected oligonucleotide sequences to screen cDNA libraries from vanous tissues The oligonucleotide sequences selected as probes should be ot sufficient length and sufficiently unambiguous that false positives are minimized The actual nucleotide sequence(s) may. for example, be based on conserved or highly homologous nucleotide sequences or regions of ErbB ligand The oligonucleotides may be degenerate at one or more positions The use of degenerate oligonucleotides may be of particular importance where a library is screened from a species in \\ Inch preferential codon usage in that species is not known The oligonucleotide must be labeled such that it can be detected upon hvbπdization to DNA in the library being screened The preferred method of labeling is to use " P-labeled ATP with polynucleotide kmase. as is well known in the art. to radiolabel the oligonucleotide However, other methods may be used to label the oligonucleotide. includmg, but not limited to. biotinylation or enzyme labeling 2.Amino Acid Sequence Variants Ammo acid sequence variants of ErbB receptor ligands can be prepared by introducing appropnate nucleotide changes mto the DNA, or by in vitro synthesis of the desired ligand polypeptide Such variants include, for example, deletions from, or insertions or substitutions of. residues withm the ammo acid sequences of the native sequence ErbB ligand Any combination of deletion, insertion, and substitution can be made to arrive at the final construct, provided that the final construct possesses the desired charactenstics The ammo acid changes also may alter post-translational processes, such as changmg the number of position of glycosylation sites, altenng the membrane anchonng charactenstics. altenng the intra-cellular location of the polypeptide by inserting, deleting, or otherwise affectmg the leader sequence of the native sequence polypeptide. or modifying its susceptibility to pro teolytic cleavage In designmg ammo acid sequence variants of an ErbB ligand. the location of the mutation site and the nature of the mutation will depend on the polypeptide charactenstιc(s) to be modified The sites for mutation can be modified individually or in senes. e g , by ( 1 ) substituting first with conservative ammo acid choices and then with more radical selections depending upon the results achieved. (2) deleting the target residue, or (3) inserting residues of other receptor ligands adjacent to the located site A useful method for identification of certain residues or regions of the polypeptide that are preferred locations for mutagenesis is called "alamne scannmg mutagenesis" as described by Cunningham and Wells (Science.244" 1081- 1085. 1989) Here, a residue or group of target residues are identified (e g.. charged residues such as arg, asp, his, lys, and glu) and replaced by a neutral or negatively charged ammo acid (most preferably alamne or polyalamne) to affect the interaction of the ammo acids with the surrounding aqueous environment in or outside the cell. Those domains demonstratmg functional sensitivity to the substitutions then are refined by mtroducmg further or other vanants at or for the sites of substitution Thus, while the site for mtroducmg an ammo acid sequence vanation is predetermined, the nature of the mutation/, er se need not be predetermined For example, to optimize the performance of a mutation at a given site, ala scannmg or random mutagenesis may be conducted at the target codon or region and the expressed ErbB ligand vanants are screened for the optimal combination of desired activity There are two pnncipal variables m the construction of ammo acid sequence variants the location of the mutation site and the nature of the mutation. These are variants from the native sequence, and may represent naturally occurnng alleles or predetermined mutant forms made by mutating the DNA. either to arrive at an allele or a vanant not found in nature In general, the location and nature of the mutation chosen will depend upon the charactenstic to be modified Ammo acid sequence deletions generally range from about 1 to 30 residues, more preferably about 1 to 10 residues, and typically about 1 to 5 are contiguous The number of consecutive deletions may be selected so as to preserve the tertiary structure of the polypeptide m the affected domam. e g . cvsteine cross-linkmg. beta-pleated sheet or alpha helix Ammo acid sequence insertions include ammo- and or carboxyl- terminal fusions ranging in length from one residue to polypeptides containing a hundred or more residues, as well as intrasequence insertions of single or multiple ammo acid residues Intrasequence insertions may range generally from about 1 to 10 residues, more preferably 1 to 5. and most preferably 1 to 3 Examples of terminal insertions mclude ErbB ligand with an N-termmal methionyl residue (an artifact of the direct expression of ErbB in bacterial recombinant cell culture), and fusion of a heterologous N- terminal signal sequence to the N-terminus of ErbB ligand to facilitate the secretion of mature ErbB ligand from recombmant host cells Such signal sequences generally will be obtained from, and thus be homologous to. the intended host cell species Suitable sequences include STII. tPA or lpp tor E coll. alpha factor for yeast, and viral signals such as herpes gD for mammalian cells Other insertional vanants of ErbB ligand mclude the fusion to the N- or C-termmus of ErbB ligand of an lmmunogenic polypeptide. e g . bactenal polypeptides such as beta-lactamase or an enzyme encoded by the E coll trp locus, or yeast protein, bovine serum albumin, and chemotactic polypeptides C- terminal fusions of ErbB ligand ECD with proteins having a long half-lite such as immunoglobuhn constant regions (or other lmmunoglobulm regions). albumin, or ferntm. as descnbed m WO 89/02922. published 6 April 1989 are contemplated Another group ol variants are ammo acid substitution vanants These vanants have at least one amino acid residue in the polypeptide removed and a different residue inserted m its place The sites of greatest mterest for substitutional mutagenesis mclude sites identified as the active sιte(s) of the polypeptide, and sites where the ammo acids found in ErbB ligands from \ anous species are substantially different in terms of side-chain bulk, charge, and/or hydrophobicity Non-conservative substitutions will entail exchanging a member of one of these classes for another Such substituted residues may be introduced into regions of the polypeptide that are homologous with other receptor gands. or, more preferably, mto the non-homologous regions of the molecule In one embodiment, anv methionyl residue other than the starting methionyl residue of the signal sequence, or any residue located within about three residues N- or C-terminal to each such methionyl residue, is substituted by another residue or deleted Alternatively, about 1-3 residues are inserted adjacent to such sites Any cysteine residues not involved in maintaining the proper conformation of ErbB ligand also may be substituted, generally with seπne. to improve the oxidative stability of the molecule and prevent aberrant cross-linking DNA encoding ammo acid sequence vanants of the ErbB ligand can be prepared by a vanety of methods known in the art These methods mclude. but are not limited to. isolation from a natural source (m the case of naturally occurring amino acid sequence vanants) orpreparation by oligonucleo tide-mediated (site-directed) mutagenesis, PCR mutagenesis, and cassette mutagenesis of an earlier prepared vanant or a non- vanant version These techniques may utilize nucleic acid (DNA or RNA). or nucleic acid complementary to such nucleic acid Oligonucleotide-mediated mutagenesis is an optional method for preparing substitution, deletion, and insertion vanants This technique is known in the art as descnbed by Adelman et al . DNA. 2 183 (1983) Bnefly, DNA is altered by hybndizmg an oligonucleotide encoding the desired mutation to a DNA template, where the template is the single-stranded form of a plasmid or bacteπophage containing the unaltered or native DNA sequence After hybndization. a DNA polymerase is used to synthesize an entire second complementary strand of the template that will thus incorporate the oligonucleotide pnmer, and will code for the selected alteration in the DNA Generally, oligonucleotides of at least 25 nucleotides in length are used An optimal oligonucleotide will have 12 to 15 nucleotides that are completely complementary to the template on either side of the nucleotιde(s) coding for the mutation This ensures that the oligonucleotide will hvbπdize properly to the single-stranded DNA template molecule The oligonucleotides are readily synthesized using techniques known m the art such as that descnbed by Crea et al , Proc Natl Acad Sci 75 L5765 (1978) Smgle-stranded DNA template may also be generated by denatunng double-stranded plasmid (or other) DNA using standard techniques For alteration of the native DNA sequence (to generate ammo acid sequence variants, for example), the oligonucleotide is hybndized to the smgle-stranded template under suitable hybridization conditions A DNA polymenzmg enzyme, usually the Klenow fragment of DNA polvmerase I. is then added to synthesize the complementary strand of the template using the oligonucleotide as a pnmer for synthesis A heteroduplex molecule is thus formed such that one strand ot DNA encodes the mutated form ot the polypeptide. and the other strand (the onginal template) encodes the native, unaltered sequence ot the polypeptide This heteroduplex molecule is then transformed into a suitable host cell, usually a prokaryote such as E coh JM 101 After the cells are grown, they are plated onto agarose plates and screened using the oligonucleotide pnmer radiolabeled with J T-phosphate to identify the bactenal colonies that contain the mutated DNA The mutated region is then removed and placed m an appropriate vector for protein production, generally an expression vector of the type typically employed for transformation of an appropnate host The method descnbed immediately above may be modified such that a homoduplex molecule is created wherein both strands of the plasmid contain the mutatιon(s) The modifications are as follows the smgle-stranded oligonucleotide is annealed to the smgle-stranded template as described above \ mixture of three deoxynbonucleotides. deoxynboadenosine (dATP), deoxynboguanosme (dGTD). and deoxynbothymidme (dTTP), is combined with a modified thio-deoxynbocytosine called dCTP-(aS) (which can be obtained from Amersham Corporation) This mixture is added to the template-oligonucleotide complex Upon addition of DNA polymerase to this mixture, a strand of DNA. identical to the template except for the mutated bases is generated In addition, this new strand of DNA will contain dCTP-(aS) instead of dCTP. which serves to protect it from restnction endonuclease digestion After the template strand of the double-stranded heteroduplex is nicked with an appropnate restnction enzyme, the template strand can be digested with £ oIII nuclease or another appropnate nuclease past the region that contains the sιte(s) to be mutagenized The reaction is then stopped to leave a molecule that is only partially smgle- stranded A complete double-stranded DNA homoduplex is then formed using DNA polymerase in the presence of all four deoxynbonucleotide tnphosphates, ATP, and DNA ligase This homoduplex molecule can then be transformed into a suitable host cell such as E coh JM101, as descnbed above DNA encodmg vanants with more than one ammo acid to be substituted may be generated in one of several ways If the amino acids are located close together m the polypeptide chain, they may be mutated simultaneously using one oligonucleotide that codes for all of the desired amino acid substitutions If. however, the ammo acids are located some distance from each other (separated by more than about ten ammo acids), it is more difficult to generate a single oligonucleotide that encodes all of the desired changes Instead, one of two alternative methods may be employed In the first method, a separate oligonucleotide is generated for each ammo acid to be substituted The oligonucleotides are then annealed to the single-stranded template DNA simultaneously, and the second strand of DNA that is synthesized from the template will encode all of the desired ammo acid substitutions The alternative method involves two or more rounds of mutagenesis to produce the desired mutant The first round is as descnbed for the single mutants wild-type DNA is used for the template, an oligonucleotide encoding the first desired amino acid substιtutιon(s) is annealed to this template, and the heteroduplex DNA molecule is then generated The second round of mutagenesis utilizes the mutated DNA produced in the first round of mutagenesis as the template Thus, this template already contams one or more mutations The oligonucleotide encoding the additional desired ammo acid substιtutιon(s) is then annealed to this template, and the resulting strand of DNA now encodes mutations from both the first and second rounds of mutagenesis This resultant DNA can be used as a template m a third round of mutagenesis, and so on PCR mutagenesis is also suitable for making ammo acid variants While the following discussion refers to DNA. it is understood that the technique also finds application with RNA The PCR technique generally refers to the following procedure (see Er ch. supra, the chapter by R Higuchi. p 61 -70) When small amounts of template DNA are used as starting matenal m a PCR. primers that differ slightly in sequence from the conespondmg region in a template DNA can be used to generate relatively large quantities of a specific DNA fragment that differs from the template sequence only at the positions where the pnmers differ from the template For introduction of a mutation into a plasmid DNA. one ot the primers is designed to overlap the position of the mutation and to contain the mutation, the sequence of the other primer must be identical to a stretch of sequence of the opposite strand of the plasmid, but this sequence can be located anywhere along the plasmid DNA It is prefened. however, that the sequence of the second primer is located within 200 nucleotides from that of the first such that in the end the entire amplified region of DNA bounded by the pnmers can be easily sequenced PCR amplification using a pnmer pair like the one just descnbed results in a population of DNA fragments that differ at the position of the mutation specified by the pnmer, and possibly at other positions If the ratio of template to product matenal is extremely low, the vast majority of product DNA fragments incorporate the desired mutatιon(s) This product matenal is used to replace the conespondmg region in the plasmid that served as PCR template using standard DNA technology Mutations at separate positions can be introduced simultaneously by either using a mutant second pnmer. or performing a second PCR with different mutant pnmers and ligatmg the two resulting PCR fragments simultaneously to the vector fragment in a three (or more)-part hgation Another method for prepanng v anants. cassette mutagenesis. is based on the technique descnbed by Wells et al (Gene. 34 315. 1985) The starting matenal is the plasmid (or other vector) comprising DNA to be mutated The codon(s) m the DNA to be mutated are identified There must be a unique restriction endonuclease site on each side of the identified mutation sιte(s) If no such restnction sites exist, they may be generated using the above- descnbed oligonucleotide-mediated mutagenesis method to introduce them at appropnate locations in the DNA After the restnction sites have been introduced into the plasmid. the plasmid is cut at these sites to hneanze it A double- stranded oligonucleotide encoding the sequence of the DNA between the restnction sites, but contammg the desired mutatιon(s), is synthesized usmg standard procedures. The two strands are synthesized separately and then hybndized together using standard techniques This double-stranded oligonucleotide is referred to as the cassette This cassette is designed to have 3 ' and 5 ' ends that are compatible with the ends of the lmeanzed plasmid, such that it can be directly ligated to the plasmid Any such methods and techniques mav be employed to prepare or identify ErbB ligand variants useful m the present invention In particular, reference is made to WO 98/35036 which discloses various heregulm vanants which may be useful in the present invention 3.Insertion of DNA into a Cloning Vehicle The cDNA or genomic DNA encoding the native or variant polypeptide is inserted mto a rep cable vector for further cloning (amplification of the DNA) or for expression Many vectors are available, and selection of the appropnate vector will depend on 1 ) v\ hether it is to be used for DNA amplification or for DNA expression. 2) the size of the DNA to be inserted mto the v ector, and 3) the host cell to be transformed with the vector Each vector contains vanous components depending on its function (amplification of DNA or expression of DNA) and the host cell for which it is compatible The vector components generally include, but are not limited to, one or more of the following a signal sequence, an origin ot replication, one or more marker genes, an enhancer element, a promoter, and a transcnption termination sequence (i) Signal Sequence Component In general, the signal sequence may be a component of the vector, or it may be a part of the DNA that is inserted into the vector The native DNA is believed to encode a signal sequence at the amino terminus (5 ' end of the DNA encoding the polypeptide) of the polypeptide that is cleaved during post-translational processing of the polypeptide For instance, native ErbB ligand mav be secreted from the cell, but remains lodged in the membrane because it contains a transmembrane domain and a cytoplasmic region m the carboxyl terminal region of the polypeptide Thus, in a secreted, soluble version of ErbB ligand the carboxyl terminal domain of the molecule, including the transmembrane domam. is ordmanly deleted This truncated variant ErbB ligand may be secreted from the cell, provided that the DNA encoding the truncated vanant encodes a signal sequence recognized by the host The selected polypeptide may be expressed not only directly, but also as a fusion with a heterologous polypeptide. preferably a signal sequence or other polypeptide having a specific cleavage site at the N-and/or C- terminus of the mature polypeptide In general, the signal sequence may be a component of the vector, or it may be a part of the DNA that is inserted into the vector Included within the scope of this invention are ErbB ligands with the native signal sequence deleted and replaced with a heterologous signal sequence The heterologous signal sequence selected should be one that is recognized and processed, l e . cleaved by a signal peptidase. by the host cell For prokaryotic host cells that do not recognize and process the native ErbB ligand signal sequence, the signal sequence is substituted by a prokaryotic signal sequence selected, for example, from the group of the alkaline phosphatase penicillinase.1pp. or heat-stable enterotoxm II leaders For yeast secretion, the native ErbB ligand signal sequence mav be substituted by the yeast mvertase, alpha factor, or acid phosphatase leaders In mammalian cell expression, the native signal sequence is satisfactory, although other mammalian signal sequences may be suitable (ii) Origin of Replication Component Both expression and cloning vectors generally contain a nucleic acid sequence that enables the vector to replicate in one or more selected host cells Generally, in cloning vectors, this sequence is one that enables the vector to replicate independently of the host chromosomal DNA. and includes origins of replication or autonomously replicatmg sequences Such sequences are well known for a vanety of bactena, yeast, and viruses The ongm of replication from the plasmid pBR322 is suitable for most Gram-negative bactena, the 2m plasmid ongm is suitable for yeast, and vanous viral origins (SV40. polyoma. adenovirus. VSV or BPV) are useful for clonmg vectors m mammalian cells Generally, the ongm of replication component is not needed for mammalian expression vectors (the SV40 ongm may typically be used only because it contains the early promoter) Most expression vectors are "shuttle" vectors, l e . they are capable of replication in at least one class of organisms, but can be transtected into another organism for expression For example, a vector is cloned m E coh and then the same vector is transtected into yeast or mammalian cells for expression DNA may also be amplified by insertion mto the host genome This is readily accomplished using Bacillus species as hosts, for example, by including in the vector a DNA sequence that is complementary to a sequence found in Bacillus genomic DNA Transfection of Bacillus with this vector results in homologous recombination with the genome and insertion of the DNA encoding the selected polypeptide DNA can be amplified by PCR and directly transfected mto the host cells ithout any replication component (iii) Selection Gene Component Expression and cloning vectors should contain a selection gene, also termed a selectable marker This gene encodes a protem necessary tor the survival or growth of transformed host cells grown in a selective culture medium Host cells not transformed with the vector containing the selection gene will not survive in the culture medium Typical selection genes encode proteins that (a) confer resistance to antibiotics or other toxins, e g . ampicil n, neomycin. methotrexate, or tetracychne. (b) complement auxotrophic deficiencies or (c) supply critical nutnents not available from complex media, e g . the gene encoding D-alamne racemase for Bacilli One example of a selection scheme utilizes a drug to arrest growth ol a host cell Those cells that are successfully transformed with a heterologous gene express a protem conferring drug resistance and thus survive the selection regimen Examples of such dominant selection use the drugs neomycm (Southern et al . J Molec Appl Genet 1 327. 1982). mycophenohc acid (Mulligan et al . Science 209 1422. 1980) orhygromycιn (Sugden etal.,-Vto/ Cell Biol 5 410-413. 1985) The three examples given above employ bactenal genes under eukaryotic control to convey resistance to the appropnate drug G418 or neomycm (geneticm). xgpt (mvcopheno c acid), or hygromycm. respectively Another example ot suitable selectable markers for mammalian cells are those that enable the identification of cells competent to take up the nucleic acid such as dihydrofolate reductase (DHFR) or thymidine kmase The mammalian cell transformants are placed under selection pressure which only the transformants are uniquely adapted to survive by virtue of having taken up the marker Selection pressure is imposed by culturmg the transformants under conditions in which the concentration of selection agent in the medium is successively changed thereby leading to amplification of both the selection gene and the DNA that encodes the selected polypeptide Amplification is the process by which genes in greater demand for the production of a protem cntical for growth are reiterated m tandem within the chromosomes of successive generations of recombmant cells For example cells transformed with the DHFR selection gene are first identified by cultunng all of the transformants m a culture medium that contains methotrexate (Mtx) a competitive antagonist of DHFR An appropnate host cell when wild-type DHFR is employed, is the Chinese hamster ovary (CHO) cell line deficient m DHFR activity, prepared and propagated as descnbed by Urlaub and Chasm, Proc Natl Acad Sci USA 11 4216, 1980 The transformed cells are then exposed to increased levels of methotrexate This leads to the synthesis of multiple copies of the DHFR gene, and, concomitantly, multiple copies of other DNA compnsing the expression vectors, such as the DNA encoding ErbB ligand This amplification technique can be used with any otherwise suitable host, e g , ATCC No CCL61 CHO-K1, notwithstanding the presence of endogenous DHFR if . for example, a mutant DHFR gene that is highly resistant to Mtx is employed (EP 117,060) Alternatively, host cells (particularly wild-type hosts that contain endogenous DHFR) transformed or co-transformed with DNA sequences encoding the selected polypeptide, wild-type DHFR protein, and another selectable marker such as ammoglycoside 3' phosphotransferase (APH) can be selected by cell growth in medium containing a selection agent for the selectable marker such as an aminoglycostdic antibiotic, e g . kanamycin, neomycm. or G418 (see U S Patent No 4.965,199) A suitable selection gene for use m veast is the trpl gene present in the yeast plasmid Yrp7 (Stmchcomb et al , Natw e 282 39 1979. Kingsman et al Gene 1 141. 1979. or Tschemper et al , Gene 10 157. 1980) The trpl gene provides a selection marker for a mutant strain of yeast lacking the ability to grow in tryptophan. for example. ATCC No 44076 or PEP4-1 (Jones. Genetics 85 12. 1977) The presence of the tipl lesion in the yeast host cell genome then provides an effective environment for detecting transformation by growth in the absence of tryptophan Similarly. --ez.2-deficιent yeast strains (ATCC 20,622 or 38.626) are complemented by known plasmids beanng the Leu2 gene (iv) Promoter Component Expression and clonmg vectors usually contain a promoter that is recognized by the host organism and is operably linked to the nucleic acid encoding the polypeptide Promoters are untranslated sequences located upstream (5') to the start codon of a structural gene (generally withm about 100 to 1000 bp) that control the transcnption and translation of a particular nucleic acid sequence, such as ErbB ligand to which they are operably linked Such promoters typically fall into two classes mducible and constitutive Inducible promoters are promoters that initiate increased levels ot transcnption from DNA under their control m response to some change in culture conditions, e g . the presence or absence of a nutrient or a change in temperature At this time a large number of promoters recognized by a variety of potential host cells are well known These promoters are operably linked to DNA encoding ErbB ligand by removing the promoter from the source DNA by restnction enzvme digestion and inserting the isolated promoter sequence mto the vector Both the native ErbB ligand promoter sequence and many heterologous promoters may be used to direct amplification and- or expression ot ErbB ligand DNA However, heterologous promoters are preferred, as they generally permit greater transcnption and higher yields of expressed ErbB ligand as compared to the native ErbB ligand promoter Promoters suitable lor use with prokaryotic hosts include the β-lactamase and lactose promoter systems (Chang e. α/ Natut e 2 7 5 615. 1978. and Goeddel et al I\atuι e 28 l 544.1979). alkaline phosphatase. a tryptophan (tip) promoter system (Goeddel. \ucleιc Acids Res 8 4057. 1980 and EP 36 776). tPA (U S 5,641.655) and hybnd promoters such as the tac promoter (deBoer et al Proc Natl Acad Sci USA 80 21-25, 1983) However, other known bactenal promoters are suitable Their nucleotide sequences have been published, thereby enabling a skilled worker operably to ligate them to DNA encoding the selected polypeptide (Sieben st et al , Cell 20 269, 1980) usmg linkers or adapters to supply any required restriction sites Promoters for use m bacterial systems also generally will contain a Shme-Dalgarao (S D ) sequence operably linked to the encodmg DNA Suitable promoting sequences for use with yeast hosts include the promoters for 3-phosphoglycerate kmase (Hitzeman e. al , J Biol Chem , 255 2073. 1980) or other glycolytic enzymes (Hess e. α/ , J Adv EnzvmeRegl 149, 1968. and Holland, Biochemisti 17 4900. 1978), such as enolase glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase. phosphofructokmase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase. tnosephosphate isomerase, phosphoglucose isomerase. and glucokinase Other yeast promoters, which are inducible promoters having the additional advantage of transcnption controlled by growth conditions, are the promoter regions for alcohol dehydrogenase 2, lsocytochrome C, acid phosphatase. degradative enzymes associated with nitrogen metabolism, metallothionein, glyceraldehyde-3-phosphate dehydrogenase, and enzymes responsible for maltose and galactose utilization Suitable vectors and promoters for use in yeast expression are further descnbed in Hitzeman et al , EP 73.657A Yeast enhancers also are advantageously used with yeast promoters Promoter sequences are known for eukaryotes Virtually all eukaryotic genes have an AT-nch region located approximately 25 to 30 bases upstream from the site where transcnption is initiated Another sequence found 70 to 80 bases upstream from the start of transcnption of many genes is a CXCAAT region where X may be any nucleotide At the 3' end of most eukaryotic genes is an AATAAA sequence that may be the signal for addition of the poly A tail to the 3' end of the coding sequence All of these sequences are suitably inserted into mammalian expression vectors Gene transcnption from vectors m mammalian host cells may be controlled by promoters obtained from the genomes of viruses such as polyoma virus, fowlpox virus (UK 2,21 1.504, published 5 July 1989). adenovirus (such as Adenovirus 2). bovme papilloma virus, avian sarcoma virus, cytomegalovirus. a retrovirus. hepatttis-B virus and most preferably Simian Virus 40 (SV40). from heterologous mammalian promoters, e g , the actm promoter or an lmmunoglobulm promoter, from heat-shock promoters, and from the promoter normally associated with ErbB ligand sequence, provided such promoters are compatible with the host cell systems The early and late promoters of the S V40 virus are conveniently obtained as an SV40 restnction fragment that also contains the SV40 viral origin of replication (Fiers et al . Nature. 273 1 13 ( 1978), Mulligan and Berg, Science, 209 14221427 ( 1980). Pavlakis et al . Proc Natl Acad Sci USA. 78 73 98-7402 ( 1981 ) The immediate early promoter of the human cytomegalovirus is conveniently obtained as a Hindlll restnction fragment (Greenaway et al . Gene. 18 355-360 ( 1982)) A system for expressing DNA in mammalian hosts using the bovine papilloma virus as a vector is disclosed in U S Patent No 4.419.446 A modification of this system is described in U S Patent No 4.601.978 See also Gray et al Natui e 295 503-508 ( 1982) on expressing cDNA encoding immune mterferon in monkey cells. Reyes et al . Nature. 29 7 598-601 ( 1982) on expression ot human β-mterferon cDNA in mouse cells under the control of a thymidme kinase promoter from herpes simplex virus. Canaani and Berg. Proc Natl Acad Sci USA. 79 5166-5170 ( 1982) on expression of the human mterferon gene in cultured mouse and rabbit cells, and Gorman et al . Proc Natl Acad Sci USA 79 6777-6781 (1982) on expression of bactenal CAT sequences m CV-1 monkey kidney cells, chicken embryo fibroblasts. Chinese hamster ovarv cells. HeLa cells, and mouse NIH-3T3 cells using the Rous sarcoma virus long terminal repeat as a promoter (v) Enhancer Element Component Transcription of a DNA encoding a selected polypeptide of this invention by higher eukarvotes is often increased by inserting an enhancer sequence into the vector Enhancers are cis-acting elements of DNA. usually about from 10-300 bp. that act on a promoter to increase its transcnption Enhancers are relatively onentation and position independent having been found 5' (Laimms. et al . Proc Natl Acad Sci USA. 78 993. 1981) and 3' (Lusky et al , Mol Cell Bio . 3 1 108. 1983) to the transcription unit, within an intron (Baneηi et al . Cell. 33 729. 1983) as well as withm the coding sequence itself (Osborne et al Mol Cell Bio . 4 1293. 1984) Many enhancer sequences are now known from mammalian genes (globm. elastase. albumin, α-feto protem and msulm) Typically, however, one will use an enhancer from a eukaryotic cell virus Examples include the SV40 enhancer on the late side of the replication ongm (bp 100-270). the cytomegalov irus early promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers (see also Yaniv, Nature, 297 17-18 (1982)) on enhancing elements for activation of eukaryotic promoters The enhancer may be spliced into the vector at a position 5' or 3' to ErbB ligand DNA. but is preferably located at a site 5' from the promoter (vi) Transcription Termination Component Expression vectors used in eukaryotic host cells (yeast, fiingi, insect, plant, animal, human, or nucleated cells from other multicellular organisms) will also contain sequences necessary for the termination of transcnption and for stabilizing the mRNA Such sequences are commonly available from the 5 ' and, occasionally 3 ' untranslated regions of eukaryotic or viral DNAs or cDNAs These regions contain nucleotide segments transcnbed as polyadenylated fragments m the untranslated portion of the mRNA encoding the polypeptide The 3' untranslated regions also include transcnption termination sites Construction of suitable vectors containing one or more of the above listed components and the desired coding and control sequences employs standard gation techniques Isolated plasmids or DNA fragments are cleaved, tailored, and relegated m the form desired to generate the plasmids required For analysis to confirm correct sequences m plasmids constructed, the hgation mixtures are used to transform E coh K12 stram 294 (ATCC 31.446) and successful transformants selected by ampicillin or tetracyclme resistance where appropnate Plasmids from the transformants are prepared, analyzed bv restriction endonuclease digestion, and or sequenced by the method of Messing et al Nucleic Acids Res 9 309 ( 1981 ) or bv the method of Maxam et al , Methods in Enzvmologv 65 499 (1980) Particularly useful in the practice of this invention are expression vectors that provide for the transient expression in mammalian cells In general, transient expression involves the use of an expression vector that is able to replicate efficiently m a host cell, such that the host cell accumulates many copies of the expression vector and, m turn, synthesizes high levels of a desired polypeptide encoded by the expression vector Transient expression systems, compnsmg a suitable expression vector and a host cell, allow for the convenient positive identification of polypeptides encoded by cloned DNAs. as well as for the rapid screening ot such polypeptides lor desired biological or physiological properties Thus, transient expression systems are particularly useful in the invention for purposes of identifying useful analogs and variants Such a transient expression system is described in U S 5.024.939 Other methods, vectors, and host cells suitable tor adaptation to the synthesis of the selected polypeptide m recombinant v ertebrate cell culture are described m Gethmg et al Natui e 293 620-625 , 1981 , Mantei et al , Nature 281 40-46. 1979. Levmson et al , EP 1 17.060 and EP 1 17 058 4. Selection and Transformation of Host Cells Suitable host cells for clonmg or expressing the v ectors herein are the prokaryote. yeast, or higher eukaryote cells descnbed above Suitable prokaryotes include eubacteπa. such as Gram-negative or Gram-positive organisms, for example. E coh Bacilli such as B subtihs Pseudomonas species such as P aerugmosa. Salmonella typhimunum, or Serratia marcescans One preferred E coh cloning host is E coh 294 (ATCC 31 446), although other strains such as E coh X1776 (ATCC 31,537), and E coh W3110 (ATCC 27 325) are suitable These examples are illustrative rather than limiting Preferably the host cell should secrete minimal amounts of proteolytic enzymes Alternatively, in vin o methods of cloning, e g , PCR or other nucleic acid polymerase reactions, are suitable In addition to prokaryotes. eukaryotic microbes such as filamentous fungi or yeast are suitable hosts Sacchai omxces ceievisiae. or common baker's yeast, is the most commonly used among lower eukaryotic host microorganisms However, a number of other genera, species, and strains are commonly available and useful herem, such as Schizosaccharomvces pombe (Beach and Nurse. Nature.290 140 ( 1981), EP 139,383. pub shedMay 2, 1985), Kluyveromyces hosts (U S Patent 4.943.529) such as. e g K lactis (Louvencourt et al , J Bactenol , 737 (1983), K fragihs, K bulgancus, K thermotolerans. and K marxianus, yarrowia (EP 402.226), Pichia pastons (EP 183.070), Sreeknshna et al .LT Basic Microbiol , 28 265-278 (1988), Candida, Tiichoderm reesia fEP 244,234), euτospora crassa (Case et al , Proc Natl Acad Sci USA.76 5259-5263 (1979), and filamentous fungi such as, e g, Neurospora, Penicil um, Tolypocladium (WO 91/00357, published 10 January 1991), and Aspergillus hosts such as A nidulans (Ballance et al . Biochem -5ιophys Res Commun , 112 284-289 (1983), Tilburn et al . Gene, 26 205-221 (1983), Yelton etal . Proc Natl Acad Sci USA, 81 1470- 1474 (1984) and A Niger (Kelly and Hynes. -5M-50 , 4 475-479 (1985)) Suitable host cells for the expression of glycosylated polypeptide are denved from multicellular organisms Such host cells are capable of complex processing and glycosylation activities In principle, any higher eukaryotic cell culture is workable, whether from vertebrate or invertebrate culture Examples of invertebrate cells include plant and insect cells Numerous baculoviral strains and vanants and corresponding permissive insect host cells from hosts such as Spodopterα frugiperdα (caterpillar) Aedes αegypti (mosquito) Aedes αlbopictus (mosquito). Drosophilα melαnogαstei (fruitfly), and Bombvx mon host cells have been identified (see. e g . Luckow et αl Bio/Technology, 6 47-55 (1988). Miller et αl in Genetic Engineering, Set low. J K e t αl , eds . Vol 8 (Plenum Publishing, 1986), pp 277-279. and Maeda e. α/ Nature 575 592-594 (1985)) A vanety of such viral strains are publicly available, e g , the L- 1 variant oiAutogi apha cahformca NPV and the Bm-5 strain of Bombvx mon NPV. and such viruses may be used as the virus herein according to the present invention, particularly for transfection of Spodoptei a frugtperda cells Plant cell cultures of cotton, corn, potato, soybean, petunia, tomato, and tobacco can be utilized as hosts Typically, plant cells are transfected by mcubation with certain strains of the bacterium Agt obacterium tumefaciens Dunng incubation of the plant cell culture with A tumefaciens, the DNA encoding ErbB ligand is transferred to the plant cell host such that it is transfected. and will, under appropnate conditions, express ErbB ligand DNA In addition, regulatory and signal sequences compatible with plant cells are available, such as the nopaline synthase promoter and polyadenylation signal sequences (Depicker et al , Mol Appl Gen 1 561 (1982)) In addition, DNA segments isolated from the upstream region of the T-DNA 780 gene are capable of activating or increasing transcnption levels of plant-expressible genes in recombinant DNA-contammg plant tissue (see EP 321 196, published 21 June 1989) However, interest has been greatest in vertebrate cells, and propagation of vertebrate cells m culture (tissue culture) has become a routine procedure in recent years (Tissue Culture, Academic Press. Kruse and Patterson, editors (1973)) Examples of useful mammalian host cell lines are monkey kidney CV1 line transformed by SV40 (COS-7, ATCC CRL 1651 ), human embrvomc kidney lme (293 or 293 cells subcloned for growth in suspension culture. Graham et al , J Gen Vi rol 36 59. 1977). babv hamster kidney cells (BHK. ATCC CCL 10). Chinese hamster ovary cellsADHFR (CHO. Urlaub and Chasm. Proc Natl Acad Sci USA 11 4216 (1980)). mouse sertoli cells (TM4, Mather. Biol Reprod 23 243-251 (1980)). monkey kidney cells (CV1 ATCC CCL 70). African green monkey kidney cells (VERO-76 ATCC CRL-1587) human cervical carcinoma cells (HELA. ATCC CCL 2). canme kidney cells (MDCK. ATCC CCL 34). buffalo rat liver cells (BRL 3 A. ATCC CRL 1442), human lung cells (W138. ATCC CCL 75). human liver cells (Hep G2. HB 8065). mouse mammary tumor (MMT 060562. ATCC CCL51), TRI cells (Mather et al , Annals N Y Acad Sci , 383 44-68 (1982)), MRC 5 cells, FS4 cells; and a human hepatoma cell lme (Hep G2) Preferred host cells are human embryonic kidney 293 and Chmese hamster ovary cells Host cells are transfected and preferably transformed with the above-descnbed expression or cloning vectors of this invention and cultured in conventional nutnent media modified as appropnate for inducing promoters, selecting transformants. or amplifying the genes encoding the desired sequences Transfection refers to the taking up of an expression vector by a host cell whether or not any codmg sequences are in fact expressed Numerous methods of transfection are known to the ordmanly skilled artisan, for example. CaP0 4 and electroporation Successful transfection is generally recognized when any indication of the operation of this vector occurs within the host cell Transformation means introducing DNA into an organism so that the DNA is replicable, either as an extrachromosomal element or by chromosomal mtegration Dependmg on the host cell used, transformation is done usmg standard techniques appropnate to such cells The calcium treatment employing calcium chlonde, as descnbed m section 1 82 of Sambrook et al , supra, is generally used for prokaryotes or other cells that contain substantial cell-wall barriers Infection with Agrobactenum tumefaciens is used for transformation of certain plant cells, as descnbed by Shaw et al , Gene, 23 315 (1983) and WO 89/05859, published 29 June 1989 For mammalian cells without such cell walls, the calcium phosphate precipitation method descnbed m sections 16 30-16 37 of Sambrook et al, supra, is preferred General aspects of mammalian cell host system transformations have been descnbed by Axel in U S 4.399.216. issued 16 August 1983 Transformations into yeast are typically carried out according to the method of Van Solmgen et al , J Bact , 130 946 (1977) and Hsiao et al , Proc Natl Acad Sci (USA), 76 3829 (1979) However, other methods for introducing DNA into cells such as by nuclear injection, electroporation, or protoplast fusion may also be used 5. Culturing the Host Cells Prokaryotic cells used to produce the ErbB ligand are cultured in suitable media as descnbed generally m Sambrook et al supra The mammalian host cells used to produce the ErbB ligand may be cultured in a vanety of media Commercially available media such as Ham s F10 (Sigma). Minimal Essential 30 Medium ((MEM). Sigma), RPMI- 1640 (Sigma), and Dulbecco's Modified Eagle's Medium ((DMEM), Sigma) are suitable for cultunng the host cells In addition, any of the media described m Ham and Wallace, Meth Enz 58 44 ( 1979). Barnes and Sato, Anal Biochem , 102 255 (1980), U S 4.767,704, 4.657.866, 4,927.762. or 4.560.655. WO 90/03430. WO 87/00195; U S Patent No Re 30,985. U S 5.122 469. may be used as culture media for the host cells Any of these media may be supplemented as necessary with hormones and/or other growth factors (such as msulm, transfernn. or epidermal growth factor), salts (such as sodium chloride, calcium, magnesium, and phosphate), buffers (such as HEPES), nucleosides (such as adenosme and thvmidine). antibiotics (such as GENTAMYCI drug), trace elements (defined as inorganic compounds usually present at final concentrations in the micromolar range), and glucose or an equivalent energy source Any other necessary supplements may also be included at appropnate concentrations that would be known to those skilled in the art The culture conditions, such as temperature. pH. and the like, are those previously used with the host cell selected tor expression, and will be apparent to the ordinarily skilled artisan The host cells referred to in this disclosure encompass cells in in x in o culture as well as cells that are within a host animal It is further envisioned that the ErbB ligand may be produced by homologous recombmation, or with recombmant production methods utilizing control elements introduced into cells already contammg DNA encodmg the polypeptide currently m use in the field For example, a powerful promoter/enhancer element, a suppresser, or an exogenous transcnption modulatory element is inserted in the genome of the intended host cell in proximity and onentation sufficient to influence the transcription of DNA encoding the desired polypeptide 6. Detecting Gene Amplif-cation/ Expression Gene amplification and/or expression may be measured in a sample directly, for example, by conventional Southern blotting. Northern blotting to quantitate the transcription of mRNA (Thomas. Proc Natl Acad Sci USA, 11 5201-5205 (1980)), dot blotting (DNA analysis), or in situ hybndization. usmg an appropriately labeled probe based on the sequences provided herein Vanous labels may be employed, most commonly radioisotopes. particularly 32 P However, other techniques may also be employed, such as usmg biotin-modified nucleotides for introduction into a polynucleotide The biotin then serves as the site for binding to avidm or antibodies which may be labeled with a wide vanety of labels, such as radionuc des, fluorescers, enzymes, or the like Alternatively, antibodies may be employed that can recognize specific duplexes, including DNA duplexes, RNA duplexes, and DNA-RNA hybnd duplexes or DNA-protem duplexes The antibodies in turn may be labeled and the assay may be earned out where the duplex is bound to a surface, so that upon the formation of duplex on the surface, the presence of antibody bound to the duplex can be detected Gene expression, alternatively, may be measured by lmmunological methods, such as lmmunohistochemical staining of tissue sections and assay of cell culture or body fluids, to quantitate directly the expression of gene product With lmmunohistochemical staining techniques, a cell sample is prepared, typically dehydration and fixation, followed by reaction with labeled antibodies specific for the gene product coupled where the labels are usually visually detectable such as enzymatic labels, fluorescent labels, luminescent labels, and the like A particularly sensitive staining technique suitable for use m the present invention is descnbed by Hsu et al . Am J Chn Path , 75 734-738 (1980) Antibodies useful for lmmunohistochemical staining and/or assay of sample fluids may be either monoclonal or polvclonal, and may be prepared in any mammal Conveniently, the antibodies may be prepared agamst a native ErbB ligand or against a synthetic peptide based on the DNA sequences provided herein as descnbed further below 7. Purification of the Polypeptides The ErbB ligand may be recovered from a cellular membrane fraction Alternatively, a proteolytically cleaved or a truncated expressed soluble fragment or subdomain are recovered from the culture medium as a soluble polypeptide The polypeptide can be recovered from host cell lysates when directly expressed without a secretory signal When ErbB ligand is expressed in a recombinant cell other than one of human ongm. ErbB ligand is completely free of proteins or polypeptides of human ongin However, it is desirable to punfy ErbB ligand from recombinant cell proteins or polypeptides to obtain preparations that are substantially homogeneous as to ErbB ligand As a first step, the culture medium or lvsate is centnfuged to remove particulate cell debns The membrane and soluble protem fractions are then separated ErbB ligand can then be punfied from both the soluble protem fraction (requrnng the presence of a protease) and from the membrane fraction of the culmre lysate. depending on whether ErbB ligand is membrane bound The following procedures are exemplary of suitable punfication procedures fractionation on lmmunoaffinity or ion-exchange columns, ethanol precipitation, reverse phase HPLC. chromatography on silica, hepann SEPHAROSE or on a cation exchange resm such as DEAE. chromatofocusmg, SDS-PAGE. ammonium sulfate precipitation, and gel filtration using, for example, SEPHADEX G-75 Polypeptide vanants in which residues have been deleted, inserted or substituted are recovered m the same fashion as the native polypeptide. taking account of any substantial changes in properties occasioned by the vanation For example, preparation of an ErbB ligand fusion with another protem or polypeptide. e g . a bactenal or viral antigen, facilitates punfication, an lmmunoaffinity column contammg antibody to the antigen can be used to adsorb the fusion lmmunoaffinity columns such as a rabbit polvclonal anti-ErbB ligand column can be employed to absorb ErbB ligand variant by binding it to at least one remaining immune epitope A protease inhibitor such as phenylmethylsulfonylfluonde (PMSF) also may be useful to inhibit proteolvtic degradation dunng punfication, and antibiotics may be included to prevent the growth of adventitious contaminants One skilled in the art will appreciate that punfication methods suitable for native polypeptide may require modification to account for changes m the character of vanants or upon expression in recombmant cell culture 8.Covalent Modifications of the Polypeptides Covalent modifications of the ErbB ligands are mcluded within the scope of this invention Both native sequence and ammo acid sequence vanants optionally are covalently modified One type of covalent modification included within the scope of this invention is an ErbB ligand fragment. ErbB ligand fragments, such as those having up to about 40 amino acid residues are convemently prepared by chemical synthesis, or by enzymatic or chemical cleavage of the full-length ErbB ligand polypeptide or ErbB ligand vanant polypeptide Other types of covalent modifications of ErbB ligands are introduced into the molecule by reacting targeted ammo acid residues of ErbB ligands with an organic denvatizing agent that is capable of reacting with selected side chains or the N- or C-terminal residues Cystemyl residues most commonly are reacted with α-haloacetates (and corcesponding amines) such as chloroacetic acid or chloroacetamide, to give carboxymethyl or carboxyamidomethvl derivatives Cystemyl residues also are deπvatized by reaction with bromotnfluoroacetone. "α-bromo-β-(5-ιmιdozoyl) propiomc acid, chloroacetyl phosphate. N-alkylmaleimides. 3-nιtro-2-pyπdyl disulfide. methyl 2-pyπdyl disulfide. p-chloromercunbenzoate. 2- chloromercuπ-4- mtrophenol. or chloro-7-mtrobenzo-2-oxa- 1.3-dιazole Histidyl residues are deπvatized by reaction with diethylpyrocarbonate at pH 5 5-7 0 because this agent is relatively specific for the histidyl side chain Para-bromophenacyl bromide also is useful, the reaction is preferably performed in O lM sodium cacodylate at pH 6 0 Lysmyl and ammo terminal residues are reacted with succimc or other carboxyhc acid anhydndes Deπvatization with these agents has the effect of reversing the charge of the lysmyl residues other suitable reagents for denvatizing an ammo-containing residues include limdoesters such as methyl picolimmidate, pyndoxal phosphate. pyndoxal; chloroborohydnde. tπmtrobenzenesulfonic acid. O-methyhsourea. 2.4-pentanedιone. and transaminase- catalyzed reaction with glyoxylate Arginyl residues are modified by reaction with one or several conventional reagents, among them phenylglyoxal. 2.3- butanedione, 1.2-cv clohexanedione. and ninhydnn Denvatization of arginme residues requires that the reaction be performed in alkaline conditions because of the high pK a of the guanidme functional group Furthermore, these reagents may react with the groups of lysine as well as the arginme epsilon-ammo group The specific modification of tyrosyl residues may be made, with particular interest in mtroducmg spectral labels mto tyrosyl residues by reaction with aromatic diazomum compounds or tetranitromethane Most commonly, N-acetvhmidizole and tetranitromethane are used to form O-acetvl tyrosyl species and 3-nιtro denvatives, respectively Tyrosyl residues are lodinated usmg I. or J I. to prepare labeled proteins for use m radioimmunoassay, the chloramme T method descnbed above being suitable Carboxyl side groups (aspartyl or glutamyl) are selectively modified by reaction with carbodiimides (R))- N=C=N-R))), where R and R)) are different alkyl groups, such as l-cyclohexyl-3-(2-morpholιnyl-4-ethyl) carbodnmide or 1 -efhyl-3-(4-azonιa-4.4-dιmethylpentyl) carbodnmide Furthermore, aspartyl and glutamyl residues are converted to asparagmyl and glutaminyl residues by reaction with ammonium ions Deπvatization with bifunctional agents is useful for cross-linking ErbB ligand to a water-insoluble support matnx or surface Commonly used cross-linking agents include, e g .l,l-bιs(dιazoacetyl)-2-phenylethane, glutaraldehyde. N-hydroxysuccinimide esters, for example, esters with 4-azιdosalιcylιc acid, homobifunctional lmidoesters. including disuccimmidyl esters such as 3 31- maleimides dιthιobιs(succιnιmιdylpropιonate), and bifunctional such as bis-N-maleimido- 1. 8 -octane Denvatizing agents such as methyl-3-((p- azιdophenyl)dιthιo)propιoιmιdate yield photoactivatable intermediates that are capable of forming cross-links m the presence of light Alternatively, reactive water-insoluble matrices such as cyanogen bromide-activated carbohydrates and the reactive substrates descnbed m U S 3.969,287. 3.691,016, 4,195.128, 4,247,642, 4,229.537. and 4.330,440 are employed for protein immobilization Glutaminyl and asparagmyl residues are frequently deamidated to the corresponding glutamyl and aspartyl residues, respectively Alternatively, these residues are deamidated under mildly acidic conditions Either form of these residues falls within the scope of this invention Other modifications include hydroxylation ofprolme and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the a-amino groups of lysine, arginme. and histidrne side chains (T E Creighton. Proteins Structure and Molecular Properties W H Freeman & Co . San Francisco, pp 79-86 (1983)), acetylation of the N-termmal amine. and amidation of any C-termmal carboxyl group ErbB ligand optionally is fused with a polypeptide heterologous to ErbB ligand The heterologous polypeptide optionally is an anchor sequence such as that found in a phage coat protem such as M 13 gene III or gene VIII proteins These heterologous polypeptides can be covalently coupled to ErbB ligand polypeptide through side chains or through the terminal residues ErbB ligand may also be covalently modified by altering its native glycosylation pattern One or more carbohydrate substitutents in these embodiments, are modified by adding, removing or varying the monosacchande components at a given site, or by modifying residues in ErbB ligand as that glycosylation sites are added or deleted Glycosylation of polypeptides is typically either N-linked or O-hnked N-hnked refers to the attachment of the carbohydrate moiety to the side chain of an asparagine residue The tn-peptide sequences asparagme-X-senne and asparagme-X-threonine. where X is any ammo acid except prolme. are the recognition sequences for enzymatic attachment of the carbohydrate moiety to the asparagine side chain Thus, the presence of either of these tn-peptide sequences in a polypeptide creates a potential glycosylation site O-lmked glycosylation refers to the attachment of one of the sugars N-acetylgalac tosamine. galactose. or xylose, to a hydroxyamino acid, most commonly seπne or threonme. although 5-hydroxyprolme or 5-hydroxylysme may also be used Glycosvlation sites are added to ErbB ligand by altenng its amino acid sequence to contain one or more of the above-descnbed tn- peptide sequences ( for N-linked glycosvlation sites) The alteration may also be made by the addition of, or substitution bv. one or more serme or threonine residues to ErbB ligand (for O-lmked glycosylation sites) For ease. ErbB ligand is preferably altered through changes at the DNA level, particularly by mutating the DNA encoding ErbB ligand at preselected bases such that codons are generated that will translate into the desired ammo acids Chemical or enzymatic coupling of glycosides to ErbB ligand increases the number of carbohydrate substituents These procedures are advantageous in that they do not require production of the polypeptide in a host cell that is capable ot N- and O-hnked glycosylation Dependmg on the coupling mode used, the sugar(s) may be attached to (a) arginme and histidme, (b) free carboxyl groups, (c) free sulfydryl groups such as those of cysteme, (d) free hydroxyl groups such as those of serme. threonine. or hvdroxyprolme, (e) aromatic residues such as those of phenylalamne. tyrosme. or tryptophan. or (f) the amide group of glutamine These methods are descnbed in WO 87/05330. published 1 1 September 1987. and in Aplin and Wnston (CRC Cut Rev Biochem , pp 259-306 (1981)) Carbohydrate moieties present on an ErbB ligand also are removed chemically or enzymatically Chemical deglycosylation requires exposure of the polypeptide to the compound tnfluoromethanesulfonic acid, or an equivalent compound This treatment results in the cleavage of most or all sugars except the linking sugar (N-acetylglucosamine or N-acetylgalactosamine). while leaving the polypeptide mtact Chemical deglycosylation is descnbed by Hakimuddin et al (Atch Biochem Biophxs . 259 52 (1987)) and by Edge et al (Anal Biochem , 118 131 (1981)) Carbohydrate moieties are removed from ErbB ligand by a vanety of endo- and exo- glycosidases as descnbed by Thotakura et al ( Meth Enzvmol , 138 350 (1987)) Glycosylation also is suppressed by tumcamycin as descnbed by Duksm et al (J Biol Chem , 257:3105 (1982)) Tumcamycin blocks the formation of protein-N-glycoside linkages ErbB ligand may also be modified by linking ErbB ligand to vanous nonproteinaceous polymers, e.g., polyethylene glycol. polypropylene glycol or polyoxyalkylenes, m the manner set forth m U S.4,640,835.4.496,689, 4.301,144.4,670.417.4,791.192 or 4,179.337 One preferred way to increase the in vivo circulating half life of non- membrane bound ErbB ligand is to conjugate it to a polymer that confers extended half-life, such as polyethylene glycol (PEG) (Maxfield. et al, Polvmer 16.505-509 (1975), Bailey, F E . et al. m Nonionic Surfactants (Schick. M J . ed ) pp 794821 1967). (Abuchowski. A et al , J Biol Chem 252. 3582-3586. 1977, Abuchowski. A et al , Cancer Biochem Biophvs 7, 175-186. 1984). (Katre, N V et al , Proc Natl Acad Sci , 84. 1487-1491. 1987, Goodson, R et al Bio Technology, 8. 343-346. 1990) Conjugation to PEG also has been reported to have reduced lmmunogemcity and toxicity (Abuchowski. A et al , J Biol Chem , 252. 3578-3581 , 1977) ErbB ligand may also be entrapped in microcapsules prepared, for example, by interfacial polymenzation (for example, hydroxymethylcellulose or gelatin-microcapsules and poly-(methylmethacylate) microcapsules. respectively), in colloidal drug delivery systems (for example, posomes, albumin microspheres, microemulsions. nano-particles and nanocapsules). or in macroemulsions Such techniques are disclosed m Remington's Pharmaceutical Sciences, 16th edition. Oslo. A . Ed . (1980) B. Anti-ErbB Receptor Antibodv Preparation The antibodies contemplated for use m this invention include polyclonal antibodies, monoclonal antibodies and fragments thereof Preferably, the antibodies employed in the methods of the invention compnse ErbB receptor agonist antibodies which induce or stimulate proliferation of beta precursor cells or mature beta cells, or induce or stimulate differentiation of beta precursor cells Polvclonal antibodies are preterablv raised in animals by multiple subcutaneous (sc) or intrapentoneal ( ) injections of the relevant antigen (1 e . an ErbB receptor) and an adjuvant It may be useful to conjugate the relevant antigen to a protem that is lmmunogemc in the species to be immunized, e g , keyhole limpet hemocyamn, serum albumin, bovine thyroglobulin. or soybean trypsin inhibitor using a bifunctional or denvatizing agent, for example. maleimidobenzoyl sulfosuccmimide ester (conjugation through cysteme residues). N-hydroxysuccimmide (through lysine residues), glutaraldehyde. and succmic anhydride Animals may be immunized against the antigen, lmmunogemc conjugates, or derivatives by combining, e g , 100 g or 5 g of the protem or conjugate (for rabbits or mice, respectively) with 3 volumes of Freund's complete adjuvant and injecting the solution intradermally at multiple sites One month later the animals are boosted with 1/5 to 1/10 the ongmal amount of peptide or conjugate m Freund's complete adjuvant by subcutaneous injection at multiple sites Seven to 14 da later the animals are bled and the serum is assayed for antibody titer Animals are boosted until the titer plateaus Preferably, the animal is boosted with the conjugate of the same antigen, but conjugated to a different protein and'or through a different cross-linking reagent Conjugates also can be made in recombinant cell culture as protem fusions Also, aggregating agents such as alum are suitably used to enhance the immune response Monoclonal antibodies may be made usmg the hybndoma method first descnbed by Kohler et al , Nature. 256-495 (1975). or may be made by recombinant DNA methods (U S Patent No. 4,816.S67) In the hybndoma method, a mouse or other appropnate host animal, such as a hamster or macaque monkey, is immunized as herein above descnbed to elicit lymphocytes that produce or are capable of producing antibodies that will specifically bind to the protein used for immunization. Alternatively, lymphocytes may be immunized in vitro Lymphocytes then are fused with myeloma cells using a suitable fusing agent, such as polyethylene glycol, to form a hybndoma cell (Goding, Monoclonal Antibodies Principles and Practice, pp.59-103 (Academic Press, 1986)) The hybndoma cells thus prepared are seeded and grown m a suitable culture medium that preferably contains one or more substances that inhibit the growth or survival of the unfused. parental myeloma cells For example, if the parental myeloma cells lack the enzyme hypoxanthine guanine phosphoπbosyl transferase (HGPRT or HPRT). the culture medium for the hybndomas typically will include hypoxanthine. amtnoptenn. and thymidine (HAT medium), which substances prevent the growth of HGPRT-deficient cells Preferred myeloma cells are those that fuse efficiently, support stable high-level production of antibody by the selected antibody-producing cells, and are sensitive to a medium such as HAT medium Among these, preferred myeloma cell lines are muπne myeloma lines, such as those derived from MOP-21 and M C - 1 1 mouse tumors available from the Salk Institute Cell Distribution Center. San Diego. California USA. and SP-2 or X63- AgB-653 cells available from the American Type Culture Collection. Manassas. Virginia USA Human myeloma and mouse-human heteromyeloma cell lines also have been described for the production of human monoclonal antibodies (Kozbor. J Immunol . 133 3001 (1984). Brodeur etal .Monoclonal Antibodx Production Techniques and Applications, pp 51-63 (Marcel Dekker. Inc . New York. 1987)) Culture medium m which hybndoma cells are growing is assayed for production ot monoclonal antibodies directed against the antigen Preferably, the binding specificity of monoclonal antibodies produced by hybndoma cells is determined by immunoprecipitation or by an in vitro binding assay, such as radioimmunoassay (RIA) or enzyme- linked immunoabsorbent assay (ELISA) The binding affinity of the monoclonal antibody can. for example, be determined bv the Scatchard analysis of Munson et al . Anal Biochem , 107 220 ( 1980) After hybndoma ceils are identified that produce antibodies of the desired specificity, affinity, and/or activity, the clones may be subcloned by limiting dilution procedures and grown by standard methods (Goding, Monoclonal Antibodies Principles and Pi actice. pp 59-103 (Academic Press. 1986)) Suitable culture media for this purpose include, tor example. D-MEM or RPMI-1640 medium In addition, the hybndoma cells may be grown in vivo as ascites tumors in an animal The monoclonal antibodies secreted by the subclones are suitably separated from the culmre medium, ascites fluid, or serum by conventional lmmunoglobulm purification procedures such as for example, protem A- SEPHAROSE. hydroxvlapatite chromatography gel electrophoresis. dialysis, or affinity chromatography DNA encoding the monoclonal antibodies is readily isolated and sequenced using conventional procedures (e g . by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains ot the monoclonal antibodies) The hybndoma cells serve as a preferred source ot such DNA Once isolated, the DNA may be placed mto expression vectors, which are then transfected mto host cells such as E coh cells, simian COS cells. Chinese hamster ovary (CHO) cells, or myeloma cells that do not otherwise produce lmmunoglobulm protein, to obtain the synthesis of monoclonal antibodies in the recombinant host cells Hybndoma cell lines producing antibodies may be identified by screening the culture supernatants for antibodv which binds to one or more ErbB receptors This is routinely accomplished by conventional immunoassays usmg soluble receptor preparations or by FACS using cell-bound receptor and labeled candidate antibody ErbB receptor agonist antibodies are preferably antibodies which activate ErbB receptor phosphorylation. which can be determined usmg known tyrosme phosphorylation assays in the art Certain agonist antibodies to one or more ErbB receptors have been previously described, for instance, by Yarden, Proc Natl Acad Sci 87 2569-2573 (1990) and Defize et al , EMBO -/ 5 1 187-1192 (1986) The hybnd cell lines can be maintained in culture in vitro in cell culture media The cell lines of this invention can be selected and/or mamtatned m a composition compnsmg the contmuous cell line in hypoxanthme- aminoptenn thymidine (HAT) medium In fact, once the hybndoma cell line is established, it can be maintained on a vanety of nutntionally adequate media Moreover, the hybrid cell lines can be stored and preserved in any number of conventional ways, including freezing and storage under liquid nitrogen Frozen cell lines can be revived and cultured indefinitely with resumed synthesis and secretion of monoclonal antibodv The secreted antibody is recovered from tissue culture supernatant by conventional methods such as precipitation, ion exchange chromatography, affinity chromatography. or the like The antibodies described herein are also recovered from hybndoma cell cultures by conventional methods for purification of IgG or IgM as the case may be that heretofore have been used to purify these immunoglobulms from pooled plasma, e g . efhanol or polyethylene glycol precipitation procedures Human antibodies may be used Such antibodies can be obtained by using human hybπdomas (Cole et al , Monoclonal Antibodies and Cancer Thei apx, Alan R Ltss, p 77 (1985)) Chimenc antibodies. Cabilly et al , U S 4.816.567. (Morrison e. α/ . /Vot Natl Acad Sci , 81 6851 (1984). Neuberger e. al Natw e 312 604 (1984), Takeda et al Nature 314 452 (1985)) containing a munne vanable region and a human constant region of appropnate biological activity (such as ability to activate human complement and mediate ADCC) are within the scope of this invention, as are humanized antibodies produced by conventional CDR-grafting methods (Riechmann et al , Nature 332 333-327(1988), EP 0328404 Al. EP 02394000 A2) Techniques for creating recombinant DNA versions of the antigen-bindmg regions of antibody molecules (Fab or vanable regions fragments) which bypass the generation of monoclonal antibodies are also encompassed within the practice of this invention One extracts antibody-specific messenger RNA molecules from immune system cells taken from an immunized sub)ect. transcnbes these into complementary DNA (cDNA). and clones the cDNA into a bactenal expression system and selects for the desired binding charactenstic The Scnpps/Stratagene method uses a bactenophage lambda vector system contammg a leader sequence that causes the expressed Fab protein to migrate to the penplasmic space (between the bactenal cell membrane and the cell wall) or to be secreted One can rapidly generate and screen great numbers of functional Fab fragments to identify those which bind the receptors with the desired characteristics Alternatively, the antibodies can be prepared by the phage display techniques descnbed in Hoogenboom. Tibtech February 1997 (vol 15). Nen et al , Cell Bwphxsics 27 47-61 (1995), Winter et al . Annu Rev Immunol , 12 433-55 ( 1994), and Soderlind et al , Immunol Rev 130 109-124 ( 1992) and the references descnbed therein as well as the monovalent phage display technique descnbed in Lowman et al , Biochem 30 10832- 10838 ( 1991 ) C. Therapeutic Compositions and Methods The ErbB receptor ligands or ErbB receptor agonist antibodies may be employed to induce or stimulate mature beta cell or precursor beta cell proliferation The ErbB receptor ligands or ErbB receptor agonist antibodies may also be employed to induce or stimulate beta precursor cell differentiation Use of ErbB ligands is, m particular, referred to m the methods below However, it is contemplated that the ErbB receptor agonist antibodies of the invention may be similarly employed The methods of the mvention include methods of treating pancreatic dysfunction m mammals A preferred method is a method of treating diabetes, and even more preferably. Type I diabetes It is contemplated that an ErbB receptor ligand may be administered as a single therapeutic agent in treating the mammal in need of such treatment Alternatively, an ErbB ligand may be administered in combmation with one or more other ErbB ligands For instance, the mammal may be admmistered a combination of both heregulin and betacellulm. It is further contemplated that the ErbB receptor ligands may be administered m combination with other therapies or agents useful for treating pancreatic dysfunction, or symptoms associated with such pancreatic dysfunction, such as msulm, sulphonylurea, cyclosponn or other known immunosuppressive agents, thiozo denediones, and metformin Compositions, such as pharmaceutically acceptable formulations, can be prepared for storage by mixing the ErbB receptor ligand having the desired degree of punty with optional earners, excipients, or stabilizers (Remmgton's Pharmaceutical Sciences, supra) Acceptable earners, excipients or stabilizers should be nontoxic to recipients at the dosages and concentrations employed, and mclude buffers such as phosphate, citrate, and other organic acids, antioxidants includmg ascorbic acid, low molecular weight (less than about 10 residues) polypeptides. proteins, such as serum albumin, gelatin, or immunoglobulms, hydrophihc polymers such as polyvmylpyrrolidone. ammo acids such as glycine, glutamine. asparagine, arginme or lysine, monosacchaπdes, disacchandes. and other carbohydrates includmg glucose, mannose. or dextnns. chelating agents such as EDTA. sugar alcohols such as manmtol or sorbitol, salt- forming countenons such as sodium, and or noniomc surfactants such as TWEEN. PLURONICS or polyethylene glycol (PEG) The ErbB receptor ligand to be used for in vivo administration should be stenle This is readily accomplished by filtration through sterile filtration membranes, prior to or following lyophilization and reconstitution The ligand optionally will be stored m lyophilized form or in solution Therapeutic compositions containing the ErbB receptor hgand(s) generally are placed into a container havmg a stenle access port, for example, an tntravenous solution bag or vial having a stopper pierceable by a hypodermic injection needle The route of administration will usually be in accord with known methods, e g , injection or infusion by intravenous, mtrapeπtoneal intracerebral. intramuscular, intraocular mtraarteπal. powder or liquid aerosol administration, or by sustained release systems as noted below The selected ErbB receptor ligand may be admmistered continuously by infusion or by bolus injection It is contemplated that the ErbB receptor ligand may be administered to the mammal via a cannula. such as by inserting a cannula device into the pancreas or pancreatic tissue The cannula device may also be employed to admmister the ErbB receptor ligand to the mammal via the ce ac artery The use ot a cannula device for delivery of therapeutic agent is known m the art and may be accomplished usmg techniques known to the skilled artisan Suitable examples ot sustamed-release preparations include semipermeable matnces of solid hydrophobic polymers containing the ErbB receptor ligand. which matnces are in the form of shaped articles, e g films, or microcapsules Examples ot sustamed-release matnces include polyesters, hydrogels (e.g . poly(2-hydroxyefhyl- methacrylate) as descnbed by Langer et al , J Biomed Mater Res , 15 167-277 (1981) and Langer. Chem Tech 12 98-105 (1982) or poly(vιnylalcohol)), polylactides (U S 3.773,919. EP 58.481). copolymers of L-glutamic acid and gamma ethyl-L-glutamate (Sidman et al , Biopolvmers, 22 547-556 (1983)), non-degradable ethylene-vinyl acetate (Langer et al , supi a), degradable lactic acid-glycohc acid copolymers such as the LUPRON DEPOT (injectable microspheres composed of lactic acid-glycohc acid copolymer and leuprohde acetate), and poly-D-(-)-3- hydroxybutyπc acid (EP 133.988) While polymers such as ethylene-vmyl acetate and lactic acid-glycohc acid enable release of molecules tor over 100 days, certain hydrogels release proteins for shorter time penods When encapsulated proteins remam in the body for a long time, they may denature or aggregate as a result of exposure to moisture at 37°C, resulting m a loss of biological activity and possible changes in lmmunogemcity Rational strategies can be devised for protem stabilization depending on the mechanism involved For example, if the aggregation mechanism is discovered to be lntermolecular S-S bond formation through thio-disulfide mterchange, stabilization may be achieved by modifying sulfhydryl residues, lyophihzing from acidic solutions, controlling moisture content, using appropnate additives, and developing specific polymer matrix compositions Sustamed-release compositions also mclude liposomally entrapped ErbB receptor ligand Liposomes contammg the selected ligand may be prepared by methods known per se DE 3.218,121 , Epstein et al . Proc Natl Acad Sci USA, 82 3688-3692 (1985), Hwang et al . Proc Natl Acad Sci USA, 11 4030-4034 (1980). EP 52,322, EP 36,676. EP 88.046. EP 143.949. EP 142.641. Japanese patent application 83-118008. U S 4.485.045 and 4,544.545. and EP 102.324 Ordmanly the liposomes are of the small (about 200-800 Angstroms) umlamelar type in which the hpid content is greater than about 30 mol % cholesterol, the selected proportion being adjusted for the optimal therapy Liposomes with enhanced circulation time are disclosed in U S patent no 5.013.556 An effective amount of ErbB ligand to be employed therapeutically will depend, for example, upon the therapeutic objectives, the route of administration, and the condition of the patient, for instance, the seventy of the pancreatic dysfunction It may be necessary for the therapist to titer the dosage and modify the route of administration as required to obtain the optimal therapeutic effect A typical daily dosage might range from about 1 μg/kg to about 1 mg/kg and up to 100 mg/kg or more, depending on the factors mentioned above Typically, the clinician will administer the selected polypeptιde(s) until a dosage is reached that achieves the desired effect Making the determinations of dosing and scheduling is within the routine skill of the art Effective doses may be extrapolated from dose-response curves denved from in vitro or animal model test systems The progress of this therapy is easily monitored by conventional assays, for example, by testing for c-peptide levels, glucose-tolerance testing, or blood analysis of glucose levels The invention also provides methods of ex vivo treatment of mammalian cells using ErbB ligand Such ex vivo treatment may be useful in treating, for instance, beta precursor cells in culture, and subsequently transplanting the treated cells mto a mammal in need of such treatment using appropnate transplantation techniques Optionally. the transplantation is an autologous transplantation wherein the mammal's own cells are removed, treated in culture with ErbB ligand. and then transplanted back to the same mammal In the methods, cells or tιssue(s) containing mature beta cells or beta precursor cells may be obtained from a mammal (such as by performing a surgical or biopsy procedure), and preferably are obtained aseptically The number of cells or amount of tissue needed for the in vitro culture can be determined empmcally The cells or tissues are then placed in a suitable cell or tissue culture dish or plate and exposed to one or more ErbB ligands Typically, the ErbB ligand will be added to the cell culture at a concentration of about 0 1 to about 100 nM, preferably about 1 to 50 nM If desired, the cells may be cultured for several generations m order to sufficiently expand the beta cell population Vanous cell culture mediums known in the art will be suitable for the in vitro culture, including Ham ' s F10. MEM. RPMI 1640. and DMEM Such media is available from Sigma (St Louis. MO) and GIBCO (Grand Island. NY) Typically, the culmre medium will contain components such as carbohydrates (like glucose), essential amino acids, vitamins, fatty acids, trace elements, and optionally, serum from a mammalian source The cell culture conditions should be suitable to effect proliferation and/or differentiation of the beta cells The treated cells or tιssue(s) can be formulated, if desired, in a earner such as those descnbed above The treated cells or tιssue(s) can then be infused or transplanted mto a recipient mammal using techniques known in the art The recipient mammal may be the same individual as the donor mammal, or may be another heterologous mammal An "effective amount" of the treated cells or tιssue(s) to be transplanted to the mammal will depend, for example, on the therapeutic objectives, the route of administration, and the condition of the patient It will be within the ordinary skill of the practitioner to determine dose of administration and modify means of administration to obtain the optimal therapeutic effect Smgle or multiple doses of the treated cells or tιssue(s) may be admmistered to the recipient mammal It may be desirable to determine approximate dose ranges in vitro or in animal models, from which dose ranges for human patients can be extrapolated In the methods where heterologous cells or tιssue(s) are transplanted into the recipient mammal, immunosuppressant agents known m the art, such as cyclosponn, will also typically be administered to the recipient mammal Subsequent to the transplantation of the treated cells into the mammal, it is contemplated that further or continued administration of one or more ErbB ligands to the mammal in vivo may be useful to further enhance, for example, sulm secretion by the beta cells Such further or continued administration of ErbB ligand may be accomplished using the compositions and methods descnbed above Any or all of the methods, compositions, and procedures descnbed herein with respect to the ErbB receptor ligands may alternatively, or in combmation, employ the ErbB receptor agonist antibodies descnbed in the present application Gene therapy methods are also provided by the invention Nucleic acid encoding the ErbB receptor ligands may be employed in gene therapy In gene therapy applications, genes are introduced into cells in order to achieve in vivo synthesis of a therapeutically effective genetic product, for example, replacement of a defective gene "Gene therapy "" includes both conventional gene therapy where a lasting effect is achieved by a single treatment, and the administration of gene therapeutic agents, which involves the one time or repeated administration of a therapeutically effective DNA or mRNA Antisense RNAs or DNAs can be used as therapeutic agents for blocking the expression of certain genes in vivo It has already been shown that short antisense oligonucleotides can be imported into cells where they act as inhibitors, despite their low intracellular concentrations caused by their restncted uptake by the cell membrane [Zamecmk et al . Proc Natl Acad Sci 83 4143-4146 (1986)] The oligonucleotides can be modified to enhance their uptake, e g , by substituting their negatively charged phosphodiester groups by uncharged groups There are a vanety of techniques available for introducing nucleic acids into viable cells The techniques vary dependmg upon whether the nucleic acid is transferred mto cultured cells in vitro, or in vivo in the cells of the mtended host Techniques suitable for the transfer ot nucleic acid into mammalian cells in vitro include the use of liposomes, electroporation, microinjection cell fusion. DEAE-dextran the calcium phosphate precipitation method, etc The currently preferred in vixo gene transfer technique mcludes transfection with viral (typically retroviral) vectors and viral coat protem- hposome mediated transfection [Dzau et al , Tt ends in Biotechnology 1 1 205-210 (1993)] In some situations it is desirable to provide the nucleic acid source with an agent that targets the target cells, such as an antibody specific for a cell surface membrane protein or the target cell, a ligand for a receptor on the target cell, etc Where liposomes are employed, protems which bind to a cell surface membrane protem associated with endocytosis may be used for targeting and/ or to facilitate uptake, e g . capsid proteins or fragments thereof tropic for a particular cell type, antibodies for proteins which undergo internalization m cycling, proteins that target intracellular localization and enhance intracellular half-life The technique of receptor-mediated endocytosis is descnbed for example, by Wu et al . J Biol Chem 262 4429-4432 (1987) and Wagner et al . Pioc Natl Acad Sci 87 3410-3414 (1990) For a review of gene marking and gene therapy protocols, see, e g , Anderson et al . Science 256 808-813 (1992) D. Kits and Articles of Manufacture In a further embodiment there are provided articles of manufacture and kits contammg ErbB ligand (or ErbB receptor agonist antibodies) which can be used m the applications descnbed above The article of manufacture compnses a container with a label Suitable containers mclude, for example, bottles, vials, and test tubes The contamers may be formed from a vanety of matenals such as glass or plastic The container holds a composition which mcludes ErbB ligand (or ErbB receptor agonist antibody) The label on the container indicates that the composition is used for a specific therapy or diagnostic application, and may mdicate directions for use for either in vivo or ex vivo treatment, such as those descnbed above The kit will typically compnse the container descnbed above and one or more other containers compnsmg matenals desirable from a commercial and user standpoint, including buffers, diluents, filters, needles, syringes, and package inserts with instructions for use All patent and literature references cited m this specification are expressly incorporated by reference The following examples are offered by way of illustration and not by way of limitation EXAMPLES EXAMPLE 1 Pnmary cultures of muπne fetal pancreatic cells were assayed with various ErbB ligands and the expression of vanous markers or msulm was examined Pancreata were dissected from el 4 embryos of CD 1 mice (Charles River Laboratones) The pancreata were then digested with 1 37 mg/ml collogenase/dispase (Boehringer Mannheim) in F12/DMEM (Gibco) at 37°C for 40 to 60 minutes Following the incubation, the digestion was neutralized with an equal volume of 5% BSA, and then the cells were washed once with RPMI 1640 (Gibco) On Day 1, the cells were seeded into 12-well tissue culture plates that had been precoated with 20 microgram/ml laminin (Boehringer Mannheim) in PBS Cells from the pancreata of 1 -2 embryos were distnbuted per each well in pnmary culture medium (RPMI 1640 containing 10 microgram ml rhlnsuhn (Genentech, Inc.), 50 microgram/ml aprotimn (Boehnnger Mannheim), 60 microgram ml bovine pituitary extract (BPE) (Pel-Freeze), 100 ng/ml Gentamycin, at 1 1000 in 10 ml PBS 10 microgram/ml Transfernn (Sigma), 10 ng/ml EGF (BRL), 10 microliter of 5X10 M tniodothyromne (Sigma). 100 microliter of 10 nM ethanolamine (Sigma), and at 1 1000, and in 10 ml 200 proof ETOH. 2 microliter of 1 nM hydrocortisone (Sigma), 100 microliter of 10 nM progesterone (Sigma) and 500 microliter of 1 micromolar torskolm (Calbiochem) The cell cultures were then incubated at 37° C On Day 2. the pnmary culture media was removed and the attached cells were washed with RPMI 1640 Two ml of minimal media (RPMI 1640 contammg 10 microgram ml transfernn 1 microgram/ml insulin, 100 ng/ml Gentamycm, 50 microgram ml aprotinm, 1 microgram ml BPE) was then added, along with the following ErbB receptor ligands (recombinant human forms) EGF. HG-EGF. TGF-alpha. amphiregulin. betacellulm, and heregulm The heregulm polypeptide (Genentech. Inc ) consisted of the EGF domain only (HRG-beta 1 , 77 244 ) The other ligands consisted of the full length human polypeptide and were purchased from R& D Systems The respective ligands were added to the cultures at four different concentrations - 200 ng/ml, 100 ng/ml. 20 ng/ml and 4 ng/ml On Day 4, the media was removed from the wells, mRNA was prepared from the cells and assayed for the expression level of the markers identified in Figure 1 The markers are descnbed further in Edlund, Diabetes 47 1817- 1823 (1998) and Bouwens, J Pathology 184 234-239 (1998), and the references cited therein The mRNA readouts were used to indicate changes in the number of cells expressmg the various markers relative to precursor or mature phenotype Marker expression was analyzed by real-time quantitative RT-PCR [Gibson et al , Genome Research 6 986-994 (1996)] An ErbB ligand was determined to be positive if it resulted in an increase in expression of the relevant marker The results are shown in Figure 1 As shown, expression of the markers - RPL19, NeuroD, Pax4, PDX-1, Insulin, Glut2, GLK, Pax6. Glucagon, ISL1, Amylase, Somatostatin, Cytoker 19 - was determined The results observed for each of the respective ligands are also illustrated graphically in bar diagrams in Figures 2 (HB-EGF), 3 (heregulm), 4 (amphiregulin), 5 (EGF), 6 (TGF-alpha), and 7 (betacellulin) All of the ErbB ligands tested altered the expression of one or more of the markers All of the ligands except heregulm produced more than a doubling of PDX- 1 expression over a 48 hour exposure to ligand All of the ligands except betacellulm produced a more than two fold mcrease in Pax4 expression, and in the presence of all but heregulm. there was a more than two fold increase m msulm expression None of the ligands tested increased amylase expression, and amphiregulin, EGF, and TGF-alpha actually decreased the level of expression of the amylase marker EXAMPLE 2 Mice heterozygous (+/-) for either heregulin, ErbB2 or ErbB3 were created by gene targeting techniques, resulting in the loss of one functional gene copy and an associated decrease m targeted protein The in vivo activity of heregulin in the heterozygous mouse lines and in wild type mice (pregnant and non-pregnant) was then examined The chimenc mice were generated by gene targetmg, described in Enckson et al , Development 124 4999- 5011 (1997) The mice were mated on C57BL/6J and Balb/C mouse strains with no differences noted m heregulm response based on background strain or backcross level Adult 8-12 week old mice of each genotype, with an average weight of 20 g each were treated with a sustained 14 day systemic delivery of recombinant human heregulm-beta 1 (amino acids 177-244) using ALZA pumps [Holmes et al . Science 256 1205-1210 (1992)] Genotypic groups receiving the heregulin consisted of 6 females and 6 males each Control groups for each genotype (2 females and 3 males) received PBS (Gibco) ALZA mini-osmotic pumps (model 2002. pumping rate 0 5 microliter/hour, duration 14 days, reservoir volume 200 microliter) were filled according to manufacturer instructions, with the heregulm diluted in PBS and doses were delivered to the animals at 0 75 mg/kg/day or 1 0 mg/kg/day The pumps were stored at 4°C overnight in PBS prior to sterile implantation The animals were anesthetized with Ketamine, 75-80 mg/kg, Xylazine, 7 5-15 mg/kg, and Acepromazme, 0 75 mg/kg, delivered mtrapen toneally The filled pump, delivery portal first, was inserted into a subcutaneous pocket along the back Animals were individually housed and observed daily Any monbund animals were immediately sacnficed and necropsied Surviving animals were sacnficed and necropsied at day 14 Organ tissue was fixed m 10% neutral buffered formalin at room temperature overnight followed by storage in 70% ethanol For paraffin embedding, tissues were dehydrated through graded alcohols, followed by methyl sahcylate and overnight infiltration in Paraplast at 57° C Senal 6 micrometer sections were cut and affixed to poly- lysine coated slides pnor to hematoxylin/eosin staining and histological analysis Tolerance for the heregulm treatment vaned depending upon genotype Mortality differed between the genotypes (p<0 001) with the heregulm (+/-) animal groups having the highest mortality (12/12=100%), the ErbB2 and ErbB3 (+/-) animal groups having the lowest mortality (1/12=8%) and the wild type group having intermediate mortality (7/12=58%) There was no apparent difference in mortality by sex Both wild type and heregulm (+/-) animals receiving heregulin treatment exhibited lacnmation, dehydration, hunching ruffled fur, a cool body temperature and noticeably hypoactive The wild type and heregulin (+/-) animals also appeared to have enlarged abdommal regions The control animals receiving PBS survived the full 14 days with no clinical signs The pancreas appeared largely normal in the treated non-surviving wild type and heregulm (+/-) mice at necropsy with limited ductal ectasia and minimal hyperplasia probably reflecting the short exposure time of the animals to the admmistered heregulm (5-6 days) (see Figures 8(b) and 8(c)) In contrast, m the ErbB2 and ErbB3 (+/-) animals receiving treatment for the full 14 days, there was pronounced ductal hyperplasia and proliferation m the mam pancreatic ducts at necropsy with inflammatory cells present in the lumen of the ducts (see Figures 8(d) and 8(e)) Acmar cell injury was not widespread, although amylase levels were elevated in many of the animals

Claims: What is claimed is 1 A method of treating pancreatic dysfunction in a mammal, compnsmg administenng to said mammal an effective amount of ErbB receptor ligand 2 A method of treating pancreatic dysfunction in a mammal, compnsmg administering to said mammal an effective amount of ErbB receptor agonist antibody 3 A method of treating diabetes in a mammal, comprising admmistermg to said mammal an effective amount of ErbB receptor ligand 4 The method of claim 3. wherem said ErbB receptor ligand compnses betacellulm 5 The method of claim 3. wherem said ErbB receptor ligand compnses heregulm 6 The method of claim 4. wherem said betacellulin is administered in combination with heregulm 7 The method of claim 3. wherein said diabetes is Type I diabetes 8 The method of claim 3. wherem said ErbB receptor ligand is admmistered to said mammal using a cannula 9 A method of treating diabetes in a mammal, comprising administenng to said mammal an effective amount of ErbB receptor agomst antibody 10 A method of treating pancreatic dysfunction, compnsmg the steps of exposing, in vitro, mature beta cells or beta precursor cells from a donor mammal to an effective amount of ErbB receptor ligand or ErbB receptor agonist antibody and subsequently administenng said mature beta cells or beta precursor cells to a recipient mammal in vivo 11 The method of claim 10, wherein said donor mammal and said recipient mammal are the same mammal 12 The method of claim 10, wherem said donor mammal and said recipient mammal are different mammals 13 The method of claim 12, wherem an immunosuppressant agent is further admmistered to said recipient mammal 14 A method of stimulating or inducing proliferation of beta precursor cells or mature beta cells, compnsmg exposing said beta precursor cells or mature beta cells to an effective amount of ErbB receptor ligand 15 The method of claim 14, wherein said ErbB receptor ligand compnses betacellulm 16 The method of claim 14. wherein said ErbB receptor ligand compnses heregulm 17 A method of stimulating or mducmg proliferation of beta precursor cells or mature beta cells, compnsmg exposing said beta precursor cells or mature beta cells to an effective amount of ErbB receptor agonist antibody 18 A method of stimulating or inducing differentiation of beta precursor cells into mature beta cells, compnsmg exposing said beta precursor cells to an effective amount of ErbB receptor ligand 19 The method of claim 18. wherein said ErbB receptor ligand compnses betacellulm 20 The method of claim 18. wherem said ErbB receptor ligand compnses heregulm 21 A method of stimulating or inducing differentiation of beta precursor cells mto mature beta cells, compnsmg exposing said beta precursor cells to an effective amount of ErbB receptor agonist antibody 22 A composition compnsmg an effective amount of an ErbB receptor ligand and a pharmaceutically acceptable earner 23 A composition compnsmg an effective amount of an ErbB receptor agonist antibody and a pharmaceutically acceptable carrier 24 An article of manufacture, compnsmg a container which includes a composition compnsmg an effective amount of ErbB receptor ligand or ErbB receptor agonist antibody, and a label on said container, or a package msert, providing instruction for using said ligand or antibody in vitro or in vivo

Inventors: HUANG XIAOJIAN, STEWART TIMOTHY ANDREW, HUANG, XIAOJIAN, STEWART, TIMOTHY, ANDREW
Applicants: GENENTECH INC, GENENTECH, INC.
Application year: 2000
Main classification: A61K38
IPC codes: A61K31, A61K35, A61K38, A61K39, A61K45, A61K48, A61P3, A61P9, A61P13, A61P43, C07K16, C12N5