Abstract:
Observations regarding the role of MUC1 in promoting the nuclear accumulation of EGFR led us to propose the development of peptides to block nuclear accumulation of EGFR as a means to block breast cancer progression. One exemplary peptide, the ENLS1 peptide, promotes cell death in breast cancer cell lines. Studies in the MMTV-pyMT mouse model of breast cancer demonstrate significant anti-tumor activity.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    This invention is related to the area of cancer. In particular, it relates to anti-cancer peptides which inhibit growth and promote apoptosis. 
       BACKGROUND OF THE INVENTION 
       [0002]    MUC1 and EGFR have each been shown to play roles in the growth and progression of cancers. Recent work has demonstrated a role for MUC1 in promoting EGFR activity in the nucleus. This nuclear translocation results in EGFR/chromatin interactions at the Cyclin D1 promoter, resulting in an increase in Cyclin D-1 expression (Bitler et al., 2010b). 
         [0003]    There is a continuing need in the art to find effective ways to prevent the initiation of tumors, to inhibit the growth of cancer cells, to kill cancer cells, and to prevent metastasis of tumors. 
       SUMMARY OF THE INVENTION 
       [0004]    According to one aspect of the invention a polypeptide comprises a nuclear translocation sequence of EGFR and a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0005]    According to another aspect of the invention a polypeptide comprises (a) human EGFR amino acid residues 622-642 as shown in SEQ ID NO: 3; (b) a permutation of residues 622-642 as shown in SEQ ID NO: 3; or (c) a variant of SEQ ID NO: 3 having from one to three arginine and/or lysine residues substituted with a glutamine residue; and a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0006]    Another aspect of the invention is a method. A polypeptide is administered to a mammal. The mammal has a breast tumor, or the mammal is predisposed to breast cancer, or the mammal has had a breast tumor resected. The polypeptide comprises (a) human EGFR amino acid residues 622-642 as shown in SEQ ID NO: 3; (b) a permutation of residues 622-642 as shown in SEQ ID NO: 3; (c) a variant of SEQ ID NO: 3 having from one to three arginine and/or lysine residues substituted with a glutamine residue; or (d) a nuclear translocation sequence of EGFR. The polypeptide also comprises a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0007]    According to another aspect another method is provided. A polypeptide is administered to a mammal. The mammal has a tumor, or the mammal is predisposed to developing a tumor, or the mammal has had a tumor resected. The tumor is selected from the group consisting of ovarian, colon, lung, prostate, or pancreatic tumors. The polypeptide comprises (a) human EGFR amino acid residues 622-642 as shown in SEQ ID NO: 3; (b) a permutation of residues 622-642 as shown in SEQ ID NO: 3; (c) a variant of SEQ ID NO: 3 having from one to three arginine and/or lysine residues substituted with a glutamine residue; or (d) a nuclear translocation sequence of EGFR. The polypeptide also comprises a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0008]    According to another aspect of the invention a method of treating a cancer cell is provided. The cancer cell is contacted with a polypeptide. The polypeptide comprises (a) human EGFR amino acid residues 622-642 as shown in SEQ ID NO: 3; (b) a permutation of residues 622-642 as shown in SEQ ID NO: 3; (c) a variant of SEQ ID NO: 3 having from one to three arginine and/or lysine residues substituted with a glutamine residue; or (d) a nuclear translocation sequence of EGFR. The polypeptide also comprises a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0009]    Another aspect of the invention is a method of treating an animal tumor model. A polypeptide is administered to the animal tumor model. The polypeptide comprises (a) human EGFR amino acid residues 622-642 as shown in SEQ ID NO: 3; (b) a permutation of residues 622-642 as shown in SEQ ID NO: 3; (c) a variant of SEQ ID NO: 3 having from one to three arginine and/or lysine residues substituted with a glutamine residue; or (d) a nuclear translocation sequence of EGFR. The polypeptide also comprises a protein transduction domain which enhances translocation of attached macromolecules across cellular membranes. 
         [0010]    These and other aspects which will be apparent to those of skill in the art upon reading the specification provide the art with compositions and methods for inhibiting cancer cell growth and killing cancer cells. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1A-1B . ENLS1 peptide promotes cell death in triple-negative breast cancer cells.  FIG. 1A . Sequence for the ENLS-1 peptide (SEQ ID NO: 8) and the PTD4 protein transduction domain (SEQ ID NO: 2). BT-20 breast cancer cells were treated on alternate days for 7 days with 1 uM, 10 uM, 50 uM or 100 uM of ENLS-1, or no peptide treatment (NT) and an MT assay was performed to quantify cell number. *, P=0.001; **, P&lt;0.001, ANOVA.  FIG. 1B . MDA-MB-231 breast cancer cells were treated with either 1, 5, 50, or 100 uM ENLS-1 or control PTD4 peptide, as indicated, for either 90 minutes or 48 hours, as indicated. 
           [0012]      FIG. 2  ENLS1 inhibits tumor growth in the MMTV-pyMT mouse model. MMTV-pyMT mice were allowed to develop tumors of ˜100 mm 3  in at least one mammary gland. This was followed by once daily injection (i.p.) of the indicated concentration of ENLS-1 for [(5 days)×3]. Tumor volumes indicate the total tumor volume/mouse. 
           [0013]      FIG. 3 . Nuclear localization sequence of EGFR can serve as a dominant block to cell growth. MDA-MB-468 cells were grown for 3 days in the presence of the peptide indicated (sequence is shown in Table 1). At the end of 3 days, an MTT assay was performed to measure cell growth. 
           [0014]      FIG. 4A-4B . ENLS1 treatment reduces pEGFR levels and induces apoptosis. MDA-MB-468 cells were treated with ENLS1, control peptide (CP4) or PBS, followed by treatment with EGF (10 ng/ml) for either 30′ or 2 hours.  FIG. 4A . Cell lysates were evaluated for expression of phosphorylated EGFR (which detects phosphor-845 EGFR), phosphorylated AKT, cyclin D1 and Atg12, a marker of autophagy. Cell lysates were also evaluated for induction of apoptosis, as measured by an induction of cleaved PARP and cleaved caspase-3. Protein loading was normalized by beta-actin expression.  FIG. 4B . Cells were further fractionated to evaluate localization of phosphor-EGFR, with membrane, cytoplasmic and nuclear fractions shown. Fraction purity was evaluated by BAP31, a membrane protein and Histone H3, a nuclear protein. Molecular weights for all proteins are shown at the right. 
           [0015]      FIG. 5 . Vesicle formation occurs in ENLS1-treated cells. MDA-MB-468 cells were treated with either control peptide or ENLS1 for 30 minutes, fixed, sectioned and visualized by electron microscopy. 
           [0016]      FIG. 6A-6D . Tumor growth rate, initiation and metastasis is inhibited by ENLS1 treatment. MMTV-pyMT mice with at least 0.5 cm established tumors in at least one mammary gland were treated daily (1/day, 5 days/week×3 weeks) with the indicated doses of ENLS1/g body weight. In the case of the 40 ug/g body weight, mice were given ENLS1 2×/day for 8 days.  FIG. 6A . tumor growth rate was determined by measuring the total tumor burden in all 10 mammary glands at the end of the treatment/total tumor burden in all 10 mammary glands at the beginning of treatment.  FIG. 6B . Initiation of new tumors during the first 7 days of treatment was also determined by counting the number of new 0.5 cm tumors that formed during the course of treatment/number of days. A significant diminution of lung metastasis was also observed, with 2/9 treated mice developing visible lung mets ( FIG. 6C ) while 5/5 PBS treated mice developed lung metastases ( FIG. 6D ). 
           [0017]      FIG. 7 . MMTV-pyMT mice treated with ENLS1 have tumors with increased cleavage of PARP. At the end of 15 days of treatment (1×/day, intraperitoneal injection, [daily×5]×3), mice were sacrificed and remaining tumors were homogenized in protein lysis buffer. Proteins were separated by SDS-PAGE, and evaluated by immunoblot for expression of cyclin D1, cleaved PARP, phosph-EGFR (at residue 845), MUC1 and beta-actin (loading control). Molecular weights are shown at the right, and 5 tumor lysates are shown for both untreated and ENLS1 treated mice, as well as 2 non-tumor bearing wildtype animals. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The inventors have discovered that EGFR-related peptides, designed based on the EGFR juxtamembrane region, can be used to block the nuclear translocation of EGFR. The peptides include the tri-partite nuclear localization sequence of EGFR, which can act in a dominant-negative fashion to block nuclear translocation of EGFR. An EGFR peptide is fused to or synthesized in tandem with a protein transduction domain (e.g., PTD-4) to permit cellular uptake and intracellular action. One such peptide (dubbed ENLS1) has been tested for its ability to block breast cancer cell growth and tumor growth in a transgenic mouse model, MMTV-pyMT. Other peptides also have been tested and found to have cell growth inhibitory properties. 
         [0019]    The EGFR portion of the peptides can be based on the following sequence from EGFR: LLLVVALGIGLFM RRR HIV RKR TL RR LLQERELVEPLTPS (SEQ ID NO: 4). This sequence is juxtamembrane in the cytoplasmic domain of EGFR. The tri-partite sequence (underlined) interacts with importin-1β and is required for EGFR nuclear localization (Hsu and Hung, 2007; Lo et al., 2006). A portion of this sequence is linked to a protein transduction domain (such as PTD4 previously described by Bitler et al., 2009). The linkage can be direct or through a linker. Linkers can be, for example, runs of a single amino acid, or may be alternating runs of two amino acids. Linkers can be, for example, from 1 to 25 residues in length. One polypeptide, dubbed ENLS1, has the following sequence:  YARAAARQARA FMRRRHIVRKRTLRRLLQERE (SEQ ID NO: 8); the underlined sequence is PTD4 domain). This 32-mer peptide was made by synthesis; it is highly water soluble and stable for &gt;1 week at 4° C. It can also be made by other techniques, including in recombinant cells. Recombinant cells can be formed, for example, by transforming or transfecting cells with a recombinant vector which encodes for a polypeptide as described, operably linked to a transcription initiation site. 
         [0020]    The polypeptides of the invention do not occur in nature, but rather are made to juxtapose, a protein transduction domain with a sequence for blocking nuclear translocation of EGFR. The two sequences can be made to immediately abut one another or can be separated by a linker. The blocking sequence does not comprise all of EGFR, but instead comprises a subset of the EGFR amino acid sequence. Typically the size of the EGFR sequence will be less than 50 residues, less than 40, residues, less than 30 residues, or less than 25 residues. Smaller sequences may also be used, provided that they inhibit the nuclear translocation of endogenous EGFR. The nuclear translocation sequence may require one, two, or three of the arginine rich motifs, RRR, RKR, or RR, with or without the adjacent sequences in EGFR. Typically, the nuclear translocation sequence will be at least 6, at least 8, at least 10, at least 12, at least 14, at least 16, at least 18, at least 20 residues in length. Interestingly, permutations of the EGFR amino acid sequence also have inhibitory properties, thus the sequence of the residues is not an essential feature of the cancer cell inhibitory or apoptotic activity. 
         [0021]    The protein transduction domain that is fused or linked to the EGFR portion may comprise any protein transduction domain that is known in the art. These include without limitation PTD-4, HSV type I protein VP22, and Antenapedia protein transduction domain. See for example the extensive Table 1 of Dietz and Bahr,  Molecular and Cellular Neuroscience,  27 (2004) 85-131, which is expressly incorporated herein. Protein transduction domains enhance the cellular entry of macromolecules. The domains may be natural or synthetic. 
         [0022]    Spacers for use in fusion proteins may be additional amino acid residues that are used in fusion proteins typically to facilitate manufacture or synthesis. These can be fairly innocuous and typically are of a length of from 1 to 5 residues. The linkers can be monotonous or mixed residue. The residues can be random or sequences obtained from other proteins or designed for a particular property, e.g., physical, chemical or biological. In one aspect, spacers provide an optimum distance between the two portions of the fusion protein. 
         [0023]    The polypeptides may be formulated in any suitable vehicle for administration. Aqueous solutions may be used, but other alternatives may also be convenient, including capsules, time-release, implants, impregnated polymers, hydrophobic preparations, solids, powders, etc. The polypeptides can be combined with other anti-tumor agents, particularly with EGFR inhibitors. The polypeptides can be administered by any means known in the art, including but not limited to intravenous injection, intramuscular injection, intratumoral injection, oral, subcutaneous injection, and intralymphatic. 
         [0024]    Cancers and cancer cells which may be treated include breast, skin, colon, ovarian, prostate, cervical, colorectal, lung, brain, head and neck, pancreatic, kidney, and liver. One effect which may be observed upon administration is a reduced extent or retarded rate of initiation, growth, invasion, and metastasis. Suitable assays for measuring these processes are described in the examples. Other assays as are known in the art can be used as well. 
         [0025]    A person who is identified as having inherited genes associated with cancer is at increased risk of developing cancer. Such persons can be treated to reduce their risk of cancer initiation. Similarly, those who have been exposed to environmental risks, such as atomic bomb fall-out, nuclear fuel waste, and other pollutants, are at increased risk of developing cancer. Genes which may be mutated and the autosomal dominant disorders they cause include, but are not limited to BRCA1: breast cancer, BRCA2: breast cancer, APC: colon cancer HNPCC: colon cancer, CDKN2: melanoma. Other autosomal dominant inherited cancer risks include basal cell nevus syndrome, neurofibromatosis type 2, Carney syndrome, osteochondromatosis, multiple, chordoma, familial, paraganglioma, familial, Cowden syndrome, Peutz-Jeghers syndrome, esophageal cancer with tylosis, prostate cancer, gastric cancer, familial, renal cancer, familial, Li-Fraumeni syndrome, retinoblastoma, multiple endocrine neoplasia type 1, tuberous sclerosis, multiple endocrine neoplasia type 2, von Hippel-Lindau disease, neurofibromatosis type 1, and Wilms&#39; tumor. Autosomal recessive disorders disposing to cancer include ataxia-telangiectasia Rothmund-Thomson syndrome, Bloom syndrome xeroderma pigmentosa, Werner&#39;s syndrome, and Fanconi&#39;s anemia. 
         [0026]    EGFR inhibitors may be administered in the same treatment or prophylactic regimen as the peptides of the invention. They may be administered mixed with the peptides, or may be administered within a short time period of each other, such as within a week, within a day, or within a few hours or minutes. Thus combinations of the inhibitors and the peptides may be formed ex vivo during manufacturing and formulation or in vivo subsequent to administration to a mammal. The two agents may be combined in a package, i.e., a divided container to form a kit. Any EGFR inhibitor may be used, including kinase inhibitors. Exemplary but not exhaustive, the list of inhibitors may include panitumumab, cetuximab, gefitinib, and erlotinib. 
         [0027]    The polypeptides may be useful in treatment, prevention, or adjuvant therapies. These words do not imply any particular level of cure or efficacy. Rather, any time that a polypeptide is applied to a cell, tissue, or mammal so that a biological effect can be observed, a treatment has occurred. Since no treatment is successful on all members of a particular disease population, it is only necessary that the treatment have an effect on a useful percentage of the population. Prescreening and assessments may be performed to ascertain those individuals who will be most likely to benefit from the polypeptides of the invention. These will include those with a tumor such as a breast, brain, ovarian, colon, or pancreatic tumor. These tumors often contain altered EGFR expression. Other disease or predispositions can be assessed by determining the presence of an EGFR mutation in a germline or somatic tissue of an individual. Alternatively a biopsy tissue may be tested to determine the efficacy or likely efficacy of the polypeptide for that particular individual. Family history of tumors may also be used as an indication that treatment may be beneficial. Exposure to carcinogens may be used as an indication that treatment may be beneficial. 
         [0028]    Animal models of various cancers and other diseases may be used to assess the effect of the polypeptides with other agents. Combined additive or combined synergistic effects may be determined in animal models. Cellular models and tissue models may also be used, typically in advance of animal models or clinical testing. 
         [0029]    The above disclosure generally describes the present invention. All references disclosed herein are expressly incorporated by reference. A more complete understanding can be obtained by reference to the following specific examples which are provided herein for purposes of illustration only, and are not intended to limit the scope of the invention. 
       Example 1 
     Activity Against Cancer Cell Line 
       [0030]    We first evaluated the ability of ENLS1 to inhibit the growth of breast cancer cell lines in culture. For these studies, we evaluated the effects of ENLS1 on the growth of MDA-MB-231, and BT20, both of which are positive for EGFR expression and have a basal-like phenotype. We found ENLS1 to have not only a strong anti-growth phenotype, but also a very potent killing phenotype. Treatment of triple-negative breast cancer cells (both BT20 and MDA-MB-231) results in an induction of cell death as measured by MTT assay ( FIG. 1A ). 
       Example 2 
     Activity in Mouse Model 
       [0031]    We have also determined that ENLS1 can block tumor growth in the MMTV-pyMT transgenic mouse model of breast cancer. We chose this model as it has been previously demonstrated to be an excellent model for human breast cancer (Lin et al., 2003). Furthermore, its initiation is not dependent on EGFR activity, and is therefore an excellent model of spontaneous disease (Andrechek and Muller, 2000). We began treatment of tumor bearing MMTV-pyMT mice with 25 ug/g body weight ENLS1, but this treatment was met with pulmonary toxicity (data not shown). We next began treatment of tumor bearing MMTV-pyMT mice with 1 ug/g body weight ENLS1, and this treatment gave no observable toxicities. Based on this lack of toxicity, we began increasing the dosage of ENLS1 to 5 ug/g body weight, followed by 10 and 15 ug/g body weight. We did not see any apparent toxicity at any of these doses. We observed significant anti-tumor effects at both 10 and 15 ug/g body weight dosages, compared to either the lower concentration doses or a PTD4 control injection ( FIG. 2 ). In both of these cases, we observed no significant growth of tumors in these mice, evaluating growth of tumors in 10 glands in each case. These results indicate that ENLS1 has potent anti-tumor activity in the MMTV-pyMT mouse model of breast cancer. 
       Example 3 
     EGFR Juxtamembrane Peptides Kill Breast Cancer Cells 
       [0032]    We have evaluated the efficacy of 14 different drugs for their ability to inhibit the growth of triple negative breast cancers. We have identified one of these drugs (ENLS1), containing hEGFR 622-42 , that effectively blocks tumor cell growth in both in vitro cell growth assays and in an established mouse model of breast cancer. We investigated the mechanism of action for this drug and found that it induces apoptosis, accompanied by membrane blebbing and reduction of nuclear localization of erbB1. Sequence identity indicates a block of erbB1, erbB2 and erbB3 nuclear translocation. 
         [0033]    Recent data from our lab has demonstrated a prominent role for MUC 1 in promoting the nuclear activity of erbB receptors in driving transformation (Bitler et al., Journal of Cell Science, 2010). Given this activity, we focused on blocking nuclear localization of erbB receptors and MUC1 for developing anti-tumor peptides. The erbB receptors have significant homology in the nuclear localization sequence, all bearing a tri-partite basic amino acid sequence in their juxtamembrane region. In addition, a 3 residue basic sequence in the juxtamembrane of MUC1 has also been shown to drive nuclear localization of MUC1. We therefore designed peptides around this region of EGFR, and those sequences are as shown in Table 1. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 Day 3 
                 SEQ  
               
               
                   
                 Name 
                 Sequence 
                 Change 
                 Survival 
                 ID NO: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 hEGFR 622-42   
                 ENLS-1 
                 PTD4-FMRRRHIVRKRTLRRLLQERE 
                   
                   5% 
                 9 
               
               
                   
               
               
                 hEGFR 622-34   
                 ENLS-2 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 -RRLLQERE 
                  73% 
                 10 
               
               
                   
               
               
                 hEGFR 628-42   
                 ENLS-3 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 FMRRRH- 
                  37% 
                 11 
               
               
                   
               
               
                 hEGFR 624-36   
                 ENLS-4 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 FM--LLQERE 
                  78% 
                 12 
               
               
                   
               
               
                 hEGFR 632-42   
                 ENLS-5 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 FMRRRHIVRK- 
                  62% 
                 13 
               
               
                   
               
               
                 hEGFR 637-48   
                 EBL-1 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Basolateral Domain 
                  96% 
                 14 
               
               
                   
               
               
                 hEGFR 637-48LVΔ4×A   
                 cEBL-1 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 EBL-1 L and V to  A   
                  98% 
                 15 
               
               
                   
               
               
                 hEGFR s622-42   
                 nlsCPv1 
                 PTD4-FRMHRIRVRTKLRLRLRQERE 
                 Scramble ENLS- 1 
                   5% 
                 16 
               
               
                 hEGFR 622-42RKΔ8×A   
                 nlsCPv2  
                 PTD4-FM AAA HIV AAA TL AA LLQERE 
                   A  for R and K 
                 Not Sol. 
                 17 
               
               
                   
               
               
                 hEGFR s622-34   
                 cENLS-2 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Scramble ENLS- 2 
                  83% 
                 18 
               
               
                   
               
               
                 hEGFR s628-42   
                 cENLS-3 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Scramble ENLS-3 
                  51% 
                 19 
               
               
                   
                   
                   
                   
                   
                 20 
               
               
                 hEGFR 624-36RKΔ3×D   
                 nlsCPv4 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 ENLS-4 R to  D   
                  99% 
                 21 
               
               
                   
               
               
                 hEGFR 622-42RKΔ3×D   
                 nlsCPv5 
                 PTD4-FMR D RHIVR D RTLR D LL Q ERE 
                 ENLS-1 R to  D   
                 100% 
                 22 
               
               
                 hEGFR 622-42RKΔ3×Q   
                 nlsCPv6 
                 PTD4-FMR Q RHIVR Q RTLR Q LLQERE 
                 ENLS-1 R to  Q   
                  35% 
                 23 
               
               
                   
               
             
          
         
       
     
         [0034]    We next evaluated the ability of each of these peptides to inhibit the growth of the triple-negative breast cancer line, MDA-MB-468. In our previous studies, we had demonstrated that these cells were particularly sensitive to a loss of MUC1 expression for nuclear-EGFR-dependent effects, including Cyclin D1 expression. Cells were evaluated for effects of peptide on growth inhibition by MTT assay at 1, 3 and 5 days of 20 uM peptide treatment. Peptide concentration is based on evaluations of the ability of the peptide to block cell growth at 0.1 uM-100 uM concentrations, where 20 uM was found to optimally reduce cell growth in the active peptide, without any effects in the control peptide (data not shown). We then treated MDA-MB-468 cells with 14 derivatives of the peptide, including versions with the full sequence, portions of the sequence, and acidic substitutions for the basic amino acids (which were synthesized as controls) (Table 1). We found that a key 21 amino acid sequence is optimal for causing cell death, which is encompassed by ENLS1 ( FIG. 1 ). In addition, while data shown is for MDA-MB-468 cells, growth inhibitory effects were observed for MDA-MB-231 and BT20 cells as well (both triple negative breast cancers). 
         [0035]    We then proceeded to evaluate cell death in other cell types, including HER2 and HER3 positive cells, and HER negative cells. In addition, we evaluated the efficacy of ENLS1 on pancreatic cells. Surprisingly, we found that ENLS1 effectively blocks cell growth in 2 different pancreatic cell lines (BxPC3 and AsPc1) as well as HER2 positive T47D breast cancer cells. It had no effect, though, on HEK293 cells, which do not express the HER receptors (data not shown). 
       Example 4 
     ENLS1-Dependent Cell Death is Via Apoptosis 
       [0036]    We next set out to determine whether cell death was occurring by the induction of apoptosis. For this, we treated cells for either 30 minutes or 2 hours and made protein lysates ( FIG. 2   a ). Lysates were then analyzed by SDS-PAGE and immunoblot for expression of cleaved caspase 3 and cleaved PARP, both markers of the induction of apoptosis. We found that by 2 hours of peptide treatment, both were induced, indicating that cells were dying by apoptosis. In addition, we found that these cancer cells had established a state of autophagy for survival (as demonstrated by expression of atg12). ENLS1 was also observed to block the formation of atg12, indicating a loss of the cell preserving the autophagic state. No effects on protein expression for any proteins evaluated were affected by our control peptide. In addition, we observed a loss of Cyclin D1 expression, which is known to be induced by nuclear EGFR. Finally, we found a loss of pAKT expression, which we subsequently found to correlate with a loss of total AKT expression. We are currently evaluating the mechanism by which this may be occurring. 
         [0037]    We next set out to verify that we are blocking the nuclear translocation of EGFR, which we evaluated by fractionating the cytoplasmic, membrane and nuclear fraction of cells treated with ENLS1 versus ENLSCP5 (the control peptide with 3 key amino acids changed from basic (arginine) to acidic (aspartic acid). In  FIG. 2   b , we demonstrate that while EGFR is phosphorylated on residue 845 (p-EGFR) in response to EGF treatment, this form of EGFR does not translocate to the nucleus in the presence of ENLS1, whereas it readily translocates to the nucleus in the control (either vehicle or CP4 control peptide). ENLS4 also inhibits the nuclear translocation of p-EGFR, as ENLS4 is the minimal nuclear translocation sequence of EGFR. Interestingly, ENLS4 has minimal effects on cell growth ( FIG. 1 ), indicating that the loss of EGFR translocation can inhibit cell growth, but that another function must be being affected by ENLS1. 
       Example 5 
     ENLS1 Treatment Induces Vesicle Formation in Cells 
       [0038]    To determine how ENLS1 was driving the cells to undergo apoptosis, we began by evaluating the morphological changes that are observed upon ENLS1 treatment. We noticed that within a few hours of peptide treatment, cells began to exhibit membrane blebbing, demonstrating a membrane ‘bubbling’ (data not shown). We decided to look by electron microscopy to determine what changes were occurring at a sub-structural level. Upon performance of scanning electron microscopy, we were able to identify the formation of multiple vesicles under the plasma membrane of ENLS1 treated cells, but not in control-treated cells ( FIG. 3 ). We are currently investigating the origin of these vesicles through investigations into membrane integrity, calcium flux and exocytosis in the cell. 
       Example 6 
     ENLS1 Inhibits Tumor Growth and Metastasis in the MMTV-pyMT Mouse Model of Breast Cancer 
       [0039]    We have been extensively testing the ability of ENLS1 to affect breast cancer growth in vivo. We have been testing the MMTV-pyMT model of breast cancer, a model that forms spontaneous breast tumors in all 10 mammary glands of the mouse. This model has been extensively evaluated by pathologists, and shown to undergo many of the same changes that occur in human breast cancer. In addition this is a metastatic model, with metastases forming in the lung in close to 100% of the animals. 
         [0040]    MMTV-pyMT mice were allowed to develop tumors of at least 0.5 cm in diameter prior to treatment, and were then treated for 15 days with either 1 ug/g body weight (n=1), 5 ug/g body weight (n=1), 10 ug/g body weight (n=4), 15 ug/g body weight (n=1), or 40 ug/g body weight (n=1). This was done initially to determine if treatment with ENLS1 would result in toxicity. We found that no toxicity to the animal (as determined by evaluated changes in weight, grooming, gait) was observed at any of the treatment groups. We next began to evaluate the effects of peptide treatment on tumor growth. The MMTV-pyMT model is a stochastically developing tumor model, with tumors developing in all ten mammary glands from as early as 6 weeks of age. This allows us to determine both how drug treatment effects established tumors as well as newly initiated tumors.  FIG. 4   a  shows that ENLS1 exhibits strong antitumor activity, as shown by the tumor growth rate in the animals treated, also that this effect on tumor growth increases as the amount of drug increases. In  FIG. 4   b , we demonstrate that ENLS1 treatment inhibits the initiation of new tumors during the treatment. Finally, we found a striking reduction in lung metastases in treated mice versus control mice. This model is known to be 100% metastatic to the lungs, and we therefore excised the lungs of untreated and control mice to evaluate effects of ENLS1 on lung metastasis. We found only 2/9 mice that had been treated with ENLS1 with visible lung metastases, while all of the control mice (5/5) had lung metastases. 
       Example 7 
     Inhibition of Tumor Growth in the MMTV-pyMT Model is Associated with Apoptosis 
       [0041]    Finally, we have evaluated the molecular events occurring in the tumors excised from treated mice. Mice that had received 10 ug/g body weight of ENLS1 for 15 days were sacrificed and protein lysates prepared from the remaining tumors. We then evaluated these protein lysates for expression of cleaved PARP as an indicator of the induction of apoptosis, and found a significant increase in cleaved PARP in ENLS1 treated tumors ( FIG. 5 ). We also evaluated tumors for the expression of Cyclin D1, pY845EGFR, and MUC1, but did not observe any significant differences. 
       REFERENCES 
       [0042]    The disclosure of each reference cited is expressly incorporated herein.
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