Efficient inhibition of an intraperitoneal xenograft model of human ovarian cancer by HSulf-1 gene delivered by biodegradable cationic heparin-polyethyleneimine nanogels.

The HSulf-1 (heparan sulfate 6-O-endosulfatase 1) gene is an important element             that modulates the sulfation status of heparan sulfate proteoglycans (HSPGs),             leading to the interference of HSPG-related signal transduction pathways. HSulf-1             plays a key role in regulating cell proliferation, tumorigenesis and angiogenesis.             Recently, some studies have reported that HSulf-1 is a down-regulated gene in             the majority of examined tumor types. In our present study, a recombinant plasmid             DNA carrying HSulf-1-cDNA (pHSulf-1) was constructed. The antitumor effect of             pHSulf-1 delivered by heparin-polyethyleneimine (HPEI) nanogels on human ovarian             cancer and the possible mechanisms of the antitumor efficacy in vivo were further             investigated. Heparin-polyethyleneimine (HPEI) nanogels, as a new safe non-viral             gene delivery carrier, were prepared to deliver the plasmid expressing HSulf-1             into HSulf-1-deficient SKOV3 human ovarian cancer cells in vitro and in vivo.             pHSulf-1 could be efficiently transfected into SKOV3 ovarian cancer cells by HPEI             nanogels in vitro and in vivo. Stable expression of HSulf-1 in vitro and in vivo             was verified by reverse transcription polymerase chain reaction (RT-PCR) and Western             blot analysis. Furthermore, a SKOV3 intraperitoneal ovarian carcinomatosis model             was established to investigate the growth inhibition function of pHSulf-1 in nude             mice. Tumor weight was measured. An anti-angiogenesis effect of pHSulf-1 in vivo             was detected by CD31 immunostaining and alginate-encapsulate tumor cell assay.             Assessment of apoptotic cells and proliferation index in tumor tissues were performed             by TUNEL assay and Ki‑67 immunostaining. Intraperitoneal injection of pHSulf-1/HPEI             complexes efficiently reduced tumor weight by approximately 87% compared with             control groups (P<0.01). Meanwhile, reduction in angiogenesis, inhibition of             cell proliferation, as well as induction of tumor cell apoptosis were observed,             without apparent systemic toxic effects. Collectively, these observations provide             the first evidence that pHSulf-1 delivered by HPEI nanogels may become a promising             therapeutic strategy against human ovarian cancer.

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title: Cloning and Characterization of Two Extracellular Heparin-degrading Endosulfatases in Mice and Humans*
abstract: Here we report the cloning of a full-length cDNA encoding the human ortholog (HSulf-1) of the developmentally regulated putative sulfatases QSulf-1 (Dhoot, G. K., Gustafsson, M. K., Ai, X., Sun, W., Standiford, D. M., and Emerson, C. P., Jr. (2001) Science 293, 1663–1666) and RSulfFP1 (Ohto, T., Uchida, H., Yamazaki, H., Keino-Masu, K., Matsui, A., and Masu, M. (2002) Genes Cells 7, 173–185) as well as a cDNA encoding a closely related protein, designated HSulf-2. We have also obtained cDNAs for the mouse orthologs of both Sulfs. We demonstrate that the proteins encoded by both classes of cDNAs are endoproteolytically processed in the secretory pathway and are released into conditioned medium of transfected CHO cells. We demonstrate that the mammalian Sulfs exhibit arylsulfatase activity with a pH optimum in the neutral range; moreover, they can remove sulfate from the C-6 position of glucosamine within specific subregions of intact heparin. Taken together, our results establish that the mammalian Sulfs are extracellular endosulfatases with strong potential for modulating the interactions of heparan sulfate proteoglycans in the extracellular microenvironment.

title: Regulation of Wnt signaling and embryo patterning by an extracellular sulfatase.
abstract: The developmental signaling functions of cell surface heparan sulfate proteoglycans (HSPGs) are dependent on their sulfation states. Here, we report the identification of QSulf1, the avian ortholog of an evolutionarily conserved protein family related to heparan-specific N-acetyl glucosamine sulfatases. QSulf1 expression is induced by Sonic hedgehog in myogenic somite progenitors in quail embryos and is required for the activation of MyoD, a Wnt-induced regulator of muscle specification. QSulf1 is localized on the cell surface and regulates heparan-dependent Wnt signaling in C2C12 myogenic progenitor cells through a mechanism that requires its catalytic activity, providing evidence that QSulf1 regulates Wnt signaling through desulfation of cell surface HSPGs.

title: Role of heparan sulfate proteoglycans in cell signaling and cancer.
abstract: Publisher Summary Heparan sulfate proteoglycans (HSPGs) are composed of a protein core modified on specific serine residues by the addition of heparan sulfate (HS) glucosaminoglycans (GAGs) synthesized in the Golgi. Three distinct types of proteins can serve as the HSPG cores: the transmembrane proteins encoded by the syndecan genes, the glycosylphosphatidylinositol (GPI) membrane-bound glypicans, and the extracellular matrix secreted perlecan proteins. The chapter presents the two major advances made in understanding the role of HSPGs in development and cancer. First, studies in Drosophila have identified many mutations in either the biosynthetic enzymes for example, Sugarless (Sgl), Sulfateless (Sfl), Tout velu (Ttv); or the protein cores for example, syndecans and glypicans. Analysis of the mutant phenotypes has revealed the critical roles of HSPGs in modulating various growth factor signaling pathways. Second, many mutations linked to human cancers have been isolated and shown to correspond to defects in the biosynthesis of HSPGs. The chapter explains the importance of HSPGs in cell signaling and provides insights into their functions. Modulating the activity of HSPGs could influence the development of cancers caused by aberrant cell signaling. The chapter concludes that HSPGs constitute important targets for therapeutics to treat some human tumors.

title: Functions of heparan sulfate proteoglycans in cell signaling during development
abstract: Heparan sulfate proteoglycans (HSPGs) are cell-surface and extracellular matrix macromolecules that are composed of a core protein decorated with covalently linked glycosaminoglycan (GAG) chains. In vitro studies have demonstrated the roles of these molecules in many cellular functions, and recent in vivo studies have begun to clarify their essential functions in development. In particular, HSPGs play crucial roles in regulating key developmental signaling pathways, such as the Wnt, Hedgehog, transforming growth factor-β, and fibroblast growth factor pathways. This review highlights recent findings regarding the functions of HSPGs in these signaling pathways during development.

title: Heparan sulfate proteoglycans at a glance
abstract: Proteoglycans are abundant components of the cell surface and extracellular matrix that mediate critical interactions between cells and their environment. They play a variety of biological roles in normal tissues and in response to injury and disease. Proteoglycans regulate the distribution of

title: Loss of HSulf-1 Up-regulates Heparin-binding Growth Factor Signaling in Cancer*
abstract: Emerging data suggest that signaling by heparin-binding growth factors is influenced by the sulfation state of N-acetylglucosamine residues of heparan sulfate proteoglycans (HSPGs). Here we report that the recently identified protein HSulf-1, a heparin-degrading endosulfatase, encodes a cell surface-associated enzyme that diminishes sulfation of cell surface HSPGs. The message encoding this enzyme is readily detectable in a variety of normal tissues, including normal ovarian surface epithelial cells, but is undetectable in 5 of 7 ovarian carcinoma cell lines and markedly diminished or undetectable in ∼75% of ovarian cancers. Similar down-regulation is also observed in breast, pancreatic, renal cells, and hepatocellular carcinoma lines. Re-expression of HSulf-1 in ovarian cancer cell lines resulted in diminished HSPG sulfation, diminished phosphorylation of receptor tyrosine kinases that require sulfated HSPGs as co-receptors for their cognate ligands, and diminished downstream signaling through the extracellular signal-regulated kinase pathway after treatment with fibroblast growth factor-2 or heparin-binding epidermal growth factor. Consistent with these changes, HSulf-1 re-expression resulted in reduced proliferation as well as sensitivity to induction of apoptosis by the broad spectrum kinase inhibitor staurosporine and the chemotherapeutic agent cisplatin. Collectively, these observations provide evidence that HSulf-1 modulates signaling by heparin-binding growth factors, and HSulf-1 down-regulation represents a novel mechanism by which cancer cells can enhance growth factor signaling.

title: HSulf-1 modulates HGF-mediated tumor cell invasion and signaling in head and neck squamous carcinoma
abstract: Recently, we cloned a novel sulfatase domain-containing downregulated gene, HSulf-1, which modulates heparin-binding growth factor signaling in ovarian cancer. Based on the pilot data showing the loss of HSulf-1 in head and neck squamous cell carcinoma cell lines (SCCHN), we sought to employ SCCHN as a model to define the role of HSulf-1 in the molecular regulation of tumorigenecity. Three SCCHN lines (012SCC, WMMSCC, and 015SCC) had no detectable HSulf-1 mRNA. Clonal lines of HSulf-1-expressing 012SCC attenuated the activation of ERK/mitogen-activated protein kinase (MAPK) signaling mediated by fibroblast growth factor (FGF-2) and both ERK/MAPK and Akt signaling mediated by hepatocyte growth factor (HGF). Consistent with this downregulation, phosphorylation of HGF receptor, c-Met, which is frequently overexpressed in SCCHN, was also attenuated in HSulf-1 clonal 012SCC cell lines. HGF markedly enhanced the motility and migration of vector-transfected cells in a transwell invasion chamber. However, HGF-mediated motility and invasion was attenuated in HSulf-1 clonal 012SCC cell lines. In addition, transfected cells displayed significant growth inhibition concomitant with a decrease in mitogenecity, as measured by thymidine incorporation and increased sensitivity to staurosporine- and cisplatin-induced apoptosis. These data suggest that HSulf-1 normally functions as a negative regulator in cell growth and loss of HSulf-1 in SCCHN potentiates growth factor signaling, enhances motility, invasiveness and inhibits stress-induced apoptosis, with a resulting increase in tumorigenecity.

title: hSulf1 Sulfatase promotes apoptosis of hepatocellular cancer cells by decreasing heparin-binding growth factor signaling.
abstract: The heparin-binding growth factors fibroblast growth factor (FGF) and hepatocyte growth factor (HGF) are potent mitogens for hepatocellular carcinomas (HCCs). Heparin-binding growth factor signaling is regulated by sulfation of cell-surface heparan sulfate proteoglycans (HSPGs). We hypothesized that hSulf1, a recently described sulfatase, regulates growth signaling in HCCs.



Expression of hSulf1 in human HCC tumors was determined by real-time PCR. Down-regulation of hSulf1 expression was investigated by analyzing loss of heterozygosity (LOH) at the hSulf1 locus and the effect of the DNA methylation inhibitor 5-aza-deoxycytidine on hSulf1 expression. The subcellular location of hSulf1 and sulfation state of cell-surface HSPGs were assessed by immunocytochemistry. FGF and HGF signaling was examined by phospho-specific immunoblot analysis. Cell growth was measured by trypan blue exclusion, and the MTT assay and apoptosis were quantitated by fluorescence microscopy.



hSulf1 expression was decreased in 29% of HCCs and 82% of HCC cell lines. There was LOH at the hSulf1 locus in 42% of HCCs. Treatment with 5-aza-deoxycytidine reactivated hSulf1 expression in hSulf1-negative cell lines. Low hSulf1-expressing cells showed increased sulfation of cell-surface HSPGs, enhanced FGF and HGF-mediated signaling, and increased HCC cell growth. Conversely, forced expression of hSulf1 decreased sulfation of cell-surface HSPGs and abrogated growth signaling. HCC cells with high-level hSulf1 expression were sensitive to staurosporine- or cisplatin-induced apoptosis, whereas low expressing cells were resistant. Transfection of hSulf1 into hSulf1-negative cells restored staurosporine and cisplatin sensitivity.



Down-regulation of hSulf1 contributes to hepatocarcinogenesis by enhancing heparin-binding growth factor signaling and resistance to apoptosis.

title: Epigenetic silencing of HSulf-1 in ovarian cancer:implications in chemoresistance
abstract: To investigate the mechanism by which HSulf-1 expression is downregulated in ovarian cancer, DNA methylation and histone acetylation of HSulf-1 was analysed in ovarian cancer cell lines and primary tumors. Treatment of OV207 and SKOV3 by 5-aza-2′-deoxycytidine resulted in increased transcription of HSulf-1. Sequence analysis of bisulfite-modified genomic DNA from ovarian cell lines and primary tumors without HSulf-1 expression revealed an increase in the frequency of methylation of 12 CpG sites in exon 1A. Chromatin immunoprecipitation assays showed an increase in histone H3 methylation in cell lines without HSulf-1 expression. To assess the significance of HSulf-1 downregulation in ovarian cancer, OV167 and OV202 cells were transfected with HSulf-1 siRNA. Downregulation of HSulf-1 expression in OV167 and OV202 cells lead to an attenuation of cisplatin-induced cytotoxicity. Moreover, patients with ovarian tumors expressing higher levels of HSulf-1 showed a 90% response rate (27/30) to chemotherapy compared to a response rate of 63% (19/30) in those with weak or moderate levels (P=0.0146, χ2 test). Collectively, these data indicate that HSulf-1 is epigenetically silenced in ovarian cancer and that epigenetic therapy targeting HSulf-1 might sensitize ovarian tumors to conventional first-line therapies.

title: Regulation of HSulf-1 expression by variant hepatic nuclear factor 1 in ovarian cancer.
abstract: We recently identified HSulf-1 as a down-regulated gene in ovarian carcinomas. Our previous analysis indicated that HSulf-1 inactivation in ovarian cancers is partly mediated by loss of heterozygosity and epigenetic silencing. Here, we show that variant hepatic nuclear factor 1 (vHNF1), encoded by transcription factor 2 gene (TCF2, HNF1beta), negatively regulates HSulf-1 expression in ovarian cancer. Immunoblot assay revealed that vHNF1 is highly expressed in HSulf-1-deficient OV207, SKOV3, and TOV-21G cell lines but not in HSulf-1-expressing OSE, OV167, and OV202 cells. By short hairpin RNA-mediated down-regulation of vHNF1 in TOV-21G cells and transient enhanced vHNF1 expression in OV202 cells, we showed that vHNF1 suppresses HSulf-1 expression in ovarian cancer cell lines. Reporter assay and chromatin immunoprecipitation experiments showed that vHNF1 is specifically recruited to HSulf-1 promoter at two different vHNF1-responsive elements in OV207 and TOV-21G cells. Additionally, down-regulation of vHNF1 expression in OV207 and TOV-21G cells increased cisplatin- or paclitaxel-mediated cytotoxicity as determined by both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and clonogenic assays and this effect was reversed by down-regulation of HSulf-1. Moreover, nude mice bearing TOV-21G cell xenografts with stably down-regulated vHNF1 were more sensitive to cisplatin- or paclitaxel-induced cytotoxicity compared with xenografts of TOV-21G clonal lines with nontargeted control short hairpin RNA. Finally, immunohistochemical analysis of 501 ovarian tumors including 140 clear-cell tumors on tissue microarrays showed that vHNF1 inversely correlates to HSulf-1 expression. Collectively, these results indicate that vHNF1 acts as a repressor of HSulf-1 expression and might be a molecular target for ovarian cancer therapy.

title: HSulf-1 and HSulf-2 Are Potent Inhibitors of Myeloma Tumor Growth in Vivo*
abstract: To participate as co-receptor in growth factor signaling, heparan sulfate must have specific structural features. Recent studies show that when the levels of 6-O-sulfation of heparan sulfate are diminished by the activity of extracellular heparan sulfate 6-O-endosulfatases (Sulfs), fibroblast growth factor 2-, heparin binding epidermal growth factor-, and hepatocyte growth factor-mediated signaling are attenuated. This represents a novel mechanism for regulating cell growth, particularly within the tumor microenvironment where the Sulfs are known to be misregulated. To directly test the role of Sulfs in tumor growth control in vivo, a human myeloma cell line was transfected with cDNAs encoding either of the two known human endosulfatases, HSulf-1 or HSulf-2. When implanted into severe combined immunodeficient (SCID) mice, the growth of these tumors was dramatically reduced on the order of 5- to 10-fold as compared with controls. In addition to an inhibition of tumor growth, these studies revealed the following. (i) HSulf-1 and HSulf-2 have similar functions in vivo. (ii) The extracellular activity of Sulfs is restricted to the local tumor cell surface. (iii) The Sulfs promote a marked increase in extracellular matrix deposition within tumors that may, along with attenuated growth factor signaling, contribute to the reduction in tumor growth. These findings demonstrate that dynamic regulation of heparan sulfate structure by Sulfs present within the tumor microenvironment can have a dramatic impact on the growth and progression of malignant cells in vivo.

title: HSulf-1 inhibits angiogenesis and tumorigenesis in vivo.
abstract: We previously identified HSulf-1 as a down-regulated gene in several tumor types including ovarian, breast, and hepatocellular carcinomas. Loss of HSulf-1, which selectively removes 6-O-sulfate from heparan sulfate, up-regulates heparin-binding growth factor signaling and confers resistance to chemotherapy-induced apoptosis. Here we report that HSulf-1 expression in MDA-MB-468 breast carcinoma clonal lines leads to reduced proliferation in vitro and reduced tumor burden in athymic nude mice in vivo. Additionally, xenografts derived from HSulf-1-expressing stable clones of carcinoma cells showed reduced vessel density, marked necrosis, and apoptosis, indicative of inhibition of angiogenesis. Consistent with this observation, HSulf-1-expressing clonal lines showed reduced staining with the endothelial marker CD31 in Matrigel plug assay, indicating that HSulf-1 expression inhibits angiogenesis. More importantly, HSulf-1 expression in the xenografts was associated with a reduced ability of vascular endothelial cell heparan sulfate to participate in a complex with fibroblast growth factor 2 (FGF-2) and its receptor tyrosine kinase FGF receptor 1c. In vitro, short hairpin RNA-mediated down-regulation of HSulf-1 in human umbilical vein endothelial cells (HUVEC) resulted in an increased proliferation mediated by heparan sulfate-dependent FGF-2, hepatocyte growth factor, and vascular endothelial growth factor 165 (VEGF165) but not by heparan sulfate-independent VEGF121. HSulf-1 down-regulation also enhanced downstream signaling through the extracellular signal-regulated kinase pathway compared with untreated cells. Consistent with the role of heparan sulfate glycosaminoglycan sulfation in VEGF-mediated signaling, treatment of HUVEC cells with chlorate, which inhibits heparan sulfate glycosaminoglycan sulfation and therefore mimics HSulf-1 overexpression, led to an attenuated VEGF-mediated signaling. Collectively, these observations provide the first evidence of a novel mechanism by which HSulf-1 modulates the function of heparan sulfate binding VEGF165 in proliferation and angiogenesis.

title: Enhanced levels of Hsulf-1 interfere with heparin-binding growth factor signaling in pancreatic cancer
abstract: Hsulf-1 is a newly identified enzyme, which has the ability to decrease the growth of hepatocellular, ovarian, and head and neck squamous cell carcinoma cells by interfering with heparin-binding growth factor signaling. Since pancreatic cancers over-express a number of heparin-binding growth factors and their receptors, the expression and function of this enzyme in pancreatic cancer was analyzed.ResultsPancreatic cancer samples expressed significantly (22.5-fold) increased Hsulf-1 mRNA levels compared to normal controls, and Hsulf-1 mRNA was localized in the cancer cells themselves as well as in peritumoral fibroblasts. 4 out of 8 examined pancreatic cancer cell lines expressed Hsulf-1, whereas its expression was below the level of detection in the other cell lines. Stable transfection of the Hsulf-1 negative Panc-1 pancreatic cancer cell line with a full length Hsulf-1 expression vector resulted in increased sulfatase activity and decreased cell-surface heparan-sulfate proteoglycan (HSPG) sulfation. Hsulf-1 expression reduced both anchorage-dependent and -independent cell growth and decreased FGF-2 mediated cell growth and invasion in this cell line.ConclusionHigh expression of Hsulf-1 occurs in the stromal elements as well as in the tumor cells in pancreatic cancer and interferes with heparin-binding growth factor signaling.

title: Extracellular Sulfatases, Elements of the Wnt Signaling Pathway, Positively Regulate Growth and Tumorigenicity of Human Pancreatic Cancer Cells
abstract: Heparan sulfate proteoglycans (HSPGs) are control elements in Wnt signaling, which bind extracellularly to Wnt ligands and regulate their ability to interact with signal transduction receptors on the cell surface. Sulf-1 and Sulf-2 are novel extracellular sulfatases that act on internal glucosamine-6-sulfate (6S) modifications within HSPGs and thereby modulate HSPG interactions with various signaling molecules, including Wnt ligands. Emerging evidence indicates the importance of reactivated Wnt signaling in a number of cancers, including pancreatic adenocarcinoma. Principle Findings Both Sulf proteins were upregulated in human pancreatic adenocarcinoma tumors and were broadly expressed in human pancreatic adenocarcinoma cell lines. Expression of human extracellular sulfatases Sulf-1 and Sulf-2 enhanced Wnt signaling in a reconstituted system. Three of four pancreatic adenocarcinoma cell lines tested exhibited autocrine Wnt signaling, in that extracellular Wnt ligands were required to initiate downstream Wnt signaling. Exposure of these pancreatic adenocarcinoma cells to a catalytically inactive form of Sulf-2 or siRNA-mediated silencing of endogenous Sulf-2 inhibited both Wnt signaling and cell growth. Sulf-2 silencing in two of these lines resulted in markedly reduced tumorigenesis in immunocompromised mice.  We have identified the Sulfs as potentiators of autocrine Wnt signaling in pancreatic cancer cells and have demonstrated their contribution to the growth and tumorigenicity of these cells. Since the Sulfs are extracellular enzymes, they would be attractive targets for therapy of pancreatic cancer. Our results run counter to the prevailing view in the literature that the Sulfs are negative regulators of tumorigenesis.

title: Gene therapy clinical trials worldwide 1989–2004—an overview
abstract: In 1989, Rosenberg et al. performed the first human gene therapy trial when they used a retrovirus to introduce the gene coding for resistance to neomycin into human tumor‐infiltrating lymphocytes before infusing them into five patients with advanced melanoma. This study demonstrated the feasibility of using retroviral gene transduction in humans and set the stage for further studies. Since then, over 900 clinical trials have been completed, are ongoing or have been approved worldwide. These trials have been designed to establish feasibility and safety, to demonstrate the reality of expression of therapeutic protein(s) in vivo by the genes transferred and, in some cases, to show therapeutic benefit.

title: A polymer library approach to suicide gene therapy for cancer.
abstract: Optimal gene therapy for cancer must (i) deliver DNA to tumor cells with high efficiency, (ii) induce minimal toxicity, and (iii) avoid gene expression in healthy tissues. To this end, we generated a library of >500 degradable, poly(beta-amino esters) for potential use as nonviral DNA vectors. Using high-throughput methods, we screened this library in vitro for transfection efficiency and cytotoxicity. We tested the best performing polymer, C32, in mice for toxicity and DNA delivery after intratumor and i.m. injection. C32 delivered DNA intratumorally approximately 4-fold better than one of the best commercially available reagents, jetPEI (polyethyleneimine), and 26-fold better than naked DNA. Conversely, the highest transfection levels after i.m. administration were achieved with naked DNA, followed by polyethyleneimine; transfection was rarely observed with C32. Additionally, polyethyleneimine induced significant local toxicity after i.m. injection, whereas C32 demonstrated no toxicity. Finally, we used C32 to deliver a DNA construct encoding the A chain of diphtheria toxin (DT-A) to xenografts derived from LNCaP human prostate cancer cells. This construct regulates toxin expression both at the transcriptional level by the use of a chimeric-modified enhancer/promoter sequence of the human prostate-specific antigen gene and by DNA recombination mediated by Flp recombinase. C32 delivery of the A chain of diphtheria toxin DNA to LNCaP xenografts suppressed tumor growth and even caused 40% of tumors to regress in size. Because C32 transfects tumors locally at high levels, transfects healthy muscle poorly, and displays no toxicity, it may provide a vehicle for the local treatment of cancer.

title: Towards safe, non-viral therapeutic gene expression in humans
abstract: The potential dangers of using viruses to deliver and integrate DNA into host cells in gene therapy have been poignantly highlighted in recent clinical trials. Safer, non-viral gene delivery approaches have been largely ignored in the past because of their inefficient delivery and the resulting transient transgene expression. However, recent advances indicate that efficient, long-term gene expression can be achieved by non-viral means. In particular, integration of DNA can be targeted to specific genomic sites without deleterious consequences and it is possible to maintain transgenes as small episomal plasmids or artificial chromosomes. The application of these approaches to human gene therapy is gradually becoming a reality.

title: Recent advances in rational gene transfer vector design based on poly(ethylene imine) and its derivatives
abstract: The continually increasing wealth of knowledge about the role of genes involved in acquired or hereditary diseases renders the delivery of regulatory genes or nucleic acids into affected cells a potentially promising strategy. Apart from viral vectors, non‐viral gene delivery systems have recently received increasing interest, due to safety concerns associated with insertional mutagenesis of retro‐viral vectors. Especially cationic polymers may be particularly attractive for the delivery of nucleic acids, since they allow a vast synthetic modification of their structure enabling the investigation of structure‐function relationships. Successful clinical application of synthetic polycations for gene delivery will depend primarily on three factors, namely (1) an enhancement of the transfection efficiency, (2) a reduction in toxicity and (3) an ability of the vectors to overcome numerous biological barriers after systemic or local administration. Among the polycations presently used for gene delivery, poly(ethylene imine), PEI, takes a prominent position, due to its potential for endosomal escape. PEI as well as derivatives of PEI currently under investigation for DNA and RNA delivery will be discussed.

title: Low-molecular-weight polyethylenimine as a non-viral vector for DNA delivery: comparison of physicochemical properties, transfection efficiency and in vivo distribution with high-molecular-weight polyethylenimine.
abstract: Low-molecular-weight polyethylenimine (LMW-PEI) was synthesized by the acid-catalyzed, ring-opening polymerization of aziridine and compared with commercially available high-molecular-weight PEI (HMW-PEI) of 25 kDa. Molecular weights were determined by size-exclusion chromatography in combination with multi-angle laser light scattering. The weight average molecular weight (M(w)) of synthesized LMW-PEI was determined as 5.4+/-0.5 kDa, whereas commercial HMW-PEI showed a M(w) of 48+/-2 kDa. DNA polyplexes of LMW-PEI and HMW-PEI were characterized with regard to DNA condensation (ethidium bromide fluorescence quenching), size (photon correlation spectroscopy) and surface charge (laser Doppler anemometry). Compared with HMW-PEI, DNA condensation of LMW-PEI was slightly impaired at lower N/P ratios. Complexes with plasmid DNA at a N/P ratio of 6.7 showed significantly increased hydrodynamic diameters (590+/-140 vs. 160+/-10 nm), while the zeta-potential measurements were similar (23+/-2 vs. 30+/-3 mV). The cytotoxicity of LMW-PEI in L929 fibroblasts was reduced by more than one order of magnitude compared with HMW-PEI, as shown by MTT assay. LMW-PEI exhibited increased transfection efficiency in six different cell lines. Reporter gene expression was found to be increased by a factor of 2.1-110. The pharmacokinetics and biodistribution of 125I-PEI in mice were similar for both molecular weights with an AUC of ca. 330+/-100% ID/ml min. Approximately half of the injected dose accumulated in the liver. LMW-PEI proved to be an efficient gene delivery system in a broad range of cell lines. Due to differences in polyplex structure, as well as its relatively low cytotoxicity, which makes the application of high N/P ratios possible, LMW-PEI appears to possess advantageous qualities with regard to transfection efficiency over PEI of higher molecular weight.

title: A biodegradable low molecular weight polyethylenimine derivative as low toxicity and efficient gene vector.
abstract: Polyethylenimine (PEI) is a class of cationic polymers proven to be effective for gene delivery. However, PEI is nondegradable and the molecular weight of PEI affects the cytotoxicity and gene transfer activity. Aiming to prepare a biodegradable gene vector with high transfection efficiency and low cytotoxicity, we conjugated low molecular weight (LMW) PEIs to the biodegradable backbone polyglutamic acids derivative (PEG-b-PBLG) by aminolysis to form PEIs combined PEG-b-PLG-g-PEIs (GGI). Two copolymers, GGI 30 and GGI 40, were synthesized. The chemistry of GGI was characterized using IR, 1H NMR and 13C NMR, GPC, and CD, respectively. The degradation behaviors of copolymer GGI in papain solution were investigated. GGIs showed good DNA condensation ability and high protection of DNA from nuclease degradation. The zeta potential of the GGI/pDNA polyplexes was approximately 15 mV, and the particle size was in the range 102-138 nm at N/P ratios between 10 and 30. The particle size and the morphology of the polyplex was further confirmed by transmission electron microscope (TEM). In cytotoxicity assay, GGIs were significantly less toxic than PEI 25k. The degradation product of GGI exhibited negligible effects on cells even at high copolymer concentration. The results of GFP flow cytometry and fluorescence imaging showed that the trasnfection efficiencies of GGIs were all markedly higher than PEI 25k in Hela, HepG2, Bel 7402, and 293 cell lines. Importantly, the presence of serum had a lower inhibitive effect on the transfection activity of GGI in comparison to PEI 25k and Lipofectamine 2000. Therefore, PEG-b-PLG-g-PEI copolymers may be attractive cationic polymers for nonviral gene therapy.

title: Efficient gene transfer using reversibly cross-linked low molecular weight polyethylenimine.
abstract: Polyethylenimine (PEI) is a polycation with potential application as a nonviral vector for gene delivery. Here we show that after conjugation with homobifunctional amine reactive reducible cross-linking reagents, low molecular weight polyethylenimine efficiently mediates in vitro gene delivery to Chinese hamster ovary (CHO) cells. Two cross-linking reagents, dithiobis(succinimidylpropionate) (DSP) and dimethyl.3,3'-dithiobispropionimidate*2HCl (DTBP), were utilized based on their reactivity and chemical properties. Both reagents react with primary amines to form reducible cross-links; however, unlike DSP, the DTBP cross-linker maintains net polymer charge through amidine bond formation. PEI with a reported weight-average molecular weight (M(w)) of 800 Da was reacted with either DSP or DTBP at PEI primary amine:cross-link reactive group ratios of 1:1 and 2:1. The transfection efficiencies of the resulting cross-linked products were evaluated in CHO cells using a luciferase reporter gene under a cytomegalovirus (CMV) promoter. Our results show that cross-linked polymers mediate variable levels of transfection depending on the cross-linking reagent, the extent of conjugation, and the N/P ratio. In general, we found conjugate size to be proportional to gene transfer efficiency. Using gel retardation analysis, we also evaluate the capacity of the cross-linked polymers to condense plasmid DNA before and after reduction with 45 mM dithiothreitol (DTT). DTT mediated reduction of intra-cross-link disulfide bonds and inhibited condensation of DNA by conjugates cross-linked with DSP at a ratio of 1:1, but had little effect on the remaining polymers. Analogous intracellular reduction of transfection complexes by reduced glutathione could facilitate uncoupling of PEI from DNA to enhance gene expression.

title: A degradable polyethylenimine derivative with low toxicity for highly efficient gene delivery.
abstract: Routine clinical implementation of human gene therapy awaits safe and efficient gene delivery methods. Polymeric vectors hold promise due to the availability of diverse chemistries, potentially providing targeting, low immunogenicity, nontoxicity, and robustness, but lack sufficient gene delivery efficiency. We have synthesized a versatile group of degradable polycations, through addition of 800-Da polyethylenimine (PEI) to small diacrylate cross-linkers. The degradable polymers reported here are similar in structure, size (14-30 kDa), and DNA-binding properties to commercially available 25-kDa PEI, but mediate gene expression two- to 16-fold more efficiently and are essentially nontoxic. These easily synthesized polymers are some of the most efficient polymeric vectors reported to date and provide a versatile platform for investigation of the effects of polymer structure and degradation rate on gene delivery efficiency.

title: Heparin-conjugated polyethylenimine for gene delivery.
abstract: A major problem when using cationic polymers for gene delivery is that transfection is strongly inhibited by the presence of serum. This shortcoming limits the application of cationic polymers for systematic gene delivery in vivo. Due to the shielding effect of heparin, heparin conjugation to cationic polymers may improve the in vivo gene transfection efficiency. In this study, the transfection efficiency of heparin-conjugated polyethylenimine (HCPEI) with a low molecular weight of 1800 Da was compared to the transfection efficiencies of polyethylenimine with a low molecular weight of 1800 Da (PEI1800), polyethylenimine with a high molecular weight of 25,000 Da (PEI25k), and Lipofectamine. The size of the HCPEI/plasmid DNA (pDNA) complex is approximately 250 nm. HCPEI has a proton-buffering effect and HCPEI/pDNA has higher blood compatibility and a lower cytotoxicity than PEI25k/pDNA and Lipofectamine/pDNA. For in vitro transfection of rabbit smooth muscle cells in serum-free medium, the transfection efficiency of HCPEI/pDNA was not significantly different from those of PEI25k/pDNA and Lipofectamine/pDNA. Importantly, in serum-containing medium, the transfection efficiency of HCPEI/pDNA was significantly higher than those of PEI25k/pDNA and Lipofectamine/pDNA. For vascular endothelial growth factor (VEGF) gene transfection to mouse ischemic limbs, HCPEI/pDNA exhibited significantly higher VEGF expression and more extensive neovascularization than PEI/pDNA and Lipofectamine/pDNA. Taken together, heparin conjugation to PEI improves the in vivo gene transfection efficiency of PEI.

title: Efficient inhibition of C-26 colon carcinoma by VSVMP gene delivered by biodegradable cationic nanogel derived from polyethyleneimine.
abstract: Biodegradable cationic nanoparticles have promising application as a gene delivery system. In this article, heparin-polyethyleneimine (HPEI) nanogels were prepared, and these nanogels were developed as a nonviral gene vector. The transfection efficiency of HPEI nanogels was comparable with that of PEI25K, while the cytotoxicity was lower than that of PEI2K and much lower than that of PEI25K in vitro. These HPEI nanogels also had better blood compatibility than PEI25K. After intravenous administration, HPEI nanogels degraded, and the degradation products were excreted through urine. The plasmid expressing vesicular stomatitis virus matrix protein (pVSVMP) could be efficiently transfected into C-26 colon carcinoma cells by HPEI nanogels in vitro, inhibiting the cell proliferation through apoptosis induction. Intraperitoneal injection of pVSVMP/HPEI complexes efficiently inhibited the abdominal metastases of C-26 colon carcinoma through apoptosis induction (mean tumor weight in mice treated with pVSVMP/HPEI complex = 0.93 g and in control mice = 3.28 g, difference = 2.35 g, 95% confidence interval [CI] = 1.75-2.95 g, P < 0.001) and prolonged the survival of treated mice. Moreover, intravenous application of pVSVMP/HPEI complexes also inhibited the growth of pulmonary metastases of C-26 colon carcinoma through apoptosis induction. The HPEI nanogels delivering pVSVMP have promising application in treating colon carcinoma.

title: Dynamic progression of an intraperitoneal xenograft model of human ovarian cancer and its potential for preclinical trials.
abstract: This study was conducted to establish a feasible intraperitoneal xenograft model in nude mice which mimicked the dynamic progression of human ovarian cancer and to explore its potential for preclinical trials. A human ovarian tumor line SKOV3 was originally injected s.c. to develop tumors; then the tumors were harvested and minced into small particles for i.p. inoculation in three groups of nude mice which would be monitored consecutively. The intraperitoneal carcinomatosis and relevant organs were collected for histopathological dynamic comparison and CA125 immunohistochemical staining 7, 21 and 49 days after inoculation. An additional experiment with cisplatin sensitivity test was performed and tumor tissues were observed for apoptosis-Hoechst assay. The intraperitoneal carcinomatosis had a rapid progression which resulted in extensive dissemination on the peritoneal surfaces and invasion into abdominal lymph nodes, livers, pancreas and spleen. Tumor tissues revealed similar morphological features of primary tumor from which SKOV3 derived and part of in vivo tumor mass was positive for CA125. Cisplatin could significantly inhibit the intraperitoneal carcinomatosis growth. This model may provide a valuable platform to study the biological properties of ovarian cancer as well as to test new therapeutic strategies in preclinical trials.

title: Inhibition of Tumor Growth with a Vaccine Based on Xenogeneic Homologous Fibroblast Growth Factor Receptor-1 in Mice*
abstract: Angiogenesis is important for the growth of solid tumors. The breaking of the immune tolerance against the molecule associated with angiogenesis should be a useful approach for cancer therapy. However, the immunity to self-molecules is difficult to elicit by a vaccine based on autologous or syngeneic molecules due to immune tolerance. Basic fibroblast growth factor (bFGF) is a specific and potent angiogenic factor implicated in tumor growth. The biological activity of bFGF is mediated through interaction with its high-affinity receptor, fibroblast growth factor receptor-1 (FGFR-1). In this study, we selected Xenopus FGFR-1 as a model antigen by the breaking of immune tolerance to explore the feasibility of cancer therapy in murine tumor models. We show here that vaccination with Xenopus FGFR-1 (pxFR1) is effective at antitumor immunity in three murine models. FGFR-1-specific autoantibodies in sera of pxFR1-immunized mice could be found in Western blotting analysis. The purified immunoglobulins were effective at the inhibition of endothelial cell proliferation in vitro and at the antitumor activity in vivo. The antitumor activity and production of FGFR-1-specific autoantibodies could be abrogated by depletion of CD4+ T lymphocytes. Histological examination revealed that the autoantibody was deposited on the endothelial cells within tumor tissues from pxFR1-immunized mice, and intratumoral angiogenesis was significantly suppressed. Furthermore, the inhibition of angiogenesis could also be found in alginate-encapsulate tumor cell assay. These observations may provide a new vaccine strategy for cancer therapy through the induction of autoimmunity against FGFR-1 associated with angiogenesis in a cross-reaction.

title: Toxicity of cationic lipids and cationic polymers in gene delivery.
abstract: Gene therapy, as a promising therapeutics to treat genetic or acquired diseases, has achieved exciting development in the past two decades. Appropriate gene vectors can be crucial for gene transfer. Cationic lipids and polymers, the most important non-viral vectors, have many advantages over viral ones as non-immunogenic, easy to produce and not oncogenic. They hold the promise to replace viral vectors to be used in clinic. However, the toxicity is still an obstacle to the application of non-viral vectors to gene therapy. For overcoming the problem, many new cationic compounds have been developed. This article provides a review with respect to toxicity of cationic lipids and polymers in gene delivery. We evaluate the structural features of cationic compounds and summarize the relationship of toxicity and structure and hope to provide available suggestions on the development of these cationic compounds.

title: Tumour vascular targeting
abstract: It is now accepted that the growth of solid tumours is dependent on their capacity to acquire a blood supply, and much effort has been directed towards the development of agents (known as anti-angiogenics) that disrupt this process. More recently, it has become apparent that targeted destruction of the established tumour vasculature is another avenue for exciting therapeutic opportunities. In this article, we present evidence that vascular targeting is an effective antitumour strategy in animal models, describe strategies for identifying putative tumour vascular targets and discuss future prospects for vascular targeting in the clinic.

title: What is the evidence that tumors are angiogenesis dependent?
abstract: Method of treating a wound or burn which comprises directly dressing its surface with non-woven fabric comprising staple fibers of spun, regenerated collagen substantially free of telopeptides is disclosed.

title: Angiogenesis in cancer and other diseases
abstract: Pathological angiogenesis is a hallmark of cancer and various ischaemic and inflammatory diseases. Concentrated efforts in this area of research are leading to the discovery of a growing number of pro- and anti-angiogenic molecules, some of which are already in clinical trials. The complex interactions among these molecules and how they affect vascular structure and function in different environments are now beginning to be elucidated. This integrated understanding is leading to the development of a number of exciting and bold approaches to treat cancer and other diseases. But owing to several unanswered questions, caution is needed.

title: Role of angiogenesis in tumor growth and metastasis.
abstract: Angiogenesis is required for invasive tumor growth and metastasis and constitutes an important point in the control of cancer progression. Its inhibition may be a valuable new approach to cancer therapy. Avascular tumors are severely restricted in their growth potential because of the lack of a blood supply. For tumors to develop in size and metastatic potential they must make an "angiogenic switch" through perturbing the local balance of proangiogenic and antiangiogenic factors. Frequently, tumors overexpress proangiogenic factors, such as vascular endothelial growth factor, allowing them to make this angiogenic switch. Two strategies used in the development of antiangiogenic agents involve the inhibition of proangiogenic factors (eg, anti-vascular endothelial growth factor monoclonal antibodies) as well as therapy with endogenous inhibitors of angiogenesis, such as endostatin and angiostatin. Therapy with endogenous angiogenic inhibitors such as endostatin and angiostatin may reverse the angiogenic switch preventing growth of tumor vasculature. Preclinical studies have shown that endostatin effectively inhibits tumor growth and shrinks existing tumor blood vessels. Phase 1 clinical trials of endostatin and angiostatin are ongoing, and preliminary results show minimal toxicities.

title: Vascular endothelial growth factor immunoneutralization plus Paclitaxel markedly reduces tumor burden and ascites in athymic mouse model of ovarian cancer.
abstract: Ovarian cancer is characterized by rapid growth of solid intraperitoneal tumors and production of large volumes of ascites. Our previous studies of intraperitoneal ovarian carcinoma in an athymic mouse model demonstrated that a monoclonal antibody (mAb) to human vascular endothelial growth factor (VEGF) could prevent ascites formation. Although ascites was almost completely inhibited, tumor burden was variably reduced. To develop more effective therapy, we assessed the combination of a human VEGF mAb plus paclitaxel. Four groups of female athymic nude mice were inoculated intraperitoneally with OVCAR3 cells. Two weeks after inoculation, one group was treated with a human VEGF mAb intraperitoneally twice weekly plus paclitaxel intraperitoneally three times weekly for 6 weeks. The second group was treated with VEGF mAb alone. The third group was treated with paclitaxel alone. The remaining group was treated with vehicle only. Tumor burden in the VEGF mAb plus paclitaxel and paclitaxel alone groups was reduced by 83.3% and 85.7% and 58.5% and 59.5%, respectively, in two separate experiments, compared to controls. VEGF mAb alone caused no significant decrease in tumor burden, nor did treatment of mice inoculated intraperitoneally with HEY-A8 cells, a non-VEGF-secreting ovarian cell line. Virtually no ascites developed in the combined treatment group or the group treated with VEGF mAb alone. Paclitaxel alone reduced ascites slightly, but not significantly. Morphological studies demonstrated that VEGF immunoneutralization enhanced paclitaxel-induced apoptosis in these human ovarian cancers. Thus, combination therapy with inhibitors of VEGF plus paclitaxel may be an effective way to markedly reduce tumor growth and ascites in ovarian carcinoma.