Improved biological activity of a mutant endostatin containing a single amino-acid substitution

Human endostatin has an internal Asn-Gly-Arg (NGR) motif at position 126-128 following a proline at position 125. Asn-Gly-Arg-containing peptides have been shown to target tumour vasculature and inhibit aminopeptidase N activity. We previously compared the in vitro and in vivo biological activities of native endostatin and endostatin with a proline to alanine mutation (P125A-endostatin). P125A-endostatin exhibited greater inhibition of both endothelial cell proliferation and human ovarian cancer growth compared to native endostatin. Here we explore further the effects on biological activity of the P125A mutation, and show that aminopeptidase N is not involved. To determine whether the increased biological activity of the mutant was due to unmasking of downstream NGR-sequence, effect of endostatin on aminopeptidase N activity was investigated. Neither the native nor the P125A-endostatin inhibited aminopeptidase N. However, synthetic peptides consisting of the S118-T131 region of endostatin inhibited aminopeptidase N. These results suggest that the internal NGR site in native or mutant endostatin is not accessible to aminopeptidase N, and that this activity is not involved in the enhanced biological activity of the P125A form. P125A-endostatin bound to endothelial cells more efficiently than native endostatin and exhibited greater inhibition of not only proliferation but also migration of endothelial cells. P125A-endostatin also localised into tumour tissue to a higher degree than the native protein, and displayed greater inhibition of growth of colon cancer in athymic mice. Both proteins inhibited tumour cell-induced angiogenesis effectively. Real-time PCR analysis showed that both native and P125A-endostatin decreased expression of key proangiogenic growth factors. Vascular endothelial growth factor and angiopoietin 1 were downregulated more by the mutant. These studies suggest that the region around P125 can be modified to improve the biological activity of endostatin.     

Inhibition of ovarian cancer by RGD-P125A-endostatin-Fc fusion proteins

Previous studies have shown that a single point mutation in endostatin at position 125 (P125A) can improve the biological activity of endostatin. Addition of an integrin-targeting moiety, R-G-D, resulted in better localization to tumor vasculature and improved the antiangiogenic activity of endostatin. Because endostatin has relatively shorter serum half-life, frequent dosing was required for inhibiting tumor growth. In our study, we have genetically fused RGD-P125A-endostatin to Fc of IgG4 isotype and evaluated its antiangiogenic and antitumor effects in athymic mice. Two genetic constructs were made, RGD-P125A-endostatin-Fc (RE-Fc) and P125A-endostatin-RGD-Fc (ER-Fc). Both constructs were cloned and expressed in mammalian cells. Purified fusion proteins inhibited endothelial cell migration and proliferation better than yeast-derived P125A-endostatin. Both RE-Fc and ER-Fc inhibited ovarian cancer growth and were found to be as effective as Bevacizumab treatment. Fusion protein showed marked increased half-life. Combination treatment with Bevacizumab and ER-Fc showed additive inhibition of ovarian cancer growth. These studies demonstrate that genetic fusion with human IgG4-Fc increases the half-life of P125A-endostatin and can be used along with Bevacizumab to improve antiangiogenic and antitumor activities.     

Addition of integrin binding sequence to a mutant human endostatin improves inhibition of tumor growth

Tumor vasculatures express high levels of alphaVbeta3/alphaVbeta5 and alpha5beta1 integrins. Consequently, peptides containing the RGD (Arg-Gly-Asp) sequence, which is present in ligands of integrins, is effective in targeting therapeutic reagents to tumor vascular endothelium. In our study, we investigated whether the biologic activity of endostatin can be enhanced by the addition of an integrin targeting sequence. RGD sequence was added to either the amino or carboxyl terminus of endostatin containing a point mutation, P125A-endostatin. Earlier we have shown that the P125A mutation did not affect the biologic activity of endostatin but in fact had better antiangiogenic activity when compared to the native molecule. Further modification of P125A-endostatin with the RGD motif showed specific and increased binding to endothelial cells, and the increased binding coincided with improved antiangiogenic properties. Both amino and carboxyl terminal RGD-modification of P125A-endostatin resulted in greater inhibition of endothelial cell migration and proliferation. RGD modification increased tumor localization without affecting the circulatory half-life of P125A-endostatin, and RGD-modified P125A-endostatin was found to be more effective when compared to the P125A-endostatin in inhibiting ovarian and colon cancer growth in athymic mice. Complete inhibition of ovarian tumor growth was observed when P125A-endostatin-RGD was encapsulated into alginate beads. These studies demonstrate that addition of a vascular targeting sequence can enhance the biologic activity of an antiangiogenic molecule.     

Endostatin binding to ovarian cancer cells inhibits peritoneal attachment and dissemination

Ovarian cancer cells use integrins to attach to the peritoneal wall. Integrin alpha(5)beta(1) is also the target for the angiogenesis inhibitor, endostatin. Therefore, the ability of endostatin to competitively inhibit tumor cell seeding of the peritoneum was investigated. An imaging method was developed to determine early phases of peritoneal dissemination of ovarian cancer cells. Using this method, endostatin was found to bind ovarian cancer cells through integrin alpha(5)beta(1) and inhibit vessel cooption efficiently. Although both angiostatin and endostatin are potent inhibitors of tumor angiogenesis, peritoneal attachment and vessel cooption was blocked only by the endostatin. Knocking down the expression of integrins alpha(5) and beta(1) in ovarian cancer cells interfered with endostatin-mediated inhibition of peritoneal seeding. Furthermore, adenovirus-mediated in situ expression of endostatin either inside the peritoneum or by the ovarian tumor cells inhibited peritoneal seeding and dissemination in vivo. Endostatin treatment also prevented primary ovarian cancer cells from attaching to mouse peritoneal wall. These studies show a paraendothelial mechanism by which endostatin can inhibit peritoneal dissemination of ovarian cancer cells and raises the possibility of intraperitoneal expression of endostatin to reduce recurrence.     

Indoleamine 2,3-dioxygenase promotes peritoneal dissemination of ovarian cancer through inhibition of natural killercell function and angiogenesis promotion

The purpose of this study was to clarify the relationship between ovarian cancer peritoneal dissemination and indoleamine 2,3-dioxygenase (IDO) expression, and to explore the possibility of IDO-targeting molecular therapy for ovarian cancer. We transfected an IDO expression vector into the IDO-non-expressing human ovarian cancer cell line OMC-1, and established an IDO-expressing cell line (OMC-1/IDO) to examine the relationship between IDO expression and cancer cell growth in vitro and in vivo. IDO expression did not influence cancer cell growth and invasion in vitro, but promoted tumor growth and peritoneal dissemination in vivo. Immunostaining showed that IDO expression inhibited natural killer (NK) cell accumulation in tumors and promoted tumor angiogenesis. In addition, the oral administration of the IDO inhibitor 1-methly-tryptophan inhibited the growth of OMC-1/IDO-derived subcutaneous tumors in mice. These findings indicate that IDO promotes the peritoneal dissemination of ovarian cancer by inhibiting NK cell accumulation in tumors and promoting angiogenesis, supporting the applicability of IDO-targeting molecular therapy in ovarian cancer.     

Binding of endostatin to human ovarian cancer cells inhibits cell attachment

Endostatin, a C-terminal fragment of collagen type XVIII, is one of the well-characterized endogenous inhibitors of angiogenesis. Endostatin is known to bind integrin alpha(5)beta(1), which is upregulated on tumor endothelium. Most of the ovarian cancer cells express significant amounts of alpha(5)beta(1) integrin, which is important for ovarian cancer cells to attach to the peritoneal wall. Therefore we investigated whether endostatin could directly bind ovarian cancer cells and inhibit tumor cell attachment to extracellular matrix. Binding of endostatin to ovarian cancer cells was characterized by preincubation with function blocking antibodies to integrin subunits. These studies showed that ovarian cancer cell attachment to fibronectin-coated wells can be inhibited by alpha(5)beta(1) integrin specific antibodies as well as endostatin. Downregulation of integrin alpha(5) and beta(1) by siRNA abrogated the binding of OVCAR5 and human umbilical vein endothelial cell to endostatin. Although endostatin treatment did not affect ovarian cancer cell migration, treated cells failed to attach mouse peritoneal wall preparations. These studies suggest an extra-antiangiogenic role for endostatin, which can be used prevent peritoneal attachment and dissemination of ovarian cancer cells.     

Recombinant adeno-associated virus 2-mediated antiangiogenic prevention in a mouse model of intraperitoneal ovarian cancer.

PURPOSE: In the present study, we sought to determine the potential of sustained transgene expression by a single i.m. administration of recombinant adeno-associated virus 2 (rAAV) encoding angiostatin and endostatin in inhibiting i.p. ovarian cancer growth and dissemination in a preclinical mouse model. EXPERIMENTAL DESIGN: Cohorts of female athymic nude mice received either no virus or 1.2 x 10(11) particles of rAAV encoding green fluorescence protein or endostatin plus angiostatin, i.m. Three weeks later, the mice were i.p. injected with 10(6) human epithelial ovarian cancer cell line SKOV3.ip1. As a measure of effectiveness of the therapy, tumor weight, abdominal distension, ascites volume and vascular endothelial growth factor level, and tumor weight were determined. Immunohistochemistry was done to determine tumor cell apoptosis and endothelial cell proliferation following the therapy. Tumor-free survival was recorded as the end point. RESULTS: Results indicated a significant tumor-free survival (P < 0.003) following therapy with rAAV encoding endostatin and angiostatin compared with untreated or rAAV-green fluorescence protein-treated mice. Ascites volume in rAAV endostatin and angiostatin-treated mice was significantly lower than naive mice and contained less hemorrhage and tumor conglomerates. The level of vascular endothelial growth factor in the ascites of antiangiogenic vector treated mice was also significantly less compared with the untreated mice. Immunohistochemical analyses indicated increased tumor cell apoptosis and decreased blood vasculature following rAAV endostatin and angiostatin treatment. CONCLUSION: The results indicate that antiangiogenic genetic prevention from stable systemic levels of angiostatin and endostatin by i.m. administration of rAAV can be used for the treatment of i.p. ovarian cancer growth and dissemination.     

Adeno-associated viral vector-mediated expression of endostatin inhibits tumor growth and metastasis in an orthotropic pancreatic cancer model in hamsters

We examined the feasibility of using adeno-associated virus (AAV)-mediated systemic delivery of endostatin in gene therapy to treat metastasis of pancreatic cancer. We established an animal model of orthotopic metastatic pancreatic cancer in which the pancreatic cancer cell line PGHAM-1 was inoculated into the pancreas of Syrian golden hamsters. Transplanted cells proliferated rapidly and metastasized to the liver. An AAV vector expressing endostatin (5 x 10(10) particles) was injected intramuscularly into the left quadriceps or intravenously into the portal vein. These routes of vector administration were evaluated by comparing various parameters of tumor development. Intramuscular injection of the vector modestly increased the serum endostatin level. The numbers of metastases and the incidence of hemorrhagic ascites were decreased in the treated animals. In contrast, the serum concentration of endostatin was significantly increased after intraportal injection of the vector. The antitumor effects on all parameters (including the size and microvessel density of primary pancreatic tumors, the sizes and number of liver metastases, and the incidence of hemorrhagic ascites) were significant. These results suggest that systemic delivery of endostatin represents a potentially effective treatment for pancreatic cancer and liver metastases. The route of vector administration influences the efficacy of AAV-mediated endostatin expression. Intraportal injection of the AAV vector appears to be more effective as an antiangiogenic gene therapy for pancreatic cancer.     

Expression of Vascular Endothelial Growth Factor and E-Cadherin in Human Ovarian Cancer: Association with Ascites Fluid Accumulation and Peritoneal Dissemination in Mouse Ascites Model

Ascites formation and peritoneal dissemination are critical problems in patients with advanced ovarian cancer. Vascular endothelial growth factor (VEGF), also known as angiogenic growth factor, is a potent mediator of peritoneal fluid accumulation and angiogenesis of tumors. E-Cadherin is an adhesion molecule that is important for cell-to-cell interaction. To elucidate the molecular mechanism of ascites formation and peritoneal dissemination of ovarian cancer, we examined the expression of VEGF and E-cadherin in different ovarian cancer cell lines and utilized nude mice to compare the biological characteristics of ovarian cancer cells. Three human ovarian cancer cell lines (AMOC-2, HNOA and HTBOA) were used in this study. Expression of genes was analyzed by northern blotting and RT-PCR methods. AMOC-2 expressed E-cadherin, but not VEGF. HNOA expressed VEGF without E-cadherin expression. HTBOA expressed both VEGF and E-cadherin. Each human ovarian cancer model revealed a specific feature. The AMOC-2 mouse had a single large peritoneal tumor without ascites or remarkable peritoneal dissemination. HTBOA and HNOA mice had bloody ascites and marked peritoneal dissemination. Introduction of VEGF antisense into HTBOA cells could inhibit the ascites formation. It is suggested that VEGF is important for the ascites formation via the increased vascular permeability effect. The deregulation of E-cadherin expression might be involved in the peritoneal dissemination. These molecules are important for the formation of specific features of advanced ovarian cancer. Ovarian cancer cell lines that had different gene expression patterns produced nude mouse human ovarian cancer models with different characteristics.     

Expression of vascular endothelial growth factor and E-cadherin in human ovarian cancer: association with ascites fluid accumulation and peritoneal dissemination in mouse ascites model.

Ascites formation and peritoneal dissemination are critical problems in patients with advanced ovarian cancer. Vascular endothelial growth factor (VEGF), also known as angiogenic growth factor, is a potent mediator of peritoneal fluid accumulation and angiogenesis of tumors. E-Cadherin is an adhesion molecule that is important for cell-to-cell interaction. To elucidate the molecular mechanism of ascites formation and peritoneal dissemination of ovarian cancer, we examined the expression of VEGF and E-cadherin in different ovarian cancer cell lines and utilized nude mice to compare the biological characteristics of ovarian cancer cells. Three human ovarian cancer cell lines (AMOC-2, HNOA and HTBOA) were used in this study. Expression of genes was analyzed by northern blotting and RT-PCR methods. AMOC-2 expressed E-cadherin, but not VEGF. HNOA expressed VEGF without E-cadherin expression. HTBOA expressed both VEGF and E-cadherin. Each human ovarian cancer model revealed a specific feature. The AMOC-2 mouse had a single large peritoneal tumor without ascites or remarkable peritoneal dissemination. HTBOA and HNOA mice had bloody ascites and marked peritoneal dissemination. Introduction of VEGF antisense into HTBOA cells could inhibit the ascites formation. It is suggested that VEGF is important for the ascites formation via the increased vascular permeability effect. The deregulation of E-cadherin expression might be involved in the peritoneal dissemination. These molecules are important for the formation of specific features of advanced ovarian cancer. Ovarian cancer cell lines that had different gene expression patterns produced nude mouse human ovarian cancer models with different characteristics.     

Suppression of cell migration in ovarian cancer cells mediated by PTEN overexpression

Peritoneal dissemination is the major progression pathway of ovarian cancer, and its control is important for improvement of the prognosis. PTEN is a tumor suppressor gene, and is known to inhibit cancer cell growth and migration. To investigate the possibility of gene therapy using PTEN for ovarian cancer, we introduced PTEN cDNA into an ovarian cancer cell line HRA carrying wild-type PTEN, and examined the effects in vitro and in vivo. Using PTEN cDNA cloned from a human liver cDNA library, a PTEN expression vector was constructed. This vector was introduced into HRA cells by the standard calcium phosphate precipitation method, and an HRA cell line overexpressing PTEN (HRA/PTEN) was established. On the cell migration test by in vitro scratch wound healing assay, the number of migrating cells was 6.3+/-0.9 cells/mm(2) in HRA/PTEN, which was significantly smaller than that in the control (39.7+/-3.2 cells/mm(2)) (p<0.01). No significant differences were observed in the in vitro cell growth or in vivo tumor growth between HRA/PTEN and the control. The findings described above, show that enhanced expression of PTEN inhibits ovarian cancer cell migration, suggesting that gene therapy approaches using PTEN for control of peritoneal dissemination of ovarian cancer are possible.     

Cooperative effect of adenoviral p53 gene therapy and standard chemotherapy in ovarian cancer cells independent of the endogenous p53 status

Clinical adenoviral p53 gene therapy has been shown by us and others to inhibit tumor growth of ovarian cancer with endogenous mutant p53. This study was designed to test the cooperative antitumor effect of standard combination chemotherapy using paclitaxel and carboplatin together with adenoviral p53 gene transfer in the presence of wild-type and mutant p53. Seven ovarian cancer cell lines with mutant p53 and seven ovarian cancer cell lines with wild-type p53 were tested. An E1-deleted adenovirus type 5 expressing p53 (ACNp53) was used for p53 gene transfer. p53 gene transfer at 50% transduction efficiency significantly reduced IC50 of carboplatin chemotherapy up to 49-fold, of paclitaxel chemotherapy up to six-fold, and of paclitaxel/carboplatin chemotherapy up to 19-fold in the wild-type p53 cell line OV-MZ-5. Synergism between ACNp53 and chemotherapy calculated by median-effect analysis was found at low drug concentrations in all cell lines independent of the p53 mutational status. In conclusion, adenoviral p53 gene transfer significantly increased the sensitivity of ovarian tumor cells to paclitaxel, to carboplatin and/or to the combination of both.     

Adenovirus-mediated calponin h1 gene therapy directed against peritoneal dissemination of ovarian cancer: bifunctional therapeutic effects on peritoneal cell layer and cancer cells.

PURPOSE: Calponin h1 (CNh1), one of the family of actin-binding proteins, stabilizes the filaments of actin and modulates various cellular biological phenotypes. Recent studies revealed the close correlation between the invasive tumor spread and the reduced expression of CNh1 and alpha-smooth muscle actin in the surrounding stromal cells. The purpose of this study is to evaluate the efficacy of i.p. CNh1 gene therapy against peritoneal dissemination of ovarian cancer. EXPERIMENTAL DESIGN: We used an adenoviral vector to induce the CNh1 gene into peritoneal cells and ovarian cancer cells as a means of enhancing or inducing the expression of alpha-smooth muscle actin as well as CNh1. The efficacy of gene transfer was examined by in vitro cell culture and in vivo animal experiments. RESULTS: The formation of longer and thicker actin fibers was observed in each transfected cell line, and the localization of these fibers coincided with that of externally transducted CNh1. With respect to changes in cell behavior, the CNh1-transfected peritoneal cells acquired an ability to resist ovarian cancer-induced shrinkage in cell shape; thus, cancer cell invasion through the monolayer of peritoneal cells was inhibited. In addition, CNh1-transfected ovarian cancer cells showed suppressed anchorage-independent growth and invasiveness, the latter of which accompanied impaired cell motility. The concomitant CNh1 transfection into both peritoneal cells and ovarian cancer cells produced an additive inhibitory effect with respect to cancer cell invasion through the peritoneal cell monolayer. By in vivo experiments designed to treat nude mice that had been i.p. inoculated with ovarian cancer cells, we found that the i.p. injected CNh1 adenovirus successfully blocked cancer-induced morphologic changes in peritoneal cell surface and significantly prolonged the survival time of tumor-bearing mice. Moreover, CNh1 adenovirus could successfully enhance the therapeutic effect of an anticancer drug without increase in side effects. CONCLUSIONS: Thus, CNh1 gene therapy against peritoneal dissemination of ovarian cancer is bifunctionally effective (i.e., through inhibitory effects on the infected peritoneal cell layers that suppress cancer invasion and through direct antitumor effects against invasion and growth properties of cancer cells).     

A case of advanced ovarian clear cell adenocarcinoma responding to cisplatin-cyclophosphamide and paclitaxel-carboplatin]

We report a case of stage IV ovarian clear cell adenocarcinoma successfully controlled by a combination of cisplatin-cyclophosphamide (CP) and paclitaxel-carboplatin (TJ). A 64-year-old female with advanced ovarian cancer and pleural effusion underwent 4 courses of combination chemotherapy with CP. The giant ovarian tumor showed a relative reduction in size and the pleural effusion disappeared. Serum CA-125 levels and CA 19-9 levels markedly decreased. Thus, the patient underwent a total hysterectomy and bilateral salphingoophorectomy. During the operation, a giant ovarian clear cell adenocarcinoma was found, but there was no peritoneal dissemination and no cancer cells in her peritoneal fluid. Thereafter, she underwent 3 courses of combination chemotherapy with TJ. She has had 13 months of stable, tumor-free survival since the operation and normal serum CA-125 and CA 19-9 levels. Ovarian clear cell adenocarcinoma generally responds poorly to cisplatin and carboplatin, but in combination chemotherapy with paclitaxel-carboplatin these may be effective.     

Screening of novel biomarkers for the detection of intraperitoneally disseminated cancer cells using human cDNA microarray

In this study, we performed a global analysis of the differential gene expression of a gastric cancer cell line established from a primary main tumor (SNU-1) and that of other cell lines established from the metastasis to the peritoneal cavity (KATO-III, SNU-5, SNU-719, MKN45P, HS39). The application of a high-density cDNA microarray method made it possible to analyze the expression of approximately 21,168 genes. Our examinations of KATO-III, SNU-5, SNU-719, MKN45P, and HS39 showed that several genes were up-regulated in addition to expression of sequence tags (ESTs). The analysis revealed altered up-regulation of CD44 (cell adhesion), CEA, 14-3-3, Ubiquitin A and several kinds of ESTs in gastric cancer cells from malignant ascites. We then analyzed these gastric cancer cell lines with Northern blots and observed preferential up-regulation of these selected genes in cells prone to peritoneal dissemination. RT-PCR confirmed that several genes selected by DNA microarray were also overexpressed in clinical samples of malignant ascites. It is therefore considered that these genes may be related to the peritoneal dissemination of gastric cancers. The results of this global gene expression analysis of gastric cancer cells with peritoneal dissemination promise to provide new insights into the study of human gastric cancer peritoneal dissemination.     

Ovarian epithelial cell lineage-specific gene expression using the promoter of a retrovirus-like element

We have isolated 462 bp of sequence termed ovarian-specific promoter 1 (OSP-1) that is part of a retrovirus-like element specifically expressed in the rat ovary. We have evaluated the ability of OSP-1 to activate gene expression in normal and neoplastic cell lines derived from the ovaries of rats and women. We have found that there was marked specificity in the ability of OSP-1 to drive reporter gene expression in an ovarian epithelial cell lineage manner. The expression of herpes simplex virus thymidine kinase (HSV-TK) under OSP-1 control was sufficiently ovarian cancer cell line specific to render ganciclovir approximately 50-fold more toxic in the A2780 human ovarian cancer cell line compared with clones of the HCT-116 and HT-29 colon cancer cell lines. Furthermore, ganciclovir had marked antitumor efficacy in vivo in severe combined immunodeficient mice bearing A2780OSP-1-HSV-TK as a s.c. xenograft. We suggest that these data support the use of OSP-1 as a tool to provide specificity to the gene therapy of ovarian cancer and to drive ovarian-specific oncogene expression for the creation of transgenic mouse models of ovarian cancer.     

Suppression of tumor growth in human gastric cancer with HER2 overexpression by an anti-HER2 antibody in a murine model

New modalities are necessary for the treatment of patients with unresectable gastric cancer. The aim of this study was to investigate whether or not anti-HER2 antibody could suppress the growth of human gastric cancer cells with HER2 overexpression in vitro and in vivo. Four human gastric cancer cell lines, NCI-N87, MKN-45P, Kato-III, and MKN-1, were used in this study. The suppression of cell proliferation in vitro and of subcutaneous tumor growth in a nude mouse model after treatment with trastuzumab was examined. The expression of HER2 protein was investigated by Western blot analysis. The effect of trastuzumab on the survival rate of nude mice with peritoneal dissemination was examined. Trastuzumab significantly reduced proliferative activity in NCI-N87, a HER2-overexpressing human gastric cancer cell line, in vitro. In the nude mouse model with transplanted subcutaneous tumor, trastuzumab significantly suppressed the tumor growth of NCI-N87 cells, and then HER2 expression was reduced. Trastuzumab improved the survival rate of mice with peritoneal dissemination of MKN-45P cells. Trastuzumab therapy is a potential candidate for a novel treatment of HER2-overexpressing gastric cancer.     

Suppression of bladder cancer growth in mice by adeno-associated virus vector-mediated endostatin expression

Novel treatment strategies such as gene therapy are warranted in view of the failure of current treatment approaches to cure a high percentage of patients with advanced bladder cancers. Testing of the hypothesis that blocking the angiogenic switch may keep tumour growth in check has been facilitated by the discovery of endogenous inhibitors of angiogenesis and has also added another research dimension to the field of cancer gene therapy. Consequently, the concept of targeting the tumour vasculature with anti-angiogenic agents has emerged as an attractive new strategy in the treatment of cancer. Targeted biological therapies that selectively interfere with tumour angiogenesis could improve survival among patients with bladder cancer. Endostatin is a tumour-derived angiogenesis inhibitor and is the first endogenous inhibitor of angiogenesis to be indentified in a matrix protein. Gene therapy represents an attractive approach to treat cancers and other chronic diseases. The development of an effective delivery system is absolutely critical to the usefulness and safety of gene therapy. At present, the adeno-associated virus (AAV) vector has the most promising potential in view of its non-pathogenicity, wide tropisms and long-term transgene expression in vivo. Gene therapy studies using different serotypes of recombinant AAV (rAAV) as delivery vehicles have proved rAAVs to be an effective modality of cancer gene therapy. In the present study, an IgG fragment was inserted at the start of the sequence coding for endostatin with the aim of enabling continuous secretion of endostatin the serum. We also investigated the suppression effect of AAV-mediated endostatin expression on endothelial cells and in mice xenograft models of bladder cancer. Our data demonstrates that rAAV-endostatin controlled tumour cell growth and achieves strong anti-tumour efficacy in vivo.     

Indoleamine-2,3-dioxygenase, an immunosuppressive enzyme that inhibits natural killer cell function, as a useful target for ovarian cancer therapy

This study examined the role of the immuno-suppressive enzyme indoleamine-2,3-dioxygenase (IDO) in ovarian cancer progression, and the possible application of this enzyme as a target for ovarian cancer therapy. We transfected a short hairpin RNA vector targeting IDO into the human ovarian cancer cell line SKOV-3, that constitutively expresses IDO and established an IDO downregulated cell line (SKOV-3/shIDO) to determine whether inhibition of IDO mediates the progression of ovarian cancer. IDO downregulation suppressed tumor growth and peritoneal dissemination in vivo, without influencing cancer cell growth. Moreover, IDO downregulation enhanced the sensitivity of cancer cells to natural killer (NK) cells in vitro, and promoted NK cell accumulation in the tumor stroma in vivo. These findings indicate that downregulation of IDO controls ovarian cancer progression by activating NK cells, suggesting IDO targeting as a potential therapy for ovarian cancer.