Prostate-restricted replicative adenovirus expressing human endostatin-angiostatin fusion gene exhibiting dramatic antitumor efficacy

Oncolytic viruses and pancreatic cancer

BACKGROUND

Today, the pancreatic cancer prognosis is poor and genetic technology is developing to treat various types of cancers. Scientists are actively looking for a new technique to design a therapeutic strategy to treat pancreatic cancer. Several oncolytic viruses are known to be valuable tools for pancreatic cancer treatment. Recent Studies demonstrate their effectiveness and safety in various administration routes such as direct intratumoral, intracutaneous, intravascular, and other routes.

METHOD

In this study, all studies conducted in the past 20 years have been reviewed. Reputable scientific databases including Irandoc, Scopus, Google Scholar and PubMed, are searched for the keywords of Pancreatic cancer, oncolytic, viruses and treatment and the latest information about them is obtained.

RESULTS

Engineering the oncolytic viruses' genome and insertion of intended transgenes including cytokines or shRNAs, has caused promising promotions in pancreatic cancer treatment. Some oncolytic viruses inhibit tumors directly and some through activation of immune responses.

CONCLUSION

This approach showed some signs of success in efficiency like immune system activation in the tumor environment, effective virus targeting in the tumor cells by systemic administration, and enhanced patient survival in comparison with the control group. But of course, until now, using these oncolytic viruses alone has not been effective in elimination of tumors.

Improving adenoviral vectors and strategies for prostate cancer gene therapy

Gene therapy has been evaluated for the treatment of prostate cancer and includes the application of adenoviral vectors encoding a suicide gene or oncolytic adenoviruses that may be armed with a functional transgene. In parallel, versions of adenoviral vector expressing the p53 gene (Ad-p53) have been tested as treatments for head and neck squamous cell carcinoma and non-small cell lung cancer. Although Ad-p53 gene therapy has yielded some interesting results when applied to prostate cancer, it has not been widely explored, perhaps due to current limitations of the approach. To achieve better functionality, improvements in the gene transfer system and the therapeutic regimen may be required. We have developed adenoviral vectors whose transgene expression is controlled by a p53-responsive promoter, which creates a positive feedback mechanism when used to drive the expression of p53. Together with improvements that permit efficient transduction, this new approach was more effective than the use of traditional versions of Ad-p53 in killing prostate cancer cell lines and inhibiting tumor progression. Even so, gene therapy is not expected to replace traditional chemotherapy but should complement the standard of care. In fact, chemotherapy has been shown to assist in viral transduction and transgene expression. The cooperation between gene therapy and chemotherapy is expected to effectively kill tumor cells while permitting the use of reduced chemotherapy drug concentrations and, thus, lowering side effects. Therefore, the combination of gene therapy and chemotherapy may prove essential for the success of both approaches.

Tumor angiogenesis and anti-angiogenic gene therapy for cancer

When Folkman first suggested a theory about the association between angiogenesis and tumor growth in 1971, the hypothesis of targeting angiogenesis to treat cancer was formed. Since then, various studies conducted across the world have additionally confirmed the theory of Folkman, and numerous efforts have been made to explore the possibilities of curing cancer by targeting angiogenesis. Among them, anti-angiogenic gene therapy has received attention due to its apparent advantages. Although specific problems remain prior to cancer being fully curable using anti-angiogenic gene therapy, several methods have been explored, and progress has been made in pre-clinical and clinical settings over previous decades. The present review aimed to provide up-to-date information concerning tumor angiogenesis and gene delivery systems in anti-angiogenic gene therapy, with a focus on recent developments in the study and application of the most commonly studied and newly identified anti-angiogenic candidates for anti-angiogenesis gene therapy, including interleukin-12, angiostatin, endostatin, tumstatin, anti-angiogenic metargidin peptide and endoglin silencing.

Ad5/35E1aPSESE4: A novel approach to marking circulating prostate tumor cells with a replication competent adenovirus controlled by PSA/PSMA transcription regulatory elements

Circulating tumor cells serve as useful biomarkers with which to identify disease status associated with survival, metastasis and drug sensitivity. Here, we established a novel application for detecting PSA/PSMA-positive prostate cancer cells circulating in peripheral blood employing an adenovirus called Ad5/35E1aPSESE4. Ad5/35E1aPSESE4 utilized PSES, a chimeric enhancer derived from PSA/PSMA promoters that is highly active with and without androgen. A fluorescence signal mediated by GFP expression upon Ad5/35E1aPSESE4 infection was selectively amplified in PSA/PSMA-positive prostate cancer cells in vitro and ex vivo. Furthermore, for the in vivo model, blood drawn from TRAMP was tested for CTCs with Ad5/35E1aPSESE4 infection and was positive for CTCs at week 16. Validation was performed on patient blood at various clinical stages and found out 1-100 CTCs expressing GFP upon Ad5/35E1aPSESE4 infection. Interestingly, CTC from one patient was confirmed to be sensitive to docetaxel chemotherapeutic reagent and to abundantly express metastasis-related genes like MMP9, Cofilin1, and FCER1G through RNA-seq. Our study established that the usage of Ad5/35E1aPSESE4 is effective in marking PSA/PSMA-positive prostate cancer cells in patient blood to improve the efficacy of utilizing CTCs as a biomarker.

Lovastatin enhances adenovirus-mediated TRAIL induced apoptosis by depleting cholesterol of lipid rafts and affecting CAR and death receptor expression of prostate cancer cells

Oncolytic adenovirus and apoptosis inducer TRAIL are promising cancer therapies. Their antitumor efficacy, when used as single agents, is limited. Oncolytic adenoviruses have low infection activity, and cancer cells develop resistance to TRAIL-induced apoptosis. Here, we explored combining prostate-restricted replication competent adenovirus-mediated TRAIL (PRRA-TRAIL) with lovastatin, a commonly used cholesterol-lowering drug, as a potential therapy for advanced prostate cancer (PCa). Lovastatin significantly enhanced the efficacy of PRRA-TRAIL by promoting the in vivo tumor suppression, and the in vitro cell killing and apoptosis induction, via integration of multiple molecular mechanisms. Lovastatin enhanced PRRA replication and virus-delivered transgene expression by increasing the expression levels of CAR and integrins, which are critical for adenovirus 5 binding and internalization. Lovastatin enhanced TRAIL-induced apoptosis by increasing death receptor DR4 expression. These multiple effects of lovastatin on CAR, integrins and DR4 expression were closely associated with cholesterol-depletion in lipid rafts. These studies, for the first time, show correlations between cholesterol/lipid rafts, oncolytic adenovirus infection efficiency and the antitumor efficacy of TRAIL at the cellular level. This work enhances our understanding of the molecular mechanisms that support use of lovastatin, in combination with PRRA-TRAIL, as a candidate strategy to treat human refractory prostate cancer in the future.

Targeting tumor vasculature through oncolytic virotherapy: recent advances

The oncolytic virotherapy field has made significant advances in the last decade, with a rapidly increasing number of early- and late-stage clinical trials, some of them showing safety and promising therapeutic efficacy. Targeting tumor vasculature by oncolytic viruses (OVs) is an attractive strategy that offers several advantages over nontargeted viruses, including improved tumor viral entry, direct antivascular effects, and enhanced antitumor efficacy. Current understanding of the biological mechanisms of tumor neovascularization, novel vascular targets, and mechanisms of resistance has allowed the development of oncolytic viral vectors designed to target tumor neovessels. While some OVs (such as vaccinia and vesicular stomatitis virus) can intrinsically target tumor vasculature and induce vascular disruption, the majority of reported vascular-targeted viruses are the result of genetic manipulation of their viral genomes. Such strategies include transcriptional or transductional endothelial targeting, "armed" viruses able to downregulate angiogenic factors, or to express antiangiogenic molecules. The above strategies have shown preclinical safety and improved antitumor efficacy, either alone, or in combination with standard or targeted agents. This review focuses on the recent efforts toward the development of vascular-targeted OVs for cancer treatment and provides a translational/clinical perspective into the future development of new generation biological agents for human cancers.

Development of replication-competent adenovirus for bladder cancer by controlling adenovirus E1a and E4 gene expression with the survivin promoter

Survivin is a member of the inhibitors of apoptosis protein family. Here, we examined survivin expression and confirmed abundant survivin expression in bladder cancer cells. This expression pattern indicated that the transcriptional regulatory elements that control survivin expression could be utilized to discriminate cancer from normal cells. We therefore generated a novel adenovirus termed Ad5/35E1apsurvivinE4 with the following characteristics: 1) E1A and E4 protein expression was dependent on survivin promoter activity; 2) the green fluorescence protein gene was inserted into the genome under the control of the CMV promoter; 3) most of the E3 sequences were deleted, but the construct was still capable of expressing the adenovirus death protein with potent cytotoxic effects; and 4) the fiber knob was from serotype 35 adenovirus. As expected from the abundant survivin expression observed in bladder cancer cells, Ad5/35E1apsurvivinE4 replicated better in cancer cells than in normal cells by a factor of 10⁶ to 10². Likewise, Ad5/35E1apsurvivinE4 exerted greater cytotoxic effects on all bladder cancer cell lines tested. Importantly, Ad5/35E1apsurvivinE4 inhibited the growth of Ku7-Luc orthotopic xenografts in nude mice. Taken together, Ad5/35E1apsurvivinE4 indicates that the survivin promoter may be utilized for the development of a replication-competent adenovirus to target bladder cancers.

Treatment of medulloblastoma with oncolytic measles viruses expressing the angiogenesis inhibitors endostatin and angiostatin

Background

Medulloblastoma is the most common type of pediatric brain tumor. Although numerous factors influence patient survival rates, more than 30% of all cases will ultimately be refractory to conventional therapies. Current standards of care are also associated with significant morbidities, giving impetus for the development of new treatments. We have previously shown that oncolytic measles virotherapy is effective against medulloblastoma, leading to significant prolongation of survival and even cures in mouse xenograft models of localized and metastatic disease. Because medulloblastomas are known to be highly vascularized tumors, we reasoned that the addition of angiogenesis inhibitors could further enhance the efficacy of oncolytic measles virotherapy. Toward this end, we have engineered an oncolytic measles virus that express a fusion protein of endostatin and angiostatin, two endogenous and potent inhibitors of angiogenesis.

Methods

Oncolytic measles viruses encoding human and mouse variants of a secretable endostatin/angiostatin fusion protein were designed and rescued according to established protocols. These viruses, known as MV-hE:A and MV-mE:A respectively, were then evaluated for their anti-angiogenic potential and efficacy against medulloblastoma cell lines and orthotopic mouse models of localized disease.

Results

Medulloblastoma cells infected by MV-E:A readily secrete endostatin and angiostatin prior to lysis. The inclusion of the endostatin/angiostatin gene did not negatively impact the measles virus’ cytotoxicity against medulloblastoma cells or alter its growth kinetics. Conditioned media obtained from these infected cells was capable of inhibiting multiple angiogenic factors in vitro, significantly reducing endothelial cell tube formation, viability and migration compared to conditioned media derived from cells infected by a control measles virus. Mice that were given a single intratumoral injection of MV-E:A likewise showed reduced numbers of tumor-associated blood vessels and a trend for increased survival compared to mice treated with the control virus.

Conclusions

These data suggest that oncolytic measles viruses encoding anti-angiogenic proteins may have therapeutic benefit against medulloblastoma and support ongoing efforts to target angiogenesis in medulloblastoma.

Update on oncolytic viral therapy - targeting angiogenesis

Oncolytic viruses (OVs) have the ability to selectively replicate in and lyse cancer cells. Angiogenesis is an essential requirement for tumor growth. Like OVs, the therapeutic effect of many angiogenesis inhibitors has been limited, leading to the development of more effective approaches to combine antiangiogenic therapy with OVs. Angiogenesis can be targeted either directly by OV infection of vascular endothelial cells, or by arming OVs with antiangiogenic transgenes, which are subsequently expressed locally in the tumor microenvironment. In this review, we describe the development and targeting of OVs, the role of angiogenesis in cancer, and the progress made in arming viruses with antiangiogenic transgenes. Future developments required to optimize this approach are addressed.

Delivery of the co-expression plasmid pEndo-Si-Stat3 by attenuated Salmonella serovar typhimurium for prostate cancer treatment

OBJECTIVES

To investigate the therapeutic utility of an attenuated bacterium carrying a plasmid that co-expresses Endostatin, an inhibitor of tumor neovasculogenesis, and a shRNA that targets Stat3 to suppress prostate cancer growth.

METHODS

Plasmid pEndo-Si-Stat3 was constructed and introduced into an attenuated strain of Salmonella enterica serovar typhimurium. The resultant recombinant bacterium was used as a vector to deliver the plasmid to tumor cells growing in vivo. Tumor-associated gene and protein expression changes were measured by using RT-PCR and Western blot analyses. Expression of Endostatin in tumor tissue was detected by ELISA. The presence of vector bacteria in tissues was monitored and tumor destruction was assessed by using TUNEL and H&E staining assays.

RESULTS

Bacterially delivered pEndo-Si-Stat3 decreased Stat3 levels and increased Endostatin expression in mouse tumors, resulting in a significant suppression of tumor growth (P < 0.01). Expression of Bcl-2 and PCNA was down-regulated and Caspase3 expression was up-regulated to promote apoptosis of tumor cells.

CONCLUSIONS

Successful delivery by attenuated Salmonella of the combination therapeutic plasmid simultaneously knocked down the expression of Stat3 and resulted in over-expression of Endostatin, which synergistically inhibited prostate cancer growth.

Angiogenesis inhibition using an oncolytic herpes simplex virus expressing endostatin in a murine lung cancer model

Herpes-mediated viral oncolysis alone is not sufficient to completely eradicate tumors. In this study we used a replication conditional, endostatin-expressing herpes simplex virus-1 mutant (HSV-Endo) in a murine lung cancer model. We hypothesized that the anti-angiogenic action of endostatin would improve upon the oncolytic effect of HSV-1. HSV-Endo was evaluated in a pulmonary metastases and orthotopic flank model, where there was significantly less tumor burden and reduced microvessel density compared to a control virus. Endostatin expression appears to improve the anti-tumor effect of HSV-1 in a lung cancer model.

Bevacizumab with angiostatin-armed oHSV increases antiangiogenesis and decreases bevacizumab-induced invasion in U87 glioma

Bevacizumab (BEV) is an antiangiogenic drug approved for glioblastoma (GBM) treatment. However, it does not increase survival and is associated with glioma invasion. Angiostatin is an antiangiogenic polypeptide that also inhibits migration of cancer cells, but is difficult to deliver. Oncolytic viruses (OV) can potentially spread throughout the tumor, reach isolated infiltrating cells, kill them and deliver anticancer agents to uninfected cells. We have tested a combination treatment of BEV plus an OV expressing angiostatin (G47Δ-mAngio) in mice-bearing human GBM. Using a vascular intracranial human glioma model (U87) in athymic mice, we performed histopathological analysis of tumors treated with G47Δ-mAngio or BEV alone or in combination, followed tumor response by magnetic resonance imaging (MRI), and assessed animal survival. Our results indicate that injection of G47Δ-mAngio during BEV treatment allows increased virus spread, tumor lysis, and angiostatin-mediated inhibition of vascular endothelial growth factor (VEGF) expression and of BEV-induced invasion markers (matrix metalloproteinases-2 (MMP2), MMP9, and collagen). This leads to increased survival and antiangiogenesis and decreased invasive phenotypes. We show for the first time the possibility of improving the antiangiogenic effect of BEV while decreasing the tumor invasive-like phenotype induced by this drug, and demonstrate the therapeutic advantage of combining systemic and local antiangiogenic treatments with viral oncolytic therapy.

Baculovirus vectors for antiangiogenesis-based cancer gene therapy

Baculovirus is an insect virus that is non-pathogenic to humans and has emerged as a promising gene therapy vector. Since solid tumor growth/metastasis critically relies on angiogenesis and hEA, a fusion protein comprising human endostatin and angiostatin, exhibits potent antiangiogenic and antitumor efficacy in mouse models; this study aimed to evaluate the feasibility of baculovirus for hEA expression and antiangiogenesis-based cancer gene therapy. Toward this end, we constructed Bac-hEA that mediated transient hEA expression and Bac-ITR-hEA that exploited the adeno-associated virus inverted terminal repeats (ITRs) for prolonged hEA expression. Western blot and ELISA analyses showed that both Bac-hEA and Bac-ITR-hEA expressed hEA in transduced mammalian cells, yet Bac-ITR-hEA only marginally prolonged the hEA expression. In comparison with Bac-hEA, nonetheless, Bac-ITR-hEA significantly enhanced the hEA expression level that concurred with augmented antiangiogenic properties, as demonstrated by cell proliferation, migration and tubule network formation assays. Importantly, intratumoral injection of Bac-ITR-hEA into prostate cancer mouse models, when compared with Bac-hEA, exerted stronger antiangiogenic effects in vivo, more potently inhibited tumor growth and significantly prolonged mouse survival. This study collectively supported the notion that hEA is an effective antiangiogenic protein and proved the potential of baculovirus as a vector for antiangiogenesis-based cancer therapy, which may be combined with chemotherapy, radiotherapy or gene therapies using other vectors.

Comparison of angiotensin converting enzyme inhibitors and angiotensin II type 1 receptor blockade for the prevention of premalignant changes in the liver

AIM

We investigate and compare the possible antitumor activity of clinically used angiotensin converting enzyme (ACE) inhibitors; captopril, perindopril and angiotensin II type 1 receptor (AT1R) blocker, losartan against hepatocarcinogenesis initiated by diethylnitrosoamines (DENA) and promoted by carbon tetrachloride (CCl(4)).

MAIN METHODS

Diethylnitrosamine (DENA) (200mg/kgi.p.) initiated and carbon tetrachloride (CCl(4)) (2ml/kgi.p.) promoted hepatocarcinogenesis in male Wistar rats after 8weeks.

RESULTS

Hepatocarcinogenesis was manifested biochemically by elevation of serum hepatic tumor markers tested; α-feto protein (AFP) and carcinoembryonic antigen (CEA). In addition, hepatic carcinogenesis was further confirmed by a significant increase in hepatic tissue growth factors; vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF). Moreover a marked increase in matrix metalloproteinase-2 and hydroxyproline content were also observed. Hepatocarcinogenesis was further confirmed by a significant decrease in hepatic endostatin and metallothonein level.

KEY FINDINGS

Long-term administration of the selected drugs for 2weeks before and throughout the experimental period produced a significant protection against hepatic carcinogenesis. The present results claimed that different doses of the selected drugs succeeded in normalization of serum tumor markers. Furthermore, the drugs reduced the elevated level in the hepatic growth factors, matrix metalloproteinase-2 and hydroxyproline induced by the hepatocarcinogen. Moreover, the amelioration was also accompanied by augmentation of hepatic content of metallothionein and endostatin. Histopathological examination of liver tissues of rats treated with DENA-CCl(4) correlated with the biochemical observations.

SIGNIFICANCE

These findings suggest a similar protective effect of ACE inhibitors; captopril; perindopril and AT1R blocker, losartan against premalignant stages of liver cancer in the DENA initiated and CCl(4) promoted hepatocarcinogenesis model in rats. Therefore, RAS especially angiotensin II (Ang II) and AT1R interaction plays a pivotal role hepatocarcinogenesis development.

Lister vaccine strain of vaccinia virus armed with the endostatin-angiostatin fusion gene: an oncolytic virus superior to dl1520 (ONYX-015) for human head and neck cancer

Oncolytic viral therapy represents a promising strategy for the treatment of head and neck squamous cell carcinoma (HNSCC), with dl1520 (ONYX-015) the most widely used oncolytic adenovirus in clinical trials. This study aimed to determine the effectiveness of the Lister vaccine strain of vaccinia virus as well as a vaccinia virus armed with the endostatin-angiostatin fusion gene (VVhEA) as a novel therapy for HNSCC and to compare them with dl1520. The potency and replication of the Lister strain and VVhEA and the expression and function of the fusion protein were determined in human HNSCC cells in vitro and in vivo. Finally, the efficacy of VVhEA was compared with dl1520 in vivo in a human HNSCC model. The Lister vaccine strain of vaccinia virus was more effective than the adenovirus against all HNSCC cell lines tested in vitro. Although the potency of VVhEA was attenuated in vitro, the expression and function of the endostatin-angiostatin fusion protein was confirmed in HNSCC models both in vitro and in vivo. This novel vaccinia virus (VVhEA) demonstrated superior antitumor potency in vivo compared with both dl1520 and the control vaccinia virus. This study suggests that the Lister strain vaccinia virus armed with an endostatin-angiostatin fusion gene may be a potential therapeutic agent for HNSCC.

Inhibition of angiogenesis and suppression of colorectal cancer metastatic to the liver using the Sleeping Beauty Transposon System

Background

Metastatic colon cancer is one of the leading causes of cancer-related death worldwide, with disease progression and metastatic spread being closely associated with angiogenesis. We investigated whether an antiangiogenic gene transfer approach using the Sleeping Beauty (SB) transposon system could be used to inhibit growth of colorectal tumors metastatic to the liver.

Results

Liver CT26 tumor-bearing mice were hydrodynamically injected with different doses of a plasmid containing a transposon encoding an angiostatin-endostatin fusion gene (Statin AE) along with varying amounts of SB transposase-encoding plasmid. Animals that were injected with a low dose (10 μg) of Statin AE transposon plasmid showed a significant decrease in tumor formation only when co-injected with SB transposase-encoding plasmid, while for animals injected with a higher dose (25 μg) of Statin AE transposon, co-injection of SB transposase-encoding plasmid did not significantly affect tumor load. For animals injected with 10 μg Statin AE transposon plasmid, the number of tumor nodules was inversely proportional to the amount of co-injected SB plasmid. Suppression of metastases was further evident in histological analyses, in which untreated animals showed higher levels of tumor cell proliferation and tumor vascularization than animals treated with low dose transposon plasmid.

Conclusion

These results demonstrate that hepatic colorectal metastases can be reduced using antiangiogenic transposons, and provide evidence for the importance of the transposition process in mediating suppression of these tumors.

Ginger ingredients inhibit the development of diethylnitrosoamine induced premalignant phenotype in rat chemical hepatocarcinogenesis model

To investigate the possible antitumor activity of ginger extract against hepatic carcinogenesis initiated by diethylnitrosoamines (DEN) and promoted by carbon tetrachloride (CCl(4) ). A total of 60 male Wistar albino rats were divided into four groups with 15 animals in each group. Rats in group 1 (control group) received a single intraperitoneal (i.p.) injection of normal saline. Animals in group 2 were given ginger (50 mg/kg/day) in drinking water for 8 weeks. Rats in group 3 (DEN group) were injected with a single dose of DEN (200 mg/kg, i.p.), 2 weeks later received a single dose of CCl(4) (2 mL/kg i.g) by gavage as 1:1 dilution in corn oil. Animals in group 4 (DEN-ginger group) received the same carcinogenesis induction protocol as in group 3 plus ginger (50 mg/kg/day) in drinking water for 2 weeks before induction of hepatocarcinogenesis and continued throughout the experimental period. DEN-initiated and CCl(4) -promoted hepatocarcinogenesis in male Wistar rats was manifested biochemically by elevation of serum hepatic tumor markers tested; α-fetoprotein and carcinoembryonic antigen. In addition, hepatocarcinogenesis was further confirmed by a significant increase in hepatic tissue growth factors; vascular endothelial growth factor, basic fibroblast growth factor, and hydroxyproline content. A marked decrease in endostatin and metallothonein were also observed. Long-term ginger extract administration 2 weeks before induction of hepatocarcinogenesis and throughout the experimental period prevented the decrease of the hepatic content of metallothionein and endostatin and the increase in the growth factors induced by the carcinogen. Moreover, ginger extract normalize serum hepatic tumor markers. Histopathological examination of liver tissue also correlated with the biochemical observations. These findings suggest a protective effect of ginger extract against premalignant stages of liver cancer in the DEN-initiated and CCl(4) -promoted hepatocarcinogenesis model in rats.

Gene therapy with the angiogenesis inhibitor endostatin in an orthotopic lung cancer murine model

Angiogenesis plays an important role in the growth of solid tumors. To date, no information has been acquired on the effectiveness of gene therapy in the orthotopic lung cancer model of syngeneic immunocompetent mice treated with an angiogenesis inhibitor. Here, we report the establishment of such a model in which Lewis lung carcinoma (LL/2) cell suspensions were orthotopically inoculated into the lung parenchyma of C57BL/6 mice, which were also injected with a recombinant adenoviral vector delivering the human endostatin gene (Ad-hE). We found that orthotopic implantation of LL/2 cells into the lung parenchyma produced a solitary tumor nodule in the lung followed by remote mediastinal lymph node metastasis. Conditioned medium from Ad-hE-transfected LL/2 cells apparently inhibited proliferation of human umbilical vein endothelial cells (HUVECs). The level of endostatin protein in serum could be identified by enzyme-linked immunosorbent assay. Treatment with Ad-hE resulted in inhibition of tumor growth and prolongation of survival time of tumor-bearing mice. Immunohistochemical analysis revealed that intratumoral angiogenesis was significantly suppressed. Furthermore, the finding of angiogenesis inhibition was also supported by measuring the number of circulating endothelial cells (CECs). Apoptotic cells were found to be increased within tumor tissues from mice treated with Ad-hE. In addition, treatment with Ad-hE combined with cis-diamminedichloroplatinum(II) (cisplatin) enhanced antitumor activity. These observations provide further evidence of the antitumor effect of endostatin gene therapy, and may be of importance for further exploration of potential application of this combined approach in the treatment of human lung cancer as well as other solid tumors.

Docetaxel increases antitumor efficacy of oncolytic prostate-restricted replicative adenovirus by enhancing cell killing and virus distribution

BACKGROUND

We explored multiple molecular mechanisms of the combination of docetaxel and an oncolytic prostate-restricted replication competent adenovirus (Ad) (PRRA) in advanced prostate cancer (PCa) models. The combinational therapy has potential to overcome the therapeutic limitations of poor virus distribution inside solid tumors.

METHODS

We evaluated the effect of docetaxel on the antitumor efficacy and efficiency of virus transduction, transgene expression and virus distribution of PRRA in a prostate-specific antigen/prostate-specific membrane antigen-positive tumor xenograft model. We also evaluated the effect of docetaxel on apoptosis induction, cell killing and the efficiency of transgene expression and virus replication in vitro.

RESULTS

Tumor growth inhibition was significantly enhanced when docetaxel was administrated before intratumor injection of PRRA. In vivo dual-photon microscopy and ex vivo fluorescence microscopy and immunohistochemistry showed that docetaxel increased transgene expression and expanded virus distribution. The combination of docetaxel and PRRA also increased cell apoptosis. In vitro, docetaxel significantly increased cell killing in PRRA-treated PCa cells. Docetaxel significantly increased Ad-mediated trangene expression independent of Ad binding receptors and replication capability. Docetaxel increased the activity of cytomegalovirus (CMV) promoter but not of a chimeric prostate-specific enhancer, resulting in higher transgene expression. The enhanced CMV promoter activity resulted from activation of p38 mitogen-activated protein kinase (MAPK) because inhibition of p38 MAPK blocked the docetaxel-induced increase in CMV promoter activity.

CONCLUSIONS

Combining docetaxel with an oncolytic PRRA improved therapeutic potential by expanding virus distribution and enhancing cell apoptosis and killing. These studies suggested a novel mechanism for enhancing the effect of therapeutic genes delivered by a PRRA.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

Antiangiogenesis gene armed tumor-targeting adenovirus yields multiple antitumor activities in human HCC xenografts in nude mice

AIM

Gene therapy represents a promising therapeutic strategy for hepatocellular carcinoma (HCC). To improve the ratio of killing efficacy on tumor cells to side-effect on normal cells, we constructed an oncolytic adenovirus vector, AdSu-hE, expressing the human endostatin (hE) gene, in which the chimeric promoter of human epidermal growth factor receptor 2 enhancer and human telomerase reverse transcriptase promoter was used to control the adenoviral E1a gene.

METHODS

Tumor-selective replication of adenovirus AdSu-hE and its concomitant expression of endostatin were measured by 50% tissue culture infective dose method, fluorescent protein expression, Western blot and enzyme linked immunosorbent assay in cancer and normal cell lines. The antitumor efficacy was observed in nude mice bearing human HCCs.

RESULTS

The oncolytic adenovirus AdSu-hE replicated restrictedly in telomerase-positive cancer cells and resulted in oncolysis, but did not replicate in normal cell lines. Along with virus replication, AdSu-hE mediated 5-fold increased expression of endostatin in tumor cells compared with that in normal cells. Moreover, AdSu-hE expressed more endostatin in cancer cells than the non-replicative adenovirus vector Ad-hE. In vivo administration of the oncolytic adenovirus AdSu-hE into HCC-bearing nude mice produced a significant tumor reduction by synergistic effects of virus oncolysis and endostatin antiangiogenesis.

CONCLUSION

The oncolytic virus with antiangiogenesis gene driven by the chimeric promoter has an improved killing efficacy on tumor cells, and may be useful for cancer gene therapy.

Lister strain of vaccinia virus armed with endostatin-angiostatin fusion gene as a novel therapeutic agent for human pancreatic cancer

Survival following pancreatic cancer remains poor despite incremental advances in surgical and adjuvant therapy, and new strategies for treatment are needed. Oncolytic virotherapy is an attractive approach for cancer treatment. In this study, we have evaluated the effectiveness of the Lister vaccine strain of vaccinia virus armed with the endostatin-angiostatin fusion gene (VVhEA) as a novel therapeutic approach for pancreatic cancer. The Lister vaccine strain of vaccinia virus was effective against all human pancreatic carcinoma cells tested in vitro, especially those insensitive to oncolytic adenovirus. The virus displayed inherently high selectivity for cancer cells, sparing normal cells both in vitro and in vivo, with effective infection of tumors after both intravenous (IV) and intratumoral (IT) administration. The expression of endostatin-angiostatin fusion protein was confirmed in a pancreatic cancer model both in vitro and in vivo, with evidence of inhibition of angiogenesis. This novel vaccinia virus demonstrated significant antitumor potency in vivo against the Suit-2 model by IT administration. The present study suggests that the novel Lister strain of vaccinia virus armed with the endostatin-angiostatin fusion gene is a potential therapeutic agent for pancreatic cancer.

Endostatin and anastellin inhibit distinct aspects of the angiogenic process

Background

Endostatin and anastellin, fragments of collagen type XVIII and fibronectin, respectively, belong to a family of endogenous inhibitors of angiogenesis which inhibit tumor growth and metastasis in a number of mouse models of human cancer. The mechanism of action of these inhibitors is not well understood, but they have great potential usefulness as non-toxic long-term therapy for cancer treatment.

Methods

In this study, we compare the anti-angiogenic properties of endostatin and anastellin using cell proliferation and transwell migration assays.

Results

Anastellin but not endostatin completely inhibited human dermal microvessel endothelial cell proliferation in response to serum stimulation. Both anastellin and endostatin additively inhibited endothelial cell migration in response to VEGF. Anastellin but not endostatin lowered basal levels of active ERK.

Conclusion

These data indicate that anastellin and endostatin exert their anti-angiogenic effects by modulating distinct steps in the angiogenic pathway and suggest that matrix-derived inhibitors of angiogenesis may exhibit higher efficacy when used in combination.