Induction of sensitivity to ganciclovir in human hepatocellular carcinoma cells by adenovirus-mediated gene transfer of herpes simplex virus thymidine kinase

Combined transductional untargeting/retargeting and transcriptional restriction enhances adenovirus gene targeting and therapy for hepatic colorectal cancer tumors

Unresectable hepatic colorectal cancer (CRC) metastases are a leading cause of cancer mortality. These tumors and other epithelial tumors often express both cyclooxygenase-2 (COX-2) and carcinoembryonic antigen (CEA). Because adenovirus (Ad) vectors infect the liver and lack tumor tropism, they cannot be used for systemic therapy of hepatic metastases. We used COX-2 transcriptional restriction, in combination with transductional Ad hepatic untargeting and tumor retargeting by a bispecific adapter, sCARhMFE, composed of sCAR [the coxsackie/Ad receptor (CAR) ectodomain] and MFE-23 (a single-chain anti-CEA antibody), to untarget liver after i.v. administration of Ad vectors expressing firefly luciferase and to retarget virus to hepatic colorectal tumor xenografts and non-small cell lung tumor xenografts. To improve both liver untargeting and tumor retargeting, we developed sCARfMFE, a trimerized sCARhMFE adapter. Trimerization greatly improves both untargeting of CAR-dependent Ad infection and CEA-dependent virus retargeting in culture and in vivo. Combining sCARfMFE bispecific adapter transductional liver untargeting and transductional tumor retargeting with COX-2 transcriptional tumor-restricted transgene expression increases systemically administered Ad therapeutic efficacy for hepatic CRC tumors, using herpes virus type 1 thymidine kinase (HSV1-tk) as a therapeutic gene in conjunction with the prodrug ganciclovir (GCV). Both transductional untargeting and COX-2 transcriptional restriction also reduce HSV1-tk/GCV hepatic toxicity. In addition, transductional sCARfMFE untargeting reduces the innate immune response to systemic Ad administration. Combined transductional liver Ad untargeting, transductional tumor retargeting, and transcriptional transgene restriction suggests a means to engineer practical, effective therapeutic agents for hepatic CRC metastases in particular, as well as hepatic metastases of other epithelial cancers.

Treatment of metastatic colorectal carcinomas by systemic inhibition of vascular endothelial growth factor signaling in mice

AIM: Tumor angiogenesis has been shown to be promoted by vascular endothelial growth factor (VEGF) via stimulating endothelial cell proliferation, migration, and survival. Blockade of VEGF signaling by different means has been demonstrated to result in reduced tumor growth and suppression of tumor angiogenesis in distinct tumor entities. Here, we tested a recombinant adenovirus, AdsFlt1-3, that encodes an antagonistically acting fragment of the VEGF receptor 1 (Flt-1), for systemic antitumor effects in pre-established subcutaneous CRC tumors in mice.

METHODS: Murine colorectal carcinoma cells (CT26) were inoculated subcutaneously into Balb/c mice for in vivo studies. Tumor size and survival were determined. 293 cell line was used for propagation of the adenoviral vectors. Human lung cancer line A₅₄₉ and human umbilical vein endothelial cells were transfected for in vitro experiments.

RESULTS: Infection of tumor cells with AdsFlt1-3 resulted in protein secretion into cell supernatant, demonstrating correct vector function. As expected, the secreted sFlt1-3 protein had no direct effect on CT26 tumor cell proliferation in vitro, but endothelial cell function was inhibited by about 46% as compared to the AdLacZ control in a tube formation assay. When AdsFlt1-3 (5×10⁹ PFU/animal) was applied to tumor bearing mice, we found a tumor inhibition by 72% at d 12 after treatment initiation. In spite of these antitumoral effects, the survival time was not improved. According to reduced intratumoral microvessel density in AdsFlt1-3-treated mice, the antitumor mechanism can be attributed to angiostatic vector effects. We did not detect increased systemic VEGF levels after AdsFlt1-3 treatment and liver toxicity was low as judged by serum alanine aminotransferase determination.

CONCLUSION: In this study we confirmed the value of a systemic administration of AdsFlt1-3 to block VEGF signaling as antitumor therapy in an experimental metastatic colorectal carcinoma model in mice.

Gonadotropin-releasing hormone receptor–targeted gene therapy of gynecologic cancers

The majority of ovarian, endometrial, and breast cancers express gonadotropin-releasing hormone (GnRH) receptors. Apart from reproductive organs (ovaries, fallopian tubes, and uterus) that are normally removed during surgical therapy of ovarian or endometrial cancer, pituitary gonadotrophs also express GnRH receptors. The signal transduction pathway in tumor cells is basically different from the classic GnRH receptor signal transduction, which is known to operate in the pituitary gonadotrophs and can therefore be considered tumor specific. Other organs and hematopoetic stem cells do not express GnRH receptors. We have recently shown specific activation of nucleus factor κB in ovarian, endometrial, and breast cancers after treatment with GnRH agonists. Based on this tumor-specific signaling pathway and the distribution pattern of GnRH receptors, we have developed and successfully tested a gene therapy concept by using a GnRH analogue as an inducer for the transcription of a therapeutic gene in cell culture and in nude mice.