HSV-tk gene therapy for human renal cell carcinoma in nude mice

Abstract

We have treated Caki -2 human renal cell carcinoma in vivo using herpes simplex virus thymidine kinase ( HSV -tk ) gene therapy. Both stably transduced Caki -2 tumors, generated using retrovirus -mediated ex vivo HSV -tk gene transfer and direct intratumoral adenovirus -mediated HSV -tk gene transfer of wild type tumors, were tested. Similar treatments with LacZ containing retro -and adenoviruses were used as controls. The outcome was evaluated by imaging the tumors before and after the treatment with magnetic resonance imaging, and using histology, immunocytochemistry, and survival analysis. When implanted orthotopically into nude mouse kidneys, Caki -2 cells formed reproducible cystic papillary kidney carcinomas. In vivo magnetic resonance imaging provided an important tool for the evaluation of tumor growth. Transduction efficiency of wild -type tumors in vivo with adeno -LacZ was 22 14%. Significant tumor regression was achieved with direct intratumoral adeno -HSV -tk transduction followed by intraperitoneal ganciclovir ( GCV ) ( P < .001 ). Also, the treatment of stably transduced Caki -2 tumors with intraperitoneal GCV resulted in a significant treatment response in the HSV -tk group as compared to the LacZ group ( P < .009 ). Increased apoptosis and macrophage infiltrations, reduced proliferation, and degenerative changes were observed in the tumors treated with HSV -tk and GCV. Also, significant prolongation in survival was achieved with adeno -HSV -tk ± and GCV -treated mice as compared to the controls. It is concluded that adeno -HSV -tk gene therapy may be useful for the treatment of renal cell carcinoma in vivo. Cancer Gene Therapy ( 2001 ) 8, 529 ± 536

The combination of HSV-tk and endostatin gene therapy eradicates orthotopic human renal cell carcinomas in nude mice

“…In this study, HSV-tk, coupled with acyclovir, failed to demonstrate any antitumor effect. The discrepancy between this and our previous study, where HSV-tk monotherapy was used, 18 may be due to the fact that tumor cells in our model express gap junctions and display a bystander effect, 17,29 allowing more efficient action of GCV. 30 Also, GCV is a more potent replication terminator than acyclovir.…”

“…18 Immunoblotting and immunocytochemistry of in vitro ES -transduced U251MG cells showed the presence of the c-myc tag in the cell lysate and culture medium, and strong intracellular expression of the c -myc -tagged ES, respectively (Fig 2, A and B ), thus confirming the functionality of the vector. The in vivo gene transfer efficiency in the Caki -2 tumors was 27 ±7% on day 7 posttransduction ( Fig 3A ).…”

“…Although local gene transfer was used, marker gene studies in this animal model showed that a small number of adenoviruses escape into the circulation, leading to transduction of liver. 18 As the potency of endostatin is well established, 37 it is possible that even a low -level transduction of liver by ES can result in a sufficient and sustained production of endostatin into circulation to maintain tumor dormancy. Indeed, we detected the presence of endostatin in the livers of intratumorally ES -transduced mice, but not in the controls, on day 7 after the transduction using genomic PCR ( data not shown ).…”

“…17 Also, tumor samples and selected tissues from each animal were embedded in OCT compound (Miles Scientific, Naperville, IL, USA ) and processed for frozen sections. 18,24 In vivo transduction efficiency was examined from frozen sections by calculating GFP -positive cells ( percent of all cells ) 7 and 20 days posttransduction using four sections per tumor 100 m apart from each other, and 10 fields per section with 40 -fold magnification, covering systematically the central and peripheral areas of each tumor.…”

“…Neither HSV-tk adenovirus in the absence of GCV, nor GCV coupled with an adenovirus containing a LacZ marker gene had any antitumor effect. 18 Given the high vascularity of human RCCs and the inability of HSV-tk monotherapy to eradicate the tumors, we decided to test a novel combination of cytotoxic and antiangiogenic gene therapy using intratumorally delivered HSV-tk and ES adenoviruses. It was found that the transduction efficiency, measured from GFP -transduced tumors, was 27± 7%.…”