Transduction of hepatocellular carcinoma (HCC) using recombinant adeno-associated virus (rAAV): in vitro and in vivo effects of genotoxic agents

Background/Aims: Adeno-associated virus (AAV) is an attractive tool for gen e therapy. Here we investigated the in vitro and in vivo transduction of he patocellular carcinoma (HCC) cells by an AAV vector and the efficacy of dif ferent strategies to enhance the transduction of the tumor. Methods: Transduction efficiency was determined by analyzing AAV-mediated b eta-galactosidase gene (rAAV/ lacZ) expression. Results: Adenovirus help or pretreatment of HCC cells with gamma-irradiatio n or with the topoisomerase inhibitor etoposide resulted in marked enhancem ent of cell transduction in vitro, In vivo studies in nude mice with subcut aneous HCC tumors showed that HCC cells were not transduced by AAV vector a lone. However, co-infection of the tumor with adenovirus allowed an efficie nt expression of the reporter gene but only at the sites of vector injectio n. Previous gamma-irradiation of subcutaneous tumors with 1800 rad was able to improve transduction of HCC cells (up to 30%) using recombinant AAV Con tinuous i.p. infusion of etoposide in buffalo rats harboring HCC tumors in the liver resulted in transduction of normal liver tissue and also of very small neoplastic lesions (<2 mm) but no transduction was observed in tumors bigger than 2 mm, To analyze this phenomenon we determined etoposide conce ntration in hepatic tissue. Our results revealed high concentrations of the drug in non-tumoral tissue but almost undetectable levels in big tumor nod ules, Conclusions: Our results indicate that while both radiotherapy and etoposid e enhance transduction of tumor cells by rAAV in vitro, only radiotherapy i ncreases tumor transduction in vivo. Our data suggest the existence of a ba rrier which limits in vivo the diffusion of chemotherapeutic agents to well -established HCC nodules.