Gene transfer to hepatocellular carcinoma: Transduction efficacy and transgene expression kinetics by using retroviral and lentiviral vectors

Gene therapy is an attractive therapy for hepatocarcinoma, and several appr oaches have been studied using murine leukemia virus-derived retroviruses. We compared gene transfer efficacy and transgene expression kinetics after transduction of hepatocarcinoma cell lines using enhanced green fluorescent protein (EGFP)-expressing murine leukemia virus-derived retroviral vectors and HIV-derived lentiviral vectors. First, we showed that both retroviral and lentiviral vectors efficiently transduce cycling hepatocarcinoma cell l ines in vitro. However. after cell cycle arrest, transduction efficacy rema ined the same for tentiviral vectors bur it decreased by 80% for retroviral vectors. Second, we studied EGFP expression kinetics using lentiviral vect ors expressing EGFP under the control of cytomegalovirus (CMV) or phosphogl ycerolkinase (PGK) promoter. We show that the CMV promoter allows a stronge r EGFP expression than the PGK promoter. However, in contrast to PGK-driven EGFP expression, which persists up to 2 months after transduction. CMV-dri ven EGFP expression rapidly decreased with time. This phenomenon is due to promoter silencing, and EGFP expression can be restored in transduced cells by using transcription activators such as interleukin-6 or phorbol myrista te actate/ionomycin and, to a lesser extent, the demethylating agent 5'-aza cytidine. Altogether, our results suggest that lentiviral vectors. which al low efficient transduction of hepatocarcinoma cell lines with a strong and a sustained expression according to the promoter used, are promising tools for gene therapy of hepatocarcinomas.