Oncolytic adenoviral vector carrying the cytosine deaminase gene for melanoma gene therapy

We constructed an oncolytic adenoviral vector Ad.HE1HCD3, in which the adenoviral E1A promoter was replaced by a human tyrosinase enhancer (HTE)/promoter. The RGD-4C peptide was inserted into the HI loop of the fiber knob domain to increase the transduction efficiency of this vector for tumor cell lines. We also inserted the prodrug activating cytosine deaminase gene driven by the HTE/promoter into the E3 region of the Ad.HE1HCD3 vector. The in vitro cytotoxic effect of the Ad.HE1HCD3 vector with 5-fluorocytosine (5-FC) was greater than that of a wild-type adenovirus or that of the Ad.HE1HCD3 vector alone in tyrosinase-positive melanoma cell lines at low multiplicity of infection. Intratumoral injection of low doses of the Ad.HE1HCD3 vector into xenotransplanted human melanoma cell lines followed by the intraperitoneal injection of 5-FC led to a greater degree of tumor regression in vivo than did the intratumoral injection of the same dose of the Ad.HE1HCD3 vector alone. This oncolytic vector with a melanoma-specific prodrug activation therapeutic transcription unit and a RGD targeted fiber protein offers a potent therapeutic combination for the gene therapy of melanoma.