Cytotoxic effect of the cytosine deaminase gene delivered by the adenovirus vector in murine gastric cancer

OBJECTIVE: To improve the efficacy of gene delivery and to determine an effective way to kill gastric cancer cells by using a suicide gene. METHODS: First, the cytosine deaminase (CD) gene was cloned into an adenovirus vector and the recombinant plasmid was packed, amplified and purified. Murine gastric cancer cell line MFC was injected subcutaneously into the flanks of 615 mice, and when tumors were palpable, 0.2 mL of the recombinant adenovirus solution was injected directly into xenografts following the daily administration of 5-fluorocytosine (5-Fc) for 35 days. RESULTS: Positive clones were selected by using endonucleases to digest the recombinants, and the concentration of viral particles containing the CD gene was 1.2 × 1012 particles/mL. An antitumor effect was observed in MFC–CD(+) tumors when the animals were given 5-Fc via intraperitoneal injection. Pathologically, the tumors generated from MFC–CD(+) cells had widespread hemorrhagic necrosis within the tumor regions as compared with those of untreated animals, which had few necrotic regions. CONCLUSIONS: The improved antitumor effect of this adenovirus vector suggests a basis for further research involving the direct transduction of the CD gene into tumors, as well as inducing an intensive bystander effect.