Antitumor activity of mutant bacterial cytosine deaminase gene for colon cancer

AIM： To evaluate bacterial cytosine deaminase （bCD） mutant D314A and 5-fluorocytosine （5-FC） for treatment of colon cancer in a mouse model. METHODS： Recombinant lentivirus vectors that contained wild-type bCD gene （bCDwt）, and bCD mutant D314A gene （bCD-D314A） with green fluorescence protein gene were constructed and used to infect hu- man colon carcinoma LoVo cells, to generate stable transfected cells, LoVo/null, LoVo/bCDwt or LoVo/bCD- D314A. These were injected subcutaneously into Balb/c nude mice to establish xenograft models. Two weeks post-LoVo cell inoculation, PBS or 5-FC （500 mg/kg） was administered by intraperitoneal （i.p.） injection once daily for 14 d. On the day after LoVo cell injection, mice were monitored daily for tumor volume and survival. RESULTS： Sequence analyses confirmed the construction of recombinant lentiviral plasmids that contained bCDwt or bCD-D314A. The lentiviral vector had high elficacy for gene delivery, and RT-PCR showed that bCDwt or bCD-D314A gene was transferred to LoVo cells. Among these treatment groups, gene delivery or 5-FC administration alone had no effect on tumor growth. However, bCDwt/5-FC or bCD-D314A/5-FC treatment inhibited tumor growth and prolonged survival of mice significantly （P 〈 0.05）. Importantly, the tumor volume in the bCD-D314A/5-FC-treated group was lower than that in the bCDwt/5-FC group （P 〈 0.05）, and bCD- D314A plus 5-FC significantly prolonged survival of mice in comparison with bCDwt plus 5-FC （P 〈 0.05）. CONCLUSION： The bCD mutant D314A enhanced significantly antitumor activity in human colon cancer xenograft models, which provides a promising approach for human colon carcinoma therapy.