RESUMEN
<p><b>OBJECTIVE</b>To study the selective cytotoxic effect of lentivirus-mediated double suicide gene (CD/TK) against human gastric carcinoma cells SGC-7901 in vitro.</p><p><b>METHODS</b>SGC-7901 cells were infected with FGW-KDRP-CD/TK vector and the infection efficiency was observed under a fluorescence microscope. The morphological changes of the infected cells were observed by Giemsa staining. Flow cytometry (FCM) was employed for cell cycle analysis, and the expression of CD/TK was detected by RT-PCR. The infected cells were then treated with the prodrugs ganciclovir (GCV) and/or 5-fluorocytosine (5-FC) at different concentrations, and the cytotoxic effects were evaluated using MTT method.</p><p><b>RESULTS</b>The infection efficiency of the lentiviral vector in SGC-7901 cells increased with the titer of the virus, which produced no significant effect on the cancer cell morphology in vitro or on the percentages of G0-G1, G2-M and S phase cells (P>0.05). RT-PCR demonstrated the expression of CD/TK gene in SGC-7901 cells infected by FGW-KDRP-CD/TK. The infected cells were highly sensitive to the prodrugs with a dose-dependent cytotoxic effect within a specific concentration range of the drugs, whereas the non-infected cells were not sensitive to the prodrugs. Combined use of the two prodrugs produced an obviously stronger inhibitory effect than either of the them (P<0.05). When combined, GCV and 5-FC at the concentration of 0.1+40, 1+80, 10+160, and 100+320 mg/L demonstrated a synergetic effect with a CDI<1.</p><p><b>CONCLUSION</b>Lentivirus-mediated CD/TK fusion gene system can selectively kill gastric cancer cells, and the two prodrugs show a synergistic cytotoxic effect.</p>