Expression of Cytosine Deaminase Gene in Human Colon Carcinoma Cells by Recombinant Retroviral Vector.

The recombinant retroviral vector pLCDSN containing E. coli cytosine deaminase gene was constructed. After packaging with PA317 cell line, the infectious particles were used to infect human colon carcinoma cell line LoVo. A single clone harbouring EC-CD gene was picked after G418 selection. There was no significant difference in cell growth curve or morphology between the LoVo/LCDSN and LoVo cells. Both of them were very sensitive to 5-FU in vitro (IC(50), approximately 0.5 &mgr;mol/L). However, the expression of the CD gene did increase the sensitivity of these cells to the nontoxic prodrug, 5-FC, decreasing the IC(50) for 5-FC from 22 000 &mgr;mol/L for parental LoVo cells to 13 &mgr;mol/L for LoVo/LCDSN cells. Obvious by side effect was also observed. When cells transduced with CD gene were mixed with wild type cells at a ratio of 30:70, above 80% of the cancer cells could be killed after treatment with a nontoxic concentration of 5-FC.