Loss of mismatch repair activity in simian virus 40 large T antigen-immortaIized BPH-1 human prostatic epithelial cell line

Simian virus 40 large T antigen (SVLTAg) has been used to immortalize cells ; however, the mechanism leading to immortalization is still unclear. We hy pothesize that DNA mismatch repair (MMR) activity is important during SVLTA g-induced immortalization. To test this hypothesis, we used the SVLTAg-immo rtalized cell line BPH-1 derived from human benign prostate epithelial cell s to analyze MMR activity and the expression of MMR genes (hMLH1, hPMS1, hP MS2, hMSH2, hMSH3, and hMSH6). The results demonstrated that BPH-1 cells we re deficient in repairing G:T, A:C, and G:G mispairs in bacterlophage M13mp 2. Reverse-transcription polymerase chain reaction experiments indicated MM R genes (hMSH3, hMSH6, and hPMS1) were expressed at a low level in BPH-1 ce lls. In contrast, all six MMR genes were expressed in human benign prostate hyperplasia tissues. Downregulation of hMSH3, hMSH6, and hPMS1 genes is no t a result of the hypermethylation mechanism because demethylation with 5-a za-2'-deoxycytidine did not restore expression of these genes. Although the hMLH1 gene is expressed in BPH-1 cells, western blotting and exon analyses demonstrated that hMLH1 was mutated and/or deleted in BPH-1 cells. (C) 200 1 Wiley-Liss, Inc.