Role of SV40 T antigen binding to pRB and p53 in multistep transformation in vitro of human uroepithelial cells.

In the present study, we examined the sufficiency of SV40 T antigen (Tag) binding to pRB and p53 to substitute for alterations in RB and TP53 at all stages of human uroepithelial cell (HUC) transformation in vitro. Two independent SV40 immortalized HUCs (SV-HUC and SV-HUC/CK2) and 17 independent derivative carcinogen-induced or spontaneous tumors (T-SV-HUCs and T-SV-HUC/CK2) representing different stages of urothelial tumorigenesis were examined. Although five of 17 T-SV-HUCs and SV-HUC/CK2 and its derivative tumor showed 13q chromosome deletion and loss of heterozygosity (LOH), this did not reflect functional loss of pRB because Tag/pRB binding was unaltered and sequencing showed a normal RB gene in all these tumors. No genetic alterations involving 17p or TP53 were detected in any tumors in this study using the same techniques. These results indicate that Tag/pRB and Tag/p53 binding apparently abrogate requirements for/or a selective advantage of RB and TP53 mutations in HUC tumorigenic transformation and progression, as well as in HUC immortalization. These data also provide new evidence that more than one suppressor gene may be located on chromosome 13q.