Synergistic enhancement of resistance to cisplatin in human bladder cancer cells by overexpression of mutant-type p53 and Bcl-2.

Abstract

The objective of this study was to characterize the effect of mutant-type p53 and Bcl-2 expression on the sensitivity to cisplatin in a human bladder cancer cell line both in vitro and in vivo. We transfected mutant-type p53 cDNA, Bcl-2 cDNA, or both cDNAs into KoTCC-1, a human bladder cancer cell line that does not express mutant-type p53 or Bcl-2 protein. The effects of the overexpression of mutant-type p53, Bcl-2, or both on the sensitivity to cisplatin and the apoptotic features in vitro were evaluated by the MTT assay, staining with Hoechst 33258 and a DNA fragmentation assay. We then examined the in vivo effects of cisplatin treatment on the transfectants by subcutaneous and intraperitoneal tumor cell injection models in athymic nude mice. The introduction of mutant-type p53 or Bcl-2 conferred resistance to cisplatin on KoTCC-1 cells through the inhibition of apoptosis. This phenotype was more remarkable in the cell line transfected with both mutant-type p53 and Bcl-2 than in the cell lines transfected with either mutant-type p53 or Bcl-2 alone. Furthermore, the KoTCC-1 cells transfected with both mutant-type p53 and Bcl-2 exhibited significantly higher resistance to cisplatin treatment than cells transfected with mutant-type p53 or Bcl-2 alone in experimental models in vivo. These findings suggest that the overexpression of both mutant-type p53 and Bcl-2 in bladder cancer cells synergistically interferes with the therapeutic effect of cisplatin through the inhibition of the apoptotic pathway.