Purpose: 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.
Materials and methods: 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.
Results: 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.
Conclusions: 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.