Induction of apoptosis by the bis-Pt(III) complex [Pt 2(2-mercaptopyrimidine) 4Cl 2

Abstract

We analyzed both the cytotoxicity and the type of cell death produced by the novel binuclear Pt(III) compound Pt-Spym ([Pt 2(2-mercaptopyrimidine) 4Cl 2]) in kidney human fibroblasts and in human tumor cell lines (HeLa, CH1, CH1 cisR and HL-60). The data showed that Pt-Spym displayed higher cytotoxicity against these tumor cells than cisplatin. In contrast, Pt-Spym had low toxicity against normal human fibroblasts. Interestingly, Pt-Spym circumvented cisplatin resistance in CH1 cisR cells. We also observed that Pt-Spym induced the characteristic changes attributed to apoptosis in cells with normal levels of p53 protein (CH1 and CH1 cisR) and with low levels of p53 protein (HeLa), but not in cells lacking p53 (HL-60). Interestingly, Western blot data indicated that apoptosis induction by Pt-Spym in HeLa, CH1, and CH1 cisR cells was not associated with drastic changes in p53 levels. However, cis-DDP strongly decreased p53 levels in CH1 and CH1 cisR cells and abolish p53 protein in HeLa cells. Altogether, these results suggest that induction of apoptosis by Pt-Spym requires the presence of p53 protein.