Effect of p53 status on sensitivity to platinum complexes in a human ovarian cancer cell line

Wild-type p53 is frequently mutated in late-stage ovarian cancer and has been proposed as a determinant of cisplatin chemosensitivity. We have therefore established a human ovarian cancer cell line differing only in p53 status and characterized its response after treatment with different platinum complexes. The wild-type p53-expressing cell line A2780 was stably transfected with HPV-16 E6 (E6) or an empty vector (VC) as control. Parental A2780 and VC had similar cisplatin sensitivities, whereas E6 was 3- to 4-fold more sensitive as measured by sulforhodamine B and clonogenic assay. E6 was 2- to 3-fold more sensitive to transplatin and the novel cisplatin analog ZD0473 than VC, whereas the trans-platinum analog JM335 was approximately equitoxic. Platinum uptake was similar for all of the cell lines after cisplatin. The removal of platinum-DNA adducts, as measured by atomic absorption spectroscopy, was reduced in E6 compared with VC after cisplatin but similar after JM335. After 10 mu M cisplatin, the G(1) population (0-96 h) was reduced in E6 cells compared with VC, whereas the S phase (8-48 h) and G(2) phase (48-96 h) were increased. Similar proportions of VC and E6 cells died by apoptosis, as detected by annexin V binding, but more E6 cells died by necrosis relative to VC. Our results suggest that the loss of functional p53 can increase cisplatin cytotoxicity in A2780, with loss of G(1)/S checkpoint control and decreased cisplatin-DNA adduct repair, but these effects can be circumvented by the use of JM335, which forms different DNA-platinum adducts.