Abstract
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 μM cisplatin, the G1 population (0–96 h) was reduced in E6 cells compared with VC, whereas the S phase (8–48 h) and G2 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 G1/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.
Footnotes
- Received July 28, 1999.
- Accepted December 3, 1999.
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Send reprint requests to: Dr. Mike I. Walton, CRC Centre for Cancer Therapeutics, Institute of Cancer Research, E Block, 15 Cotswold Rd., Belmont, Sutton, Surrey, SM2 5NG UK. E-mail:mwalton{at}icr.ac.uk
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This work was supported by the Cancer Research Campaign, UK. K.E.P. is the recipient of an Institute of Cancer Research Ph.D. studentship.
- The American Society for Pharmacology and Experimental Therapeutics
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