INCREASED PLATINUM-DNA DAMAGE TOLERANCE IS ASSOCIATED WITH CISPLATIN RESISTANCE AND CROSS-RESISTANCE TO VARIOUS CHEMOTHERAPEUTIC-AGENTS IN UNRELATED HUMAN OVARIAN-CANCER CELL-LINES

We have examined a panel of 12 unrelated human ovarian cancer cell lin es derived from patients who were either untreated or treated with pla tinum-based chemotherapy to determine whether a relationship is presen t between cisplatin sensitivity and: (a) cellular platinum accumulatio n; (b) glutathione levels; (c) platinum-DNA adduct formation; (d) plat inum-DNA adduct removal; and (e) platinum-DNA damage tolerance. Multip le regression and correlation analysis revealed that of these resistan ce mechanisms, platinum-DNA damage tolerance correlates strongly with cisplatin sensitivity (r = 0.84, P = 0.001), whereas platinum accumula tion (r = -0.11), cellular glutathione levels (r = 0.13), and platinum -DNA adduct removal (r = 0.44) correlate insignificantly. The correlat ion of platinum-DNA damage tolerance to cisplatin sensitivity (IC(50)s ) is derived from the clustering of platinum-DNA adduct formation into three distinct groups spanning a 3-fold range, which is narrow relati ve to the corresponding 43-fold range in sensitivity. Adduct formation itself is not associated with cisplatin sensitivity (r = -0.38). Stro ng correlations were also observed between platinum-DNA damage toleran ce and sensitivity to Adriamycin (r = 0.80, P = 0.002), paclitaxel (r = 0.87, P = 0.0002), etoposide (r = 0.78, P = 0.003), and mitomycin C (r = 0.73, P = 0.007). These results suggest that the failure of pathw ays that are involved in recognizing and processing platinum-DNA damag e and other types of drug-induced damage that culminate in cell death may result in a broad resistance phenotype.