EFFECTS OF TEMPERATURE ON THE INTERACTION OF CISPLATIN AND CARBOPLATIN WITH CELLULAR DNA

Increased levels of cisplatin (cDDP)- and carboplatin (CBDCA)-DNA addu cts were detected in cDDP (10 muM)- and CBDCA (6 mM)-treated CC531 cel ls when the temperature was raised from 37-degrees to 43-degrees. In t he case of cDDP, increased DNA adduct formation was already detectable at 38.5-degrees; additional temperature steps led to further increase s in DNA modification. Increased CBDCA-DNA adduct formation was observ ed only at temperatures higher than 40-degrees. In vitro studies on th e interaction of CDDP and CBDCA with isolated salmon sperm DNA, howeve r, demonstrated no significant differences in the DNA binding rate bet ween 37-degrees and 43-degrees for cDDP and a minor effect for CBDCA o nly at 43-degrees, almost totally excluding a direct temperature effec t on DNA platination in this temperature range. Furthermore, neither t he stability of the formed platinum-DNA adducts nor the rate of adduct loss in CC531 cells was changed at higher temperatures. The observed difference in cellular adduct formation, however, could be related to increased uptake of cDDP and CBDCA into CC531 cells at higher temperat ures. In the case of cDDP, a temperature shift from 37-degrees to 38.5 -degrees resulted in a significantly higher intracellular platinum con centration (0.03 +/- 0.01 vs 0.071 +/- 0.021 mug platinum/10(6) cells, respectively); for CBDCA, temperatures greater-than-or-equal-to 41.5- degrees were needed to increase the platinum concentration significant ly above 37-degrees values (0.3 +/- 0.1 vs 0.6 +/- 0.1 mug platinum/10 (6) cells, respectively). In addition, the increase in DNA adduct form ation of cDDP and CBDCA at elevated temperatures was comparable with t he increase in cDDP-DNA adducts after a cDDP concentration escalation at 37-degrees, indicating a concentration-dependent increase in cDDP-D NA adducts. It seems that heat affects primarily the cellular uptake o f cDDP and CBDCA and not their covalent binding to DNA.