Combined effect of trans-diamminedichloroplatinum(II) and hyperthermia on murine and human tumor cells.

trans-Diamminedichloroplatinum(II), a paradigm of an inactive platinum compound, exhibited cytotoxic effect against HEP-2 human tumor cells, TA3Ha murine tumor cells, and freshly collected human ovarian carcinoma cells when combined with hyperthermia (43 degrees, 30 min). The heat treatment reduced the D0 of trans-platinum from 56 to 16.5 micrograms/ml in the HEP-2 system and from an undeterminable value at 37 degrees to 8.2 micrograms/ml in the TA3Ha system. Heat treatment before trans-platinum was more cytotoxic than that after trans-platinum in the TA3Ha system (P less than 0.001). TA3Ha cells treated in vitro with 40 micrograms/ml TDDP at 43 degrees failed to form tumors in mice upon subcutaneous implantation into the tails of mice. In contrast, these agents given singly did not alter the tumor-forming ability of TA3Ha cells. In vivo administration of trans-platinum after hyperthermia (43 degrees for 30 min) retarded the growth of TA3Ha tumors compared to either treatment alone. trans-Platinum did not form detectable DNA-interstrand cross-links in the HEP-2 cells treated at 37 degrees or 43 degrees. However, the DNA-protein cross-links were detectable under these conditions. The frequencies of DNA-protein cross-links were higher in the cells treated at 43 degrees than in those treated at 37 degrees, both immediately after and 12 h after the treatment with trans-platinum. Heat alone did not induce the formation of either DNA-interstrand or DNA-protein cross-links. Heat treatment did not appear to enhance the entry of trans-platinum into the cells.