Evaluation of cross-resistance between responses to cisplatin, hyperthermia, and radiation in human glioma cells and eight clones selected for cisplatin resistance.

Human glioma cells were exposed to stepwise increasing concentrations of cisplatin and given a final, acute, high concentration treatment of cisplatin. From the surviving cells, eight cisplatin resistant clones were selected. These clones demonstrated a range of cisplatin sensitivities that were retained in the absence of cisplatin when cells were continually passaged. These cells were tested for cross-resistance to radiation and hyperthermia at 42 and 45 degrees C. The data showed that seven of the eight clones were also more radioresistant than the parental line, while one was more radiosensitive. The degree of cisplatin resistance was not related to the degree of radiation resistance. For hyperthermia at 42 and 45 degrees C, some of the clones were slightly more resistant than the parental line, while one clone was much more sensitive. This was not the same clone that was radiosensitive. In conclusion, there was no direct correlation between cisplatin resistance, radiation resistance, and hyperthermia response, although some of the clones were resistant to all three treatments.