Abstract

Comparison of the heat sensitivity and radiosensitivity of four human melanoma cell lines in culture revealed a large variation in sensitivity amongst the four cell lines. Three of the four cell lines had large shoulders on the survival curves when exposed to hyperthermia (44 degrees C or 45 degrees C). These three cell lines also had demonstrable shoulders on the acute radiation dose response curves. The most radiosensitive cell line did not show a shoulder region in the heat or radiation survival curves (HT-144, Dq = 0.2 Gy). Despite this consistency in the presence or absence of shoulder, there was no correlation between heat and radiation sensitivity in the four melanoma cell lines. Furthermore, regardless of radiosensitivity, all four lines studied showed competent repair of potentially lethal damage. The recovery ratios at a surviving fraction of 0.001 ranged from 5.7 to 7.6. All four lines had a similar cell cycle distribution at the time of treatment, hence the variation observed in the response of these four lines to radiation and heat was not due to differences in cell cycle kinetics. Preliminary results of DNA polymerase-alpha and -beta activities do not demonstrate a clear correlation between cellular levels of these two enzymes and radiosensitivity.