Radiation and heat sensitivity of cells from two slowly growing human melanoma xenografts.

The radiation and heat sensitivity of cells from two melanin-rich, slowly growing human melanoma xenografts (B.E. and R.A.) were studied. The volume-doubling times of the xenografts in the volume range 200-500 mm3 were found to be 22.5 47.5 days (B.E.) and 25.3-39.2 days (R.A.). The cells were suspended in culture medium during irradiation or heating, and the colony forming ability of the cells was assayed in soft agar. The X-ray survival curve parameters were found to be: Do = 1.09 +/- 0.14 Gy, Dq = 1.99 +/- 0.58 Gy (B.E.); Do = 1.23 +/- 0.08 Gy, Dq = 2.03 +/- 0.35 Gy (R.A.). The Do-values of the heat survival curves were found to be 119.0 +/- 26.6 min (42.5 degrees C), 20.4 +/- 3.9 min (43.5 degrees C) and 9.6 +/- 1.6 min (44.5 degrees C) for the B.E. melanoma and 112.9 +/- 13.3 min (42.5 degrees C), 17.9 +/- 2.0 min (43.5 degrees C) and 7.7 +/- 0.5 min (44.5 degrees C) for the R.A. melanoma. Both the radiation and the heat sensitivities of the cells are within the range of sensitivities reported for rapidly growing melanoma xenografts, suggesting that the intrinsic radiation and heat sensitivity of tumour cells are not strongly related to the rate of tumour growth prior to treatment.