Modulation of heat shock protein synthesis in two human melanoma cell lines.

Two human melanoma cell lines, largely different from one another in their intrinsic thermosensitivity, were exposed to supranormal temperatures and labeled with 35S-methionine. The protein patterns resolved by SDS-polyacrylamide gel electrophoresis showed in both cell lines an increased synthesis of a unique set of heat shock proteins (HSP) of 72 Kdalton (KD). Already evident after 15 min at 42 degrees C, the relative rate of synthesis of these HSP increased progressively for up to 3 h of continuous heat treatment. The cells exposed for 1 h at 42 degrees C and then returned to 37 degrees C maintained a high relative rate of HSP synthesis for more than 6 h. The rate of decay of the neosynthesized HSP did not differ from that of the overall cell proteins. Since in both cell lines all the parameters concerning HSP induction were identical, no correlation can be established between their intrinsic sensitivity towards the conditioning treatment and the capacity to respond to heat treatment with an increased synthesis of these proteins.