Heterogeneous patterns of constitutive and heat shock induced expression of HLA-linked HSP70-1 and HSP70-2 heat shock genes in human melanoma cell lines

The heat shock response, which is characterized by the induction of heat shock proteins, is known to affect the ability of tumour cells to cope with potentially adverse conditions such as hypoxia, glucose starvation and cytotoxic immune reactions. To assess the heat shock response of melanoma cells, spontaneous and heat shock induced expression of heat shock proteins was analysed in a panel of 17 human melanoma cell lines. Constitutive expression of HSP27, HSP70, HSC70, HSP90alphabeta and GRP94 proteins was found in all the melanoma cell lines, and HSP70 and HSC70 were also induced by heat shock. The major heat inducible HLA-linked HSP70-1 and HSP70-2 genes were analysed at the mRNA level. Basal expression and inducibility varied between the different melanoma cell lines. In addition, in situ hybridization demonstrated heterogeneous expression of these genes among single cells of a given cell line. In general, each melanoma cell line appears to exhibit an individual type of HSP70 expression that might reflect selection during tumour progression and therapy.