Induction and membrane expression of heat shock proteins in heat-treated HPC-4 cells is correlated with increased resistance to LAK-mediated lysis

In human pancreatic carcinoma cells (HPC-4), a hyperthermic treatment at 43 °C for 30 min resulted in the vigorous induction of Hsp72, along with a less pronounced increase in the rate of synthesis of Hsp90, Hsp60 and Hsp 27. Biotinylation of surface-exposed proteins, followed by isolation of biotin-tagged proteins by affinity chromatography, demonstrated that both Hsp72 and Hsp60 are expressed on plasma membrane. Membrane expression of these two Hsps was confirmed by immunoprecipitation of surface biotinylated proteins with anti-Hsp72 and anti-Hsp60 specific antibodies. Cytotoxic assays showed that untreated HPC-4 cells are intrinsically resistant to NK-mediated lysis, while they were efficiently killed by LAK lymphocytes, as well as by exposure to TNFα. Following heat-treatment, cells became much more resistant to LAK-mediated lysis, while their sensitivity to NK-mediated lysis and to TN-Fα cytotoxicity remained unmodified.