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 degreesC for 30 min resulted in the vigorous induction of Hsp72, along wit h a less pronounced increase in the rate of synthesis of Hsp90, Hsp60 and H sp 27. Biotinylation of surface-exposed proteins, followed by isolation of biotin-tagged proteins by affinity chromatography, demonstrated that both H sp72 and Hsp60 are expressed on plasma membrane. Membrane expression of the se two Hsps was confirmed by immunoprecipitation of surface biotinylated pr oteins with anti-Hsp72 and anti-Hsp60 specific antibodies. Cytotoxic assays showed that untreated HPC-4 cells are intrinsically resist ant to NK-mediated lysis, while they were efficiently killed by LAK lymphoc ytes, as well as by exposure to TNF alpha. Following heat-treatment, cells became much more resistant to LAK-mediated lysis, while their sensitivity t o NK-mediated lysis and to TNF alpha cytotoxicity remained unmodified.