Heat treatment of hepatocellular carcinoma cells: Increased levels of heatshock proteins 70 and 90 correlate with cellular necrosis

Immunotherapy, i.e. stimulation of the body's immune response against tumor cells, is a promising approach in cancel treatment. In this context, heat shock proteins (HSP) have been shown to function in tumor antigen chaperoni ng. HSP are evolutionarily conserved and show increased expression in respo nse to chemical and physical stress. Two members of the HSP family, NSP 70 and 90, seem to further act as immuno-stimulating agents because of their p ossible involvement in tumor antigen presentation. We cultured the human he patocellular carcinoma cell line HepG2 and investigated its HSP content und er normal and hyperthamic conditions. Flow cytometry showed increased level s of HSP 70 and 90 after heat shock at 41.8 degreesC for 60 minutes, measur ed after a subsequent incubation time of five hours, as compared to untreat ed cells in vitro. We further observed a clear correlation between the HSP 70 and 90 levels and the necrotic cell subpopulation in heat shocked tumor cells. We conclude that HSP expression in HepG2 cells can be enhanced by he at shock treatment in vitro. We suggest that this mechanism can be exploite d in increasing tumor immunogenicity.