Exogenously delivered heat shock protein 70 displaces its endogenous analogue and sensitizes cancer cells to lymphocytes-mediated cytotoxicity

Abstract

Hsp70 chaperone is known to stimulate anti-tumour immunity in a variety of cancer models. Here we demonstrated that the addition of purified recombinant Hsp70 to the culture medium facilitated cancer cell cytolysis by lymphocytes. Importantly, exogenous Hsp70 triggered secretion of the intracellular Hsp70 to a cell surface and extracellular milieu, which played a role in cytolysis because down-regulation of the endogenous Hsp70 reduced both its presence at the cell surface and the lymphocyte-mediated cytolysis. Inhibitors that target both the ATPase and the peptide-binding domains of Hsp70 molecule potently decreased its anti-tumor effect. Using a variety of cell transport markers and inhibitors, we showed that the exchange of exogenous and intracellular Hsp70 is supported by classical and non-classical transport pathways, with a particular role of lipid rafts in the chaperone's intracellular transport. In conclusion, exogenous Hsp70 can eject endogenous Hsp70, thus exerting anticancer activity.

Hsp70 Induction and Anticancer Activity of U-133, the Acetylated Trisglucosydic Derivative of Echinochrome

“…The antibody was earlier found to recognize both cytosolic and membranebound forms of the protein [31]. We found that in full agreement with the data on Hsp70 expression the protein amount after the beginning of incubation with U-133 was grown in cytoplasm and the green speckles appeared in a close proximity to a cell surface (Figures 3a and 3c).…”

The Heat Shock Protein Story—From Taking mTORC1,2 and Heat Shock Protein Inhibitors as Therapeutic Measures for Treating Cancers to Development of Cancer Vaccines

“…That the usage of HSP70 as an anti-cancer drug has passed through the pre-clinical test, as reported in [154]. We refer the readers to other examples taking pure HSPs as anti-cancer drugs in reference [119].…”

“…In particular, injection of pure human recombinant HSP70 caused a remarkable delay in tumor growth and elongation of the survival time of animal models. It was noted also that the therapeutic effect was accompanied by the growth of specific CD4+ and CD8+ T lymphocytes and activation of cytotoxic NK cells [119].…”

“…To study the mechanism behind the anti-cancer effects of HSP70, in vitro experiments were carried out in which C6 glioma or B16 melanoma cells incubated with fluorescently labeled HSP70 being stained with antibody recognizing the TKD-peptide; TKD-peptide is a partial HSP70 sequence capable of stimulating the cytolytic and proliferative activity of NK cells [119]. This study revealed that exogenous HSP70 caused the endogenous HSP70 to be released to the extracellular matrix.…”

“…It has been suggested that either one or all the following processes are at work: 1) a classical, endocytotic pathway, 2) non-classical process involving secretory lysosomal endosomes process [128], 3) via lipid rafts trafficking mechanism [119]. Further research on the details of this particular "HSP replace-P. C. W. Fung, R. K. C. Kong Journal of Cancer Therapy ment" mechanism is necessary.…”