Molecular mechanism of anti-tumor effect by heperthermia

Abstract

[Background]

It has been reported that anti-tumor effect is mediated by heating through activating immune system or cellular damage response pathways such as apoptosis. However, a responsible gene or protein for the anti-tumor effect by hyperthermia is little known. We attempted to isolate the responsible factor using various normal or cancer cell lines by proteomics approach. We think that identification of the responsible factor for anti-tumor activity in hyperthermia would lead to development of a drug for patients unsuitable for the treatment.

[Methods]

We compared protein expression pattern between various normal and cancer cell lines in the absence or presence of heat treatment by two-dimensional gel electrophoresis (2DE). After 2DE, we identified heat-specific induced or reduced proteins using liquid chromatography mass spectrometry. Anti-tumor activity of proteins of interest was evaluated by colony-formation assay between cell lines with or without expression of shRNA for genes of interest.

[Results]

We found that a protein kinase was degradated after heat treatment. The protein kinase was not degradated by other stimuli such as X-ray irradiation, anti-cancer drugs, or addition of ceramides. In vitro degradation assay indicated that the protein kinase was cleaved by a proteinase. Moreover, reduced expression by shRNA for the protein kinase suppressed cell proliferation in several cancer cell lines.

[Conclusion]

We identified heat-sensitive protein kinase by proteomics approach. Since this heat-sensitive protein kinase is involved in the regulation of cellular proliferation, this protein might be one of true targets for hyperthermia.