Specific regulation of HSPs in human tumor cell lines by PSK

Substantial progress has been make in elucidating the biochemical properties of HSPs (Heat Shock Proteins) as molecular chaperones in protein biogenesis and their roles in thermoprotection and cytoprotection against cellular insults. Recently, besides advantageous cellular functions, the detrimental role of HSPs has been implicated in a variety of diseases. HSP47 is assumed to be a collagen specific molecular chaperone and its involvement in the progression of fibrosis was observed. There have been a number of reports that suggest the role of HSP60 as an autoantigen in a variety of autoimmune diseases. PSK, a protein-bound polysaccharide, is a biological response modifier that is clinically used for the treatment of cancer patients in Japan. PSK shows a broad range of biological effects in addition to the antitumor activity. In this study, we evaluated the effect of PSK on the expression of HSPs in human tumor strains at the protein and mRNA levels. PSK was observed to suppress the expression of HSP47 and HSP60 but not HSP72/73 in human tumor cell lines. Thus, the novel pharmacological potential of PSK was suggested in the diseases derived from the aberrant expression of HSPs.