Inconstant association between 27-kDa heat-shock protein (Hsp27) content and doxorubicin resistance in human colon cancer cells. The doxorubicin-protecting effect of Hsp27.

To investigate the role of the small 27-kDa heat-shock protein (Hsp27) in the intrinsic resistance of colon cancer cells to doxorubicin, we modified Hsp27 expression either genetically by transfection or pharmacologically by cisplatin treatment. HT-29 cells were transfected with a full-length Hsp27 construct in the sense or antisense orientation. We found a good correlation between cell survival after doxorubicin treatment and Hsp27 content. A similar correlation was found for the thermoresistance of the Hsp27-transfected cells. In contrast, the sensitivity of the different transfected cells to 5-fluorouracil was not modified. cis-Platinum(II)diammine dichloride (cisplatin) treatment of HT-29 or Caco2 cells dramatically increased their Hsp27 mRNA and protein content. Accordingly, the cells became thermoresistant. Contrary to what has been previously assumed, however, cell resistance to doxorubicin was reduced. Our data suggest that the decreased resistance of the cells to doxorubicin may be due to a concomitant increase of topoisomerase II expression, the main target of anthracyclines. In conclusion, although Hsp27 seems to participate in the natural resistance of colon cancer cells to anthracyclines, its increase after cisplatin treatment is not associated with a decreased cytotoxicity to doxorubicin.