Expression of hsp90 and cyclin D1 in human breast cancer

The integral roles of heat shock proteins (hsps) in the cell cycle and in multistep processes leading to tumorigenesis have been implied. We examined the expression of hsp90α, hsp90β and cyclin D1 in human breast cancer. Levels of mRNAs coding for hsp90α and cyclin D1 were significantly higher in cancer tissues than in non-cancer tissues. Moreover, there was a close relationship between the extent of the two mRNA levels, suggesting that increased expression of hsp90α, an isoform of the hsp90 family, is associated with the proliferation of human breast cancer. Hsp90β was expressed in cancer cells, but not associated with cell proliferation.