INTRATUMORAL HETEROGENEITY FOR HSP90-BETA MESSENGER-RNA LEVELS IN A BREAST-CANCER CELL-LINE

BC-3A and BC-61 are two breast cancer cell lines that have been cloned from parental 8701-BC cells and exhibit different biosynthetic, proli ferative, and invasive properties in vitro. In the attempt to search w hether alterations in the profiles of gene expression could be detecte d, we have submitted both cytotypes to identification of differentiall y expressed cDNAs. In addition, steroid hormone receptor mRNA arrays a nd in vivo tumorigenesis of the two lines have been checked. The techn ique used allowed identification of changes in the expression of the 9 0-kD heat shock protein-beta (hsp90 beta) which is prominently down-re gulated in BC-61 cells. Because we have also found that these cells, w hich lack estrogen receptor mRNA synthesis, display a more invasive be havior in vitro and increased tumorigenesis in vivo, we propose that e valuation of hsp90 beta transcript levels may be taken into considerat ion for screening as a novel molecular marker of breast cancer progres sion.