CD44 VARIANT EXPRESSION AND ESTROGEN-RECEPTOR STATUS IN BREAST-CANCER

To understand the relationship between CD44 gene expression and an est ablished variable associated with aggressive behaviour in human breast cancer, we have studied a panel of 6 breast cell lines and 40 breast tumors selected primarily on the basis of estrogen receptor (ER) statu s. CD44s (standard form) mRNA was assessed by semi-quantitative RT-PCR , and CD44 variants incorporating exon v7 or v10 were studied by RT-PC R and Southern blot. While CD44 expression was not influenced by estro gen in ER+ve MCF-7 cells, CD44s expression was slightly higher (up to 2 fold) in ER-ve cells but there was a marked decrease in the range of CD44 variants incorporating exons v7 or v10. In microdissected tumors , the levels of CD44s showed no correlation with ER status but the pat tern of expression of larger forms of CD44 incorporating variant exons v7 and v10 was significantly different (p = 0.005 and p = 0.015, resp ectively) between ER+ve and ER-ve tumors, reflecting the pattern seen in the cell lines. These findings suggest that the profile of CD44 exp ression in breast cancer may reflect cellular differentiation as indic ated by the ER phenotype. The influence of these differences in CD44 e xpression on the increased metastatic potential of ER negative breast cancer remains to be determined.