A possible divergent role for the oestrogen receptor alpha and beta subtypes in clinical breast cancer

We have examined the relative levels of oestrogen receptor beta (ER beta) m RNA in 94 breast cancer specimens using a semi-quantitative RT-PCR procedur e. We correlated its expression with ER alpha and various clinical, patholo gical and biochemical features of the disease. The level of ER beta mRNA ex pression in these samples was found to be much lower than ER alpha. Althoug h ER alpha mRNA species were found to be most frequently associated with hi stological grade I and II tumours, displaying tubular differentiation, low grades of nuclear pleomorphism and low mitotic activity, such features were not characteristic of ER beta positive samples. Indeed, application of the Spearman rank correlation test revealed that there was an inverse associat ion between ER beta normalised levels and ER alpha protein HScore. Also ER beta mRNA positive cancers were more frequently EGFR protein positive than their negative counterparts (p = 0.016). a feature normally associated with endocrine-insensitive disease. Our data suggest that although ER beta leve ls are most likely lower than ER alpha, they may influence the biological b ehaviour of breast cancers containing low levels of ER alpha. (C) 2000 Wile y-Liss, Inc.