Different associations of estrogen receptor ß isoforms, ERß1 and ERß2, expression levels with tumor size and survival in early- and late-onset breast cancer.

ABSTRACT

BACKGROUND: In breast cancer, little is known about the consequences of co-expression of ERα with the second estrogen receptor, ERß, and its isoforms in light of their joint prognostic value. Previously reported correlations have been based mostly on independent ERα and ERß expression levels in breast tumors. PURPOSE: To address whether the expression ratio of ERα and ERß and its isoforms may be a more important parameter than their absolute levels, we analyzed relative mRNA expression ratios of ERß1 to ERß2 and ERα in 74 clinical samples of invasive breast cancer including 39 early-onset and 35 late-onset breast cancers. Expression levels were correlated with clinical and histopathological parameters and disease-free interval. RESULTS: A specific correlation of ERß1 expression levels with tumor size was detected in early-onset breast cancer patients and of ERß2 levels with tumor size in late-onset patients. Expression of both ERß isoforms inversely correlated with expression of the two estrogen regulated genes, progesterone receptor and pS2 in both groups. Higher levels of ERß2 than ERß1 isoform were associated with a better outcome in late-onset patients. CONCLUSIONS: Our results suggest that different isoforms of ERß may be involved in suppression of tumor growth in young and elder patients and may have different prognostic values.