Expression of the forkhead transcription factor FOXP1 is associated with that of estrogen receptorβ in primary invasive breast carcinomas

Abstract

We previously identified a correlation between estrogen receptor alpha (ERα) and the candidate tumour suppressor gene Forkhead Box P1 (FOXP1), whose nuclear protein expression in breast tumours was associated with improved patient survival. However, the expression pattern of FOXP1 in normal breast tissue is more reminiscent of the second receptor, ERβ, which has an emerging role as a tumour suppressor in breast cancer and critically may underlie the ability of some ERα-negative tumours to respond to tamoxifen. In a series of 283 breast cancers, in which ERα-positive tumours were treated with tamoxifen, the nuclear expression of ERβ correlated significantly with ERα (p = 0.004), low-tumour gr..