Tumoral expression of BRCA1, estrogen receptor alpha and ID4 protein in patients with sporadic breast cancer.

Introduction: BRCA1 expression is downregulated in a third of sporadic breast cancers (SBC). Most of the tumors in which BRCA1 function is diminished do not express estrogen receptor alpha (ER). Recent studies suggest that the inhibitor of DNA binding (ID)-4 could participate in the hormonal regulation of BRCA1 expression.