ABSTRACT: BACKGROUND: Most of breast cancers are considered sporadic and modulation of the two major genes BRCA1 and BRCA2 expressions caused by tissue-specific somatic mutations lead to this pathology. The nutritional intake of phytoestrogens seems to reduce the risk of breast cancer and investigation of their potential as anticancer agents has increased. However, the possible mechanisms and signalling pathways of phytoestrogen action in breast cancer prevention remains unknown. RESULTS: Using Taqman Low Density Array technology, we investigated the BRCA2 loss of function role in sporadic breast cancers and the links existing with soy isoflavones on a panel of nuclear receptor expression. Human breast cell lines (MCF-7, MDA-MB-231, and MCF-10a) were transfected by BRCA2-siRNA and treated with genistein (18.5 muM) or daidzein (78.5 muM) for 72 h. Generating the transitory knockdown of BRCA2 oncosuppressor, we observed different modulations in several nuclear receptor genes such as ER, RAR and RXR, as well as PPARs and VDR according to the studied breast cell line. Additional isoflavone treatments showed different nuclear receptor gene modulation profiles. CONCLUSION: Our results seemed to implicate the oncosuppressor BRCA2 and the phytoestrogen pathways in different nuclear gene expressions via an ER-independent manner.