TY - JOUR T1 - Histone Deacetylase Inhibitors Enhance Retinoid Response in Human Breast Cancer Cell Lines JF - Anticancer Research JO - Anticancer Res SP - 4019 LP - 4024 VL - 24 IS - 6 AU - LAURA EMIONITE AU - FABIA GALMOZZI AU - MYRIAM GRATTAROLA AU - FRANCESCO BOCCARDO AU - LAURA VERGANI AU - SALVATORE TOMA Y1 - 2004/11/01 UR - http://ar.iiarjournals.org/content/24/6/4019.abstract N2 - Solid tumors develop resistance to retinoids during carcinogenesis. One of the strategies to overcome this resistance may include the combination of these molecules with other differentiating, cytotoxic or chromatin-remodelling agents. We analysed the anti-proliferative activity of two histone-deacetylase inhibitors (HDACIs), Trichostatin A (TSA) and sodium phenylbutyrate (PB), alone or combined with retinoids, all-trans retinoic acid (ATRA) and Ro 41-5253, on two human breast cancer cell lines: the hormone-dependent MCF-7 and the hormone-independent MDA-MB-231. These lines responded differently to retinoids: MCF-7 were sensitive, whilst MDA-MB-231 were rather resistant. When the retinoids were combined with HDACIs, these molecules potentiated the retinoid activity on growth inhibition, especially for the association Ro 41-5253 and TSA. By FACS analysis, we observed that the anti-proliferative effects were only partially due to pro-apopotic mechanisms, suggesting a cell-cycle block. The efficacy of the retinoids/HDACIs combinations could represent a new strategy in breast cancer chemotherapy, allowing inhibition of both ER+ and ER- cell populations. Copyright© 2004 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved ER -