Abstract 2580: Induction of estrogen receptor alpha by GW9662 sensitizes mammary glands to tamoxifen treatment in organ culture

Peroxisome proliferator-activated receptor gamma (PPARδ) are ligand activated nuclear receptor and binds to natural and synthetic ligands. Earlier we had reported that PPARδ agonist troglitazone inhibited the development of precancerous lesions induced by DMBA in mouse mammary gland organ culture (MMOC). In the present study we evaluated the effects of PPARδ agonist GW7845 and antagonist GW9662 on the development of 7,12 dimethylbenz(a)anthracene (DMBA)-induced mammary alveolar lesions (MAL) in ER negative mammary glands in MMOC. The results showed that both GW7845 and GW9662 inhibited development of ER- MAL in MMOC. Since PPARδ and ER cross talk has been reported in the literature, we determined the effects of GW9662 on the induction of ER and PR in this model. Real-time PCR studies and immunohistochemical analyses showed that GW9662 induced ERα in the absence of estradiol, whereas GW7845 did not induce ERα under these conditions. Both GW7845 and GW9662 failed to suppress mRNA expression of PPARδ in the mammary glands that are otherwise ER negative. However GW9662 suppressed the expression of PPARδ response genes adipsin and aP2. Conversely, GW7845 an agonist of PPARδ enhanced the expression of aP2 and adipsin. These results suggested that the effects of these agents are mediated by PPARδ in MMOC. Finally, Tamoxifen does not inhibit MAL in MMOC, however sequential treatments with GW9662 followed by Tamoxifen suppressed development of DMBA-induced MAL in these glands. Since the ER negative breast cancer patients are generally not treated with SERM, inducing ERα in the mammary cells by GW9662 possibly could make them responsive to Tamoxifen or other SERM. [This work was supported by N01 CN433303] Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2580. doi:1538-7445.AM2012-2580