Abstract 2863: Mechanisms underlying estrogen-induced inflammation in estrogen-deprived breast cancer cells

Abstract

Abstract Inflammation is critical for estrogen (E2) to undertake apoptosis in E2-deprived breast cancer cells. However, it remains unclear how E2 induces inflammation. Here, we demonstrate that E2 increases lipid metabolism and accumulates unfolded proteins in the endoplasmic reticulum in E2-deprived breast cancer cells. These two major alterations result in different inflammatory responses. E2 rapidly increases lipid metabolism related genes such as fatty acid desaturase 1 (FADS1) and CCAAT/enhancer binding protein beta (CEBPB) to modulate adipose inflammation related factors, e.g. IL6/IL6R after two hours treatment, which regulate the cellular proliferation or differentiation. Simultaneously, accumulation of the unfolded protein activates unfolded protein response (UPR) sensors, protein kinase RNA-like endoplasmic reticulum kinase (PERK) and inositol-requiring protein 1 alpha (IRE1α) within few hours after exposure to E2. Importantly, inhibition of PERK, rather than IRE1α, is able to completely prevent E2 from induction of late event inflammatory genes associated with apoptosis, such as tumor necrosis factor (TNF) superfamily members, BCL2L11 (Bim), and HMOX1,which are activated by E2 after 48 hours. Consistently, nuclear factor-kappa B (NF-κB) is activated when TNFα is maximal after E2 treatment. Further examination revealed that an anti-inflammatory agent, dexamethasone (Dex), activates glucocorticoid receptor (GR) transcriptional activity and blocks E2-induced apoptosis. These effects can be reversed by the knockdown of GR. A notable mechanistic change is that Dex effectively blocks the phosphorylation of PERK and produces equivalent inhibitory effects on the apoptosis-associated inflammatory genes as the PERK inhibitor. However, Dex has an additional potential to activate lipid metabolism and are additive with E2 to elevate FADS1 and adipokine IL6/IL6R. All of these data, for the first time, describe the mechanisms underlying E2-induced inflammation in E2-deprived breast cancer. It provides important information to restrict the clinical use of glucocorticoids, which will undermine the beneficial effects of E2-induced apoptosis in estrogen deprived breast cancer patients. Citation Format: Ping Fan, Fadeke A. Agboke, Amit Kumar Tyagi, V. Craig Jordan. Mechanisms underlying estrogen-induced inflammation in estrogen-deprived breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2863.