Abstract 2541: Combined androgen and glucocorticoid receptor (AR/GR) activity drives TNBC progression

Abstract

Abstract Background: A recent effort to distinguish early-stage TNBC based on outcome and to expose driver pathways using gene profiling/cluster analysis divided TNBC into four subtypes- basal-like, mesenchymal, immunomodulatory, and luminal androgen receptor (LAR). The clinical AR+ TNBC subtype (>10% AR by IHC) comprises up to 35% of metastatic disease. The discovery of this TNBC subtype and the concomitant development of potent new anti-androgens for prostate cancer have led to several clinical trials evaluating AR antagonists in TNBC. In parallel, glucocorticoid receptor (GR) expression and activation have been shown to mediate anti-apoptotic gene expression in TNBC. However, to our knowledge, no one has examined the coordinate expression of GR and AR activity and the potential crosstalk downstream of dual GR and AR activation. We hypothesized that AR/GR cooperative gene expression pathways may induce TNBC therapy resistance and tumor progression. Methods and Results: We analyzed GR+ TNBC primary tumor gene expression from TCGA samples and found a wide range of AR expression. To examine whether GR-associated gene expression differed in high versus low AR+ TNBC, we divided TCGA TNBC primary tumors (N=123) at the AR median into “high” versus “low” AR expression. We then identified relative GR target gene expression levels in those genes identified from a previous TNBC meta-analysis. Invasion, motility and proliferation pathways were found to be most significantly expressed among GR-associated genes in AR high TNBC (top 5 significant pathways). Similarly, we found that GR and AR co-activation in AR+ MDA-MB-453 TNBC cells significantly increased cell migration compared to GR or AR activation alone. In addition, when MDA-MB-453 cells were exposed to the AR antagonist enzalutamide (enza) for more than 30 days (long-term, LT), the magnitude of increase in cell migration following GR activation increased, suggesting that increased GR activity may compensate for long-term AR blockade. Furthermore, long-term enza exposure (LTenza) in AR+ MFM-223 and MDA-MB-453 cells resulted in increased GR mRNA and protein levels. The magnitude of GR-mediated target gene expression was also significantly increased in LTEnza versus control-treated cells. In vivo, LTenza-treated MDA-MB-453 xenografts were relatively insensitive to paclitaxel chemotherapy treatment, consistent with increased GR activity compared to control cells. Conclusions: We conclude that coordinate GR and AR expression in TNBC contributes to a particularly poor outcome in TNBC. Downstream AR/GR gene expression favoring cell survival and invasive phenotypes may contribute to this outcome. Consideration of dual AR/GR inhibition in TNBC may increase the effectiveness of anti-androgen therapy. Citation Format: Deniz N. Dolcen, Eva Tonsing-Carter, Ryan Harkless, Caroline Kim, Kathleen Bowie, Gini Fleming, Suzanne Conzen. Combined androgen and glucocorticoid receptor (AR/GR) activity drives TNBC progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2541.