Abstract 6270: Anti-metastatic effects of estrogen receptor β in inflammatory breast cancer

Abstract Inflammatory breast cancer (IBC) is a rare but highly aggressive form of breast cancer with a 5-year survival rate of less than 50%. Although 20-30% of women with IBC have distant metastasis at the time of diagnosis, the biology underlying the aggressive behavior of the disease is poorly understood and molecular markers that distinguish IBC from non-IBC have not yet been identified. In response to the urgent need of discovering new targeted therapies in IBC, we have studied the second estrogen receptor (ERβ) since prior work from our lab correlated higher tumor expression of ERβ in samples from IBC patients with longer metastasis free survival. We showed that ERβ exerted anti-metastatic activity in IBC by inhibiting actin-based cell migration through the suppression of RhoC GTPase signaling. However, since estrogen receptors elicit their effects by inducing global cellular alterations, we have now adopted an integrated genomic approach to fully understand the anti-metastatic effects of ERβ in IBC and delineate the underlying transcriptional regulatory circuits. We found ERβ binding sites in IBC cells and combined this information with gene expression data to identify downstream direct target genes and associated pathways. Our findings suggest the regulation of tumor micro-environment and metabolism as the primary targets of ERβ and we are currently working to pinpoint the crucial regulatory components in these functions. Our findings thus offer an opportunity to better understand the mechanism of ERβ action in aggressive breast cancer, serving as a critical step in validating its tumor repressive role. Citation Format: Harika Nagandla, Spyros Tastsoglou, Kim Cuong Cap, Aireana Phillips, Wei Qian, Jianying Zhou, Jenny Chang, Savitri Krishnamurthy, Naoto Ueno, Artemis Hatzigeorgiou, Christoforos Thomas. Anti-metastatic effects of estrogen receptor β in inflammatory breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6270.