Abstract 823: Combination therapy of HDAC inhibitors with HSP90 and TRAP1 targeting the hypoxia pathway in triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is one of the deadliest subtypes of breast cancer that more than 50% of cases present with hypoxia, which induces chemotherapy resistance and fuels treatment failure. While various therapies targeting components of the hypoxia signaling cascade have been identified, those focusing on specific targets often fail to produce lasting clinical responses. Therefore, there is a critical need for novel hypoxia inhibitors that combine potency, specificity, low toxicity, and favorable druggability. In this study, we evaluated the efficacy of novel drug combinations involving Heat Shock Protein 90 inhibitor (HSP90i) NDNB-25, Tumor Necrosis Factor Receptor-Associated Protein 1 inhibitor (TRAP1i) NDNT-34, and histone deacetylase inhibitors (HDACis) such as CAY10603, suberoylanilide hydroxamic acid (SAHA), and Valproic acid (VPA). The goal was to suppress the hypoxia pathway in TNBC and assess impacts on cell viability, metastasis, and hypoxia-related gene expression using 2D and 3D TNBC models. Our results demonstrated a strong synergistic effect of SAHA/NDNB-25 and SAHA/NDNT-34 combination therapies. Specifically, NDNB-25/SAHA combination significantly down-regulated HIF1A expression in 2D- cultures. While NDNB-25 and NDNT-34 mono-therapies only reduced HIF2A and TRAP1 expression, the NDNB-25/NDNT-34 combination down-regulated HIF1A, HIF2A, VEGFA, TRAP1, and HSP90 in 3D cultures. Moreover, the NDNB-25/NDNT-34 combination, at lower concentrations (250 nM and 5 µM), inhibited cell migration more effectively than mono-therapies at higher concentrations (500 nM and 10 µM). Fluorescent imaging revealed more distribution of hypoxia signals using a labeled hypoxia probe and the localization of TRAP1i, tagged with rhodamine B, in TNBC-derived mammospheres compared with luminal subtype. These findings suggest that combining epi-drugs and targeted therapies to modulate the hypoxia pathway could inform the development of innovative clinical strategies against TNBC. Citation Format: Golnaz Asaadi Tehrani, Becca Kubick, Andrew Gutierrez, Terin D'Amic, Hailey Sanders, Brian Blagg, Bradley Smith, Meenal Datta. Combination therapy of HDAC inhibitors with HSP90 and TRAP1 targeting the hypoxia pathway in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 823.