Abstract 2100: Novel LIPA targeted therapy for treating inflammatory breast cancer

Abstract Background: Inflammatory breast cancer (IBC) is a rare but incredibly aggressive subtype of breast cancer (BC). IBC accounts for 2-4% of all occurrences of breast cancer and results in 7-10% of breast cancer-related deaths. IBC is only partially treatable with current therapies such as chemotherapy, surgery, and radiotherapy. Identification of novel therapeutic targets is urgently required. The main organelle for the synthesis, folding, and modification of proteins is called the endoplasmic reticulum (ER). Since elevated basal ER stress (ERS) is usually found in many cancers including IBC, our hypothesis was that the high basal ERS in IBC constitutes a serious vulnerability that can be targeted. Recently, we developed a small molecule ERX41 that promotes ER stress by blocking Lysosomal acid lipase A (LIPA) function in ER of cancer cells. The goal of the project is to test the utility of ERX-41 in treating IBC. Methods: To study the effect of ERX-41, we have used three well-established IBC model cells. We evaluated the efficacy of ERX-41 as a novel therapeutic for treating IBC using cell viability assays. The long-term effects of ERX-41 on IBC cell survival were evaluated using colony formation assays. Annexin V assays were used to measure apoptosis. Reporter assays, splicing assays, RT-qPCR, and Western blotting were used in mechanistic investigations. The effectiveness of ERX-41 was examined in vivo using KPL4 cell-based xenografts. Results: ERX-41 significantly decreased the viability of all three IBC model cells (SUM149, SUM190PT, and KPL4), with an IC50 of about 125 nM in MTT assay. Additionally, ERX-41 treatment significantly decreased IBC cells capacity to form colonies and promoted apoptosis. Specificity of the ERX41 mediated actions were confirmed using LIPA KO cells. Using RTqPCR based splicing assays, we demonstrated increased splicing of XBP1 as early as 6 hours after ERX41 treatment. Western analyses showed robust induction of stress markers (CHOP, PERK, ATF4) in IBC cells upon treatment with ERX-41. In KPL4 xenograft studies, ERX-41 showed significant reduction in the tumor volume. IHC analyses confirmed decreased proliferation marker and increased ER stress markers. Conclusions: Collectively, our results suggest that ERX-41 is a novel therapeutic agent that targets the LIPA with a unique mechanism of action and implicate ERX-41 binding to LIPA induces ER stress and promotes apoptosis of IBC cells. Citation Format: Zenaida Fuentes, Rahul Gopalam, Bianca A. Romo, Khaled Mohamed Nassar, Xue Yang, Behnam Ebrahimi, Paulina Ramirez, Chia-Yuan Chen, Scott Elmore, Harika Nagandla, Uday Pratap, Christoforos Thomas, Suryavathi Viswanadhapalli, Jung-Mo Ahn, Ganesh Raj, Ratna K. Vadlamudi. Novel LIPA targeted therapy for treating 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 2100.