Abstract 5641: Role of ceramide synthase 2 in drug-induced ER-stress, Ca2+ release and apoptosis in triple-negative breast cancer cells

Abstract Breast cancer can be classified in five subgroups: Luminal A (ER+/PR+/HER2-), Luminal B (ER+/PR-/HER2- or ER+/PR+/HER2+), ER-/PR-/HER2+, and ER-/PR-/HER2- (triple-negative). Significant progress has been made in the treatment of hormone-responsive and HER2-overexpressing breast cancer; however, the treatment for TNBC is underdeveloped due to lack of appropriate targeting. Further, all subtypes of breast cancer quickly become resistant to the current available therapy. Hence, there is an urgent need to develop a therapeutic strategy that targets a common molecular pathway, irrespective of their biological markers. Recent studies recognized lipid metabolism as one of the important cancer hallmarks. Among many lipids, ceramides play a crucial role in cell signaling, apoptosis, and the regulation of cell growth and differentiation. Very long-chain fatty acid (VLCFA)-ceramides (C20-C26), which are synthesized by ceramide synthase 2 (CerS2), suppress cancer cell invasion and metastasis. The decreased expression of CerS2 is known as a poor prognostic factor for BC patients. The reduction in CerS-2 expression may be due to genetic mutations, epigenetic modifications, or changes in the cellular microenvironment. Thus, the increased level or the activity of CerS2 can be a better prognostic factor for BC patients. In this effort, we have synthesized a novel biisoquinoline-derivative, DH20931 (US Patent ID: US9914733B2) that causes death of breast cancer cells, including TNBC cells. The spatial molecular modeling and enzymatic assays show that DH20931 interacts with and stimulates ceramide synthase 2 (CerS2) activity, reduces the growth of hormone-responsive, HER2-overexpressing, and TNBC cells. DH20931 treatment increases the level of VLCFA-ceramides, induces lipotoxic endoplasmic reticulum (ER) stress, and ATF4/CHOP/PUMA pathway of apoptosis. Here, we show an additional apoptotic pathway that is linked with DH20931-mediated ER-stress. DH20931 induced ER-stress causes the release of Ca2+ from ER to mitochondria, leading to the release of cytochrome c, that in turn leads to significant increase of apoptosis in TNBC cells. We provide evidence that CerS2 plays an important role in the release of Ca2+ from ER to mitochondria where it forms an active IP3R1 channel complex and reduces the distance between ER and mitochondria. Based on Swiss-ADME analysis and laboratory experiments, DH20931 possess all the properties of a druggable molecule and obeys the Lipinski-rule-of-five. Thus, DH20931 can be developed as a novel therapeutic agent that can induce apoptosis by ATF4/CHOP/PUMA axis and Ca2+-dependent pathways, which are independent to ER, PR and HER2 status. The use of this therapy can potentially reduce the morbidity and mortality of women of all races and ethnic groups with BC of hormone-responsive, HER2-expressing, and TNBC. Citation Format: Hissah Alatawi, Haritha Nair, Garrette Timothy, Vulpe Christopher, Sharma Arun, Narayan Satya. Role of ceramide synthase 2 in drug-induced ER-stress, Ca2+ release and apoptosis in triple-negative breast cancer cells [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 5641.