Abstract 1524: The cancer specific intramembrane serine protease RHBDL2 serves as a master regulator of glutamine metabolism and chemoresistance in TNBC

Abstract Glutamine metabolism is critical in cancer, driving cell proliferation and chemoresistance by supporting anabolic processes and energy production. This dependency offers a potential for therapeutic intervention; however, attempts to inhibit glutamine transporters and related enzymes have largely failed due to tumor plasticity, which enables cancer cells to adapt and bypass metabolic blockades. Our studies focus on RHBDL2, a cancer-specific intramembrane serine protease that regulates the glutamine metabolism in triple-negative breast cancer (TNBC).RHBDL2 plays two pivotal roles in glutamine metabolism. First, it binds and stabilizes ASCT2 at the plasma membrane, ensuring efficient glutamine uptake, which is crucial for ATP production and cell proliferation. Second, highlighting RHBDL2 localizes to the endoplasmic reticulum (ER), where it modulates N-glycosylation of ASCT2 by regulating glycosyltransferase activity. This glycosylation is essential for ASCT2 trafficking and stabilization. Collectively, these functions underscore RHBDL2’ pivotal roles in maintaining tumor metabolism of TNBC cells. In addition to regulating ASCT2, RHBDL2 forms complexes with other proteins and transporters involved in glutamine metabolism, enhancing cancer cells’ adaptability to metabolic stress. Our studies reveal that the RHBDL2-ASCT2 complex correlates with poor prognosis in cancer patients. Moreover, RHBDL2 upregulation has been associated with increased chemoresistance in TNBC, identifying it as a critical factor in therapeutic resistance. We successfully develop the RHBDL2 polyclonal antibody, which inhibits tumor growth by reducing glutamine uptake. Building on this, we are now developing monoclonal antibodies designed to disrupt RHBDL2 function, thereby reducing glutamine uptake and restoring chemotherapy sensitivity. This approach has the potential to impair cancer metabolism, suppress tumor growth, and improve outcomes in TNBC patients. Citation Format: Yosuke Matsushita, Kazumasa Okumura, Masato Komatsu, Tetsuro Yoshimaru, Masaya Ono, Mitsunori Sasa, Yasuo Miyoshi, Toyomasa Katagiri. The cancer specific intramembrane serine protease RHBDL2 serves as a master regulator of glutamine metabolism and chemoresistance in TNBC [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 1524.