Abstract 5496: Glutaminase inhibition induces replication stress in ovarian cancer cells and inhibition of replication checkpoint causes synthetic lethality

Abstract

Abstract Ovarian cancer (OC) is a highly aggressive disease and the most lethal gynecologic malignancy in women. Although the majority of OC patients respond to chemotherapeutic drugs, more than 70% of the patients relapse and die as a result of chemoresistance. Therefore, novel therapeutics are warranted to prevent chemoresistance and treat the relapsed disease to improve prognosis. Many cancer cells depend on Glutamine as major carbon source and these cells have high Glutaminase (GLS) expression, an enzyme that converts Glutamine to Glutamate. Chemo-resistant OC cells have elevated levels of GLS, which confirms their increased dependency on glutamine metabolism. Based on these observations, we postulated that GLS inhibition may attenuate the aggressive growth of GLS high OC cells and may sensitize to the agents that can further potentiate these effects. Interestingly, GLS inhibition using a clinical-stage drug CB839 caused replication stress and activated DNA damage checkpoint protein 1 (CHK1) mediated cell cycle arrest. These novel findings suggested a role for CHK1 in protecting GLS inhibition-induced DNA damage by facilitating the timely repair of DNA breaks. Based on these observations, we hypothesized that GLS inhibition in combination with CHK1 inhibition may cause synergistic lethality in chemo-resistant and GLShigh OC cells. We evaluated the combination of GLS inhibitor CB839 and CHK1 inhibitor Prexasertib. Our results demonstrate that GLS inhibition-induced CHK1 phosphorylation is significantly attenuated by Prexasertib treatment. Similarly, combined treatment of CB839 and Prexasertib showed significantly elevated levels of DNA damage as measured by COMET assays, replication stress-mediated DNA damage responses, and synergistic OC cell lethality compared to individual drug treatments. Furthermore, CB839 and Prexasertib combination was more synergistic in cells that expressed high GLS compared to low GLS-expressing OC cells indicating the specificity of the combination of these drugs. Together, our studies identified a novel connection between metabolic and DNA damage checkpoint pathways in OC and propose a novel synergistic lethality-based combination therapy to treat chemo-resistant and aggressive OC. Citation Format: Pamela Luna, Ganesh Acharya, Damieanus Ochola, Swetha Peddibhotla, Chinnadurai Mani, Mark B. Reedy, Komaraiah Palle. Glutaminase inhibition induces replication stress in ovarian cancer cells and inhibition of replication checkpoint causes synthetic lethality. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5496.