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Abstract Metabolic reprogramming is a hallmark of cancer cells and a key contributor to cancer progression, which is a promising target for cancer therapies. The enhanced glycolysis, also known as the Warburg effect, represents the most widely recognized metabolic alteration in cancer, wherein the majority of cancer cells undergoes reprogramming to heavily rely on glycolysis for their accelerated growth and proliferation. The glycolytic enzyme lactate dehydrogenase A (LDHA) catalyzes the conversion of pyruvate to lactate in the final stage of glycolysis. LDHA is frequently overexpressed in cancers, which plays a critical role in promoting glycolysis and cancer progression. To deepen our understanding of the oncogenic mechanism of LDHA, we screened for LDHA-interacting proteins in human breast cancer cells by liquid chromatography mass spectrometry (LC/MS) analysis. Through this strategy, small GTPase Rac1 was identified as an LDHA-interacting protein. LDHA interacted with the active form of Rac1, Rac1-GTP, and impaired the interaction of Rac1-GTP with its negative regulators, GTPase-activating proteins, leading to Rac1 activation independently of the glycolytic enzyme activity of LDHA. In addition, LDHA overexpression was significantly associated with increased Rac1 activity in clinical breast cancer specimens. Inhibiting Rac1 significantly attenuated the oncogenic effect of LDHA. Combining small-molecule inhibitors targeting LDHA enzyme activity and Rac1 activity displayed a synergistic inhibitory effect on breast cancers with LDHA overexpression in mouse models. Thus, our results revealed a novel and critical noncanonical mechanism of LDHA in promoting cancer progression through its direct interaction and activation of Rac1. Given that LDHA is frequently overexpressed in cancer, LDHA overexpression constitutes an important mechanism contributing to aberrant Rac1 activation in cancer. Importantly, our findings also suggest that pharmacologically targeting LDHA enzyme activity and Rac1 activity simultaneously is a promising strategy to treat breast cancers with LDHA overexpression. Citation Format: Juan Liu, Wenwei Hu, Zhaohui Feng. The noncanonical mechanism of metabolic enzyme LDHA in cancer progression 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 432.
Liu et al. (Fri,) studied this question.