Abstract 3069: Targeting lactic acid sensing GPR132 in ccRCC
Authors: Wang Dazhi 
Published: March 2024

Abstract
Clear cell renal cell carcinoma (ccRCC) is the most common and aggressive subtype of kidney cancer, accounting for 70-80% of the cases. Despite the improvements in tumor therapeutics, patients with metastatic clear cell tumors still have a five-year survival rate lower than 10%. Most of the ccRCC tumors harbor loss of VHL tumor suppressor gene on chromosome 3, leading to constitutively stabilized HIF, activation of downstream pathways involved in glycolysis, angiogenesis and metastasis and a highly acidic, vascularized, and immunosuppressive tumor microenvironment (TME). Such molecular alterations lead to the buildup of lactic acid within the tumor microenvironment. Long has been considered as a byproduct of hypoxic tumor metabolism, but recent studies have demonstrated a pro-tumorigenic role of lactic acid. Therefore, elucidating the molecular mechanisms on how tumor cells take advantage of lactic acid can identify potential novel therapeutic options. To understand how ccRCC cells sense extracellular lactic acid, I explored the concept of a lactate sensor. The currently known lactate sensors are GPR81 and GPR132. By querying TCGA data, GPR81 is reduced in ccRCC tumors and does not predict patient outcome while GPR132 is elevated in ccRCC tumors compared to normal kidney and demonstrates a strong negative effect on survival. Therefore, GPR132 stands out as a potential lactate sensor in ccRCC with meaningful impact on patient survival. Previously, GPR132 has been shown to be involved in tumor associated macrophage M1 to M2 transition upon lactic acid exposure. However, GPR132 exerts a striking impact on ccRCC tumors. Depleting GPR132 significantly decreased the HIF2α level in multiple ccRCC cell lines, establishing a molecular connection between lactic acid, GPR132 and HIF2α. Furthermore, due to suppressed HIF2α signaling, GPR132 knockout led to decreased lactic acid uptake through MCT1. Such decreased lactic transporter MCT1 abrogated the elevated aggressive phenotype in ccRCC cells when exposed to lactic acid. Metabolically, GPR132 knockout led to decreased lipid deposition. In addition, such deprivation of lipid droplet is not replenished when cells are exposed to lactic acid. Furthermore, by conducting an isotype-tracing experiment, GPR132 knockout actively decreased lactic acid uptake by the tumors and limit their resources to regenerate TCA cycle intermediates and build up lipid droplets. More importantly, GPR132 knockout led to defective mitochondria activities and activation of apoptosis, both of which led to significantly suppressed ccRCC growth in vitro and in vivo. This suggested that GPR132 likely affects ccRCC fitness through multiple layers of signaling mechanisms. Overall, our study has revealed that lactate sensing GPR132 is a critical signaling pathway for ccRCC tumor development in a glycolytic feed-forward context. As a membrane bound receptor, GPR132 holds immense potential as a novel therapeutic target in ccRCC.
Citation Format: Dazhi Wang. Targeting lactic acid sensing GPR132 in ccRCC [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(6_Suppl):Abstract nr 3069.