Abstract B003: Increasing branched-chain amino acid metabolism reduces clear cell renal cell carcinoma growth

Abstract

Abstract North America has the highest incidence of renal cancer in the world with the most common subtype being clear cell renal cell carcinoma (ccRCC). Metabolic dysfunction is a hallmark of ccRCC based on molecular analysis and its clear cell histologic appearance due to significant cytoplasmic accumulation of lipid droplets and glycogen. Using publicly available RNA-Seq and proteomic datasets, we identified reduced expression of branched-chain amino acid (BCAA) enzymes BCAA transaminase 2 (BCAT2) and the branched-chain ketoacid dehydrogenase complex (BCKDH) in ccRCC compared to healthy kidney tissue. We validated these results by confirming that BCAT2 and the BCKDH complex are decreased at the mRNA and protein level in ccRCC tumors and cell lines compared to pair-matched normal adjacent kidney tissue. The reduced expression of the BCKDH complex was reinforced at the genome level by copy number loss of BCKDH subunits DBT and BCKDHB, underscoring the selection for suppression of this pathway. Metabolomics analysis then showed that the abundance of BCAAs were decreased in ccRCC tumors. Additionally, public datasets revealed that ccRCC patients presenting low mRNA expression of any of the four BCKDH subunits DBT, BCKDHB, BCKDHA, and DLD have a worse overall survival compared to patients with higher expression. To test if reactivating the BCAA pathway would impact ccRCC growth, I inhibited BCKDK, a kinase that inactivates the BCKDH complex, pharmacologically with BT2 and genetically with shRNA. Multiple ccRCC cell lines demonstrated reduced proliferation due to apoptosis after being treated with shRNA targeting BCKDK. Cell viability could be rescued by the antioxidant N-acetyl cysteine, suggesting loss of BCKDK increased the production of reactive oxygen species (ROS). Flow cytometry showed that knocking down BCKDK increases cellular ROS. Our data reveal that BCAA catabolism is decreased in ccRCC and reactivating the pathway reduces ccRCC growth in vitro by inducing apoptosis through increased production of ROS. This suggests that BCKDK could be a therapeutic target in ccRCC. Citation Format: Nathan J. Coffey, Romain Riscal, Nicolas Skuli, Nicholas P. Lesner, Michael Noji, Christine Jiang, Laura C. Kim, Xu Han, Megan C. Blair, Brian Keith, Zoltan Arany, M. Celeste Simon. Increasing branched-chain amino acid metabolism reduces clear cell renal cell carcinoma growth [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr B003.