PD01: Kidney Cancer: Basic Research & Pathophysiology I
PD01-07: The Tumor Suppressor FLCN Regulates the Warburg Effect in Renal Cell Carcinoma through Inhibition of Lactate Dehydrogenase-A
Friday, May 13, 2022
8:00 AM – 8:10 AM
Location: Room 252
Mark R Woodford, Rebecca A Sager*, Sarah J Backe, Fiza Hashmi, Priyanka Kancherla, Alexandr Pinkhasov, Syracuse, NY, W Marston Linehan, Bethesda, MD, Dimitra Bourboulia, Gennady Bratslavsky, Mehdi Mollapour, Syracuse, NY
Introduction: Germline mutations in the tumor suppressor folliculin (FLCN) lead to development of Birt-Hogg-Dubé syndrome, which predisposes patients to development of renal cell carcinoma (RCC). Although FLCN has been linked to many signaling pathways, the exact mechanism of its tumor suppressive function remains elusive. RCC is characterized by reliance on aerobic glycolysis, a phenomenon known as the Warburg effect. Hyperactivity of the glycolytic enzyme lactate dehydrogenase-A (LDHA) drives this process. Previously, FLCN loss had been shown to lead to increased LDHA activity. The objective of this study was to investigate whether FLCN served as an endogenous protein inhibitor of LDHA activity and therefore the Warburg effect.
Methods: FLCN-LDHA interaction and FLCN-mediated inhibition of LDHA activity were examined using a variety of in vitro and cell-based binding and enzymatic activity assays. Synthetic FLCN peptides were generated to identify the required interacting region and mechanism of inhibition. Extracellular acidification was measured to determine the effect of FLCN on glycolysis. The ability of FLCN peptide to accumulate in tumor tissue and inhibit LDHA was examined in ex vivo treated tumor samples from a patient with BHD. FLCN peptide treatment induced apoptosis was also analyzed in RCC cell lines using flow cytometry and Western blot analysis.
Results: FLCN binds to and specifically inhibits the activity of LDHA. A ten amino acid region of FLCN was identified that inhibits LDHA and thereby regulates glycolysis. FLCN was found to be dissociated from LDHA in renal cell carcinoma cells and these cells demonstrated hyperactive LDHA. Hyperactive LDHA present in renal tumor from a patient with BHD was inhibited following ex vivo tissue treatment with FLCN peptide. Additionally, treatment with FLCN peptide led to induction of apoptosis in RCC cells.
Conclusions: The tumor suppressor FLCN functions as an endogenous inhibitor of LDHA. Loss of this inhibition leads to LDHA hyperactivation and metabolic shift in RCC. FLCN peptide can effectively inhibit LDHA and lead to apoptosis in RCC cells. FLCN-mediated inhibition of LDHA provides a new paradigm for the regulation of glycolysis.
Source of Funding: This work was supported by the funds from SUNY Upstate Medical University, Upstate Cancer Center and the Upstate Foundation (M.M.).