Session: PD17: Kidney Cancer: Basic Research & Pathophysiology II
PD17-01: The Impact of Loss and Mutation of Mitochondrial DNA on Oncometabolite Accumulation in Patient-Derived Fumarate Hydratase-Deficient Renal Tumor Cell Lines
Introduction: Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant cancer syndrome characterized by mutations in the fumarate hydratase gene (FH). We recently reported the discovery of mutations and loss of mitochondrial DNA (mtDNA) in FH-deficient renal tumors and tumor-derived cell lines. Mitochondrial alterations in FH-deficient tumor-derived cell lines ranged from inactivating mutations in mitochondrial Complex I and Complex III subunits to complete loss of mtDNA in two tumor cell lines. The goal of the present study was to characterize the impact of mtDNA mutations on the oncometabolites fumarate and succinate in FH-deficient renal tumor cell lines. Methods: We performed stable isotope-resolved metabolomics (SIRM) with 13C5,15N2-glutamine tracer on five FH-deficient patient-derived tumor cell lines, and utilized ion chromatography coupled with ultra-high resolution Orbitrap-based mass spectrometry (UHR-ICMS) and NMR spectroscopy to determine the abundance and isotopic labeling pattern of fumarate and its precursors in polar extracts obtained from the tumor cells. Results: We found that several of the FH-deficient tumor cell lines showed elevated succinate levels, with a 13C labeling pattern that was consistent with oxidative production of succinate from glutamine. In contrast, fumarate 13C labeling patterns in these same cell lines was consistent with reductive carboxylation of glutamine and formation of fumarate from the urea cycle and purine biosynthesis, suggesting a deficiency of succinate dehydrogenase (Complex II) activity in the cells. UHR-ICMS analysis of FH-/- cells labeled with 13C1-glutamine confirmed 13C labeling of the purine biosynthetic intermediate adenylosuccinate via reductive carboxylation of glutamine, giving rise to 13C1-fumarate, and this 13C label was localized to the carboxylate carbon of fumarate using an HMBC NMR experiment. Conclusions: We have uncovered additional lesions in the TCA cycle in patient-derived HLRCC cell lines, giving rise to accumulation of the oncometabolite succinate. These data highlight the metabolic heterogeneity that is observed in genetically-defined human tumors. SOURCE OF Funding: NIH NIH MRSP
