Genomic and Metabolic Hallmarks of SDH- and FH-Deficient Renal Cell Carcinomas

PurposeSuccinate dehydrogenase-deficient and fumarate hydratase-deficient renal cell carcinomas (SDHRCC and FHRCC) are rare kidney cancers driven by loss of metabolically proximal enzymes. We sought to define and compare the genomic and metabolomic hallmarks of these entities. Experimental DesignWe analyzed SDHRCC and FHRCC tumors with either immunohistochemical evidence of loss of protein expression or genomically-confirmed biallelic inactivation of SDHA/B/C/D/AF2 or FH. Somatic alterations were identified using clinical pipelines, and allele-specific copy number changes were identified using FACETS. Mass-spectrometry-based metabolomic profiling was performed on available SDHRCC and FHRCC tumors. ResultsForty two patients were analyzed (25 FHRCC, 17 SDHRCC). In the germline analysis, 16/17 SDHRCC harbored a germline alteration in SDHB, whereas only 17/22 FHRCC had pathogenic germline FH variants. SDHRCC had a lower mutation burden (p = 0.02) and copy number alteration burden (p = 0.0002) than FHRCC. All SDHRCC presented with deletion of chromosome 1p (overlapping SDHB), whereas FHRCC demonstrated high but not ubiquitous loss of 1q (FH locus). Both SDHRCC and FHRCC demonstrated significant, idiopathic accumulation of the metabolite guanine. FHRCC tumors had elevated levels of urea cycle metabolites (argininosuccinate, citrulline, and fumarate), whereas SDHRCC had elevation of numerous acylcarnitines. These characteristic metabolic changes enabled the identification of a previously unrecognized SDH-deficient RCC. ConclusionDespite sharing similar genetic etiology, SDHRCC and FHRCC represent distinct molecular entities with unique genetic and metabolic abnormalities. Translational RelevanceMutations to the TCA cycle enzymes Succinate Dehydrogenase (SDH) and Fumarate Hydratase (FH) predispose individuals to unique subtypes of renal cell carcinoma (SDHRCC and FHRCC, respectively). Defining the genetic and metabolic hallmarks of these diseases is critical for advancing new diagnostic and therapeutic approaches for these rare but biologically intriguing entities. Despite a superficially similar genetic etiology, SDHRCC and FHRCC demonstrated significantly fewer secondary mutations to other cancer-associated genes and copy number aberrations than FHRCC, and was distinguished by universal loss-of-heterozygosity of chromosome 1p. Metabolomic analysis identified pathways disrupted in both SDHRCC and FHRCC, including the massive accumulation of free guanine, as well as pathways uniquely disrupted in each of the two entities. These metabolomic findings enabled the identification of a previously unidentified case of unclassified RCC with SDH deficiency, suggesting that metabolomic profiling may aid in phenotypic classification of tumors and uncover novel therapeutic targets.