TET-Mediated Hypermethylation Primes SDH-Deficient Cells for HIF2α-Driven Mesenchymal Transition

Loss-of-function mutations in the SDHB subunit of succinate dehydrogenase predispose patients to aggressive tumors characterized by pseudohypoxic and hypermethylator phenotypes. The mechanisms leading to DNA hypermethylation and its contribution to SDH-deficient cancers remain un-demonstrated. We examine the genome-wide distribution of 5-methylcytosine and 5-hydroxymethylcytosine and their correlation with RNA expression in SDHB-deficient tumors and murine Sdhb(-/-) cells. We report that DNA hypermethylation results from TET inhibition. Although it preferentially affects PRC2 targets and known developmental genes, PRC2 activity does not contribute to the DNA hypermethylator phenotype. We also prove, in vitro and in vivo, that TET silencing, although recapitulating the methylation profile of Sdhb(-/-) cells, is not sufficient to drive their EMT-like phenotype, which requires additional HIF2 alpha activation. Altogether, our findings reveal synergistic roles of TET repression and pseudohypoxia in the acquisition of metastatic traits, providing a rationale for targeting HIF2a and DNA methylation in SDH-associated malignancies.