FH and neoplasm: Indeed, striking activation of HIF was observed in the mouse model described above and in FH-associated human cancer, as well as in tumors linked to inactivation of the succinate dehydrogenase enzyme complex and mutations in genes encoding isocitrate dehydrogenases 1 and 2, which have also been defined as tumor suppressors or oncogenes (Pollard and Ratcliffe, 2009)).