Multiple cycle enzymes, including aconitase (also known as aconitate hydratase, AH), isocitrate dehydrogenase (IDH), FH, succinate dehydrogenase (SDH) and KGDHC, are frequently mutated or deregulated in human cancers (Eng et al., 2003; Juang, 2004; Yan et al., 2009). Here, FH is linked to cancer.