IDH2 and neoplasm: From what has been explained so far and from the fact that biochemical and knock down studies proved that both IDH1 and IDH2 isoforms function interchangeably to support reductive carboxylation [31], it is possible that if a tumor cell happened to harbor both neomorphic alleles of the two isoforms (i.e. the tumor cell has both IDH1 R132 and IDH2 R172 neomorphic alleles), that tumor cell will lose its ability to synthesize enough citrate through the reverse reductive carboxylation reaction to keep up with its division and eventually dies.