IDH1 and neoplasm: Mutations in the IDH1 or IDH2 gene may predict a better prognosis by downregulating several hypoxia-inducible factor 1α (HIF-1α) target genes which are involved in glycolytic energy metabolism [53], among them lactate dehydrogenase (LDH) which catalyzes the conversion of pyruvate to lactate and thereby contributes to the acidification of the tumor microenvironment [54].