IDH1 and neoplasm: Knockdown of mutant IDH1 in the HT1080 tumor cell line confers significant decreases in cellular proliferation, decreases in the onco-metabolite D-2HG, overall decreases in clonogenic potential, as well as an induction of a G0/G1 cell cycle arrest; thereby suggesting that depletion of mutant IDH1 from an IDH1 mutant tumor cell line decreases the tumorigenic potential of these cells.