Abstract 3981: Enhancement of the Anticancer Activity of Methylenetetrahydrofolate Dehydrogenase Knockdown by Folate Depletion with Carboxypeptidase G2

Abstract The mitochondrial folate enzyme, methylene tetrahydrofolate dehydrogenase (MTHFD2), is a promising anticancer target because 1) it is required for the generation of one-carbon units required for purine synthesis and generation of NADH/NADPH necessary for protection from ROS in the mitochondria; 2) it is markedly distinct from the cytoplasmic MTHFD1 enzyme with respect to location, catalytic activity and cofactors; 3) it is expressed at low levels in proliferating normal cells; 4) in contrast, it is highly expressed in a variety of rapidly proliferating malignant tumors; 5) knockdown (KD) of MTHFD2 has been shown to inhibit proliferation in a subset of tumor cells in vitro; and 6) MTHFD2 KD is predicted to have metabolic consequences (glycine auxotrophy, folate deficiency) that could be exploited for combination therapy. In this study we tested the hypotheses that downregulation of MTHFD2 will result in relative folate deficiency, which can be exploited by using a folate-depleting enzyme, carboxypeptidase G2 (CPG2), to enhance tumor cell kill. CPG2 is approved by the FDA for the treatment of methotrexate overdose in patients. It acts to inactivate MTX or naturally occurring folates by hydrolyzing the terminal glutamate from folates and MTX, generating a pteroate and glutamate. As pteroates cannot be used to resynthesize folates, or MTX, this treatment depletes cells from MTX or folates. The combination of CPG2 in cell lines, MCF7 and T47D with MTHFD2 KD, was done and the actual increase in growth inhibition showed enhanced antitumor effects, indicating that when effective inhibitors of MTHFD2 are available, this combination may have widespread clinical usefulness, especially in rapidly proliferating tumors that express high levels of MTHFD2. Citation Format: Gulam M. Rather, John E. Kerrigan, Kathleen W. Scotto, Joseph R. Bertino. Enhancement of the anticancer activity of methylenetetrahydrofolate dehydrogenase knockdown by folate depletion with carboxypeptidase G2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3981.