Abstract 1803: Lethal synthesis: Potent anticancer activity of a glycine uptake inhibitor in tumor cells with mitochondrial methylenetetrahydrofolate dehydrogenase (MTHFD2) knocked down

Methylene tetrahydrofolate dehydrogenase 2 (MTHFD2) is a mitochondrial bifunctional enzyme with dehydrogenase and cyclohydrolase activity. MTHFD2 is expressed in embryonic tissues and not in adult tissues, and by generating formate for purine biosynthesis, enhances proliferation. It is over expressed in many cancers, including breast cancer, and has become an important cancer drug target. Knockdown (KD) of MTHFD2 in breast cancer cell lines MCF7 and T47D, slowed proliferation and resulted in an increase in early apoptosis and a S-phase block. Lack of MTHFD2 causes a dependence on glycine, and in the absence of glycine, proliferation of the MCF-7 cell line with MTHFD2 knocked down was inhibited even further. A known specific glycine transporter type-I (GlyT1) inhibitor, ORG 25935 potently inhibited growth of MCF7 cell with MTHFD2 KD, while it had less of an effect on T47D cells with MTHFD2 KD. Furthermore, both cell lines with MTHFD2 KD showed increase in expression of GlyT1 (SLC6A9) at both mRNA and protein level, using the qPCR and western blotting, respectively. The metabolomics studies showed that intracellular glycine, and NAD+ pools are more reduced in control cells compared to MTHFD2 KD cells on treatment with GlyT1 inhibitor, suggesting that this inhibitor causes glycine depletion in the cells. These data encourage the development of inhibitors of MTHFD2 for use in combination with glycine transport inhibitors. Citation Format: Gulam Mohmad Rather, Joseph R. Bertino. Lethal synthesis: Potent anticancer activity of a glycine uptake inhibitor in tumor cells with mitochondrial methylenetetrahydrofolate dehydrogenase (MTHFD2) knocked down [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1803.