The overall goal of this proposal is to characterize the novel tumor suppressor activity of a key metabolic enzyme and to determine the mechanism(s) of its selective toxicity to malignant vs. non-malignant cells. FDH (10-formyltetrahydrofolate dehydrogenase) irreversibly converts 10-formyltetrahydrofolate, an essential substrate for de novo purine biosynthesis, to tetrahydrofolate. Through depletion of this substrate, FDH can restrict purine biosynthesis. In turn, this interferes with important downstream intracellular processes, including DNA/RNA biosynthesis and DNA repair. Because of this critical metabolic function, down-regulation of FDH in cancer cells was predicted to be prosurvival, while artificial elevation through stable transfection, would be toxic. We have recently made the important observation that FDH is strongly and ubiquitously down-regulated in tumor tissues and cancer cell lines and that FDH promoter hypermethylation is likely involved in this down-regulation. We have further demonstrated that moderate FDH expression in FDH-deficient cancer cells induces apoptotic cell death. Furthermore, evidence was recently obtained that p53 is required to mediate FDH-induced cytotoxicity. In contrast, non-cancer cells were insensitive to FDH elevation. Therefore, it is proposed that cancer cells silence the FDH gene in order to escape cytotoxicity. Our central hypothesis is that FDH down-regulation through promoter hypermethylation is one of the important means by which malignancies gain pro-survival advantage over normal cells.
The Specific Aims that will be used to address this hypothesis are: (1) Determine the molecular mechanisms of FDH-induced apoptosis in transfected cancer cells, (2) Elucidate the mechanism(s) that protects non-malignant cells from FDH-induced apoptosis, and (3) Determine the role of promoter hypermethylation in down-regulation of FDH in cancer cells. Stable clones of malignant cells that inducibly express FDH, resistant cancer cell clones that have acquired the ability to constitutively express FDH, and FDH-insensitive non-malignant cells, will be used to pursue the goals of this project. It is proposed that investigation of the critical role of FDH in cancer cell survival will provide important insight into the malignant process itself and link disregulation of important metabolic pathways to cell death.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Etiology Study Section (CE)
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Arya, Suresh
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Medical University of South Carolina
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Fekry, Baharan; Esmaeilniakooshkghazi, Amin; Krupenko, Sergey A et al. (2016) Ceramide Synthase 6 Is a Novel Target of Methotrexate Mediating Its Antiproliferative Effect in a p53-Dependent Manner. PLoS One 11:e0146618
Krupenko, Natalia I; Holmes, Roger S; Tsybovsky, Yaroslav et al. (2015) Aldehyde dehydrogenase homologous folate enzymes: Evolutionary switch between cytoplasmic and mitochondrial localization. Chem Biol Interact 234:12-7
Prakasam, A; Ghose, S; Oleinik, N V et al. (2014) JNK1/2 regulate Bid by direct phosphorylation at Thr59 in response to ALDH1L1. Cell Death Dis 5:e1358
Oleinik, Natalia V; Helke, Kristi L; Kistner-Griffin, Emily et al. (2014) Rho GTPases RhoA and Rac1 mediate effects of dietary folate on metastatic potential of A549 cancer cells through the control of cofilin phosphorylation. J Biol Chem 289:26383-94
DebRoy, Suchandra; Kramarenko, Inga I; Ghose, Sampa et al. (2013) A novel tumor suppressor function of glycine N-methyltransferase is independent of its catalytic activity but requires nuclear localization. PLoS One 8:e70062
Strickland, Kyle C; Krupenko, Natalia I; Krupenko, Sergey A (2013) Molecular mechanisms underlying the potentially adverse effects of folate. Clin Chem Lab Med 51:607-16
Hoeferlin, L Alexis; Fekry, Baharan; Ogretmen, Besim et al. (2013) Folate stress induces apoptosis via p53-dependent de novo ceramide synthesis and up-regulation of ceramide synthase 6. J Biol Chem 288:12880-90
Oleinik, Natalia V; Krupenko, Natalia I; Krupenko, Sergey A (2011) Epigenetic Silencing of ALDH1L1, a Metabolic Regulator of Cellular Proliferation, in Cancers. Genes Cancer 2:130-9
Hoeferlin, L Alexis; Oleinik, Natalia V; Krupenko, Natalia I et al. (2011) Activation of p21-Dependent G1/G2 Arrest in the Absence of DNA Damage as an Antiapoptotic Response to Metabolic Stress. Genes Cancer 2:889-99
Oleinik, N V; Krupenko, N I; Krupenko, S A (2010) ALDH1L1 inhibits cell motility via dephosphorylation of cofilin by PP1 and PP2A. Oncogene 29:6233-44

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