Folate cycle enzyme MTHFD1L confers metabolic advantages in hepatocellular carcinoma
Derek Lee, … , Irene Oi-Lin Ng, Carmen Chak-Lui Wong
Derek Lee, … , Irene Oi-Lin Ng, Carmen Chak-Lui Wong
Published April 10, 2017
Citation Information: J Clin Invest. 2017;127(5):1856-1872. https://doi.org/10.1172/JCI90253.
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Research Article Gastroenterology Metabolism

Folate cycle enzyme MTHFD1L confers metabolic advantages in hepatocellular carcinoma

Abstract

Cancer cells preferentially utilize glucose and glutamine, which provide macromolecules and antioxidants that sustain rapid cell division. Metabolic reprogramming in cancer drives an increased glycolytic rate that supports maximal production of these nutrients. The folate cycle, through transfer of a carbon unit between tetrahydrofolate and its derivatives in the cytoplasmic and mitochondrial compartments, produces other metabolites that are essential for cell growth, including nucleotides, methionine, and the antioxidant NADPH. Here, using hepatocellular carcinoma (HCC) as a cancer model, we have observed a reduction in growth rate upon withdrawal of folate. We found that an enzyme in the folate cycle, methylenetetrahydrofolate dehydrogenase 1–like (MTHFD1L), plays an essential role in support of cancer growth. We determined that MTHFD1L is transcriptionally activated by NRF2, a master regulator of redox homeostasis. Our observations further suggest that MTHFD1L contributes to the production and accumulation of NADPH to levels that are sufficient to combat oxidative stress in cancer cells. The elevation of oxidative stress through MTHFD1L knockdown or the use of methotrexate, an antifolate drug, sensitizes cancer cells to sorafenib, a targeted therapy for HCC. Taken together, our study identifies MTHFD1L in the folate cycle as an important metabolic pathway in cancer cells with the potential for therapeutic targeting.

Authors

Derek Lee, Iris Ming-Jing Xu, David Kung-Chun Chiu, Robin Kit-Ho Lai, Aki Pui-Wah Tse, Lynna Lan Li, Cheuk-Ting Law, Felice Ho-Ching Tsang, Larry Lai Wei, Cerise Yuen-Ki Chan, Chun-Ming Wong, Irene Oi-Lin Ng, Carmen Chak-Lui Wong

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Figure 5

Knockdown of MTHFD1L caused cell cycle delay.

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Knockdown of MTHFD1L caused cell cycle delay. (A) 8-OH-dG levels in MHCC...
(A) 8-OH-dG levels in MHCC97L-NTC, -shML-00, and -shML-99 cells. (B) Oxygen consumption rate (OCR) in MHCC97L-NTC and -shML-99 cells was determined by XFp Analyzer (Seahorse Bioscience). Basal respiration, respiratory capacity, proton leak, and ATP-linked respiration were calculated based on the OCRs at different points when oligomycin, FCCP, and antimycin A and rotenone were sequentially added to cells. (C) Cell proliferation rate of MHCC97L-NTC, -shML-00, and -shML-99. An equal number of cells was seeded on day 0. Cell numbers were recorded daily by cell counting. (D) Representative pictures of flow cytometry analyses of propidium iodide staining in MHCC97L-NTC, -shML-00, and -shML-99 stable cells that were synchronized by 200 ng/ml nocodazole for 16 hours and released for 9 hours in the presence of vehicle control and antioxidants 10 μM GSH, 0.1 mM GSH-EE, and 2 mM NAC. (E) Percentage of cells in G1 phase. (F and G) Levels of intracellular ROS (F) and BrdU uptake (G) in MHCC97L-NTC and -shML-99 cells treated with vehicle or different concentrations of reduced GSH. Results are representative of 3 independent experiments. Error bars indicate mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 vs. NTC, or as indicated. A, C, and E–G: 1-way ANOVA. B: Student’s t test.