Modulation of Redox Homeostasis by Inhibition of MTHFD2 in Colorectal Cancer: Mechanisms and Therapeutic Implications

Background Overcoming oxidative stress is a critical step for tumor progression; however, the underlying mechanisms in colorectal cancer (CRC) remain unclear. Methods We investigated nicotinamide adenine dinucleotide (phosphate) (NAD(P))-dependent enzyme methylene tetrahydrofolate dehydrogenase 2 (MTHFD2) expression, clinical relevance, redox modification, and molecular mechanisms using the CRC cells and tissues (n=462 paired samples). The antitumor effects of MTHFD2 inhibitor LY345899 on CRC tumorigenesis and metastasis were evaluated in vitro and in vivo. Data analysis used Kaplan-Meier, Pearson's correlation, and Student t test where appropriate. All statistical tests were two-sided. Results Here, we report that the patients with high expression of MTHFD2 have a shorter overall survival (HR=1.62, 95% CI=1.12 to 2.36, P = .01) and disease-free survival (HR=1.55, 95% CI=1.07 to 2.27, P = .02) than patients with low MTHFD2 expression. Suppression of MTHFD2 disturbs NADPH and redox homeostasis and accelerates cell death under oxidative stress, such as hypoxia or anchorage independence (P <= .01 for all). Also, genetic or pharmacological inhibition of MTHFD2 suppresses CRC cell growth and lung and peritoneal metastasis in cell-based xenografts (n=5-8 mice per group). Importantly, LY345899 treatment statistically significantly suppresses tumor growth and decreases the tumor weight in CRC patient-derived xenograft models (n=10 mice per group, mean [SD] tumor weight of the vehicle-treated group was 1.83 [0.19]mg vs 0.74 [0.30]mg for the LY345899-treated group, P < .001) Conclusions Our study presents evidence that MTHFD2 confers redox homeostasis and promotes CRC cell growth and metastasis. The folate analog LY345899 as MTHFD2 inhibitor displays therapeutic activity against CRC and warrants further clinical investigation for CRC treatment.