Murine MTHFD1-synthetase deficiency, a model for the human MTHFD1 R653Q polymorphism, decreases tumor growth in males. Mus musculus

[Abstract] The R653Q variant in the synthetase domain of the folate-metabolizing enzyme MTHFD1 has been shown to increase risk for birth defects, but it does not affect risk for development of colorectal cancer (CRC). However, since we have shown that this variant reduces purine synthesis, the goal of this study was to determine whether it could affect tumor growth. Using our mouse model for MTHFD1-synthetase deficiency (Mthfd1S+/-), we induced tumor formation with azoxymethane (AOM) and dextran sodium sulfate (DSS) in male and female wild-type and Mthfd1S+/- mice. Tumor size was significantly smaller due to mutant genotype, particularly in males. Tumor size was increased in female mice compared with males, regardless of genotype. Tumor number was not influenced by genotype and was lower in females. Inflammation within tumors of male Mthfd1S+/- mice was lower than in wild-type mice. Proliferation of mouse embryonic fibroblasts from mutant lines was slower than that in wild-type fibroblasts. Gene expression analysis in tumor adjacent normal (preneoplastic) tissue identified several genes involved in proliferation (Fosb, Fos, Ptk6, Esr2, Atf3) or inflammation (Atf3, Saa1, TNF-α) that were downregulated in mutant male mice. Female mutants did not have changes in expression for those genes, nor in tumor inflammation levels, compared with wild-type, suggesting a different mechanism directing tumor growth in females. We suggest that restriction of purine synthesis and reduced expression of critical tumor-promoting genes leads to slower tumor growth in MTHFD1-synthetase deficiency. These findings may have implications for CRC tumor growth and prognosis in individuals with the R653Q variant. Overall design: Affymetrix Mouse Gene 2.0 ST Array Chips were used to assess gene expression in normal colonic mucosa of four male Mthfd1S+/+ and two male Mthfd1S+/- BALB/c mice.