Differential gene expression and methylation in the retinoid/PPARA pathway and of tumor suppressors may modify intestinal tumorigenesis induced by low folate in mice.

SCOPE

Inadequate folate intake increases risk for colorectal cancer. We previously showed that low-folate diets induced intestinal tumors in BALB/c mice, but not in C57BL/6 mice. We suggested that DNA damage, altered methylation, and reduced apoptosis could contribute to tumorigenesis in this model.

METHODS AND RESULTS

To identify genes involved in tumorigenesis, we compared gene expression profiles in preneoplastic intestine of BALB/c and C57BL/6 mice-fed low folate. We identified 74 upregulated and 90 downregulated genes in BALB/c compared to C57BL/6 mice. We validated decreased expression of Bcmo1 and increased expression of Aldh1a, which would be expected to upregulate the peroxisome proliferator-activated receptor alpha (PPARA) pathway, and confirmed the expected upregulation of several Ppara downstream genes. We verified, in BALB/c mice, reduced expression of Sprr2a, a gene that increases resistance to oxidative damage, and of two oncosuppressors (Bmp5 and Arntl). Low folate increased Ppara and Aldh1a1 expression, and decreased Bcmo1, Sprr2a, and Bmp5 expression in BALB/c, compared to BALB/c on control diets. Bcmo1, Ppara, and Bmp5 showed differential DNA methylation related to strain, diet, and/or Mthfr genotype.

CONCLUSION

Disturbed regulation of the retinoid/PPARA pathway, which influences oxidative damage, and altered expression of tumor suppressors may contribute to intestinal tumorigenesis induced by low-folate intake.