One-carbon metabolism biomarkers and genetic variants in relation to colorectal cancer risk by KRAS and BRAF mutation status

PLoS One. 2018 Apr 25;13(4):e0196233. doi: 10.1371/journal.pone.0196233. eCollection 2018.

Abstract

Disturbances in one-carbon metabolism, intracellular reactions involved in nucleotide synthesis and methylation, likely increase the risk of colorectal cancer (CRC). However, results have been inconsistent. To explore whether this inconsistency could be explained by intertumoral heterogeneity, we evaluated a comprehensive panel of one-carbon metabolism biomarkers and some single nucleotide polymorphisms (SNPs) in relation to the risk of molecular subtypes of CRC defined by mutations in the KRAS and BRAF oncogenes. This nested case-control study included 488 CRC cases and 947 matched controls from two population-based cohorts in the Northern Sweden Health and Disease Study. We analyzed 14 biomarkers and 17 SNPs in prediagnostic blood and determined KRAS and BRAF mutation status in tumor tissue. In a multivariate network analysis, no variable displayed a strong association with the risk of specific CRC subtypes. A non-synonymous SNP in the CTH gene, rs1021737, had a stronger association compared with other variables. In subsequent univariate analyses, participants with variant rs1021737 genotype had a decreased risk of KRAS-mutated CRC (OR per allele = 0.72, 95% CI = 0.50, 1.05), and an increased risk of BRAF-mutated CRC (OR per allele = 1.56, 95% CI = 1.07, 2.30), with weak evidence for heterogeneity (Pheterogeneity = 0.01). This subtype-specific SNP association was not replicated in a case-case analysis of 533 CRC cases from The Cancer Genome Atlas (P = 0.85). In conclusion, we found no support for clear subtype-specific roles of one-carbon metabolism biomarkers and SNPs in CRC development, making differences in CRC molecular subtype distributions an unlikely explanation for the varying results on the role of one-carbon metabolism in CRC development across previous studies. Further investigation of the CTH gene in colorectal carcinogenesis with regards to KRAS and BRAF mutations or other molecular characteristics of the tumor may be warranted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers, Tumor / genetics*
  • Carbon / metabolism
  • Case-Control Studies
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / metabolism
  • Cystathionine gamma-Lyase / genetics*
  • Female
  • Gene Regulatory Networks
  • Genetic Association Studies
  • Humans
  • Male
  • Middle Aged
  • Polymorphism, Single Nucleotide*
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • Sweden

Substances

  • Biomarkers, Tumor
  • KRAS protein, human
  • Carbon
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins p21(ras)
  • Cystathionine gamma-Lyase

Grants and funding

This work was supported by Swedish Council for Working Life and Social Research (grant number 2007-0925 to IJ), Swedish Cancer Society (grant numbers 2012/0501 to RP and 2014/780 to BVG), the Swedish Research Council (grant number K2012-55X-21100-04-3 to RP), the Faculty of Medicine at Umeå University, the Cancer Research Foundation in Northern Sweden (grant numbers AMP 15-761 and AMP 16-798 to BG, and AMP 15-768 to RM), and through the regional agreement between Umeå University and Västerbotten County Council on cooperation in the field of Medicine, Odontology and Health (grant numbers VLL-493531 and VLL-400931 to IJ). The funders provided support in the form of salaries for authors or costs of analyses (RM, BG, IJ, RP, BVG), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The same was true for Bevital AS, who is the employer of KM. Bevital AS is 100% owned by a private non-profit organization. The specific roles of the authors are articulated in the ‘author contributions’ section. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.