, Volume 21, Issue 4, pp 557-566
Date: 10 Dec 2009

One-carbon metabolism and CpG island methylator phenotype status in incident colorectal cancer: a nested case–referent study

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Abstract

Objective

We related prediagnostic plasma folate, vitamin B12, and total homocysteine concentrations, and the MTHFR 677C>T and 1298A>C polymorphisms, to the risk of colorectal cancer with and without the CpG island methylator phenotype (CIMP).

Methods

This was a nested case–referent study of 190 cases and double, matched referents from the large, population-based Northern Sweden Health and Disease Study. Using archival tumor tissue, promoter methylation in an eight-gene panel was analyzed by MethyLight.

Results

A reduced risk of CIMP-low/CIMP-high CRC (≥1 gene methylated) was observed in subjects with very low plasma folate concentrations [multivariate odds ratio 2.96 (95% CI 1.24–7.08) for quintiles two to five versus one (lowest)]. With the exception of a reduced risk in MTHFR 677 TT-homozygotes, none of the other one-carbon variables were associated with the risk of CIMP-low/CIMP-high CRC. For CIMP-negative CRC, only the MTHFR polymorphisms were statistically significantly related to risk, inversely for 677C>T and positively for 1298A>C, but a tendency toward a reduced risk was observed in subjects with an adequate methyl availability, combining the plasma variables [multivariate odds ratio 0.61 (95% CI 0.32–1.15)].

Conclusion

Though limited by low power, these findings suggest the possibility of different roles for one-carbon metabolism in different pathways of colorectal tumorigenesis.