[Effect of peripheral bloodgenomic DNA methylation on the relationship between methyl donor status and risk of breast cancer]

Objective: To explore the effect of peripheral blood genomic DNA methylation on the relationship between methyl donor status and risk of breast cancer. Methods: A case-control study was conducted. Each three hundred breast cancer cases and controls were consecutively recruited. Food frequency questionnaire was used to collect dietary information. Amounts on folate, methionine, choline and betaine intake were calculated. Blood samples were collected for DNA extraction. Peripheral blood genomic DNA methylation was measured by using the Methyl Flash(TM) Methylated DNA Quantification Kit. Pathway analysis was used to examine the effect of genomic DNA methylation on the relations between methyl donor status and risk of breast cancer. Results: The genome DNA methylation rates were 0.46%±0.25% and 0.53%±0.34%, respectively on both cases and controls, with differences statistically significant (P<0.01). Results from the pathway analysis, results showed that methionine consumption was related to genomic DNA methylation (β=0.065, P<0.05) while genomic DNA methylation was related to the risk of breast cancerk (β=-0.027, P<0.05), respectively. Conclusions: The level of peripheral blood genomic DNA methylation in breast cancer cases was significantly lower than that in the controls. Genomic DNA methylation seemed to have played a mediated role between methionine and the risk of breast cancer.