Methyl-deficient diets, methylated ER genes and breast cancer: An hypothesized association

Recent molecular studies show that ER-negative breast cancer results from t he lack of ER gene transcription due to the methylation of the CpG island 5 ' to the gene. Because CpG island methylation is an early event in carcinog enesis and because methyl-deficient diets could result in CpG island methyl ation, it is relevant to postulate that methyl-deficient diets may be a ris k factor for breast cancer with methylated ER genes (as opposed to the dise ase with unmethylated ER genes). This molecular-based etiologic hypothesis may facilitate epidemiological research on the relationship between breast cancer and diet that has been unclear until now.