Folic acid enforces DNA methylation-mediated transcriptional silencing of PTEN, APC and RARbeta2 tumour suppressor genes in breast cancer

► High level of folic acid led to PTEN, RARbeta2 and APC promoters hypermethylation. ► Folic acid caused DNA-mediated transcriptional silencing of PTEN, RARbeta2 and APC. ► MCF-7 cells are more susceptible for folic acid action than MDA-MB-231 cells. ► Effect of folic acid action depends on dose, timing and individual conditions.