PTEN and breast carcinoma: It was demonstrated that overmethylation of the PTEN promoter inhibits PTEN expression in tamoxifen-resistant breast carcinoma cells and activates Protein Kinase B (AKT) and 5-Azacytidine (5-Aza) methylation of the PTEN promoter and making cells more susceptible to tamoxifen's cytotoxicity.