There are several studies bringing promising results of epigenetic modulation of tumor suppressor genes or oncogenes through dCas9/effector complexes in the most common cancers, for example, activation of PTEN in breast cancer [159], BRAF1 gene in cervical cancer [160] and other genes in colon cancer [161], liver cancer [162], prostate cancer [163] or lung cancer [164] and others. This evidence concerns the gene PTEN and breast cancer.