CEACAM6 and breast cancer: Nevertheless numerous epigenetically-regulated genes are known to be directly silenced by DNA methylation in breast cancer including cell cycle control genes (APC, RASSF1, RB, TFAP2A), steroid receptor genes (ESR1, PGR, RARα), tumor suppressor genes (BRCA1, CDKN2A, CST6), and metastasis-associated genes (CDH1, CEACAM6, PCDHGB6), among others [16-19].