CTCF and breast cancer: Moreover, CTCF play important roles during carcinogenesis: epigenetic silencing of tumor suppressor genes such as p16 and Rb (De La Rosa-Velazquez et al., 2007; Witcher and Emerson, 2009), apoptosis of breast cancer cells (Docquier et al., 2005), and regulation of important tumor suppressor genes such as p53 (Recillas-Targa et al., 2011; Saldana-Meyer and Recillas-Targa, 2011).