PRDM9 and colorectal cancer: In colorectal cancer, members of the Polycomb group machinery B cell-specific Moloney murine leukemia virus integration site 1 (Bmi1) and enhancers of zeste homolog 2 (EZH2), as well as histone methyltransferase G9a, are overexpressed and critical for the maintenance of CSC functional hallmarks [11,12,13].