YY1 and breast cancer: This is achieved through the activation or repression of genes that are specific to different cancer types, such as the cyclin-dependent kinase inhibitor (CDKN3) in pancreatic cancer that YY1 represses or v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 (ERBB2) in breast cancer that is induced by YY1 [9].