In ER+ breast cancer cells, FOXM1 engages in core circadian gene cryptochrome 2 (CRY2) promoter hypermethylation by forming the FOXM1/DNMT3b (DNA methyltransferase 3b) complex; the FOXM1/DNMT3b complex binds to the CRY2 promoter directly to downregulate the expression of CRY2 [69]. This evidence concerns the gene DNMT3B and breast cancer.