We modeled CDK12 overexpression in the normal human mammary epithelium by enforcing CDK12 expression in the normal mammary epithelial MCF10A cell line (CDK12-OE MCF10A cells), obtaining CDK12 levels comparable to the breast cancer BT474 cell line that bears CDK12 overexpression11,18 (Fig. 3a). This evidence concerns the gene CDK12 and breast cancer.