CDK12 and breast cancer: Conversely, CDK12 has also been described as a pro-tumorigenic factor in different human cancers15–17, including breast cancer, where its tumorigenic role appears to depend mainly on its co-amplification and cooperation with the HER2 oncogene or on its synergistic interaction with oncogenic pathways, such as WNT and IRS1-ErbB-PI3K signaling18,19.