CDK12 and breast cancer: Recently, we discovered that cyclin-dependent kinase 12 (CDK12) as a co-amplified gene on 17q12 is involved in tumorigenesis and trastuzumab resistance in HER2+ breast cancers, proposing CDK12 an attractive therapeutic target to escalate the therapeutic activity of trastuzumab and overcome the trastuzumab resistance (Figure 1) [10].