CDK1 and breast cancer: Given the observation that concomitant loss of TP53 and TP73 is rather infrequent in cancer (at least in CRC and breast cancer) this also suggests that routes other than p53/p73 loss can result in lowered expression of CDKN1A and increased CDK1 activity and contribute to abnormally increased microtubule polymerization rates and CIN in human cancer (Fig. 7).