Unlike other mitotic CDKs, CDK5 is activated by binding to p35 or p39.5 In the central nervous system, CDK5 has been proved as a key regulator of neuronal migration, synaptic activity and neuronal cell survival and death.6, 7, 8 Over the past decade, an increasing body of evidence has suggested that CDK5 may also have a significant role in the tumorigenesis of multiple organs, such as breast cancer, pancreatic cancer and neuroendocrine thyroid carcinoma.9, 10, 11 However, the knowledge on the role and underlying mechanism of CDK5 in CRC remains poorly unknown. Here, CDK5 is linked to breast cancer.