CDK18 belongs to the PCTAIRE family of CDKs, which include human CDK16, CDK17 and CDK18, all of which share a conserved PCTAIRE amino acid sequence in the helical α-C region of the kinase N-lobe. In mature tissues and cell lines, CDK18 predominantly localizes in the cytoplasm and at the plasma membrane, and it was shown to interact with cyclin A2 and displayed kinase activity, which is further controlled by PKA through Ser12 phosphorylation. CDK18 was first described as a neuronal kinase that phosphorylates TAU protein when overexpressed in human brain. It has multifaceted functions in human cancer and can act either as oncogene or as tumor suppressor, depending on the specific tumor type and context.