STK16 (serine/threonine kinase 16, also known as Krct, PKL12, MPSK1, and TSF-1) is a unique member of the NAK (Numb Associated Kinase) subfamily of serine/threonine protein kinase. STK16 appears to be associated with the Golgi and is believed to be involved in the regulation of VEGF expression and soluble cargo secretion as well as end-bud morphogenesis during murine mammary gland development. STK16 has been demonstrated to interact with MAL2 protein, GlcNAcK kinase, and DRG1 protein and is involved in the TGF-β signaling pathway. As an active serine/threonine kinase, STK16 has been reported to phosphorylate DRG1 and 4EBP1 in vitro.[1] Despite its ubiquitous expression, STK16 is expressed preferentially within specific cellular compartments in multiple tissues, in particular within the testis and gastrointestinal tract. In addition, STK16 is located on mouse chromosome 11 closely linked to the epidermal growth factor receptor and, therefore, is likely to be co-amplified in a variety of human tumors.[2]