CSK(Tyrosine-protein kinase CSK) is also named as C-Src kinase, protein-tyrosine kinase CYL and belongs to the protein kinase superfamily. Csk is a non-receptor tyrosine kinase with a molecular mass of 50 kDa. It contains the SH3 and SH2 domains in its N-terminus and a kinase domain in its C-terminus. It negatively regulates the kinase activity of SFKs and plays an important role in physiological functions via signaling pathways for cell proliferation, differentiation, adhesion, and migration(PMID:23548896). Csk may play a role in tumor suppression by inhibiting the oncogenic activity of SFKs. Indeed, overexpression of Csk can inhibit tumor growth of human colon cancer cells(PMID:23139636). This protein can be autophosphorylated(PMID:11181701).