CDCP1 and prostate cancer: The activity of CDCP1 is regulated by limited proteolysis of its extracellular domain (ECD), converting the full-length (FL) 135 kDa glycoprotein to a 70 kDa membrane spanning carboxyl-terminal fragment (CTF) and an amino-terminal fragment (ATF) of 65 kDa that is shed from the surface of several prostate cancer cell lines 15,16 and detected in serum of colorectal cancer patients 17.