Cystatin C is a 14 kDa member of the Cystatin superfamily of cysteine protease inhibitors. Most cell types secrete Cystatin C. Cystatin C inhibits cathepsins, and thereby may function as a tumor suppressor by inhibiting cathepsin mediated tumor cell invasion. In addition, this tumor suppressor function can also be attributed to Cystatin Cs ability to antagonize TGF-beta1 signaling.
