CST6 is a member of the type 2 cystatin family. Some of the members are active cysteine protease inhibitors, while cystatin E/M moderate the inhibition of cathepsin B but is not active against cathepsin C. CST6 is secretable proteins that influence osteogenesis and bone resorption, regulation of the insulin and hepatocyte growth factor receptors, and the response to systemic inflammation.