CST3 and hepatocellular carcinoma: It has been shown previously that the stab-1 HCC oligomers are not capable of inhibiting the protease papain, indicative of the papain-binding site (N-terminal loops 1 and 2) being buried within the oligomer structure, whereas the oligomers are still capable of inhibiting the activity of legumain, confirming that this part of the cystatin C structure is still available for protease-binding [16].