CTSH and neoplasm: The 28 kDa single chain is believed to be the most important form of active CTSH in exerting specific aminopeptidase activity.5 However, del Re et al. 36 demonstrated that in colorectal carcinoma the expression of the 30 kDa form is decreased, while the expression of the mature 28 kDa form is increased in tumor comparing to normal tissue, thus showing the importance of different CTSH processing forms.