CTSG and colorectal carcinoma: Moreover, a noncell-permeable CTSG inhibitor I (CTSGi) (26), which potently inhibits CTSG protease activity, attenuated apoptosis induced by either recombinant CTSG or conditioned medium from neutrophils treated with CB-839 and 5-FU (NET medium) in a dose-dependent manner (Supplemental Figure 5, E–K) in HCT116, DLD1, and RKO CRC cells.