CTSB and cancer: Proteases and their inhibitors are in equilibrium, and this balance governs most normal and pathological processes.25 It was discovered that CysC might be involved in regulating the expression of cathepsin B, a cysteine protease primarily present in fast spreading cancer cells.26 The less common cathepsin B/CysC complexes in the sera of cancer patients compared to healthy controls or patients with benign diseases suggested an imbalance between the enzyme and its inhibitor in these patients.27