It was confirmed that the thiol protease inhibitory activities in human lung cancer extracts were significantly higher than normal lung tissue extracts.
Furthermore the thiol protease inhibitor was extracted from human lung cancer tissue and purified by papain-Sepharose and Sephadex G-100 column chromatographies. The purified inhibitor inhibited papain and ficin, and its molecular weight determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was about 13,000.