MULTIPLE FORMS OF CATHEPSIN-B IN HUMAN LUNG-CANCER

In this study we have examined, by means of isoelectric focusing (IEF) in native polyacrylamide gel and contact-print fluorescence zymograph y, whether human lung carcinomas and the lung parenchyma contain diffe rent pools of multiple charge forms of the cysteine proteinase catheps in B. The isoelectric point (pI) patterns of cathepsin B from lung car cinoma and matched lung were similar, particularly with regard to 2 ma jor intermediate acidic enzyme pI forms designated as I and II (pI(app ) of 5.10 and 4.93 in tumors, and 5.11 and 4.94 in lungs, respectively ). The slightly acidic cathepsin B pI forms (pI(app) 5.47-5.19) in squ amous-cell lung carcinoma (SQCLC) were significantly move numerous tha n such enzyme pI forms in lungs. The numbers of the highly acidic cath epsin B pI forms (pl(app) 4.82-4.33) were significantly higher in SQCL C and lung adenocarcinoma (ACL) than in matched lung. The activity dis tribution percentage in the set of highly acidic cathepsin B pI forms was significantly higher in SQCLC and ACL than in matched lung. We als o observed that cathepsin B from SQCLC and matched lung was fully reco verable by IEF from inhibition by leupeptin. Using the cysteine-protei nase-specific inactivator E-64, we revealed by IEF that some cathepsin B isoforms (charge forms) from SQCLC were more resistant to inactivat ion by this compound than the corresponding enzyme isoforms from lungs . After IEF, the enzyme isoforms apparently lost their resistance to E -64. Our results indicate that the pool of multiple charge forms of ca thepsin B in SQCLC and ACL is different from that in the lung, and als o that there may be an increased level of loose complexes between cath epsin B and some proteins or polypeptides in SQCLC: compared to the lu ng. (C) 1995 Wiley-Liss, Inc.