Lysosomal dipeptidyl-peptidases I and II in human squamous cell lung carcinoma and lung parenchyma

In the present work we studied the levels of activities of dipeptidyl-peptidase I (or cathepsin C, DPP-I) and dipeptidyl-peptidase II (DPP-II) and examined their isoelectric focusing profiles in matched pairs of human squamous cell lung carcinoma (SQCLC) and the lung from surgically treated patients (n = 33). The mean specific activities of DPP-I and DPP-II were higher in SQCLC (Stages I and II) than in the lung, but only the activity of DPP-II in Stage I SQCLC was significantly higher compared to the lung. The activities of both enzymes were higher in the tumor than in the lung in 10 of 20 Stage I SQCLC patients, but only in 3 of 13 Stage II SQCLC patients. The specific activities of DPP-I and DPP-II in the lungs showed a good correlation while the correlation of both enzyme activities in SQCLCs was poor. We observed only a small and mutually comparable activation of DPP-I in extracts from SQCLCs and from the lungs by dithiothreitol. The isoelectric focusing profile of several DPP-II forms in SQCLCs and the lungs was similar and the single major DPP-II isoform revealed in the tumors and lungs showed a pIapp of 5.3-5.2. The isoelectric focusing profile of DPP-I showed multiple enzyme forms in SQCLCs (pIapp 6.3-4.5) as well as in the lungs (pIapp 6.4-4.8). In SQCLCs, as well as in the lungs, the activities of the DPP-I forms with pIapp values < or = 5.6 were shifted by neuraminidase treatment to the site of the major DPP-I isoform with pIapp of about 6.0 and the zymograms then showed an another DPP-I with pIapp of 5.7, which was less discernible in the lung. In some patients, the DPP-I forms with pIapp values < or = 5.6 from SQCLC retained a greater percentage of activity distribution than did the DPP-I pIapp-counterparts from the lung.