Cathepsin S in tumours, regional lymph nodes and sera of patients with lung cancer: relation to prognosis

Cysteine proteinase cathepsin S (Cat S) is expressed mainly in lymphatic ti ssues and has been characterised as a key enzyme in major histocompatibilit y complex class II (MHC-II) mediated antigen presentation. Cat S has been m easured in tissue cytosols of lung parenchyma, lung tumours and lymph nodes and in sera of patients with lung tumours and of healthy controls, by spec ific enzyme-linked immunosorbent assay (ELISA). A difference in Cat S level was found between tumour and adjacent control tissue cytosols of 60 lung c ancer patients (median 4.3 vs. 2.8 ng mg(-1) protein). In lymph nodes obtai ned from 24 patients of the same group, the level of Cat S was significantl y higher than in tumours or lung parenchyma (F < 0.001). Additionally, sign ificantly higher levels were found in non-infiltrated than in infiltrated l ymph nodes (median 16.6 vs 7.5 ng mg(-1) protein). Patients with low levels of Cat S in tumours and lung parenchyma exhibited a significantly higher r isk of death than those with high levels of Cat S (P = 0.025 - tumours; P = 0.02 - parenchyma). Immunohistochemical analysis (IHA) of lung parenchyma revealed a staining reaction in alveolar type II cells, macrophages and bro nchial epithelial cells. In regional lymph node tissue, strong staining of Cat S was found in lymphocytes and histiocytes. Nevertheless, Cat S was det ected also in tumour cells, independently of their origin. Our results prov ide evidence that Cat S may be involved in malignant progression. Its role, however, differs from that of the related Cats B and L and could be associ ated with the immune response rather than with remodelling of extracellular matrix. (C) 2001 Cancer Research Campaign.