Cysteine proteinase cathepsin H in tumours and sera of lung cancer patients: relation to prognosis and cigarette smoking

In order to evaluate the role of cysteine peptidase cathepsin H (Cath H) in human lung cancer its protein levels were determined in 148 pairs of lung tumour tissue and adjacent non-tumourous lung parenchyma using the enzyme-l inked immunosorbent assay technique. Additionally, Cath H levels were deter mined in sera of 171 patients with malignant rumours, 34 patients with beni gn lung diseases and 47 healthy controls, The median level of Cath H in tum our tissue was 0.64 times that in the corresponding lung parenchyma. Relati ng tumour levels with histological type we found higher Cath H levels in sm all-cell and adenocarcinomas and lower levels in squamous cell carcinoma, l arge-cell carcinoma and secondary tumours. A significant difference in Cath H level between lung tumour tissue and non-tumourous lung parenchyma was a ssociated with the group of cigarette smokers (156 vs 263 ng mg(-1) protein , P < 0.001). For this group of patients Cath H tumour levels correlated wi th the survival rate, while for the entire patient population this was not the case. Smokers with high tumour levels of Cath H experienced poor surviv al. Cath H was significantly higher in sera of patients with malignant and benign lung diseases than in control sera (P < 0.001). The increase was sig nificant for all histological types, being the highest in small-cell and sq uamous cell carcinomas, Our study reveals that in lung rumours there is dif ferent behaviour of Cath H compared with other cysteine peptidases, e.g. ca thepsin B and cathepsin L. Variations between tissue and serum levels of Ca th H indicate either reduced expression or enhanced secretion of this enzym e in lung rumours, (C) 2000 Cancer Research Campaign.