Proteolytic activity of human tumor cell lines deriving from bronchial squamous cell carcinoma, pulmonary metastasis of rhabdomyosarcoma and pleural metastasis of mesothelioma.

The proteolytic activities of human tumor cell lines deriving from bronchial squamous cell carcinoma, a lung metastasis of an embryonal rhabdomyosarcoma and a pleural mesothelioma were measured by use of chromogenic substrates. N-acetyl-alanine aminopeptidase activity, plasminogen activator activity, H-D-Ile-Pro-Arg-p-NA splitting activity as well as plasmin-like activity, cathepsin G-like activity and plasma-kallikrein-like activity were found in cell lysates. The enzymatic activity of N-acetyl-alanine aminopeptidase, plasminogen activator and H-D-Ile-Pro-Arg-p-NA splitting activity changed during culturing. Plasminogen activator and H-D-Ile-Pro-Arg-p-NA splitting activity decreased to very low values, whereas N-acetyl-alanine aminopeptidase activity leveled at 1 x 10(-5) mU/cell. Unlike other proteolytic activities, plasminogen activator was released into the medium. Plasminogen activator activity could be measured in culture medium which contained no fetal calf serum.