Neutral proteinases and inhibitors secreted by human rectal adenocarcinoma cell line (RCM-1)

A human rectal adenocarcinoma cell line, RCM-1, secreted some neutral proteinases: metallo-, serine and cysteine proteinases; and trypsin inhibitors into the serum-free conditioned medium (SFCM) in vitro. They were separated by anion-exchange and gel filtration high-performance liquid chromatography. SFCM from the cells of early passage numbers (20-24) contained native activities of serine proteinase and collagenolytic metalloproteinase. However, after several passages the native activities of them were diminished and latent form of metalloproteinase increased. In contrast to the native proteolytic activities, trypsin inhibitory activity was elevated in SFCM from the cells of passages 38-42. It inhibited the serine proteinase secreted by the same cells of early passage numbers. Furthermore, the serine proteinase was able to activate the latent form of metalloproteinase. Cooperative roles of these tumor-secreted proteinases and inhibitors may be important in tumor invasion.