Immunodetection of cathepsins B and L present in and secreted from human pre-malignant and malignant colorectal tumour cell lines

• Published in: International journal of cancer Vol. 43; no. 3; p. 478
• Main Authors: Maciewicz, R A, Wardale, R J, Etherington, D J, Paraskeva, C
• Format: Journal Article
• Language: English
• Published: United States 15-03-1989
• Subjects: Adenoma - enzymology; Animals; Basement Membrane - metabolism; Carcinoma - enzymology; Cathepsin B - metabolism; Cathepsin L; Cathepsins - metabolism; Cattle; Collagen - metabolism; Colorectal Neoplasms - enzymology; Cysteine Endopeptidases; Cytoplasm - enzymology; Endopeptidases; Enzyme Precursors - metabolism; Fluorescent Antibody Technique; Humans; Hydrogen-Ion Concentration; Immunologic Techniques; In Vitro Techniques; Lysosomes - enzymology; Tumor Cells, Cultured
• ISSN: 0020-7136
• DOI: 10.1002/ijc.2910430323

Pre-malignant and malignant human colorectal tumour epithelial cell lines both secreted precursor forms of the 2 cysteine proteinases, cathepsins B and L. The amount of proteinases secreted by these cell lines varied according to the cell density. Comparison at similar cell densities showed that the pre-malignant, adenoma-derived cell line (PC/AA) secreted as much, or more, of both cathepsin B and L precursors as did the malignant, carcinoma-derived cell line (PC/JW/FI). However, mature forms of cathepsins B and L were detected in the culture media of only the carcinoma-derived cell line, thus indicating that the invasive potential of a tumour may be related to its ability to process extracellularly the secreted precursor enzyme to a mature and consequently active enzyme, rather than to the amount of proteinase synthesized and/or secreted. Similar results were obtained using 2 other epithelium-derived tumour cell lines, HT/29 (carcinoma) and SP/AN (adenoma). Immunolocation studies showed that cathepsin B was lysosomal while cathepsin L appeared to have a distribution more consistent with a plasma membrane association. Purified human cathepsins B and L (mature form) were capable of solubilizing an isolated basement membrane matrix (bovine anterior lens capsule) in vitro, thus indicating that the secreted mature enzymes and the membrane-associated cathepsin L could potentially degrade basal laminae or sub-endothelial basement membranes in vivo.