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Characterization of an extracellular matrix-degrading protease derived from a highly metastatic tumor cell line
Abstract:
A proteolytic activity associated with the microsomal fraction of L-5178Y/Esb tumor cells has been characterized. The enzyme has a molecular weight of 80-90 kD as determined by affinity-labelling with [3H]DFP and SDS-gel electrophoresis. It cleaves ester substrates at the carboxyl position of lysine and arginine and can activate the proenzyme plasminogen. The enzyme is found to be associated with the plasma membranes of high and low metastatic tumor cell lines and is shed in high-molecular-weight form mainly by the high metastatic variant. The pH optimum for esterase and protease activities was 7.5-8.5. Although similar to trypsin in substrate specificity, the enzyme was not inhibited by lima-bean trypsin inhibitor but was inhibited by DFP, PMSF, aprotinin and leupeptin. Partially purified preparations of the protease can alone degrade 125I-labelled endothelial cell extracellular matrix, pointing at the putative role of this enzyme in tumor invasion.
Insights
Researchers identified a novel protease in tumor cells that degrades extracellular matrix. This enzyme, associated with high metastatic potential, may play a key role in tumor invasion and metastasis.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Tumor cell invasion and metastasis are complex processes involving the degradation of the extracellular matrix.
- Proteolytic enzymes are implicated in facilitating tumor cell migration and invasion.
Purpose of the Study:
- To characterize a specific proteolytic activity found in the microsomal fraction of L-5178Y/Esb tumor cells.
- To investigate the enzyme's properties, substrate specificity, and potential role in tumor cell behavior.
Main Methods:
- Affinity labeling with [3H]DFP and SDS-gel electrophoresis to determine molecular weight.
- Assays for esterase and protease activity at optimal pH (7.5-8.5).
- Inhibition studies using various protease inhibitors (DFP, PMSF, aprotinin, leupeptin) and substrate specificity analysis (lysine, arginine).
- Degradation assays using 125I-labelled endothelial cell extracellular matrix.
Main Results:
- A protease with a molecular weight of 80-90 kD was identified.
- The enzyme exhibits esterase activity towards carboxyl positions of lysine and arginine and activates plasminogen.
- It is associated with plasma membranes of both high and low metastatic cell lines, shed predominantly by high metastatic variants.
- The protease degrades extracellular matrix, suggesting a role in tumor invasion.
Conclusions:
- A novel tumor-associated protease with characteristics similar to trypsin but distinct inhibition profiles was identified.
- This enzyme's ability to degrade extracellular matrix highlights its potential significance in cancer cell invasion and metastasis.
- Further investigation into this protease could lead to new therapeutic strategies targeting tumor spread.