Melanoma-mediated dissolution of extracellular matrix: contribution of urokinase-dependent and metalloproteinase-dependent proteolytic pathways
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A M Montgomery1, Y A De Clerck, K E Langley
1Department of Immunology, Scripps Research Institute, La Jolla, California 92037.
Abstract:
Constitutive overexpression of both urokinase and matrix metalloproteinase (MMP) activity is frequently observed in individual malignant tumors. In this study we describe the combined contribution of these distinct enzyme systems to the invasive phenotype of a highly metastatic human melanoma cell line (M24met). M24met cells were found to secrete a spectrum of MMPs, including interstitial collagenase, type IV collagenases (M(r) 92,000 and 72,000 progelatinases), and stromelysin. Urokinase, but not tissue-type plasminogen activator, was detected in M24met-conditioned media and on cell surfaces. The contribution of these enzymes to extracellular matrix dissolution was determined by exploiting specific inhibitors, namely tissue inhibitor of the metalloproteinases-2 and plasminogen activator inhibitor-2. Due to the coexpression of urokinase and MMP-dependent activity, M24met cells were observed to degrade multiple components of the extracellular matrix and to significantly degrade both interstitial and basement membrane matrices. Urokinase-dependent removal of matrix glycoprotein was observed to precede MMP-dependent collagenolysis as a prerequisite rate-limiting step. We present evidence which suggests that this temporal relationship is imposed by the structural architecture of the matrix such that matrix glycoprotein serves to protect associated collagen from MMP-dependent degradation. In addition to mediating significant collagenolysis, MMP activity was further implicated in the dissolution of matrix tropoelastin. Urokinase/plasmin activity was not found to be required for MMP-zymogen activation.
Insights
This study reveals how urokinase and matrix metalloproteinases (MMPs) work together to drive melanoma invasion. Urokinase clears matrix glycoproteins, enabling MMPs to degrade collagen and elastin, crucial steps in tumor metastasis.
Area of Science:
- Oncology
- Biochemistry
- Cell Biology
Background:
- Malignant tumors often show high levels of urokinase and matrix metalloproteinase (MMP) activity.
- Understanding the interplay between these enzymes is crucial for explaining tumor invasion.
Purpose of the Study:
- To investigate the combined role of urokinase and MMPs in the invasive behavior of human melanoma cells (M24met).
- To elucidate the sequential contribution of these enzyme systems to extracellular matrix degradation.
Main Methods:
- Utilized a highly metastatic human melanoma cell line (M24met).
- Employed specific inhibitors: tissue inhibitor of metalloproteinases-2 and plasminogen activator inhibitor-2.
- Analyzed the degradation of various extracellular matrix components.
Main Results:
- M24met cells secrete multiple MMPs and urokinase.
- Combined urokinase and MMP activity enables degradation of interstitial and basement membrane matrices.
- Urokinase-dependent glycoprotein removal precedes MMP-dependent collagenolysis.
- MMP activity also contributes to tropoelastin dissolution.
Conclusions:
- Coexpression of urokinase and MMPs is critical for melanoma cell invasion and extracellular matrix degradation.
- A specific temporal sequence exists where urokinase activity facilitates MMP action.
- Matrix structure influences the enzymatic degradation cascade, with glycoproteins protecting collagen.