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Expression and tissue localization of membrane-types 1, 2, and 3 matrix metalloproteinases in human invasive breast
1Department of Molecular Immunology, School of Medicine, Kanazawa University, Ishikawa, Japan.
Abstract:
Activation of the zymogen of matrix metalloproteinase 2 (proMMP-2, progelatinase A) possibly is one of the key steps in invasion and metastasis of various human carcinomas. Three different membrane-type MMPs (MT-MMPs), MT1-, MT2-, and MT3-MMPs are thought to be activators of proMMP-2 in the tissues. MT4-MMP is structurally different from the other three enzymes, and its function as proMMP-2 activator is uncertain. In the present study of human invasive breast carcinomas, we examined a correlation between the expression of MT1-, MT2-, and MT3-MMPs, immunolocalization of MT1- and MT2-MMPs, and proMMP-2 activation. Northern blot analysis demonstrated the predominant expression of MT1-MMP mRNA in carcinoma tissues (20 of 20 cases), whereas MT2-MMP was detected in only 25% of the cases (5 of 20 cases), and no detectable expression of MT3-MMP was observed. The expression levels of MT1-MMP but not MT2-MMP correlated well with the presence of lymph node and distant metastases, clinical stages, and size of tumors. Immunohistochemically, MT1-MMP was localized predominantly in the carcinoma cells in all of the samples (32 of 32 cases). Immunostaining of MT2-MMP in the carcinoma cells was observed in only 38% of the cases (12 of 32 cases). Immunoblot analysis of tumor homogenates confirmed the presence of these MT-MMPs. Activation of proMMP-2 was significantly higher in the carcinoma samples with lymph node or distant metastasis compared to carcinoma without metastasis, normal control, or fibrocystic disease (P < 0.05). An increase in the activation ratio of proMMP-2 correlated directly with the expression of MT1-MMP but not MT2-MMP, as measured by either Northern blot analysis or immunostaining. These results suggest that MT1-MMP may play a key role in human breast carcinoma invasion and metastasis by being predominantly responsible for activation of proMMP-2.
Insights
Matrix metalloproteinase 1 (MT1-MMP) activation of progelatinase A (proMMP-2) is crucial for breast carcinoma invasion and metastasis. MT1-MMP expression strongly correlates with advanced tumor stage and metastasis, suggesting its key role in proMMP-2 activation.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Activation of matrix metalloproteinase 2 (proMMP-2) is a critical step in the invasion and metastasis of human carcinomas.
- Membrane-type MMPs (MT-MMPs), including MT1-, MT2-, and MT3-MMPs, are implicated as proMMP-2 activators.
- The specific role of MT4-MMP in proMMP-2 activation remains uncertain due to its distinct structure.
Purpose of the Study:
- To investigate the correlation between the expression and localization of MT1-, MT2-, and MT3-MMPs and proMMP-2 activation in human invasive breast carcinomas.
- To determine the specific role of MT1-MMP and MT2-MMP in breast cancer progression and metastasis.
Main Methods:
- Northern blot analysis was used to assess the mRNA expression levels of MT1-, MT2-, and MT3-MMPs in carcinoma tissues.
- Immunohistochemistry was employed to determine the cellular localization of MT1-MMP and MT2-MMP.
- Immunoblot analysis confirmed the presence of MT-MMPs in tumor homogenates, and proMMP-2 activation ratios were quantified.
Main Results:
- MT1-MMP mRNA was predominantly expressed in all carcinoma tissues (20/20), while MT2-MMP was detected in 25% (5/20), and MT3-MMP was not detected.
- Higher MT1-MMP expression correlated significantly with lymph node/distant metastases, advanced clinical stages, and larger tumor size.
- Increased proMMP-2 activation ratios directly correlated with MT1-MMP expression, but not MT2-MMP expression.
Conclusions:
- MT1-MMP is predominantly expressed in breast carcinoma cells and its expression levels are closely linked to tumor metastasis.
- MT1-MMP plays a significant role in the activation of proMMP-2 within the tumor microenvironment.
- These findings suggest MT1-MMP is a key driver of invasion and metastasis in human breast carcinomas through proMMP-2 activation.