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Tumor cells of malignant fibrous histiocytomas express mRNA for laminin
1Department of Pathology, University of Oulu, Finland.
Abstract:
In situ hybridization was used on routinely processed paraffin-embedded tissue sections to study the synthesis of the basement membrane (BM) proteins laminin and type IV collagen in 14 cases of malignant fibrous histiocytoma (MFH). Complementary RNA probes coding for the pro-alpha 1 (IV) chain of human type IV collagen and the B1 chain of human laminin were used to detect the respective mRNAs. The results were correlated with the immunohistochemical reactivity of tumor cells to specific antibodies against the P1 fragment of laminin and the 7S domain of type IV collagen. Signals for the presence of laminin mRNA in atypical neoplastic tumor cells could be detected in 11 MFHs. None of the tumors could be shown to contain signals for type IV collagen mRNA in their cells, although such signals were detected in the endothelial cells of tumor capillaries. In the corresponding immunohistochemical stainings, nine MFHs showed intracytoplasmic staining of tumor cells for laminin and one tumor showed weak staining for type IV collagen in the neoplastic cells. The results show that the laminin immunoreactivity found in MFHs is due to synthesis in the tumor cells and not to endogenous uptake of this protein. Synthesis of laminin in the majority of MFHs is in accordance with the notion that these tumors originate from primitive mesenchymal cells in soft tissues.
Insights
Malignant fibrous histiocytoma (MFH) tumor cells synthesize laminin, a basement membrane protein, but not type IV collagen. This finding supports the theory that MFH originates from primitive mesenchymal cells.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Malignant fibrous histiocytoma (MFH) is a soft tissue sarcoma.
- Basement membrane (BM) proteins like laminin and type IV collagen are crucial for tissue structure.
- The origin of MFH and its synthesis of BM proteins are not fully understood.
Purpose of the Study:
- To investigate the synthesis of laminin and type IV collagen in MFH.
- To determine if MFH tumor cells produce these basement membrane proteins.
- To correlate molecular findings with immunohistochemical results.
Main Methods:
- In situ hybridization was performed on paraffin-embedded MFH tissue sections.
- Complementary RNA probes were used to detect messenger RNA (mRNA) for laminin and type IV collagen.
- Immunohistochemistry was employed to detect laminin and type IV collagen proteins.
Main Results:
- Laminin mRNA was detected in tumor cells of 11 out of 14 MFH cases.
- Type IV collagen mRNA was not found in MFH tumor cells but was present in capillary endothelial cells.
- Immunohistochemistry showed laminin in tumor cells of nine MFHs and type IV collagen in one MFH.
Conclusions:
- MFH tumor cells actively synthesize laminin.
- The observed laminin immunoreactivity in MFH is due to endogenous synthesis, not uptake.
- These findings support the hypothesis that MFH arises from primitive mesenchymal cells.