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Occurrence of the tumor-specific, calcium-binding protein, oncomodulin, in virally transformed normal rat kidney
Abstract:
Oncomodulin, an apparently tumor-specific calcium-binding protein, has been detected in many chemically induced rat hepatomas. It is now possible to detect, by radioimmunoassay and immunofluorescence, the presence of oncomodulin in normal rat kidney cells virally transformed by avian sarcoma virus. By contrast, it was not detected in uninfected, nonneoplastic normal rat kidney cells. The protein was isolated and purified by a novel high-performance liquid chromatography procedure and shown to be identical to that isolated previously from rat hepatoma. The cellular levels of oncomodulin approached the levels of calmodulin in avian sarcoma virus-transformed normal rat kidney cells, suggesting that the total calcium-binding activity of the cell may play a role in expression of the transformed phenotype.
Insights
Oncomodulin, a tumor-associated protein, is found in virus-transformed kidney cells, not normal ones. Its levels in transformed cells suggest calcium-binding proteins influence cell transformation.
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Oncomodulin is a calcium-binding protein primarily found in rat hepatomas.
- Its presence in non-tumorigenic cells has not been previously established.
Purpose of the Study:
- To investigate the presence of oncomodulin in virally transformed rat kidney cells.
- To characterize oncomodulin isolated from transformed cells and compare it to tumor-derived oncomodulin.
- To explore the potential role of oncomodulin in cellular transformation.
Main Methods:
- Radioimmunoassay and immunofluorescence were used to detect oncomodulin.
- High-performance liquid chromatography (HPLC) was employed for protein isolation and purification.
- Cellular levels of oncomodulin were compared to calmodulin.
Main Results:
- Oncomodulin was detected in normal rat kidney cells transformed by avian sarcoma virus.
- Oncomodulin was absent in uninfected, nonneoplastic normal rat kidney cells.
- Purified oncomodulin from transformed cells was identical to that from rat hepatoma.
- Oncomodulin levels in transformed cells approached those of calmodulin.
Conclusions:
- Viral transformation can induce oncomodulin expression in non-neoplastic cells.
- Oncomodulin is a valid marker for cellular transformation.
- Elevated calcium-binding activity, including oncomodulin, may contribute to the transformed phenotype.