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NIH/3T3 cells transfected with human tumor DNA containing activated ras oncogenes express the metastatic phenotype in
Abstract:
NIH/3T3 cells transfected with DNA from malignant human tumors produced experimental and spontaneous metastases in nude mice. In contrast, parent or spontaneously transformed NIH/3T3 cells failed to metastasize. The transfected clones contained either activated c-Harvey-ras or N-ras oncogenes. A representative clone (T71-17SA2) which was used to assess selected cellular and host factors relevant to the metastatic process produced lung metastases in 100% of the NIH nude mice recipients, secreted augmented levels of type IV collagenase, and invaded human amnion basement membrane in vitro. Expression of the metastatic phenotype was not related to decreased sensitivity to natural killer cells or macrophage-mediated cytotoxicity. Analysis of the cellular DNA from the T71-17SA2 transfectant and its corresponding metastases, both of which contained activated N-ras oncogenes, revealed a twofold increase in the N-ras-specific DNA sequences in the metastatic cells. Thus, transfection with human tumor DNA containing activated ras oncogenes can induce the complete metastatic phenotype in NIH/3T3 cells by a mechanism apparently unrelated to immune cell killing.
Insights
Activated ras oncogenes in human tumor DNA can induce cancer cells to metastasize. This study shows that ras oncogenes promote the complete metastatic phenotype in NIH/3T3 cells, independent of immune responses.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Metastasis is a complex process involving multiple genetic and cellular changes.
- Ras oncogenes are frequently implicated in cancer development and progression.
- Understanding the genetic drivers of metastasis is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate whether activated ras oncogenes can induce the metastatic phenotype in NIH/3T3 cells.
- To identify cellular and host factors associated with metastasis induced by ras oncogenes.
- To determine the role of N-ras gene amplification in the metastatic process.
Main Methods:
- Transfection of NIH/3T3 cells with DNA from human malignant tumors.
- In vivo metastasis assays in nude mice.
- In vitro invasion assays using human amnion basement membrane.
- Analysis of cellular DNA for oncogene copy number and expression.
Main Results:
- NIH/3T3 cells transfected with human tumor DNA containing activated c-Harvey-ras or N-ras oncogenes formed experimental and spontaneous metastases in nude mice.
- A specific transfectant clone (T71-17SA2) exhibited a 100% lung metastasis rate, increased type IV collagenase secretion, and invaded basement membranes in vitro.
- Metastasis was not linked to reduced sensitivity to natural killer cells or macrophages.
- Metastatic cells showed a twofold increase in N-ras DNA sequences, suggesting gene amplification.
Conclusions:
- Activated ras oncogenes are sufficient to confer the complete metastatic phenotype on NIH/3T3 cells.
- The metastatic process induced by ras oncogenes appears to be independent of immune surveillance.
- N-ras gene amplification may contribute to the metastatic potential of cancer cells.