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Transformation of human mammary epithelial cells by oncogenic retroviruses
R Clark1, M R Stampfer, R Milley
1Cetus Corporation, Emeryville, California 94608.
Abstract:
We have introduced viral oncogenes into human mammary epithelial cells through the use of murine retroviruses. A continuous cell line (184A1N4) derived from benzo(a)pyrene treatment of normal breast epithelial cells was used as a recipient for the ras, mos, and T-antigen oncogenes. Each of these oncogenes enabled the 184A1N4 cells to grow in a selective medium, thus demonstrating the potential utility of these cells for oncogene detection and isolation. 184A1N4 cells transformed by T-antigen were nontumorigenic in athymic mice, but v-ras transformants were weakly tumorigenic. Transformants bearing both the T-antigen and ras oncogenes were strongly tumorigenic, however. The karyotype of these double transformants shows a high degree of stability. These results demonstrate the stepwise acquisition of the fully malignant phenotype by normal human epithelial cells in vitro.
Insights
Viral oncogenes like ras and T-antigen were introduced into human breast cells. These oncogenes facilitated cell growth and, when combined, led to a stable, malignant cell phenotype, demonstrating stepwise cancer development.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Human mammary epithelial cells are crucial for understanding breast cancer development.
- Viral oncogenes play a significant role in cellular transformation and tumorigenesis.
- Benzo(a)pyrene is a known carcinogen that can induce genetic mutations.
Purpose of the Study:
- To investigate the role of specific viral oncogenes (ras, mos, T-antigen) in transforming human mammary epithelial cells.
- To establish a model system for studying the stepwise acquisition of malignancy in human epithelial cells.
- To assess the tumorigenic potential and karyotypic stability of oncogene-transformed cells.
Main Methods:
- Introduction of viral oncogenes (ras, mos, T-antigen) into a human mammary epithelial cell line (184A1N4) using murine retroviruses.
- Selection of transformed cells based on their ability to grow in a selective medium.
- In vivo tumorigenicity assays using athymic mice.
- Karyotype analysis of double transformants.
Main Results:
- Individual oncogenes (ras, T-antigen) conferred the ability to grow in selective medium.
- T-antigen transformed cells were non-tumorigenic, while v-ras transformants were weakly tumorigenic.
- Cells co-expressing T-antigen and ras oncogenes were strongly tumorigenic and exhibited stable karyotypes.
- Demonstrated stepwise acquisition of the malignant phenotype.
Conclusions:
- Viral oncogenes can induce transformation and tumorigenesis in human mammary epithelial cells.
- The combination of specific oncogenes leads to a fully malignant phenotype with stable genetic characteristics.
- This study provides a valuable in vitro model for dissecting the molecular mechanisms of human epithelial cancer progression.