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Independent molecular pathways in initiation and loss of hormone responsiveness of breast carcinomas
S Sukumar1, W P Carney, M Barbacid
1Developmental Oncology Section, Basic Research Program, Frederick Cancer Research Facility, MD 21701.
Abstract:
These studies were set up to determine whether those oncogenes participating in the initiation of mammary carcinogenesis (for example, ras oncogenes) play a direct role in the outcome of events associated with the late stages of tumor development such as loss of hormone dependency. Mammary carcinomas induced by a single carcinogenic insult in pubescent rats was selected as an in vivo model system with direct relevance to human breast cancer. Acquisition of hormone-independent growth in these carcinogen-induced tumors was found to be independent of the activation of ras oncogenes during the early stages of carcinogenesis. In agreement with these observations, introduction of a human ras oncogene into human MCF-7 breast carcinoma cells did not abrogate their hormonal dependency for growth in vivo. These findings suggest that those events responsible for the critical stages of breast cancer development occur independently and in an uncoordinated manner.
Insights
Ras oncogenes do not drive hormone-independent growth in breast cancer. These findings suggest critical breast cancer development stages occur independently.
Area of Science:
- Oncology
- Molecular Biology
- Carcinogenesis
Background:
- Oncogenes, such as ras oncogenes, are implicated in initiating mammary carcinogenesis.
- Understanding the role of oncogenes in late-stage tumor development, like hormone independence, is crucial for breast cancer research.
Purpose of the Study:
- To investigate if ras oncogenes directly influence hormone-independent growth in late-stage mammary tumors.
- To determine the role of oncogene activation in the progression of breast cancer.
Main Methods:
- Utilized a rat model of mammary carcinogenesis induced by a single carcinogenic insult.
- Introduced a human ras oncogene into human MCF-7 breast carcinoma cells for in vivo growth studies.
Main Results:
- Acquisition of hormone-independent growth in carcinogen-induced rat mammary tumors was independent of ras oncogene activation.
- Introduction of a human ras oncogene into MCF-7 cells did not affect their hormonal dependency for in vivo growth.
Conclusions:
- Ras oncogene activation during early carcinogenesis does not appear to dictate hormone-independent growth in later stages.
- Critical events in breast cancer development, including hormone independence, may occur independently and without coordination.