Related Experiment Videos
The process of malignant progression in human breast cancer
R Clarke1, R B Dickson, N Brünner
1Vincent T. Lombardi Cancer Research Center, Georgetown University Medical Center, Washington.
Abstract:
Malignant progression in breast cancer represents the processes through which localized, hormone-dependent tumor cells become resistant to endocrine manipulations and metastasize to sites distant from the primary tumor. By selection in ovariectomized athymic nude mice, we have isolated a variant (MIII) of the hormone-dependent, poorly invasive, human breast cancer cell line MCF-7. MIII cells have lost their absolute requirement for estrogen to form proliferating tumors in nude mice. Furthermore, these tumors are significantly more invasive than the parental MCF-7 cell line. MIII cells retain some responsivity to estrogens and antiestrogens, indicating that they have progressed to a hormone-independent but hormone-esponsive phenotype. In an attempt to determine the nature of this process, we have compared the phenotype of MIII cells with that of other MCF-7 variants. These comparisons strongly suggest that the factors contributing to perturbations in antiestrogen sensitivity, hormone-dependent growth, metastatic potential and tumorigenicity are essentially independent of each other and acquired in a random manner. Loss of estrogen receptor expression and overexpression of EGF receptors tend to occur later in the process of malignant progression.
Insights
Researchers identified a new breast cancer cell variant (MIII) that is more invasive and less dependent on estrogen. This progression involves independent acquisition of traits like altered hormone sensitivity and metastatic potential.
Area of Science:
- Oncology
- Cell Biology
- Endocrinology
Background:
- Malignant progression in breast cancer involves hormone-dependent cells becoming resistant to treatment and metastasizing.
- Understanding these changes is crucial for developing effective breast cancer therapies.
Purpose of the Study:
- To isolate and characterize a variant of the MCF-7 human breast cancer cell line exhibiting malignant progression.
- To investigate the phenotypic changes associated with acquired hormone independence and increased invasiveness.
Main Methods:
- Selection of a variant (MIII) from the MCF-7 cell line in ovariectomized athymic nude mice.
- Comparative phenotypic analysis of MIII cells with parental MCF-7 cells and other variants.
Main Results:
- The MIII variant lost its absolute estrogen requirement for tumor formation and showed significantly increased invasiveness.
- MIII cells maintained partial responsiveness to estrogens and antiestrogens, indicating a hormone-independent yet hormone-responsive phenotype.
- Factors contributing to altered hormone sensitivity, growth, and metastasis appear to be acquired independently and randomly.
Conclusions:
- Malignant progression in breast cancer involves the acquisition of multiple independent traits.
- Loss of estrogen receptor and overexpression of EGF receptors may occur later in this progression process.