From the article:
In a study using a first-of-its kind mouse model of aging that mimics breast cancer development in estrogen receptor-positive post-menopausal women, investigators at Georgetown Lombardi Comprehensive Cancer Center and colleagues have determined that over-expression, or switching on of the Esr1 gene, could lead to elevated risk of developing estrogen receptor-positive breast cancer in older women.
In a second study from the same research lab, investigators found that in the specially bred mice given anti-hormonal drugs (e.g., tamoxifen and letrozole) similar to those currently used by women to lower their breast cancer risk, the elevated risk of developing breast cancer due to over-expression of Esr1 could be lowered or reversed.
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“If validated in human studies, detection of over-expression of Esr1-related genes could be a new signature to add to current prognostic tools that would help post-menopausal women at risk for estrogen receptor-positive breast cancer decide what their best risk reduction strategy might be.”
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The investigators were guided in their study by the use of the PAM50 (Prediction Analysis of Microarray 50) prognostic tool. The tool reads a sample of the tumor and determines expression levels for a group of 50 genes. The scientists found that many genes related to proliferation of breast cancer cells in the PAM50 tool were significantly expressed only in Esr1 mice and this correlated with development of the same type of estrogen receptor-positive breast cancers that develop in humans, thereby giving them new evidence of which other genes might be implicated in inducing breast cancer in post-menopausal women. In current clinical practice, the results of the PAM50 test have helped predict the chance of metastasis for some ER-positive, HER2-negative breast cancers.