Karma Normal is a biopsy-based study of 161 healthy Karma participants without prior history of breast cancer. The overall aim of Karma Normal is to understand the biological mechanisms underlying mammographic density as a risk factor for breast cancer.
By analysing the histological composition and expression of hormone receptors in the healthy breast we found that high mammographic density was associated with higher amount of stroma and epithelium and less amount of fat, but was not associated with a change in epithelial proliferation or receptor status [Gabrielson, 2016]. Increased expressions of both epithelial PR and stromal ER were associated with a greater proportion of stroma, suggesting hormonal involvement in regulating breast tissue composition. We have also found that reproductive risk factors significantly influence the epithelial tissue compartment and expression of hormone receptors in later life, and that these changes remain after menopause [Gabrielson, 2018].
These studied provide deeper insights of the biological mechanisms by which risk factors influence breast tissue composition and expression of hormone receptors, and as a consequence the risk of breast cancer.
Gabrielson M, Chiesa F, Paulsson J, Strell C, Behmer C, Rönnow K, Czene K, Östman A, Hall P. Amount of stroma is associated with mammographic density and stromal expression of oestrogen receptor in normal breast tissues. Breast Cancer Res Treat. 2016 Jul;158(2):253-61. doi: 10.1007/s10549-016-3877-x. Epub 2016 Jun 27. PMID: 27349429
Gabrielson M, Chiesa F, Behmer C, Rönnow K, Czene K, Hall P. Association of reproductive history with breast tissue characteristics and receptor status in the normal breast. Breast Cancer Res Treat. 2018 Mar 30. doi: 10.1007/s10549-018-4768-0. PMID: 29603032