Conjugated linoleic acid induces apoptosis through estrogen receptor alpha in human breast tissue
Conjugated linoleic acid (CLA), a naturally occurring fatty acid found in ruminant products such as milk and beef, has been shown to possess anti-cancer activities in in vivo animal models and in vitro cell culture systems. In human breast cancer, the overall duration of estrogen exposure is the most important risk factor for developing estrogen-responsive breast cancer.
Accordingly, it has been suggested that estrogen exposure reduces apoptosis through the up-regulation of the anti-apoptosis protein, Bcl-2. Bcl-2, an anti-apoptotic protein, regulates apoptosis and plays a crucial role in the development and growth regulation of normal and cancerous cells.
Our research interest is to examine the effects of CLA on the induction of apoptosis in human breast tissues.
Methods: The localization of Bcl-2 in both normal and cancerous human breast tissues was determined by immunohistochemical staining and the Bcl-2 protein expression was tested by western blot analysis.
Co-culture of epithelial cells and stromal cells was carried out in the presence or absence of CLA to evaluate apoptosis in the context of a cell-cell interaction.
Results: The results showed that both normal and cancerous breast tissues were positive for Bcl-2 staining, which was higher overall in mammary ducts but very low in the surrounding stromal compartment.
Interestingly, by quantifying the western blot data, basal Bcl-2 protein levels were higher in normal breast epithelial cells than in cancerous epithelial cells. Furthermore, treatment with 17 beta-estradiol (E2) stimulated growth, decreased apoptosis and up-regulated Bcl-2 expression in estrogen responsive breast epithelial cells; however, these carcinogenic effects were diminished by either CLA or 4-Hydroxytamoxifen (Tam) and were suppressed further by the combination of CLA and Tam.
In both one cell type cultured and co-culture systems, CLA decreased cell proliferation in ER alpha transfected MDA-MB-231 cells but not in the wild type MDA-MB-231 cells.
Conclusions: These data, therefore, demonstrate that ER alpha plays important roles in CLA induced apoptosis in human breast tissues.
Author: Li-Shu Wang, Yi-Wen Huang, Suling Liu, Pearlly Yan and Young C Lin
Credits/Source: BMC Cancer 2008, 8:208
Published on: 2008-07-24
Copyright by the authors listed above - made available via BioMedCentral (Open Access). Please
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