Estrogen sensitive breast cancer cells

Most steroid-sensitive cancers express specific cell surface receptors. Prednisone-sensitive lymphomas, estrogen-sensitive breast cancers, and prostatic cancers express specific receptors for corticosteroids, estrogens, and androgens, respectively. It is now possible to assay tumor specimens for steroid receptor content and to identify which individual patients are likely to benefit from hormonal therapy. Measurement of the estrogen receptor (ER) and progesterone receptor (PR) proteins in breast cancer tissue is now standard clinical practice. ER or PR positivity predicts response to hormonal therapy, whereas patients whose tumors are ER-negative generally fail to respond to such treatment. 

Wu X et al (2011) Estrogen receptor-beta sensitizes breast cancer cells to the anti-estrogenic actions of endoxifen. Breast Cancer Res 13 R27... 

The test system was considerably less sensitive to endosulfan when mouse ER, rather than human ER, was used to mediate (3-gal activity (Ramamoorthy et al. 1997). In similar assays, endosulfan at 10 jM had no effect on (3-gal activity in yeast Saccharomyces) transfected with either the human or rainbow trout ER (Andersen et al. 1999). In addition, no effect was observed on transcriptional activation of HeLa cells transfected with plasmids containing an estrogen receptor as a responsive element (Shelby et al. 1996). Endosulfan also did not induce transient reporter gene expression in MCF-7 human breast cancer cells at an incubation concentration of 2.5 pM (Andersen et al. 1999). Maximum endosulfan-induced ER-mediated luciferase reporter gene expression occurred in vitro in a T47D human breast adenocarcinoma cell line at approximately 10 pM, while 50% expression of luciferase occurred at about 5.9 pM the maximum expression was approximately 59% of the effect from exposure to 0.03 nM estradiol (0.00003 pM) (Legler et al. 1999). Luciferase expression from combined treatment with endosulfan and dieldrin was additive over concentrations ranging from 3 to 8 pM. 

Mai Z, Blackburn GL, Zhou JR (2007) Genistein sensitizes inhibitory effect of tamoxifen on the growth of estrogen receptor-positive and HER2-overexpressing human breast cancer cells. Mol Carcinog 46 534-542... 

Wang LH, et al. Disruption of estrogen receptor DNA-binding domain and related intramolecular communication restores tamoxifen sensitivity in resistant breast cancer. Cancer Cell. 2006 10 487-499. 

The majority of patients with disseminated ERP+ breast cancer will respond to hormonal manipulation. With subsequent relapses many of these patients respond to additional hormonal therapy. It is postulated that breast cancer is a heterogenous disease composed of hormone-sensitive and hormone-resistant clones, and that measurement of the estrogen receptor protein identifies the dominant cell population. Megestrol acetate (MEG) treatment of advanced breast cancer has achieved tumor regression in sensitive patients (M9). 

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