title: Role of GPR30 in the mechanisms of tamoxifen resistance in breast cancer MCF-7 cells.
abstract: Tamoxifen is the most frequently used anti-hormonal drug for treatment of women with hormone-dependent breast cancer. The aim of this study is to investigate the mechanism of tamoxifen resistance and the impact of the new estrogen G-protein coupled receptor (GPR30). MCF-7 cells were continuously exposed to tamoxifen for 6 months to induce resistance to the inhibitory effect of tamoxifen. These tamoxifen-resistant cells (TAM-R) exhibited enhanced sensitivity to 17-ss-estradiol and GPR30 agonist, G1, when compared to the parental cells. In TAM-R cells, tamoxifen was able to stimulate the cell growth and MAPK phosphorylation. These effects were abolished by EGFR inhibitor AG1478, GPR30 anti-sense oligonucleotide, and the selective c-Src inhibitor PP2. Only EGFR basal expression was slightly elevated in the TAM-R cells, whereas GPR30 expression and the basal phosphorylation of Akt and MAPK remained unchanged when compared to the parental cells. Interestingly, estrogen treatment significantly increased GPR30 translocation to the cell surface, which was stronger in TAM-R cells. Continuous treatment of MCF-7 cells with GPR30 agonist G1 mimics the long-term treatment with tamoxifen and increases drastically its agonistic activity. This data suggests the important role of GPR30/EGFR receptor signaling in the development of tamoxifen resistance. The inhibition of this pathway is a valid option to improve anti-hormone response in breast cancer.
authors.affiliation: Department of Obstetrics and Gynecology, Otto-von-Guericke University, G-Hauptmann Str 35, 39108 Magdeburg, Germany. atanas.ignatov@med.ovgu.de
authors.forename: Atanas
authors.initials: A
authors.lastname: Ignatov
authors.forename: Tanja
authors.initials: T
authors.lastname: Ignatov
authors.forename: Albert
authors.initials: A
authors.lastname: Roessner
authors.forename: Serban Dan
authors.initials: SD
authors.lastname: Costa
authors.forename: Thomas
authors.initials: T
authors.lastname: Kalinski
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011960:Receptors, Estrogen; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013629:Tamoxifen / Q000494:pharmacology*
chemical_list: C109584:GPER1 protein, human; D011960:Receptors, Estrogen; D043562:Receptors, G-Protein-Coupled; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D066246:ErbB Receptors