Icariin (ICA) and icaritin (ICT), with a similar structure to genistein, are the important bioactive components of the genus Epimedium, and regulate many cellular processes. In the present study, using the estrogen receptor (ER)-negative breast cancer cell line, SKBr3, as a model, we examined the hypothesis that ICA and ICT at low concentrations stimulate SKBr3 cell proliferation in vitro through the functional membrane, G protein-coupled estrogen receptor 1 (GPER1), mediated by the epithelial growth factor receptor (EGFR)-mitogen-activated protein kinase (MAPK) signaling pathway. MTT assay revealed that ICA and ICT at doses of 1 nM to 1 mu M markedly stimulated SKBr3 cell proliferation in a dose-dependent manner. The ICA- and ICT-stimulated cell growth was completely suppressed by the GPER1 antagonist, G-15, indicating that the ICA- and ICT-stimulated cell proliferation was mediated by GPER1 activation. Semi-quantitative RT-PCR analysis revealed that treatment with ICA and ICT enhanced the,transcription of c-fos, a proliferation-related early gene. The ICA- and ICT-stimulated mRNA expression was markedly attenuated by G-15, AG-1478 (an EGFR antagonist) or PD98059 (a MAPK inhibitor). Our data also demonstrated that ICA and ICT increased the phosphorylation of ERK1/2. The ICA- and ICT-stimulated ERK1/2 phosphorylation was blocked by pre-treatment of the cells with G-15 and AG-1478 or PD 98059. Flow cytometric analysis confirmed that the ICA- and ICT-stimulated SKBr3 cell proliferation involved the GPER1-mediated modulation of the EGFR-MAPK signaling pathway. To the best of our knowledge, our current findings demonstrate for the first time that ICA and ICT promote the progression of ER-negative breast cancer through the activation of membrane GPER1.
Chinese Acad Sci, Key Lab Plant Resources & Chem Arid Zone, Urumqi 830011, Xinjiang, Peoples R China;Chinese Acad Sci, Xinjiang Tech Inst Phys & Chem, State Key Lab Basis Xinjiang Indigenous Med Plant, Urumqi 830011, Xinjiang, Peoples R China;Shihezi Univ, Coll Pharm, Key Lab Xinjiang Endem Phytomed Resources, Minist Educ, Shihezi 832002, Peoples R China;Univ Alabama Birmingham, Dept Med, Vasc Biol & Hypertens Program, Birmingham, AL 35294 USA;Shihezi Univ, Sch Med, Shihezi 832002, Peoples R China
Ma, Hai-Rong,Wang, Jie,Chen, Yiu-Fai,et al. Icariin and icaritin stimulate the proliferation of SKBr3 cells through the GPER1-mediated modulation of the EGFR-MAPK signaling pathway[J]. INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE,2014,33(6):1627-1634.