Baicalein Has Protective Effects On The 17 ?-estradiol-induced Transformation Of Breast Epithelial Cells By Interfering With Estrogen Receptor-?-and G-protein Coupled Estrogen Receptor 30-mediated Signaling Transduction

Objective: Baicalein,the primary flavonoid derived from the roots of Scutellaria baicalensis Georgi,exerts anticancer effects in breast cancer.In the current study,the long-term exposure of breast epithelial cells to 17?-estradiol(E2)was used to investigate the chemopreventive potential of baicalein on neoplastic transformation.Moreover,what this thesis attempts to probe into is whether baicalein can suppresses 17-?-estradiol-induced neoplastic transformation by interfering with estrogen receptor-?-and G-protein coupled estrogen receptor 30-mediated signaling transduction.Methods: Cells were continuously cultured for 5-10 weeks with E2 or E2 plus baicalein in vitro to develop two cell model system.Cell growth were examined on four consecutive days using trypan blue dye exclusion;Wound-healing assay was analyzed cells migration capacity;Transwell chamber assays were used to test the ability of cells to invade through Matrigel-coated filters;3D epithelial culture model provides technique for studying the features of the breast epithelium in vivo,as well as the features of malignant transformation;Model cells were transferred to soft agar or mammary fat pads of female NOD/SCID mice to assess the inhibitory effects of baicalein on E2-induced tumorigenic ability in vivo and in vitro;SWISS-MODEL and Sybyl-X 1.2 were used to evaluate the potential affinity of E2 and baicalein for the Ligand binding domains(LBDs)of ER? and GPR30;The intracellular localization of ER? was analyzed by using immunofluorescence microscopy and electrophoretic mobility shift assay(EMSA).Western blotting and RT-PCR were performed to detect E2-induced ER? and GPR30-mediated signal transduction and target gene expression.Results:(1)Baicalein inhibits E2-enhanced cell growth,migration,and invasion in mammary epithelial cells.(2)Baicalein protectsE2-disrupted acini grown in 3D cultures.(3)Baicalein impedes E2-induced tumorigenesis in vitro and in vivo.(4)Molecular modeling and docking study demonstrate that baicalein and E2 showed the ability to bind to both ER? and GPR30.(5)Baicalein inhibits E2-induced ER? nuclear translocation and transcriptional activity.(6)Baicalein prevents E2-induced GPR30-mediated signal transduction and gene expression.Conclusion: The current results demonstrated that baicalein inhibits E2-induced neoplastic transformation and the cancerous phenotype of the breast epithelium.Moreover,baicalein suppressed the E2-mediated activation of two key regulatory pathways involved in breast carcinogenesis: ER? and GPR30.Targeting the two pathways simultaneously could represent a novel promising pharmacological approach for the chemoprevention of estrogen-dependent breast cancer that expresses one or both receptors from the onset or following tumor progression.