Study On The Screening Of Small Molecular Compounds Targeting To Ubiquitin-mediated Degradation Of Estrogen Receptor α And The Evaluation Of Its Antitumor Activity

Background: Breast cancer is a common tumor in women,and the incidence has increased significantly in recent years.The majority of breast cancer is hormone-dependent,and endocrine therapy is an important treatment method.Estrogen receptor inhibitor is the first-line drug for patients whose estrogen receptor is positive.Nowadays tamoxifen is the most widely used drug in clinical practice,but its resistance is the bottleneck in the later clinical application.The technology of proteolysis-targeting chimeric molecule(PROTAC)can be used to combine the target protein of estrogen receptor group with the ubiquitin ligase E3 and lead to the degradation of estrogen receptor.Objective: To screen out the suitable ligand for ubiquitin-mediated degradation of estrogen receptor and to evaluate its efficacy preliminarily.Methods: The fluorescence polarization technique was used to detect the binding activity of the compounds for screening with estrogen receptor alpha and beta,and the dual luciferase report gene assay system was used to detect the effect of the compound on the transcription activity of estrogen receptor alpha.Immunohistochemistry method and Western Blot were used to detect the expression of estrogen receptor alpha in MCF-7 cells.The effect of the compound on the proliferation of MCF-7 cells in vitro was detected by WST-1 method and the proliferation of MCF-7 cells in vivo was observed by an in-vitro subcutaneous transplantation breast tumor model in nude mice.Result: Among the compounds for screening,the 4g and 5g were strongly associated with estrogen receptor alpha and beta,and the selectivity of 4g to estrogen receptor alpha was stronger than tamoxifen.The results by dual luciferase report gene assay system showed that4 g had an antagonistic effect on estrogen receptor alpha,and had inhibitory effects on the proliferation of MCF-7 cells in patients with positive-expression estrogen receptor alpha and as well as on the development of tumor in mice transplanted with MCF-7 cells.Conclusion: Among the compounds for screening,the 4g and 5g were strongly associated with estrogen receptor alpha and beta,and the selectivity of 4g to estrogen receptor alpha was stronger than tamoxifen.The results by dual luciferase report gene assay system showedthat 4g had an antagonistic effect on estrogen receptor alpha,and had inhibitory effects on the proliferation of MCF-7 cells in patients with positive-expression estrogen receptor alpha and as well as on the development of tumor in mice transplanted with MCF-7 cells.