Identification of a natural product-like STAT3 dimerization inhibitor by structure-based virtual screening

OBJECTIVE To apply molecular docking techniques to identify STAT3 inhibitors from a database of over 90 000 natural product and natural product-like compounds.METHODS Molecular docking was used for the virtual screening campaign and hit validation of STAT3 inhibitor.To further evaluate the potency of candidates at inhibiting STAT3-DNA binding activity,a STAT3 and STAT1transcription factor ELISA was performed.A dual-luciferase reporter assay,co-immunoprecipitation assay and Western blotting were carried out for the investigation of effect of compound 1 on STAT3-driven transcription,STAT3 dimerization and STAT3 phosphorylation.Finally,the cell toxicity of compound 1 was assessed by using MTT assay on different cell lines.RESULTS The virtual screening campaign furnished fourteen hit compounds,from which compound 1 emerged as a top candidate.Compound 1inhibited STAT3DNA-binding activity in vitro and attenuated STAT3-directed transcription in cellulo with selectivity over STAT1 and comparable potency to the wellknown STAT3 inhibitor S3I-201.Furthermore,compound 1 inhibited STAT3 dimerization and decreased STAT3 phosphorylation in cells without affecting STAT1 dimerization and phosphorylation.Compound 1 also exhibited selective anti-proliferative activity against cancer cells over normal cells in vitro.CONCLUSION The benzofuran derivative 1 was identified as a potential inhibitor of STAT3 dimerization using in silico screening.Molecular docking analysis suggested that compound 1 might putatively function as an inhibitor of STAT3 dimerization by binding to the SH2 domain.To the best of our knowledge,compound 1 has not been reported as a STAT3 inhibitor and no biological activity of compound 1 has been presented in the literature.