Kynurenine induced E-cadherin degradation in an AhR- and Skp2-dependent pathway. (A) MCF-7 cells were incubated with kynurenine for 6 hours, and cellular proteins were harvested. AhR protein was immunoprecipitated by specific antibody, and the binding of E-cadherin and Skp2 was studied with Western blotting. (B) Cells were incubated with kynurenine or 3-methylcholanthrene (an AhR agonist) for 6 hours, and the co-localization of E-cadherin and AhR was studied with confocal microscopy. (C) Cells were treated with Skp2 shRNA for 24 hours and then incubated with kynurenine for another 48 hours. The protein levels of Skp2, E-cadherin, and AhR were determined with Western blotting and normalized to actin level. (D) Cells were incubated with kynurenine, 3′4′-dimethoxyflavone (3′4′-DMF, an AhR antagonist) or both drugs for 24 hours. E-cadherin protein level was investigated with Western blotting. (E) Cells were also collected and subjected to migration assay. *P < 0.05.