Involvement of Jak-Stat signaling in upregulation of MUC4. (A) The expression of MUC4 in CD18 cells upon treatment with Nicotine, IFN-γ and RA were analyzed by agarose gel electrophoresis. Serum-starved CD18 cells were treated with 1 μM nicotine, IFN-γ and RA for the given time points. (B) MUC4 expression at protein level was analyzed in nicotine in combination of IFN-γ and also nicotine in combination with retinoic acid by western blot analysis and the quantification of the bands is shown below. (C) Kinetics (starting at 10 min - 2 h) of Phosphorylation status of Jak kinases at the protein level was analyzed by immunoblotting. (D) Kinetics (starting at 10 min - 2 h) of Phosphorylation status of Stat1 at the protein level was analyzed by immunoblotting. In addition, the levels of total Tyk2, Jak2 and Stat1 were also assessed by immunoblotting. β-actin was used as a loading control. All immunoblotting results are representative of two independent experiments.