Figure 4 Regulation of tyrosine kinase activity on the transcription and expression levels of PSMB8 and its alternatively spliced isoforms (A) JHU-011 cells and FaDu cells were divided into 5 groups. In the IFN-γ+/Nilo+ group, nilotinib was first added and the cells were incubated for 24 h. Then IFN-γ was added and the cells were cultured for another 24 h. In the IFN-γ+/Nilo− group, the transcription level of PSMB8 was significantly upregulated compared to that in the control group (IFN-γ−/Nilo− group) (** P<0.01), while the transcription of PSMB8 in the IFN-γ−/Nilo+ group was inhibited (* P<0.05). (B) The protein expression of PSMB8 in the IFN-γ+/Nilo+ group was downregulated compared to that in the IFN-γ+/Nilo− group in FaDu cells (** P<0.01). (C) The protein expression of PSMB8 in the IFN-γ+/Nilo+ group was downregulated in JHU-011 cells (** P<0.01). (D) Nilotinib downregulated the induction effect of IFN-γ on isoform E2, and the percentage of isoform E2 was reduced (* P<0.05). In the DPH+ group, the transcription level of isoform E2 was higher than that in the control group (IFN-γ−/Nilo− group) (** P<0.01). Quantitative data are expressed as the mean±SD. (E) In FaDu cells, the regulation of nilotinib on the transcription of E2 was consistent with the results in JHU-011 cells (* P<0.05). (F) In the DPH+ group, protein expression of PSMB8 in JHU-011 cells and FaDu cells was elevated compared to that in the blank control group (** P<0.01). Each group contained 3 independent replicates.