Figure 5. Fraxetin induced STAT3 inactivation by occupying its SH2 domain in vitro and in vivo. (A) The expression of STAT3 in PDA tissues and adjacent normal tissues in the GEPIA 2 database was analyzed. (B) The correlation between STAT3 expression and KRAS activity in the GEPIA 2 database was evaluated. (C) The expression and phosphorylation of STAT3 in a normal pancreatic ductal cell (hTERT-HPENKRAS(-)) and PCCs (PANC-1KRAS G12D, Patu8988KRAS G12V and BxPc-3KRAS(-)) (D) JAK2 and STAT3 expression and phosphorylation in PANC-1 and Patu8988 cells with and without fraxetin treatment, as seen on a Western blot. (E) Immunocytochemical staining of STAT3 in PANC-1 and Patu8988 cells with or without fraxetin treatment. Bar = 50 μm. (F) Western blot analysis showing the expression and phosphorylation of JAK2 and STAT3 in fraxetin-treated animal xenograft models. The overview of Fraxetin binding in the STAT3 SH2 domain by using UCSF chimera. (G) Sequence analysis indicates that the STAT3 protein harbor conserved motifs, such as the DNA binding region and SH2 domain. (H) The overview of Fraxetin binding in the STAT3 SH2 domain by using UCSF chimera. (I) 3D representation of fraxetin binding sites in the STAT3 SH2 domain (yellow dotted line means hydrogen bond) by using PyMol. (J) Detailed 2D representation of fraxetin binding sites in STAT3 SH2 domain residues interactions generated by LigPlot plus. Data were presented as the mean ± standard deviation, and were analyzed by One-way ANOVA with Bonferroni’s post-hoc test and two-sided Student’s t-test. *P < 0.05, **P < 0.01, ***P < 0.001.