Inhibition of STAT3/IL-4 signaling restored sensitivity to osimertinib. (a). Western blot shows STAT3 expression in the PC-9 L792Fcis cells transfected with scramble, sgSTAT3#1, sgSTAT3#2, or sgSTAT3#3, and IL-4 expression in the PC-9 L792Fcis cells transfected with scramble, sgIL4#1, sgIL4#2, or sgIL4#3. (b-c) Representative cell viability curve and osimertinib IC50 value in the PC-9 L792Fcis cells transfected with scramble, sgSTAT3#2 or sgSTAT3#3 (b, n=3, p=0.001 or 0.0007, respectively. Statistical differences were evaluated using t test.), and in the PC-9 L792Fcis cells transfected with scramble, sgIL4#2 or sgIL4#3 (c, n=3, p=0.0006 or 0.001, respectively. Statistical differences were evaluated using t test.), under osimertinib treatment for 72 h. (d-e). Tumor growth curves and tumor images of the PC-9 L792Fcis-scramble, PC-9 L792Fcis-sgSTAT3#2, PC-9 L792Fcis-sgSTAT3#3 (d) (n=5, p=0.01 or 0.001, respectively. Statistical differences were evaluated using t test), and PC-9 L792Fcis-scramble, PC-9 L792Fcis-IL4#2, and PC-9 L792Fcis-IL4#3 (e) (n=6, p=1E-08 or 9E-08, respectively. Statistical differences were evaluated using t test) in the nude mice with osimertinib (10 mg/kg, 5 days a week) treatment. Scale bar, 2 cm. (f-h). Growth curve (f), tumor images (g), and tumor weight (h, n=5, p=0.0012 or 0.0028, respectively. Statistical differences were evaluated using t test.) of PC-9 L792Fcis xenografts treated with osimertinib (10 mg/kg, 5 days a week), osimertinib (10 mg/kg, 5 days a week) + STAT3 inhibitor (SH-4-54, [10 mg/kg, twice a week]), and osimertinib (10 mg/kg, 5 days a week) + IL-4 receptor antibody (dupilumab, 10 mg/kg, twice a week). Scale bar, 2 cm. (i). Inhibitory rates of SH-4-54 and dupilumab for PC-9 L792Fcis xenografts. (j-k). Images of H&E (upper panel in j), immunohistochemistry staining for CD206 (down panel in j) and CD206+/F4-80+ macrophages fractions in PC-9 L792Fcis xenografts treated with osimertinib, osimertinib + SH-4-54, and osimertinib + dupilumab (k). Scale bar, 50 μm.