Journal: Frontiers in Oncology
Article Title: The STAT3–ZEB1 axis contributes to CCL2-mediated resistance to osimertinib in lung cancer
doi: 10.3389/fonc.2026.1699471
Figure Lengend Snippet: Blocking CCR2–STAT3/ERK signaling restores osimertinib sensitivity (A) Western blot analysis of CCR2 expression in HCC827-CCL2 cells after transfection with CCR2 siRNA. Representative blots are shown from three independent biological experiments. (B) MTT assay showing reduced viability of HCC827-CCL2-si-CCR2 cells treated with osimertinib (48 h). Data represent the mean ± SD from three independent biological experiments, each performed in triplicate (***p < 0.001, Student’s t-test ). (C) Caspase-9 activity increased in CCR2-knockdown cells upon osimertinib treatment, measured by luminescent Caspase-Glo 9 assay. Data represent the mean ± SD from three independent experiments (***p < 0.001 vs. si-scramble, Student’s t-test ). (D) Western blot analysis of downstream signaling proteins (p-STAT3, p-ERK1/2, ZEB1) in HCC827-CCL2 cells treated with CCR2 antagonist INCB3344. Representative blots are shown from three independent experiments. (E) Combined treatment with osimertinib and INCB3344 decreased cell viability in HCC827-CCL2 cells (MTT assay). Data represent the mean ± SD from three independent biological replicates (*p < 0.05, Student’s t-test ). (F) INCB3344 enhanced caspase-9 activity upon osimertinib treatment. Data represent the mean ± SD from three independent biological experiments (**p < 0.01, Student’s t-test ). (G) HCC827-CCL2 cells treated with STAT3 inhibitor (S3I201, 40 μM, 24 h) were analyzed by Western blot for p-STAT3, p-ERK1/2, and ZEB1. Representative blots are shown from three independent experiments. (H) MTT assay showing that STAT3 inhibition sensitized HCC827-CCL2 cells to osimertinib treatment. Data represent the mean ± SD from three independent experiments (**p < 0.01, Student’s t-test ). (I) Tumor volume of H1975/AZD-18 xenografts treated with vehicle, osimertinib (1mg/kg/day), S3I201 (5mg/kg/2day), or a combination of both drugs for 16days (n = 5 in each subgroup). Data are presented as mean ± SE (*p < 0.05, Student’s t-test) . (J) Chromatin immunoprecipitation (ChIP) assay demonstrating STAT3 binding to the ZEB1 promoter in H1975/AZD-18 cells. Enrichment of ZEB1 promoter fragments was quantified by qPCR and normalized to IgG control. Data represent the mean ± SD from three independent experiments (*p < 0.05, Student’s t-test). (K) The expression of p-STAT3, p-ERK1/2, STAT3, ERK, and ZEB1 in HCC827-CCL2 cells with ERK inhibitor selumetinib was measured using Western blot analysis. Representative blots are shown from three independent experiments. (L) HCC872-CCL2 cells were treated with osimertinib and selumetinib treatment alone or in combination for 48 h; cell viability was determined using MTT assays. Data represent the mean ± SD from three independent experiments (**p < 0.001, Student’s t-test ).
Article Snippet: HCC827-CCL2 cells were generated by transfecting them with a plasmid carrying human CCL2 cDNA (SC118317, Origene, Rockville, MD).
Techniques: Blocking Assay, Western Blot, Expressing, Transfection, MTT Assay, Activity Assay, Knockdown, Inhibition, Chromatin Immunoprecipitation, Binding Assay, Control