Fig. 1: Downregulation of IL-6 renders cancer cells sensitive to genotoxic treatments.

A IL-6 mRNA levels in lung adenocarcinomas with different histological grades were investigated using the GSE68465 dataset and their log₂-transformed values were compared among well (n = 60), moderately (n = 209), and poorly (n = 167) differentiated tumors. B Kaplan–Meier analysis of the relationship between IL-6 gene expression and disease-free survival (DFS) in lung cancer patients from the GSE30219 cohort. C, D Kaplan–Meier analysis of the relationship between IL-6 gene expression and overall survival (OS) in cancer patients from The Cancer Genome Atlas (TCGA) (C) lung cancer (LUNG) or (D) Pan-Cancer datasets. E, F The concentration of IL-6 present in the culture supernatants of A549 or H1299 cells treated with the indicated concentrations of (E) sodium arsenite (SA) or (F) doxorubicin (Dox) for 24 h was determined by ELISA. G Western blot analysis of IL-6, phosphorylated STAT3 (Y705), and total STAT3 protein levels in A549 cells treated with increasing concentrations of SA for 24 h. H, J Dose-response curves showing the survival of control (scramble) and IL-6-silenced (shIL-6-1 and shIL-6-2) A549 cells in response to increasing concentrations of (H) SA or (J) Dox treatments for 24 h. I, K The IC₅₀ values of (I) SA or (K) Dox against scramble, shIL-6-1, and shIL-6-2 A549 cells were calculated from the nonlinear regression curves in Fig. 1H or J, respectively. Cell viability was measured by MTT assays. L Phosphorylated STAT3 (Y705), total STAT3, and γH2A.X protein levels in control (scramble) and IL-6-silenced (shIL-6) A549 cells untreated or treated with 20 µM SA for 24 h were determined by western blot analysis. M, N The mRNA levels of the anti-apoptotic genes (M) Bcl-xL and (N) Mcl-1 in scramble, shIL-6-1, and shIL-6-2 A549 cells untreated or treated with 20 µM SA for 24 h were measured by qRT-PCR. O, P The (O) migratory and (P) invasive abilities of scramble, shIL-6-1, and shIL-6-2 A549 cells untreated or treated with 20 µM SA or 0.1 µM Dox for 24 h were measured with transwell migration and invasion assays, respectively. Scale bar: 100 µm. Error bars represent mean ± SD, n = 3. Statistical analysis was performed using one-way ANOVA with Tukey’s multiple comparisons test (A), log-rank test (B–D), unpaired two-tailed Student’s t test (E, F, I, K), or two-way ANOVA with Tukey’s multiple comparisons test (M–P). *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001. The full length uncropped original western blots related to this figure are provided in the Supplemental Material file.