High levels of IL-6 in MIA-MSLN cells plays important role in resistance to TNF-α-mediated cytotoxicity. (A). Elevated constitutive and TNF-α induced IL-6 expression in MIA-MSLN cells using Luminex-based IL-6 assay kit. Y-axis represents fluorescence corresponding to IL-6-levels. Bars denote SD of duplicate data. (B). Inhibiting endogenous IL-6 by siRNA sensitizes MIA-MSLN cells to TNF-α-induced apoptosis. MIA-MSLN cells were either mock-transfected (control) or transfected with non-targeting (siNT) or IL-6 specific siRNA pools (siIL-6) and treated with 20 ng/ml of TNF-α for 72 h and analyzed for TUNEL positivity. Flow histograms show percentage of dUTP-FITC-positive apoptotic cells. Plots are representatives of three independent experiments.