Fig. 4

Exogenous expression of NRG1 leads to cetuximab resistance. A HN30 and PCI37A cells were plated and treated with 100 nM of cetuximab (Ctx), 100 ng/mL of NRG1, or the combination of Ctx and NRG1 for 72 h. Cell proliferation was determined by CCK8 assay. Mean values, SEs, and statistical analyses are representative of two independent experiments. N = 6, **P < 0.01. Whole cell lysates were harvested at 24 h after treatment and fractionated via SDS-PAGE, followed by immunoblotting for the indicated proteins. GAPDH was used as a loading control. B HN30 and PCI37A cells were transfected with 30 nM siHER3 or 30 nM siNT for 24 h before treatment with Ctx (100 nM) or NRG1 (100 ng/ml) for an additional 72 h. Cell viability or cell proliferation was determined by crystal violet assay for HN30 cells and CCK8 assay for PCI37A cells. Mean values, SEs, and statistical analyses are representative of two or three independent experiments. N = 3–10, **P < 0.01. Whole cell lysate was harvested at 24 h after treatment and subjected to immunoblot analysis following fractionation via SDS-PAGE. GAPDH was used as a loading control