Glucosamine down-regulates the IGF-1R kinase-dependent Akt pathway in NSCLC cells. (A) Time- and dose-dependent effects of glucosamine in A549 cells. (B) A549 cells were pretreated with glucosamine for 1 day and then activated with IGF-1 for 15 minutes. (C) The effect of glucosamine on different NSCLC cell lines. (D) A549 cells transfected with siIGF-1R or scrambled non-targeting siRNA (siSCR) 2 days prior to a 1-day treatment with 1 mM glucosamine. (E) Cell proliferation assay in NSCLC cells transfected with siIGF-1R and treated with the indicated doses of glucosamine for 2 days. * P < 0.05 compared with siSCR-transfected cells.