Combined inhibition of insulin-like growth factor-1 receptor enhances the effects of gefitinib in a human non-small cell lung cancer resistant cell line.

The type I insulin-like growth factor receptor (IGF-1R) signaling pathway is an important growth-regulatory pathway that is prevalent in a variety of cancer types, including human non-small cell lung cancer (NSCLC). To observe the combined effects of gefitinib and AG1024-induced IGF-1R inhibition on the growth of NSCLC, PC9/G cells, a NSCLC cell line with acquired resistance to gefitinib, were treated with AG1024 and gefitinib, alone or in combination. The proliferative activity of PC9/G cells upon different treatments was assessed by CCK-8, and the median-effects principle was used to assess the effect of the combined treatment. Apoptotic rates of the PC9/G cells for the different treatment groups were analyzed by flow cytometry. The expression of phosphorylated epidermal growth factor receptor (p-EGFR), phosphorylated-Akt (p-Akt), and phosphorylated extracellular signal-regulated kinase (p-ERK) in PC9/G cells was examined by Western blotting. PC9/G cells exhibited apoptotic features after treatment with AG1024 and gefitinib alone, and their proliferation rates were inhibited to different degrees. The treatment of AG1024 combined with gefitinib resulted in a synergistic effect in inducing apoptosis, inhibiting cell proliferation and decreasing the expression of p-EGFR, p-Akt and p-ERK. In conclusion, combined inhibition of IGF-1R signaling enhances the anti-proliferative and pro-apoptotic effects of gefitinib in NSCLC gefinitib-resistant cells. Moreover, the addition of an anti-IGF-1R strategy to gefitinib treatment may be more effective than a single-agent approach.