['To determine the effects of endostatin on vascular growth factor receptor 2 (VEGFR2) expression in non-small cell lung cancer (NSCLC) cells and the mechanisms underlying its radiosensitizing effect.', 'VEGFR2 mRNA levels were determined in different NSCLC cell lines using qRT-PCR. RT-PCR and Western blot assays were used to assess the expression of mRNA and proteins. The radiosensitivity of the cells was determined by colony-formation assays; and cell apoptosis and cell cycle distribution were determined by flow cytometry.', 'VEGFR2 mRNA levels differed among the five NSCLC cell lines (P < 0.01), with the highest expression in Calu-1 cells and lowest in A549 cells. Endostatin significantly inhibited the growth of Calu-1 cells (P < 0.01) (IC20 = 296.5 μg/ml), and the expression of VEGFR2 and HIF-1α (P < 0.05). Phosphorylation of protein kinase B (Akt), extracellular signal-regulated kinases 1/2 (ERK1/2), and p38 were significantly lower in endostatin-treated cells than control (P < 0.05). Endostatin enhanced the radiosensitivity of Calu-1 cells to SER = 1.38 and induced apoptosis (P < 0.01) and G2/M blockage (P < 0.01). However, endostatin had limited effects on A549 cells. Compared with Calu-1 cells, there was not significantly effects on cell radiosensitivity (SER = 1.09).'] Does endostatin exert radiosensitizing effect in non-small cell lung cancer cells by inhibiting VEGFR2 expression?