Objective To explore the effect of dose rate of X-rays on migration of non-small cell lung cancer (NSCLC) cells and provide the experimental basis for developing radiotherapy scheme. Methods Human NSCLC cell line A549 was cultured and irradiated with X-rays at dose of 6 Gy from a linear accelerator. The dose rates of 1, 2, 4 and 6 Gy/min were selected. Monolayer adherent cells were scratched and photographed at 0 hour and 24 hours under a microscope to measure the scratch width. Results After 24 hours, the scratch width of nonirradiated control cells was (640.7±8.1)μm. The scratch widths of cells were different when cells were irradiated with X-rays of various dose rates. Scratch widths were the largest in cells irradiated at dose rates of 1 Gy/min [(691.4±7.6)μm] and 6 Gy/min [(691.8±12.1)μm]. The scratch width was (666.2±1.3) μm of X-rays at 4 Gy/min, and there were significant differences compared with nonirradiated group (all P< 0.01), which suggested that inhibitory effect of X-rays at dose rates on A549 cell migration was obvious. However, the scratch width of cells irradiated at 2 Gy/min [(643.5 ±6.8) μm] had no difference compared with the control cells (t=-0.336, P=0.742). Conclusions The effect of X-rays irradiation on cell migration of human NSCLC cell line A549 is related with irradiated dose rate. The effect of different dose rates on cell migration is significantly different. Selecting appropriate dose rates for irradiation may help to improve the efficacy of radiotherapy.

Objective To explore the effects of different dose rates of X-ray under the same dose on cell clonogenic formation in non-small-cell lung cancer cell line A549 in order to provide experimental basis for clinical radiotherapy plan. Methods The A549 cells were cultured at low density and irradiated with X-rays at dose of 4 Gy and selected dose rates of 1, 2, 4 and 6 Gy/min, respectively, from a linear accelerator. The 8th day after irradiation, the cells were fixed and stained with Giemsa solution, and colonies containing at least 50 cells were counted. The plating efficiency and surviving fraction were calculated. Results The clonogenic number in non-irradiated cells was 88.6±4.6. The numbers were significantly reduced in irradiated cells at dose rate 1, 2, 4 and 6 Gy/min (12.3±3.4, 9.0±0.8, 5.6±1.0, 11.5±1.7, respectively) than that in non-irradiated control cells (F=678.799, P<0.05). The plating efficiencies were decreased in irradiated cells, especially in 4 Gy/min irradiated cells, which was lower than that in any of the other three dose rate groups (P< 0.05). Conclusions Though at same radiation dose, cancer cells have different clonogenic formation efficiency when irradiation with X-ray at different dose rates. Thus, treatment with optimal dose rate may improve the radiotherapy efficacy.