Effect of ionizing radiation on invasiveness of pulmonary adenocarcinoma cells A549 and its mechanism

Objective: To investigate the effect of ionizing radiation on the invasion of the pulmonary adenocarcinoma cell line A549. Methods: The invasiveness of A549 cells irradiated with 2 and 4 Gy doses of γ-rays was detected by using transwell invasion assay. The expression levels of matrix metalloproteinase (MMP)-2 mRNA and protein and phosphorylated signal transducers and activators of transcription 3 (STAT3) protein were detected by reverse transcription PCR and Western blot. Results: After irradiation with 2 or 4 Gy, the invasiveness of A549 cells increased by 200.0% (F=111.7, P<0.01) and 390.9% (F=593.7, P<0.01), respectively, compared with that in untreated A549 cells.Furthermore, the transcription and protein expression of MMP-2 24 h after irradiation and the phosphorylation of STAT3 12 h after irradiation were promoted. The irradiation-induced elevation of MMP-2 protein expression was suppressed using STAT3 phosphorylation specific inhibitor (AG490). Moreover, compared with 4 Gy of irradiation alone, treatment with 4 Gy of irradiation plus AG490 decreased the number of invasive cells by 76.1% (F=555.9, P<0.01), and the number of invasive cells in 4 Gy of irradiation plus AG490 group made up only 117.8% of that in untreated group (F=3.6, P>0.05). Conclusions: Ionizing radiation could activate STAT3, which triggers the transcription of MMP-2, and then promote the invasiveness of A549 cells. (authors)