Autophagy inhibition enhances radiosensitivity of esophageal squamous carcinoma Eca-109 cells

Abstract

Objective To investigate the role of autophagy in radiation-induced death process of human esophageal squamous carcinoma Eca-109 cells. Methods Esophageal carcinoma cell line Eca-109 was divided into 6 groups of control, 5 mmol/L 3-Methyladenine treatment, 10 mmol/L treatment, 6 Gy irradiation, irradiation + 5 mmol/L drug, and irradiation + 10 mmol/L drug. Some cells were transferred with GFP-LC3 plasmid and the changes of autophagosome were obserred. After each treatment, the expression of autophagy marker LC3B was measured by Western Blot, cell viability was detected by MTT, morphological characteristics of apoptosis cells were stained with a fluorescein of Hoechst 33342 and the percentage of apoptotic cells and cell cycle distribution were measured by flow cytometry. Clonogenic survival were used to evaluate the cell radiosensitivity. Results Autophagy level was increased after radiation, and the LC3BⅡ expression and LC3BⅡ/LC3BⅠ ratio were significantly decreased by autophagy inhibitor 3-Methyladenine (F=25.64, P<0.05). The number of autophagosome fluorescent foci were significantly increased in the GFP-LC3 transfected cells after radiation, but reduced by 3-Methyladenine (F=127.36, P<0.05). Compared with radiation alone group, autophagy inhibition combined with radiation significantly decreased cell viability (F=129.54, P<0.05) and colony formation, increased apoptosis and the percentage of G2/M-phase cells. Conclusions 3-Methyladenine enhances the radiosensitivity of esophageal squamous carcinoma Eca-109 cells, suggesting that inhibition of autophagy could be used as an adjuvant treatment of radiotherapy in esophageal squamous carcinoma. Key words: Autophagy; Esophageal squamous carcinoma Eca-109 cells; Radiosensitivity