MiRNA-21 functions in ionizing radiation-induced epithelium-to-mesenchymal transition (EMT) by downregulating PTEN

• Published in: Toxicology research (Cambridge) Vol. 8; no. 3; pp. 328 - 34
• Main Authors: Liu, Zheng, Liang, Xin, Li, Xueping, Liu, Xiaodan, Zhu, Maoxiang, Gu, Yongqing, Zhou, Pingkun
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.05.2019
• Subjects: AKT protein; Attenuation; Epithelial cells; Epithelium; Fibrosis; Inhibitors; Ionizing radiation; Irradiation; Lung diseases; Lungs; Mesenchyme; miRNA; Phosphorylation; Post-irradiation; PTEN protein; Pulmonary fibrosis; Radiation dosage; Radiation effects; Radiation therapy; Thorax; Transfection
• ISSN: 2045-452X; 2045-4538
• DOI: 10.1039/c9tx00019d

Radiation-induced pulmonary fibrosis (RIPF) results from thoracic radiotherapy and severely limits the use of radiotherapy. Recent studies suggest that epithelium-to-mesenchymal transition (EMT) contributes to pulmonary fibrosis. Although miRNA dysregulation participates in a variety of pathophysiologic processes, their roles in fibrotic lung diseases and EMT are unclear. In this study, we aimed to identify key miRNAs involved in this process using a mouse model of RIPF previously established by irradiation with a single dose (20 Gy) of 60 Co γ-rays. At 2-weeks post-irradiation, a set of significantly upregulated miRNAs was identified in lung tissue by miRNA array analysis. This included miR-21, which has been reported to contribute to the pulmonary fibrotic response induced by stereotactic body radiotherapy. Here, we showed that miR-21 expression increased in parallel with EMT progression in the lungs of irradiated mice. Ectopic miR-21 expression promoted EMT progression in lung epithelial cells. Furthermore, downregulation of miR-21 expression by transfection of its inhibitor inhibited ionizing radiation (IR)-induced EMT. Knockdown of PTEN, which is the functional target of miR-21, reversed the attenuation of IR-induced EMT mediated by miR-21 downregulation. Radiation treatment decreased PTEN expression and increased Akt phosphorylation; these effects were abolished by the miR-21 inhibitor. MiR-21 overexpression in lung epithelial cell also downregulated PTEN expression and upregulated Akt phosphorylation. In conclusion, we have demonstrated that miR-21 functions as a key regulator of IR-induced EMT in lung epithelial cells via the PTEN/Akt pathway. Targeting miR-21 is implicated as a novel therapeutic strategy for the prevention of RIPF. MiR-21 functions as a key regulator of IR-induced fibrotic EMT in lung epithelial cells via the miR-21/PTEN/Akt axis.