GSK-3\u03b2 inhibits autophagy and enhances radiosensitivity in non-small cell lung cancer

Jialin Ren,Yanzhi Chen,Tingting Liu,Qiongzi Wang,Lihong Jiang,Yang Han,Guang Li

doi:10.1186/s13000-018-0708-x

Abstract

BackgroundRadiotherapy is one of the most common and effective treatment methods for cancer, and improving the radiosensitivity of tumor tissues during the treatment process is vital. We report the mechanisms of glycogen synthase kinase 3 (GSK-3) β-regulated autophagy and the effects of autophagy on radiosensitivity in non-small cell lung cancer (NSCLC).MethodImmunohistochemical staining was performed to determine GSK-3β tissue expression in 89 NSCLC patients with follow-up data and the expression status of GSK-3β and autophagy in NSCLC tissues after X-ray radiotherapy. Western blots were used to quantitate changes in autophagy-related protein expression after A549 cells were treated with GSK-3β inhibitors and after H460 cells were transfected with GSK-3β mutants with different activities and X-ray irradiated. Clonogenic assays were used to measure the effect of autophagy on cellular proliferation.ResultsGSK-3β expression positively correlated with NSCLC differentiation (P < 0.05), and GSK-3β negativity was associated with a better prognosis in 89 NSCLC patients. After X-ray irradiation, the expression levels of GSK-3β and p62 were decreased in NSCLC tissues, and the expression levels of the autophagy-related protein LC3 were increased. A549 and H460 cells were selected as representative GSK-3β-high and GSK-3β-low expression cell lines. After transfecting H460 cells with different GSK-3β mutants [wild type GSK-3β (GSK-3β-WT), constitutively active GSK-3β (GSK-3β-S9A), and catalytically inactive GSK-3β (GSK-3β-K85R)] and subjecting these cells to X-ray irradiation, AMPK and LC3 expression levels decreased, and p62 expression levels increased. These effects were particularly significant for the GSK-3β-S9A mutant. In A549 cells, after GSK-3β inhibition and X-ray irradiation, AMPK and LC3 protein expression levels increased. Moreover, when autophagy was inhibited, cell proliferation decreased.ConclusionOur studies revealed that GSK-3β expression is associated with NSCLC differentiation, and patients with GSK-3β-negative tumors had a better prognosis. X-ray irradiation inhibited GSK-3β expression and promoted autophagy. Therefore, GSK-3β inhibits autophagy and enhances the radiosensitivity of NSCLC cells.

Highlights

Radiotherapy is one of the most common and effective treatment methods for cancer, and improving the radiosensitivity of tumor tissues during the treatment process is vital
GSK-3β expression positively correlated with nonsmall cell lung cancer (NSCLC) differentiation (P < 0.05), and GSK-3β negativity was associated with a better prognosis in 89 NSCLC patients
After X-ray irradiation, the expression levels of GSK-3β and p62 were decreased in NSCLC tissues, and the expression levels of the autophagy-related protein LC3 were increased

Summary

Introduction

Radiotherapy is one of the most common and effective treatment methods for cancer, and improving the radiosensitivity of tumor tissues during the treatment process is vital. We report the mechanisms of glycogen synthase kinase 3 (GSK-3) β-regulated autophagy and the effects of autophagy on radiosensitivity in nonsmall cell lung cancer (NSCLC). Glycogen synthase kinase 3 (GSK-3) β is a serine/threonine protein kinase, and its activity is regulated by the phosphorylation of specific sites. Some studies have indicated that GSK-3β can regulate autophagy; others suggest that the regulatory effects of GSK-3β are not the same in different cancers [2,3,4,5,6,7]. Recent studies have shown that the autophagy status of cells affects the radiosensitivity of tumors [9]. These responses vary in different types of cells

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