TUSC3 induces autophagy in human non-small cell lung cancer cells through Wnt/β-catenin signaling.

Yun Peng,Xiao-Yi Yao,Jian-Huang Li,Jun Cao,Mei-Zuo Zhong,Jian-Xin Wang,Ping-Ping Gan,Jian Huang Li

doi:10.18632/oncotarget.17674

Abstract

We investigated the effects of tumor suppressor candidate 3 (TUSC3) on autophagy in human non-small cell lung cancer (NSCLC) cells. A total of 118 NSCLC patients (88 males and 30 females) who underwent surgery at our institute were enrolled in the study. Immunohistochemical analysis revealed that TUSC3 protein expression was lower in NSCLC specimens than adjacent normal tissue. Correspondingly, there was greater methylation of TUSC3 in NSCLC than adjacent normal tissue. After transient transfection of A549 NSCLC cells with constructs designed to up-regulate or down-regulate TUSC3 expression, we analyzed the effects of inhibiting the Wnt pathway (XAV939) and autophagy (chloroquine, CQ) on the behavior of NSCLC cells. We also performed TOP/FOP-Flash reporter assays, MTT assays, Annexin V-FITC/propidium iodide staining, and acridine orange staining to evaluate Wnt/β-catenin signaling, cell proliferation, apoptosis, and autophagy, respectively. Expression of Wnt/β-catenin pathway components and autophagy-related proteins was analyzed using qRT-PCR and Western blotting. We found that TUSC3 inhibited cell proliferation and promoted both apoptosis and autophagy in A549 cells. In addition, TUSC3 increased expression of autophagy-related proteins. It also increased expression of Wnt/β-catenin signaling pathway components and promoted nuclear transfer of β-catenin, resulting in activation of Wnt/β-catenin signaling. TUSC3 thus induces autophagy in human NSCLC cells through activation of the Wnt/β-catenin signaling pathway.

Highlights

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in men worldwide [1]
tumor suppressor candidate 3 (TUSC3) protein expression is reduced in non-small cell lung cancer (NSCLC) compared to adjacent normal tissue
Our data indicate that TUSC3 promotes autophagy in NSCLC cells though activation of the Wnt/β-catenin signaling pathway

Summary

Introduction

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in men worldwide [1]. It is estimated that up to 70% of NSCLC patients are diagnosed with advanced-stage disease [2]. Cytotoxic chemotherapy is beneficial for patients with advanced NSCLC, the response rate is only 20%−35% and the median survival is 10−12 months [3]. Differences in the clinical presentation of NSCLC patients can be attributed to the diverse molecular mechanisms that drive malignant transformation and dissemination of the primary tumor. Inhibition of autophagy is an attractive therapeutic strategy because it can weaken the ability of tumor cells to clear protein aggregates or damaged organelles [5]. A better understanding of the mechanisms of cell death could lead to the development of more effective therapeutics for NSCLC

Methods

Results

Conclusion