N-Methylparoxetine Blocked Autophagic Flux and Induced Apoptosis by Activating ROS-MAPK Pathway in Non-Small Cell Lung Cancer Cells.

Kun Wang,Hiuting Idy Ho,Yuhui Tan,Wenli Mao,Jiawei Chen,Yuhua Lu,Yujuan Zhan,Shikun Zhou,Xiaodong Liu,Yilin Zhang,Bonan Chen,Ting Yin,Weijie Wu,Jianyong Xiao,Biaoyan Du

doi:10.3390/ijms20143415

Abstract

The main mechanistic function of most chemotherapeutic drugs is mediated by inducing mitochondria-dependent apoptosis. Tumor cells usually respond to upregulate autophagy to eliminate impaired mitochondria for survival. Hypothetically, inhibiting autophagy might promote mitochondria-dependent apoptosis, thus enhancing the efficacy of chemotherapeutic therapies. We previously identified N-methylparoxetine (NMP) as an inducer of mitochondrial fragmentation with subsequent apoptosis in non-small cell lung cancer (NSCLC) cells. We discovered that ROS was accumulated in NMP-treated NSCLC cells, followed by c-Jun N-terminal kinase (JNK) and p38 MAP kinase (p38) activation. This was reversed by the application of a reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC), leading to a reduction in apoptosis. Our data suggested that NMP induced apoptosis in NSCLC cells by activating mitogen-activated protein kinase (MAPK) pathway. We further speculated that the remarkable increase of ROS in NMP-treated NSCLC cells might result from an inhibition of autophagy. Our current data confirmed that NMP blocked autophagy flux at late stage wherein lysosomal acidification was inhibited. Taken together, this study demonstrated that NMP could exert dual apoptotic functions—mitochondria impairment and, concomitantly, autophagy inhibition. NMP-related excessive ROS accumulation induced apoptosis by activating the MAPK pathway in NSCLC cells.

Highlights

Lung cancer is the leading cause of cancer death globally, representing 18% of all cancer deaths [1]
Our colony formation assay showed that the numbers of colonies of NMP-pretreated Non-small cell lung cancer (NSCLC) cells decreased in a dose-dependent manner
To determine the effect of NMP on cell division, NSCLC cells were labeled with CFDA-SE which can be distributed to daughter cells, leading to a decreased fluorescence intensity in proliferating cells

Summary

Introduction

Lung cancer is the leading cause of cancer death globally, representing 18% of all cancer deaths [1]. Adjuvant chemotherapy after surgical resection is the prioritized strategy against NSCLC to prolong survival. As mitochondria play a pivotal role on triggering apoptosis [4], currently many clinically-used anti-tumor drugs, including the first-line therapies such as cisplatin and paclitaxel, exert a killing effect on cancer cells at least in part by mitochondrial apoptotic priming, or direct impairment of mitochondrial respiratory chain complexes. With this strategy, high doses of chemotherapy are normally required for an effective anti-tumor effect. Treatment with high dosages of non-targeted drugs is a double-edged sword that the cytotoxicity affects tumor and healthy cells simultaneously

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