JunD accentuates arecoline-induced disruption of tight junctions and promotes epithelial-to-mesenchymal transition by association with NEAT1 lncRNA.

Subarna Ghosh,Sarbani Giri,Urmi Chatterji,Abhinandan Bhattacharjee,Nitai Pada Bhattacharyya,Priyanka Dey Talukdar

doi:10.18632/oncotarget.28026

Abstract

Head and neck cancers are highly prevalent in south-east Asia, primarily due to betel nut chewing. Arecoline, the primary alkaloid is highly carcinogenic; however its role in promoting tumorigenesis by disrupting junctional complexes and increasing risk of metastasis is not well delineated. Subsequently, the effects of low and high concentrations of arecoline on the stability of tight junctions and EMT induction were studied. A microarray analysis confirmed involvement of a MAPK component, JunD, in regulating tight junction-associated genes, specifically ZO-1. Results established that although arecoline-induced phosphorylation of JunD downregulated expression of ZO-1, JunD itself was modulated by the lncRNA-NEAT1 in presence of arecoline. Increased NEAT1 in tissues of HNSCC patients significantly correlated with poor disease prognosis. Here we show that NEAT1-JunD complex interacted with ZO-1 promoter in the nuclear compartment, downregulated expression of ZO-1 and destabilized tight junction assembly. Consequently, silencing NEAT1 in arecoline-exposed cells not only downregulated the expression of JunD and stabilized expression of ZO-1, but also reduced expression of the EMT markers, Slug and Snail, indicating its direct regulatory role in arecoline-mediated TJ disruption and disease progression.

Highlights

In the past few years, there has been a drastic rise in the incidence of head and neck cancers worldwide [1]
International Agency for Research on Cancer (IARC) has declared the psychoactive areca nut to be carcinogenic to humans and chewing betel nut increases the risk of oropharyngeal cancer, independent of use of tobacco and alcohol [6]
This fact was further ratified in our experiments where we confirmed that a switch between the proliferative and apoptotic effects of arecoline lay somewhere between 90 and 110 μM when exposed for 24 hours, which included the concentration of arecoline in the saliva of betel nut chewers (23.7 to 415.2 μM), thereby defining both intermittent and regular usage as a risk for carcinogenic insult [8]

Summary

Introduction

In the past few years, there has been a drastic rise in the incidence of head and neck cancers worldwide [1]. Head and neck squamous cell carcinomas (HNSCCs) are highly prevalent in countries of south-east Asia, comprising 35–40% of all malignancies in India [2]. Cancer arising in the larynx is the most prevalent form of HNSCC (25–30%) and confers a negative effect on the quality of life [3, 4]. Highly rife in Asian countries, is one of the potential causes of HNSCC [5]. International Agency for Research on Cancer (IARC) has declared the psychoactive areca nut to be carcinogenic to humans and chewing betel nut increases the risk of oropharyngeal cancer, independent of use of tobacco and alcohol [6]. Salivary arecoline level in humans during betel nut chewing ranges from 5.66 to 97.39 μg/ml [8]. EMT, which is characterized by a loss of cell-to-cell contact, leads to repression of tight junction (TJ)-related proteins and eventually disruption of the TJs [11]

Methods

Results

Discussion

Conclusion