IL-32 gamma reduces lung tumor development through upregulation of TIMP-3 overexpression and hypomethylation

Jaesuk Yun,Dong Ju Son,Jung Heun Ju,Jin Tae Hong,Kyung Tak Nam,Tae Hoon Kim,Do-Young Yoon,Dae Bong Moon,Jeong Soon Choi,Ok Kyung Hwang,Sang Bae Han,Mi Hee Park,Dae Yeon Hwang,Young Suk Jung

doi:10.1038/s41419-018-0375-6

Abstract

The low expression of tissue inhibitor of metalloproteinase 3 (TIMP-3) is important in inflammatory responses. Therefore, inhibition of TIMP-3 may promote tumor development. Our study showed that expression of TIMP-3 was elevated in lL-32γ mice lung tissues. In this study, we investigated whether IL-32γ mice inhibited lung tumor development through overexpression of TIMP-3 and its methylation. To explore the possible underlying mechanism, lung cancer cells were transfected with IL-32γ cDNA plasmid. A marked increase in TIMP-3 expression was caused by promoter methylation. Mechanistic studies indicated that TIMP-3 overexpression reduced NF-κB activity, which led to cell growth inhibition in IL-32γ transfected lung cancer cells. We also showed that IL-32γ inhibits expression of DNA (cytosine-5-)-methyltransferase 1 (DNMT1). Moreover, IL-32γ inhibits the binding of DNMT1 to TIMP-3 promoter, but this effect was reversed by the treatment of DNA methyltransferase inhibitor (5-Aza-CdR) and NF-κB inhibitor (PS1145), suggesting that a marked increase in TIMP-3 expression was caused by inhibition of promoter hypermethylation via decreased DNMT1 expression through the NF-κB pathway. In an in vivo carcinogen induced lung tumor model, tumor growth was inhibited in IL-32γ overexpressed mice with elevated TIMP-3 expression and hypomethylation accompanied with reduced NF-κB activity. Moreover, in the lung cancer patient tissue, the expression of IL-32 and TIMP-3 was dramatically decreased at a grade-dependent manner compared to normal lung tissue. In summary, IL-32γ may increase TIMP-3 expression via hypomethylation through inactivation of NF-κB activity, and thereby reduce lung tumor growth.

Highlights

Interleukin-32 (IL-32) was cloned as a gene induced by IL-18 and was formerly known as natural killer cell transcript 41
To determine whether apoptotic cell death contributed to the observed inhibitory effect of IL-32γ on lung tumor growth, we performed the TUNEL assay to detect apoptosis and Western blot to show the expression of apoptotic cell death regulatory proteins
We found that the expression of pro-apoptotic proteins, including Bax, cleaved caspase-3 and caspase-9, were increased but the IL-32γ inhibits cell growth and induces apoptosis in lung cancer cell lines

Summary

Introduction

Interleukin-32 (IL-32) was cloned as a gene induced by IL-18 and was formerly known as natural killer cell transcript 41. Since IL-32 modulates generation of pro and anti-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), IL-1β, IL-6, IL-10, and two C-X-C. Yun et al Cell Death and Disease (2018)9:306 chemokine family members involved in inflammatory and/or autoimmune diseases[3,4,5], there are different pathophysiological functions in the development of several diseases such as arthritis, psoriasis, ulcerative colitis, Crohn’s disease, chronic obstructive pulmonary disease and cancer that have been reported[3,6,7]. IL-32 inhibited tumor growth in a xenograft animal model and carcinogen-induced colon tumor development[8]. The role of IL-32 on the carcinogen-induced-lung tumor growth, and action mechanisms have not been reported yet. Many cytokines are involved in cancer development in different ways[9].

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