College of Pharmacy and Medical Research Center, Chungbuk National University, Osongsaengmyeong1-ro 194-21, Heungduk-gu, Cheongju, Chungbuk, 28160, Republic of Korea.
Department of Pharmacy, Wonkwang University, #460 Iksan-daero, Iksan-si, Jeonbuk, 54538, Republic of Korea.
Cell Death Dis. 2018 Feb 21;9(3):306. doi: 10.1038/s41419-018-0375-6.
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.
组织金属蛋白酶抑制剂 3（TIMP-3）的低表达在炎症反应中很重要。因此，抑制 TIMP-3 可能会促进肿瘤的发展。我们的研究表明，IL-32γ 小鼠肺组织中 TIMP-3 的表达升高。在这项研究中，我们研究了通过过表达 TIMP-3 及其甲基化是否可以抑制 IL-32γ 小鼠的肺肿瘤发生。为了探讨可能的潜在机制，用 IL-32γ cDNA 质粒转染肺癌细胞。启动子甲基化导致 TIMP-3 表达显著增加。机制研究表明，TIMP-3 过表达降低了 NF-κB 活性，从而导致 IL-32γ 转染的肺癌细胞生长受到抑制。我们还表明，IL-32γ 抑制 DNA（胞嘧啶-5-）-甲基转移酶 1（DNMT1）的表达。此外，IL-32γ 抑制 DNMT1 与 TIMP-3 启动子的结合，但该作用可被 DNA 甲基转移酶抑制剂（5-Aza-CdR）和 NF-κB 抑制剂（PS1145）逆转，表明通过降低 DNMT1 表达抑制启动子超甲基化导致 TIMP-3 表达显著增加，通过 NF-κB 通路。在致癌剂诱导的肺肿瘤模型中，过表达 IL-32γ 的小鼠肿瘤生长受到抑制，TIMP-3 表达升高，低甲基化伴有 NF-κB 活性降低。此外，与正常肺组织相比，肺癌患者组织中 IL-32 和 TIMP-3 的表达呈显著降低的梯度依赖性。总之，IL-32γ 可能通过 NF-κB 活性失活通过低甲基化增加 TIMP-3 表达，从而减少肺肿瘤生长。
