National Institute of Molecular Biology and Biotechnology, University of the Philippines, Diliman, Quezon City 1101, Philippines.
Oncol Rep. 2019 Apr;41(4):2103-2116. doi: 10.3892/or.2019.7020. Epub 2019 Feb 19.
Inactivation of the tumor suppressor protein Merlin leads to the development of benign nervous system tumors in neurofibromatosis type2 (NF2). Documented causes of Merlin inactivation include deleterious mutations in the encoding neurofibromin2 gene (NF2) and aberrant Merlin phosphorylation leading to proteasomal degradation. Rare somatic NF2 mutations have also been detected in common human malignancies not associated with NF2, including colorectal and lung cancer. Furthermore, tumors without NF2 mutations and with unaltered NF2 transcript levels, but with low Merlin expression, have been reported. The present study demonstrated that NF2 is also regulated by microRNAs (miRNAs) through direct interaction with evolutionarily conserved miRNA response elements (MREs) within its 3'‑untranslated region (3'UTR). Dual‑Luciferase assays in human colorectal carcinoma (HCT116) and lung adenocarcinoma (A549) cells revealed downregulation of NF2 by miR‑92a‑3p via its wild‑type 3'UTR, but not NF2‑3'UTR with mutated miR‑92a‑3p MRE. HCT116 cells overexpressing miR‑92a‑3p exhibited significant downregulation of endogenous NF2 mRNA and protein levels, which was rescued by co‑transfection of a target protector oligonucleotide specific for the miR‑92a‑3p binding site within NF2‑3'UTR. miR‑92a‑3p overexpression in HCT116 and A549 cells promoted migration, proliferation and resistance to apoptosis, as well as altered F‑actin organization compared with controls. Knockdown of NF2 by siRNA phenocopied the oncogenic effects of miR‑92a overexpression on HCT116 and A549 cells. Collectively, the findings of the present study provide functional proof of the unappreciated role of miRNAs in NF2 regulation and tumor progression, leading to enhanced oncogenicity.
肿瘤抑制蛋白 Merlin 的失活导致神经纤维瘤病 2 型 (NF2) 中良性神经系统肿瘤的发展。 Merlin 失活的已知原因包括编码神经纤维瘤蛋白 2 基因 (NF2) 的有害突变和导致蛋白酶体降解的异常 Merlin 磷酸化。在与 NF2 无关的常见人类恶性肿瘤中也检测到罕见的体细胞 NF2 突变,包括结直肠癌和肺癌。此外,还报道了没有 NF2 突变且 NF2 转录本水平不变但 Merlin 表达降低的肿瘤。本研究表明,NF2 还通过其 3' 非翻译区 (3'UTR) 内与进化上保守的 microRNA (miRNA) 反应元件 (MRE) 的直接相互作用受到 miRNAs 的调节。在人结直肠癌细胞 (HCT116) 和肺腺癌细胞 (A549) 中的双荧光素酶测定显示,miR-92a-3p 通过其野生型 3'UTR 下调 NF2,但突变的 miR-92a-3p MRE 的 NF2-3'UTR 则不然。过表达 miR-92a-3p 的 HCT116 细胞表现出内源性 NF2 mRNA 和蛋白水平的显著下调,这可通过共转染针对 NF2-3'UTR 中 miR-92a-3p 结合位点的靶保护寡核苷酸得到挽救。与对照相比,HCT116 和 A549 细胞中 miR-92a-3p 的过表达促进了迁移、增殖和抗凋亡,并改变了 F-肌动蛋白的组织。NF2 的 siRNA 敲低模仿了 miR-92a 过表达对 HCT116 和 A549 细胞的致癌作用。总之,本研究的结果提供了 miRNA 在 NF2 调节和肿瘤进展中未被认识的作用的功能证据,导致了增强的致癌性。