Jiang Zhen-Huan, Peng Jun, Yang Hui-Lin, Fu Xing-Li, Wang Jin-Zhi, Liu Lei, Jiang Jian-Nong, Tan Yong-Fei, Ge Zhi-Jun
Department of Orthopedics, The Affiliated Yixing Hospital of Jiangsu University, Yixing, People's Republic of China.
Department of Orthopedics, The First Affiliated Hospital of Soochow University, Suzhou, People's Republic of China.
Exp Mol Med. 2017 May 12;49(5):e329. doi: 10.1038/emm.2017.41.
Osteosarcoma is suggested to be caused by genetic and molecular alterations that disrupt osteoblast differentiation. Recent studies have reported that transmembrane protein 119 (TMEM119) contributes to osteoblast differentiation and bone development. However, the level of TMEM119 expression and its roles in osteosarcoma have not yet been elucidated. In the present study, TMEM119 mRNA and protein expression was found to be up-regulated in osteosarcoma compared with normal bone cyst tissues. The level of TMEM119 protein expression was strongly associated with tumor size, clinical stage, distant metastasis and overall survival time. Moreover, gene set enrichment analysis (GSEA) of the Gene Expression Omnibus (GEO) GSE42352 dataset revealed TMEM119 expression in osteosarcoma tissues to be positively correlated with cell cycle, apoptosis, metastasis and TGF-β signaling. We then knocked down TMEM119 expression in U2OS and MG63 cells using small interfering RNA, which revealed that downregulation of TMEM119 could inhibit the proliferation of osteosarcoma cells by inducing cell cycle arrest in G0/G1 phase and apoptosis. We also found that TMEM119 knockdown significantly inhibited cell migration and invasion, and decreased the expression of TGF-β pathway-related factors (BMP2, BMP7 and TGF-β). TGF-β application rescued the inhibitory effects of TMEM119 knockdown on osteosarcoma cell migration and invasion. Further in vitro experiments with a TGF-β inhibitor (SB431542) or BMP inhibitor (dorsomorphin) suggested that TMEM119 significantly promotes cell migration and invasion, partly through TGF-β/BMP signaling. In conclusion, our data support the notion that TMEM119 contributes to the proliferation, migration and invasion of osteosarcoma cells, and functions as an oncogene in osteosarcoma.
骨肉瘤被认为是由破坏成骨细胞分化的基因和分子改变引起的。最近的研究报道，跨膜蛋白119（TMEM119）有助于成骨细胞分化和骨骼发育。然而，TMEM119的表达水平及其在骨肉瘤中的作用尚未阐明。在本研究中，与正常骨囊肿组织相比，发现骨肉瘤中TMEM119 mRNA和蛋白表达上调。TMEM119蛋白表达水平与肿瘤大小、临床分期、远处转移和总生存时间密切相关。此外，对基因表达综合数据库（GEO）GSE42352数据集进行基因集富集分析（GSEA）发现，骨肉瘤组织中TMEM119表达与细胞周期、凋亡、转移和TGF-β信号通路呈正相关。然后，我们使用小干扰RNA敲低U2OS和MG63细胞中TMEM119的表达，结果显示TMEM119的下调可通过诱导细胞周期停滞在G0/G1期和凋亡来抑制骨肉瘤细胞的增殖。我们还发现，敲低TMEM119可显著抑制细胞迁移和侵袭，并降低TGF-β通路相关因子（BMP2、BMP7和TGF-β）的表达。应用TGF-β可挽救敲低TMEM119对骨肉瘤细胞迁移和侵袭的抑制作用。使用TGF-β抑制剂（SB431542）或BMP抑制剂（多穗柯碱）进行的进一步体外实验表明，TMEM119可部分通过TGF-β/BMP信号通路显著促进细胞迁移和侵袭。总之，我们的数据支持这样一种观点，即TMEM119促进骨肉瘤细胞的增殖、迁移和侵袭，并在骨肉瘤中作为一种癌基因发挥作用。
