A reciprocal feedback of Myc and lncRNA MTSS1-AS contributes to extracellular acidity-promoted metastasis of pancreatic cancer
A reciprocal feedback of Myc and lncRNA MTSS1-AS contributes to extracellular acidity-promoted metastasis of pancreatic cancer
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Myc 和 lncRNA MTSS1-AS 的相互反馈有助于细胞外酸性促进胰腺癌转移
DOI：
10.7150/thno.49147
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发表时间：
2020-01-01
期刊：
影响因子：
12.4
通讯作者：
Zhao, Gang
中科院分区：
文献类型：
--
作者：
Hu, Yuhang;Wang, Fan;Zhao, Gang
理论基础：以前的研究已经报道了细胞外酸度在许多癌症转移中的作用。然而，长非编码RNA(LncRNA)在酸性诱导的胰腺癌(PC)细胞外转移中的作用尚不清楚。方法：采用RNA测序(RNA-seq)技术比较正常和酸性条件下胰腺癌细胞中LncRNA的表达水平。通过功能得失实验评价肿瘤转移抑制因子1反义寡核苷酸(MTSS1-AS)对酸性PC细胞的作用。采用荧光原位杂交、RNA免疫沉淀、RNA下拉、Western印迹、荧光素酶报告和染色质免疫沉淀等方法研究MTSS1-AS在酸性诱导的PC细胞转移中的调控机制。比较MTSS1-AS在胰腺癌组织和瘤周正常组织中的表达及相关途径。结果：RNA-seq显示酸性介质培养的胰腺细胞MTSS1-AS表达明显下调。MTSS1-AS的过表达通过上调其正义基因转移抑制因子1(MTSS1)的表达，显著抑制了酸性诱导的PC细胞的转移。在机制上，MTSS1-AS支架了E3泛素蛋白连接酶STIP1同源物与U盒含蛋白1(STUB1)和转录调节因子髓样锌指1(MZF1)之间的相互作用，导致泛素化介导的MZF1降解。此外，MZF1通过与MTSS1启动子结合来抑制MTSS1的表达。因此，酸性降低的MTSS1-AS有利于MZF1的稳定性及其对MTSS1转录的抑制作用，从而促进了PC细胞在酸性条件下的转移。此外，MYC原癌基因(Myc)与MTSS1-AS启动子的启动子(INR)元件的结合在转录水平上抑制了MTSS1-AS。同时，MTSS1-AS通过抑制MZF1介导的Myc转录激活相互抑制Myc的表达，从而在酸性PC细胞中形成MTSS1-AS与Myc之间的负反馈环。结论：Myc和MTSS1-AS之间的相互反馈环参与了细胞外酸性促进PC的转移，提示MTSS1-AS是PC有价值的生物标志物和治疗靶点。
Rationale: Previous studies have reported on the role of extracellular acidity in the metastasis of numerous cancers. However, the involvement of long noncoding RNA (lncRNA) in the extracellular acidity-induced cancer metastasis of pancreatic cancer (PC) remains unclear.Methods: Different expression levels of lncRNAs in PC cells under normal and acidic conditions were compared by RNA sequencing (RNA-seq). The effects of antisense lncRNA of metastasis suppressor 1 (MTSS1-AS) on acidic PC cells were assessed by gain- and loss-of-function experiments. Fluorescence in situ hybridization, RNA immunoprecipitation, RNA pull-down, Western blot, luciferase reporter, and Chromatin immunoprecipitation assays were employed to determine the regulatory mechanisms of MTSS1-AS in the acidity-induced metastasis of PC cells. The expression of MTSS1-AS and associated pathways were compared in PC samples and peritumoral normal tissues.Results: RNA-seq demonstrated that MTSS1-AS was significantly downregulated in pancreatic cells cultured with the acidic medium. The overexpression of MTSS1-AS remarkably inhibited the acidity-promoted metastasis of PC cells by upregulating the expression of its sense gene metastasis suppressor 1 (MTSS1). Mechanistically, MTSS1-AS scaffolded the interaction between E3 ubiquitin-protein ligase STIP1 homology and U-box containing protein 1 (STUB1) and transcription regulator myeloid zinc finger 1 (MZF1), leading to ubiquitination-mediated degradation of MZF1. Further, MZF1 inhibited the expression of MTSS1 by binding to the MTSS1 promoter. Thus, the acidity-reduced MTSS1-AS facilitated the stability of MZF1 and its inhibitory effect on MTSS1 transcription, thereby promoting the metastasis of PC cells under acidic conditions. Moreover, MTSS1-AS was transcriptionally repressed by the binding of MYC proto-oncogene (Myc) with initiator (Inr) elements of the MTSS1-AS promoter. Meanwhile, MTSS1-AS mutually repressed the expression of Myc by impairing the MZF1-mediated transcription activation of Myc, thereby forming a negative feedback loop between MTSS1-AS and Myc in acidic PC cells. In accordance with the experimental results, MTSS1-AS and MTSS1 were downregulated in PC and correlated with poor overall survival.Conclusions: The results implicated that a reciprocal feedback loop between Myc and MTSS1-AS contributed to the extracellular acidity-promoted metastasis of PC, and indicated that MTSS1-AS was a valuable biomarker and therapeutic target for PC.