MiRNA-646-mediated reciprocal repression between HIF-1α and MIIP contributes to tumorigenesis of pancreatic cancer
MiRNA-646-mediated reciprocal repression between HIF-1α and MIIP contributes to tumorigenesis of pancreatic cancer
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miRNA-646介导的HIF-1α和MIIP之间的相互抑制有助于胰腺癌的肿瘤发生
DOI：
10.1038/s41388-017-0082-2
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发表时间：
2018-03-01
期刊：
影响因子：
8
通讯作者：
Zhao, Gang
中科院分区：
文献类型：
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作者：
Niu, Yi;Jin, Yan;Zhao, Gang
迁移和侵袭抑制蛋白(MIIP)是近年来发现的一种肿瘤生长抑制因子。然而，MIIP在胰腺癌(PC)中的调控机制和生物学作用尚不清楚。在这项研究中，我们证明了MIIP和低氧诱导因子-1α(HIF-1α)的负反馈，这是由低氧诱导的microRNA介导的。与癌旁组织相比，MIIP在PC组织中表达下调。在体外和小鼠异种移植模型中，MIIP的过表达均显著抑制PC细胞的增殖和侵袭。我们进一步验证了MIIP在低氧条件下以HIF-1α介导的方式下调。有趣的是，尽管MIIP启动子包含两个假定的缺氧反应元件(HRE)，但染色质免疫沉淀(CHIP)和荧光素酶报告实验并不支持HIF-1a和MIIP启动子之间的主动相互作用。同时，microRNA阵列显示，低氧诱导的microRNA miR-646会损害MIIP mRNA的稳定性，从而通过靶向编码序列(CDS)来抑制其表达。巧合的是，miR-646基因的敲除通过上调MIIP的表达，显著抑制了PC细胞在体内外的增殖和侵袭能力。此外，CHIP和荧光素酶报告实验进一步证实了缺氧条件下HIF-1α激活了miR-646的转录。因此，这些结果提示HIF-1α通过上调miR-646转录在转录后水平间接调节MIIP的表达。相反，我们的结果进一步表明，MIIP抑制了组蛋白脱乙酰酶6(HDAC6)的脱乙酰酶能力，促进了HIF-1α的乙酰化和降解，从而损害了HIF-1α的积聚。此外，在PC样本中验证了下调的MIIP和上调的miR-646表达之间的特定关系。此外，miR-646和MIIP的异常表达与PC患者的分期、淋巴侵犯、转移和总生存期缩短有关。总之，我们的结果强调了HIF-1α/miR-646/MIIP的相互循环可能作为胰腺癌治疗的适用靶点。
Migration and invasion inhibitory protein (MIIP) is recently identified as an inhibitor in tumor development. However, the regulatory mechanism and biological contributions of MIIP in pancreatic cancer (PC) have been not elucidated. In this study, we demonstrated a negative feedback of MIIP and hypoxia-induced factor-1 alpha (HIF-1 alpha), which was mediated by a hypoxia-induced microRNA. Compared with paracarcinoma tissues, MIIP was downregulated in PC tissues. Overexpression of MIIP significantly impeded the proliferation and invasion of PC cells both in vitro and in mouse xenograft models. We further verified MIIP was downregulated under hypoxia in a HIF-1 alpha-mediated manner. Interestingly, although MIIP promoter containing two putative hypoxia response elements (HREs), the chromatin immunoprecipitation (ChIP) and luciferase reporter assays did not support an active interaction between HIF-1a and MIIP promoter. Meanwhile, microRNA array revealed a hypoxia-induced microRNA, miR-646, impaired stability of MIIP mRNA and consequently inhibited its expression by targeting the coding sequence (CDS). Coincidently, knockdown of miR-646 significantly repressed proliferation and invasion ability of PC cells both in vitro and in vivo by upregulating MIIP expression. Besides, ChIP and luciferase reporter assays further validated that HIF-1 alpha activated transcription of miR-646 in hypoxia condition. Therefore, these results suggested HIF-1 alpha indirectly regulated MIIP expression in post-transcriptional level through upregulating miR-646 transcription. Conversely, our results further revealed that MIIP suppressed deacetylase ability of histone deacetylase 6 (HDAC6) to promote the acetylation and degradation of HIF-1 alpha, by which impairing HIF-1 alpha accumulation. What is more, a specific relationship between downregulated MIIP and upregulated miR-646 expression was validated in PC samples. Moreover, the dysregulated miR-646 and MIIP expression was correlated with advanced tumor stage, lymphatic invasion, metastasis and shorter overall survival in PC patients. Together, our results highlight that the reciprocal loop of HIF-1 alpha/miR-646/MIIP might be implemented as an applicable target for pancreatic cancer therapy.