Transcriptional repression of interferon-gamma-inducible gene by hypoxia

缺氧对干扰素γ诱导基因的转录抑制

• 批准号: 20791360
• 负责人: HIROI Miki
• 金额: $ 2.75万
• 依托单位: Meikai University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Young Scientists (B)
• 财政年份: 2008
• 资助国家: 日本
• 起止时间: 2008 至 2009
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20791360/
• 关键词: ケモカイン; 低酸素; インターフェロン; 転写; CXCL9; CXCL10

Interferon-γ (IFN-γ) is a pleiotropic cytokine that exerts anti-tumor activity to various cancer cells. IFNγ induces Mig/CXCL9 and IP10/CXCL10, members of the CXC chemokine family, have been shown to induce potent lymphocyte chemotaxis and play an important role in tumor rejection. In the tumor microenvironment, most solid tumors develop regions of low oxygen tension called hypoxia, which is due to an imbalance in oxygen supply and consumption. We have previously shown that hypoxia inhibited the IFN-γ induced expression of chemokines CXCL9 and CXCL10 in human tumor cell lines. Although hypoxia (1% O2) markedly inhibited IFN-γ -induced expression of CXCL9 and CXCL10 mRNAs in human oral squamous carcinoma cell line, hypoxia had no effect on the levels of tyrosine-phosphorylated and nuclear-translocated STAT1. Furthermore,Chromatin immunoprecipitation assay demonstrated that although STAT1 was recruited to the promoter region of the CXCL9 and CXCL10 gene under hypoxia, recruitments of RNA polymerase II and coactivator SRC-1 was inhibited under hypoxia. In the present study, we further investigated the mechanisms by which hypoxia down-regulates the IFN-y-induced CXCL9 and CXCL10 gene expression. IFNγ-induced phosphorylation of STAT1 (Ser727) was down-regulated under the hypoxia in HSC-2 cell. However, the inhibitory effect of hypoxia on the phosphorylation was not observed in HSC-3 and T98G cells, suggesting that the inhibition of STAT1 Ser727 by hypoxia is a cell-type specific phenomenon. Furthermore, U3A cells transfected with mutant STAT1 in which Ser727 had been mutated to Glu, which mimics the phosphorylated status of Ser727, were also inhibited by hypoxia for the IFN-y-induced CXCL9 and CXCL10 gene expression. Taken together these results suggest that the inhibition of STAT1 Ser727 does not involved in the inhibition of IFN-γ-induced gene expression.

干扰素-γ（IFN-γ）是一种对多种癌细胞发挥抗肿瘤活性的多效性细胞因子。IFNγ诱导CXC趋化因子家族成员Mig/CXCL 9和IP 10/CXCL 10，已显示诱导有效的淋巴细胞趋化性并在肿瘤排斥中起重要作用。在肿瘤微环境中，大多数实体肿瘤发展出低氧张力区域，称为缺氧，这是由于氧供应和消耗的不平衡。我们先前已经表明，缺氧抑制IFN-γ诱导的人肿瘤细胞系中趋化因子CXCL 9和CXCL 10的表达。低氧（1%O2）可显著抑制IFN-γ诱导的人口腔鳞癌细胞CXCL 9和CXCL 10 mRNA的表达，但对酪氨酸磷酸化和核转位的STAT 1水平无影响。此外，染色质免疫沉淀试验表明，虽然在缺氧条件下，STAT 1被募集到CXCL 9和CXCL 10基因的启动子区域，RNA聚合酶II和辅激活因子SRC-1的募集在缺氧条件下受到抑制。在本研究中，我们进一步研究了缺氧下调IFN-γ诱导的CXCL 9和CXCL 10基因表达的机制。低氧可下调IFNγ诱导的HSC-2细胞STAT 1（Ser 727）磷酸化水平。然而，在HSC-3和T98 G细胞中未观察到低氧对STAT 1 Ser 727磷酸化的抑制作用，这表明低氧对STAT 1 Ser 727磷酸化的抑制是细胞类型特异性现象。此外，用突变体STAT 1转染的U3 A细胞，其中Ser 727已经突变为Glu，其模拟Ser 727的磷酸化状态，也被缺氧抑制IFN-γ诱导的CXCL 9和CXCL 10基因表达。综上所述，这些结果表明STAT 1 Ser 727的抑制不参与IFN-γ诱导的基因表达的抑制。