Wang Yan, Liu Dongping, Chen Pingping, Koeffler H Phillip, Tong Xiangjun, Xie Dong
Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
Cancer Res. 2008 Feb 15;68(4):1136-43. doi: 10.1158/0008-5472.CAN-07-5021.
IFN-gamma is an antitumor cytokine that inhibits cell proliferation and induces apoptosis after engagement with the IFN-gamma receptors (IFNGR) expressed on target cells, whereas IFN regulatory factor 2 (IRF-2) is able to block the effects of IFN-gamma by repressing transcription of IFN-gamma-induced genes. Thus far, few studies have explored the influences of IFN-gamma on human esophageal cancer cells. In the present study, therefore, we investigated in detail the functions of IFN-gamma in esophageal cancer cells. The results in clinical samples of human esophageal cancers showed that the level of IFN-gamma was increased in tumor tissues and positively correlated with tumor progression and IRF-2 expression, whereas the level of IFNGR1 was decreased and negatively correlated with tumor progression and IRF-2 expression. Consistently, in vitro experiments showed that low concentration of IFN-gamma induced the expression of IRF-2 with potential promotion of cell growth, and moreover, IRF-2 was able to suppress IFNGR1 transcription in human esophageal cancer cells by binding a specific motif in IFNGR1 promoter, which lowered the sensitivity of esophageal cancer cells to IFN-gamma. Taken together, our results disclosed a new IRF-2-mediated inhibitory mechanism for IFN-gamma-induced pathway in esophageal cancer cells: IFN-gamma induced IRF-2 up-regulation, then up-regulated IRF-2 decreased endogenous IFNGR1 level, and finally, the loss of IFNGR1 turned to enhance the resistance of esophageal cancer cells to IFN-gamma. Accordingly, the results implied that IRF-2 might act as a mediator for the functions of IFN-gamma and IFNGR1 in human esophageal cancers.
γ干扰素是一种抗肿瘤细胞因子,与靶细胞上表达的γ干扰素受体(IFNGR)结合后可抑制细胞增殖并诱导凋亡,而干扰素调节因子2(IRF-2)能够通过抑制γ干扰素诱导基因的转录来阻断γ干扰素的作用。迄今为止,很少有研究探讨γ干扰素对人食管癌细胞的影响。因此,在本研究中,我们详细研究了γ干扰素在食管癌细胞中的功能。人食管癌临床样本结果显示,肿瘤组织中γ干扰素水平升高,且与肿瘤进展和IRF-2表达呈正相关,而IFNGR1水平降低,与肿瘤进展和IRF-2表达呈负相关。同样,体外实验表明,低浓度的γ干扰素诱导IRF-2表达,可能促进细胞生长,此外,IRF-2能够通过结合IFNGR1启动子中的特定基序抑制人食管癌细胞中IFNGR1的转录,从而降低食管癌细胞对γ干扰素的敏感性。综上所述,我们的结果揭示了食管癌细胞中一种新的IRF-2介导的γ干扰素诱导途径的抑制机制:γ干扰素诱导IRF-2上调,上调的IRF-2随后降低内源性IFNGR1水平,最终,IFNGR1的缺失转而增强食管癌细胞对γ干扰素的抗性。因此,结果表明IRF-2可能是人食管癌中γ干扰素和IFNGR1功能的介导因子。