BMI1 and MEL18 Promote Colitis-Associated Cancer in Mice via REG3B and STAT3
BMI1 and MEL18 Promote Colitis-Associated Cancer in Mice via REG3B and STAT3
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BMI1 和 MEL18 通过 REG3B 和 STAT3 促进小鼠结肠炎相关癌症
DOI：
10.1053/j.gastro.2017.07.044
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发表时间：
2017-12-01
期刊：
影响因子：
29.4
通讯作者：
Xi, Rongwen
中科院分区：
文献类型：
--
作者：
Liu, Xicheng;Wei, Wendi;Xi, Rongwen
背景与目的：Polycomb基团蛋白是抑制基因表达的表观遗传因子，在肿瘤细胞中表达失调，其致癌机制尚不清楚。我们研究了BMI1原癌基因、多梳环指(BMI1)和多梳环指2(PCGF2，又称MEL18)是否参与了小鼠结肠炎相关癌(CAC)的发生和发展。方法：我们利用Villin-Cre启动子(称为Bmi1(Delta IEC)、Mel18(Delta IEC)、DKO和TKO小鼠)建立了含有Bmi1和/或Mel18和/或Reg3b等位基因的小鼠。我们还使用Villin-Creer(T2)诱导的启动子在肠上皮细胞(IECS)中特异性地干扰了Bmi1和/或Mel18。在cre阴性的产仔小鼠(对照组)和条件阻断Bmi1和/或Mel18的小鼠身上，通过向饮用水中注射偶氮甲烷(AOM)和添加葡聚糖硫酸钠(DSS)的方法诱导CAC。收集小鼠结肠组织，进行组织学和免疫印迹分析；分离IECs，用于基因芯片分析。结果：给予AOM和DSS后，DKO小鼠的息肉发生率显著低于对照组、Bmi1(Delta IEC)、Mel18(Delta IEC)、Reg3b(Delta IEC)或TKO小鼠。DKO小鼠结肠腺瘤为低度异型增生，而对照组、Bmi1DIEC、Mel18DIEC、Reg3bDIEC或TKO小鼠结肠腺瘤为高度异型增生并侵袭粘膜肌层。在癌变后期阻断Bmi1和Mel18(DKO小鼠)显著减少大腺瘤的数量和腺瘤总量，减少结肠组织的增殖和增加细胞凋亡。与对照组、Bmi1DIEC和Mel18DIEC小鼠相比，经AOM和DSS处理的DKO小鼠分离的IECs中Reg3b的表达增加。REG3B的表达足以抑制细胞因子诱导的IECS中STAT3的激活。人REG3β蛋白在人293T细胞中的表达水平与pSTAT3水平和患者的生存时间呈负相关。结论：BMI1和MEL18通过抑制Reg3b的表达，促进细胞增殖，减少细胞凋亡，参与了小鼠CAC的发生发展。REG3B负性调节细胞因子诱导的结肠上皮细胞中STAT3的激活。这一途径可能针对结肠炎患者，以减少癌变。
BACKGROUND & AIMS: Polycomb group proteins are epigenetic factors that silence gene expression; they are dysregulated in cancer cells and contribute to carcinogenesis by unclear mechanisms. We investigated whether BMI1 protooncogene, polycomb ring finger (BMI1), and polycomb group ring finger 2 (PCGF2, also called MEL18) are involved in the initiation and progression of colitis-associated cancer (CAC) in mice. METHODS: We generated mice containing floxed alleles of Bmi1 and/or Mel18 and/or Reg3b using the villin-Cre promoter (called Bmi1(Delta IEC), Mel18(Delta IEC), DKO, and TKO mice). We also disrupted Bmi1 and/or Mel18 specifically in intestinal epithelial cells (IECs) using the villin-CreER(T2)-inducible promoter. CAC was induced in cre-negative litter-mate mice (control) and mice with conditional disruption of Bmi1 and/or Mel18 by intraperitoneal injection of azoxy-methane (AOM) followed by addition of dextran sulfate sodium (DSS) to drinking water. Colon tissues were collected from mice and analyzed by histology and immunoblots; IECs were isolated and used in cDNA microarray analyses. RESULTS: Following administration of AOM and DSS, DKO mice developed significantly fewer polyps than control, Bmi1(Delta IEC), Mel18(Delta IEC), Reg3b(Delta IEC), or TKO mice. Adenomas in the colons of DKO mice were low-grade dysplasias, whereas adenomas in control, Bmi1DIEC, Mel18DIEC, Reg3bDIEC, or TKO mice were high-grade dysplasias with aggressive invasion of the muscularis mucosa. Disruption of Bmi1 and Mel18 (DKO mice) during late stages of carcinogenesis significantly reduced the numbers of large adenomas and the load of total adenomas, reduced proliferation, and increased apoptosis in colon tissues. IECs isolated from DKO mice after AOM and DSS administration had increased expression of Reg3b compared with control, Bmi1DIEC, or Mel18DIEC mice. Expression of REG3B was sufficient to inhibit cytokine-induced activation of STAT3 in IECs. The human REG3 beta protein, the functional counterpart of mouse REG3B, inhibited STAT3 activity in human 293T cells, and its expression level in colorectal tumors correlated inversely with pSTAT3 level and survival times of patients. CONCLUSIONS: BMI1 and MEL18 contribute to the development of CAC in mice by promoting proliferation and reducing apoptosis via suppressing expression of Reg3b. REG3B negatively regulates cytokine-induced activation of STAT3 in colon epithelial cells. This pathway might be targeted in patients with colitis to reduce carcinogenesis.