Laboratory of Transcription and Cell Signaling, Institute of Medical Biochemistry and Laboratory Diagnostics, Charles University in Prague, 1st Faculty of Medicine, Prague, Czech Republic.
Institute of Pathology, Charles University in Prague, 1st Faculty of Medicine and General University Hospital in Prague, Prague, Czech Republic.
Cell Death Dis. 2016 Jan 14;7(1):e2048. doi: 10.1038/cddis.2015.389.
Survivin, an important antiapoptotic protein, is expressed in tumors, whereas in normal tissues the expression of this protein is extremely low, defining a role for survivin as a cancer gene. Survivin exhibits multifunctional activity in tumor cells. However, why survivin expression is sharply and invariably restricted to tumor tissue remains unclear. Here, we identified 11 putative consensus binding sites for GLI transcription factors in the survivin promoter and characterized the promoter activity. Inhibitors of the Hedgehog/GLI pathway, cyclopamine and GANT61, decreased the promoter activity in reporter assays. ΔNGLI2 (which lacks the repressor domain) was the most potent vector in activating the survivin promoter-reporter. Moreover, GANT61, a GLI1/2 inhibitor, repressed endogenous survivin protein and mRNA expression in most cells across a large panel of tumor cell lines. Chromatin immunoprecipitation showed GLI2 binding to the survivin promoter. The ectopic GLI2-evoked expression of endogenous survivin was observed in normal human fibroblasts. GANT61 decreased survivin level in nude mice tumors, mimicking the activity of GANT61 in cultured cells. The immunohistochemistry and double immunofluorescence of human tumors revealed a correlation between the tissue regions showing high GLI2 and survivin positivity. Thus, these results demonstrated that survivin is a classical transcriptional target of GLI2, a Hedgehog pathway signaling effector. This potentially reflects the high expression of survivin in human tumor cells. As the Hedgehog pathway is upregulated in virtually all types of cancer cells, these findings substantially contribute to the explanation of uniform survivin expression in tumors as a potential target for the development of a more effective treatment of cancers through the inhibition of GLI2 to restrain survivin activity.
Survivin,一种重要的抗凋亡蛋白,在肿瘤中表达,而在正常组织中这种蛋白的表达极低,这定义了 survivin 作为癌基因的作用。Survivin 在肿瘤细胞中具有多功能活性。然而,为什么 survivin 的表达如此急剧和始终局限于肿瘤组织尚不清楚。在这里,我们在 survivin 启动子中鉴定了 11 个推定的 GLI 转录因子的共有结合位点,并对启动子活性进行了表征。Hedgehog/GLI 通路的抑制剂 cyclopamine 和 GANT61 在报告基因检测中降低了启动子活性。缺乏抑制域的 ΔNGLI2 是激活 survivin 启动子-报告子的最有效载体。此外,GLI1/2 抑制剂 GANT61 抑制了大多数肿瘤细胞系中大多数细胞内源性 survivin 蛋白和 mRNA 的表达。染色质免疫沉淀显示 GLI2 与 survivin 启动子结合。在正常的人成纤维细胞中观察到异位 GLI2 诱导的内源性 survivin 的表达。GANT61 降低了裸鼠肿瘤中的 survivin 水平,模拟了 GANT61 在培养细胞中的活性。人类肿瘤的免疫组织化学和双重免疫荧光显示,组织区域中显示出高 GLI2 和 survivin 阳性之间存在相关性。因此,这些结果表明 survivin 是 GLI2 的经典转录靶标,是 Hedgehog 通路信号效应物。这可能反映了 survivin 在人类肿瘤细胞中的高表达。由于 Hedgehog 通路在几乎所有类型的癌细胞中都被上调,这些发现极大地促进了对肿瘤中 survivin 表达均匀的解释,作为通过抑制 GLI2 来抑制 survivin 活性从而开发更有效的癌症治疗方法的潜在靶点。