Role of GLI in Tumor progression

描述(由申请人提供)：在发育过程中和正常成人组织中，由声波刺猬(SHH)发出的信号是增殖和形态发生的重要调节机制。ShH结合并拮抗肿瘤抑制因子PTCH的活性，PTCH是一种在皮肤基底细胞癌(BCC)、髓母细胞瘤和横纹肌肉瘤中重要的把关分子。功能丧失和功能获得的研究支持GLI家族锌指转录因子在Hedgehog信号传递中的作用。在最常见的BCC中，GLI的表达始终是由于PTCH或该途径中其他分子的突变而诱导的。GLI或GL12在小鼠皮肤中的表达足以诱发基底细胞癌。 为了更好地了解GLI在肿瘤进展中的作用，我们对表达GLI的RK3E上皮细胞进行了广泛的鉴定，以确定可能的靶基因。采用抑制性消减杂交和微阵列分析相结合的方法鉴定GLI诱导的转录本。已鉴定的转录本没有与其他几个癌基因的转化相关的改变，包括RAS、c-myc或GKLF/KLF4。与对照细胞相比，携带PTCH缺陷等位基因的小鼠胚胎细胞显示出其中几个转录本的表达增加，这表明内源性GLI的表达足以满足某些观察到的转录效应。 原位杂交显示，与GLI阴性毛囊相比，GLI阳性毛囊和人基底细胞癌中GLI诱导的转录本表达增加。与其他转化RK3E的癌基因不同，GLI特异性地诱导分子或癌基因的表达，这些分子或癌基因可在发育过程中诱导上皮-间充质转化(EMT)。在体外，GLI同样诱导了先前观察到的人基底细胞癌基因表达的多种变化。 我们建议鉴定与直接转录靶基因相对应的转录本，确定GLI诱导的特定转录本在小鼠基底细胞癌模型中的作用，并将GLI诱导的转录本表征为体外和体内转化的潜在效应因子。

DESCRIPTION (provided by applicant): Signaling by sonic hedgehog (SHH) during development and in normal adult tissues is an important regulatory mechanism for proliferation and morphogenesis. SHH binds to and antagonizes the activity of the tumor suppressor PTCH, a gatekeeper molecule important in basal cell carcinoma of the skin (BCC), medulloblastoma, and rhabdomyosarcoma. Loss-of-function and gain-of-function studies support a role for the GLI family of zinc finger transcription factors in transmission of the hedgehog signal. In BCC, a most common form of carcinoma, GLI expression is consistently induced as a result of mutation of PTCH or of other molecules in the pathway. Expression of GLI or GL12 in mouse skin is sufficient to induce BCC. To better understand the role of GLI in tumor progression, we extensively characterized GLI-expressing RK3E epithelial cells to identify putative target genes. The techniques of suppression subtractive hybridization and microarray analysis were used in combination to identify GLI-induced transcripts. The identified transcripts were not altered in association with transformation by several other oncogenes, including RAS, c-MYC, or GKLF/KLF4. Compared with control cells, mouse embryo cells harboring defective alleles of PTCH exhibited increased expression of several of these transcripts, suggesting that expression of endogenous GLI is sufficient for some of the observed transcriptional effects. mRNA in situ hybridization revealed increased expression of GLI-induced transcripts in GLI-positive hair follicles and in human BCC, compared with GLI-negative hair follicles. Unlike other oncogenes that transform RK3E, GLI specifically induced expression of molecules or oncogenes known to induce epithelial-mesenchymal transition (EMT) in development. Multiple alterations in gene expression previously observed in human BCC were likewise induced by GLI in vitro. We propose to identify transcripts that correspond to direct transcriptional target genes, to determine a role for specific GLI-induced transcripts in a mouse model of BCC, and to characterize specific GLI-induced transcripts as potential effectors of transformation in vitro and in vivo.