Identification and characterization of genetic regulators in cancer stem cell

描述(申请人提供)：乳腺癌干细胞已被鉴定为CD44？/Low乳腺肿瘤细胞，在小鼠模型中仅保留形成新肿瘤的能力。癌症干细胞可以直接来自正常干细胞的突变，也可以来自导致干细胞特性恢复的祖细胞突变。虽然CD44在乳腺上皮细胞分化过程中正常下调，但在高达85%的人类乳腺癌中都有表达，而且CD44的异位表达被证明促进了转移。由于调控CD44表达的途径发生突变，乳腺干细胞中CD44基因的失控可能与肿瘤的转化有关。因此，深入剖析调控乳腺干细胞CD44表达、调控干细胞分化过程中CD44表达下调的分子机制(S)是非常重要的。除了DNA甲基化等表观遗传控制外，基因表达还可以由遗传元件(例如，顺式调控因子，即控制特定细胞类型的基因表达/抑制的非编码DNA序列)控制。由于基因组的高度复杂性，在脊椎动物中寻找决定细胞类型特异性(干细胞与分化细胞)基因表达的顺式调控因子仍然是一项艰巨的任务。然而，许多顺式调节因子往往在进化上跨物种保守的事实为利用比较基因组方法鉴定这些顺式调节因子提供了基础。我们的方法使用计算机预测和“湿实验室”验证方法来识别CD44基因的关键顺式调节因子和反式作用因子，这是非常有创新性的。进化保守的非编码区用于预测顺式调节基因，大大减少了假阳性，从而减少了实验验证的工作量。它为破译复杂的CD44转录调控提供了一种综合途径。了解CD44表达的调控机制可能最终导致识别在乳腺干细胞或细胞向肿瘤转化过程中可能发生突变的途径，从而可能为乳腺癌的治疗提供新的治疗靶点。公共卫生相关性：这项建议的目标是剖析调控乳腺癌干细胞标记物CD44表达的分子机制。了解CD44表达的调控机制最终可能导致识别在乳腺干细胞或分化层次更低的细胞的致癌转化过程中可能发生突变的途径，从而为乳腺癌的治疗提供新的治疗靶点，直接针对肿瘤的起源。

DESCRIPTION (provided by applicant): Breast cancer stem cells have been identified as CD44?/low breast tumor cells that exclusively retain the ability to form new tumors in mouse models. Cancer stem cells can arise from mutations in normal stem cells directly, or from mutations in progenitor cells that lead to the regaining of stem cell property. Although normally down-regulated during mammary epithelial differentiation, CD44 is expressed in up to 85% human breast cancers and the ectopic expression of CD44 has been shown to promote metastasis. It is possible that the deregulation of CD44 in breast stem cell is associated with tumorigenic transformation due to mutations in pathways that regulate CD44 expression. Therefore it is extremely important to dissect the molecular mechanism(s) that regulates CD44 expression in breast stem cells and controls CD44 down-regulation during stem cell differentiation. Gene expression can be controlled by genetic elements (e.g., cis-regulators, i.e., non- coding DNA sequences that control cell type-specific expression/suppression of genes), in addition to epigenetic controls such as DNA methylation. Due to the highly complex nature of the genome, finding cis-regulators, which determine cell type-specific (stem cells versus differentiated cell) gene expression, in vertebrates remains a difficult task. However, the fact that many cis-regulators are often evolutionarily conserved across species provides a basis for the identification of these cis-regulators using comparative genomic method. Our approach employing in silico predication and "wet lab" verification methods to identify crucial cis-regulators and trans-acting factors of the CD44 gene is highly innovative. Evolutionarily conserved non-coding regions for the prediction of cis-regulators greatly reduced false positives, hence, work load for experimental verification. It provides an integrative way to decode the complicated transcriptional regulation of CD44. Understanding regulatory mechanisms of CD44 expression could ultimately lead to the identification of pathways that could be mutated during the tumorigenic transformation of breast stem cells or cells further down the differentiation hierarchy and thus may provide new therapeutic targets for treatment of breast cancer. PUBLIC HEALTH RELEVANCE: The goal of this proposal is to dissect molecular mechanisms that regulate the expression of the breast cancer stem cell marker CD44 .Understanding regulatory mechanisms of CD44 expression could ultimately lead to the identification of pathways that could be mutated during tumorigenic transformation of breast stem cells or cells further down the differentiation hierarchy and thus provide novel therapeutic targets for treatment of breast cancer, aimed directly at the origin of the tumor.