Klf4 in tumor initiation and maintenance of squamous cell carcinoma

KLF4转录因子在细胞命运和上皮细胞分化中起重要作用。KLF4快速 在小鼠中引发皮肤鳞状细胞癌(SCC)，并在人类的早期阶段解除管制 皮肤肿瘤进展。使用条件性KLF4-ER融合蛋白，我们鉴定了细胞命运决定因素 Notch 1作为KLF4的转录靶点。在培养细胞、转基因小鼠和人类肿瘤中，KLF4 Notchl的表达与Notchl、Notchl配体和Notchl效应因子(如Cyclin D1)的表达有关。 RK3E上皮细胞的转化需要Notchl。这些研究确定了KLF4-Notch1途径 在正常上皮细胞和肿瘤细胞的细胞命运决定中具有重要意义。 KLF4的诱变鉴定出显性负性(DN)等位基因，可阻断KLF4的体外转化。 KLF4-DNS鉴定KLF4在特定人类细胞类型的体外生长和转化中的作用 特异性转化癌基因，如ErbB2和c-myc。 为了研究KLF4在皮肤鳞状细胞癌中的作用，我们建立了一种新的高渗透皮肤鳞状细胞癌模型。 给转基因小鼠注射致癌物质。肿瘤在组织上与人类相似 并表达鳞癌标志物P53、角蛋白14和Notch！在此模型中开发的SCCS 包括KLF4阳性的肿瘤和一些KLF4阴性的肿瘤。 为了了解正常调节KLF4的机制，我们将研究翻译后的作用 突变的KLF4蛋白的dN活性的修饰(目标1)。内源性KLF4在肿瘤中的作用 在新的鳞状细胞癌小鼠模型中，将使用条件的、Cre介导的方法来研究启动和维持 KLF4/loxP等位基因的缺失以及四环素诱导的转基因小干扰RNA或KLF4-dN的表达 小鼠(目标2)。使用类似的功能丧失和功能获得策略，KLF4在乳腺上皮中的作用 将确定ErbB2的发展和转型(目标3)。在《目标4》中，翻译后控制 对小鼠和人鳞状细胞癌中Klf4转录上调负责的基因将进行分析 鉴定KLF4基因中的RNA不稳定元件。 这些研究可能为KLF4和Notch1在普通人发病机制中的作用提供支持 鳞状细胞癌和乳腺癌等癌症。因此，研究的完成将确定这条路径是一条 为预防和治疗提供目标，并提供评估此类疗法的新动物模型。

The KLF4 transcription factor is important in cell fate and differentiation of epithelial cells. KLF4 rapidly initiates cutaneous squamous cell carcinoma (SCC) in mice, and is deregulated at an early step in human skin tumor progression. Using a conditional KLF4-ER fusion protein, we identified the cell fate determinant Notch 1 as a transcriptional target of KLF4. In cultured cells, in transgenic mice and in human tumors, KLF4 expression is associated with expression of Notchl, Notchl ligands, and Notchl effectors such as Cyclin D1. Transformation of RK3E epithelial cells requires Notchl. These studies identify a KLF4-Notch1 pathway that appears important in cell fate specification of normal epithelial cells and tumor cells. Mutagenesis of KLF4 identified dominant negative (DN) alleles that block transformation in vitro by KLF4. KLF4-DNs identify a role of KLF4 in growth of specific human cell types in vitro, and in transformation by specific transforming oncogenes such as ErbB2 and c-MYC. To study the role of Klf4 in cutaneous SCC we developed a novel highly penetrant model of SCC by administering carcinogens to genetically-engineered mice. Tumors were histologically similar to human SCC, and expressed SCC markers such as p53, keratin 14, and Notch! SCCs that developed in this model included KLF4-positive tumors and some tumors that were KLF4-negative. To understand the mechanisms that normally regulate KLF4, we will study the role of posttranslational modifications in the DN activity of mutant KLF4 proteins (Aim 1). The role of endogenous Klf4 in tumor initiation and maintenance will be studied in the new SCC mouse model using conditional, Cre-mediated deletion of Klf4/LoxP alleles, and by tetracycline-inducible expression of siRNA or KLF4-DN in transgenic mice (Aim 2). Using similar loss- and gain-of-function strategies, the role of Klf4 in mammary epithelial development and in transformation by ErbB2 will be determined (Aim 3). In Aim 4, a posttranslational control that appears responsible for upregulation of Klf4 transcripts in mouse and human SCC will be analyzed by identifying RNA destabilizing elements in the KLF4 cDNA. These studies may provide support of a role for KLF4 and Notchl in pathogenesis of common human cancers such as SCC and breast cancer. Thus, completion of the studies would identify this pathway as a target for prevention and treatment, and provide new animal models in which to assess such therapies.