p120 and Kaiso dysregulation in intestinal tumorigenesis

描述（由申请人提供）：结直肠癌是最常见的癌症诊断形式之一，也是美国癌症相关死亡的第三大原因。肿瘤抑制性腺瘤性结肠息肉病（APC）基因的缺失是约80%这些癌症的起始突变，也是家族性腺瘤性结肠息肉病（FAP）背后的驱动突变。APC基因产物（Apc）的缺失激活经典Wnt信号通路，最终导致细胞增殖、转化和肿瘤形成。使用各种 在APC突变小鼠模型中，我发现APC消融在时间和空间上与Kaiso的急剧上调相一致，Kaiso是粘附连接蛋白p120-连环蛋白（p120）的核结合伴侣。我们先前的数据进一步显示在Wnt活化的所有情况下Kaiso的强核表达，因为Kaiso在肠隐窝的干细胞区室中天然上调，并且在APC损失或β-连环蛋白活化后异常上调。我们小组和其他人的工作进一步表明，Kaiso的这种上调可能在APC丢失引发的肿瘤促进事件中发挥关键作用。基于这些观察结果，我的工作假设是Kaiso表达直接或间接受经典Wnt通路的调节。此外，我认为Kaiso的组成性上调可能是APC丢失致瘤后果的关键效应子。以下目的旨在确定Kaiso上调的机制和Kaiso消融的分子后果。在目标1中，我将优化我设计的检测方法，以明确询问体内APC消融的直接物理和分子后果。这种“快速上位性测定”（下文称为REA）将允许在肿瘤形成的精确微环境背景下有效分析APC消融的效果。在目标2中，我将确定APC消融后Kaiso上调的机制。将确定Kaiso转录、翻译和蛋白质稳定性的改变，目的是确定阻断Kaiso上调的方法。最后，由于ApcMin/+模型中的Kaiso消融显著延迟肿瘤形成，因此Aim 3将利用REA与分子和形态学读数的组合来阐明负责肿瘤衰减表型的机制（例如，减少的细胞增殖、拯救的细胞沿着绒毛迁移、去分化逆转等）。Kaiso消融表型的分子效应器可能最终为药物干预提供新的靶点。 公共卫生相关性：肿瘤抑制因子结肠腺瘤性息肉病（APC）的缺失是约80%散发性结直肠癌（CRC）的起始事件。我们发现，Kaiso，p120-catenin（p120）的核结合伴侣，被APC突变大幅上调，这种上调在CRC肿瘤发生中起着积极的作用。了解导致APC损失下游Kaiso上调的机制可能会导致药物干预的新分子靶点。

DESCRIPTION (provided by applicant): Colorectal cancer is the one of the most commonly diagnosed forms of cancer and the third leading cause of cancer-related deaths in the United States. Loss of the tumor suppressor adenomatous polyposis coli (APC) gene is the initiating mutation in ~80% of these cancers and the driving mutation behind familial adenomatous polyposis coli (FAP). Loss of the APC gene product (Apc) activates the Canonical Wnt signaling pathway, culminating in cell proliferation, transformation, and tumor formation. Using a variety of APC mutant mouse models, I have found that APC ablation coincides temporally and spatially with drastic upregulation of Kaiso, a nuclear binding partner of the adherens junction protein, p120-catenin (p120). Our previous data further show strong nuclear expression of Kaiso in all instances of Wnt activation, as Kaiso is naturally upregulated in the stem cell compartment of the intestinal crypt and aberrantly upregulated following either APC loss or -catenin activation. Work from our group and others further suggest that this upregulation of Kaiso may play a critical role in the tumor promoting events triggered by APC loss. Based on these observations, my working hypothesis is that Kaiso expression is directly or indirectly regulated by the canonical Wnt pathway. Additionally, I propose that constitutive upregulation of Kaiso may be a critical effector of the tumorigenic consequences of APC loss. The following aims seek to define the mechanism(s) of Kaiso upregulation and the molecular consequences of Kaiso ablation. In Aim 1, I will optimize an assay I have designed expressly to interrogate immediate physical and molecular consequences of APC ablation in vivo. This "Rapid Epistasis Assay" (hereafter, REA) will permit efficient analysis of the effects of APC ablation in the precise microenvironmental context of tumor formation. In Aim 2, I will identify the mechanism(s) of Kaiso upregulation following APC ablation. Alterations in Kaiso transcription, translation, and protein stability willbe determined with the goal of identifying means of blocking Kaiso upregulation. Finally, as Kaiso ablation in the ApcMin/+ model markedly delays tumor formation, Aim 3 will utilize the REA in combination with molecular and morphological readouts to clarify the mechanism(s) responsible for the tumor attenuating phenotype (e.g., reduced cell proliferation, rescued cell migration along the villus, reversal of dedifferentiation, etc.). Molecular effectors of the Kaiso ablation phenotype may ultimately provide novel targets for pharmaceutical intervention. PUBLIC HEALTH RELEVANCE: Loss of the tumor suppressor Adenomatous Polyposis Coli (APC) is the initiating event in ~80% of sporadic colorectal cancers (CRC). We show that Kaiso, a nuclear binding partner of p120-catenin (p120), is drastically upregulated by APC mutation and this upregulation plays a positive role in CRC tumorigenesis. Understanding the mechanisms that lead to Kaiso upregulation downstream of APC loss may lead to novel molecular targets for pharmaceutical intervention.