Post-Transcriptional Regulation in Colorectal Cancer

描述（由申请人提供）：结直肠癌是成人癌症死亡的主要原因。在结肠癌细胞和肿瘤中通常观察到许多生长和炎症相关的立即早期反应基因的过表达。控制这些因子在正常肠上皮中表达的关键点是通过调节mRNA衰变的转录后机制发生。与转录后调节相关的两种主要RNA结合蛋白是mRNA稳定因子Hu抗原R（HuR）和mRNA衰变因子tristetraprolin（TTP）。这两种因子结合存在于大多数癌症相关的立即早期反应基因转录物中的富含AU的mRNA元件（ARE），并靶向mRNA以稳定或快速衰减。然而，在结肠癌细胞和肿瘤中观察到的特征性特征是稳定因子HuR的过表达和衰变因子TTP的表达丧失。这些组合的缺陷允许癌症相关生长因子的稳定和过度表达。基于这些观察结果，我们推测，转录后调控的损失，促进肠上皮细胞肿瘤的发生，通过选择性地稳定AU丰富的元素含有mRNA转录。为检验这一假设，提出了以下具体目标。具体目标1：确定mRNA稳定因子HuR和mRNA衰减因子TTP的表达改变是否可以促进肠细胞转化和肿瘤发生。在目标1下，我们将确定HuR过表达和TTP损失是否通过缺陷性快速mRNA衰减和癌症相关基因过表达的机制在促进上皮细胞转化和肿瘤发生中发挥因果作用。具体目标二：确定HuR的低分子量抑制剂和病毒介导的TTP递送影响结肠癌细胞生长和基因表达的能力。这一目标的重点是研究靶向HuR介导的mRNA稳定的治疗潜力。具体目标3：确定小鼠胃肠道中HuR过表达和TTP丢失是否促进体内癌症相关基因表达和肿瘤发生。在这个特定的目标，我们将确定在体内的意义，HuR过表达和TTP损失，促进肠道肿瘤的发生。具体目标4：确定结肠癌细胞和肿瘤中促进HuR过表达和TTP表达沉默的分子事件。在此目标下，我们将确定促进HuR表达和TTP基因沉默在结肠癌中的机制。这项研究将增强我们对结直肠癌生物学的理解，并导致新的分子靶点的鉴定，这将改善目前的治疗和预防策略。 公共卫生相关性：结直肠癌是美国成年人癌症发病和死亡的主要原因。在结直肠癌细胞和肿瘤中，发生许多生长和炎症相关基因的不受控制的表达。通过更好地了解参与控制这些因子表达的细胞机制，我们的目标是识别和定义控制结直肠癌基因表达的新分子靶点，并改善当前的治疗和预防策略。

DESCRIPTION (provided by applicant): Colorectal cancer is a leading cause of cancer mortality among adults. Commonly observed in colon cancer cells and tumors is overexpression of many growth- and inflammation-associated immediate-early response genes. A critical point in controlling the expression of these factors in normal intestinal epithelium occurs through post-transcriptional mechanisms that regulate mRNA decay. The two primary RNA-binding proteins associated with post-transcriptional regulation are the mRNA stability factor Hu antigen R (HuR) and the mRNA decay factor tristetraprolin (TTP). Both of these factors bind AU-rich mRNA elements (ARE) present in a majority of cancer-associated immediate-early response gene transcripts and target the mRNA for stabilization or rapid decay. However, a characteristic feature observed in colon cancer cells and tumors is overexpression of the stability factor HuR and loss of expression of the decay factor TTP. These combined defects allow for stabilization and overexpression of cancer-associated growth factors. Based on these observations we hypothesize that loss of post-transcriptional regulation promotes intestinal epithelial cell tumorigenesis by selectively stabilizing AU-rich element containing-mRNA transcripts. The following specific aims are proposed to test this hypothesis. Specific Aim 1: Determine whether altered expression of the mRNA stability factor HuR and the mRNA decay factor TTP can promote intestinal cell transformation and tumorigenesis. Under Aim 1 we will determine whether HuR overexpression and TTP loss play a causal role in promoting epithelial cell transformation and tumorigenesis through a mechanism of defective rapid mRNA decay and cancer-associated gene overexpression. Specific Aim 2: Determine the ability of low-molecular- weight inhibitors of HuR and viral-mediated delivery of TTP to impact colon cancer cell growth and gene expression. The emphasis of this aim is to investigate the therapeutic potential of targeting HuR-mediated mRNA stabilization. Specific Aim 3: Determine if HuR overexpression and TTP loss in the murine gastrointestinal tract promotes cancer-associated gene expression and tumorigenesis in vivo. In this Specific Aim we will determine the in vivo significance of HuR overexpression and TTP loss in promoting intestinal tumorigenesis. Specific Aim 4: Determine the molecular events in colon cancer cells and tumors that promote HuR overexpression and silencing of TTP expression. Under this aim, we will determine the mechanisms promoting HuR expression and TTP gene silencing in colon cancer. This study will enhance our understanding of colorectal cancer biology and lead to the identification of novel molecular targets, which will improve current treatment and prevention strategies. PUBLIC HEALTH RELEVANCE: Colorectal cancers are a leading cause of cancer incidence and death among adult Americans. In colorectal cancer cells and tumors, uncontrolled expression of many growth- and inflammation-associated genes occurs. By better understanding the cellular mechanisms involved in controlling the expression of these factors, we aim to identify and define new molecular targets for controlling gene expression in colorectal cancer and improve current treatment and prevention strategies.