The LIN28b-Let7-IMP1 axis in colonic epithelial biology

项目摘要 肠上皮细胞沿着 隐窝-绒毛梯度正常的肠道内稳态在感染、炎症和炎症的状态下被扰乱， 恶性转化（腺瘤性息肉、结直肠癌）。散发性结直肠癌的发病机制 癌症涉及具有特征性基因组和遗传改变的不同途径。尽管取得了重大 利用我们对这些途径的理解进行诊断、预后和治疗的进展 尽管采取了各种治疗策略，但结直肠癌（CRC）仍然是癌症相关死亡率的主要原因。这表明， 特别需要确定和理解新的，治疗上易于处理的肠道稳态途径， 可以驱动CRC。我们的工作已经介绍并阐明了mRNA结合蛋白的新作用， 肠/结肠上皮稳态，以及包括过度增殖、代谢改变 和转变。LIN 28 B是一种mRNA结合蛋白，在胚胎干细胞中也很关键， 转录调节let-7 microRNA家族并导致分化抑制。反过来，Let-7 microRNA具有不同的mRNA靶点，包括IMP 1（Igf 2 mRNA结合蛋白-1），另一种mRNA结合蛋白， 蛋白我们已经证明LIN 28 B和IMP 1分别驱动肿瘤起始细胞表型 与它们在正常稳态期间调节增殖和分化的作用有关;然而， 目前尚不清楚LIN 28 B介导的过度增殖、分化改变和相关的肿瘤发生 需要IMP 1。此外，尚不清楚IMP 1的肿瘤促进或转移作用是否依赖于 这完全取决于LIN 28 B下游的Let-7对其的调节。我们对这一提议的总体假设是， LIN 28 B和IMP 1在转录后控制途径中起协同作用（一些已知） 与上皮细胞命运相关，这可能有利于恶性转化。我们将继续这个假设 通过以下相互关联的具体目标：目标1：评估LIN 28 B和 IMP 1在体内增殖、分化和恶性转化中的作用。目标2：确定和验证 通过RNA测序（“转录组”）由LIN 28 B和IMP 1介导的共同和不同途径， 核糖体分析（“translatome”）。目的3：评估IMP 1的Let-7依赖性调节，以促进 过度增殖和转移。

PROJECT SUMMARY The intestinal epithelium is in a dynamic equilibrium of proliferation, differentiation and apoptosis along the crypt-villus gradient. Normal intestinal homeostasis is disturbed during states of infection, inflammation and malignant transformation (adenomatous polyps, colorectal cancer). The pathogenesis of sporadic colorectal cancer involves distinct pathways with characteristic genomic and genetic alterations. Despite significant advances in leveraging our understanding of these pathways for diagnostic, prognostic, and therapeutic strategies, colorectal cancer (CRC) remains a leading cause of cancer-related mortality. This underscores a specific need to identify and understand novel, therapeutically tractable pathways in intestinal homeostasis that may drive CRC. Our work has introduced and elucidated the novel role of mRNA binding proteins in intestinal/colonic epithelial homeostasis, as well as aberrations including hyperproliferation, altered metabolism and transformation. LIN28B, an mRNA binding protein, also critical in embryonic stem cells, post- transcriptionally regulates the let-7 microRNA family and results in suppression of differentiation. In turn, Let-7 microRNAs have diverse mRNA targets, including IMP1 (Igf2 mRNA binding protein-1), another mRNA binding protein. We have demonstrated that LIN28B and IMP1 separately drive tumor-initiating cell phenotypes associated with their roles in regulating proliferation and differentiation during normal homeostasis; however, it remains unclear if LIN28B-mediated hyperproliferation, altered differentiation, and associated tumorigenesis requires IMP1. In addition, it remains unknown if the tumor promoting or metastatic roles of IMP1 depend entirely on its regulation by Let-7 downstream of LIN28B. Our overarching hypothesis of this proposal is that LIN28B and IMP1 comprise cooperative roles in controlling post-transcriptionally the pathways (some known) associated with epithelial cell fate, which may favor malignant transformation. We will pursue this hypothesis through the following interrelated Specific Aims: Aim 1: To evaluate the interdependence of LIN28B and IMP1 in proliferation, differentiation, and malignant transformation in vivo. Aim 2: To determine and validate common and divergent pathways mediated by LIN28B and IMP1 via RNA-Sequencing (“transcriptome”) and ribosome profiling (“translatome”) in vivo. Aim 3: To evaluate Let-7 dependent regulation of IMP1 to promote hyperproliferation and metastasis.