MicroRNAs and chromosome 22q in the colon

描述（由申请人提供）：结直肠癌（CRC）已经成为一个独特的平台，不仅在这个领域，而且扩展到其他疾病状态，在分子发病机制、化学预防、诊断和治疗方面取得了持久的见解和进展。通过对关键基因和分子途径的鉴定，促进了对结直肠癌这些综合方面的阐明。人们普遍认为，大多数散发性结直肠癌具有染色体不稳定性途径，涉及关键肿瘤抑制基因（APC和p53，但也包括SMAD4）和癌基因（尤其是Ras，但也包括EGFR， c-myc, B-Raf）及其下游效应物的改变。散发性结肠癌的一个子集经历微卫星不稳定性（MSI）途径，通常是右侧的B-Raf突变，但没有Ras突变。最近，有人主张某些结直肠癌具有高甲基化的特征。我们已经在22q13.31染色体上绘制了一个杂合性缺失（LOH）区域的遗传和物理图谱，作为了解新基因在结直肠癌（和其他癌症）发生中的作用的基础。我们现在已经发现了LOH的一个新的端粒区，其中包含两个microrna，即Let-7a3和Let-7b，这些microrna在高达40%的结直肠癌中下调。MicroRNAs在发育、分化、增殖和癌症中发挥着关键的、多样化的作用，这些作用是通过信使rna降解或干扰翻译而实现的。我们假设Let-7a3和Let-7b microrna在结直肠癌的进展中起作用，这可能通过靶向Ras癌基因和c-myc癌基因来实现。这一新颖的假设将被以下相关的具体目标所追求：(1)。确定Let-7a3和Let-7b microrna在结直肠癌中的作用。A.确定这些microrna与临床参数和分子参数的关系；B.通过对Let7a和Let7b microrna的遗传/过表达/敲低研究，确定它们在结直肠癌发生中的功能，并确定它们对结肠癌发生和发展的关键特征——细胞增殖、凋亡、迁移和侵袭的影响。(2)。确定Ras和c-myc癌基因是否代表Let-7a3和Let- 7b的靶标。这将通过在遗传学方法设置中检查Ras转录和蛋白质活性来实现，即Let-7a3和Let-7b过表达/敲低。(3)确定体内恢复和抑制Let-7a3和Let-7b在结肠癌细胞中的功能后果。这将通过创新的三维器官型培养来评估，模拟结肠癌微环境，在胸腺中，通过肿瘤生长的生物发光照射裸鼠。总的来说，我们的研究有办法揭示结肠癌中由Let-7a3和Let-7b microrna调控Ras和c-myc癌基因的新途径，特别是在散发性结直肠癌（染色体不稳定性途径）中没有Ras突变。公共卫生相关性：结直肠癌（CRC）作为研究基本机制和转化为新的化学预防、诊断和治疗策略的范例。CRC的潜在发病机制可能涉及Let-7a3和Let-7b microrna，它们通常是正常细胞过程向恶性转化的关键调节因子。我们的研究希望揭示结直肠癌发病机制的新范式，并为利用这些知识开发新的诊断和治疗方法提供机会。

DESCRIPTION (provided by applicant): Colorectal cancer (CRC) has served as a unique platform for durable insights into and advances in molecular pathogenesis, chemoprevention, diagnosis, and therapy, not only in this venue but expanded into other disease states. The elucidation of these comprehensive aspects of CRC has been facilitated through the identification of key genes and molecular pathways. It is well accepted that the majority of sporadic colorectal cancers feature the chromosomal instability pathway, involving alterations in key tumor suppressor genes (APC and p53, but also SMAD4) and oncogenes (especially Ras, but also EGFR, c-myc, B-Raf) and their downstream effectors. A subset of sporadic colon cancers undergo microsatellite instability (MSI) pathway, typically right-sided with B-Raf mutations but without Ras mutations. Recently, it has been advocated that certain colorectal cancers feature hypermethylation. We have genetically and physically mapped a region of loss of heterozygosity (LOH) on chromosome 22q13.31 as a basis to understand the role of new genes in colorectal carcinogenesis (and other cancers). We now have discovered a new telomeric region of LOH, which harbors two microRNAs, namely Let-7a3 and Let-7b, and these microRNAs are downregulated in up to 40% of colorectal cancers. MicroRNAs have become increasingly recognized for their pivotal, diverse roles in development, differentiation, proliferation, and cancer, which is achieved the degradation or interference with translation with messenger RNAs. We hypothesize that the Let-7a3 and Let-7b microRNAs are instrumental in colorectal cancer progression, and this may be achieved by targeting the Ras oncogene, and also, the c-myc oncogene. This novel hypothesis will be pursued by the following interrelated Specific Aims: (1). To identify the roles of the Let-7a3 and Let-7b microRNAs in colorectal cancer. A. To determine the relationship between these microRNAs and clinical parameters and molecular parameters; B. To determine the function(s) of Let7a and Let7b in colorectal carcinogenesis through genetic /overexpression/knockdown studies of these microRNAs with determination of effects upon cellular proliferation, apoptosis, migration and invasion, which are critical features of the colon cancer initiation and progression. (2). To determine if the Ras and c-myc oncogenes represent targets of Let-7a3 and Let- 7b. This will be achieved through examination of Ras transcriptional and protein activities in the setting of genetic approaches, namely Let-7a3 and Let-7b overexpression/knockdown. (3) To determine the functional consequences of restoration and inhibition of Let-7a3 and Let-7b in colon cancer cells in vivo. This will be assessed by innovative three-dimensional organotypic cultures, which mimic the colon cancer microenvironment, and in athymic, irradiated nude mice through bioluminescence of tumor growth. In aggregate, our studies have the means to unravel new pathways of regulation of the Ras and c-myc oncogenes by the Let-7a3 and Let-7b microRNAs in colon cancer, especially where sporadic colorectal cancers (chromosomal instability pathway) do not harbor Ras mutations. PUBLIC HEALTH RELEVANCE: Colorectal cancer (CRC) serves as a paradigm for the investigation of basic mechanisms and translation into novel chemopreventive, diagnostic and therapeutic strategies. The underlying pathogenesis of CRC may involve the Let-7a3 and Let-7b microRNAs, which in general are critical regulators of normal cellular processes to malignant transformation. Our studies hope to reveal new paradigms in CRC pathogenesis, and offer opportunities for exploiting this knowledge in novel diagnostics and therapeutics.