Epigenetic modulation of lung cancer metastasis by a novel long intergenic RNA

描述（由申请人提供）：胸部恶性肿瘤导致的死亡人数超过前列腺癌、乳腺癌和结直肠癌的总和。最常见的肺癌亚型是肺腺癌（LUAD），其起始于外周气道并可迅速扩散至其他重要器官。目前还没有有效的治疗转移性LUAD，这是生物学和遗传多样性。此外，最近的基因组重新测序工作揭示了数千个新的人类基因位点，尽管这些基因位点不编码任何蛋白质，但可能对人类医学至关重要。鉴于LUAD的异质性和遗传复杂性，需要多学科的方法来了解肺癌转移的分子发病机制，并发现这种疾病的新介质和生物标志物。 通过计算和实验方法，我们检查了细胞分化状态、肺癌亚型和临床结果之间的分子关系，以发现细胞谱系限制性基因在转移性LUAD中的作用。这些改变包括功能未知的新型长基因间非编码RNA（lincRNA）转录的变化。特别是，我们鉴定了一种lincRNA，在此称为linc-XIM（X连锁转移抑制剂），作为转移的潜在抑制剂和表观遗传异常的生物标志物，特别是在人LUAD中。我们证实linc-XIM通过拮抗Polycomb阻遏复合物2（PRC 2）的活性和/或其向相关基因组靶标的募集来抑制转移。因此，linc-XIM的抑制可以通过表观遗传学重编程惰性LUAD细胞的转录组来增强LUAD的转移能力。 我们将通过首先使用我们建立的人LUAD细胞转移性传播和定殖的体内模型表征linc-XIM在肺LUAD分化、肿瘤生长和远处器官转移期间的生物学功能来测试该假设。我们将采用遗传和药理学方法，使暂时控制的增益和功能的损失，建立linc-XIM表达和PRC 2活性之间的功能关联。在这些生物学实验的同时，我们将结合联合收割机分子、生物化学和原位技术来阐明linc-XIM隔离或抑制PRC 2蛋白亚基并最终调节表观遗传沉默的机制。最后，我们将检查人类LUAD生物标本中linc-XIM、PRC 2亚基、PRC 2靶基因的表达与临床结果之间的相关性。因此，我们申请的总体目标可能为组织特异性lincRNA在癌症进展中的作用提供新的线索，并为有转移性疾病风险的肺癌患者提供更有效的表观遗传疗法的见解。

DESCRIPTION (provided by applicant): Thoracic malignancies account for more deaths than prostate, breast and colorectal cancer combined. The most frequent lung cancer subtype is lung adenocarcinoma (LUAD), which is initiated in the peripheral airways and can disseminate rapidly to other vital organs. There are currently no effective therapeutics for metastatic LUAD, which are biologically and genetically diverse. In addition, recent genomic re-sequencing efforts have revealed thousands of new human gene loci that, despite not coding for any proteins, may be critical to human medicine. Given the heterogeneity and genetic complexity of LUADs, a multi-disciplinary approach is needed to understand the molecular pathogenesis of lung cancer metastasis and uncover novel mediators and biomarkers of this disease. Through computational and experimental approaches, we examined the molecular relationship between cell differentiation states, lung cancer subtypes, and clinical outcome, to discover a role for cel lineage- restricted genes in metastatic LUAD. These alterations include changes in the transcription of novel long intergenic non-coding RNAs (lincRNAs) with unknown function. In particular, we identified one lincRNA, referred to here as linc-XIM (X-linked inhibitor of metastasis), as a potential suppressor of metastasis and biomarker of epigenetic abnormalities specifically in human LUADs. We posit that linc-XIM inhibits metastasis by antagonizing the activity of the Polycomb repressor complex 2 (PRC2) and/or its recruitment to relevant genomic targets. Thus, repression of linc-XIM may enhance metastatic competence of LUADs by epigenetically reprogramming the transcriptome of indolent LUAD cells. We will test this hypothesis by first characterizing the biological function(s) of linc-XIM during lung LUAD differentiation, tumor growth and distant organ metastasis, using our established in vivo model of metastatic dissemination and colonization by human LUAD cells. We will employ genetic and pharmacological approaches that enable temporally controlled gain and loss of function, to establish the functional association between linc-XIM expression and PRC2 activity. In parallel to these biological experiments, we will combine molecular, biochemical, and in situ techniques to elucidate the mechanism by which linc-XIM sequesters or inhibits PRC2 protein subunits and ultimately regulates epigenetic silencing. Finally, we will examine the correlation between the expression of linc-XIM, PRC2 subunits, PRC2 target genes, and clinical outcome in human LUAD biospecimens. The overall goal of our application may therefore shed new light into the role of tissue specific lincRNAs in cancer progression, and provide insights into more effective epigenetic therapies for lung cancer patients at risk for metastatic disease.