Tracing the origins of chromosomal translocations in prostate cancer

描述（由申请人提供）：染色体易位是癌症进展的标志。这些易位通常导致基因融合，这是致癌基因激活的一种常见机制。直到最近，复发性基因融合主要与血液恶性肿瘤（白血病和淋巴瘤）和软组织肿瘤（肉瘤）相关，但很少与常见上皮癌相关。这种观点随着ETS家族基因在前列腺癌中复发性基因融合的发现而改变。在ETS家族基因融合中，涉及雄激素调节基因TMPRSS2的5'非翻译区与ERG基因的TMPRSS2-ERG融合是最常见的，在大约50%的前列腺癌中发现。下一代基于测序方法的发展，如RNA-Seq和成对端全基因组测序，加速了前列腺癌基因融合的发现。然而，染色体易位的形成机制和细胞类型特异性尚不清楚。我们的建议旨在弥合染色体易位的快速发现和我们对导致其形成的机制的有限理解之间的差距。在我们最近的研究中，我们证明雄激素信号诱导TMPRSS2和ERG位点之间的染色体接近，并在受到导致DNA双链断裂的药物时促进TMPRSS2-ERG基因融合的形成。这些结果为人类前列腺癌基因融合的发生提供了一个概念框架。在具体目标1中，我们建议采用下一代测序来鉴定雄激素信号介导的全基因组染色体相互作用。导师在吞吐量技术方面的专业知识将帮助候选人获得完成目标1所需的技能。有趣的是，我们在雄激素受体AR协同因子FOXA1中发现了新的复发突变，在147例前列腺癌中有5例（3.4%）发生突变。对一个代表性突变的初步功能研究表明，突变的FOXA1破坏雄激素信号传导并增加增殖。在具体的目标2中，我们提出研究FOXA1突变在调节AR信号和相互作用中的作用。目标2，目标1的逻辑扩展将在独立阶段（R00）进行。完成这两个目标将使我们全面了解前列腺细胞的三维基因组结构，AR如何调节这种结构，AR协同因子的影响突变，以及重要的是这如何影响基因融合的形成。虽然空间接近是染色体易位的必要条件，但这还不够。DNA断裂与空间接近协同作用，促进染色体易位。在具体目标3中，我们将研究炎症介导的NF-kB通路激活在前列腺癌DNA断裂和ETS基因融合形成中的作用。成功完成本提案中概述的目标将提高我们对前列腺癌染色体易位起源的理解，可能对理解和治疗癌症具有更广泛的意义，并可能为人类前列腺癌的一般病因提供建议。这些项目都是基于我最初的想法构思出来的。Chinnaiyan博士对我的职业目标给予了全力支持，并鼓励我在未来将这些项目带到我的独立实验室。

DESCRIPTION (provided by applicant): Chromosomal translocations are a hallmark of cancer progression. These translocations often result in gene fusions, a common mechanism for oncogene activation. Until recently, recurrent gene fusions were predominantly associated with hematological malignancies (leukemias and lymphomas) and soft tissue tumors (sarcomas), but were rarely linked to common epithelial carcinomas. This view changed with the discovery of recurrent gene fusions involving ETS family genes in prostate cancer. Among the ETS family gene fusions, the TMPRSS2-ERG fusions involving the 5'untranslated region of androgen-regulated gene TMPRSS2 with the ERG gene are the most common and found in approximately 50% of prostate cancers. The development of next generation sequencing based approaches like RNA-Seq and paired-end whole-genome sequencing have accelerated the discoveries of gene fusions in prostate cancer. However, the mechanisms underlying the formation and cell type specificities of chromosomal translocations are far from clear. Our proposal aims to bridge the gap between the rapid discovery of chromosomal translocations and our limited understanding of the mechanisms leading to their formation. In our recent study, we demonstrate that androgen signaling induces chromosomal proximity between TMPRSS2 and ERG loci, and facilitates the formation of the TMPRSS2-ERG gene fusion when subjected to an agent that causes DNA double strand breaks. These results provide a conceptual framework for the genesis of gene fusions in human prostate cancer. In specific aim 1, we propose to employ next-generation sequencing to identify genome-wide chromosomal interactions mediated by androgen signaling. The mentor's expertise in throughput technologies will help the candidate acquire the necessary skill-set to accomplish aim 1. Interestingly, we identified novel recurrent mutations in the androgen receptor AR collaborating factor FOXA1, which is mutated in 5 of 147 (3.4%) prostate cancers. Preliminary functional studies on one representative mutation revealed that mutated FOXA1 disrupts androgen signaling and increases proliferation. In specific aim 2, we propose to study the effect of FOXA1 mutations in regulating AR signaling and interactome. Aim 2, a logical extension of aim 1 will be pursued during the independent phase (R00). Accomplishment of these two aims will provide us with a comprehensive understanding of the three dimensional genomic architecture of prostatic cells, how AR regulates this architecture, the influence mutations in AR collaborating factors, and importantly how this impacts the formation of gene fusions. While spatial proximity is necessary for chromosomal translocations, it is not sufficient. DNA breaks synergize with spatial proximity to fuel chromosomal translocations. In specific aim 3, we will study the role of inflammation mediated activation of NF-kB pathway in the formation of DNA breaks and ETS gene fusions in prostate cancer. Successful completion of the aims outlined in this proposal will improve our understanding of the origins of chromosomal translocations in prostate cancer, may have broader implications for understanding and treating cancer and may provide suggestions as to the general etiology of human prostate cancer. These projects have been conceived based on my original ideas. Dr. Chinnaiyan has extended his full support towards my career goals and has encouraged me to take these projects to my independent lab in the future. PUBLIC HEALTH RELEVANCE: Chromosomal translocations are a hallmark of cancer progression. However, the mechanisms underlying their formation in cancer tissues are not clear. The central objective of this proposal is to understand the mechanistic basis of chromosomal translocations.