Delineating ARF negative regulation of PAF1C-dependent oncogenic programs

项目总结 肿瘤抑制因子(TS)通过在多个水平上的作用来调节细胞生长和死亡的平衡。放松管制 这些等级中的任何一个都可以促进肿瘤的发生，影响癌症患者的生存和应对目前 可用的治疗方法。因此，对这些过程有了更好的理解和对小说的认同 针对TS丢失的治疗靶点是癌症生物学领域的优先事项。几十年的工作已经定义了 P14ARF(另类阅读框架)TS以P53依赖的方式工作，以防止肿瘤发生。 然而，ARF也以一种P53独立的方式运作，以潜在地“备份P53”，但其机制 人们对此仍然知之甚少。该领域有了一个重新获得的想法，即深入研究肿瘤抑制机制和 利用基础生物学来获得治疗机会。在此背景下，这项研究提案的主要目标是 是定义ARF(在p53丢失时重新激活)如何发挥抑制肿瘤促进剂计划的作用。我们未出版的 研究已经确定了一个以前被忽视的ARF肿瘤抑制机制。首先，在p53丢失的情况下， 重新激活的ARF选择性地针对编码基因的聚合酶相关因子1复合体(PAF1C) 促生长的GDF和BMP配体抑制细胞的异常生长。第二，原发性p53中ARF的丢失-/- 细胞去抑制GDF/BMP程序导致Smad1/5磷酸化和靶基因激活 (“致癌GDF/SMAD轴”)，表明致癌易损性发生在双TS(p53和ARF)上 Lost作为替代治疗靶点出现。然而，目前尚不清楚ARF是如何使PAF1C在 以及致癌基因GDF/SMAD轴是否具有诊断和治疗价值。 这项小额拨款提案旨在解决ARF如何以特定于基因的方式使PAF1C失活 抑制肿瘤促进剂计划并评价靶向致癌基因的治疗价值 GDF/SMAD计划。本提案中的工作以这些先前的发现和知识中的关键差距为指导 为了检验ARF结合Paf1和基因特异性因子RUNX1以阻断PAF1C的中心假设 以基因特异的方式组装，从而抑制肿瘤启动子程序。要测试底层的 假设，我们将利用生化和遗传方法以及临床和分子注释 临床前模型。具体地说，我们将首先调查ARF如何绑定Paf1和RUNX1以阻止PAF1C 以基因特异性方式组装(目标1)，然后探测是否存在双TS(P53和ARF)缺失 展示致癌GDF/SMAD轴的重新激活并检查其治疗和诊断潜力(AIM 2)。总之，阐明了ARF负性调节PAF1C依赖的肿瘤促进剂的机制 转录程序将提高我们对一个重要的生物过程的理解，并提供替代方案 ARF和P53双重失活的癌症(如肉瘤、胰腺癌和 肺腺癌)，这与NCI的使命是一致的，即寻找新的目标来转移发现 从长凳到诊所。

PROJECT SUMMARY Tumor suppressors (TS) tune the balance of cell growth and death by acting at multiple levels. Deregulation of any of these hierarchies can promote tumorigenesis, impact cancer patient’s survival and response to currently available treatments. Therefore, having a better understanding of these processes and the identification of novel therapeutic targets upon TS loss is a priority in the field of cancer biology. Decades of work have defined how the p14ARF (Alternative Reading Frame) TS operates in a p53-dependent manner to prevent tumorigenesis. However, ARF also operates in a p53-independent manner to potentially “back-up p53”, but the mechanisms remain poorly understood. There is a regained idea in the field to delve into tumor suppressive mechanisms and to leverage the basic biology to therapeutic opportunities. In this context, the major goal of this research proposal is to define how ARF (reactivated upon p53 loss) functions to restrain tumor promoter programs. Our unpublished studies have defined a previously overlooked mechanism of ARF tumor suppression. First, upon p53 loss, reactivated ARF selectively targets the Polymerase Associated Factor 1 complex (PAF1C) at genes encoding the pro-growth GDF and BMP ligands to restrain abnormal cell growth. Second, loss of ARF in primary p53-/- cells de-repress GDF/BMP programs leading to SMAD1/5 phosphorylation and target gene activation (“oncogenic GDF/SMAD axis”), suggesting oncogenic vulnerabilities accrued upon double TS (p53 and ARF) loss emerge as alternative therapeutic targets. However, it remains unknown how ARF inactivates PAF1C in a gene-specific manner and whether the oncogenic GDF/SMAD axis has any diagnostic and therapeutic value. This small grant proposal aims at addressing how ARF inactivates PAF1C in a gene-specific manner to restrain tumor promoter programs and to evaluate the therapeutic value of targeting the oncogenic GDF/SMAD program. Work in this proposal is guided by these previous findings and critical gaps in knowledge to test the central hypothesis that ARF binds Paf1 and the gene-specific factor RUNX1 to block PAF1C assembly in a gene-specific manner thereby restraining tumor promoter programs. To test the underlying hypothesis, we will leverage biochemical and genetic approaches as well as clinically and molecularly annotated preclinical models. Specifically, we will first investigate how ARF binds Paf1 and RUNX1 to block PAF1C assembly in a gene-specific manner (Aim 1), and then probe if tumors bearing double TS (p53 and ARF) loss exhibit reactivation of the oncogenic GDF/SMAD axis and examine its therapeutic and diagnostic potential (Aim 2). Together, elucidating the mechanisms by which ARF negatively regulates PAF1C-dependent tumor promoter transcriptional programs will improve our understanding of an important biological process and offer alternative opportunities to target TS loss in cancers with dual ARF and p53 inactivation (such as sarcoma, pancreas, and lung adenocarcinoma), which is in-line with NCI’s mission to identify novel targets to move the discoveries from the bench to the clinics.