Transcriptional Control of Cellular Survival and Proliferation in KSHV-transformed B Cells

摘要 卡波西肉瘤相关疱疹病毒(KSHV)是艾滋病毒/艾滋病背景下癌症的主要原因。我们 最近发现KSHV转化的原发渗出性淋巴瘤(PEL)细胞株表现出强烈的需求 对于细胞淋巴转录因子IRF4。这一发现将PEL归入一种新兴的血型 IRF4是关键致癌驱动因素的癌症。对IRF4致癌作用的详细了解还没有 已经在这些癌症中的任何一个中实现了，但有证据表明IRF4作为主要转录因子发挥作用 诱导广泛的表观遗传和转录重编程的因子。在PEL中，IRF4是必需的 MYC癌基因的过表达，但KSHV如何控制IRF4，IRF4的分子机制 调节MYC，IRF4是仅通过MYC发挥作用，还是具有额外的致癌作用尚不清楚。这个 这项建议的长期目标是确定作为致癌作用基础的下游影响。 IRF4在PEL中的应用，并利用我们的结果开发新的治疗策略。这一点的中心假设是 有人提出，KSHV诱导的、依赖IRF4的致癌基因转录重编程是肿瘤所必需的 PEL中细胞的存活和增殖。这一假设是以我们广泛的前期工作为前提的，这些工作已经 鉴定了KSHV编码的转录因子和细胞转录因子，它们控制着PEL中IRF4的表达和功能。 在ChIP-Seq和mRNA-Seq实验的基础上，我们特别假设IRF4及其病毒 和细胞共因子，与启动子和远端顺式调节元件相关联，推动IRF4依赖 致癌转录程序，其中包括沉默“有毒”的肿瘤抑制因子和 包括MYC在内的几个基本生存基因的过度表达，但也有其他的。为了检验我们的假设，我们 提出两个具体目标，即我们将：(1)确定哪些有毒基因必须被IRF4沉默以促进 PEL细胞的活性和增殖，以及(2)确定哪些受IRF4刺激的基因是必不可少的IRF4效应器 在PEL细胞中。已经确定的IRF4效应器的几个候选药物是高可信的药物靶点。我们 因此，我们将利用我们的结果，在体外和体内识别和测试新的治疗策略。 这项工作使用了一种将假设驱动的实验与无偏泛函相结合的尖端方法 基因组学方法。这项拟议的研究是创新的，因为转录的致癌结果 在KSHV相关恶性肿瘤的背景下重新编程尚未被研究。建议的工作是 意义重大，因为它将揭示IRF4在KSHV介导的B细胞增殖和生存中的致癌作用。 此外，结果将有助于我们理解IRF4在B细胞生物学中的作用以及它在几个 恶性血液病。结果将是有影响的，因为我们对IRF4依赖性的研究是意料之中的 以改进这种不治之症的治疗干预策略。

SUMMARY Kaposi’s sarcoma-associated herpesvirus (KSHV) is a major cause of cancer in the context of HIV/AIDS. We recently showed that KSHV-transformed primary effusion lymphoma (PEL) cell lines exhibit a strong requirement for the cellular lymphoid transcription factor IRF4. This finding places PEL into an emerging group of blood cancers where IRF4 is a key oncogenic driver. A detailed understanding of the oncogenic roles of IRF4 has not been achieved in any of these cancers, but evidence suggests that IRF4 functions as a master transcription factor that induces extensive epigenetic and transcriptional reprogramming. In PEL, IRF4 is required for overexpression of the MYC oncogene, but how KSHV controls IRF4, the molecular mechanism by which IRF4 regulates MYC, and whether IRF4 acts solely through MYC or has additional oncogenic roles is unknown. The long-term objective of this proposal is to determine the downstream effects that underlie the oncogenic roles of IRF4 in PEL and to use our results to develop novel therapeutic strategies. The central hypothesis of this proposal is that KSHV-induced, IRF4-dependent oncogenic transcriptional reprogramming is required for tumor cell survival and proliferation in PEL. This hypothesis is premised on our extensive preliminary work, which has identified both KSHV-encoded and cellular transcription factors that control IRF4 expression and function in PEL. Based on ChIP-Seq and mRNA-Seq experiments, we specifically hypothesize that IRF4, together with its viral and cellular co-factors, associates with promoters and distal cis-regulatory elements to drive an IRF4-dependent oncogenic transcription program, which involves both the silencing of “toxic” tumor suppressors and the overexpression of several essential survival genes, including MYC, but also others. To test our hypothesis, we propose two Specific Aims, i.e. we will: (1) determine which toxic genes must be silenced by IRF4 to promote PEL cell viability and proliferation, and (2) determine which IRF4-stimulated genes are essential IRF4 effectors in PEL cells. Several of the already identified candidates for IRF4 effectors are high-confidence drug targets. We will therefore exploit our results in both aims to identify and test novel therapeutic strategies, in vitro and in vivo. This work uses a cutting-edge approach that integrates hypothesis-driven experiments with unbiased functional genomics approaches. The proposed study is innovative, because the oncogenic outcome of transcriptional reprogramming in the context of KSHV-associated malignancies has not been studied. The proposed work is significant, because it will uncover oncogenic roles of IRF4 in KSHV-mediated B cell proliferation and survival. In addition, results will inform our understanding of IRF4 in B cell biology and its oncogenic role in several hematopoietic malignancies. Results will be impactful, because our studies of IRF4 dependency are expected to result in improved strategies for therapeutic intervention in this incurable cancer.