Identification of Novel Gene Regulatory Interactions Driving the Immune Evasion Program Through Transcriptional Activation of CD47 in Cancer

摘要：CD 47是一种细胞表面蛋白，几乎存在于每个细胞中，它与SIRPα相互作用， 巨噬细胞抑制吞噬作用。在癌细胞中，CD 47转录和蛋白表达异常， 上调，保护癌细胞不被巨噬细胞识别和清除。封锁 通过抗CD 47或抗SIRP α单克隆抗体（mAb）的CD 47-SIRPα信号传导增强巨噬细胞 吞噬多种癌症类型。由于该信息具有临床意义，因此至关重要 了解负责增加CD 47的确切机制和上游调节因子 在癌细胞中的表达，以开发新的疗法，靶向上游组的转录 白血病和实体瘤中CD 47的失调因子、遗传或表观遗传修饰，以及 这种方式防止恶性细胞逃避免疫监视。通过进行基因组顺式- 通过调控分析，我发现两种不同的超级增强子（SE）与某些癌症中的CD 47相关 而不是在健康的细胞中。我还发现了一组活性成分增强剂， 在两种CD 47 SE中的每一种内，调节不同癌细胞类型中的CD 47表达：而1） 上游CD 47成分增强子在T细胞淋巴母细胞白血病（T-ALL）细胞中有活性，2）下游CD 47成分增强子在T细胞淋巴母细胞白血病（T-ALL）细胞中有活性， CD 47成分增强子在乳腺癌（乳腺癌阳性亚型）中是活跃的，它对诱导 TNF-NFKB 1信号通路。相反，我的初步数据表明，CD 47上调， 白血病细胞系，是独立于这种炎症途径，并依赖于参与的途径， 在造血发育过程中。基于这些发现，我假设：在不同的癌症中， 类型，独特形成的远端增强子或超级增强子（SE），从转录因子中招募输入（转录因子）。 炎症和/或发育程序以失调免疫逃避靶基因（例如，CD 47）。这 该提案旨在研究其他机制（包括表观遗传变化和基因组修饰）， 单独或与TNF炎性途径组合特别被乳腺癌细胞使用， 白血病亚型通过错误调节CD 47启动免疫逃避反应。为了了解这些 将进行拟议的实验，癌症细胞与健康细胞的调节机制发生了改变 主要在患者来源的实体瘤（特别是乳腺癌）和白血病样本中;结果 将与健康供体样本的结果进行比较。就这项建议而言，将有以下具体目标： 进行：1）确定是否形成独特的CD 47超级增强子（SE）以响应于 炎症信号错误激活免疫逃避程序在乳腺癌阳性。 2)研究CD 47增强子或SE是否错误地募集输入（转录因子） 通常驱动造血发育，触发白血病细胞中CD 47的误激活。

ABSTRACT: CD47 is a cell surface protein, found virtually in every cell, which interacts with SIRPα on macrophages to inhibit phagocytosis. In cancer cells, CD47 transcript and protein expression is aberrantly upregulated, protecting the cancer cells from being recognized and cleared by macrophages. Blockade of CD47-SIRPα signaling by anti-CD47 or anti-SIRPα monoclonal antibodies (mAbs) enhances macrophage phagocytosis of a variety of cancer types. Due to the clinical implications this information has, it is critical to understand the precise mechanisms and upstream regulators responsible for increasing CD47 expression in cancer cells, to develop novel therapies to target the upstream group of transcription factors, genetic or epigenetic modifications that misregulate CD47 in leukemia and solid tumors, and in this manner, prevent malignant cells from evading immunosurveillance. By performing a genomic cis- regulatory analysis, I found that two distinct super-enhancers (SEs) are associated with CD47 in certain cancer cell types and not in their healthy counterparts. I also found that a set of active constituent enhancers, located within each of the two CD47 SEs, regulate CD47 expression in different cancer cell types: while 1) an upstream CD47 constituent enhancer is active in T-cell lymphoblastic leukemia (T-ALL) cells, 2) a downstream CD47 constituent enhancer is active in breast cancer (hormone-positive subtype), and it responds to induction of the TNF–NFKB1 signaling pathway. In contrast, my preliminary data suggests that CD47 upregulation in leukemia cell lines, is independent of this inflammatory pathway, and is dependent on pathways that are involved in hematopoietic developmental processes. Based on these findings, I hypothesize that: in different cancer types, uniquely formed distal enhancers or super-enhancers (SEs), recruit inputs (transcription factors) from the inflammatory and/or developmental program to dysregulate target genes of immune evasion (e.g, CD47). This proposal aims to investigate other mechanisms (including epigenetic changes and genomic modifications) that alone or in combination with the TNF inflammatory pathway are used particularly by breast cancer cells and leukemia subtypes to initiate an immune evasion response by misregulating CD47. To understand how these mechanisms of regulation are altered in cancer versus healthy cells, the proposed experiments will be carried out mainly in patient-derived solid tumors (specifically breast cancer) and leukemia samples; and the results will be compared with results from healthy donor samples. For this proposal, the following specific aims will be performed: 1) Determine whether unique CD47 super-enhancers (SEs) are formed to respond to inflammatory signaling to misactivate the immune evasion program in hormone-positive breast cancers. 2) Investigate whether CD47 enhancers or SEs are erroneously recruiting inputs (transcription factors) that typically drive hematopoiesis development, to trigger misactivation of CD47 in leukemia cells.