Epigenetic Alterations and Targeted Therapies in North American ATLL

项目总结/摘要 成人T细胞白血病/淋巴瘤（ATLL）是一种恶性CD 4 + T细胞疾病，在人类T细胞中发展。 嗜淋巴细胞病毒-1（HTLV-1）携带者。3年总生存率只有可怜的25%， 最激进的化疗目前不存在改变结果的靶向治疗。因此改进的 迫切需要了解发病机制和新的治疗策略。我们和其他人已经证明 在日本（J-ATLL）和北美（NA-ATLL）患者中诊断的ATLL具有非常不同的 临床行为，北美变异的特点是化疗难治性疾病的发生率较高， 预后更差最近，我们对30名在我们的研究中发现的患者进行了首次靶向外显子测序分析。 中心，并发现控制表观遗传修饰的基因中有更多的突变， 在TCR/NF-κ B信号通路中的突变比日本的ATL更少。令人惊讶的是， 我们患者队列中的EP 300突变（20%）约为日本队列（5.7%）的4倍。一 在能被p300乙酰化的转录因子中，BCL 6是一种转录抑制因子， 成熟B和T细胞的许多功能方面。我们首次发现BCL 6表达于 在原代ATLL样品和ATLL细胞系中。有趣的是，NA-ATLL细胞系明显比 J-ATLL细胞系对BCL 6的抑制。另外的实验表明，在NA-ATLL细胞中，BCL 6起作用。 在S-期NA-ATLL细胞科普升高的DNA复制应激时， 细胞周期的阶段。支持S期是NA-ATLL细胞的阿基里斯之踵的概念，这些细胞 但J-ATLL细胞对PARP抑制剂奥拉帕尼并不敏感。这些发现支持了我们的 工作假设，失调的表观遗传程序是NA-ATLL生物学的中心特征， 减弱的p300活性结合BCL 6在S期程序中的独特作用提供了一个新的机会， 用于治疗靶向。提出了以下三个具体目标来检验这一假设。 目标1.阐明p300调控NA-ATLL染色质和基因表达的机制。 目标2.表征p300和BCL 6作为DNA复制程序和基因组稳定性的调节剂的作用 在NA-ATLL。 目标3.确定PARPi敏感性的机制基础，并设计治疗策略以靶向S- NA-ATLL的相位漏洞。

PROJECT SUMMARY/ABSTRACT Adult T-cell leukemia/lymphoma (ATLL) is a disease of malignant CD4+ T cells that develops in human T- lymphotropic virus-1 (HTLV-1) carriers. The 3-yr overall survival is an abysmal 25% even when managed with the most aggressive chemotherapy. No outcome-changing targeted treatment currently exists. Thus, improved understanding of pathogenesis and novel therapeutic strategies are urgently needed. We and others have shown that ATLLs diagnosed in the Japanese (J-ATLL) and North American (NA-ATLL) patients have very different clinical behavior, with the North American variant characterized by a higher rate of chemo-refractory disease and worse prognosis. Recently, we performed the first targeted exon sequencing analysis in 30 patients seen at our center and discovered significantly more mutations in genes controlling epigenetic modifications and fewer mutations in the TCR/NF-kappaB signaling pathways than the Japanese ATLLs. Strikingly, the frequency of EP300 mutations in our patient cohort (20%) was about 4 times that seen in the Japanese cohort (5.7%). One of the transcription factors that can be acetylated by p300 is BCL6, a transcription repressor that critically controls many functional aspects of mature B and T cells. We have discovered for the first time that BCL6 is expressed in primary ATLL samples and ATLL cell lines. Interestingly, NA-ATLL cell lines are notably more sensitive than J-ATLL cell lines to BCL6 inhibition. Additional experiments suggest that in NA-ATLL cells, BCL6 plays an essential role enabling survival of NA-ATLL cells as they cope with elevated DNA replication stress during S- phase of the cell cycle. Supporting the concept that the S-phase is an Achilles’ heel of NA-ATLL cells, these cells but not the J-ATLL cells are exquisitely sensitive to a PARP inhibitor, Olaparib. These findings support our working hypothesis that dysregulated epigenetic program is a central feature of NA-ATLL biology and that attenuated p300 activity combined with a unique role of BCL6 in S-phase programs provides a novel opportunity for therapeutic targeting. The following three specific aims are proposed to test this hypothesis. Aim 1. Elucidate the mechanisms by which p300 regulates chromatin and gene expression in NA-ATLL. Aim 2. Characterize the roles of p300 and BCL6 as regulators of DNA replication program and genome stability in NA-ATLL. Aim 3. Determine the mechanistic basis of PARPi sensitivity and design therapeutic strategies to target the S- phase vulnerabilities of NA-ATLL.