Chromatin remodeling and FOXO in targeting CDK4 in mantle cell lymphoma

套细胞淋巴瘤(MCL)是一种B细胞性非霍奇金淋巴瘤(NHL)，由于 耐药性的发展。MCL的疾病进展总是与无拘无束有关 CDK4活性异常和细胞周期蛋白D1表达异常导致肿瘤细胞增殖。瞄准 因此，CDK4是一种合理的MCL治疗方法。针对CDK4与帕金森病的第一阶段临床试验 0332991(帕波西利，第一种选择性CDK4/6抑制剂)治疗复发的MCL可获得持久的临床疗效 部分MCL患者的肿瘤消退反应。因此，抑制CDK4不仅可以防止 这不仅增加了癌细胞的增殖能力，而且也增强了它们的脆弱性。正在进行的联合帕波西利的临床试验 使用Bortezomib或ibrutinib，抑制MCL生存所需的BTK，支持临床疗效 靶向CDK4。全转录组测序和全eXom的纵向综合分析 测序进一步显示，抑制CDK4导致所有患者的早期G1期停滞(PG1)延长，但 临床反应与参与PI3K失活的基因的不同调控有关， 新陈代谢和氧化还原压力。为了解决潜在的机制，我们发现pG1诱导了 组蛋白甲基转移酶EZH1和EZH2的差异调节抑制染色质重塑 H3K27me2/3，在应答患者中，及时抑制EZH1/EZH2导致协同杀伤MCL细胞 在pG1中。这些结果表明染色质重塑是pG1重编程的关键近端事件。 此外，pg1使MCL细胞对伊布鲁替尼的杀伤和对PI3K的抑制敏感，这需要作用 FOXO1转录因子，它被激活并定位于pG1的细胞核。Foxo1是一个中心 PI3K信号的组成部分，并以上下文依赖的方式发挥肿瘤抑制因子的作用。基座 根据我们新的初步发现，我们假设CDK4抑制诱导pG1导致特定的 表观遗传学改变改变FOXO1的S获得其目标基因，这反过来又改变了FOXO1的表达 依赖Foxo1的细胞毒基因对靶向CDK4的MCL的临床反应。我们的目标是前进 通过定义细胞周期的机制进行假设驱动的、有效的、持久的癌症细胞周期治疗 重新编程。为了实现这一目标，我们将在两个具体目标中检验我们的假设：1)阐明 EZH1和EZH2在染色质重塑中的作用 PG1转录重编程中的重塑和细胞周期功能的决定 调控EZH1/EZH2；以及2)确定FOXO1在CDK4抑制剂对BTK或 通过确定FOXO1对细胞周期调节的意义和鉴定其对PI3K的抑制 FOXO1介导pG1对临床反应增敏的转录靶点。成功完成 应有助于阐明染色质重塑和细胞周期调控的机制。 FOXO激活，具有重要而广泛的临床意义。

Mantle cell lymphoma (MCL) is a B cell non-Hodgkin lymphoma (NHL) that remains largely incurable due to development of drug resistance. Disease progression in MCL is invariably associated with unrestrained proliferation of tumor cells caused by dysregulated CDK4 activity and aberrant cyclin D1 expression. Targeting CDK4, therefore, is a rational approach to MCL therapy. The first phase I clinical trial targeting CDK4 with PD 0332991 (palbociclib, the first selective CDK4/6 inhibitor) in recurrent MCL resulted in durable clinical responses with tumor regression in some MCL patients. Inhibition of CDK4, therefore, not only prevents proliferation of cancer cells but also enhances their vulnerability. Ongoing clinical trials combining palbociclib with bortezomib or with ibrutinib, which inhibits BTK required for MCL survival, support the clinical efficacy of targeting CDK4. Longitudinal integrative analysis of whole transcriptome–sequencing and whole exom- sequencing further reveals that inhibition of CDK4 leads to prolonged early G1 arrest (pG1) in all patients but clinical response is associated with differential regulation of genes that are involved in PI3K inactivation, metabolism and redox stress. To address the underlying mechanism, we discovered that pG1 induced repressive chromatin remodeling by differential regulation of EZH1 and EZH2, histone methyltransferases for H3K27me2/3, in responding patients, and timely inhibition of EZH1/EZH2 led to synergistic killing of MCL cells in pG1. These results suggest that chromatin remodeling is a critical proximal event in pG1 reprogramming. Moreover, pG1 sensitizes MCL cells to killing by ibrutinib and by inhibition of PI3K, and this requires the action of the FOXO1 transcription factor, which is activated and localized to the nucleus in pG1. FOXO1 is a central component of the PI3K signaling and also acts as a tumor suppressor in a context-dependent manner. Based on our novel preliminary findings, we hypothesize that induction of pG1 by CDK4 inhibition causes specific epigenetic alterations that modify FOXO1's access to its target genes, which in turn alters the expression of FOXO1-dependent cytotoxic genes for clinical response to targeting CDK4 in MCL. Our goal is to advance hypothesis-driven, effective and durable cell cycle therapy in cancer by defining the mechanisms of cell cycle reprogramming. To achieve this goal, we will test our hypothesis in two Specific Aims: 1) To elucidate the role of EZH1 and EZH2 in chromatin remodeling in pG1 reprogramming by elucidate chromatin remodeling in pG1 transcriptional reprogramming and determining the functional consequence of cell cycle regulation of EZH1/EZH2; and 2) To define the role of FOXO1 in CDK4 inhibitor sensitization to BTK or PI3K inhibition by determine the significance of cell cycle regulation of FOXO1 and identifying the transcriptional targets of FOXO1 that mediates pG1 sensitization to clinical response. Successful completion of the proposed studies should shed light on the mechanism of cell cycle control of chromatin remodeling and FOXO activation, which has important and broad clinical implications.