Chromatin remodeling and FOXO in targeting CDK4 in mantle cell lymphoma

套细胞淋巴瘤（MCL）是一种B细胞非霍奇金淋巴瘤（NHL），由于 耐药性的发展。MCL的疾病进展总是与不受限制的 CDK 4活性失调和细胞周期蛋白D1表达异常引起的肿瘤细胞增殖。靶向 因此，CDK 4是MCL治疗的合理方法。首个靶向CDK 4的I期临床试验 0332991（palbociclib，第一种选择性CDK 4/6抑制剂）在复发性MCL中产生了持久的临床疗效 一些MCL患者的肿瘤消退。因此，抑制CDK 4不仅可以防止 癌细胞的增殖，但也增加了他们的脆弱性。正在进行的与Palbociclib联合治疗的临床试验 与硼替佐米或伊曲替尼（抑制MCL存活所需的BTK）联合使用，支持 靶向CDK 4。全转录组测序和全外显子组测序的纵向整合分析 测序进一步揭示，CDK 4的抑制导致所有患者的早期G1期阻滞（pG 1）延长， 临床反应与参与PI 3 K失活的基因的差异调节有关， 代谢和氧化还原应激。为了解决潜在的机制，我们发现pG 1诱导了 通过EZH 1和EZH 2的差异调节抑制染色质重塑，组蛋白甲基转移酶 H3 K27 me 2/3，以及及时抑制EZH 1/EZH 2导致MCL细胞的协同杀伤 在pG 1中。这些结果表明，染色质重塑是一个关键的近端事件在pG 1重编程。 此外，pG 1使MCL细胞对伊鲁替尼的杀伤和PI 3 K的抑制敏感，这需要 FOXO 1转录因子，其在pG 1中被激活并定位于细胞核。FOXO 1是一个中心 它是PI 3 K信号传导的组成部分，也以上下文依赖性方式作为肿瘤抑制因子。基于 根据我们新的初步发现，我们假设通过CDK 4抑制诱导pG 1导致特异性的 表观遗传学改变，改变FOXO 1进入其靶基因的途径，这反过来又改变了 FOXO 1依赖性细胞毒性基因对MCL中靶向CDK 4的临床应答。我们的目标是 通过定义细胞周期机制，在癌症中进行假设驱动的、有效的和持久的细胞周期治疗 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 EZH 1和EZH 2在pG 1重编程中染色质重塑中的作用 pG 1转录重编程中的重构和决定细胞周期的功能后果 EZH 1/EZH 2的调节;和2）确定FOXO 1在CDK 4抑制剂对BTK或EZH 1/EZH 2的敏化中的作用。 通过测定FOXO 1对细胞周期调控的意义及鉴定PI 3 K抑制剂， FOXO 1的转录靶点，介导pG 1对临床反应的敏感性。成功完成 的拟议研究应该阐明染色质重塑的细胞周期控制机制， FOXO激活，具有重要和广泛的临床意义。

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.