Targeting c-Myc stability in c-Myc overexpressing large B-cell lymphoma

项目摘要 二次(DH)和三次(TH)淋巴瘤(L)是罕见的伴有弥漫性大B细胞的高度恶性B细胞淋巴瘤 (DLBCL)以涉及MYC的染色体易位共存为特征的形态学， BCL2和/或BCL6。双c-Myc(免疫组织化学检测为40%)和bcl2(免疫组化检测为50%)的DLBCL 没有易位的蛋白质过度表达(双表达或DEL)明显比 占DLBCL患者的20%~30%。淋巴瘤伴Del、DHL或THL 统称为c-Myc过表达的LBCL，与c-Myc相比，预后明显更差 MYC阴性患者[3年总存活率分别为30%和70%]。可怜的临床医生 这一亚组淋巴瘤患者的结果突出了对新的治疗策略的需要。换能器 β样蛋白1(TbL1X)最初被认为是一种特异性的接头蛋白，在 通过将β-连环蛋白募集到WNT靶标的启动子区域，如MYC和 CCND1激活它们的转录。少数已发表的报告表明，Wnt/β-catenin信号是 在DLBCL中被结构性激活，这促使我们对这种疾病进行了初步的研究。初步数据：我们的 已发表的研究表明，与正常的B细胞不同，DLBCL细胞表达丰富的TBL1。遗传 TBL1的缺失或用一流的小分子靶向药物替加韦(Iterion)进行药物治疗 TBL1在体内外均可诱导DLBCL细胞显著死亡。而tegavivint最初是作为一种 抑制TbL1/β-连环蛋白的相互作用，我们的数据表明，TbL1的基因缺失和 替加韦以转录后/β-连环蛋白非依赖的方式减少c-Myc蛋白表达。我们进一步 证明在DLBCL中，TBL1与Skp1/Cul1/F-Box(SCF)超复合体相互作用，该超复合体控制着 蛋白酶体介导的c-Myc和mTOR组分等关键促生存蛋白的降解 信令，如RHEB。总而言之，这些观察结果奠定了将TBL1作为一部小说的理论基础 促进c-Myc周转和干扰由其在c-Myc中的活动协调的驱动事件的治疗策略 MYC过表达LBCL。项目假设：TBL1是c-Myc周转的关键调节因子 代表了一种新的和有吸引力的靶向治疗c-Myc过表达的LBCL患者的候选方案。 为了验证这一假设，我们提出了以下目标：目标1：表征TBL1/c-Myc前馈 促进c-Myc高表达LBCL细胞存活的电路。目标2：启动单一药物的Ib期试验 替加韦治疗复发/难治性cMyc过表达的LBCL患者。目标3：确定组合 最大限度地发挥替加韦治疗潜力的策略。在这个项目完成后，我们将有一个更好的 了解调控c-Myc周转的TBL1调节机制将有 开发了一种新的治疗策略来治疗这种不治之症，并将开始描述 替加维特的耐药机制。

Project Summary Double (DH) and triple-hit (TH) lymphomas (L) are rare high grade B-cell lymphomas with diffuse large B-cell (DLBCL) morphology characterized by the co-occurrence of chromosomal translocations involving MYC, BCL2, and/or BCL6. DLBCLs with dual c-Myc (>40% by immunohistochemistry, IHC) and BCL2 (>50% by IHC) protein overexpression without translocation (double-expressor or DEL) are significantly more common than DH/THL, accounting for 20% to 30% of DLBCL patients. Lymphoma with either DEL, DHL, or THL are here collectively called c-Myc overexpressing LBCL and have a significantly worse prognosis compared to the c- Myc-negative counterpart [3-year overall survival of ~30% versus 70%, respectively]. The poor clinical outcome of this subset of lymphoma patients highlights the need for novel therapeutic strategies. Transducin β-like protein 1 (TBL1X) was initially identified as a specific adaptor protein playing an essential role in canonical Wnt signaling by recruiting β-catenin to the promoter region of Wnt targets such as MYC and CCND1 to activate their transcription. Few published reports indicate that the Wnt/β-catenin signaling is constitutively activated in DLBCL, which prompted our initial investigation in this disease. Preliminary data: Our published work shows that, unlike normal B cells, DLBCL cells express abundant levels of TBL1. Genetic deletion of TBL1 or pharmacologic treatment with tegavivint (Iterion), a first-in-class small molecule targeting TBL1, induces significant DLBCL cell death in vitro and in vivo. While tegavivint was initially developed as an inhibitor of the TBL1/β-catenin interaction, our data show that genetic deletion of TBL1 and treatment with tegavivint reduce c-Myc protein expression in a post-transcriptional/β-catenin independent manner. We further show that in DLBCL, TBL1 interacts with a Skp1/Cul1/F-Box (SCF) supercomplex, which controls the proteasome-mediated degradation of critical pro-survival proteins such as c-Myc and components of mTOR signaling such as Rheb. Collectively, these observations establish the rationale for targeting TBL1 as a novel therapeutic strategy to promote c-Myc turnover and to disrupt the driver events coordinated by its activity in c- Myc overexpressing LBCL. Project hypothesis: TBL1 serves as a critical modulator of c-Myc turnover and represents a novel and attractive candidate for targeted therapy for patients with c-Myc overexpressing LBCL. To test this hypothesis, we propose the following aims: Aim 1: Characterize the TBL1/c-Myc feedforward circuit promoting c-Myc overexpressing LBCL cell survival. Aim 2: Initiate a Phase Ib trial with single agent tegavivint in patients with relapsed/refractory cMyc overexpressing LBCL. Aim 3: Identify combination strategies to maximize the therapeutic potential of tegavivint. At completion of this project, we will have a better understanding of the TBL1-modulated mechanism through which c-Myc turnover is regulated, will have developed a novel therapeutic strategy to treat this incurable disease, and will have begun to characterize resistance mechanisms to tegavivint.