The cyclic AMP/phosphodiesterase4 axis regulates proximal B cell receptor signaling and offers a new therapeutic strategy for B cell lymphomas

 描述（由申请方提供）：B细胞受体（BCR）的异常激活是成熟B细胞肿瘤的新标志。BCR启动信号级联，激活多种激酶，包括SYK、BTK和PI 3 K δ，导致NF-κB、PI 3 K/AKT、RAS和MAPK通路的参与，从而促进B细胞的增殖/存活。考虑到这种促生长的结果，恶性B细胞为了它们的利益而劫持这种信号传导模块并不奇怪。因此，开发抑制BCR的疗法已成为高度优先事项，初步结果表明这是一种合理的方法。然而，这些新的治疗方法主要依赖于一次靶向一种激酶，并且很少诱导完全反应。此外，最近在接受BTK抑制剂伊布替尼治疗的患者中报告了BCR途径（BTK/PLCγ2）内的获得性突变和随后的临床应答丧失。此外，对诱导BCR活性终止的信号分子知之甚少。早期我们发现磷酸二酯酶4 B（PDE 4 B）在致死性弥漫性大B细胞淋巴瘤（DLBCL）中高度表达。随后，我们证明了PDE 4 B抑制导致环AMP（cAMP）介导的SYK、BTK和PI 3 K的抑制，这与淋巴瘤中的生长抑制有关。这些观察结果表明cAMP/PDE 4和BCR之间存在相互作用，当充分理解时，可以将观察结果发展为临床举措。在此，我们将检验以下假设：PDE 4抑制通过升高cAMP水平，抑制BCR的活性，从而抑制BCR依赖性激酶SYK、BTK和PI 3 K δ的活性。基于我们的初步数据，我们还计划测试cAMP/PDE 4轴通过激活脂质磷酸酶SHIP 1调节BCR，从而终止PI 3 K活性的想法。通过扩展，我们建议将PDE 4抑制剂与特异性靶向这些BCR相关激酶的药物组合将带来临床益处。我们认为，这种垂直靶向的方法将是协同的，并可能阻止来自单一药物策略的补偿机制，从而限制耐药性的出现。为了测试这些概念，我们将使用遗传修饰的DLBCL细胞系、Pde 4敲除小鼠、在我们组中产生的新的复合小鼠模型（其将Pde 4 b的纯合缺失与淋巴瘤原性Myc转基因等位基因组合）以及PDE 4、BTK和PI 3 K δ的临床级抑制剂。我们的具体目标是：1.在体外和体内确定cAMP/PDE 4轴在正常成熟B淋巴细胞和B细胞淋巴瘤中调节BCR活性的作用; 2.在体外和体内确定PDE 4和BCR依赖性激酶的组合靶向在人和鼠B细胞淋巴瘤中的作用。完成后，这项研究可能会确定cAMP作为介导的BCR信号终止，和PDE 4抑制作为一种新的方法来靶向异常的BCR信号通路。如果是肯定的，我们的数据将满足当代合理的治疗设计的原则之一，靶向一个关键的途径，BCR，与不同的药物类别，磷酸二酯酶和激酶抑制剂。

 DESCRIPTION (provided by applicant): Aberrant activation of the B cell receptor (BCR) is an emerging hallmark of mature B cell tumors. The BCR initiates a signaling cascade that activates multiple kinases, including SYK, BTK and PI3Kδ, leading to engagement of the NF-κB, PI3K/AKT, RAS and MAPK pathways, thus promoting proliferation/survival of B cells. Considering this pro-growth outcome, it is not surprising that malignant B cells hijack this signaling module for their benefit. Consequently, the development of therapies to inhibit the BCR has become a high priority and preliminary results suggest that this is a sound approach. However, these novel therapeutic approaches rely primarily on the targeting of one kinase at a time and only rarely induce complete responses. Moreover, acquired mutations within the BCR pathway (BTK/PLCγ2) and subsequent loss of clinical response have recently been reported in patients treated with the BTK inhibitor Ibrutinib. Moreover, little is known about the signaling molecules that induce the termination of BCR activity. Earlier we identified phosphodiesterase 4B (PDE4B) as a highly expressed gene in fatal diffuse large B cell lymphoma (DLBCL). Subsequently, we demonstrated that PDE4B inhibition leads to a cyclic-AMP (cAMP) mediated suppression of SYK, BTK and PI3K, which associates with growth inhibition in lymphoma. These observations suggested a cross-talk between cAMP/PDE4 and the BCR, an observation that when fully understood can be developed into clinical initiatives. Here, we will test the hypothesis that PDE4 inhibition, by elevating cAMP levels, suppresses the activity of the BCR and consequently that of BCR-dependent kinases SYK, BTK and PI3Kδ. Building on our preliminary data, we also plan to test the idea that the cAMP/PDE4 axis modulates the BCR via activation of of the lipid phosphatase SHIP1, thus terminating PI3K activity. By extension, we propose that combining PDE4 inhibitors with agents that specifically target these BCR-related kinases will impart clinical benefit. We suggest that this vertical targeting approach will be synergistic and may block compensatory mechanisms derived from single agent strategies, thus limiting the emergence of resistance. To test these concepts, we will use genetically modified DLBCL cell lines, a Pdeb4 knock-out mouse, a new composite mouse model generated in our group that combines homozygous loss of Pde4b with a lymphomagenic Myc transgenic allele, and clinical grade inhibitors of PDE4, BTK and PI3Kδ. Our specific aims are: 1. Define in vitro and in vivo the role of the cAMP/PDE4 axis in modulating BCR activity in normal mature B lymphocytes and B cell lymphomas; 2. Determine in vitro and vivo the effects of the combinatorial targeting of PDE4 and BCR-dependent kinases in human and murine B cell lymphoma. Upon completion, this study may identify cAMP as mediator of BCR signal termination, and PDE4 inhibition as a novel approach to target the aberrant BCR signaling pathway. If positive, our data will fulfill one of the tenets of contemporary rational therapeutic design, the targeting of a critical pathway, the BCR, with distinct drug classes, phosphodiesterase and kinase inhibitors.