Phosphodiesterase 4B as a Therapeutic Target in Lymphoma

描述（由申请人提供）：本研究的主要目的是确定PDE4B作为弥漫性大b细胞淋巴瘤（DLBCL）治疗探索的新靶点的作用，DLBCL是成人中最常见的b淋巴细胞恶性肿瘤。DLBCL是一种侵袭性和异质性疾病，其中只有大约40%的患者可以通过标准治疗治愈。更积极和/或剂量强化的化疗方案不能提供主要的生存优势，可能具有更高的毒性。因此，为了提高DLBCL的治愈率，我们需要更好地了解其分子基础，并将这些发现转化为针对这些肿瘤特定遗传病变的治疗方法。为了实现这一目标，我们在微阵列上使用表达谱，发现了与疾病结果相关的单个基因和途径。在我们的初步研究中，致死性/难治性DLBCL中最显著的过表达基因之一是磷酸二酯酶4B （PDE4B）。这种酶能使cAMP失活，cAMP是诱导b淋巴细胞细胞周期阻滞和凋亡的第二信使。因为PDE4B终止cAMP活性，它消除了这些负面影响。我们的初步研究证实，在DLBCLs中，PDE4B通过与PI3K/AKT生存通路的独特串导，阻断camp介导的细胞凋亡。在这项初步研究中，我们还在体外证实了PDE4抑制剂治疗这些恶性肿瘤的潜力。在本提案中，我们将以这些初步数据为基础，实现两个具体目标：明确cAMP-PDE4B在DLBCL中调节PI3K/AKI活性的机制。2. 建立小鼠DLBCL模型，在体内证实PDE4抑制剂治疗该疾病的有效性。

DESCRIPTION (provided by applicant): The major objective of this research is to firmly establish the role of PDE4B as a novel target for therapeutic exploration in diffuse large B-cell lymphoma (DLBCL), the most common B-lymphoid malignancy in adults. DLBCL is an aggressive and heterogeneous disorder in which only approximately 40% of the patients can be cured with standard therapy. More aggressive and/or dose-intensified chemotherapy regimens do not provide major survival advantages may have higher toxicity. Therefore, to improve the cure rate in DLBCL, we need to better understand its molecular basis and translate these findings into therapies that target the specific genetic lesions of these tumors. Towards this goal, we used expression profiling on microarrays and found single genes and pathways that were associated with the disease outcome. In our pilot study, one of the most prominently over expressed genes in fatal/refractory DLBCL was the phosphodiesterase 4B (PDE4B). This enzyme inactivates cAMP, a second messenger which induces cell cycle arrest and apoptosis in B-lymphocytes. Because PDE4B terminates cAMP activity, it abrogates these negative effects. Our preliminary studies confirmed that in DLBCLs PDE4B blocks cAMP-mediated apoptosis, via a unique cross-talk with the PI3K/AKT survival pathway. In this initial study, we also confirmed, in vitro, the potential of PDE4 inhibitors in the treatment of these malignancies. In the present proposal, we will build on these preliminary data to address two specific aims: 1. Define the mechanisms by which cAMP-PDE4B modulate PI3K/AKI activity in DLBCL. 2. Develop murine DLBCL models to confirm, in vivo, the effectiveness of PDE4 inhibitors in the treatment of this disease. Our study plan exploits a series of tools that we have recently generated, including a DLBCL cell line with low endogenous PDE4B activity reconstituted with a retrovirus vector to express wild-type PDE4B or a phosphodiesterase inactive mutant. In specific aim one, we will utilize these cells to define how intracellular cAMP/PDE4B modulates PI3K activity; we will specifically study cAMP effects on protein tyrosine kinases (PTK) that regulate PI3K and on the small GTPase Ras. To precisely evaluate the role of the PTKs in this process, we will also use DT-40 knockout lymphoma cells lacking relevant upstream kinases. To resolve the role of Ras, we will retrovirally generate DLBCL cells expressing constitutive active (V12) or dominant negative (N17) forms of this protein. In aim two we will generate human DLBCL xenografts in NOD/SCID mice to define the effectiveness of PDE4B inhibitors in the treatment of these tumors. Since clinical grade PDE4 inhibitors are available and currently in clinical trials for a variety of conditions, the findings derived from this proposal can realistically lead to novel therapeutic strategies in DLBCL.