Cyclic AMP-mediated apoptosis in lymphoid malignancies

描述（由申请人提供）：4型cAMP磷酸二酯酶（PDE 4）抑制剂，如在B细胞慢性淋巴细胞白血病中的咯利普兰诱导的细胞凋亡，即使在不存在激活腺苷酸环化酶的外源性药物如二萜毛喉素的情况下。相反，T细胞或T-CLL对咯利普兰诱导的细胞凋亡具有抗性。Rolipram诱导B-CLL细胞中的线粒体死亡途径，可能部分是由于磷酸酶PP 2A的活化和BAD的去磷酸化。值得注意的是，cAMP还可以通过EPAC 1激活B-CLL中的抗凋亡途径，EPAC 1是cAMP激活的Rap 1 GDP交换因子。B-CLL细胞在其EPAC 1的功能表达方面在循环造血细胞中是独特的，这表明EPAC 1信号传导可能在这种疾病的病理生理学中起作用。具体目标一。为了阐明PDE 4抑制剂激活B-CLL中细胞凋亡的线粒体途径的机制，我们将：A）确定PDE 4抑制剂诱导的CLL中细胞凋亡是否是PKA介导的。B）确定CLL中咯利普兰诱导的细胞凋亡是否是EPAC非依赖性的。C）确定咯利普兰诱导的增强的CLL PP 2A活性的机制。D）确定PP 2A是否是CLL中咯利普兰介导的细胞凋亡所需的。具体目标二。为了对比EPAC和PKA信号传导在CLL中的作用，我们将：A）确定PDE 4抑制剂的PKA活化是否阻断EPAC活化增加B-CLL趋化因子转录水平的能力。B）确定EPAC诱导的趋化因子和/或Mcl-1转录物的增加是否是循环造血细胞中B-CLL所特有的。C）确定EPAC诱导的B-CLL存活的增加是否是由IL-8自分泌环的上调引起的。D）确定PKA和EPAC是否差异调节PI 3 K或其下游靶标。具体目标三。为了确定功能性EPAC在CLL细胞中的独特表达是否具有病理生理学重要性，我们将：A）检查EPAC活化对CLL粘附和迁移的影响。B）比较EPAC和PKA活化对基础和化疗诱导的CLL存活的影响。C）比较EPAC和PKA对CLL和B细胞增殖的影响。

DESCRIPTION (provided by applicant): Inhibitors of type 4 cAMP phosphodiesterase (PDE4) such as rolipram-induced apoptosis in B cell chronic lymphocytic leukemia, even in the absence of exogenous pharmacologic agents that activate adenylate cyclase such as the diterpene forskolin. T cells or T-CLL, in contrast, are resistant to rolipram-induced apoptosis. Rolipram induces a mitochondrial death pathway in B-CLL cells, perhaps in part due to activation of the phosphatase PP2A and dephosphorylation of BAD. Remarkably, cAMP can also activate an antiapoptotic pathway in B-CLL through EPAC1, a cAMP-activated Rap1 GDP exchange factor. B-CLL cells are unique among circulating hematopoietic cells in their functional expression of EPAC1, suggesting EPAC1 signaling may play a role in the pathophysiology of this disease. Specific Aim I. To elucidate the mechanism by which PDE4 inhibitors activate a mitochondrial pathway of apoptosis in B-CLL, we will: A) Determine whether PDE4 inhibitor-induced apoptosis in CLL is PKA-mediated. B) Determine whether rolipram-induced apoptosis in CLL is EPAC-independent. C) Determine the mechanism for rolipram-induced augmented CLL PP2A activity. D) Determine whether PP2A is required for rolipram-mediated apoptosis in CLL. Specific Aim II. To contrast the roles of EPAC and PKA signaling in CLL, we will: A) Determine whether PKA activation by PDE4 inhibitors blocks the ability of EPAC activation to augment B-CLL chemokine transcript levels. B) Determine if EPAC-induced augmentation of chemokine and/or Mcl-1 transcripts is unique to B-CLL among circulating hematopoietic cells. C) Determine if EPAC-induced augmentation of B-CLL survival results from up-regulation of an IL-8 autocrine loop. D) Determine whether PKA and EPAC differentially regulate PI3K or its downstream targets. Specific Aim III. To determine whether the unique expression of functional EPAC in CLL cells is of pathophysiologic importance, we will: A) Examine the effects of EPAC activation on CLL adhesion and migration. B) Compare the effects of EPAC and PKA activation on both basal and chemotherapy-induced CLL survival. C) Compare the effects of EPAC and PKA on CLL and B cell proliferation.