膜联蛋白Annexin II在急性早幼粒细胞白血病中高表达的病理生理效应及分子调控机制

Annexin II（Ann-II）在急性早幼粒细胞白血病（APL）细胞中异常高表达，所致的纤维蛋白溶解亢进是患者早期出血死亡的关键原因之一。申请者前期阐明了导致APL出血的重要因子Tissue factor的分子调控机制（PNAS 2010），目前又发现另一出血关键因子Ann-II的高表达与APL特征性PML/RARα融合蛋白调控有关；而诱导分化药物可迅速下调Ann-II并改善临床出血症状。故拟在U937/PR9细胞中，研究1）PML/RARα融合蛋白上调Ann-II高表达所致纤溶亢进、白血病细胞侵袭等病理生理效应；2）应用启动子截短分析策略，通过荧光素酶活性分析、EMSA、ChIP、Co-IP等手段，探讨PML/RARα融合蛋白上调Ann-II表达的分子机制。3）应用上述类似的转录调控研究手段，阐明诱导分化药物下调其表达的分子机制。为系统解释并防治出凝血并发症、白血病浸润提供理论基础。

Aberrant annexin II expression and consequent hyperfibrinolysis in acute promyelocytic leukemia (APL) are one of causes for the early death of APL patients. In the past 5 years, the applicant has been focusing on the molecular mechanism of regulation of tissue factor, which triggers disseminated intravascular coagulation in APL bleeding complication, and the transactivation of tissue factor by PML/RAR alpha fusion protein was accepted and published in PNAS, 2010. Annexin II, which aberrantly expressed in APL cells, is a membrane protein as the cofactor for t-PA and plasminogen. High level expression of annexin II overproduces plasmin to induce hyperfibrinolysis, a known major component of APL bleeding complication. The recent findings in our laboratory indicate that annexin II is up-regulated by PML/RAR alpha fusion protein, an oncoprotein specific for the leukemogenesis of APL, but down-regulated by differentiation agents such as all-trans retinoic acid and/or arsenic trioxide (ATRA/AS2O3) for rapid alleviation of bleeding. Therefore, the current project is designed to further investigate: 1) the functional significance of aberrant annexin II expression in APL cells, such as hyperfibrinolysis and cell invasion; 2) the molecular mechanism of annexin II up-regulation by PML/RAR alpha fusion protein using promoter deletion analysis, luciferase activity assay, EMSA, chromatin immunoprecipitation and co-immunoprecipitation; 3) the molecular mechanism of annexin II down-regulation by differentiation agents ATRA/AS2O3 using similar research methods outlined above. Taken together, this project is intended to elucidate the functional significance and underlying molecular basis of aberrant annexin II expression in the pathogenesis of APL coagulopathy. The ramification of our findings has clinical importance, as annexin II may serve as a novel therapeutic target aiming to minimize the fatality caused by coagulopathy and relapse from leukemia infiltration in APL patients.