HMGB1参与白血病细胞分化的分子机制研究

Acute promyelocytic leukemia (APL) is a unique subtype of the acute leukemias. It is caused by an arrest of leukocyte differentiation at the promyelocyte stage. In APL, all-trans retinoic acid induces degradation of the fusion protein encoded by the PML-RARα oncogene [a fusion protein of promyelocytic leukemia (PML) and the retinoic acid receptor-α (RARα)], differentiation of leukaemic cells and clinical remissions. Our recent study demonstrated that autophagy is a crucial regulator of PML-RARα degradation and leukocyte differentiation. High mobility group box 1 (HMGB1) is a prototypical DAMP and is associated with the hallmarks of cancer. Recently we found that HMGB1 release after chemotherapy treatment is a critical regulator of autophagy and a potential drug target for therapeutic interventions in leukemia. Overexpression of HMGB1 by gene transfection rendered leukemia cells resistant to cell death; whereas depletion or inhibition of HMGB1 and autophagy by RNA interference or pharmacological inhibitors increased the sensitivity of leukemia cells to chemotherapeutic drugs. Based on these findings, our hypothesis is that HMGB1 regulates APL differentiation by autophagy. We will determine whether endogenous HMGB1 regulates PML-RARα degradation and function. We will determine the signal pathways and strctural basis of exogenous HMGB1-mediated differentiation of leukaemic cells. In light of the therapeutic promise of autophagy inhibitors to render tumor cells more susceptible to conventional therapies, our discovery that HMGB1 is an important regulator of autophagy in leukemia cells may lead to the development of novel strategies for the treatment of human leukemias including APL.

探索细胞分化机制、改善"诱导分化治疗"，仍然是白血病研究热点。项目组在《Autophagy》上报道自噬是白血病细胞分化调控的新机制，并在《Leukemia》上首次报道高迁移率族蛋白1（HMGB1）促进化疗中自噬形成。申请者在此基础之上进一步提出"HMGB1促进白血病细胞分化"的科学假说，并拟采用突变体构建、凝胶滞留实验、染色质免疫共沉淀，免疫共沉淀等先进研究手段，探讨白血病细胞分化时HMGB1的定位改变机制及其功能意义，其中内源性和外源性HMGB1如何调控白血病细胞分化是研究重点。内源性HMGB1对细胞分化的影响侧重于对PML-RARα融合蛋白降解和核功能影响的研究，外源性HMGB1对细胞分化的影响侧重于阐明HMGB1的信号受体、分子结构基础与细胞分化的关系。开展本项目可望揭示HMGB1在白血病中的作用新机制，为细胞分化的研究开辟新的领域，为寻找白血病治疗药物和手段提供新的思路与实验线索。

探索细胞分化机制、改善“诱导分化治疗”，仍然是白血病研究热点。为了阐明HMGB1参与白血病细胞分化的分子机制和结构基础，通过一系列的研究方法，首先探讨了活性氧（ROS）通过调控内源性HMGB1介导的自噬反应促进了白血病细胞分化，并初步证实了P62/PML-RaRα蛋白复合物的解离促进RaRα蛋白降解和NB4细胞分化成熟。进一步发现PKM2 介导的Warburg 效应（即有氧糖酵解）是调控脓毒症HMGB1释放的机制之一，以及HMGB1-DNA复合物通过晚期糖基化终末产物受体（RAGE）介导调控细胞炎症活性及自噬反应，对临床中脓毒症的治疗提供了新的理论依据。在HMGB1与白血病分化的基础上，研究了HMGB1相关DAMP分子WAVE1介导的自噬反应调控白血病细胞凋亡的机制；同时，探讨了新的细胞死亡方式铁死亡促进急性髓系白血病对化疗药物的敏感性的机制。最后，重点研究了HMGB1二磷酸腺苷核糖多聚化介导自噬反应调控TNFSF10/TRAIL的化疗耐药的机制，为克服TNFSF10所致的化疗耐药提供新的观点，较为圆满的完成了课题计划。