ULK1-FIP200调控HMGB1转位介导的自噬相关白血病耐药的机制研究

Acute lymphoblastic leukaemia is a common paediatric cancer. The acquisition of drug resistance is a significant obstacle to the achievement of favourable outcomes, and autophagy is regarded as a mechanism that underlies chemoresistance. As critical effector of autophagosome formation, the Ulk13-FIP200 complex and the Beclin1-HMGB1 complex are not independent modules. In addition, the translocation of HMGB1 from nucleus to cytoplasm is a crucial molecular event during autophagy. However, the association between the activities of these complexes and the function of HMGB1 translocation, specifically in leukaemia, have yet to be clearly elucidated. Our previous studies and preliminary experiments show that Ulk1-FIP200 complex functions upstream of the Beclin1-HMGB1 and HMGB1 translocation is involved in their regulatory relationships. The acetylation of HMGB1 is related to its translocation. Bioinformatics prediction shows that STAT5 may activate SIRT6 by stimulating the transcription initiation and then influence the acetylation of HMGB1 via PARP-1. Therefore we assume that the ULK1-FIP200 phosphorylates STAT5, activates SIRT6 and assists the HMGB1 translocation by acetylating HMGB1 via PARP-1, and consequently promotes the assembly of the Beclin1-HMGB1 and promotes autophagy-related chemoresistance in leukaemia. We intend to prove this science hypothesis using in vitro and in vivo methods. The findings will have important implications for further study on the mechanism of autophagy-related chemoresistance. We are likely to develop new combination therapy strategies, render tumour cells more susceptible to conventional therapies and overcome drug resistance in leukaemia, and even other tumours.

白血病是儿童常见的恶性肿瘤。耐药是难治、复发的重要因素，自噬在其中发挥重要作用。但自噬起始时HMGB1从胞核转位到胞浆，和关键蛋白复合物ULK1-FIP200、Beclin1-HMGB1，三者之间的调控机制尚不明确。前期研究和预实验发现ULK1-FIP200通过协助HMGB1转位促进Beclin1-HMGB1形成，这一过程与HMGB1乙酰化有关；利用生物信息学还预测了STAT5可能激活SIRT6转录活化并通过PARP-1影响HMGB1的乙酰化。因此我们推测ULK1-FIP200是通过磷酸化激活STAT5，并导致SIRT6转录活化，借助PARP-1对HMGB1进行乙酰化修饰来协助其转位，从而促进下游Beclin1-HMGB1组装，介导自噬相关白血病细胞耐药。本项目拟通过体内外实验，明确这一科学假说，对深入阐明自噬介导的白血病耐药机制有重要意义，有望为解决白血病乃至其他肿瘤耐药难题提供新思路。

白血病是儿童常见的恶性肿瘤，而耐药是白血病难治、复发的重要因素，其中自噬发挥重要的作用。已有研究表明HMGB1在化疗药物所致白血病耐药的机制中发挥重要作用。研究表明自噬起始时HMGB1从胞核转位到胞浆，但其与自噬的关键蛋白复合物ULK1-FIP200、Beclin1之间的调控机制尚不明确。本项目拟探讨ULK1-FIP200调控HMGB1转位介导的自噬相关白血病耐药的具体分子机制。本课题组从临床数据切入，发现自噬关键蛋白HMGB1与儿童急性淋巴细胞白血病相关。在体外细胞实验中，发现沉默FIP200可显著抑制化疗诱导的白血病细胞自噬，并恢复恢复白血病细胞对化疗敏感性；在化疗药物诱导的自噬中，ULK1-mAtg13-FIP200复合物是HMGB1- Beclin1复合物的形成的上游信号；ULK1-mAtg13-FIP200复合物的形成能促进HMGB1的核-浆转位以及下游HMGB1-Beclin1复合物的形成，进而上调自噬。进一步研究还表明PARP-1可以促进HMGB1进行聚ADP核糖基化并易化其乙酰化；SIRT6作为PARP-1活化的上游信号参与HMGB1的核-浆转位；沉默SIRT6及PARP-1基因可抑制HMGB1的核-浆转位及化疗药物诱导的白血病细胞的耐药自噬，SIRT6-PARP1复合物的形成与HMGB1的聚ADP核糖基化及乙酰化相关。动物实验也初步证实了HMGB1聚ADP-核糖基化以及乙酰化可促进其核-浆转位诱导的白血病细胞发生自噬相关耐药。综上所述，本项目阐明了ULK1-FIP200复合物通过活化SIRT6-PARP-1，促进HMGB1的聚ADP-核糖基化以及乙酰化，从而促进其发生核-浆转位并介导自噬相关白血病耐药的分子机制。该研究成果为制定抗肿瘤及抗耐药联合治疗策略提供了理论依据，为解决白血病耐药难题提供了新思路。