SENP7调控MDH1促发氧化磷酸化在AML化疗耐药中的作用及机制研究

While cytotoxic chemotherapy can occasionally cure hematologic cancers, a significant portion of patients only partially respond or relapse. Resistance to chemotherapy and relapse following remission are critical problems in acute myeloid leukemia (AML) which drives failure of treatment and finally death of patients. The mechanisms leads to chemoresistance of AML is obscure. Recent evidence have showed that oxidative phosphorylation (OXPHOS) can mediate chemoresistance of AML and is a promising target for reversing resistance and improve the outcome of AML patients. The SUMO (small ubiquitin-like modifier) proteases (SENPs) deconjugate SUMO modified proteins and maintain the balance of SUMOylated and de-SUMOylated substrates required for normal physiology. Abnormal expression or activity of SENPs can cause various pathological conditions by targeting certain target protein(s). Our previous work have explored the role of SENP1 in leukemogenesis of AML, but the role of SENPs in chemoresistance of AML is unknown. Our preliminary results show that the expression of SENP7 in chemoresistant AML was significantly elevated and was significantly associated with the prognosis of AML; Multivariate analysis demonstrated that SENP7 is an independent prognostic factor for AML. We also found that over-expression of SENP7 in AML cell lines could directly lead to the occurrence of chemoresistance of AML cells. We have identified that malate dehydrogenase 1 (MDH1) is a novel target of SENP7 by mass spectrometry. SENP7 can up-regulate the activity of MDH1, the up-regulated MDH1 activity can enhances the OXPHOS of cells. We have also demonstrated that the SENP7 can deconjugate the SUMOylation of MDH1. Therefore, we envisage that: SENP7 enhances the activity of MDH1 by de-SUMOylation, then promotes OXPHOS and mediates AML chemoresistance. This study intends to establish the role of SENP7 in AML chemoresistance and elucidate the molecular mechanism of SENP7-MDH1 axis involved in chemoresistance. Collectively, these studies will provide new insights into the mechanisms of AML chemoresistance and provide new strategies for reversing chemoresistance.

急性髓细胞白血病（AML）化疗耐药是治疗失败的关键原因。氧化磷酸化的增强能够介导AML的化疗耐药，但调控机制不明。蛋白翻译后SUMO化修饰和去SUMO修饰的平衡由去SUMO蛋白酶SENPs调控，其失衡参与多种病理生理过程。我们初步研究显示，SENP7在化疗耐药AML中表达明显升高，并且与AML预后显著相关； SENP7过表达能直接导致AML化疗耐药的发生，经质谱鉴定出其全新的靶蛋白苹果酸脱氢酶1（MDH1），SENP7能够上调MDH1的活性，MDH1活性上调能够促发细胞氧化磷酸化；并且证实SENP7能够去除MDH1的SUMO化。因此设想：SENP7通过去除MDH1的SUMO化上调其活性，促发氧化磷酸化，介导AML化疗耐药。本课题拟确立SENP7在AML化疗耐药中的作用；阐明SENP7-MDH1轴参与化疗耐药的分子机制。这些研究将为了解AML的化疗耐药机制提供新视野，为逆转耐药提供新策略。

急性髓细胞白血病（AML）化疗耐药是治疗失败的关键原因，其背后复杂的调控机制非常值得深入研究。蛋白翻译后SUMO化修饰和去SUMO修饰的平衡由去SUMO蛋白酶SENPs调控，其失衡参与多种病理生理过程。我们通过AML患者骨髓单个核细胞标本的检测和分析，发现蛋白酶SENP7的高表达与AML的不良预后显著相关；敲低SENP7后，AML代表性细胞系HL-60及NB4细胞的集落形成能力明显下降，并且敲低SENP7能够使HL-60及NB4细胞阻滞在G1期；此外，敲低SENP7可提高HL-60及NB4细胞对Ara-C的敏感性。在标本和细胞系实验的基础上，我们利用NOD/SCID小鼠，构建了AML异种移植模型，采用流式细胞术分析小鼠体内的白血病负荷情况，检测脾脏的浸润情况，从体内水平证实SENP7在AML的进展中扮演着重要的作用，并且敲低SENP7可增加AML细胞对Ara-C的敏感性。利用转录组测序探索SENP7调控AML的具体机制，绘制了差异基因热图，对差异基因进行GO和KEGG富集分析，结果提示，SENP7主要参与到免疫反应、细胞外囊泡、肿瘤坏死因子受体结合及NF-KB信号通路。我们以Chemdiv (Version 2020)和Natural Compound Library数据库作为虚拟筛选的化合物库，利用计算机虚拟筛选技术，通过计算SENP7和小分子基于结合能的对接打分，得到59个最佳化合物和15个天然产物，值得进一步作为靶向SENP7治疗的探索。