果糖1,6-二磷酸醛缩酶B调控肝癌糖代谢重构的机制研究

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and China accounts for > 50% of the newly diagnosed liver cancer cases. The unsatisfactory clinical prognosis of HCC has been largely attributed to a poor understanding of the underlying molecular mechanisms of HCC. Metabolic reprogramming has been regarded as the core hallmark of cancer but metabolic studies in HCC are surprisingly limited. Our gene expression microarray analysis found a significant downregulation of fructose-1,6-bisphosphate Aldolase B (ALDOB) in HCC tumor tissue comparing to adjacent normal tissues. ALDOB is a critical enzyme regulating glycolysis and gluconeogenesis; however, it is unknown whether loss of Aldob in HCC affords any metabolic advantages during the progression of HCC. WE HYPOTHESIZE THAT ALDOB ACTS AS A METABOLIC SWITCH COORDINATING GLYCOLYSIS AND PENTOSE PHOSPHATE PATHWAY DURING THE PROGRESSION OF HCC. We propose to investigate the molecular mechanism on how AldoB regulates metabolic reprogramming in HCC using metabolic flux analysis, cell and liver specific knockout of ALDOB mouse model as well as clinical samples. Our preliminary studies identified that expression patterns of ALDOB and glucose-6-phosphate dehydrogenase (G6PD) predicted the clinical outcome of HCC. Over-expression of ALDOB and G6PD knockdown significantly suppressesed tumor cell proliferation and migration in vitro and in vivo. Furthermore, ALDOB suppressed tumorigenesis by direct interaction with G6PD and inhibiting G6PD activity. Successful completion of this project will establish a critical role for ALDOB in metabolic reprogramming to sustain tumor cell rapid proliferation and survival, suggesting that targeting ALDOB and its interaction with G6PD might be a viable therapeutic strategy.

代谢重构在肝癌发生发展过程中起重要作用，但分子机制还不清楚。我们对配对临床肝癌样本进行基因表达芯片和代谢组学分析，发现肝癌肿瘤组织与正常组织相比糖酵解和磷酸戊糖途径代谢流增加，糖酵解途径关键代谢酶果糖1,6-二磷酸醛缩酶B（ALDOB）在癌组织中极大的下调，同时磷酸戊糖途径的限速酶G6PD显著上调；我们还发现ALDOB与G6PD相互作用抑制G6PD酶活及肿瘤细胞的增值与迁移；临床试验还显示ALDOB和G6PD的表达与肝癌预后生存相关。因此我们认为ALDOB调控着肝癌代谢重构并抑制肝癌的发生发展。在本项目中，我们将应用肝癌细胞、ALDOB肝特异敲除小鼠模型和临床实验等探讨ALDOB和G6PD如何介导肿瘤细胞代谢途径重构并促进肿瘤细胞的生长，以此揭示该基因和蛋白对肝癌细胞生长过程的代谢调控规律，为肝癌的临床诊断、药物靶点治疗和预后判断提供科学依据。

肝癌的发病率和死亡率在全球的癌症中位于第六位和第四位，其中肝细胞癌 (HCC) 大约占所有肝癌病理类型的90%。代谢异常是肿瘤的重要特征之一，肿瘤细胞会经历一系列代谢重编程来满足自身快速增殖的需要，但是HCC中代谢重构的机制尚不十分清楚。在本项目中，我们利用多种ALDOB基因敲除小鼠模型，结合细胞生物学与临床试验发现了ALDOB的两个非酶功能，取得了一系列重要的研究成果：.(1) ALDOB通过与p53/G6PD相互作用抑制G6PD酶活以及PPP通路; HCC 发生发展过程中ALDOB的丢失造成G6PD 酶活以及PPP代谢通路的上调，促进肝癌发生 (Li et al, Nature Cancer, 2020)；.(2) ALDOB通过与AKT/PP2A相互作用抑制AKT信号通路，ALDOB的丢失激活AKT, 促进肿瘤细胞增殖、代谢与细胞周期进展，抑制AKT或者激活PP2A均可抑制肝癌 (He et al, Plos Biology, 2020);.(3) 花生红衣多酚类活性成分原花青素-B2 (OPC-B2)抑制AKT信号通路发挥抑制肝癌作用, OPC-B2可以直接结合AKT, 发挥别构抑制剂的作用 (Liu et al, Redox Biology, 2020); .(4) 酵母β-葡聚糖是一种新型的自噬抑制剂，在体内对肝癌细胞的增殖、代谢和肿瘤生长具有显著的抑制作用 (Wang et al, Redox Biology, 2020). . 综上所述，本研究系统阐明了ALDOB在HCC中通过多种机制扮演了肿瘤抑制子的角色，并发现了ALDOB全新的非酶功能，即通过与另一个代谢酶G6PD直接相互作用来抑制其酶活，同时介导增强p53对G6PD的抑制，从而抑制HCC的发生发展；还可以与AKT/PP2A相互作用调控其上游信号通路。以上研究有可能对肝癌代谢乃至肿瘤代谢领域产生重大影响。