Bmi1调控有氧糖酵解代谢促进胰腺癌干细胞免疫逃逸的作用及机制研究

We have successful elicited anti-pancreatic cancer stem cell immune through dendritic vaccine. We also found that inducing immature dendritic cells may be important causation of PCSC immune escape, but the mechanism is unclear. Applicants found that pancreatic cancer stem cells have active aerobic glycolysis, and its metabolites lactic acid may affect dendritic cell function. Because dendritic cells are key mediators of anti-tumor immune, its dysfunction may negatively regulate anti-tumor immunity, suggesting that abnormal glucose metabolism of pancreatic cancer stem cells may regulate the function of dendritic cells and promote immune evasion. Our previous studies have confirmed Bmi1 was overexpressed in pancreatic cancer stem cells, and Bmi1 can adjust aerobic glycolysis-related signals. Bioinformatics’ analysis showed that Bmi1 may associate with metabolic enzyme of aerobic glycolysis. Combined with the results of our preliminary experiments and related literature, we assumed that Bmi1 in pancreatic cancer stem cells may regulate the activity of aerobic glycolysis and lead to dysfunction of dendritic cell, which may cause immune escape. The project intends to explore the possible mechanisms of immune escape of the pancreatic cancer stem cells from the perspective of metabolism, and elucidate the relationship among Bmi1, aerobic glycolysis, dendritic cells, and immune escape. This project may provide experimental evidence for the interpretation and intervention of highly malignant behaviors of pancreatic cancer.

申报者前期构建树突状细胞(DC)疫苗诱导抗胰腺癌干细胞(PCSC)免疫,但发现DC成熟受阻并诱生免疫抑制等现象可导致PCSC免疫逃逸,然其机制不明。PCSC被证实有活跃的有氧糖酵解,可产生大量乳酸。因乳酸可能抑制DC成熟相关信号,预实验发现PCSC培养基预处理的DC不能有效活化,推测PCSC异常糖代谢通过乳酸阻抑DC成熟产生免疫抑制。申报者进一步证实Bmi1调控胰腺癌干细胞特性,生物信息学分析显示Bmi1与有氧糖酵解代谢酶相关联,可能活化Akt, mTOR等有氧糖酵解相关信号,结合前期结果和文献,提出假说:Bmi1调控PCSC发生活跃的有氧糖酵解导致DC成熟障碍,介导免疫逃逸。本项目拟在已构建DC疫苗基础上,围绕PCSC能量代谢,从细胞和动物实验等方面验证PCSC异常糖代谢对抗肿瘤免疫的影响,探讨Bmi1调控异常糖代谢对PCSC免疫逃逸的作用。本项目可能为阐释PCSC逃避免疫监视提供线索。

胰腺癌是一种高度恶性的消化系统肿瘤，预后极差。从新的角度去认识胰腺癌并探讨针对性的干预策略成为改善胰腺癌临床治疗效果的突破口。胰腺癌干细胞是导致胰腺癌恶性生物学行为的重要原因, 本课题在前期发现胰腺癌干细胞具有免疫逃逸的基础上, 重点探讨能量代谢对胰腺癌干细胞免疫逃逸的影响。Bmi1 是一种重要的干细胞调控因子, 可高表达于胰腺癌干细胞，促进耐药、转移等恶性生物学行为，本项目重点围绕Bmi1 对胰腺癌干细胞能量代谢的调控作用以及免疫调理作用及机制，明确胰腺癌免疫浸润模式和代谢特征的关系，以及可能的调控因素。本项目发现Bmi1 在胰腺癌干细胞中的过表达可促进RNA结合蛋白UPF1表达，UPF1与HK2mRNA结合并促进HK2 mRNA稳定性，导致HK2表达增加，最终促进活跃的有氧糖酵解发生。Bmi1介导的有氧糖酵解代谢可通过其代谢产物乳酸，对微环境中的免疫浸润细胞产生影响，抑制效应CD8+T细胞、DC细胞数量，而免疫抑制型CD8+PD1+ T cells, MDSC 数量增加。 抑制Bmi1 可以恢复抗肿瘤免疫细胞的浸润，增强CD8+T细胞的功能，降低免疫抑制细胞的浸润 （CD4+ Treg, PD-1+CD8+T cells, MAC）。同样抑制糖酵解代谢可逆转Bmi1过表达胰腺癌细胞的恶性生物学行为，重塑免疫抑制型微环境。不仅如此，我们还发现Bmi1对抗肿瘤免疫具有直接调理作用，Bmi1在胰腺癌细胞中的高表达可抑制MICA/B的表达，进而抑制NK细胞对胰腺癌的杀伤活性。 本课题首次从表观遗传学角度揭示了Bmi1的表达调控机理，证实Bmi1表达受H4组蛋白的乙酰化修饰调控， ACLY依赖性的乙酰辅酶A产生可调控Bmi1表达，高糖等胰腺癌微环境可能通过ACLY-KAT5调控H4的组蛋白乙酰化修饰调控Bmi1的表达。本项目从新的角度证实了Bmi1对胰腺癌恶性生物学行为的调控机制，靶向Bmi1的干预策略联合免疫治疗可能为胰腺癌的治疗提供新的思路和方向。