Department of Neurosurgery, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
J Natl Cancer Inst. 2020 Apr 1;112(4):343-355. doi: 10.1093/jnci/djz155.
Isocitrate dehydrogenase wild-type (WT) glioblastoma (GBM) accounts for 90% of all GBMs, yet only 27% of isocitrate dehydrogenase WT-GBMs have p53 mutations. However, the tumor surveillance function of WT-p53 in GBM is subverted by mechanisms that are not fully understood.
We investigated the proteolytic inactivation of WT-p53 by asparaginyl endopeptidase (AEP) and its effects on GBM progression in cancer cells, murine models, and patients' specimens using biochemical and functional assays. The sera of healthy donors (n = 48) and GBM patients (n = 20) were examined by enzyme-linked immunosorbent assay. Furthermore, effects of AEP inhibitors on GBM progression were evaluated in murine models (n = 6-8 per group). The statistical significance between groups was determined using two-tailed Student t tests.
We demonstrate that AEP binds to and directly cleaves WT-p53, resulting in the inhibition of WT-p53-mediated tumor suppressor function in both tumor cells and stromal cells via extracellular vesicle communication. High expression of uncleavable p53-N311A-mutant rescue AEP-induced tumorigenesis, proliferation, and anti-apoptotic abilities. Knock down or pharmacological inhibition of AEP reduced tumorigenesis and prolonged survival in murine models. However, overexpression of AEP promoted tumorigenesis and shortened the survival time. Moreover, high AEP levels in GBM tissues were associated with a poor prognosis of GBM patients (n = 83; hazard ratio = 3.94, 95% confidence interval = 1.87 to 8.28; P < .001). A correlation was found between high plasma AEP levels and a larger tumor size in GBM patients (r = 0.6, P = .03), which decreased dramatically after surgery.
Our results indicate that AEP promotes GBM progression via inactivation of WT-p53 and may serve as a prognostic and therapeutic target for GBM.
野生型异柠檬酸脱氢酶（IDH）脑胶质瘤（GBM）占所有 GBM 的 90%，但只有 27%的 IDH WT-GBM 存在 p53 突变。然而，WT-p53 在 GBM 中的肿瘤监测功能被尚未完全阐明的机制所颠覆。
我们使用生化和功能测定法，研究了天冬酰胺内肽酶（AEP）对 WT-p53 的蛋白水解失活作用，及其对癌细胞、鼠模型和患者标本中 GBM 进展的影响。我们通过酶联免疫吸附试验检测了 48 名健康供体（健康对照）和 20 名 GBM 患者的血清。此外，我们还在鼠模型中评估了 AEP 抑制剂对 GBM 进展的影响（每组 6-8 只）。使用双尾学生 t 检验确定组间的统计学显著性。
我们证明，AEP 与 WT-p53 结合并直接切割 WT-p53，导致 WT-p53 在肿瘤细胞和基质细胞中通过细胞外囊泡通讯抑制 WT-p53 介导的肿瘤抑制功能。未切割的 p53-N311A 突变体高表达可挽救 AEP 诱导的肿瘤发生、增殖和抗凋亡能力。敲低或药理学抑制 AEP 可减少鼠模型中的肿瘤发生并延长生存期。然而，AEP 的过表达促进了肿瘤发生并缩短了生存时间。此外，GBM 组织中 AEP 水平较高与 GBM 患者的预后不良相关（n=83；风险比=3.94，95%置信区间=1.87 至 8.28；P<0.001）。我们发现，GBM 患者的血浆 AEP 水平与肿瘤较大呈正相关（r=0.6，P=0.03），术后水平显著下降。
我们的结果表明，AEP 通过失活 WT-p53 促进 GBM 进展，可能成为 GBM 的预后和治疗靶点。
