Department of Neurology, University Hospital Heidelberg, Heidelberg, Germany.
Neuro Oncol. 2010 Sep;12(9):894-907. doi: 10.1093/neuonc/noq051. Epub 2010 May 26.
Previous findings suggest an angiogenesis-regulating function of the p53 tumor suppressor protein in various malignancies. With several antiangiogenic agents entering the clinic, we assessed the value of the TP53 status in predicting angiogenesis in glioblastoma in vivo and examined underlying angiogenic-signaling pathways in vitro. We identified 26 TP53 wild-type and 9 TP53 mutated treatment-naïve, primary, isocitrate dehydrogenase 1 (IDH1) wild-type glioblastoma specimens by sequence analysis and quantified vascularization. P53 responsiveness of the angiogenesis-related target genes, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), thrombospondin 1 (TSP-1), brain-specific angiogenesis inhibitor 1 (BAI1), and collagen prolyl-4-hydroxylase alpha 2 (P4HA2), was evaluated by (i) overexpression of wild-type p53 in homozygously TP53-deleted LN-308 cells; (ii) shRNA-mediated p53 knockdown in the TP53 wild-type LNT-229 cells; and (iii) chemical induction of wild-type p53 expression in LNT-229 cells by camptothecin. Irrespective of the TP53 status, vascularization did not differ significantly between the two groups of glioblastoma specimens. Of all target genes, only P4HA2 mRNA was upregulated through wild-type p53. As opposed to several nonglial tumors, in glioblastoma cells, p53-mediated transcriptional induction of P4HA2 mRNA neither resulted in increased levels of P4HA2 protein or antiangiogenic endostatin nor did it influence endothelial cell sprouting, viability, or transmigration in vitro. Moreover, p53-uncoupled stable overexpression of P4HA2 in LN-308 cells did not affect endothelial cell viability. These data challenge the view of p53 as an angiogenesis-regulator in glioblastoma in that relevant signaling pathways are silenced, potentially contributing to the angiogenic switch during malignant progression.
先前的研究结果表明，p53 肿瘤抑制蛋白在多种恶性肿瘤中具有调节血管生成的功能。随着几种抗血管生成药物进入临床，我们评估了 TP53 状态在预测体内胶质母细胞瘤血管生成中的价值，并在体外研究了潜在的血管生成信号通路。我们通过序列分析鉴定了 26 例 TP53 野生型和 9 例 TP53 突变型初治、异柠檬酸脱氢酶 1（IDH1）野生型胶质母细胞瘤标本，并对血管化进行了定量。通过（i）在 TP53 缺失的 LN-308 细胞中过表达野生型 p53；（ii）在 TP53 野生型 LNT-229 细胞中用 shRNA 敲低 p53；（iii）用喜树碱诱导 LNT-229 细胞中野生型 p53 的化学表达，评估了与血管生成相关的靶基因（如血管内皮生长因子[VEGF]、碱性成纤维细胞生长因子[bFGF]、血小板反应蛋白 1[TSP-1]、脑特异性血管生成抑制剂 1[BAI1]和胶原脯氨酰-4-羟化酶 α2[P4HA2]）的 p53 反应性。无论 TP53 状态如何，两组胶质母细胞瘤标本的血管化均无显著差异。在所有靶基因中，只有 P4HA2mRNA 被野生型 p53 上调。与几种非神经胶质瘤肿瘤不同，在胶质母细胞瘤细胞中，p53 介导的 P4HA2mRNA 转录诱导既没有导致 P4HA2 蛋白或抗血管生成内皮抑素水平的增加，也没有影响内皮细胞的发芽、活力或体外迁移。此外，LN-308 细胞中 p53 分离的稳定过表达 P4HA2 并不影响内皮细胞活力。这些数据挑战了 p53 作为胶质母细胞瘤中血管生成调节剂的观点，因为相关的信号通路被沉默，这可能有助于恶性进展期间的血管生成开关。
