Anti-angiogenic effects of pl6, p53, PTEN tumor suppressor gene transfer on human malignant gliomas

除了p16、p53和PTEN的改变外，从低级别到高级别胶质瘤的恶性进展还伴随着血管生成因子的过度产生和抗血管生成效应物的抑制。然而，肿瘤抑制基因与人类胶质瘤血管生成相关物质之间的关系尚未得到充分解决。本研究的目的是探讨p16、p53和PTEN基因转移对胶质瘤血管生成的影响。我们重点研究了血管内皮生长因子（VEGF）作为一种有效的血管生成刺激剂，血栓反应蛋白-1 （TSP-1）和TSP-2作为血管生成抑制剂。p16基因在U251MG和U87MG中是内源性缺失的。p53基因在U251MG细胞中发生突变，但在U87MG细胞中是完整的。内源性PTEN在U251MG和U87MG中都发生突变。感染含有野生型p16、p53或PTEN cDNA的重组复制缺陷腺病毒载体可显著降低VEGF的表达，这取决于每种胶质瘤细胞系的基因状态。野生型p53或PTEN的转导增强了TSP-1和TSP-2的表达。相比之下，野生型p16的恢复对TSP-1的表达没有影响，但在p16缺失的胶质瘤细胞中增加了TSP-2的表达。体内血管生成实验表明，腺病毒介导的p16、p53和PTEN基因转移可显著抑制肿瘤新生血管的形成。总之，这些在人类胶质瘤中经常被观察到失去功能的抑制基因也与肿瘤血管生成密切相关。本研究提示p16、p53和PTEN基因转移可能是恶性胶质瘤的一种合适的抗血管生成治疗方法。

In addition to the alteration of p16, p53, and PTEN, the malignant progression from low to high-grade gliomas is accompanied by overproduction of angiogenic factors and suppression of anti-angiogenic effectors. However, the relationship between tumor suppressor genes and angiogenic-related substances in human gliomas has not been sufficiently resolved. The aim of the present study was to investigate the effects of p16, p53, and PTEN gene transfer on glioma angiogenesis. We focused on vascular endothelial growth factor (VEGF) as a potent angiogenic stimulator, and thrombospondin-1 (TSP-1) and TSP-2 as angiogenic inhibitors. The p16 gene is endogenously deleted in U251MG and U87MG. The p53 gene is mutated in U251MG but is intact in U87MG cells. Endogeneous PTEN is mutated in both U251MG and U87MG. Infection with recombinant replication-defective adenovirus vector containing the cDNA of wild-type p16, p53, or PTEN significantly reduced the expression of VEGF depending on the gene status of each glioma cell line. TSP-1 and TSP-2 expression was enhanced by the transduction of wild-type p53 or PTEN. In contrast, the restoration of wild-type p16 had no effect on TSP-1 expression, but increased TSP-2 in p16-deleted glioma cells. In vivo angiogenesis assay showed that adenovirus-mediated gene transfer of p16, p53, and PTEN markedly inhibited tumor neovascularization. In conclusion, these suppressor genes, which are frequently observed to lose function in human gliomas, are also closely related to tumor angiogenesis. The present study suggests that p16, p53, and PTEN gene transfer may be a suitable anti-angiogenic therapy for malignant gliomas.