Plate K H, Breier G, Millauer B, Ullrich A, Risau W
Max-Planck-Institut für Psychiatrie, Abteilung Neurochemie, Martinsried, Germany.
Cancer Res. 1993 Dec 1;53(23):5822-7.
We have recently shown that vascular endothelial growth factor (VEGF) is produced by human malignant glioma cells and acts on tumor endothelial cells, which express VEGF receptors, suggesting that VEGF is a regulator of tumor angiogenesis. To investigate the feasibility of antiangiogenic brain tumor therapy, we developed an intracerebral (i.c.) rat glioma model. We used two transplantable rat glioma cells lines, C6 and GS-9L, to analyze VEGF regulation in vitro and expression of VEGF and its high affinity tyrosine kinase receptors, flt-1 and flk-1, in vivo. Glioma cells were transplanted i.c. or s.c. into syngeneic rats. C6 gliomas exhibit morphological characteristics of human glioblastoma multiforme such as necroses with palisading cells. Immunocytochemistry with von Willebrand factor showed that C6 gliomas are highly vascularized and therefore show another prominent feature of human glioblastoma. GS-9L gliosarcomas were less vascularized. In situ hybridization showed that VEGF is expressed in vivo in rat glioma cells which reside along necrotic areas and therefore closely mimicks the expression pattern of VEGF observed in human glioblastoma. flt-1 and flk-1 are specifically expressed in endothelial cells in the tumor and at the border between tumor and normal brain but are absent from endothelial cells in the normal brain proper. The action of VEGF may therefore be restricted to tumor endothelium. Upregulation of VEGF, but not acid fibroblast growth factor, basic fibroblast growth factor, and platelet-derived growth factor B messenger RNA was observed in hypoxic C6 and GS-9L cells in vitro. These observations are consistent with a role for VEGF in tumor- and hypoxia-induced angiogenesis. Since the expression pattern of VEGF and its receptors in rat glioma appears to be indistinguishable from human glioblastoma multiforme, this model provides an excellent tool to study anti-angiogenic therapy.
我们最近发现，人恶性胶质瘤细胞可产生血管内皮生长因子（VEGF），并作用于表达VEGF受体的肿瘤内皮细胞，这表明VEGF是肿瘤血管生成的调节因子。为了研究抗血管生成脑肿瘤治疗的可行性，我们建立了大鼠脑内（i.c.）胶质瘤模型。我们使用两种可移植的大鼠胶质瘤细胞系C6和GS-9L，来体外分析VEGF的调节情况以及体内VEGF及其高亲和力酪氨酸激酶受体flt-1和flk-1的表达情况。将胶质瘤细胞脑内或皮下移植到同基因大鼠体内。C6胶质瘤呈现出多形性胶质母细胞瘤的形态特征，如伴有栅栏状细胞的坏死。用血管性血友病因子进行免疫细胞化学检测显示，C6胶质瘤血管高度丰富，因此呈现出多形性胶质母细胞瘤的另一个显著特征。GS-9L胶质肉瘤血管化程度较低。原位杂交显示，VEGF在大鼠胶质瘤细胞体内表达，这些细胞位于坏死区域周围，因此与在人多形性胶质母细胞瘤中观察到的VEGF表达模式极为相似。flt-1和flk-1在肿瘤内的内皮细胞以及肿瘤与正常脑的边界处特异性表达，但在正常脑实质的内皮细胞中不表达。因此，VEGF的作用可能仅限于肿瘤内皮。在体外低氧的C6和GS-9L细胞中，观察到VEGF上调，但酸性成纤维细胞生长因子、碱性成纤维细胞生长因子和血小板衍生生长因子B信使核糖核酸未上调。这些观察结果与VEGF在肿瘤和缺氧诱导的血管生成中的作用一致。由于大鼠胶质瘤中VEGF及其受体的表达模式似乎与人多形性胶质母细胞瘤无法区分，该模型为研究抗血管生成治疗提供了一个极好的工具。
