Vascular endothelial growth factor enhances endothelial cell survival and tumor radioresistance
Vascular endothelial growth factor enhances endothelial cell survival and tumor radioresistance
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DOI：
10.1097/00130404-200201000-00009
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发表时间：
2002-01-01
期刊：
影响因子：
2.2
通讯作者：
Weichselbaum, RR
中科院分区：
文献类型：
--
作者：
Gupta, VK;Jaskowiak, NT;Weichselbaum, RR
血管内皮生长因子（VEGF）是内皮细胞增殖和存活的重要介质。本研究的目的是探讨VEGF在肿瘤对电离辐射的反应中的作用。方法两个ras转化的鼠纤维肉瘤细胞系，VEGF+/+和VEGF-/-在体外暴露于电离辐射（0，1，3，5，7或9戈伊），并测定克隆形成生存。在无胸腺裸鼠中产生VEGF+/+和VEGF-/-异种移植物，然后用电离辐射处理（10次5-戈伊分次= 50戈伊）。平均肿瘤体积分数用于评价治疗疗效。为了确定VEGF是否通过靶向内皮细胞增强肿瘤的放射抗性，我们用人脐静脉内皮细胞进行了克隆形成存活测定。用电离辐射（5戈伊）和重组hVEGF 165（0、1、10和100 ng/mL）处理后计算存活分数。为了确定VEGF中和是否增强肿瘤放射敏感性，我们采用抗VEGF 165单克隆抗体治疗人肿瘤异种移植物。将肿瘤暴露于电离辐射（4次5-戈伊分次= 20戈伊）并用抗VEGF抗体处理（0、5和25 μg/kg，4次腹膜内剂量）。平均肿瘤体积分数用于评价治疗疗效。为了阐明所观察到的抗VEGF/电离辐射相互作用的分子机制，我们在抗VEGF抗体（1 μg/mL）存在下将人脐静脉内皮细胞暴露于电离辐射（5戈伊）。细胞裂解物的十二烷基硫酸钠聚丙烯酰胺凝胶电泳探测丝裂原活化蛋白激酶（MAPK）和MAPK激酶（MEK 1/MEK 2）。然而，VEGF+/+异种移植物比VEGF-/-异种移植物更能抵抗电离辐射的细胞毒性作用。VEGF+/+异种移植物表现出比VEGF-/-异种移植物更快的倍增时间（4.5 vs 6.0天）和更短的生长延迟（15 vs 23天）。在VEGF存在下，暴露于电离辐射后的人脐静脉内皮细胞的存活分数显著增加（6.4%对12.5%）。Western blot分析表明，MAPK和MEK 1/MEK 2的刺激被废除后，暴露于抗VEGF抗体。结论这些发现代表了第一个遗传证据，除了固有的肿瘤细胞放射敏感性的因素是放射治疗的重要决定因素。靶向VEGF和其他内皮细胞存活机制的抗肿瘤策略可用于增强放疗的细胞毒性作用。
PURPOSEVascular endothelial growth factor (VEGF) is an important mediator of endothelial cell proliferation and survival. The purpose of the present studies was to investigate the role of VEGF in the tumor response to ionizing radiation.METHODSTwo ras-transformed murinefibrosarcoma cell lines, VEGF+/+ and VEGF−/− were exposed to ionizing radiation (0, 1, 3, 5, 7 or 9 Gy) in vitro, and clonogenic survival was determined. VEGF+/+ and VEGF-\-xenografts were generated in athymic nude mice and then treated with ionizing radiation (ten 5-Gy fractions= 50 Gy). Mean fractional tumor volume was used to evaluate treatment efficacy. To determine whether VEGF enhances tumor radioresistance by targeting endothelial cells, we performed clonogenic survival assays with human umbilical vein endothelial cells. Surviving fractions were calculated after treatment with ionizing radiation (5 Gy) and recombinant hVEGF 165 (0, 1, 10, and 100 ng/mL). To determine whether VEGF neutralization enhances tumor radio-sensitivity, we employed anti-VEGF 165 monoclonal antibody to treat human tumor xenografts. Tumors were exposed to ionizing radiation (four 5-Gy fractions= 20 Gy) and treated with anti-VEGF antibody (0, 5, and 25 μg/kg in four intraperitoneal doses). Mean fractional tumor volume was used to evaluate treatment efficacy. To elucidate the molecular mechanism contributing to the observed anti-VEGF/ionizing radiation interaction, we exposed human umbilical vein endothelial cells to ionizing radiation (5 Gy) in the presence of anti-VEGF antibody (1 μg/mL). Sodium dodecyl sulfate polyacrylamide gel electrophoresis of cell lysates was probed for mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK1/MEK2).RESULTSThe in vitro radiosensitivities of the VEGF+/+ and VEGF−/− clones were equivalent (Do= 146 vs 149). However, the VEGF+/+ xenografts were more resistant to the cytotoxic effects of ionizing radiation than the VEGF−/− xenografts. VEGF+/+ xenografts demonstrated a faster doubling time (4.5 vs 6.0 days) and a shorter growth delay (15 vs 23 days) than VEGF−/− xenografts. The surviving fraction of human umbilical vein endothelial cells after exposure to ionizing radiation was significantly enhanced in the presence of VEGF (6.4% vs 12.5%). Western blot analysis demonstrated that stimulation of MAPK and MEK1/MEK2 was abrogated after exposure to anti-VEGF antibody.DISCUSSIONThese findings represent the first genetic evidence that factors other than inherent tumor cell radiosensitivity are important determinants of radiocurability. Antitumor strategies targeting VEGF and other endothelial cell survival mechanisms may be used to enhance the cytotoxic effects of radiotherapy.