Hayward Robert M, Kirk Melissa J, Sproull Mary, Scott Tamalee, Smith Sharon, Cooley-Zgela Theresa, Crouse Nancy S, Citrin Deborah E, Camphausen Kevin
Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892-1002, USA.
J Cell Mol Med. 2008 Jan-Feb;12(1):343-50. doi: 10.1111/j.1582-4934.2007.00135.x.
Angiogenesis, the development and recruitment of new blood vessels, plays an important role in tumour growth and metastasis. Vascular endothelial growth factor (VEGF) is an important stimulator of angiogenesis. Circulating and urinary VEGF levels have been suggested as clinically useful predictors of tumour behaviour, and investigations into these associations are ongoing. Despite recent interest in measuring VEGF levels in patients, little is known about the factors that influence VEGF levels in biospecimens. To begin to address this question, urine samples were collected from patients with solid tumours undergoing radiotherapy and healthy volunteers. Four factors were examined for their effects on VEGF concentrations as measured by chemiluminescent immunoassay: time from sample collection to freezing, number of specimen freeze-thaw cycles, specimen storage tube type and the inclusion or exclusion of urinary sediment. The results of this study indicate that time to freeze up to 4 hrs, number of freeze-thaw cycles between one and five, and different types of polypropylene tubes did not have statistically significant effects on measured urinary VEGF levels. Urinary sediment had higher VEGF levels than supernatant in five of six samples from healthy patients. It is not clear whether there is an active agent in the sediment causing this increase or if the sediment particles themselves are affecting the accuracy of the assay.Therefore, we recommend centrifuging urine, isolating the supernatant, and freezing the sample in polypropylene microcentrifuge tubes or cryogenic vials within 4 hrs of collection.In addition, we recommend the use of samples within five freeze-thaw cycles.
血管生成，即新血管的形成和募集，在肿瘤生长和转移中起着重要作用。血管内皮生长因子（VEGF）是血管生成的重要刺激因子。循环和尿液中的VEGF水平已被认为是肿瘤行为的临床有用预测指标，对此类关联的研究正在进行中。尽管最近人们对测量患者体内的VEGF水平很感兴趣，但对于影响生物样本中VEGF水平的因素却知之甚少。为了开始解决这个问题，我们收集了接受放疗的实体瘤患者和健康志愿者的尿液样本。通过化学发光免疫分析检测了四个因素对VEGF浓度的影响：从样本采集到冷冻的时间、样本冻融循环次数、样本储存管类型以及是否包含尿液沉淀物。本研究结果表明，长达4小时的冷冻时间、1至5次的冻融循环次数以及不同类型的聚丙烯管对所测尿液VEGF水平没有统计学上的显著影响。在健康患者的六个样本中的五个样本中，尿液沉淀物中的VEGF水平高于上清液。目前尚不清楚沉淀物中是否存在导致这种升高的活性剂，或者沉淀物颗粒本身是否影响检测的准确性。因此，我们建议对尿液进行离心，分离出上清液，并在采集后4小时内将样本冷冻在聚丙烯微量离心管或低温小瓶中。此外，我们建议在五个冻融循环内使用样本。
