Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
Lab Invest. 2010 May;90(5):709-23. doi: 10.1038/labinvest.2010.52. Epub 2010 Mar 1.
Human epithelial ovarian cancer (EOC) is the most lethal neoplasm affecting the female genital tract, and is characterized by overexpression of vascular endothelial growth factor (VEGF) and growth as ascites. Anti-VEGF strategies are currently used in EOC therapy with promising results; however, molecular targeting of specific VEGF receptors on the cancer cells themselves has not been explored to date. We previously showed that activation of a VEGF/VEGFR2 signaling loop in EOC cells supports their survival in suspension, and short-term pharmacological inhibition of this loop increased EOC cell apoptosis in vitro. In this study, we stably knocked down VEGFR2 in OVCAR-3 and SKOV-3 EOC cells using short hairpin RNA (shRNA), an RNA interference strategy that could potentially overcome chemoresistance arising with angiogenic inhibitors. Unexpectedly, we observed an induction of more aggressive cellular behavior in transfected cells, leading to increased growth in mouse xenografts, enhanced accumulation of ascites, increased VEGF and neuropilin-1 (NRP-1) expression, and decreased expression of adhesion proteins, notably cadherins and integrins. Sonic hedgehog (SHH) pathways do not seem to be involved in the upregulation of NRP-1 message in VEGFR2 knockdown cells. Supporting our mouse model, we also found a significant increase in the ratio between NRP-1 and VEGFR2 with increasing tumor grade in 80 cases of human EOC. The change in EOC behavior that we report in this study occurred independent of the angiogenic response and shows the direct effect of VEGF blockade on the cancer cells themselves. Our findings highlight the possible confounding events that may affect the usefulness of RNAi in a therapeutic setting for disrupting EOC cell survival in ascites.
人上皮性卵巢癌 (EOC) 是最致命的影响女性生殖道的肿瘤，其特征是血管内皮生长因子 (VEGF) 过表达和腹水生长。目前在 EOC 治疗中使用抗 VEGF 策略取得了有希望的结果；然而，迄今为止尚未探索针对癌细胞自身特定 VEGF 受体的分子靶向治疗。我们之前的研究表明，EOC 细胞中 VEGF/VEGFR2 信号通路的激活支持它们在悬浮状态下的存活，并且该通路的短期药理学抑制增加了体外 EOC 细胞的凋亡。在这项研究中，我们使用短发夹 RNA (shRNA) 稳定敲低了 OVCAR-3 和 SKOV-3 EOC 细胞中的 VEGFR2，这是一种 RNA 干扰策略，可能克服与血管生成抑制剂相关的耐药性。出乎意料的是，我们观察到转染细胞中诱导出更具侵袭性的细胞行为，导致在小鼠异种移植中生长增加、腹水积聚增加、VEGF 和神经纤毛蛋白-1 (NRP-1) 表达增加以及粘附蛋白表达减少，尤其是钙粘蛋白和整合素。SHH 途径似乎不参与 VEGFR2 敲低细胞中 NRP-1 信使的上调。支持我们的小鼠模型，我们还发现 80 例人 EOC 中肿瘤分级越高，NRP-1 与 VEGFR2 的比值显著增加。我们在这项研究中报告的 EOC 行为的变化独立于血管生成反应，显示了 VEGF 阻断对癌细胞本身的直接影响。我们的研究结果强调了在使用 RNAi 干扰破坏腹水肿瘤细胞存活的治疗环境中可能影响其有用性的潜在混杂事件。
