Department of Urology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095-1738, USA.
Cancer Res. 2010 Jan 15;70(2):752-61. doi: 10.1158/0008-5472.CAN-09-2211. Epub 2010 Jan 12.
The critical downstream signaling consequences contributing to renal cancer as a result of loss of the tumor suppressor gene von Hippel-Lindau (VHL) have yet to be fully elucidated. Here, we report that VHL loss results in an epithelial to mesenchymal transition (EMT). In studies of paired isogenic cell lines, VHL silencing increased the levels of N-cadherin and vimentin and reduced the levels of E-cadherin relative to the parental VHL(+) cell line, which displayed the opposite profile. VHL(+) cells grew as clusters of cuboidal and rhomboid cells, whereas VHL-silenced cells took on an elongated, fibroblastoid morphology associated with a more highly invasive character in Matrigel chamber assays. Based on earlier evidence that VHL loss can activate NF-kappaB, a known mediator of EMT, we tested whether NF-kappaB contributed to VHL-mediated effects on EMT. On pharmacologic or molecular inhibition of NF-kappaB, VHL-silenced cells regained expression of E-cadherin, lost expression of N-cadherin, and reversed their highly invasive phenotype. Introducing a pVHL-resistant hypoxia-inducible factor 1alpha (HIF1alpha) mutant (HIFalpha(M)) into VHL(+) cells heightened NF-kappaB activity, phenocopying EMT effects produced by VHL silencing. Conversely, inhibiting the heightened NF-kappaB activity in this setting reversed the EMT phenotype. Taken together, these results suggest that VHL loss induces an EMT that is largely dependent on HIFalpha-induced NF-kappaB. Our findings rationalize targeting the NF-kappaB pathway as a therapeutic strategy to treat renal tumors characterized by biallelic VHL inactivation.
导致肾细胞癌的抑癌基因 von Hippel-Lindau (VHL) 缺失的关键下游信号转导后果尚未完全阐明。在这里，我们报告 VHL 缺失导致上皮-间充质转化 (EMT)。在对配对同基因细胞系的研究中，VHL 沉默导致 N-钙粘蛋白和波形蛋白的水平增加，而与亲本 VHL(+)细胞系相比，E-钙粘蛋白的水平降低，VHL(+)细胞呈立方和菱形细胞簇生长，而 VHL 沉默的细胞呈拉长的成纤维细胞样形态，与 Matrigel 室测定中更高的侵袭特性相关。基于先前的证据表明 VHL 缺失可以激活 NF-κB，这是 EMT 的已知介质，我们测试了 NF-κB 是否有助于 VHL 介导的 EMT 效应。通过药理学或分子抑制 NF-κB，VHL 沉默的细胞重新表达 E-钙粘蛋白，失去 N-钙粘蛋白的表达，并逆转其高侵袭表型。将 pVHL 抗性缺氧诱导因子 1alpha (HIF1alpha) 突变体 (HIFalpha(M)) 引入 VHL(+) 细胞会增加 NF-κB 活性，模拟由 VHL 沉默产生的 EMT 效应。相反，在这种情况下抑制 NF-κB 的活性增强会逆转 EMT 表型。总之，这些结果表明 VHL 缺失诱导 EMT，这在很大程度上依赖于 HIFalpha 诱导的 NF-κB。我们的发现合理地将 NF-κB 途径作为治疗策略的靶点，用于治疗由双等位 VHL 失活引起的肾肿瘤。
