Cancer Res.:肿瘤缺氧途径研究新模型

6月4日Cancer Research杂志在线报道了一种新开发的缺氧感受信号通路斑马鱼体内研究系统，为深入研究缺氧在肿瘤中作用提供了有力的新手段。

缺氧信号通路是肿瘤细胞病理过程的核心调控者。过去对氧浓度感受途径的关键因子von Hippel-Lindau肿瘤抑制蛋白（pVHL）以及HIF转录因子虽然研究得很多，但是还需要加强在生物模型中对缺氧途径的研究，以加深人类对肿瘤病理的理解，促进新治疗手段的研发。

为此，研究者试图用斑马鱼模式生物研究HIF信号通路在肿瘤起源和发展中的作用。他们开发出一种独特的体内缺氧报告系统，可在缺氧诱导因子脯氨酰羟化酶3（phd3）启动/调节元件的驱动下表达EGFP。在Tg(phd3::EGFP)斑马鱼胚胎中的研究显示，斑马鱼vhl突变体表现出系统性的缺氧反应。在缺氧反应途径成员脯氨酰羟化酶3（phd3）启动/调节元件驱动下，转基因EGFP呈现强烈而广泛的表达。

与人类VHL患者不同的是，杂合子Vhl小鼠和vhl斑马鱼均未表现对肿瘤的特殊易感性。然而，在暴露于化学致癌剂二甲基苯并蒽（DMBA）情况下，vhl杂合子斑马鱼的肝及肠道肿瘤的发生率上升了。而且，其中部分肿瘤细胞呈现较强的EGFP表达，提示Vhl在其中的功能丢失。与对照组相比，DMBA处理的vhl杂合子斑马鱼在肾小管中增殖细胞核抗原阳性率也增加了。

总之，该研究证实了Vhl在斑马鱼模型中确为肿瘤抑制因子，并为非损伤性研究VHL和HIF信号通路在肿瘤发生和发展中的作用通过了可靠的模型。

doi:10.1016/j.cell.2011.10.017
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A zebrafish model to study and therapeutically manipulate hypoxia signaling in tumorigenesis

Kirankumar Santhakumar1, Emma C Judson1, Philip M Elks1, Sarah McKee1, Stone Elworthy1, Ellen van Rooijen2, Sarah S Walmsley3, Stephen Renshaw4, Simon S. Cross5, and Fredericus JM van Eeden6,*

Abstract

Hypoxic signaling is a central modulator of cellular physiology in cancer. Core members of oxygen sensing pathway including the von Hippel-Lindau tumor suppressor protein (pVHL) and the HIF transcription factors have been intensively studied, but improved organismal models might speed advances for both pathobiological understanding and therapeutic modulation. To study HIF signaling during tumorigenesis and development in zebrafish, we developed a unique in vivo reporter for hypoxia, expressing EGFP driven by prolyl hydroxylase 3 (phd3) promoter/regulatory elements. Modulation of HIF pathway in Tg(phd3::EGFP) embryos showed a specific role for hypoxic signaling in the transgene activation. Zebrafish vhl mutants display a systemic hypoxia response, reflected by strong and ubiquitous transgene expression. In contrast to human VHL patients, heterozygous Vhl mice and vhl zebrafish are not predisposed to cancer. However, upon exposure to dimethylbenzanthracene (DMBA), the vhl heterozygous fish showed an increase in the occurrence of hepatic and intestinal tumors, a subset of which exhibited strong transgene expression, suggesting loss of Vhl function in these tumor cells. Compared to control fish, DMBA-treated vhl heterozygous fish also showed an increase in proliferating cell nuclear antigen positive renal tubules. Taken together, our findings establish Vhl as a genuine tumor suppressor in zebrafish and offer this model as a tool to non-invasively study VHL and HIF signaling during tumorigenesis and development.