Crosstalk between the urokinase-type plasminogen activator receptor and EGF receptor variant III supports survival and growth of glioblastoma cells
Crosstalk between the urokinase-type plasminogen activator receptor and EGF receptor variant III supports survival and growth of glioblastoma cells
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DOI：
10.1073/pnas.1113416108
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发表时间：
2011-09-20
影响因子：
11.1
通讯作者：
Gonias, Steven L.
中科院分区：
文献类型：
--
作者：
Hu, Jingjing;Jo, Minji;Gonias, Steven L.
EGF受体的截短和组成型活性形式，变体III（EGFRvIII），是多形性胶质母细胞瘤（GBM）中肿瘤生长和进展的主要决定因素。广泛的双向串扰发生在EGFR和尿激酶型纤溶酶原激活物受体（uPAR）下游的细胞信号转导通路中;然而，EGFRvIII和uPAR之间的串扰尚未得到研究。在这里，我们表明，uPAR不调节ERK激活EGFRvIII表达GBM细胞，然而，在GBM细胞分离的四个单独的异种移植物中，EGFRvIII表达下调体内，uPAR承担了维持ERK激活的主要作用。在表达EGFRvIII的GBM细胞中，由Src家族激酶介导的EGFR中Tyr-845的磷酸化依赖于uPAR。EGFRvIII下游的促有丝分裂和促存活转录因子STAT 5 b的激活也需要uPAR。EGFR选择性酪氨酸激酶抑制剂厄洛替尼和吉非替尼不仅阻断EGFRvIII向ERK的信号传导，而且阻断uPAR依赖性STAT 5 b活化。在表达EGFRvIII的GBM细胞和来自逃避对EGFRvIII依赖的肿瘤细胞中，uPAR基因沉默降低了细胞存活和增殖。表达EGFRvIII的癌细胞系和作为异种移植物繁殖的人GBM的异种移植物通过免疫组织化学对uPAR和磷酸-Tyr-845呈强免疫阳性。EGFR基因扩增而未截短的人GBM对uPAR和磷酸-Tyr-845均呈免疫阴性。这些研究确定了表达EGFRvIII的GBM细胞和EGFRvIII被中和时从休眠释放的细胞中uPAR的不同细胞信号传导活性。uPAR及其与EGFRvIII的串扰途径成为GBM治疗开发的逻辑靶点。
A truncated and constitutively active form of the EGF receptor, variant III (EGFRvIII), is a major determinant of tumor growth and progression in glioblastoma multiforme (GBM). Extensive bidirectional crosstalk occurs in the cell-signaling pathways downstream of the EGFR and the urokinase-type plasminogen activator receptor (uPAR); however, crosstalk between EGFRvIII and uPAR has not been examined. Here, we show that uPAR does not regulate ERK activation in EGFRvIII-expressing GBM cells; however, in GBM cells isolated from four separate xenografts in which EGFRvIII expression was down-regulated in vivo, uPAR assumed a major role in sustaining ERK activation. Phosphorylation of Tyr-845 in the EGFR, which is mediated by Src family kinases, depended on uPAR in EGFRvIII-expressing GBM cells. Activation of the mitogenic and prosurvival transcription factor, STAT5b, downstream of EGFRvIII, also required uPAR. The EGFR-selective tyrosine kinase inhibitors, erlotinib and gefitinib, blocked not only EGFRvIII signaling to ERK but also uPAR-dependent STAT5b activation. uPAR gene silencing in EGFRvIII-expressing GBM cells and in cells from tumors that escaped dependency on EGFRvIII decreased cell survival and proliferation. Xenografts of EGFRvIII-expressing cancer cell lines and a human GBM, which was propagated as a xenograft, were robustly immunopositive for uPAR and phospho-Tyr-845 by immunohistochemistry. A human GBM in which the EGFR gene was amplified without truncation was immunonegative for both uPAR and phospho-Tyr-845. These studies identify distinct cell-signaling activities for uPAR in GBM cells that express EGFRvIII and in cells released from dormancy when EGFRvIII is neutralized. uPAR and its crosstalk pathways with EGFRvIII emerge as logical targets for therapeutics development in GBM.