Gprc5a deletion enhances the transformed phenotype in normal and malignant lung epithelial cells by eliciting persistent Stat3 signaling induced by autocrine leukemia inhibitory factor.
Gprc5a deletion enhances the transformed phenotype in normal and malignant lung epithelial cells by eliciting persistent Stat3 signaling induced by autocrine leukemia inhibitory factor.
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DOI：
10.1158/0008-5472.can-10-0518
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发表时间：
2010-11-01
期刊：
影响因子：
11.2
通讯作者：
Lotan R
中科院分区：
文献类型：
--
作者：
Chen Y;Deng J;Fujimoto J;Kadara H;Men T;Lotan D;Lotan R
信号转导和转录激活因子3(STAT3)在肺癌中由细胞因子和生长因子激活，调节与细胞生长、存活和转化有关的基因的表达。此前，我们发现G蛋白偶联受体，C家族，第5组，a成员(Gprc5a)基因缺失的小鼠发生肺肿瘤，表明Gprc5a是一种肿瘤抑制因子。在此，我们发现Gprc5a基因敲除小鼠肺上皮细胞(Gprc5a−/−细胞)在不含外源生长因子的培养液中能更好地存活，并在半固体培养中形成比野生型小鼠肺上皮细胞(Gprc5a+/+细胞)更多的集落。与Gprc5a+/+细胞相比，Gprc5a−/−中STAT3酪氨酸705的磷酸化水平和几个STAT3调控的抗凋亡基因的表达水平更高。两种细胞均分泌白血病抑制因子(LIF)，而STAT3在Gprc5a+/+−/−细胞中持续存在，在Gprc5a+/+细胞中是一过性的。从Gprc5a−/−小鼠分离的肺腺癌细胞也表现出自分泌Lif介导的STAT3激活。Gprc5a+/+细胞内源性STAT3抑制蛋白SOCS3的表达水平高于Gprc5a−/−细胞，肿瘤抑制基因SOCS3的表达稳定了SOCS3。JAK2抑制剂AG490或显性负性STAT3(Y705F)抑制Gprc5a−/−正常细胞和癌细胞中的STAT3信号转导增加饥饿诱导的细胞凋亡和抑制集落形成。这些结果表明，持续的STAT3激活对Gprc5a−/−肺癌细胞的存活和转化是重要的，并提示Gprc5a的抑瘤作用至少部分是通过稳定SOCS3来抑制STAT3信号的。
Signal transduction and activator of transcription 3 (Stat3) is activated by cytokines and growth factors in lung cancers and regulates expression of genes implicated in cell growth, survival, and transformation. Previously, we found that mice with a deletion of the G protein-coupled receptor, family C, group 5, member a (Gprc5a) gene develop lung tumors indicating that Gprc5a is a tumor suppressor. Herein, we show that epithelial cells from Gprc5a knockout mouse lung (Gprc5a−/− cells) survive better in vitro in medium deprived of exogenous growth factors and form more colonies in semi-solid medium than their counterparts from wildtype mice (Gprc5a+/+ cells). Stat3 Tyrosine 705 phosphorylation and expression of several Stat3-regulated anti-apoptotic genes were higher in Gprc5a−/− than in Gprc5a+/+ cells. Both cell types secreted Leukemia inhibitory factor (Lif), however, whereas Stat3 activation was persistent in Gprc5a−/− cells it was transient in Gprc5a+/+ cells. Lung adenocarcinoma cells isolated from Gprc5a−/− mice also exhibited autocrine Lif-mediated Stat3 activation. The level of Socs3, the endogenous Stat3 inhibitory protein, was higher in Gprc5a+/+ than in Gprc5a−/− cells and expression of the tumor suppressor stabilized Socs3. Inhibition of Stat3 signaling in Gprc5a−/− normal and cancer cells by the Jak2 inhibitor AG490 or by a dominant negative Stat3(Y705F) increased starvation-induced apoptosis and inhibited colony formation. These results demonstrate that persistent Stat3 activation is important for the survival and transformation of Gprc5a−/− lung cells and suggest that the tumor suppressive effects of Gprc5a are mediated, at least in part, by inhibition of Stat3 signaling via Socs3 stabilization.