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Gprc5a deletion enhances the transformed phenotype in normal and malignant lung epithelial cells by eliciting persistent Stat3 signaling induced by autocrine leukemia inhibitory factor.

Abstract：

:Signal transducers and activators 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 semisolid medium than their counterparts from wild-type mice (Gprc5a(+/+) cells). Stat3 tyrosine 705 phosphorylation and expression of several Stat3-regulated antiapoptotic 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 Janus-activated kinase 2 inhibitor AG490 or by a dominant negative Stat3(Y705F) increased starvation-induced apoptosis and inhibited colony formation. These results show 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 through Socs3 stabilization.

journal_name

Cancer Res

journal_title

Cancer research

authors

Chen Y,Deng J,Fujimoto J,Kadara H,Men T,Lotan D,Lotan R

doi

10.1158/0008-5472.CAN-10-0518

subject

Has Abstract

pub_date

2010-11-01 00:00:00

pages

8917-26

issue

eissn

0008-5472

issn

1538-7445

pii

0008-5472.CAN-10-0518

journal_volume

pub_type

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Gprc5a deletion enhances the transformed phenotype in normal and malignant lung epithelial cells by eliciting persistent Stat3 signaling induced by autocrine leukemia inhibitory factor.