Oncotarget

Research Papers:

Chronic TGFβ stimulation promotes the metastatic potential of lung cancer cells by Snail protein stabilization through integrin β3-Akt-GSK3β signaling

Gab-Yong Bae, Soon-Ki Hong, Jeong-Rak Park, Ok-Seon Kwon, Keun-Tae Kim, JaeHyung Koo, Ensel Oh and Hyuk-Jin Cha _

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Oncotarget. 2016; 7:25366-25376. https://doi.org/10.18632/oncotarget.8295

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Abstract

Gab-Yong Bae1,*, Soon-Ki Hong1,*, Jeong-Rak Park1, Ok-Seon Kwon1, Keun-Tae Kim1, JaeHyung Koo2, Ensel Oh3, Hyuk-Jin Cha1

1College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea

2Department of Brain and Cognitive Sciences, DGIST, Daegu, Republic of Korea

3Laboratory of Cancer Genomics and Molecular Pathology, Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Republic of Korea

*These authors have contributed equally to this work

Correspondence to:

Hyuk-Jin Cha, e-mail: [email protected]

Gab-Yong Bae, e-mail: [email protected]

Keywords: chronic TGFβ exposure, integrin β3, Akt, GSK3β, Snail

Received: December 23, 2015     Accepted: March 07, 2016     Published: March 23, 2016

ABSTRACT

Chronic exposure to TGFβ, a frequent occurrence for tumor cells in the tumor microenvironment, confers more aggressive phenotypes on cancer cells by promoting their invasion and migration while at the same time increasing their resistance to the growth-inhibitory effect of TGFβ. In this study, a transdifferentiated (TD) A549 cell model, established by chronically exposing A549 cells to TGFβ, showed highly invasive phenotypes in conjunction with attenuation of Smad-dependent signaling. We show that Snail protein, the mRNA expression of which strongly correlates with a poor prognosis in lung cancer patients, was highly stable in TD cells after TGFβ stimulation. The increased protein stability of Snail in TD cells correlated with elevated inhibitory phosphorylation of GSK3β, resulting from the high Akt activity. Notably, integrin β3, whose expression was markedly increased upon sustained exposure to TGFβ, was responsible for the high Akt activity as well as the increased Snail protein stability in TD cells. Consistently, clinical database analysis on lung cancer patients revealed a negative correlation between overall survival and integrin β3 mRNA levels. Therefore, we suggest that the integrin β3-Akt-GSK3β signaling axis plays an important role in non-canonical TGFβ signaling, determining the invasive properties of tumor cells chronically exposed to TGFβ.


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