title: Chronic TGFβ stimulation promotes the metastatic potential of lung cancer cells by Snail protein stabilization through integrin β3-Akt-GSK3β signaling.
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.
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Gab-Yong
authors.initials: GY
authors.lastname: Bae
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Soon-Ki
authors.initials: SK
authors.lastname: Hong
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Jeong-Rak
authors.initials: JR
authors.lastname: Park
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Ok-Seon
authors.initials: OS
authors.lastname: Kwon
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Keun-Tae
authors.initials: KT
authors.lastname: Kim
authors.affiliation: Department of Brain and Cognitive Sciences, DGIST, Daegu, Republic of Korea.
authors.forename: JaeHyung
authors.initials: J
authors.lastname: Koo
authors.affiliation: Laboratory of Cancer Genomics and Molecular Pathology, Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Republic of Korea.
authors.forename: Ensel
authors.initials: E
authors.lastname: Oh
authors.affiliation: College of Natural Sciences, Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors.forename: Hyuk-Jin
authors.initials: HJ
authors.lastname: Cha
mesh_terms: D000072283:A549 Cells; D000230:Adenocarcinoma / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism; D006801:Humans; D039661:Integrin beta3 / Q000378:metabolism; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D009361:Neoplasm Invasiveness / Q000473:pathology; D011379:Prognosis; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071250:Snail Family Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D039661:Integrin beta3; D000071250:Snail Family Transcription Factors; D016212:Transforming Growth Factor beta; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt
keywords: Akt; GSK3β; Snail; chronic TGFβ exposure; integrin β3