Homozygous deletion of glycogen synthase kinase 3beta bypasses senescence allowing Ras transformation of primary murine fibroblasts.
In primary mammalian cells, expression of oncogenes such as activated Ras induces premature senescence rather than transformation. We show that homozygous deletion of glycogen synthase kinase (GSK) 3beta (GSK3beta-/-) bypasses senescence induced by mutant Ras(V12) allowing primary mouse embryo fibroblasts (MEFs) as well as immortalized MEFs to exhibit a transformed phenotype in vitro and in vivo. Both catalytic activity and Axin-binding of GSK3beta are required to optimally suppress Ras transformation. The expression of Ras(V12) in GSK3beta-/-, but not in GSK3beta+/+ MEFs results in translocation of beta-catenin to the nucleus with concomitant up-regulation of cyclin D1. siRNA-mediated knockdown of beta-catenin decreases both cyclin D1 expression and anchorage-independent growth of transformed cells indicating a causal role for beta-catenin. Thus Ras(V12) and the lack of GSK3beta act in concert to activate the beta-catenin pathway, which may underlie the bypass of senescence and tumorigenic transformation by Ras.
Liu
Shuying
S
Department of Systems Biology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Fang
Xianjun
X
Hall
Hassan
H
Yu
Shuangxing
S
Smith
Debra
D
Lu
Zhimin
Z
Fang
Dexing
D
Liu
Jinsong
J
Stephens
L Clifton
LC
Woodgett
James R
JR
Mills
Gordon B
GB
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002384:Catalysis; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D019938:Cyclin D1 / Q000378:metabolism; D005347:Fibroblasts; D017353:Gene Deletion; D005786:Gene Expression Regulation; D038362:Glycogen Synthase Kinase 3 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006720:Homozygote; D051379:Mice; D018345:Mice, Knockout; D019076:Transgenes / Q000235:genetics*; D051176:beta Catenin / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D051176:beta Catenin; D019938:Cyclin D1; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D018631:ras Proteins