RhoA regulates G1-S progression of gastric cancer cells by modulation of multiple INK4 family tumor suppressors.
RhoA, a member of the Rho GTPase family, has been extensively studied in the regulation of cytoskeletal dynamics, gene transcription, cell cycle progression, and cell transformation. Overexpression of RhoA is found in many malignancies and elevated RhoA activity is associated with proliferation phenotypes of cancer cells. We reported previously that RhoA was hyperactivated in gastric cancer tissues and suppression of RhoA activity could partially reverse the proliferation phenotype of gastric cancer cells, but the underlying mechanism has yet to be elucidated. It has been reported that RhoA activation is crucial for the cell cycle G(1)-S procession through the regulation of Cip/Kip family tumor suppressors in benign cell lines. In this study, we found that selective suppression of RhoA or its effectors mammalian Diaphanous 1 and Rho kinase (ROCK) by small interfering RNA and a pharmacologic inhibitor effectively inhibited proliferation and cell cycle G(1)-S transition in gastric cancer lines. Down-regulation of RhoA-mammalian Diaphanous 1 pathway, but not RhoA-ROCK pathway, caused an increase in the expression of p21(Waf1/Cip1) and p27(Kip1), which are coupled with reduced expression and activity of CDK2 and a cytoplasmic mislocalization of p27(Kip1). Suppression of RhoA-ROCK pathway, on the other hand, resulted in an accumulation of p15(INK4b), p16(INK4a), p18(INK4c), and p19(INK4d), leading to reduced expression and activities of CDK4 and CDK6. Thus, RhoA may use two distinct effector pathways in regulating the G(1)-S progression of gastric cancer cells.
Zhang
Siyuan
S
Sichuan University, Chengdu 610041, Sichuan Province, People's Republic of China.
Tang
Qiulin
Q
Xu
Feng
F
Xue
Yan
Y
Zhen
Zipeng
Z
Deng
Yu
Y
Liu
Ming
M
Chen
Ji
J
Liu
Surui
S
Qiu
Meng
M
Liao
Zhengyin
Z
Li
Zhiping
Z
Luo
Deyun
D
Shi
Fang
F
Zheng
Yi
Y
Bi
Feng
F
D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000235:genetics / Q000378:metabolism*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D050763:Cyclin-Dependent Kinase Inhibitor p18 / Q000235:genetics / Q000378:metabolism*; D050764:Cyclin-Dependent Kinase Inhibitor p19 / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase / Q000502:physiology*; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000502:physiology*; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology*; D013347:Subcellular Fractions; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
C493966:CDKN2B protein, human; C493971:CDKN2C protein, human; C493974:CDKN2D protein, human; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050764:Cyclin-Dependent Kinase Inhibitor p19; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C066737:RHOA protein, human; D020742:rhoA GTP-Binding Protein