title: P27(Kip1), regulated by glycogen synthase kinase-3β, results in HMBA-induced differentiation of human gastric cancer cells.
abstract: BACKGROUND
  Gastric cancer is the second most common cause of global cancer-related mortality. Although dedifferentiation predicts poor prognosis in gastric cancer, the molecular mechanism underlying dedifferentiation, which could provide fundamental insights into tumor development and progression, has yet to be elucidated. Furthermore, the molecular mechanism underlying the effects of hexamethylene bisacetamide (HMBA), a recently discovered differentiation inducer, requires investigation and there are no reported studies concerning the effect of HMBA on gastric cancer.
  
  
  METHODS
  Based on the results of FACS analysis, the levels of proteins involved in the cell cycle or apoptosis were determined using western blotting after single treatments and sequential combinations of HMBA and LiCl. GSK-3β and proton pump were investigated by western blotting after up-regulating Akt expression by Ad-Akt infection. To investigate the effects of HMBA on protein localization and the activities of GSK-3β, CDK2 and CDK4, kinase assays, immunoprecipitation and western blotting were performed. In addition, northern blotting and RNase protection assays were carried out to determine the functional concentration of HMBA.
  
  
  RESULTS
  HMBA increased p27(Kip1) expression and induced cell cycle arrest associated with gastric epithelial cell differentiation. In addition, treating gastric-derived cells with HMBA induced G0/G1 arrest and up-regulation of the proton pump, a marker of gastric cancer differentiation. Moreover, treatment with HMBA increased the expression and activity of GSK-3β in the nucleus but not the cytosol. HMBA decreased CDK2 activity and induced p27(Kip1) expression, which could be rescued by inhibition of GSK-3β. Furthermore, HMBA increased p27(Kip1) binding to CDK2, and this was abolished by GSK-3β inhibition.
  
  
  CONCLUSIONS
  The results presented herein suggest that GSK-3β functions by regulating p27(Kip1) assembly with CDK2, thereby playing a critical role in G0/G1 arrest associated with HMBA-induced gastric epithelial cell differentiation.
authors: Key Laboratory of Shanghai Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China. liubyrj@yahoo.com.cn
authors: Min
authors: M
authors: Wei
authors: Zhiwei
authors: Z
authors: Wang
authors: Hongliang
authors: H
authors: Yao
authors: Zhongyin
authors: Z
authors: Yang
authors: Qing
authors: Q
authors: Zhang
authors: Bingya
authors: B
authors: Liu
authors: Yingyan
authors: Y
authors: Yu
authors: Liping
authors: L
authors: Su
authors: Zhenggang
authors: Z
authors: Zhu
authors: Qinlong
authors: Q
authors: Gu
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000627:Aminophenols; D000970:Antineoplastic Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008301:Maleimides; D017494:Proton Pumps / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology
chemical_list: C417520:3-(3-chloro-4-hydroxyphenylamino)-4-(4-nitrophenyl)-1H-pyrrole-2,5-dione; D000081:Acetamides; D000627:Aminophenols; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D008301:Maleimides; D017494:Proton Pumps; D050760:Cyclin-Dependent Kinase Inhibitor p27; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051357:Cyclin-Dependent Kinase 2; D038362:Glycogen Synthase Kinase 3; C014026:hexamethylene bisacetamide