title: Glycogen synthase kinase 3β inhibition sensitizes pancreatic cancer cells to gemcitabine.
abstract: BACKGROUND
  Pancreatic cancer is obstinate and resistant to gemcitabine, a standard chemotherapeutic agent for the disease. We previously showed a therapeutic effect of glycogen synthase kinase-3β (GSK3β) inhibition against gastrointestinal cancer and glioblastoma. Here, we investigated the effect of GSK3β inhibition on pancreatic cancer cell sensitivity to gemcitabine and the underlying molecular mechanism.
  
  
  METHODS
  Expression, phosphorylation, and activity of GSK3β in pancreatic cancer cells (PANC-1) were examined by Western immunoblotting and in vitro kinase assay. The combined effect of gemcitabine and a GSK3β inhibitor (AR-A014418) against PANC-1 cells was examined by isobologram and PANC-1 xenografts in mice. Changes in gene expression in PANC-1 cells following GSK3β inhibition were studied by cDNA microarray and reverse transcription (RT)-PCR.
  
  
  RESULTS
  PANC-1 cells showed increased GSK3β expression, phosphorylation at tyrosine 216 (active form), and activity compared with non-neoplastic HEK293 cells. Administration of AR-A014418 at pharmacological doses attenuated proliferation of PANC-1 cells and xenografts, and significantly sensitized them to gemcitabine. Isobologram analysis determined that the combined effect was synergistic. DNA microarray analysis detected GSK3β inhibition-associated changes in gene expression in gemcitabine-treated PANC-1 cells. Among these changes, RT-PCR and Western blotting showed that expression of tumor protein 53-induced nuclear protein 1, a gene regulating cell death and DNA repair, was increased by gemcitabine treatment and substantially decreased by GSK3β inhibition.
  
  
  CONCLUSIONS
  The results indicate that GSK3β inhibition sensitizes pancreatic cancer cells to gemcitabine with altered expression of genes involved in DNA repair. This study provides insight into the molecular mechanism of gemcitabine resistance and thus a new strategy for pancreatic cancer chemotherapy.
authors: Department of Medical Oncology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293, Japan. takeo@kanazawa-med.ac.jp
authors: Takeo
authors: T
authors: Shimasaki
authors: Yasuhito
authors: Y
authors: Ishigaki
authors: Yuka
authors: Y
authors: Nakamura
authors: Takanobu
authors: T
authors: Takata
authors: Naoki
authors: N
authors: Nakaya
authors: Hideo
authors: H
authors: Nakajima
authors: Itaru
authors: I
authors: Sato
authors: Xia
authors: X
authors: Zhao
authors: Ayako
authors: A
authors: Kitano
authors: Kazuyuki
authors: K
authors: Kawakami
authors: Takuji
authors: T
authors: Tanaka
authors: Tsutomu
authors: T
authors: Takegami
authors: Naohisa
authors: N
authors: Tomosugi
authors: Toshinari
authors: T
authors: Minamoto
authors: Yoshiharu
authors: Y
authors: Motoo
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004260:DNA Repair / Q000187:drug effects; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D019008:Drug Resistance, Neoplasm; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors*; D000071679:Glycogen Synthase Kinase 3 beta; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020411:Oligonucleotide Array Sequence Analysis; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013844:Thiazoles / Q000008:administration & dosage; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
chemical_list: D013844:Thiazoles; D003841:Deoxycytidine; C479831:N-(4-methoxybenzyl)-N'-(5-nitro-1,3-thiazol-2-yl)urea; D014508:Urea; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D000093542:Gemcitabine