Aberrant nuclear accumulation of glycogen synthase kinase-3beta in human pancreatic cancer: association with kinase activity and tumor dedifferentiation.
OBJECTIVE
We have shown recently that glycogen synthase kinase-3 (GSK-3) beta regulates nuclear factor-kappaB (NF-kappaB)-mediated pancreatic cancer cell survival and proliferation in vitro. Our objective was to determine the localization of GSK-3beta in pancreatic cancer cells and assess the antitumor effect of GSK-3 inhibition in vivo to improve our understanding of the mechanism by which GSK-3beta affects NF-kappaB activity in pancreatic cancer.


METHODS
Immunohistochemistry and cytosolic/nuclear fractionation were done to determine the localization of GSK-3beta in human pancreatic tumors. We studied the effect of GSK-3 inhibition on tumor growth, cancer cell proliferation, and survival in established CAPAN2 tumor xenografts using a tumor regrowth delay assay, Western blotting, bromodeoxyuridine incorporation, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling.


RESULTS
We found nuclear accumulation of GSK-3beta in pancreatic cancer cell lines and in 62 of 122 (51%) human pancreatic adenocarcinomas. GSK-3beta nuclear accumulation is significantly correlated with human pancreatic cancer dedifferentiation. We have found that active GSK-3beta can accumulate in the nucleus of pancreatic cancer cells and that inhibition of GSK-3 kinase activity represses its nuclear accumulation via proteasomal degradation within the nucleus. Lastly, we have found that inhibition of GSK-3 arrests pancreatic tumor growth in vivo and decreases NF-kappaB-mediated pancreatic cancer cell survival and proliferation in established tumor xenografts.


CONCLUSIONS
Our results show the antitumor effect of GSK-3 inhibition in vivo, identify GSK-3beta nuclear accumulation as a hallmark of poorly differentiated pancreatic adenocarcinoma, and provide new insight into the mechanism by which GSK-3beta regulates NF-kappaB activity in pancreatic cancer.
Ougolkov
Andrei V
AV
Division of Oncology Research, Gastrointestinal Unit, Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Fernandez-Zapico
Martin E
ME
Bilim
Vladimir N
VN
Smyrk
Thomas C
TC
Chari
Suresh T
ST
Billadeau
Daniel D
DD
D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology* / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D015996:Survival Rate; D013844:Thiazoles / Q000008:administration & dosage / Q000494:pharmacology; D014183:Transplantation, Heterologous; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
D016328:NF-kappa B; D013844:Thiazoles; 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