Deregulated GSK3{beta} sustains gastrointestinal cancer cells survival by modulating human telomerase reverse transcriptase and telomerase.
OBJECTIVE
Glycogen synthase kinase-3beta (GSK3beta) regulates multiple cell signaling pathways and has been implicated in glucose intolerance, neurodegenerative disorders, and inflammation. We investigated the expression, activity, and putative pathologic role of GSK3beta in gastrointestinal, pancreatic, and liver cancers.


METHODS
Colon, stomach, pancreatic, and liver cancer cell lines; nonneoplastic HEK293 cells; and matched pairs of normal and tumor tissues of stomach and colon cancer patients were examined for GSK3beta expression and its phosphorylation at serine 9 (inactive form) and tyrosine 216 (active form) by Western immunoblotting and for GSK3beta activity by in vitro kinase assay. The effects of small-molecule GSK3beta inhibitors and of RNA interference on cell survival, proliferation, and apoptosis were examined in vitro and on human colon cancer cell xenografts in athymic mice. The effects of GSK3beta inhibition on human telomerase reverse transcriptase (hTERT) expression and telomerase activity were compared between colon cancer and HEK293 cells.


RESULTS
Cancer cell lines and most cancer tissues showed increased GSK3beta expression and increased tyrosine 216 phosphorylation and activity but decreased serine 9 phosphorylation compared with HEK293 cells and nonneoplastic tissues. Inhibition of GSK3beta resulted in attenuated cell survival and proliferation and increased apoptosis in most cancer cell lines and in HT-29 xenografts in rodents but not in HEK293 cells. GSK3beta inhibition in colon cancer cells was associated with decreased hTERT expression and telomerase activity.


CONCLUSIONS
The results indicate that deregulated GSK3beta sustains gastrointestinal cancer cells survival through modulation of hTERT and telomerase.
Mai
Wei
W
Division of Translational and Clinical Oncology, Cancer Research Institute, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan.
Kawakami
Kazuyuki
K
Shakoori
Abbas
A
Kyo
Satoru
S
Miyashita
Katsuyoshi
K
Yokoi
Kenji
K
Jin
Mingji
M
Shimasaki
Takeo
T
Motoo
Yoshiharu
Y
Minamoto
Toshinari
T
D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D016922:Cellular Senescence; D005770:Gastrointestinal Neoplasms / Q000201:enzymology* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000096:biosynthesis*; D006801:Humans; D051379:Mice; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D015398:Signal Transduction; D019098:Telomerase / Q000096:biosynthesis*
D038362:Glycogen Synthase Kinase 3; C509186:TERT protein, human; D019098:Telomerase