GSK3beta and beta-catenin modulate radiation cytotoxicity in pancreatic cancer.
BACKGROUND
Knowledge of factors and mechanisms contributing to the inherent radioresistance of pancreatic cancer may improve cancer treatment. Irradiation inhibits glycogen synthase kinase 3beta (GSK3beta) by phosphorylation at serine 9. In turn, release of cytosolic membrane beta-catenin with subsequent nuclear translocation promotes survival. Both GSK3beta and beta-catenin have been implicated in cancer cell proliferation and resistance to death.


METHODS
We investigated pancreatic cancer cell survival after radiation in vitro and in vivo, with a particular focus on the role of the function of the GSK3beta/beta-catenin axis.


RESULTS
Lithium chloride, RNAi-medicated silencing of GSK3beta, or the expression of a kinase dead mutant GSK3beta resulted in radioresistance of Panc1 and BxPC3 pancreatic cancer cells. Conversely, ectopic expression of a constitutively active form of GSK3beta resulted in radiosensitization of Panc1 cells. GSK3beta silencing increased radiation-induced beta-catenin target gene expression as measured by studies of AXIN2 and LEF1 transcript levels. Western blot analysis of total and phosphorylated levels of GSK3beta and beta-catenin showed that GSK3beta inhibition resulted in stabilization of beta-catenin. Xenografts of both BxPC3 and Panc1 with targeted silencing of GSK3beta exhibited radioresistance in vivo. Silencing of beta-catenin resulted in radiosensitization, whereas a nondegradable beta-catenin construct induced radioresistance.


CONCLUSIONS
These data support the hypothesis that GSK3beta modulates the cellular response to radiation in a beta-catenin-dependent mechanism. Further understanding of this pathway may enhance the development of clinical trials combining drugs inhibiting beta-catenin activation with radiation and chemotherapy in locally advanced pancreatic cancer.
Watson
Richard L
RL
Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI, USA.
Spalding
Aaron C
AC
Zielske
Steven P
SP
Morgan
Meredith
M
Kim
Alex C
AC
Bommer
Guido T
GT
Eldar-Finkelman
Hagit
H
Giordano
Thomas
T
Fearon
Eric R
ER
Hammer
Gary D
GD
Lawrence
Theodore S
TS
Ben-Josef
Edgar
E
D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D005260:Female; D015870:Gene Expression / Q000528:radiation effects*; D020869:Gene Expression Profiling; D020868:Gene Silencing; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000532:radiotherapy; D011836:Radiation Tolerance / Q000235:genetics*; D011878:Radiotherapy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023041:Xenograft Model Antitumor Assays; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D051176:beta Catenin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3
Digestion. 1999 Nov-Dec;60(6):544-8
10545724
Radiat Res. 1984 Jul;99(1):73-84
6739728
Proc Natl Acad Sci U S A. 1996 Sep 17;93(19):10228-33
8816781
Invest New Drugs. 2005 Oct;23(5):485-7
16133800
Cancer Res. 2008 Jul 15;68(14):5859-68
18632640
Biochem J. 1993 Nov 15;296 ( Pt 1):15-9
8250835
J Cell Biol. 1999 Aug 23;146(4):855-68
10459019
Am J Pathol. 2009 Jan;174(1):248-55
19036807
Proc Natl Acad Sci U S A. 2007 Jan 9;104(2):618-23
17202265
Proc Natl Acad Sci U S A. 2002 Jun 11;99(12):8265-70
12060769
Proc Natl Acad Sci U S A. 2009 Feb 17;106(7):2331-6
19179402
Cell Growth Differ. 1999 Jun;10(6):369-76
10392898
Proc Natl Acad Sci U S A. 2000 Nov 7;97(23):12613-8
11050151
Biochem J. 1993 Sep 15;294 ( Pt 3):625-9
8397507
Mol Cell Biol. 1999 Aug;19(8):5696-706
10409758
Mol Vis. 2000 Oct 05;6:178-83
11023552
J Clin Oncol. 2007 May 20;25(15):1960-6
17452677
Oncogene. 2006 Jan 5;25(1):139-46
16247484
Cancer Res. 2006 Dec 1;66(23):11179-86
17145862
Prog Neurobiol. 2006 Jul;79(4):173-89
16935409
Clin Cancer Res. 2007 Nov 15;13(22 Pt 1):6827-33
18006785
Cancer Res. 2006 Feb 15;66(4):2320-7
16489037
J Cell Biochem. 2006 Apr 1;97(5):969-83
16267835
Strahlenther Onkol. 2004 Mar;180(3):157-64
14991204
Cancer Res. 2007 Oct 1;67(19):8980-4
17908997
J Biol Chem. 2002 Jun 14;277(24):21657-65
11940574
BMC Cell Biol. 2001;2:12
11483158
Ann N Y Acad Sci. 1999 Jun 30;880:288-307
10415874
J Virol. 1998 Dec;72(12):9873-80
9811723
Int J Cancer. 2008 Jan 1;122(1):100-7
17764107
Science. 1997 Mar 21;275(5307):1784-7
9065401
Neuropharmacology. 2002 Dec;43(7):1158-64
12504922
J Clin Invest. 2004 Jun;113(11):1535-49
15173880