Activation of p53-dependent apoptosis by acute ablation of glycogen synthase kinase-3beta in colorectal cancer cells
UMass Chan AffiliationsDepartment of Cancer Biology and Cancer Center
CDC2 Protein Kinase
Cell Cycle Proteins
Cyclin-Dependent Kinase Inhibitor p21
Glycogen Synthase Kinase 3
Proto-Oncogene Proteins c-mdm2
TCF Transcription Factors
Tumor Suppressor Protein p14ARF
Tumor Suppressor Protein p53
Medicine and Health Sciences
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AbstractPURPOSE: The restoration of checkpoint mechanisms may provide a rational anticancer approach, but the molecular circuitries of how this can be achieved therapeutically are poorly understood. A pivotal signaling network in colorectal cancer cells involves glycogen synthase kinase-3beta (GSK3beta), a multifunctional kinase whose role in tumor cell survival is not defined. EXPERIMENTAL DESIGN: We used molecular, genetic, and pharmacologic antagonists of GSK3beta in p53+/+ or p53-/- colorectal cancer cells. We monitored kinase activity in immunoprecipitation, protein expression by immunoblotting, and cell death by multiparametric flow cytometry. A xenograft colorectal cancer model was used to study antitumor activity in vivo. RESULTS: Treatment of p53+/+ colorectal cancer cells with pharmacologic inhibitors of GSK3beta resulted in sustained elevation of p53, with up-regulation of p21(Waf1/Cip1) and loss of survivin levels. Molecular targeting of GSK3beta by overexpression of a GSK3beta dominant-negative mutant, or acute-silencing of GSK3beta by RNA interference, reproduced the induction of transcriptionally active p53 in colorectal cancer cells. This pathway was recapitulated by deregulated Wnt/T-cell factor signaling, with elevation of the tumor suppressor p14ARF, and reduced expression of the p53 antagonist, MDM2. Rather than cell cycle arrest, GSK3beta blockade resulted in p53-dependent apoptosis, which was contributed by acute loss of survivin and inhibition of colorectal cancer growth in mice. CONCLUSIONS: Acute ablation of GSK3beta in colorectal cancer cells activates p53-dependent apoptosis and antagonizes tumor growth. This pathway may be exploited for rational treatment of colorectal cancer patients retaining wild-type p53.
SourceClin Cancer Res. 2005 Jun 15;11(12):4580-8. Link to article on publisher's site
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/41798
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