{'fraction_non_alphanumeric': 0.027672273467173086, 'fraction_numerical': 0.020075963103635377, 'mean_word_length': 5.633093525179856, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Activation of p53-Dependent Apoptosis by Acute Ablation of Glycogen Synthase Kinase-3β in Colorectal Cancer Cells

Purpose: 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-3β (GSK3β), a multifunctional kinase whose role in tumor cell survival is not defined. Experimental Design: We used molecular, genetic, and pharmacologic antagonists of GSK3β 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 GSK3β resulted in sustained elevation of p53, with up-regulation of p21Waf1/Cip1 and loss of survivin levels. Molecular targeting of GSK3β by overexpression of a GSK3β dominant-negative mutant, or acutesilencing of GSK3β 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, GSK3β 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 GSK3β 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.