title: 5-Fluorouracil signaling through a calcium-calmodulin-dependent pathway is required for p53 activation and apoptosis in colon carcinoma cells.
abstract: 5-Fluorouracil (5-FU) is an anti-metabolite that is in clinical use for treatment of several cancers. In cells, it is converted into three distinct fluoro-based nucleotide analogs, which interfere with DNA synthesis and repair, leading to genome impairment and, eventually, apoptotic cell death. Current knowledge states that in certain cell types, 5-FU-induced stress is signaling through a p53-dependent induction of tumor necrosis factor-receptor oligomerization required for death-inducing signaling complex formation and caspase-8 activation. Here we establish a role of calcium (Ca(2+)) as a messenger for p53 activation in response to 5-FU. Using a combination of pharmacological and genetic approaches, we show that treatment of colon carcinoma cells stimulates entry of extracellular Ca(2+) through long lasting-type plasma membrane channels, which further directs posttranslational phosphorylation of at least three p53 serine residues (S15, S33 and S37) by means of calmodulin (CaM) activity. Obstructing this pathway by the Ca(2+)-chelator BAPTA (1,2-bis(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid) or by inhibitors of CaM efficiently reduces 5-FU-induced caspase activities and subsequent cell death. Moreover, ectopic expression of p53 S15A in HCT116 p53(-/-) cells confirmed the importance of a Ca(2+)-CaM-p53 axis in 5-FU-induced extrinsic apoptosis. The fact that a widely used therapeutic drug, such as 5-FU, is operating via this pathway could provide new therapeutic intervention points, or specify new combinatorial treatment regimes.
authors.affiliation: Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Can
authors.forename: B
authors.initials: B
authors.lastname: Akpinar
authors.forename: Y
authors.initials: Y
authors.lastname: Baran
authors.forename: B
authors.initials: B
authors.lastname: Zhivotovsky
authors.forename: M
authors.initials: M
authors.lastname: Olsson
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002147:Calmodulin / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005472:Fluorouracil / Q000494:pharmacology*; D045325:HCT116 Cells; D006801:Humans; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D021381:Protein Transport; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002147:Calmodulin; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D002118:Calcium; D005472:Fluorouracil