title: The calcium-binding protein S100B down-regulates p53 and apoptosis in malignant melanoma.
abstract: The S100B-p53 protein complex was discovered in C8146A malignant melanoma, but the consequences of this interaction required further study. When S100B expression was inhibited in C8146As by siRNA (siRNA(S100B)), wt p53 mRNA levels were unchanged, but p53 protein, phosphorylated p53, and p53 gene products (i.e. p21 and PIDD) were increased. siRNA(S100B) transfections also restored p53-dependent apoptosis in C8146As as judged by poly(ADP-ribose) polymerase cleavage, DNA ladder formation, caspase 3 and 8 activation, and aggregation of the Fas death receptor (+UV); whereas, siRNA(S100B) had no effect in SK-MEL-28 cells containing elevated S100B and inactive p53 (p53R145L mutant). siRNA(S100B)-mediated apoptosis was independent of the mitochondria, because no changes were observed in mitochondrial membrane potential, cytochrome c release, caspase 9 activation, or ratios of pro- and anti-apoptotic proteins (BAX, Bcl-2, and Bcl-X(L)). As expected, cells lacking S100B (LOX-IM VI) were not affected by siRNA(S100B), and introduction of S100B reduced their UV-induced apoptosis activity by 7-fold, further demonstrating that S100B inhibits apoptosis activities in p53-containing cells. In other wild-type p53 cells (i.e. C8146A, UACC-2571, and UACC-62), S100B was found to contribute to cell survival after UV treatment, and for C8146As, the decrease in survival after siRNA(S100B) transfection (+UV) could be reversed by the p53 inhibitor, pifithrin-alpha. In summary, reducing S100B expression with siRNA was sufficient to activate p53, its transcriptional activation activities, and p53-dependent apoptosis pathway(s) in melanoma involving the Fas death receptor and perhaps PIDD. Thus, a well known marker for malignant melanoma, S100B, likely contributes to cancer progression by down-regulating the tumor suppressor protein, p53.
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Maryland 21201.
authors.forename: Jing
authors.initials: J
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Maryland 21201.
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Maryland 21201; Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Wilder
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Maryland 21201; Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201. Electronic address: fcarr001@umaryland.edu.
authors.forename: France
authors.initials: F
authors.lastname: Carrier
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Maryland 21201; Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201. Electronic address: dweber@umaryland.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Weber
mesh_terms: D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins; D015536:Down-Regulation; D004789:Enzyme Activation / Q000235:genetics / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000235:genetics / Q000528:radiation effects; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics / Q000528:radiation effects; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; D051034:Inhibitor of Apoptosis Proteins; D046912:Multiprotein Complexes; D009414:Nerve Growth Factors; C485896:PIDD1 protein, human; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9