title: Upregulation of survivin in G2/M cells and inhibition of caspase 9 activity enhances resistance in staurosporine-induced apoptosis.
abstract: Survivin, a member of the inhibitor of apoptosis (IAP) gene family, plays an important role in both the regulation of cell cycle and the inhibition of apoptosis, and is frequently overexpressed in many tumor types. In neuroblastomas, the expression of survivin correlates with a more aggressive and histologically unfavorable disease. Survivin is predominantly a cytoplasmic protein that is expressed in a cell cycle-dependent manner, increasing in the G2/M phase of the cell cycle followed by a rapid decline in the G1 phase. Recently, the role of survivin in resistance to chemotherapy has become an area of intensive investigation. In this study, we demonstrate a phase-specific resistance due to survivin in staurosporine (STS)-induced apoptosis in the human neuroblastoma cell line SK-N-MC. G2/M-arrested cultures show an upregulation of survivin expression and are more resistant, whereas G1-phase cells that show decreased levels of survivin are more sensitive to apoptosis. Localization studies revealed differences in the distribution of survivin in two synchronized populations, with G1 cells having weakly positive staining confined to the nucleus, in contrast to G2/M cells that depicted a more uniform and intense expression of survivin throughout the cell. In our experimental system, STS induced apoptosis through the mitochondrial-caspase 9-mediated pathway. Retention of survivin in G1 cells by inhibition of the ubiquitin-proteosome pathway or inhibition of caspase 9 protected the cells against apoptosis. Our data suggest that survivin exerts its antiapoptotic effect by inhibiting caspase 9 activity, an important event in STS-mediated apoptosis. In context with cell cycle-dependent responses to chemotherapy, the data from this study suggest the possibility of exploiting the survivin pathway for inducing apoptosis in tumor cells.
authors.affiliation: National Centre for Cell Science, NCCS Complex, Ganeshkhind, Pune 411 007, India.
authors.forename: Anmol
authors.initials: A
authors.lastname: Chandele
authors.forename: Vandna
authors.initials: V
authors.lastname: Prasad
authors.forename: Jayashree C
authors.initials: JC
authors.lastname: Jagtap
authors.forename: Ravi
authors.initials: R
authors.lastname: Shukla
authors.forename: Padma R
authors.initials: PR
authors.lastname: Shastry
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051034:Inhibitor of Apoptosis Proteins; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009363:Neoplasm Proteins; D009447:Neuroblastoma / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019311:Staurosporine / Q000494:pharmacology; D000077022:Survivin; D014162:Transfection; D015854:Up-Regulation
chemical_list: C107489:BIRC5 protein, human; D004791:Enzyme Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D000077022:Survivin; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases; D019311:Staurosporine