title: Bcl-2 inhibits apoptosis by increasing the time-to-death and intrinsic cell-to-cell variations in the mitochondrial pathway of cell death.
abstract: BH3 mimetics have been proposed as new anticancer therapeutics. They target anti-apoptotic Bcl-2 proteins, up-regulation of which has been implicated in the resistance of many cancer cells, particularly leukemia and lymphoma cells, to apoptosis. Using probabilistic computational modeling of the mitochondrial pathway of apoptosis, verified by single-cell experimental observations, we develop a model of Bcl-2 inhibition of apoptosis. Our results clarify how Bcl-2 imparts its anti-apoptotic role by increasing the time-to-death and cell-to-cell variability. We also show that although the commitment to death is highly impacted by differences in protein levels at the time of stimulation, inherent stochastic fluctuations in apoptotic signaling are sufficient to induce cell-to-cell variability and to allow single cells to escape death. This study suggests that intrinsic cell-to-cell stochastic variability in apoptotic signaling is sufficient to cause fractional killing of cancer cells after exposure to BH3 mimetics. This is an unanticipated facet of cancer chemoresistance.
authors.affiliation: School of Biological Sciences, University of Auckland, Thomas Bld., 3a Symonds Street, Auckland, 1142, New Zealand. J.Skommer@auckland.ac.nz
authors.forename: Joanna
authors.initials: J
authors.lastname: Skommer
authors.forename: Tom
authors.initials: T
authors.lastname: Brittain
authors.forename: Subhadip
authors.initials: S
authors.lastname: Raychaudhuri
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D001578:Benzopyrans / Q000378:metabolism / Q000494:pharmacology; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D005434:Flow Cytometry; D019254:Genes, bcl-2; D006801:Humans; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D001578:Benzopyrans; D009570:Nitriles; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C456800:ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate; D045304:Cytochromes c