title: Enhancement of stress-induced apoptosis in B-lineage cells by caspase-9 inhibitor.
abstract: We have established human B-lineage (BLIN) acute lymphoblastic leukemia cell lines that retain a dependency on fibroblast monolayers for survival and proliferation. Eight hours following removal from adherent cell contact BLIN cells undergo a decrease in mitochondrial transmembrane potential and an increase in annexin V binding. Unexpectedly, the caspase-9 inhibitor (C9i) benzyloxycarbonyl-Leu-Glu-His-Asp-fluoromethylketone enhanced the appearance of apoptotic cells within 8 hours following removal of BLIN cells from fibroblast monolayers. C9i enhancement of apoptosis was dose dependent and did not occur with irreversible inhibitors of caspases-2, -3, -6, and -8. C9i also enhanced apoptosis in cord blood-derived CD19(+) B-lineage cells (but not myeloid cells) removed from murine stromal cells. Longer exposure (> 18 hours) to C9i culminated in apoptosis in a panel of B-lineage acute lymphoblastic leukemia (ALL) cell lines in the presence or absence of fibroblast monolayers, as well as in 2 proliferating leukemic cell lines (RAMOS and CEM). BLIN-4L cells made deficient in caspase-9 by RNA interference exhibited no resistance to apoptotic signals and actually showed increased apoptotic sensitivity to staurosporine. These collective results suggest that a 4-amino acid caspase inhibitor of caspase-9 can promote apoptosis and that at least some types of apoptotic pathways in B-lineage ALL do not require caspase-9.
authors.affiliation: Cancer Center and Department of Laboratory Medicine/Pathology, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Nisha
authors.initials: N
authors.lastname: Shah
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Asch
authors.forename: Alana S
authors.initials: AS
authors.lastname: Lysholm
authors.forename: Tucker W
authors.initials: TW
authors.lastname: Lebien
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects / Q000473:pathology*; D002051:Burkitt Lymphoma / Q000473:pathology; D053453:Caspase 9; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D013312:Stress, Physiological / Q000473:pathology*
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse; D053453:Caspase 9