title: LY294002-mediated inhibition of phosphatidylinositol 3-kinase activity triggers growth inhibition and apoptosis in CD40-triggered Ramos-Burkitt lymphoma B cells.
abstract: Cells of the Epstein-Barr virus genome-negative Ramos-Burkitt lymphoma (Ramos-BL) B cell line can be rescued from antigen receptor (AgR)-triggered growth inhibition and apoptosis by signals transduced through their surface CD40. This study investigates whether phosphatidylinositol 3-kinase (PI3-kinase), which has been reported to be intimately involved in the regulation of normal and neoplastic cell growth, plays a role in CD40-promoted Ramos-BL B cell survival and uses the selective and reversible PI3-kinase inhibitor, LY294002 (LY). LY-mediated inhibition of PI3-kinase activity triggers growth inhibition and leads to the processing of caspase-3, caspase-3-like activity, cleavage of the death substrate poly(ADP-ribose) polymerase (PARP), and apoptosis from the G1 phase of cell cycle. These data indicate that constitutive PI3-kinase activity is critical for Ramos-BL B cell progression through the cell cycle such that if this PI3-kinase-dependent pathway(s) is inhibited, the cells default to apoptosis. Signals transduced through CD40 abrogate LY-triggered caspase-3-like activity and PARP cleavage but fail to inhibit LY-triggered growth inhibition, processing of caspase-3, and apoptosis. Likewise, in the presence of LY, signals transduced through CD40 abrogate AgR-triggered caspase-3-like activity and PARP cleavage but fail to inhibit AgR-triggered growth inhibition, caspase-3 processing, and apoptosis. The LY-mediated induction of growth inhibition and apoptosis occurs in the presence of the CD40-induced anti-apoptotic protein Bcl-XL. Taken together these data indicate that the CD40 of Ramos BL B cells is linked to PI3-kinase-independent and -dependent routes of survival: CD40-mediated inhibition of AgR-triggered caspase-3-like activity, PARP cleavage, and CD40-triggered Bcl-XL expression are PI3-kinase-independent, whereas PI3-kinase is critical for CD40-mediated rescue of this cellular population from AgR-triggered growth inhibition, caspase-3 processing, and apoptosis.
authors.affiliation: Department of Biochemistry, University of Oxford, United Kingdom.
authors.forename: A P
authors.initials: AP
authors.lastname: Curnock
authors.forename: K A
authors.initials: KA
authors.lastname: Knox
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000502:physiology; D002051:Burkitt Lymphoma / Q000473:pathology*; D019013:CD40 Antigens / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases; D002478:Cells, Cultured; D002675:Child, Preschool; D002867:Chromones / Q000494:pharmacology*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D051020:bcl-X Protein
chemical_list: C494811:BCL2L1 protein, human; D019013:CD40 Antigens; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases