title: Bruton's tyrosine kinase prevents activation of the anti-apoptotic transcription factor STAT3 and promotes apoptosis in neoplastic B-cells and B-cell precursors exposed to oxidative stress.
abstract: Bruton's tyrosine kinase (BTK) was previously demonstrated to be a mediator of oxidative stress-induced apoptosis in irradiated neoplastic B-cells and B-cell precursors. Defective BTK expression in leukaemic B-cell precursors from infants with t(4;11) acute lymphoblastic leukaemia has been associated with radiation resistance. The present study examined whether BTK mediates apoptosis during oxidative stress by interfering with the anti-apoptotic function of signal transducer and activator of transcription 3 (STAT3). BTK physically associated with and tyrosine phosphorylated STAT3; this association was promoted by pervanadate (PV)-induced oxidative stress. The BTK/STAT3 interaction appeared to prevent STAT3 response to oxidative stress, because PV-induced STAT3 activation was markedly enhanced in DT40 chicken lymphoma B-cells that were rendered BTK-deficient by targeted disruption of the btk gene as well as in BTK-deficient RAMOS-1 human lymphoma B-cells. These BTK-deficient cells were highly resistant to oxidative stress-induced apoptosis triggered by PV treatment. Reconstitution of BTK-deficient DT40 cells with wild-type human BTK gene eliminated the amplification of the STAT3 response and restored the PV-induced apoptotic signal. Similarly, while the BTK-positive NALM-6 human leukaemic B-cell precursor cell line showed no STAT3 activation after PV treatment and was exquisitely sensitive to PV-induced apoptosis, PV failed to induce apoptosis in BTK-deficient RAMOS-1 human lymphoma B-cells that showed a robust STAT3 response. These results provide unprecedented biochemical and genetic evidence for a unique mode of cross-talk that occurs between BTK and STAT3 pathways during oxidative stress, whereby BTK may trigger apoptosis via negative regulation of the anti-apoptotic STAT3 activity.
authors: Parker Hughes Cancer Center, Roseville, MN 55113, USA. fatih_uckun@tmo.blackberry.net
authors: Fatih
authors: F
authors: Uckun
authors: Zahide
authors: Z
authors: Ozer
authors: Alexei
authors: A
authors: Vassilev
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002645:Chickens; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D015448:Leukemia, B-Cell / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D016393:Lymphoma, B-Cell / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014638:Vanadates / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D009363:Neoplasm Proteins; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C076715:pervanadate; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; D017027:Protein Tyrosine Phosphatases