title: BTK inhibitor ibrutinib is cytotoxic to myeloma and potently enhances bortezomib and lenalidomide activities through NF-κB.
abstract: Ibrutinib (previously known as PCI-32765) has recently shown encouraging clinical activity in chronic lymphocytic leukaemia (CLL) effecting cell death through inhibition of Bruton's tyrosine kinase (BTK). In this study we report for the first time that ibrutinib is cytotoxic to malignant plasma cells from patients with multiple myeloma (MM) and furthermore that treatment with ibrutinib significantly augments the cytotoxic activity of bortezomib and lenalidomide chemotherapies. We describe that the cytotoxicity of ibrutinib in MM is mediated via an inhibitory effect on the nuclear factor-κB (NF-κB) pathway. Specifically, ibrutinib blocks the phosphorylation of serine-536 of the p65 subunit of NF-κB, preventing its nuclear translocation, resulting in down-regulation of anti-apoptotic proteins Bcl-xL, FLIP(L) and survivin and culminating in caspase-mediated apoptosis within the malignant plasma cells. Taken together these data provide a platform for clinical trials of ibrutinib in myeloma and a rationale for its use in combination therapy, particularly with bortezomib.
authors.affiliation: School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Rushworth
authors.forename: Kristian M
authors.initials: KM
authors.lastname: Bowles
authors.forename: Lawrence N
authors.initials: LN
authors.lastname: Barrera
authors.forename: Megan Y
authors.initials: MY
authors.lastname: Murray
authors.forename: Lyubov
authors.initials: L
authors.lastname: Zaitseva
authors.forename: David J
authors.initials: DJ
authors.lastname: MacEwan
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000577:Amides / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects*; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D000077269:Lenalidomide; D009101:Multiple Myeloma / Q000378:metabolism / Q000473:pathology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D010880:Piperidines; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013792:Thalidomide / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000577:Amides; D000970:Antineoplastic Agents; D001897:Boronic Acids; D020672:I-kappa B Proteins; C118451:LFM A13; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D009570:Nitriles; D010880:Piperidines; D011719:Pyrazines; D011720:Pyrazoles; D011743:Pyrimidines; D012333:RNA, Messenger; D000072000:NF-KappaB Inhibitor alpha; C551803:ibrutinib; D013792:Thalidomide; D000069286:Bortezomib; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; D020169:Caspases; D000077269:Lenalidomide; D000225:Adenine