Bortezomib induces canonical nuclear factor-kappaB activation in multiple myeloma cells.
Bortezomib is a proteasome inhibitor with remarkable preclinical and clinical antitumor activity in multiple myeloma (MM) patients. The initial rationale for its use in MM was inhibition of nuclear factor (NF)-kappaB activity by blocking proteasomal degradation of inhibitor of kappaBalpha (IkappaBalpha). Bortezomib inhibits inducible NF-kappaB activity; however, its impact on constitutive NF-kappaB activity in MM cells has not yet been defined. In this study, we demonstrate that bortezomib significantly down-regulated IkappaBalpha expression and triggered NF-kappaB activation in MM cell lines and primary tumor cells from MM patients. Importantly, no inhibition of p65 (RelA) nuclear translocation was recognized after bortezomib treatment in a murine xenograft model bearing human MM cells. Bortezomib-induced NF-kappaB activation was mediated via the canonical pathway. Moreover, other classes of proteasome inhibitors also induced IkappaBalpha down-regulation associated with NF-kappaB activation. Molecular mechanisms whereby bortezomib induced IkappaBalpha down-regulation were further examined. Bortezomib triggered phosphorylation of IkappaB kinase (IKKbeta) and its upstream receptor-interacting protein 2, whereas IKKbeta inhibitor MLN120B blocked bortezomib-induced IkappaBalpha down-regulation and NF-kappaB activation, indicating receptor-interacting protein 2/IKKbeta signaling plays crucial role in bortezomib-induced NF-kappaB activation. Moreover, IKKbeta inhibitors enhanced bortezomib-induced cytotoxicity. Our studies therefore suggest that bortezomib-induced cytotoxicity cannot be fully attributed to inhibition of canonical NF-kappaB activity in MM cells.
Jerome Lipper Multiple Myeloma Center, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Teru
T
Hideshima
Hiroshi
H
Ikeda
Dharminder
D
Chauhan
Yutaka
Y
Okawa
Noopur
N
Raje
Klaus
K
Podar
Constantine
C
Mitsiades
Nikhil C
NC
Munshi
Paul G
PG
Richardson
Ruben D
RD
Carrasco
Kenneth C
KC
Anderson
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001897:Boronic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D000069286:Bortezomib; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D020672:I-kappa B Proteins / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000187:drug effects* / Q000502:physiology; D009363:Neoplasm Proteins / Q000187:drug effects* / Q000502:physiology; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011719:Pyrazines / Q000494:pharmacology* / Q000627:therapeutic use; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2 / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D001897:Boronic Acids; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D009363:Neoplasm Proteins; C000606205:Nfkbia protein, mouse; D011480:Protease Inhibitors; D011719:Pyrazines; D000072000:NF-KappaB Inhibitor alpha; D000069286:Bortezomib; C506253:RIPK2 protein, human; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D051550:I-kappa B Kinase