Proteasome inhibitors trigger NOXA-mediated apoptosis in melanoma and myeloma cells.
Patients with metastatic melanoma or multiple myeloma have a dismal prognosis because these aggressive malignancies resist conventional treatment. A promising new oncologic approach uses molecularly targeted therapeutics that overcomes apoptotic resistance and, at the same time, achieves tumor selectivity. The unexpected selectivity of proteasome inhibition for inducing apoptosis in cancer cells, but not in normal cells, prompted us to define the mechanism of action for this class of drugs, including Food and Drug Administration-approved bortezomib. In this report, five melanoma cell lines and a myeloma cell line are treated with three different proteasome inhibitors (MG-132, lactacystin, and bortezomib), and the mechanism underlying the apoptotic pathway is defined. Following exposure to proteasome inhibitors, effective killing of human melanoma and myeloma cells, but not of normal proliferating melanocytes, was shown to involve p53-independent induction of the BH3-only protein NOXA. Induction of NOXA at the protein level was preceded by enhanced transcription of NOXA mRNA. Engagement of mitochondrial-based apoptotic pathway involved release of cytochrome c, second mitochondria-derived activator of caspases, and apoptosis-inducing factor, accompanied by a proteolytic cascade with processing of caspases 9, 3, and 8 and poly(ADP)-ribose polymerase. Blocking NOXA induction using an antisense (but not control) oligonucleotide reduced the apoptotic response by 30% to 50%, indicating a NOXA-dependent component in the overall killing of melanoma cells. These results provide a novel mechanism for overcoming the apoptotic resistance of tumor cells, and validate agents triggering NOXA induction as potential selective cancer therapeutics for life-threatening malignancies such as melanoma and multiple myeloma.
Qin
Jian-Zhong
JZ
Department of Pathology, Loyola University Medical Center, Maywood, Illinois 60153-5385, USA.
Ziffra
Jeffrey
J
Stennett
Lawrence
L
Bodner
Barbara
B
Bonish
Brian K
BK
Chaturvedi
Vijaya
V
Bennett
Frank
F
Pollock
Pamela M
PM
Trent
Jeffrey M
JM
Hendrix
Mary J C
MJ
Rizzo
Paola
P
Miele
Lucio
L
Nickoloff
Brian J
BJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D005260:Female; D006801:Humans; D008544:Melanocytes / Q000166:cytology / Q000187:drug effects; D008545:Melanoma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D016376:Oligonucleotides, Antisense / Q000235:genetics; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011719:Pyrazines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D023041:Xenograft Model Antitumor Assays
D001897:Boronic Acids; D016376:Oligonucleotides, Antisense; C498702:PMAIP1 protein, human; C408009:Pmaip1 protein, mouse; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000069286:Bortezomib