Combined proteasome and Bcl-2 inhibition stimulates apoptosis and inhibits growth in EBV-transformed lymphocytes: a potential therapeutic approach to EBV-associated lymphoproliferative diseases.
OBJECTIVE
Epstein-Barr virus (EBV) transforms B-cells into immortalized lymphoblastoid cells (LCLs) by triggering signaling pathways that lead to activation of multiple transcription factors and anti-apoptotic proteins, including NF-kappaB and Bcl-2, respectively. Since proteasome inhibition suppresses NF-kappaB activity, we sought to determine whether the proteasome inhibitor, bortezomib, alone or in combination with Bcl-2 inhibition, has potential as a therapeutic strategy in EBV-driven B-cell neoplasms.


METHODS
We evaluated the effects of bortezomib in LCLs in vitro, in the presence and absence of the small molecular inhibitor of Bcl-2, HA14-1, on proliferation, apoptosis, caspase activation, and expression of Bcl-2 family members, and in vivo in the severe combined immunodeficiency (SCID) model of EBV+ lymphoproliferative disease.


RESULTS
Bortezomib inhibited proliferation, stimulated apoptosis, and activated caspases-3 and -9 in a dose-dependent manner in LCLs. In vivo, bortezomib completely abrogated development of EBV+ lymphoproliferative disease in LCL-bearing SCID mice. When HA14-1 was added to bortezomib in vitro, we observed a synergistic anti-proliferative effect and enhancement of apoptosis and caspase activation, including activation of caspase-8, in LCLs. These events were associated with modulation of expression of Bcl-2 family members towards a pro-apoptotic profile with translocation of cytochrome C from mitochondria to cytoplasm.


CONCLUSIONS
These studies demonstrated that bortezomib mediates anti-tumor effects in EBV-associated lymphoproliferations both in vitro and in vivo, and that its anti-proliferative and apoptotic effects are synergistically enhanced in the presence of a Bcl-2 inhibitor. These findings support further investigation of bortezomib in EBV+ lymphoproliferative diseases, and suggest that bortezomib in combination with Bcl-2 antagonists represents a potential therapeutic strategy for EBV-driven B-cell neoplasms.
Srimatkandada
Pavani
P
Department of Medicine, Yale University School of Medicine, New Haven, CT, USA.
Loomis
Regina
R
Carbone
Rocco
R
Srimatkandada
Srinivasan
S
Lacy
Jill
J
D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000494:pharmacology; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D020169:Caspases / Q000378:metabolism; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D008214:Lymphocytes / Q000166:cytology* / Q000187:drug effects*; D008232:Lymphoproliferative Disorders / Q000188:drug therapy / Q000473:pathology*; D009570:Nitriles / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000145:classification / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology
D001578:Benzopyrans; D001897:Boronic Acids; D009570:Nitriles; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D011719:Pyrazines; C456800:ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate; D000069286:Bortezomib; D020169:Caspases; D046988:Proteasome Endopeptidase Complex