I-kappa-kinase-2 (IKK-2) inhibition potentiates vincristine cytotoxicity in non-Hodgkin's lymphoma.
BACKGROUND
IKK-2 is an important regulator of the nuclear factor-κB (NF-κB) which has been implicated in survival, proliferation and apoptosis resistance of lymphoma cells. In this study, we investigated whether inhibition of IKK-2 impacts cell growth or cytotoxicity of selected conventional chemotherapeutic agents in non-Hodgkin's lymphoma.Two established model systems were used; Follicular (WSU-FSCCL) and Diffuse Large Cell (WSU-DLCL2) Lymphoma, both of which constitutively express p-IκB. A novel, selective small molecule inhibitor of IKK-2, ML120B (N-[6-chloro-7-methoxy-9H-β-carbolin-8-yl]-2-methylnicotinamide) was used to perturb NF-κB in lymphoma cells. The growth inhibitory effect of ML120B (M) alone and in combination with cyclophosphamide monohydrate (C), doxorubicin (H) or vincristine (V) was evaluated in vitro using short-term culture assay. We also determined efficacy of the combination in vivo using the SCID mouse xenografts.


RESULTS
ML120B down-regulated p-IκBα protein expression in a concentration dependent manner, caused growth inhibition, increased G0/G1 cells, but did not induce apoptosis. There was no significant enhancement of cell kill in the M/C or M/H combination. However, there was strong synergy in the M/V combination where the vincristine concentration can be lowered by a hundred fold in the combination for comparable G2/M arrest and apoptosis. ML120B prevented vincristine-induced nuclear translocation of p65 subunit of NF-κB. In vivo, ML120B was effective by itself and enhanced CHOP anti-tumor activity significantly (P = 0.001) in the WSU-DLCL2-SCID model but did not prevent CNS lymphoma in the WSU-FSCCL-SCID model.


CONCLUSIONS
For the first time, this study demonstrates that perturbation of IKK-2 by ML120B leads to synergistic enhancement of vincristine cytotoxicity in lymphoma. These results suggest that disruption of the NF-κB pathway is a useful adjunct to cytotoxic chemotherapy in lymphoma.
Al-Katib
Ayad
A
Lymphoma Research Laboratory, Wayne State University-School of Medicine, 540 E, Canfield, 8229 Scott Hall, Detroit, MI 48201, USA. aalkati@med.wayne.edu
Arnold
Alan A
AA
Aboukameel
Amro
A
Sosin
Angela
A
Smith
Peter
P
Mohamed
Anwar N
AN
Beck
Frances W
FW
Mohammad
Ramzi M
RM
D000818:Animals; D000996:Antitussive Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D003520:Cyclophosphamide / Q000627:therapeutic use; D004317:Doxorubicin / Q000627:therapeutic use; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy; D008228:Lymphoma, Non-Hodgkin / Q000188:drug therapy*; D051379:Mice; D016513:Mice, SCID; D008856:Microscopy, Fluorescence; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D014750:Vincristine / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
D000996:Antitussive Agents; D004791:Enzyme Inhibitors; D009536:Niacinamide; D014750:Vincristine; D004317:Doxorubicin; D003520:Cyclophosphamide; D051550:I-kappa B Kinase
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