p65 activity and ZAP-70 status predict the sensitivity of chronic lymphocytic leukemia cells to the selective IkappaB kinase inhibitor BMS-345541.
OBJECTIVE
Constitutive nuclear factor-kappaB (NF-kappaB) activation has been implicated in the pathogenesis of chronic lymphocytic leukemia (CLL). Our purpose was to characterize the molecular mechanisms underlying for the selective IkappaB kinase inhibitor BMS-345541 in CLL cells together with the analysis of its combination with several antineoplasic drugs.


METHODS
Primary cells from 34 CLL patients were incubated with different doses of BMS-345541. NF-kappaB DNA-binding activity was analyzed by ELISA-based kits and the characterization of the apoptotic pathway was done by flow cytometry, immunoblotting, quantitative reverse transcription-PCR, and immunofluorescence techniques.


RESULTS
BMS-345541 selectively induced apoptosis in CLL cells in the low micromolar range irrespective of p53 status. Noteworthy, the high ZAP-70 group was significantly more sensitive to BMS-345541 than the low ZAP-70 group, in correlation with high levels of p65 phosphorylation and DNA-binding activity. Following NF-kappaB inhibition, BMS-345541 led to induction of the mitochondrial apoptotic pathway and activation of both caspase-dependent and caspase-independent factors. Moreover, BMS-345541-induced apoptosis was accompanied by down-regulation of several antiapoptotic NF-kappaB-target genes, including both BCL2 family members and apoptotic endogenous inhibitors. In addition, we showed a strong synergism between BMS-345541 and conventional chemotherapeutics such as mitoxantrone and dexamethasone as well as with new promising drugs such as the BH3-mimetic GX15-070/Obatoclax or the anti-TRAIL-R1 monoclonal antibody mapatumumab.


CONCLUSIONS
These data confirm that NF-kappaB is a relevant target in CLL and indicate that inhibitors of IkappaB kinase, alone or in combination, represent a novel therapeutic strategy for the treatment of CLL patients, especially for the group with high ZAP-70.
Authors' Affiliations: Hematopathology Unit, Department of Pathology and Department of Hematology, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, University of Barcelona, Barcelona, Spain.
Mónica
M
López-Guerra
Gaël
G
Roué
Patricia
P
Pérez-Galán
Roberto
R
Alonso
Neus
N
Villamor
Emili
E
Montserrat
Elias
E
Campo
Dolors
D
Colomer
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005260:Female; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000494:pharmacology*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology*; D051996:Transcription Factor RelA / Q000378:metabolism*; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism*
C471109:4(2'-aminoethyl)amino-1,8-dimethylimidazo(1,2-a)quinoxaline; D007093:Imidazoles; D016328:NF-kappa B; D011810:Quinoxalines; D051996:Transcription Factor RelA; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D051550:I-kappa B Kinase