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Clin Cancer Res. 2014 Mar 15;20(6):1576-89. doi: 10.1158/1078-0432.CCR-13-0987.

The Nedd8-activating enzyme inhibitor MLN4924 thwarts microenvironment-driven NF-κB activation and induces apoptosis in chronic lymphocytic leukemia B cells.

Author information

1
Authors' Affiliations: Departments of Medicine and Pathology, Dartmouth-Hitchcock Medical Center, Lebanon; Department of Pharmacology and Toxicology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire; and Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts.

Abstract

BACKGROUND:

Stromal-mediated signaling enhances NF-κB pathway activity in chronic lymphocytic leukemia (CLL) B cells, leading to cell survival and chemoresistance. Ubiquitination of IκBα may partially account for constitutive activation of NF-κB. MLN4924 is an investigational agent that inhibits the Nedd8-activating enzyme, thereby neutralizing Cullin-RING ubiquitin ligases and preventing degradation of their substrates.

EXPERIMENTAL DESIGN:

We conducted a preclinical assessment of MLN4924 in CLL. Primary CLL cells were cocultured in vitro with CD40L-expressing stroma to mimic the prosurvival conditions present in lymphoid tissue. The effect of MLN4924 on CLL cell apoptosis, NF-κB pathway activity, Bcl-2 family members, and cell cycle was assessed by flow cytometry, Western blotting, PCR, and immunocytochemistry.

RESULTS:

CD40L-expressing stroma protected CLL cells from spontaneous apoptosis and induced resistance to multiple drugs, accompanied by NF-κB activation and Bim repression. Treatment with MLN4924 induced CLL cell apoptosis and circumvented stroma-mediated resistance. This was accompanied by accumulation of phospho-IκBα, decreased nuclear translocation of p65 and p52 leading to inhibition of both the canonical and noncanonical NF-κB pathways, and reduced transcription of their target genes, notably chemokines. MLN4924 promoted induction of Bim and Noxa in the CLL cells leading to rebalancing of Bcl-2 family members toward the proapoptotic BH3-only proteins. siRNA-mediated knockdown of Bim or Noxa decreased sensitivity to MLN4924. MLN4924 enhanced the antitumor activity of the inhibitors of B-cell receptor (BCR)-associated kinases.

CONCLUSIONS:

MLN4924 disrupts NF-κB activation and induces Bim expression in CLL cells, thereby preventing stroma-mediated resistance. Our data provide rationale for further evaluation of MLN4924 in CLL.

PMID:
24634471
PMCID:
PMC3960291
DOI:
10.1158/1078-0432.CCR-13-0987
[Indexed for MEDLINE]
Free PMC Article

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