The NF-kappaB subunit Rel A is associated with in vitro survival and clinical disease progression in chronic lymphocytic leukemia and represents a promising therapeutic target.
ABSTRACT In this study, we characterized nuclear factor kappaB (NF-kappaB) subunit DNA binding in chronic lymphocytic leukemia (CLL) samples and demonstrated heterogeneity in basal and inducible NF-kappaB. However, all cases showed higher basal NF-kappaB than normal B cells. Subunit analysis revealed DNA binding of p50, Rel A, and c-Rel in primary CLL cells, and Rel A DNA binding was associated with in vitro survival (P = .01) with high white cell count (P = .01) and shorter lymphocyte doubling time (P = .01). NF-kappaB induction after in vitro stimulation with anti-IgM was associated with increased in vitro survival (P < .001) and expression of the signaling molecule ZAP-70 (P = .003). Prompted by these data, we evaluated the novel parthenolide analog, LC-1, in 54 CLL patient samples. LC-1 induced apoptosis in all the samples tested with a mean LD(50) of 2.8 microM after 24 hours; normal B and T cells were significantly more resistant to its apoptotic effects (P < .001). Apoptosis was preceded by a marked loss of NF-kappaB DNA binding and sensitivity to LC-1 correlated with basal Rel A DNA binding (P = .03, r(2) = 0.15). Furthermore, Rel A DNA binding was inversely correlated with sensitivity to fludarabine (P = .001, r(2) = 0.3), implicating Rel A in fludarabine resistance. Taken together, these data indicate that Rel A represents an excellent therapeutic target for this incurable disease.
Full-textDOI: · Available from: Peter A Crooks, Aug 11, 2014
- SourceAvailable from: Jean-Brice MarteauChronic Lymphocytic Leukemia, 02/2012; , ISBN: 978-953-307-881-6
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ABSTRACT: In this Ph. D. Thesis it was possible to get new insight about the variety of genomic lesions in B-NHLs and gain new knowledge about the mechanisms of deregulated NF-kB signaling in B-NHLs and cHL. The absence of inactivating mutations in TNFAIP3, indicates that, in contrast to other lymphomas, this gene was not involved in the constitutive activation of the NF-kB pathway in CLL. The supposition that TNFAIP3 is the target of the rare 6q deletion in some CLL-cases was therefore disproved. TRAF3 was inactivated by a deletion only once in a cHL cell line, but it was not affected by inactivating mutations or deletions in all other analyzed cell lines and in seven primary cHL-cases. This demonstrates that TRAF3 inactivation does not account normally for the constitutive NF-kB-expression in HRS-cells, but seems to be an uncommon event. In this work, two MYC-LDI-PCR approaches were established and used to amplify in one out of 13 B-NHL-cases a translocation with SOCS1 as a to date unknown translocation partner of MYC-translocations. Because SOCS1 is a known tumor suppressor, a translocation juxtaposing SOCS1 to the MYC-oncogene is of great interest. The mechanism affecting both translocated genes remains to be identified. The partly new established igH-LDI-PCR approaches in this work were successfully used to amplify and sequence the translocation partner of seven out of 28 DLBCLs with IgH-associated translocations. In four of these cases the translocation partners were so far not described in translocations involving the IgH-locus in DLBCLs. In the majority of the cases the translocation disrupted the coding sequence of the partner gene. It remains to clarify, if the translocations inactivate an unknown tumor suppressor or deregulate a distant unknown oncogene. In one of the cases IRF4 was identified as target oncogene of the translocation; this finding led to the characterization of a novel subtype of GCB-DLBCL. The results presented here show that DLBCL is more heterogeneous as previously expected and the identification of PVRL2 as translocation partner shows another example of translocations affecting the same breakpoint in B- and T-cell lymphomas.
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ABSTRACT: The sensitivity of chronic lymphocytic leukemia (CLL) cells to current treatments, both in vitro and in vivo, relies on their ability to activate apoptotic death. CLL cells resistant to DNA damage-induced apoptosis display deregulation of a specific set of genes. Microarray hybridization (Human GeneChip, Affymetrix), immunofluorescent in situ labeling coupled with video-microscopy recording/analyses, chromatin-immunoprecipitation (ChIP), polymerase chain reactions (PCR), real-time quantitative PCR (RT-QPCR) and bisulfite genome sequencing were the main methods applied. Statistical analyses were performed by applying GCRMA and SAM analysis (microarray data) and Student's t-test or Mann & Whitney's U-test. Herein we show that, remarkably, in a resistant male CLL cells the vast majority of genes were down-regulated compared with sensitive cells, whereas this was not the case in cells derived from females. This gene down-regulation was found to be associated with an overall gain of heterochromatin as evidenced by immunofluorescent labeling of heterochromatin protein 1α (HP-1), trimethylated histone 3 lysine 9 (3metH3K9), and 5-methylcytidine (5metC). Notably, 17 genes were found to be commonly deregulated in resistant male and female cell samples. Among these, RELB was identified as a discriminatory candidate gene repressed in the male and upregulated in the female resistant cells. The molecular defects in the silencing of RELB involve an increase in H3K9- but not CpG-island methylation in the promoter regions. Increase in acetyl-H3 in resistant female but not male CLL samples as well as a decrease of total cellular level of RelB after an inhibition of histone deacetylase (HDAC) by trichostatin A (TSA), further emphasize the role of epigenetic modifications which could discriminate two CLL subsets. Together, these results highlighted the epigenetic RELB silencing as a new marker of the progressive disease in males.BMC Medical Genomics 11/2010; 3:53. DOI:10.1186/1755-8794-3-53 · 3.91 Impact Factor