NFκB expression is a feature of both activated B-cell-like and germinal center B-cell-like subtypes of diffuse large B-cell lymphoma

Abstract

The activation of nuclear factor kappa B (NFjB) transcription factor family is considered to have a key role in diffuse large B-cell lymphoma (DLBCL) pathogenesis and is associated with a specific molecular subtype, the activated B-cell-like (ABC) subtype. We evaluated the expression of NFjB by immunohistochemistry in a large series of DLBCL cases. The five different NFjB family members (NFjB1, NFjB2, RELA, RELB, and REL) showed a heterogeneous expression pattern with the vast majority of cases being positive for at least one factor. Two independent series of tumor samples were classified into germinal center B-cell-like (GCB) or ABC subtypes using different approaches, immunohistochemistry, or gene expression profiling, and the expression of NFjB family members was assessed. Notably, no significant differences regarding the expression of the different NFjB members were detected between the two subtypes, suggesting that NFjB signaling is a prominent feature not only in the ABC subtype, but also in the GCB tumors. Of the five transcription factors, only REL expression had a significant clinical impact on R-CHOP-treated diffuse large B-cell lymphoma, identifying a subgroup of patients with superior clinical outcome. Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma in adults and is clinically and molecularly a heterogeneous disease. 1,2 Based on gene expression profiling, two different molecular subtypes of DLBCL were recognized according to the putative cell of origin; the more aggressive activated B-cell-like (ABC) subtype and the germinal center B-cell-like (GCB) subtype. [3][4][5] These subtypes reflect distinct differentiation stages of normal B-cell development and differ in their clinical presentation, cure rates, and molecular features. 2 Due to practical reasons, algorithms to classify these subtypes using immunohistochemistry of a few markers instead of gene expression profiling have been developed and extensively used. 6,7 These subtypes differ in their oncogenic programs and several subtype-specific genetic alterations have been described. 2,8,9 A hallmark of the ABC subtype is constitutive nuclear factor kappa B (NFkB) activation, and a disruption of this activation induces apoptosis in ABC cell lines. 10 Several recurrent genetic aberrations affecting NFkB signaling have been described in the ABC tumors, including for instance mutations in caspase recruitment

Evaluation of NF-κB subunit expression and signaling pathway activation demonstrates that p52 expression confers better outcome in germinal center B-cell-like diffuse large B-cell lymphoma in association with CD30 and BCL2 functions

“…These data are similar to that reported by Odqvist and Co-workers 16 who used similar cutoffs, except that the expression frequency of class II molecules showed significant differences. The variations might have resulted from a difference in the fixation procedure because we used identical antibodies (p50, rabbit polyclonal antibody (GeneTex, Irvine, CA, USA); p52, mouse monoclonal antibody (Millipore, Billerica, MA, USA); p65, mouse monoclonal antibody (Santa Cruz biotechnology, Santa Cruz, CA, USA); RELB, rabbit polyclonal antibody (Santa Cruz Biotechnology, Santa Cruz, CA, USA); and c-Rel, rabbit polyclonal antibody (Calbiochem, Darmstadt, Germany)) to those used by Odqvist et al 16 With a cutoff value of 30%, Compagno et al showed that about 30% of GCB-DLBCL and 60% of ABC-DLBCL had nuclear expression of NF-κB subunits (either p50 or p52) by immunohistochemistry using rabbit monoclonal antibodies (Cell Signaling Technology, Danvers, MA, USA). 8 In our cohort, 36% of GCB-DLBCL and 43% of ABC-DLBCL expressed either p50 or p52, which are similar to their results in GCB-DLBCL (30%) but slightly lower in ABC-DLBCL (43%).…”

“…Although constitutive activation of NF-κB is a hallmark of ABC-DLBCL, several groups have shown that NF-κB is also activated in a subset of GCB NF-κB subunits and clinical outcome in DLBCL DLBCLs. 8,10,16 Our data, combined with others, suggests that activation of the NF-κB pathway is not limited to ABC-DLBCL. We also found 23 cases with coexpression of p50 and p52, suggesting that activation of the classical and alternative pathways are not mutually exclusive in DLBCL.…”

“…More importantly, they did not specifically exclude cases with infection by Epstein-Barr virus, which is known to activate the NF-κB pathway 26 or had relatively small cohort of patients. 16 In this study, expression of p50, p52, p65, RELB, and c-Rel was observed in 34%, 12%, 20%, 14% and 23% of patients, respectively, and expression of p50/p65, p50/c-Rel and p52/RELB dimers was seen in 11%, 11% and 3% of patients, respectively. These data are similar to that reported by Odqvist and Co-workers 16 who used similar cutoffs, except that the expression frequency of class II molecules showed significant differences.…”

“…The cutoff scores for these markers used in this study were as follows: 20% for CD30 and p53; 30% for CD10 and BCL6; 40% for MYC; 50% for pSTAT3; 60% for GCET1, MUM1 and FOXP1; and 70% for BCL2. The cutoff values for NF-κB subunits were: p50, ≥ 20%; p52, ≥ 40%; p65, ≥ 30%; 16 RELB, ≥ 10%; and c-Rel, ≥ 20%.…”

“…Moreover, most previous studies have evaluated only a subset of the NF-κB subunits. [8][9][10][11][12][13][14][15] There are only two studies using all five subunits in DLBCL-a cohort of 88 patients with DLBCL by Odqvist et al 16 and a cohort of 45 patients with testicular DLBCL by Menter et al 17 In the current study, we evaluated expression of all five subunits of the NF-κB protein by immunohistochemistry and its clinical implications in a large cohort of patients with de novo DLBCL.…”