Follicle center lymphoma is associated with significantly elevated levels of BCL-6 expression among lymphoma subtypes, independent of chromosome 3q27 rearrangements

Abstract

The BCL-6 gene, located on chromosome 3q27, is implicated in the normal germinal center formation and is frequently rearranged in a wide spectrum of lymphomas. However the links between genetic alterations and expression of the gene are not clearly determined. We established a quantitative RT-PCR assay based on TaqMan technology to quantify BCL-6 mRNA expression in different subtypes of lymphomas and to compare the level of expression in lymphomas characterized by the presence or absence of BCL-6 translocation. Total RNA was extracted from 105 nodes biopsies (35 diffuse large B cell lymphomas (DLBCL); 26 follicle center lymphomas (FCL); 7 marginal zone lymphomas (MZL); 6 mantle cell lymphomas (MCL); 6 chronic lymphocytic leukemia (CLL); 5 T cell lymphomas (TCL); 7 classical Hodgkin diseases (HD); 6 nodal metastasis (NM); and 7 reactive hyperplasia (RH)). BCL-6 gene rearrangement was assessed by Southern blot analysis in 75% of 3q27 + DLBCL (n = 20) cases and 67% of 3q27 + cases (n = 10). The highest level of relative BCL-6 expression was observed in FCL (9.12 ± 7.28) comparatively to the other lymphoma subtypes including DLBCL (2.53 ± 1.82; P Ͻ 0.001), MCL (1.23 ± 0.73), MZL (1.49 ± 1.3), HD (1.60 ± 1.00), TCL (1.75 ± 1.64), but also RH (3.91 ± 3.12) or NM (1.95 ± 2.6). Among the 26 FCL cases, we observed a lower expression in grade 3 (n = 8) than in grade 1/2 (P Ͻ 0.001). Conversely, we failed to show any difference between 3q27 + DLBCL and 3q27 − DLBCL cases (P = 0.42). Paradoxically BCL-6 expression in 3q27 + FCL (n = 10) was significantly lower than in 3q27 − FCL cases (P = 0.035). Finally, this study showed that BCL-6 expression in lymphoma is largely independent of chromosome 3q27 rearrangement and is more related to the histological subtype. Clinical implication and alternative deregulation pathways of BCL-6 expression remain to be determined.

Clinical and biological relevance of single-nucleotide polymorphisms and acquired somatic mutations of the BCL6 first intron in follicular lymphoma

“…The mRNA BCL6 gene expression was assessed by a real-time quantitative RT-PCR assay in 18 available tumor samples as previously described 11 and was correlated to the mutational status. The housekeeping PBGD gene was used as internal control.…”

“…4 The third type of gene alteration is constituted by somatic mutations (SM) actively targeted to the 5 0 untranslated region of the BCL6 gene, including and largely curtailed by the first intron. 10 The mutated domain, termed the major mutation cluster (MMC), 11 is a 800 bp-domain located B650 bp downstream the TATA box in the gene promoter. SM are present in B30% of normal GC B-cells, including centroblasts and centrocytes, 12,13 40% of FL and 70% of DLBCL.…”

Expression of HYAL2 mRNA, hyaluronan and hyaluronidase in B‐cell non‐Hodgkin lymphoma: Relationship with tumor aggressiveness

“…22 Standard curves were established by serial dilutions of cDNA obtained by reverse transcription of 1 g total RNA purified from RL lymphoma line. Amounts covered the range from 0.03125 to 1 g RNA.…”

Characterization of three t(3;8)(q27;q24) translocations from diffuse large B-cell lymphomas

“…1 and 2 by real-time quantitative RT-PCR as previously described. 4 Measurements were performed in hexaplicate for both cases. 11 GC-type DLBCL without 3q27 rearrangement were used as controls and measured in duplicate.…”

“…2,3 LMO2 encodes a LIM-only protein comprised of two LIM domains characterized as a cysteine-rich motif consisting of two tandemly repeated zinc fingers and is considered to be a transcriptional regulator through the interactions with its partners, including LDB1 (CLIM2/NLI1), GATA1, TAL1(SCL) and E47, to form a multi-complex in which LMO2 functions as a bridging molecule with the two arms of GATA1 and TAL1/E47 bound to relevant DNA motifs. 4 MicroRNAs (miRNAs) are a recently discovered class of small (E22-nt), non-coding RNAs that regulate gene expression via the RNA interference pathway either to promote degradation of the target mRNA or to repress its translation. There was increasing evidence showing that miRNAs had crucial functions in hematopoiesis, as well as leukemia (reviewed in Ref.…”