Two patterns of chromosomal breakpoint locations on the immunoglobulin heavy-chain locus in B-cell lymphomas with t(3;14)(q27;q32): relevance to histology

Analysis of clinical characteristics of 516 patients with non-Hodgkin's lymphoma in Shanghai area

The aim was to determine the clinical and cytogenetic characteristics of non-Hodgkin's lymphoma (NHL) in Shanghai. A retrospective analysis was conducted in 516 patients with NHL. Patient clinical data, including age, sex, diagnosis, immunophenotypes, and karyotypes, were collected. The median age was 58 years. There was a male predominance in all NHL, except extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. Patients with B cell NHL (1.5%) expressed CD3. T cell NHL patients (11.5%) expressed CD20. Epstein-Barr virus latent integral membrane protein 1, BCL6, CD10, Bcl-2, CD68, myeloperoxidase, CD99, CD30, CD15, and CD43 were present in various types of NHL. Complex karyotypes accounted for 92.3% of the 73.7% patients with abnormal karyotypes. Immunoglobin heavy chain gene translocation was present in 60.3% of B cell and 23.7% of T/NK cell neoplasms. Understanding the complex clinicopathological and molecular features of NHL may help with prognosis and serve as targets for treatments.

The costimulatory molecule CD70 is regulated by distinct molecular mechanisms and is associated with overall survival in diffuse large B-cell lymphoma

In diffuse large B-cell lymphomas (DLBCL), a recurrent deletion of the 19p13 region has recently been described. CD70 and TNFSF9 genes are suspected tumor suppressor genes, but previous studies suggest an oncogenic role for CD70. Therefore, we studied the consequences of variation in CD70 copy number and epigenetic modifications on CD70 expression. Copy-number variation was investigated in 144 de novo DLBCL tissues by comparative genomic hybridization array and quantitative multiplex PCR. Gene expression was assessed by quantitative RT-PCR, and CD70 promoter methylation was determined by pyrosequencing. The 19p13.3.2 region was deleted in 21 (14.6%) cases, which allowed the minimal commonly deleted region of 57 Kb that exclusively includes the CD70 gene to be defined. Homozygous deletions were observed in four (2.7%) cases, and acquired single-nucleotide variations of CD70 were detected in nine (6.3%) cases. CD70 was highly expressed in both germinal centre B-cell-like (GCB) and activated B-cell-like (ABC) DLBCL compared to normal tissue, with distinct molecular mechanisms of mRNA expression regulation. A gene dosage effect was observed in the GCB subtype, whereas promoter methylation was the predominant mechanism of down regulation in the ABC subtype. However, high CD70 expression levels correlated to shorter overall survival in both the GCB (P = 0.0021) and the ABC (P =0.0158) subtypes. In conclusion, CD70 is targeted by recurrent deletions, somatic mutations and promoter hypermethylation, but its high level of expression is related to an unfavorable outcome, indicating that this molecule may constitute a potential therapeutic target in selected DLBCL.

Early steps of follicular lymphoma pathogenesis

Follicular lymphoma (FL) pathogenesis is a complex and fascinating multi-hit process, escalating along successive derailments of the distinctive molecular and cellular mechanisms paving B-cell differentiation and activation. This progressive subversion of B-cell receptor diversification mechanisms and B-cell homeostasis likely occurs during a protracted preclinical phase of asymptomatic growth, in which premalignant clones already disseminate and establish "niches" in secondary lymphoid organs. Following FL diagnosis, a parallel indolent behavior is observed in most patients, slowly progressing over a period of many years, to eventually generate a highly refractory (and in some case transform into an aggressive subtype of) lymphoma. Novel insights in human germinal center B-cell biology recently allowed a more comprehensive understanding of the various illegitimate events sequentially involved in the premalignant progression phases. In this review, we will discuss how these new data have modified our perception of early FL pathogenesis, the new questions and challenges it opened up, and how this knowledge could impact on innovative programs of early detection, follow-up, and patient management.

Follicular lymphoma grade 3B

Follicular lymphoma (FL) grade 3B (FL3B) is defined as FL with more than 15% centroblasts per high resolution field present as solid sheets. Coexistence with diffuse large B-cell lymphoma (DLBCL) is frequent. In contrast to other FL, FL3B frequently lack CD10 expression (approximately 50% of cases), show lower probability of BCL2 expression (69% positive) and increased TP53 expression (31% positive). The t(14;18) hallmark translocation of FL is present in only around 13% of FL3B. In contrast, translocations affecting the BCL6 locus in 3q27 are frequent (44%). Overall, FL3B in many features resembles DLBCL. The presence of a diffuse component in FL3B has been related to an unfavorable outcome except for pediatric FL3B that presents in 60% of the cases this DLBCL component. In this chapter we sought to review the present knowledge on morphological, cytogenetic and molecular features in FL3B.

Diffuse large B-cell lymphomas with CDKN2A deletion have a distinct gene expression signature and a poor prognosis under R-CHOP treatment: a GELA study

Genomic alterations play a crucial role in the development and progression of diffuse large B-cell lymphomas (DLBCLs). We determined gene copy number alterations (GCNAs) of TP53, CDKN2A, CDKN1B, BCL2, MYC, REL, and RB1 with a single polymerase chain reaction (PCR) assay (quantitative multiplex PCR of short fragments [QMPSF]) in a cohort of 114 patients with DLBCL to assess their prognostic value and relationship with the gene expression profile. Losses of TP53 and CDKN2A, observed in 8% and 35% of patients, respectively, were significantly associated with a shorter survival after rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) treatment, independently of the International Prognostic Index and of the cell of origin. Analysis of the 9p21 genomic region indicated that transcripts encoding p14ARF and p16INK4A were both disrupted in most patients with CDKN2A deletion. These patients predominantly had an activated B-cell profile and showed a specific gene expression signature, characterized by dysregulation of the RB/E2F pathway, activation of cellular metabolism, and decreased immune and inflammatory responses. These features may constitute the molecular basis sustaining the unfavorable outcome and chemoresistance of this DLBCL subgroup. Detection of TP53 and CDKN2A loss by QMPSF is a powerful tool that could be used for patient stratification in future clinical trials.

BCL6 gene amplification/3q27 gain is associated with unique clinicopathological characteristics among follicular lymphoma without BCL2 gene translocation

Although approximately 10-20% cases of follicular lymphoma lack BCL2 gene rearrangement, there are few reports having described the alternative genetic aberrations and their association about clinicopathological features. In this study, analysis by Fluorescence in situ hybridization of BCL6 gene aberrations in 100 follicular lymphoma cases without IGH/BCL2 rearrangement resulted in the identification of four subgroups. Group I: BCL6 gene rearrangement (n=41); Group II: BCL6 gene amplification/3q27 gain (n=30); Group III: the absence of both (n=23); and Group IV: the presence of both (n=6). Group II showed higher grade morphology (Grade 3a/b: 93%), higher bcl2 and MUM1 expression (73 and 57%, respectively), and more frequent combination with BCL2 gene amplification/18q21 gain (90%) than the other groups. BCL6 gene aberration, especially amplification/3q27 gain, indicates the presence of certain morphological and phenotypical findings in follicular lymphoma cases without IGH/BCL2 rearrangement.

Chromosomal translocations in cancer

Genetic alterations in DNA can lead to cancer when it is present in proto-oncogenes, tumor suppressor genes, DNA repair genes etc. Examples of such alterations include deletions, inversions and chromosomal translocations. Among these rearrangements chromosomal translocations are considered as the primary cause for many cancers including lymphoma, leukemia and some solid tumors. Chromosomal translocations in certain cases can result either in the fusion of genes or in bringing genes close to enhancer or promoter elements, hence leading to their altered expression. Moreover, chromosomal translocations are used as diagnostic markers for cancer and its therapeutics. In the first part of this review, we summarize the well-studied chromosomal translocations in cancer. Although the mechanism of formation of most of these translocations is still unclear, in the second part we discuss the recent advances in this area of research.

Molecular pathways in follicular lymphoma

Follicular lymphoma (FL) is one of the most common B-cell non-Hodgkin's lymphomas. The initiating genetic event found in approximately 90% of FL is the t(14;18), causing constitutive expression of the antiapoptotic BCL-2 protein. The exact secondary alterations leading to full FL development are still poorly defined. In this review, we address (i) the genetic pathways associated with tumorigenesis and progression of FL, (ii) the role of micro-environmental factors with emphasis on B-cell receptor ligands and (iii) lymphoma models in mice and what they teach us about lymphomagenesis in man.

The BCL6 proto-oncogene: a leading role during germinal center development and lymphomagenesis

The BCL6 proto-oncogene encodes a nuclear transcriptional repressor, with pivotal roles in germinal center (GC) formation and regulation of lymphocyte function, differentiation, and survival. BCL6 suppresses p53 in GCB-cells and its constitutive expression can protect B-cell lines from apoptosis induced by DNA damage. BCL6-mediated expression may allow GCB-cells to sustain the low levels of physiological DNA breaks related to somatic mutation (SM) and immunoglobulin class switch recombination which physiologically occur in GCB-cells. Three types of genetic events occur in the BCL6 locus and involve invariably the 5' non-coding region and include translocations, deletions and SM actively targeted to the 5' untranslated region. These acquired mutations occur independently of translocations but may be involved in the deregulation of the gene and/or translocation mechanisms. The favorable prognostic value of high levels of BCL6 gene expression in NHL seems well-established. By contrast, the relevance of SM or translocation of the gene remains unclear. However, it is likely that non-Hodgkin's lymphomas (NHL) harboring the most frequent translocation involving BCL6, i.e. t(3;14), are characterized by a common cell of origin and similar oncogenic mechanisms. Several experiments and mouse models mimicking BCL6 translocation occurring in human lymphoma have demonstrated the oncogenic role of BCL6 and constitute a rational to consider BCL6 as a new therapeutic target in NHL. BCL6 blockade can be achieved by different strategies which include siRNA, interference by specific peptides or regulation of BCL6 acetylation by pharmacological agents such as SAHA or niacinamide and would be applicable to most type of B-cell NHL.