The configuration of the immunoglobulin genes in B cell chronic lymphocytic leukemia

Two recurrent types of IGH::5' BCL2 breakpoints representing cytogenetic ins(14;18)(q32;q21q21) and t(14;18)(q32;q21), mediated by the VDJ and class switch recombination processes, respectively

We describe two types of IGH::BCL2 breakpoints involving the 5' region of BCL2 (5' BCL2). One was ins(14;18)(q32;q21q21) observed in 2 follicular lymphoma (FL) cases, in which IGH was cleaved at 3' of IGHD and 5' of IGHJ and BCL2 was cleaved at 5' BCL2 and downstream regions, and a 281- or 201-kilobase pair fragment containing the BCL2 protein-coding sequences was invertedly inserted into IGH. In another type observed in 2 FL and 2 chronic lymphocytic leukemia (CLL) cases, breakage and reunion occurred within the switch region associated with IGHM (Sµ) and 5' BCL2, creating IGH Sµ::5' BCL2 fusion sequences on der(18)t(14;18)(q32;q21). The former is considered to be mediated by VDJ-recombination, while the latter by the class switch recombination process. There were no particular features in FL or CLL cases with IGH::5' BCL2 breakpoints compared with those with t(14;18)(q32;q21)/IGH::BCL2 involving the 3' breakpoint cluster regions.

Immunoglobulin somatic hypermutation has clinical impact in DLBCL and potential implications for immune checkpoint blockade and neoantigen-based immunotherapies

Background

Diffuse large B-cell lymphoma (DLBCL) harbors somatic hypermutation (SHM) in the immunoglobulin heavy chain and light chain variable region genes, IGHV and IGK/LV. Recent studies have revealed that IGV SHM creates neoantigens that activate T-cell responses against B-cell lymphoma.

Methods

To determine the clinical relevance of IGV SHM in DLBCL treated with standard immunochemotherapy, we performed next-generation sequencing of the immunoglobulin variable regions and complementarity determining region 3 (CDR3) for 378 patients with de novo DLBCL. The prognostic effects of IGV SHM and ongoing SHM or intra-clonal heterogeneity were analyzed in the training (192 patients), validation (186 patients), and overall DLBCL cohorts. To gain mechanistic insight, we analyzed the predicted IG-derived neoantigens’ immunogenicity potential, determined by the major histocompatibility complex-binding affinity and the frequency-of-occurrence of T cell-exposed motifs (TCEMs) in a TCEM repertoire derived from human proteome, microbiome, and pathogen databases. Furthermore, IGV SHM was correlated with molecular characteristics of DLBCL and PD-1/L1 expression in the tumor microenvironment assessed by fluorescent multiplex immunohistochemistry.

Results

SHM was commonly found in IGHV and less frequently in IGK/LV. High levels of clonal IGHV SHM (SHM^high) were associated with prolonged overall survival in DLBCL patients, particularly those without BCL2 or MYC translocation. In contrast, long heavy chain CDR3 length, the presence of IGHV ongoing SHM in DLBCL, and high clonal IGK/LV SHM in germinal center B-cell–like (GCB)-DLBCL were associated with poor prognosis. These prognostic effects were significant in both the training and validation sets. By prediction, the SHM^high groups harbored more potentially immune-stimulatory neoantigens with high binding affinity and rare TCEMs. PD-1/L1 expression in CD8⁺ T cells was significantly lower in IGHV SHM^high than in SHM^low patients with activated B-cell–like DLBCL, whereas PD-1 expression in CD4⁺ T cells and PD-L1 expression in natural killer cells were higher in IGK/LV SHM^high than in SHM^low patients with GCB-DLBCL. PD-L1/L2 (9p24.1) amplification was associated with high IGHV SHM and ongoing SHM.

Conclusions

These results show for the first time that IGV SHM^high and ongoing SHM have prognostic effects in DLBCL and potential implications for PD-1/PD-L1 blockade and neoantigen-based immunotherapies.

Hypercalcemia and osteolytic bone lesions as the major symptoms in a chronic lymphocytic leukemia/small lymphocytic lymphoma patient: a rare case

We report a 40-year-old woman who presented with multiple osteolytic bone lesions and hypercalcemia, which are rarely caused by chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Although receiving intensive chemotherapy and allogeneic transplantation, the patient had a poor outcome with an overall survival of 2 years. To our knowledge, this presentation is extremely rare for B-chronic lymphocytic leukemia, and new treatment strategies may be needed for long-term control of the disease.

BCL11A expression in acute phase chronic myeloid leukemia

Chronic myeloid leukemia (CML) has chronic and acute phases. In chronic phase myeloid differentiation is preserved whereas in acute phase myeloid differentiation is blocked. Acute phase CML resembles acute myeloid leukemia (AML). Chronic phase CML is caused by BCR-ABL1. What additional mutation(s) cause transition to acute phase is unknown and may differ in different persons with CML. BCL11A encodes a transcription factor and is aberrantly-expressed in several haematological and solid neoplasms. We analyzed BCL11A mRNA levels in subjects with chronic and acute phase CML. BCL11A transcript levels were increased in subjects with CML in acute phase compared with those in normals and in subjects in chronic phase including some subjects studied in both phases. BCL11A mRNA levels were correlated with percent bone marrow blasts and significantly higher in lymphoid versus myeloid blast crisis. Differentiation of K562 with butyric acid, a CML cell line, decreased BCL11A mRNA levels. Cytology and flow cytometry analyses showed that ectopic expression of BCL11A in K562 cells blocked differentiation. These data suggest BCL11A may operate in transformation of CML from chronic to acute phase in some persons.

Five important advances in hematopathology

CONTEXT

Hematopathology is a dynamic field that has always been on the frontier of clinical research within the scope of pathology. Several recent developments in hematopathology will likely affect its practice clinically.

OBJECTIVE

To review 5 important recent advances in hematopathology: (1) detection and prognostic implication of MYC in diffuse large B-cell lymphomas, (2) determining origin and prognosis through immunoglobulin gene usage in mature B-cell neoplasms, (3)detecting minimal residual disease in multiple myeloma, (4) using genome-wide analysis in myelodysplastic syndromes, and (5) employing whole-genome sequencing in acute myeloid leukemias.

DATA SOURCES

Literature review and the authors' experiences in an academic center.

CONCLUSIONS

These advances will bring hematopathology into a new molecular era and help us to better understand the molecular, pathologic mechanisms of lymphomas, leukemias, myelomas, and myelodysplastic syndromes. They will help us to identify diagnostic and prognostic markers and eventually provide new therapeutic targets and treatments for these diseases.

Role of molecular studies in the classification of lymphoma

The classification of lymphomas has historically lacked both precision and accuracy, potentially compromising both optimal diagnosis and therapy. The genetic characterization of key oncogenic events and the advent of expression profiling have afforded the opportunity to understand, diagnose and treat these diseases in a much more rational and targeted manner. As exciting as these new and testable data are, it is also worth noting that molecular genetic analysis of the tumor in isolation will not be the sole arbiter of patient outcome. It is likely that we will remain reliant on traditional and sometimes subjective technologies, albeit probably to a lesser degree, with molecular studies significantly complementing, but certainly not replacing, microscopic, immunophenotypic and cytogenetic approaches. Furthermore, we will perhaps need to extend genotyping to the tumor milieu (the patient) in order to molecularly dissect drug metabolic pathways and the immune response.

Prognostic factors in chronic lymphocytic leukemia-what do we need to know?

Of all leukemias, chronic lymphocytic leukemia (CLL) shows the highest variability in its clinical presentation and course. CLL can present as an aggressive and life threatening leukemia or as an indolent form that will not require treatment over decades. The currently available clinical staging systems for CLL are simple and inexpensive but lack accuracy to predict disease progression and survival on an individual basis. The increased understanding of the key events of molecular pathogenesis has provided a plethora of novel molecular and biological factors that correlate with the outcome of CLL. This Review provides a concise discussion of the most important discoveries and gives guidance on how to implement novel prognostic tools in the clinical management of CLL by applying the criteria of evidence, relevance, and simplicity to the selection of prognostic markers.

Report of two novel chromosomal translocations in chronic lymphocytic leukemia

Two novel chromosomal translocations were identified in 2 patients with chronic lymphocytic leukemia (CLL). Case 1: 60 year-old male, stage Rai 0/Binet A, with mutated immunoglobulin heavy (IgH) and lambda (Iglambda) light chain genes; karyotype: 46, XY, t(9;12)(q12;p11) [3]/ 46, XY [22]. Case 2: 56 year-old male, stage Rai 2/Binet B, with mutated IgH and unmutated Iglambda genes; karyotype: 46, XY, add(10)(q26), t(13;18)(q14;q21) [8]/ 46, XY [27]. Although both translocations are novel, the involved breakpoints (especially 13q14 and 18q21) have been reported to participate in various aberrations in CLL patients. Aberrations affecting bands 9q12 and 12p11, as in case 1, are generally rare.

Frequency of 5'IGH deletions in B-cell chronic lymphocytic leukemia

In a retrospective analysis of a large group of cases (n=291) with B-cell CLL diagnosis, the various characteristics of IGH aberrations as identified by fluorescence in situ hybridization (FISH) probes were studied. Conventional cytogenetic and FISH studies with the standard panel (13q14, 11q13, 17p13, 12 centromere), and with IGH break-apart probes were done for each case. Abnormal karyotypes were detected with conventional cytogenetics in 29% of cases, and FISH detected abnormalities in 70%. Deletion of 13q14 was the most frequent anomaly, followed by trisomy 12, deletion of 11q, and deletion of 17p. Among the IGH abnormalities detected, translocations with unknown partners (split signals) occurred in only a small group of patients (15%). Instead, deletion of 5'IGH, corresponding to the variable IGH segment (IGH(V)) was the most recurrent aberration, observed in 82% (the second most common finding among our patients). This deletion was associated with good prognostic markers: 13q14 deletion, normal karyotype, and CD38 and ZAP-70 negative expression. Although not exclusive to CLL, the deletion occurred in a high frequency, in contrast to its rarity in other B-cell lymphoproliferative disorders. Longitudinal studies are warranted, to determine when in the disease progression this abnormality is acquired, as a potential early marker, and its impact on the natural history of CLL.

Cytogenetic characterisation in Chinese patients with chronic lymphocytic leukemia: a prospective, multicenter study on 143 cases analysed with interphase fluorescence in situ hybridisation

Chronic lymphocytic leukemia (CLL) is infrequent in Chinese people. Conventional cytogenetic analysis underestimates the frequency of chromosome aberrations in CLL due to the low rate of spontaneous mitoses. The aim of this study was to prospectively explore the frequency of chromosomal abnormalities in Chinese patients with CLL using interphase fluorescence in situ hybridisation (FISH) and probes for 12 centromere, 13q14, 14q32, 17p13, 11q22 and 6q23 on 143 patients with CLL. Molecular cytogenetic aberrations were found in 104 patients (72.7%) and 40 patients (28.0%) with more than two abnormalities. The most frequent abnormality was del(13q14) (47.6%), followed by trisomy 12 (21.7%), 14q32 translocation (19.6%), del(17p13) (12.6%), del(11q22) (11.9%) and del(6q23) (4.9%), respectively. The percentages of patients with aberrations by FISH were 75.4%, 72.3% and 67.7% for Binet stages A, B and C, respectively. In early stage (Binet A), del(13q14) aberration was more frequent than in Binet B and C (61.5% vs. 31.9% and 41.9%) (P=0.021). Patients with advanced stage (Binet C) had more frequent del(17p13) aberration than in Binet A and B (32.3% vs. 9.2% and 4.3%) (P=0.008). It was showed that the frequencies of the chromosomal abnormalities in our study population were similar to the frequencies in Western countries.

BCL-2 phosphorylation modulates sensitivity to the BH3 mimetic GX15-070 (Obatoclax) and reduces its synergistic interaction with bortezomib in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (CLL) is a B-cell lymphoid neoplasm with deregulated apoptosis and overexpression of several antiapoptotic BCL-2 proteins. GX15-070/Obatoclax is a small-molecule BH3 mimetic compound that has shown activity against several hematologic malignancies and solid tumors. In the present work, we report that GX15-070 led to the disruption of BCL-2/BIM and MCL-1/BAK complexes in CLL cells, followed by the activation of the mitochondrial apoptotic pathway. CLL cells showed lower sensitivity to GX15-070 than primary mantle cell lymphoma (MCL) ones, in correlation with higher levels of phosphorylated BCL-2 at serine 70 residue (pBCL-2(Ser70)) in CLL cells. Decrease in BCL-2 phosphorylation by extracellular signal-regulated kinase (ERK)1/2 inhibition increased CLL sensitivity to GX15-070, while blocking BCL-2 dephosphorylation using a PP2A antagonist reduced the activity of this BH3 mimetic. GX15-070 activity was increased by cotreatment with the proteasome inhibitor bortezomib. However, as proteasome inhibition led to the accumulation of phosphorylated BCL-2, the degree of interaction between GX15-070 and bortezomib was regulated by basal pBCL-2(Ser70) levels. These results support the role of BCL-2 phosphorylation as a mechanism of resistance to BH3 mimetic compounds, and demonstrate that combination approaches including ERK inhibitors could enhance BH3 mimetics activity both alone or in combination with proteasome inhibitors.

Validation of a targeted DNA microarray for the clinical evaluation of recurrent abnormalities in chronic lymphocytic leukemia

Recurrent genomic alterations, mainly losses and gains of specific chromosomes and/or regions, in chronic lymphocytic leukemia (CLL) are recognized as important independent predictors of prognosis and disease progression. The current standard clinical practice for identifying these alterations is chromosome analysis and in situ hybridization with probes targeting 4-5 chromosome regions. We sought to apply array comparative genomic hybridization (array-CGH) technology for the simultaneous detection of genomic imbalances of all loci implicated in CLL. DNA from enriched B-cells from CLL patients were analyzed by array-CGH on a customized CLL BAC array. Copy number changes were detected in 87% of samples with a sensitivity of 100% in samples with clonal abnormalities present in at least 23% of the cells. Furthermore, in nine cases genomic alterations were observed that were undetectable by standard cytogenetic and/or FISH analyses. One of these patients had a 13q14 deletion that was missed by the clinical CLL FISH panel probe set. Our results suggest that a subset of potentially significant genomic alterations in CLL is being missed by the current available techniques. Furthermore, this pilot study clearly shows the robustness, high sensitivity, and high specificity for the targeted CLL microarray analysis as well as the potential for use in routine screening in CLL.

Chronic lymphocytic leukemia FISH panel: impact on diagnosis

Interphase fluorescence in situ hybridization (FISH) is an alternative to conventional chromosome analysis of chronic lymphocytic leukemia (CLL) cells. We analyzed 172 samples from 136 possible CLL cases using a FISH panel. Reflex testing with probes to CCND1, BCL2, BCL3, BCL11A, c-MYC, MALT1, and a break-apart immunoglobulin heavy chain (IGH) probe was done if more than 2 signals for 14q32 occurred. For 111 cases, there were sufficient data for analysis. Of 111 cases, 81 (72.9%) had 1 or more genetic abnormalities. The most frequent abnormality was 13q-, followed by trisomy 12, 11q-, and 17p-. In 13 cases, there were IGH abnormalities. Two cases with CCND1/IGH fusion were reclassified as mantle cell lymphoma. Four CLL cases had IGH fusion with BCL2, BCL3 (2 cases), and BCL11A; no fusion partner was detected in 7 cases. Morphologic features were atypical for CLL in 2 cases with IGH fusion (BCL11A and BCL3). The FISH CLL panel is useful to identify prognostic aberrations and to clarify diagnosis in cases with unusual morphologic features.

Molecular genetic analysis of haematological malignancies II: mature lymphoid neoplasms

Molecular genetic techniques have become an integral part of the diagnostic assessment for many lymphomas and other chronic lymphoid neoplasms. The demonstration of a clonal immunoglobulin or T cell receptor gene rearrangement offers a useful diagnostic tool in cases where the diagnosis is equivocal. Molecular genetic detection of other genomic rearrangements may not only assist with the diagnosis but can also provide important prognostic information. Many of these rearrangements can act as molecular markers for the detection of low levels of residual disease. In this review, we discuss the applications of molecular genetic analysis to the chronic lymphoid malignancies. The review concentrates on those disorders for which molecular genetic analysis can offer diagnostic and/or prognostic information.

Telomeric IGH losses detectable by fluorescence in situ hybridization in chronic lymphocytic leukemia reflect somatic VH recombination events

Routine interphase fluorescence in situ hybridization (FISH) analysis of chronic lymphocytic leukemia (CLL) with LSI IGH/CCND1 assay, applied to differentiate CLL from leukemic mantle cell lymphoma, identified a subset of cases (42/174) with translocation-like IGH signal pattern. To unravel the underlying 14q32/IGH aberrations, 14 of these cases were subjected to cytogenetic, detailed FISH, and V(H) mutation analyses. FISH identified cryptic losses of various portions of the IGHV region in all 14 cases. Fine mapping of these V(H) deletions revealed a strict correlation between their distal border and localization of the used VH gene, suggesting that they are not oncogenic but reflect physiological events accompanying somatic V-D-J assembly. This hypothesis was further supported by FISH analysis of 20 CLL and hairy cell leukemia cases with the known V(H) usage showing a constant loss of sequences proximal to the used gene, identification of V(H) deletions in normal B cells, and their exclusive demonstration in B cell malignancies, but not of T cell and myeloid linage. Given that these cryptic physiological VH losses in B cells may seriously complicate analysis of B cell leukemia/lymphoma and lead to false conclusions, FISH users should take them into consideration when interpreting IGH aberrations in these malignancies.

Mitogen induced activation, proliferation and surface antigen expression patterns in unmutated and hypermutated chronic lymphocytic leukemia cells

OBJECTIVES

To determine whether the immunoglobulin V(H) gene mutational status has an effect on the activation, proliferation and surface antigen expression of chronic lymphocytic leukemia (CLL) cells when stimulated in vitro.

METHODS

The proliferation and activation responses of CLL cells were studied in 22-immunoglobulin gene V(H) unmutated (UM-CLL) and 12 hypermutated (M-CLL) CLL cases in 4-day cultures. As the mitogen responses have been previously shown to be diverse in CLL, a case-specific strategy based on optimized mitogen combinations (OMCs) of interleukin-2 (IL-2), 12-O-tetradecanoylphorbol 13-acetate (TPA), Staphylococcus aureus Cowan 1 (SAC), and human recombinant tumor necrosis factor alpha (TNF) was applied in cell stimulation. The expression of 23 surface membrane antigens (CD5, CD11c, CD19, CD20, CD21, CD22, CD23, CD25, CD27, CD38, CD40, CD45, CD45RA, CD45RO, CD79b, CD80, CD95, CD124, CD126, CD130, FMC7, IgD, and IgM) was studied by flow cytometry at days 0 and 4.

RESULTS

The proliferation and activation responses were similar in UM-CLL and M-CLL when OMCs contained IL-2, TPA or TNF. SAC induced faster proliferation in UM-CLL than in M-CLL. OMC stimulation induced preferential down-regulation of growth- promoting cell surface receptors CD5, CD21, and CD124 and preferential up-regulation of growth-inhibiting antigen CD80 in M-CLL.

CONCLUSIONS

Difference in immunophenotypic evolution of UM-CLL and M-CLL can be demonstrated if appropriate matrix signals are provided. The pathways for CD5, CD21, CD124 (IL4R), and CD80 (B7-1) regulation should be further explored in relation with somatic hypermutation and outcome of CLL.

Incidence of chromosomal anomalies detected with FISH and their clinical correlations in B-chronic lymphocytic leukemia

B-chronic lymphocytic leukemia (B-CLL) is the most common adult leukemia. Molecular genetic characterization of B-CLL has made significant progress and typical chromosomal anomalies have been assessed. The most frequent chromosomal abnormalities are deletions at 13q14, 17p13, and 11q22 approximately q23 and trisomy 12. The aim of this study was to establish incidence of chromosomal changes in bone marrow or peripheral blood cells (or both) of B-CLL patients using a molecular cytogenetic method, interphase fluorescence in situ hybridization (I-FISH), and to evaluate the prognostic implications. We performed I-FISH on bone marrow and blood smears from 217 B-CLL patients (124 male, 93 female). Trisomy 12 was found in 35 of the 217 (16%); deletion 13q14 was analyzed in 207 patients and found in 112 (54%). Deletion 17p13 was found in 34 (16%) out of 206 examined. Deletion of 11q23 was analyzed in 56 patients and was present in 7 (12%). Statistical analyses were performed to correlate the molecular-cytogenetic findings with disease status (stable versus progressive), Rai stage, CD38/CD19 antigen coexpression, immunoglobulin variable heavy chain (IgV(H)) mutational pattern, and other clinical and laboratory parameters. No apparent differences in distribution were noted for anomalies +12, del(13)(q14), or del(17)(p13) among patients with stable and progressive disease, and no consistent pattern in the distribution of type of genomic changes were found among various Rai stages and in CD38/CD19-positive or -negative patients. Patients without IgV(H) mutation had a worse prognosis; however, distribution of chromosomal abnormalities identified with FISH was the same for patients with and without IgV(H) mutations.

Interphase fluorescence in situ hybridization with an IGH probe is important in the evaluation of patients with a clinical diagnosis of chronic lymphocytic leukaemia

Translocations involving IGH are common in some lymphoid malignancies but are believed to be rare in chronic lymphocytic leukaemia (CLL). To study the clinical utility of fluorescence in situ hybridization (FISH) for IGH translocations, we reviewed 1032 patients with a presumptive diagnosis of CLL. Seventy-six (7%) patients had IGH translocations. Pathology and clinical data were available for the 24 patients evaluated at the Mayo Clinic. Ten (42%) patients had IGH/cyclin D1 fusion and were diagnosed with mantle cell lymphoma (MCL). The immunophenotype was typical of MCL in three of these patients and atypical for MCL in seven patients. One patient had biclonal disease with typical MCL and CLL with IGH/BCL-2. Eleven (46%) patients had IGH/BCL-2 fusion including the patient with biclonal disease. Two of these patients had leukaemic phase follicular lymphoma and nine patients had CLL. The median progression-free survival of patients with CLL and IGH/BCL-2 translocation was 20.6 months. The two patients with IGH/BCL-3 fusion (one of these also had IGH/BCL-11a) had rapid disease progression. The IGH partner gene was not identified in two patients. We conclude that use of an IGH probe in FISH analysis of monoclonal B-cell lymphocytosis improves diagnostic precision and could have prognostic value in patients with CLL.

Fluorescent-labeled DNA probes applied to novel biological aspects of B-cell chronic lymphocytic leukemia

Fluorescent-labeled DNA probes were used to study 52 chronic lymphocytic leukemia (B-CLL) patients for (1) disease progression, (2) angiogenesis genes, (3) T-cell leukemia 1 gene (TCL1), (4) immunoglobulin heavy chain variable region (IGHv) and (5) chromosome 6q. Compared to stable disease, more patients with progressive disease had > or =2 anomalies and a high percentage of neoplastic nuclei. Anomalies of genes for basic fibroblast growth factor, interleukin 4, vascular endothelial growth factor or TCL1 were not detected. Deletions in IGHv occurred in 25% of patients and correlated with IGHv gene expression. Probes for 6q23 detected more deletions in 6q than probes for 6q21.

Analysis of VH gene sequences using two web-based immunogenetics resources gives different results, but the affinity maturation status of chronic lymphocytic leukaemia clones as assessed from either of the resulting data sets has no prognostic significance

Some cellular and molecular features of chronic lymphocytic leukaemia (CLL) cells that are associated with prognosis may reflect the context within which their progenitors encountered antigen. It follows that the nature of antigen drive in CLL could influence the clinical course and we were prompted to assess the impact, if any, of affinity maturation (an antigen-driven process) on prognosis. Statistical models for assessing affinity maturation status are typically applied to V(H) gene sequence data analysed using a web-based resource like IMGT or VBASE. Since these resources differ with respect to some key relevant features, we evaluated a cohort of CLL cases by applying statistical models to V(H) data derived from both IMGT and VBASE. Important differences between the resulting data sets became apparent. These resulted from database variance and because IMGT and VBASE define complementarity-determining and framework regions (CDRs, FRs) in different ways. Thus, the numbers of mutations identified and their distribution between CDRs/FRs varied between the data sets for the majority of clones. Consequently, two different but overlapping sets of cases with evidence of affinity maturation were defined. Notwithstanding their differences, no significant associations of affinity maturation status with CD38 expression, p53 functional status or survival were identifiable in either data set.

BCL11A-dependent recruitment of SIRT1 to a promoter template in mammalian cells results in histone deacetylation and transcriptional repression

The B cell leukemia 11A protein (BCL11A/Evi9/CTIP1) has been implicated in hematopoietic cell development and malignancies. BCL11A is a transcriptional repressor that binds directly to a GC-rich motif and is also recruited to a promoter template via interaction with the orphan nuclear receptor, chicken ovalbumin upstream promoter transcription factor II. In both cases, BCL11A-mediated transcriptional repression is only minimally reversed by trichostatin A, suggesting the possible lack of involvement of class I or II histone deacetylases. Nonetheless, chromatin immunoprecipitation assays revealed that expression of BCL11A in mammalian cells resulted in deacetylation of histones H3 and/or H4 that were associated with the promoter region of a reporter gene. BCL11A-mediated transcriptional repression, as well as deacetylation of histone H3/H4 in BCL11A-transfected cells, was partially reversed by nicotinamide, an inhibitor of class III histone deacetylases such as SIRT1. SIRT1 was found to interact directly with BCL11A and was recruited to the promoter template in a BCL11A-dependent manner leading to transcriptional repression. These findings define a role for SIRT1 in transcriptional repression mediated by BCL11A in mammalian cells.

Molecular diagnosis in lymphoma

The evolution of our ability to diagnose and classify lymphomas in an increasingly refined manner has paralleled the development of novel technologic approaches, with contemporary practice dependent upon the harnessing of a plethora of data that include microscopic, immunophenotypic, and genetic information. Although each of these components is currently indispensable, there is a purported progressive improvement in biologic objectivity as one maneuvers through these respective technologies. Accordingly, and in particular given the rapid pace at which key insights into lymphoma biology are emerging with microarray and other cutting-edge technologies, the role of molecular genetic testing is assuming even greater relevance. The ability to diagnose and classify lymphomas more accurately, precisely, and rationally by incorporating molecular data ought to lead to the development of more appropriate directed therapies.

Diagnosis and management of B cell chronic lymphocytic leukaemia in a cat

A four-year-old, female neutered domestic shorthair cat had a history of chronic intermittent vomiting and lymphocytosis. B cell chronic lymphocytic leukaemia was diagnosed by flow cytometry, which revealed abnormally large numbers of mature B lymphocytes in the peripheral blood. The cat was treated conservatively with antiemetic drugs and remained stable without chemotherapy for over a year.

Bcl-6 mutation status provides clinically valuable information in early-stage B-cell chronic lymphocytic leukemia

In B-cell chronic lymphocytic leukemia (B-CLL), somatic mutation of IgVH genes defines a subgroup with favorable prognosis, whereas the absence of IgVH mutations is correlated with a worse outcome. Mutations of the BCL-6 gene are also observed in a subset of B-CLL, but the clinical significance of this molecular alteration remains uncertain. We examined the distribution of IgVH and BCL-6 gene mutations in 95 well-characterized patients with Binet stage A B-CLL, and correlated them with clinical, laboratory, cytogenetic findings and disease progression. Mutations of the BCL-6 gene were observed only in cases harboring mutated IgVH. Unexpectedly, coexistence of IgVH and BCL-6 mutations was correlated with shorter treatment-free interval (TFI) compared to cases harboring only IgVH mutation (median, 55 months vs not reached; P=0.01), resembling the clinical course of unmutated IgVH cases (median TFI, 44 months). As expected, deletions of 17p13 (P53 locus) and 11q22 (ATM locus) were observed in cases with unmutated IgVH, except one patient who showed mutations of both IgVH and BCL-6. No other statistically significant differences were observed among the genetic subgroups. Our data indicate that BCL-6 mutations identify a subgroup of Binet stage A B-CLL patients with a high risk of progression despite the presence of mutated IgVH gene.

Treatment by design in leukemia, a meeting report, Philadelphia, Pennsylvania, December 2002

Novel approaches have been designed to treat leukemia based on our understanding of the genetic and biochemical lesions present in different malignancies. This meeting report summarizes some of the recent advances in leukemia treatment. Based on the discoveries of cellular oncogenes, chromosomal translocations, monoclonal antibodies, multidrug resistance pumps, signal transduction pathways, genomics/proteonomic approaches to clinical diagnosis and mutations in biochemical pathways, clinicians and basic scientists have been able to identify the particular genetic mutations and signal transduction pathways involved as well as design more appropriate treatments for the leukemia patient. This meeting report discusses these exciting new therapies and the results obtained from ongoing clinical trials. Furthermore, rational approaches to treat complications of tumor lysis syndrome by administration of the recombinant urate oxidase protein, also known as rasburicase, which corrects the biochemical defect present in humans, were discussed. Clearly, over the past 25 years, molecular biology and biotechnology has provided the hematologist/oncologist novel bullets in their arsenal that will allow treatment by design in leukemia.

Towards molecular diagnosis and targeted therapy of lymphoid malignancies

Gene expression profiling of cancer began as a research tool but is rapidly moving towards clinical application. The diagnostic category of diffuse large B-cell lymphoma (DLBCL) can now be viewed as an amalgam of several different diseases that have distinct gene expression profiles, oncogenic mechanisms, and clinical outcomes. Other diagnostic categories such as chronic lymphocytic leukemia (CLL) have a single gene expression signature that distinguishes them from other lymphoid malignancies. Nevertheless, elevated expression of a single gene, ZAP-70, is characteristic of a more aggressive subtype of CLL that may require novel treatment approaches. In mantle cell lymphoma (MCL), a quantitative measurement of gene expression associated with tumor proliferation is a powerful predictor of survival. Ultimately, the molecular diagnosis of these malignancies will identify molecular pathways that can be exploited for therapy. For example, one of the gene expression subgroups of DLBCL, termed activated B-cell like DLBCL, is characterized by constitutive activation of the nuclear factor-kappaB (NF-kappaB) signaling pathway, and interference with this pathway selectively kills these lymphoma cells. The full benefit of gene expression profiling can only be realized if we incorporate this technology into prospective clinical trials.

Chromosomal translocations involved in non-Hodgkin lymphomas

CONTEXT

The discovery that recurrent chromosomal translocations are involved in the pathogenesis of non-Hodgkin lymphomas has greatly improved our understanding of these diseases and revolutionized their diagnosis.

OBJECTIVE

To review the mechanisms by which chromosomal translocations occur and contribute to the pathogenesis of various types of non-Hodgkin lymphomas and to review the utility of molecular genetic methods for the assessment of these translocations.

DATA SOURCES AND STUDY SELECTION

Primary research studies and reviews published in the English language that focus on chromosomal translocation and non-Hodgkin lymphomas.

DATA EXTRACTION AND SYNTHESIS

Chromosomal translocations, which usually result in oncogene activation, occur in many types of B- and T-cell lymphoma, and their detection is helpful for establishing an accurate diagnosis and monitoring disease following therapy. However, the precise mechanisms that explain how translocations occur remain unknown, although for some types of translocations a clear relationship has been established with immunoglobulin gene rearrangement mechanisms. In recent years, a number of genes deregulated by chromosomal translocations have been identified, and the detailed molecular mechanisms by which chromosomal translocations contribute to the pathogenesis of non-Hodgkin lymphoma are beginning to be elucidated.

CONCLUSIONS

Molecular genetic analysis has played a major role in improving our understanding of B- and T-cell non-Hodgkin lymphomas and has allowed more precise definition of lymphoma types. Molecular genetic tests to detect these translocations are important ancillary tools for the diagnosis and classification of malignant lymphomas.

B cell chronic lymphocytic leukemia: lessons learned from studies of the B cell antigen receptor

B cell chronic lymphocytic leukemia (B-CLL) is an accumulative disease of slowly proliferating CD5(+) B lymphocytes that develops in the aging population. Whereas some patients with B-CLL have an indolent course and die after many years from unrelated causes, others progress very rapidly and succumb within a few years from this currently incurable leukemia. Over the past decade studies of the structure and function of the B cell antigen receptor (BCR) used by these leukemic cells have helped redefine the nature of this disease. In this review we summarize and reinterpret several aspects of these BCR-related studies and how they might relate to the disease. In particular, we address the ability of antigens to select out and drive B cell clones from the normal state to overt leukemic cells by binding to BCRs that are relatively unique and characteristic of B-CLL cells. The differential capacity of some B-CLL cases to continue to transduce signals through the BCR during the leukemic phase and the consequences for the in vivo biology of the leukemic clone is also considered. Finally, we discuss current and emerging views of the cellular origin of B-CLL cells and the differentiation pathways down which we believe these cells progress.

More extensive genetic alterations in unmutated than in hypermutated cases of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) is not a uniform disease entity; approximately half of the CLL cases have undergone immunoglobulin V(H) gene hypermutation, whereas the other half display unmutated V(H) genes. We investigated genome changes in 12 hypermutated cases (M-CLL) and 22 unmutated cases (UM-CLL) by use of comparative genomic hybridization, G-banding, and multicolor fluorescence in situ hybridization (m-FISH) after optimal mitogen stimulation and FISH analysis of typical CLL aberrations: 11q deletion, 13q deletion, and trisomy 12. Very high frequencies of aberrations were found in both groups: 82% in UM-CLL and 83% in M-CLL. Deletions of 11q and 13q were equally distributed in M-CLL and UM-CLL. However, larger aberrations detectable by CGH, trisomy 12, and complex aberrations were less frequent in M-CLL than in UM-CLL. These observations led to a hypothesis that unmutated and mutated CLL have different biological Backgrounds, given that large and/or complex chromosomal aberrations and hypermutation of the CLL progenitor cells tend to be mutually exclusive.

Immunobiology of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia increasingly is being recognized as a useful model disease with which to study more general processes involved in the evolution of neoplastic disease. The accessibility of the tumor cells and the capacity to confirm their clonal relatedness allow for evaluation of the processes associated with neoplastic transformation and/or disease progression. Recent studies have provided fascinating insight into the potential pathogenesis and pathophysiology of this disease. In addition, features of leukemia cells have been identified that can distinguish subsets of patients that have different tendencies for disease progression. Gene expression studies have identified a relatively small number of genes that are differentially expressed between these subsets, allowing for focused attention on proteins that might contribute to the noted differences in clinical behavior. Finally, recognition that chronic lymphocytic leukemia cells depend upon specific microenvironmental growth and survival factors identifies novel targets for disease intervention. This article focuses on the reports of the past year that have contributed to these areas of active research on chronic lymphocytic leukemia, the most common adult leukemia in Western societies.