The value of BRCA-1-associated protein 1 expression and cyclin-dependent kinase inhibitor 2A deletion to distinguish peritoneal malignant mesothelioma from peritoneal location of carcinoma in effusion cytology specimens

OBJECTIVE

Diffuse malignant peritoneal mesothelioma (DMPM), represents 30% of all malignant mesothelioma, and is characterised by a difficult diagnosis and different presentations. Immunohistochemistry has improved the diagnostic sensitivity and specificity in the differential diagnosis between metastatic adenocarcinoma and malignant mesothelioma, and loss of BRCA-1-associated protein 1 (BAP1) expression is correlated with BAP1 somatic or constitutional genetic defects. Furthermore, cyclin-dependent kinase inhibitor 2A (CDKN2A) is frequently lost in DMPM. In the present study, we assessed the value of integrating BAP1 in the panel of antibodies used for the diagnosis of DMPM in cytological samples. Since p16 fluorescent in situ hybridisation (FISH) assay could constitute an additional useful adjunct, results of BAP1 immunostaining and p16 FISH assays have been compared.

METHODS

Forty-eight DMPM patients and 71 peritoneal carcinomatosis patients were included. BAP1 immunohistochemical and CDKN2A FISH techniques were performed on tissue specimens of DMPM (n = 48) and peritoneal carcinomatosis (n = 71) then on cell-block of DMPM (n = 16), peritoneal carcinomatosis (n = 25) and peritoneal benign effusion (n = 5).

RESULTS

Loss of BAP1 expression was observed in 56.3% of DMPM while none of the peritoneal carcinoma specimens showed BAP1 loss of expression. CDKN2A loss was observed in 34.9% DMPM and 2.1% peritoneal carcinoma. Although BAP1 immunostaining was successful in 100% of cytological DMPM samples, CDKN2A deletion status could be obtained for 75% of DMPM cases.

CONCLUSION

BAP1 immunostaining represents an objective and reproducible diagnostic biomarker for peritoneal mesothelioma in effusion cytology specimens and should be preferred to CDKN2A FISH analysis on these precious samples.

Splenic diffuse red pulp lymphoma has a distinct pattern of somatic mutations amongst B-cell malignancies

Splenic Diffuse Red Pulp Lymphoma (SDRPL) has been recently introduced as a provisional entity but differential diagnosis with other splenic lymphomas is needed to be clarified since the therapeutic approaches are distinct. Recently described recurrent mutations or CD180 expression appear useful for differential diagnosis. We completed our previous description in a larger cohort including 53 patients selected on the presence of characteristic villous cells in peripheral blood (PB) and a specific immunophenotype. Immunoglobulin heavy variable (IGHV), BRAF, MYD88, and NOTCH2 mutations were determined and CD180 and BRAF expressions were assessed. Most cases (79%) were IGHV mutated with an overrepresentation of IGHV3-23 (19%) and IGHV4-34 (21%). MYD88 L265P and NOTCH2 mutations were observed in one case each, whereas no BRAF V600E mutation or expression was found. All cases demonstrated a high CD180 expression. Those results strengthen the concept that SDRPL does emerge as a new lymphoma entity distinct from the other splenic lymphomas with circulating lymphocytes.

CD1d-restricted peripheral T cell lymphoma in mice and humans

Peripheral T cell lymphomas (PTCLs) are a heterogeneous entity of neoplasms with poor prognosis, lack of effective therapies, and a largely unknown pathophysiology. Identifying the mechanism of lymphomagenesis and cell-of-origin from which PTCLs arise is crucial for the development of efficient treatment strategies. In addition to the well-described thymic lymphomas, we found that p53-deficient mice also developed mature PTCLs that did not originate from conventional T cells but from CD1d-restricted NKT cells. PTCLs showed phenotypic features of activated NKT cells, such as PD-1 up-regulation and loss of NK1.1 expression. Injections of heat-killed Streptococcus pneumonia, known to express glycolipid antigens activating NKT cells, increased the incidence of these PTCLs, whereas Escherichia coli injection did not. Gene expression profile analyses indicated a significant down-regulation of genes in the TCR signaling pathway in PTCL, a common feature of chronically activated T cells. Targeting TCR signaling pathway in lymphoma cells, either with cyclosporine A or anti-CD1d blocking antibody, prolonged mice survival. Importantly, we identified human CD1d-restricted lymphoma cells within Vδ1 TCR-expressing PTCL. These results define a new subtype of PTCL and pave the way for the development of blocking anti-CD1d antibody for therapeutic purposes in humans.

A high rate of telomeric sister chromatid exchange occurs in chronic lymphocytic leukaemia B-cells

Cancer cells protect their telomere ends from erosion through reactivation of telomerase or by using the Alternative Lengthening of Telomere (ALT) mechanism that depends on homologous recombination. Chronic lymphocytic leukaemia (CLL) B cells are characterized by almost no telomerase activity, shelterin deregulation and telomere fusions. To characterize telomeric maintenance mechanisms in B-CLL patients, we measured their telomere length, telomerase expression and the main hallmarks of the ALT activity i.e. C-circle concentration, an extra-chromosomal telomere repeat (ECTR), and the level of telomeric sister chromatid exchange (T-SCE) rate. Patients showed relative homogenous telomere length although almost no TERT transcript and nearly no C-circle were evidenced. Nevertheless, compared with normal B cells, B-CLL cells showed an increase in T-SCE rate that was correlated with a strong down-regulation of the topoisomerase III alpha (TOP3A) expression, involved in the dissolution of Holliday Junctions (HJ), together with an increased expression of SLX1A, SLX4, MUS81 and GEN1, involved in the resolution of HJ. Altogether, our results suggest that the telomere maintenance mechanism of B-CLL cells do not preferentially use telomerase or ALT. Rather, the rupture of the dissolvasome/resolvasome balance may increase telomere shuffling that could homogenize telomere length, slowing telomere erosion in this disease.

Characterization of a de novo Supernumerary Neocentric Ring Chromosome Derived from Chromosome 7

Supernumerary ring chromosomes (SRC) are usually derived from regions adjacent to the centromere. Their identification may be challenging, particularly in case of low mosaicism. Here, we report on a patient who was referred for major in utero growth retardation, severe developmental delay, facial dysmorphism, cleft palate, and hypospadias. The karyotype showed a small SRC in mosaic. The combination of FISH, M-FISH and array-CGH was necessary for a complete characterization of this SRC. M-FISH revealed that the SRC originated from chromosome 7. Array-CGH performed with a 400K oligonucleotide array showed a gain in region 7q22.1q31.1 present in low mosaic. This result was confirmed by FISH using BAC probes specific for chromosome 7. The SRC was a neocentric ring derived from 7q22.1q31.1 and was found in only 8% of the cells. This is the first patient carrying a mosaic neocentric SRC derived from the long arm of chromosome 7. Our study emphasizes the need to combine different techniques and to use adapted bioinformatic tools for low-mosaicism marker identification. It also contributes to the delineation of the partial trisomy 7q phenotype.

Major molecular response achievement in CML Patients can be predicted by BCR-ABL1/ABL1 or BCR-ABL1/GUS ratio at an earlier time point of follow-up than currently recommended

Recent studies demonstrate that early molecular response to tyrosine-kinase inhibitors is strongly predictive of outcome in chronic myeloid leukemia patients and that early response landmarks may identify patients at higher risk for transformation who would benefit from an early switch to second-line therapy. In this study, we evaluated the ability of the control gene GUS to identify relevant thresholds for known therapeutic decision levels (BCR-ABL1/ABL1^IS  = 10% and 0.1%). We then defined the most relevant cut-offs for early molecular response markers (transcript level at 3 months, halving time and log reduction between diagnosis and 3 months of treatment) using GUS or ABL1. We demonstrated that, although both control genes could be used (in an equivalent way) to accurately assess early molecular response, the BCR-ABL1/GUS level at diagnosis is impacted by the higher GUS copy number over-expressed in CML cells, thus negatively impacting its ability to completely replace ABL1 at diagnosis. Furthermore, we pointed out, for the first time, that it would be helpful to monitor BCR-ABL1 levels at an earlier time point than that currently performed, in order to assess response to first-line tyrosine-kinase inhibitors and consider a potential switch of therapy as early as possible. We evaluated this optimal time point as being 19 days after the start of treatment in our cohort.

Higher percentage of CD34 + CD38- cells detected by multiparameter flow cytometry from leukapheresis products predicts unsustained complete remission in acute myeloid leukemia

Relapse in acute myeloid leukemia (AML) after chemotherapy reflects the persistence of resistant leukemia stem cells (LSCs). These cells have been described in the CD34 + CD38- cell fraction. Leukapheresis products were harvested in 123 patients in morphological complete remission and analyzed by multiparameter flow cytometry. The CD34 + CD38- cell population showed a prognostic impact on survival. Median event-free survival (EFS) was 8.2 months (3-year EFS: 29%) for those with a higher percentage of CD34 + CD38- versus 91.9 months (3-year EFS: 62%) for those with a lower percentage for the entire cohort. These differences were confirmed in patients undergoing autologous stem cell transplant, with median EFS of 7.3 months versus 91.1 months (3-year EFS: 31% vs. 70%). Higher proportions of CD34 + CD38- cells were associated with adverse cytogenetics and with earlier relapses. Higher percentages of CD34 + CD38- cells in apheresis products reflect inadequate in vivo purging and reliably distinguish samples enriched in LSCs from those involving mainly normal cells.

Abstract 4055: Non-canonical telomere maintenance mechanism in B-cell chronic lymphocytic leukemia

Unlimited cancer cells proliferation requires mechanisms that counteract telomere attrition. In the majority of cancer cells this is possible through up-regulation of telomerase activity. Alternatively, cancer cells use homologous recombination between telomeres. This second mechanism called ALT (Alternative Lengthening of Telomere) implicates proteins that either elongates telomeres or that either prevents telomere loss (maintenance). Among these proteins a complex composed of the topoisomerase III alpha (hTopoIIIα), BLM, RMI1 and 2 is require to repair stalled replication forks.

Little is known about the involvement of the ALT mechanism in B-cell chronic lymphocytic leukemia (B-CLL), which shows low telomerase activity, shelterin defect and telomeric dysfunctions.

We found that hTopoIIIα gene expression is downregulated in almost all B-CLL patients tested (94%; n=31), with 60% of B-CLL patients presenting a two time decreased compared to control samples. That prompted us to build the first CpG islands map of the hTopoIIIα promoter and to characterize those that are methylated in B-CLL patients. To investigate the methylation impact, we first treated CLL cell lines with 5-Azacytidine, a chemical analogue of cytidine that induces hypomethylation, and demonstrated that this treatment increases hTopoIIIα expression. In line, luciferase experiments revealed that SSSI-induced CpG islands methylation inside the TopoIIIα promoter leads to a transcriptional inhibition. Nevertheless, deletion mutants of the TopoIIIα promoter suggested that CpG islands found to be methylated in B-CLL patients are not implicated in TopoIIIα expression regulation through methylation.

Interestingly, we didn't observe a good correlation between mRNA and protein expressions in all B-CLL patients (n=6). Indeed some patients with a moderate amount of mRNA showed low level of the corresponding protein hTopoIIIα (<50% compared to controls; n=3). Downregulation of hTopoIIIα may increase recombination rate between sister chromatid. Hence, experiments aiming to evaluate sister chromatid exchange and telomeric sister chromatid exchange rate on B-CLL patients samples according to their hTopoIIIα expression level have been performed and the data will be discuss.

Our results suggest that there is no canonical mechanism maintaining telomeres in B-CLL but rather an overall recombination arising during replication, due to hTopoIIIα downregulation, leading to a silenced genetic instability in the early step of the disease.

Citation Format: Sandrine Medves, Morgan Auchter, Laetitia Chambeau, Sophie Gazzo, Aurélie Verney, Etienne Moussay, Wim Ammerlaan, Hamid Morjani, Vincent Géli, Valérie Palissot, Gilles Salles, Guy Berchem, Thomas Wenner. Non-canonical telomere maintenance mechanism in B-cell chronic lymphocytic leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4055. doi:10.1158/1538-7445.AM2013-4055

High DNA methyltransferase DNMT3B levels: a poor prognostic marker in acute myeloid leukemia

It has been recently shown that DNA methyl transferase overexpression is correlated with unfavourable prognosis in human malignancies while methylation deregulation remains a hallmark that defines acute myeloid leukemia (AML). The oncogenic transcription factor EVI1 is involved in methylation deregulation and its overexpression plays a major role for predicting an adverse outcome. Moreover, the identification of DNMT3A mutations in AML patients has recently been described as a poor prognostic indicator. In order to clarify relationship between these key actors in methylation mechanisms and their potential impact on patient outcomes, we analysed 195 de novo AML patients for the expression of DNMT3A, 3B (and its non-catalytic variant 3B(NC)) and their correlations with the outcome and the expression of other common prognostic genetic biomarkers (EVI1, NPM1, FLT3ITD/TKD and MLL) in adult AML. The overexpression of DNMT3B/3B(NC) is (i) significantly correlated with a shorter overall survival, and (ii) inversely significantly correlated with event-free survival and DNMT3A expression level. Moreover, multivariate analysis showed that a high expression level of DNMT3B/3B(NC) is statistically a significant independent poor prognostic indicator. This study represents the first report showing that the overexpression of DNMT3B/3B(NC) is an independent predictor of poor survival in AML. Its quantification should be implemented to the genetic profile used to stratify patients for therapeutical strategies and should be useful to identify patients who may benefit from therapy based on demethylating agents.

In non-follicular lymphoproliferative disorders, IGH/BCL2-fusion is not restricted to chronic lymphocytic leukaemia

The translocation t(14;18) and its t(2;18) and t(18,22) variants, which involve the BCL2 genetic hallmark for follicular lymphoma (FL), have been reported in several cases of chronic B-cell lymphoproliferative disease (CLPD) and frequently in chronic lymphocytic leukaemia (CLL). We describe here the clinical, morphological, immunological, cytogenetic and molecular findings from 37 cases of t(14;18)-positive CLPD, identified from our series of non-FL B-cell neoplasms (n=993) that were routinely analysed in peripheral blood by conventional cytogenetics analyses. The FL diagnosis was excluded by morphology and immunology (the samples were CD10 negative in all cases). The BCL2 translocations were observed in 22 CLL cases, including 7 monoclonal B-cell lymphocytosis (MBL) cases re-classified according to the new International Workshop on CLL criteria, six small lymphocytic lymphoma (SLL) cases, 1 splenic marginal zone lymphoma (SMZL) case and eight cases of unclassifiable CLPD with overlapping CLL/MZL features. In the CLL cases, the IGH/BCL2 fusion was remarkably associated with trisomy 12 (13/22) and mutated IGHV status (20/21) and did not affect the outcome. Moreover, most of these CLLs harboured a low mutation load of BCL6 gene and unmutated FAS (CD95) loci, which points to a post-germinal-centre cellular origin.

Detection of BRAF V600E mutation in thyroid fine-needle aspiration specimens by High Resolution Melting (HRM) analysis

AIM

The aim of our study was to test the feasibility of High Resolution Melting (HRM) analysis for detection of BRAF V600E mutation in various types of fine-needle aspiration (FNA) specimens from patients with papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

We analyzed fresh thyroid aspirates and smears from eight cases of PTC: three classic PTCs (CPTC), three follicular variant of PTCs (FVPTC), one tall cell, and one oncocytic variant of PTC. DNA extraction was performed using a MasterPure purification kit. The isolated DNA quantity was assessed using a NanoDrop spectrophotometer and the DNA quality was tested by PCR amplification of β-globin gene and by native DNA electrophoresis. HRM was performed on a LightCycler 480 (Roche). We amplified the 15th exon of BRAF gene, using selected primers to flank the BRAF V600E mutation point.

RESULTS

For all types of cytological specimens, the quantity of isolated DNA was adequate and allowed amplification. Similarly, the DNA quality control did not show signs of DNA degradation and the DNA was amplifiable for β-globin gene. Four cases revealed the BRAF V600E mutation: two CPTCs, one oncocytic PTC, one tall cell PTC. None of the three cases of FVPTC had this mutation.

CONCLUSIONS

HRM analysis represents a feasible and reproducible molecular technique, offering new perspectives for detecting BRAF mutation in various FNA specimens. In our study, BRAF V600E mutation revealed a strong association with specific histological variants of PTC: highly specific for CPTC, tall cell or oncocytic PTC, but negative in all cases of FVPTC.

Identification of a novel e8/a4 BCR/ABL fusion transcript in a case of a transformed Sézary syndrome

This report deals with a case of Sézary syndrome, a rare peripheral T-cell lymphoproliferative disorder, in which cytogenetic analysis performed during the disease transformation revealed the presence of a t(9;22) (q34;q11.2) translocation. Molecular analyses identified a new transcript, an e8a4 BCR-ABL fusion mRNA which could be responsible for the disease transformation.

Detailed characterization of 7q deletions by multicolor banding (mBAND) in marginal zone cell lymphoma

High-resolution multicolor banding (mBAND) analysis was applied to precisely fine-map the genomic extent of 7q deletions in a series of 26 marginal zone lymphoma patients displaying the abnormality on conventional karyotypes. Using this approach, the breakpoints and the extent of deletions revealed by conventional banding techniques had to be re-defined in 70% of cases. Although no common minimal region of deletion was delineated, mBAND demonstrated the involvement of the 7q32 region in more than 90% of cases. In addition, unsuspected translocations and intrachromosomal changes could be identified in four cases. Taken together, these data demonstrate that mBAND represents an alternative cytogenetic tool in the comprehensive analysis of chromosome aberrations in hematologic malignancies, allowing rapid screening and precise delineation of structural rearrangements of a defined chromosome. This also confirms the localization in the vicinity of band 7q32 of putative candidate gene(s) involved in the pathogenic development of the disease.

The translocations t(6;18;11)(q24;q21;q21) and t(11;14;18)(q21;q32;q21) lead to a fusion of the API2 and MALT1 genes and occur in MALT lymphomas

So far, only one variant translocation of the t(11;18)(q21;q21), the t(11;12;18) (q21;q13;q21), has been reported. We herein describe two new variant translocations, the t(6;18;11)(q24;q21;q21) and the t(11;14;18)(q21;q32;q21), occurring in mucosa-associated lymphoid tissue (MALT) lymphomas. In both cases, fluorescence in situ hybridization (FISH) and reverse transcriptase polymerase chain reaction (RT-PCR) revealed the presence of an 5'API2-3'MALT1 fusion product, encoded on the derivative chromosome 11. Exon 7 of API2 was fused with exon 5 of MALT1 in the t(11;14;18) and with exon 8 of MALT1 in the t(6;18;11). FISH revealed the involvement of the immunoglobulin locus in the t(11;14;18). Rapid amplification of cDNA ends (RACE)-PCR to detect the involved partner gene on 6q showed exclusively wild-type API2 and MALT1 sequences.

Cytogenetic and Molecular Analysis of 12 Cases of Primary Cutaneous Marginal Zone Lymphomas

Primary low-grade B-cell lymphomas of the skin are separated into marginal zone and follicle center lymphomas according to the recent World Health Organization-European Organization for Research and Treatment of Cancer classification, with distinct histologic and immunohistochemical profiles. Some cases remain difficult to distinguish. The degree of relationship with their extracutaneous counterparts is currently being investigated on clinical, histologic and molecular grounds. Cytogenetic analysis using fluorescence in situ hybridization was performed on 12 frozen samples of infiltrated skin that had been classified as marginal zone lymphoma (MZL). Chromosomal changes known to be recurrently observed in systemic MZL of the mucosa-associated lymphoid tissue type, and in follicular center lymphoma were analyzed. These included trisomy for chromosomes 3, 7, 12, and 18 as well as t(14;18) IGH/BCL2, t(14;18) IGH/MLT1, and t(11;18) API2/MLT1 translocations. Complementary molecular search of IGH/BCL2 rearrangement using a polymerase chain reaction technique and of API2/MLT1 mRNA expression by reverse transcriptase-polymerase chain reaction were performed. Two cases showed evidence of trisomy 3 at levels varying from 14% to 20% of the analyzed cells. No other chromosomal abnormalities were found with those techniques in the remaining cases. These results demonstrate that known recurrent chromosomal abnormalities rarely occur in primary cutaneous MZLs and suggest the possibility of a variety of initial oncogenic events leading to a common downstream pathway. These data also underline that fluorescence in situ analysis on routine skin punch biopsies represents a reliable tool for the detection of chromosomal changes, but requires consistent dermal infiltration.

A clinicopathological study of nodal marginal zone B-cell lymphoma. A report on 21 cases

AIMS

To report the clinicopathological findings of 21 cases of primary nodal marginal zone B-cell lymphoma (NMZL). NMZL is a recently characterized lymphoma and few series have been published.

METHODS AND RESULTS

The clinical data were characteristic of a disseminated disease at presentation: presence of peripheral and abdominal lymph nodes, bone marrow involvement (62%), disease stage III and IV (76%), elevated lactate dehydrogenase (LDH) (48%). Other features included peripheral blood involvement (23%), anaemia (24%), thrombocytopenia (10%) and presence of serum M component (33%), while the previously reported association with hepatitis C virus and cryoglobulinaemia was not found. Relapses were frequent but the majority of patients receiving chemotherapy had a good initial response. Morphological features were heterogeneous and there were some differences compared with other marginal zone B-cell lymphomas (MZL). Pure monocytoid B-cell lymphomas were rare (10%) but a minor component of monocytoid B cell was observed more frequently (23%). Plasmacytoid or plasmacytic differentiation was a very common feature (61%). Large cells and a high mitotic count were also frequent (57%).

CONCLUSION

NMZL can be distinguished from splenic MZL and extranodal MZL by its aggressive morphology and disseminated disease at presentation.

Atypical cytogenetic presentation of t(11;14) in mantle cell lymphoma

Eighteen cases of mantle cell lymphomas (MCL) with an atypical t(11;14) were studied using fluorescence in situ hybridization experiments (FISH). The atypical presentation was confirmed and unsuspected duplicated cases were identified in six patients. These data underline that FISH analysis must be be systematically performed in cases with an aberrant presentation to prevent a misdiagnosis.

An unusual case of indolent B-cell lymphoma with distinct chronic lymphocytic leukemia and marginal zone differentiation according to the site of involvement

The immunological profile of lymphoproliferative disorders is usually conserved whatever the involved site, thus allowing a reliable diagnosis from peripheral blood analysis, especially in small lymphocytic lymphoma/chronic lymphocytic lymphoma (SLL/CLL). Here we present a case wherein the cytology and immunophenotype of blood specimen and bone marrow argue in favor of SLL/CLL with a typical Matutes score (5/5), whereas the cyto-histology and immunophenotype of spleen specimen led to the diagnosis of splenic marginal zone B-cell lymphoma (SMZL). Moreover genomic analysis showed that the splenic cells displayed a SMZL signature. Whereas these data suggested the presence of 2 B-cell clones, the study of the mutational status of IgVH gene in blood and spleen demonstrated the presence of a single clone, which likely developed simultaneously along two distinct ways of differentiation according to the anatomic site suggesting here the predominant role of a micro-environmental factor in cell differentiation. Although rare, this kind of event must be kept in mind as a cause of discrepancies between diagnoses from different sites.

Cytogenetic analysis delineates a spectrum of chromosomal changes that can distinguish non-MALT marginal zone B-cell lymphomas among mature B-cell entities: a description of 103 cases

The purpose of this study was to document the frequency and distribution of karyotypic changes present at diagnosis in 103 non-MALT marginal zone cell lymphoma (MZL) patients. This cytogenetic analysis of a large cohort extends previous observations and allows the identification of new cytogenetic features. Abnormalities identified in more than 15% of patients included +3/+3q (37%), 7q deletions (31%), +18/+18q (28%), 6q deletions (19%), +12/+12q (15%) and 8p deletions (15%). Trisomy 3/3q, 7q deletions, +18 and +12 were seen in different combinations in more than 30% of patients in comparison to 2% in lymphocytic lymphomas/chronic lymphocytic leukemias, 1% in mantle cell lymphomas and 7% in follicular lymphomas. The marked propensity of these abnormalities to be recurrently associated with the same tumoral clone of individual karyotypes allowed the delineation of a cytogenetic profile that may help to distinguish non-MALT MZL among other mature B-cell neoplasms. If +3/3q, +12/+12q, and 6q, 7q and 8p deletions were significantly associated with clinical prognostic factors previously reported to influence survival and time to progression, patients displaying these abnormalities did not experience a significantly shorter time to progression.

Analysis of VH genes in marginal zone lymphoma reveals marked heterogeneity between splenic and nodal tumors and suggests the existence of clonal selection

BACKGROUND AND OBJECTIVES

To clarify the relationship between splenic (SMZL) and nodal marginal zone (NMZL) lymphomas, we analyzed immunoglobulin variable heavy chain (VH) gene usage and mutation patterns in these tumors.

DESIGN AND METHODS

VH genes were cloned and sequenced from 49 lymphoma samples (35 SMZL and 14 NMZL).

RESULTS

A biased usage of VH gene was found with overrepresentation of VH1 in SMZL cases (13/35) and VH4 in NMZL cases (7/14). Evidence for antigen driven mutations was identified in 8 SMZL and 4 NMZL cases. Three cases out of 18 with clones analyzed from spleen and peripheral blood demonstrated intra-clonal diversity, with evidence of clonal selection in one case, indicating the possibility of antigen-driven clonal expansion. Eleven SMZL cases (31%) but only 2 NMZL (14%) cases were unmutated. No differences in clinical outcome and overall survival were found between the unmutated and mutated cases.

INTERPRETATION AND CONCLUSIONS

The pattern of somatic mutation and the VH gene segment usage appear to differ between SMZL and NMZL, suggesting that these are distinct pathological entities. Moreover, a biased usage of certain sequences suggests that tumor cells in SMZL may be subjected to antigen selection.

Clinicopathologic Features of Waldenström's Macroglobulinemia and Marginal Zone Lymphoma: Are They Distinct or the Same Entity?

Waldenstrom's macroglobulinemia (WM) is considered in the World Health Organization classification as a clinical syndrome associated with monoclonal immunoglobulin (Ig) M secretion, mainly observed in patients with lymphoplasmacytic lymphoma (LPL) and occasionally with other small B-cell lymphomas. Some authors consider it a rare distinct lymphoproliferative disorder with primary bone marrow infiltration and IgM monoclonal gammopathy. As LPL shares important morphologic and immunophenotypic overlaps with marginal zone B-cell lymphomas (MZLs) in cases showing plasmacytic maturation, it remains unclear if they constitute unique or distinct entities. Both diseases are composed of lymphocytes, lymphoplasmacytoid cells, and tumoral plasma cells with a surface (s) IgM-positive sIgD+/ cytoplasmic IgMpositive CD19+ CD20+ CD27+/ CD5 CD10 CD23 phenotype, without a specific marker. Extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, nodal MZL (NMZL), and splenic MZL (SMZL) are distinct entities displaying common morphologic, immunophenotypic, and genetic characteristics. MALT lymphoma is clearly distinct from LPL, although bone marrow infiltration and IgM paraprotein are not rare. Splenic MZL and NMZL are incompletely characterized, but a plasmacytoid/plasmacytic differentiation, autoimmune manifestations, and monoclonal component are frequent in both diseases. Bone marrow involvement is constant in SMZL and present in 60% of NMZLs. Molecular IgVH gene analysis has confirmed this heterogeneity, particularly within SMZL, with mutated and unmutated cases. Further studies are needed to clarify the pathogenesis of these MZLs and their relationship with LPL.

Small lymphocytic lymphoma, marginal zone B-cell lymphoma, and mantle cell lymphoma exhibit distinct gene-expression profiles allowing molecular diagnosis

Non-germinal center small B-cell lymphomas represent a heterogeneous group of non-Hodgkin lymphomas, the most frequent histologic subtypes being small lymphocytic lymphoma (SLL), splenic marginal zone B-cell lymphoma (MZL), and mantle cell lymphoma (MCL). In order to identify genomic signatures specific for each disease, we analyzed 128 primary tumors using high-density microarrays. Several clusters of genes significantly discriminated the 3 histologic subtypes. Genes associated with cell adhesion, angiogenesis, and inhibition of apoptosis were up-regulated in SLL. Genes associated with intracellular signaling via the AKT1 pathway were up-regulated in splenic MZL. Genes associated with cell cycle control and multidrug resistance were up-regulated in MCL. Using 44 genes selected within the gene clusters discriminant for the 3 lymphoma subtypes, we generated a class prediction score that allowed us to classify the 3 entities in 96% of the cases, including borderline cases. Whereas specific transcriptional profiles easily distinguished all MZL samples, SLL samples, and most of the MCL samples into separate groups, few MCL cases exhibited MZL-type transcriptional profiles. This study demonstrates that SLL, splenic MZL, and MCL possess specific transcriptional profiles that may be relevant to the pathogenesis and the diagnosis of these histologic subtypes.

Cytogenetic and molecular delineation of a region of chromosome 3q commonly gained in marginal zone B-cell lymphoma

BACKGROUND AND OBJECTIVES

Whole or partial trisomy 3 represents the most recurrent chromosomal abnormality occurring in marginal zone B-cell lymphoma (MZBCL), a distinct subtype of B-cell non-Hodgkin's lymphoma (NHL). By conventional cytogenetic analysis, unbalanced translocations involving chromosome 3 and leading to a partial trisomy 3q were identified in a series of 14 MZBCL patients. Fluorescent in situ hybridization (FISH) experiments were then performed to characterize the breakpoints further and to delineate the extent of the 3q gained region more accurately.

DESIGN AND METHODS

We studied 14 cases of MZBCL combining cytogenetics and FISH techniques using specific probes for the long arm of chromosome 3, including the chromosome 3 a satellite probe, a representative panel of yeast artificial chromosome (YAC) clones mapping the chromosomal 3q region (3q11.2 to 3q23) and the chromosome 3 subtelomeric (3q29) probe.

RESULTS

In the 14 cases, additional chromosome 3q material was found to be involved in different unbalanced translocations with chromosomes 1, 6, 7, 8, 11, 13, 14, 15, 17, 19 and 21, leading to a derivative chromosome. None of the chromosomal abnormality juxtaposed the 3q regions with the heavy and/or light k and l immunoglobulin gene loci. Eight different breakpoints distributed between the 3q11.2 and the 3q13.32 regions were identified and a common 3q13.32 3q29 overrepresented region was delineated.

INTERPRETATION AND CONCLUSIONS

These results suggest that this critical region may be of importance in the pathogenesis of MZBCL and support the hypothesis that a gene dosage effect rather than a specific gene disruption may be involved in the development of this disease.

Distinct chromosome 3 abnormalities in persistent polyclonal B-cell lymphocytosis

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare entity of unknown etiology characterized by a polyclonal expansion of B-lymphocytes with typical bilobulated forms, elevated serum IgM, and an additional isochromosome for the long arm of chromosome 3 as the sole change. In the present study, we investigated four cases of PPBL by means of conventional cytogenetic analysis and FISH. In all patients, the polyclonality of the lymphoproliferation was demonstrated by immunophenotypic studies, and PCR analysis failed to demonstrate clonal IGH rearrangements in three evaluated cases. In two patients, in addition to +i(3)(q10), banding techniques identified unrelated clones with trisomy 3. FISH studies using a chromosome 3 long arm-specific probe provided evidence that all cases had both +i(3)(q10) and +3. To determine more precisely the distribution of the chromosomal abnormalities within the peripheral lymphocyte population, we investigated two of these cases using a technique of simultaneous fluorescence immunophenotyping and interphase cytogenetics (FICTION). We demonstrated that both abnormalities were randomly distributed among the B-lymphocytes, independently of the kappa or lambda light chain isotype and the nuclear aspect. These data lead us to conclude that trisomy 3 represents, in addition to +i(3)(q10), another recurrent cytogenetic change in PPBL, suggesting that this lymphoproliferative disorder is associated with an increased frequency of chromosome 3 instability.

Common resistance mechanisms to deoxynucleoside analogues in variants of the human erythroleukaemic line K562

Resistant variants of the human leukaemic line K562 were developed using selection with the deoxynucleoside analogues cytosine arabinoside, 2-chlorodeoxyadenosine, fludarabine and gemcitabine. The resistant lines displayed a high degree of cross resistance to all deoxynucleoside analogues, with little or no cross resistance to other agents. There was a profound accumulation defect of all nucleoside analogues in the resistant variants but no significant defect in nucleoside transport in any of the variants. 5' nucleotidase activity was strongly increased and deoxycytidine kinase activity was moderately reduced in all of the resistant variants, resulting in reduced accumulation of triphosphate analogues. In addition a deletion in one of the alleles of the deoxycytidine kinase was detected in the fludarabine-resistant line. Ribonucleotide reductase activity was found to be strongly increased in the gemcitabine-selected line and purine nucleoside phosphorylase was increased in the 2-chlorodeoxyadenosine-selected line. Free nucleotide pools were increased in the 2-chlorodeoxyadenosine-selected line. There was no expression of the mdr1 gene by the resistant lines. Karyotypic analysis and FISH experiments using a 6q21 specific probe showed alterations in the 6(q16-q22) region which contains the 5'-nucleotidase gene. Early events in the activation and degradation of deoxynucleoside analogues appear to constitute common mechanisms of resistance to these compounds.

Translocations involving the short arm of chromosome 17 in chronic B-lymphoid disorders: frequent occurrence of dicentric rearrangements and possible association with adverse outcome

Unbalanced translocations involving chromosome arm 17p, where the TP53 tumor suppressor gene localizes, are rarely described in chronic lymphocytic leukemia and small lymphocytic lymphoma (CLL/SLL), but recent use of molecular cytogenetic techniques have indicated a significant incidence of TP53 deletions, suggesting the involvement of chromosome 17p in these disorders. By conventional karyotype, we have identified unbalanced translocations involving 17p in 14 out of 123 (11%) CLL/SLL patients with clonal abnormalities. Cases were characterized by resistance to chemotherapy and a poor clinical outcome. The karyotypes presented a high incidence of complex rearrangements and 17p translocations were characterized by various partners. In 10 cases a centric fusion was assessed by fluorescent in situ hybridization (FISH) experiments using specific centromeric probes. The incidence of dicentric translocations in these series is therefore significantly higher than usually described, arising in up to 71% (10 out of 14 cases). In all cases, translocations led to a monosomy 17p and to a TP53 monoallelic deletion. The adverse clinical outcome confirms that structural abnormalities involving chromosome 17p are associated with disease progression in patients with chronic lymphoproliferative disorders.

Distribution of the cytogenetic abnormality +i(3)(q10) in persistent polyclonal B-cell lymphocytosis: a FICTION study in three cases

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare entity characterized by a moderate but sustained lymphocytosis where some binucleated or bilobulated circulating forms constitute, even if they are not entirely specific, the cytological hallmark of the disease. An additional chromosome long arm i(3)(q10) has recently been reported as a recurrent cytogenetic aberration, contrasting with a usual polyclonal immunoglobulin expression. To determine more precisely the distribution of the chromosomal abnormality within the peripheral lymphocyte population and study the relationship between the +i(3)(q10) and the bilobulated character, we investigated three new cases of PPBL displaying the cytogenetic abnormality on the karyotype, using a technique of simultaneous fluorescence immunophenotyping and interphase cytogenetics (FICTION). We demonstrated that the +i(3)(q10) was restricted to the B lymphocytes, independently of the kappa or lambda light chain isotype and was present in both bilobulated and non-bilobulated cells. Therefore it is likely that the cytogenetic abnormality occurs at an early stage of lymphocyte differentiation in a precursor cell already committed to the B-cell lineage, before any rearrangement of immunoglobulin genes has taken place.

Unbalanced X;autosome translocation (X;18)(q13;p11) in a case of aggressive natural killer non-Hodgkin lymphoma

Recent evidence has shown that rare cases of aggressive non-Hodgkin lymphomas (NHL) derive from cells belonging to the natural killer (NK) lymphocyte lineage and a new clinico pathologic entity has been proposed. Though well documented in B- and T-cell NHL, chromosome abnormalities are rare findings in NK-NHL and to date, no recurrent cytogenetic abnormality has been described. The present study reports the clinical data, cytogenetic and fluorescence in situ hybridization (FISH) analysis of a new case of typical NK-NHL characterized by a primary unbalanced translocation (X;18) (q13;p11). Recent data of X;autosome translocation in malignant lymphomas have proposed Xp22 and Xq28 as the location of NHL-related oncogenes. According to other published reports on the involvement of the Xq13 region in NHL and particularly in aggressive forms, we hypothesize the existence of additional putative lymphoma-associated oncogenes at the band Xq13.

dic(4;17)(p11;p11): a new recurrent chromosomal abnormality in chronic B-lymphoid disorders

We describe a new nonrandom rearrangement, dic(4;17)(p11;p11), which was identified in three patients with small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). All three cases had in common atypical morphological features with a significant component of prolymphocytes, an unusual clinical outcome, and were refractory to chemotherapy. To further define the cytogenetic breakpoints, we investigated the cases by whole chromosome painting and fluorescence in situ hybridization (FISH) with centromeric probes. FISH analysis detected the same cytogenetic rearrangement in all patients, suggesting that the dic(4;17)(p11;p11) is a recurrent translocation in SLL/CLL. Moreover, FISH analysis showed a monoallelic deletion of the TP53 gene in all cases, suggesting a correlation with the aggressive course of the disease and the clinical outcome observed in these patients.