Sharon Barrans

Waldenström macroglobulinemia. Development of diagnostic criteria and identification of prognostic factors.

To establish whether a combination of morphologic and immunophenotypic criteria could be developed to more precisely define Waldenström macroglobulinemia (WM) and prognostic factors, we retrospectively assessed the clinical and laboratory features of 111 cases of WM. Bone marrow infiltration by small lymphocytes was documented in each case; and diffuse, interstitial, nodular, and paratrabecular patterns of infiltration were documented in 58%, 32%, 6%, and 4% of cases, respectively. Ninety percent were characterized by a surface immunoglobulin-positive, CD19+CD20+CD5-CD10-CD23- immunophenotype. The median overall survival from diagnosis was 60 months; univariate analysis revealed the following adverse prognostic factors: older than 60 years, performance status more than 1, platelet count less than 100 x 10(3)/microL (< 100 x 10(9)/L), pancytopenia, and diffuse bone marrow infiltration. Associated median survival was 40, 38, 46, 28, and 59 months, respectively. Multivariate analysis revealed age, performance status, and platelet count as prognostically significant, but stratification of patients according to the International Prognostic Index had limited value. We suggest defining WM by the following criteria: IgM monoclonal gammopathy; bone marrow infiltration by small lymphocytes, plasmacytoid cells, and plasma cells in a diffuse, interstitial, or nodular pattern; and a surface immunoglobulin-positive, CD19+CD20+CD5-CD10-CD23- immunophenotype.

Rearrangement of the BCL6 locus at 3q27 is an independent poor prognostic factor in nodal diffuse large B‐cell lymphoma

Summary. Diffuse large B‐cell lymphomas (DLBCL) are a heterogeneous group of tumours, varying in clinical features, immunophenotype and cytogenetics. The aim of this study was to investigate the prognostic significance of BCL6 gene rearrangement at the 3q27 locus in patients with primary nodal disease, and to examine interrelationships with immunophenotype and International Prognostic Index (IPI). We have developed a fluorescent in situ hybridization (FISH)‐based technique for the retrospective analysis of the effect of BCL6 gene rearrangements on survival, using nuclei extracted from paraffin‐embedded tissue. FISH results were obtained in 111 presentation cases of nodal DLBCL. The IPI was calculated and each case was stained immunocytochemically for BCL6, BCL2 and CD10. 3q27 rearrangements were detected in 25% of cases. BCL2 protein and a germinal centre (GC) phenotype (defined as CD10+, BCL6+) were expressed in 56% and 41% of cases respectively. In multivariate analysis, rearrangement of 3q27 and BCL2 expression and the absence of a GC phenotype were associated with a poor prognosis. These factors can be used in conjunction with the IPI to improve risk stratification in nodal DLBCL.

Distribution of myeloma plasma cells in peripheral blood and bone marrow correlates with CD56 expression

There is a wide variation in the degree of marrow and blood involvement between patients with multiple myeloma. Both of these parameters are known to be highly significant prognostic factors, and the differences between patients may be due to variable expression of adhesion molecules. To test this we used three‐colour flow cytometry to study three adhesion molecules associated with myeloma, namely CD38, CD56 and CD138. The level of expression of these molecules was compared with the distribution of myeloma plasma cells in bone marrow (n=59) and peripheral blood (n=26) in patients at presentation or relapse. The extent of marrow infiltration on the trephine biopsy correlated inversely with CD56 expression (Mann‐Whitney U Test, P=0.022); there was no difference in CD38 or in CD138 expression. CD56 expression also correlated inversely with the number of circulating plasma cells (linear regression, R2=0.4268, slope=−0.58, P=0.0003). Peripheral blood plasma cell numbers correlated weakly with bone marrow plasmacytosis, and inversely with CD38 expression. The level of CD56 expression by neoplastic plasma cells was assessed in 37 patients over a median of 11 months (range 6–25). There was no significant change in expression (Wilcoxon Signed Rank, P=0.6271). We conclude that plasma cell CD56 expression is constant over the course of the disease; unlike CD138 expression, it is significantly linked to the degree of both bone marrow and peripheral blood involvement.

Targeted sequencing identifies patients with preclinical MDS at high risk of disease progression.

The diagnosis of myelodysplastic syndromes (MDS) remains problematic due to the subjective nature of morphologic assessment. The reported high frequency of somatic mutations and increased structural variants by array-based cytogenetics have provided potential objective markers of disease; however, this has been complicated by reports of similar abnormalities in the healthy population. We aimed to identify distinguishing features between those with early MDS and reported healthy individuals by characterizing 69 patients who, following a nondiagnostic marrow, developed progressive dysplasia or acute myeloid leukemia. Targeted sequencing and array-based cytogenetics identified a driver mutation and/or structural variant in 91% (63/69) of prediagnostic samples with the mutational spectrum mirroring that in the MDS population. When compared with the reported healthy population, the mutations detected had significantly greater median variant allele fraction (40% vs 9% to 10%), and occurred more commonly with additional mutations (≥2 mutations, 64% vs 8%). Furthermore, mutational analysis identified a high-risk group of patients with a shorter time to disease progression and poorer overall survival. The mutational features in our cohort are distinct from those seen in the healthy population and, even in the absence of definitive disease, can predict outcome. Early detection may allow consideration of intervention in poor-risk patients.

t(3;14)(p14;q32) results in aberrant expression of FOXP1 in a case of diffuse large B-cell lymphoma

Strong expression of Forkhead box‐P1 (FOXP1), a winged‐helix transcription factor, has been identified as an independent prognostic factor in diffuse large B‐cell lymphoma (DLBCL). However, possible mechanisms of deregulation of this gene, on 3p14.1, have yet to be elucidated. We have identified a breakpoint at the IGA1 gene in the immunoglobulin heavy chain (IGH) locus at 14q32 that was juxtaposed to the FOXP1 gene locus in a gastric DLBCL that showed strong expression of FOXP1. This may be one possible mechanism of deregulating FOXP1 expression by placing it under the control of IGH enhancers.

The detection of t(14;18) in archival lymph nodes: development of a fluorescence in situ hybridization (FISH)-based method and evaluation by comparison with polymerase chain reaction.

Fluorescence in situ hybridization (FISH) has been used to demonstrate the t(14;18) in up to 100% of follicular lymphoma (FL) cases, however, there is little reproducible data using fixed tissue. The aim was therefore to develop a robust FISH method for the demonstration of translocations in archival tissue. The technique was evaluated by comparison with multiplex polymerase chain reaction (PCR), capable of detecting the majority of known breakpoints. Twenty-eight paired frozen and fixed cases of FL and 20 reactive controls were analyzed. The t(14;18) was detected in 23 of 28 cases using PCR on frozen material and 8 of 20 in paraffin. Using FISH, 24 of 26 frozen and 26 of 28 paraffin cases had a demonstrable translocation. All 20 reactive nodes were negative for the t(14;18) by PCR. Using FISH, one of the reactive cases had occasional cells with a translocation FISH pattern, demonstrable in frozen and paraffin samples. This is consistent with the presence of the t(14;18), which is well described in normal individuals. Both PCR and FISH are highly effective for t(14;18) analysis in unfixed tissue. When only paraffin blocks are available, FISH is the method of choice, and a result was achieved in 100% of cases. The method is applicable to the retrospective analysis of a range of translocations.

Whole genome expression profiling based on paraffin embedded tissue can be used to classify diffuse large B‐cell lymphoma and predict clinical outcome

This study tested the validity of whole‐genome expression profiling (GEP) using RNA from formalin‐fixed, paraffin‐embedded (FFPE) tissue to sub‐classify Diffuse Large B‐cell Lymphoma (DLBCL), in a population based cohort of 172 patients. GEP was performed using Illumina Whole Genome cDNA‐mediated Annealing, Selection, extension & Ligation, and tumours were classified into germinal centre (GCB), activated B‐cell (ABC) and Type‐III subtypes. The method was highly reproducible and reliably classified cell lines of known phenotype. GCB and ABC subtypes were each characterized by unique gene expression signatures consistent with previously published data. A significant relationship between subtype and survival was observed, with ABC having the worst clinical outcome and in a multivariate survival model only age and GEP class remained significant. This effect was not seen when tumours were classified by immunohistochemistry. There was a significant association between age and subtype (mean ages ABC – 72·8 years, GC – 68·4 years, Type‐III – 64·5 years). Older patients with ABC subtype were also over‐represented in patients who died soon after diagnosis. The relationship between prognosis and subtype improved when only patients assigned to the three categories with the highest level of confidence were analysed. This study demonstrates that GEP‐based classification of DLBCL can be applied to RNA extracted from routine FFPE samples and has potential for use in stratified medicine trials and clinical practice.

Recurrent mTORC1-activating RRAGC mutations in follicular lymphoma

Follicular lymphoma is an incurable B cell malignancy characterized by the t(14;18) translocation and mutations affecting the epigenome. Although frequent gene mutations in key signaling pathways, including JAK-STAT, NOTCH and NF-κB, have also been defined, the spectrum of these mutations typically overlaps with that in the closely related diffuse large B cell lymphoma (DLBCL). Using a combination of discovery exome and extended targeted sequencing, we identified recurrent somatic mutations in RRAGC uniquely enriched in patients with follicular lymphoma (17%). More than half of the mutations preferentially co-occurred with mutations in ATP6V1B2 and ATP6AP1, which encode components of the vacuolar H+-ATP ATPase (V-ATPase) known to be necessary for amino acid−induced activation of mTORC1. The RagC variants increased raptor binding while rendering mTORC1 signaling resistant to amino acid deprivation. The activating nature of the RRAGC mutations, their existence in the dominant clone and their stability during disease progression support their potential as an excellent candidate for therapeutic targeting.

A Microarray Platform-Independent Classification Tool for Cell of Origin Class Allows Comparative Analysis of Gene Expression in Diffuse Large B-cell Lymphoma

Cell of origin classification of diffuse large B-cell lymphoma (DLBCL) identifies subsets with biological and clinical significance. Despite the established nature of the classification existing studies display variability in classifier implementation, and a comparative analysis across multiple data sets is lacking. Here we describe the validation of a cell of origin classifier for DLBCL, based on balanced voting between 4 machine-learning tools: the DLBCL automatic classifier (DAC). This shows superior survival separation for assigned Activated B-cell (ABC) and Germinal Center B-cell (GCB) DLBCL classes relative to a range of other classifiers. DAC is effective on data derived from multiple microarray platforms and formalin fixed paraffin embedded samples and is parsimonious, using 20 classifier genes. We use DAC to perform a comparative analysis of gene expression in 10 data sets (2030 cases). We generate ranked meta-profiles of genes showing consistent class-association using ≥6 data sets as a cut-off: ABC (414 genes) and GCB (415 genes). The transcription factor ZBTB32 emerges as the most consistent and differentially expressed gene in ABC-DLBCL while other transcription factors such as ARID3A, BATF, and TCF4 are also amongst the 24 genes associated with this class in all datasets. Analysis of enrichment of 12323 gene signatures against meta-profiles and all data sets individually confirms consistent associations with signatures of molecular pathways, chromosomal cytobands, and transcription factor binding sites. We provide DAC as an open access Windows application, and the accompanying meta-analyses as a resource.

In multiple myeloma, only a single stage of neoplastic plasma cell differentiation can be identified by VLA‐5 and CD45 expression

The nature of the proliferating fraction in myeloma is still not known and understanding the characteristics of this fraction is central to the development of effective novel therapies. However, myeloma plasma cells typically show a very low rate of proliferation and this complicates accurate analysis. Although the level of CD45 and/or VLA‐5 has been reported to identify proliferating ‘precursor’ plasma cells, there are discrepancies between these studies. We have therefore used a rigorous sequential gating strategy to simultaneously analyse cycle status and immunophenotype with respect to CD45, VLA‐5 and a range of other integrin molecules. In 11 presentation myeloma patients, the proliferative fraction was distributed evenly between CD45+ and CD45− cells, however, cycling plasma cells were consistently VLA‐5‐. There was close correlation between the expression of VLA‐5 and a range of other integrin molecules (CD11a, CD11c, CD103), as well as the immunoglobulin‐associated molecules CD79a/b (Spearman, n = 10, P < 0·0001). In short‐term culture, cells that were initially VLA‐5‐showed increasing VLA‐5 expression with time. However, simultaneous analysis of the DNA‐binding dye 7‐amino‐actinomycin D demonstrated that this was not as a result of differentiation, as VLA‐5+ plasma cells were all non‐viable. This was confirmed in freshly explanted plasma cells from nine patients. Discrete stages of plasma cell differentiation could not be distinguished by the level of CD45 or VLA‐5 expression. The results indicate that there is a single stage of plasma cell differentiation, with the phenotype CD38+CD138+VLA‐5−. These findings support the hypothesis that neoplastic bone marrow plasma cells represent an independent, self‐replenishing population.