Publications by authors named "Merrill Boyle"

28 Publications

  • Page 1 of 1

The impact of MYC and BCL2 structural variants in tumors of DLBCL morphology and mechanisms of false-negative MYC IHC.

Blood 2021 Apr;137(16):2196-2208

Centre for Lymphoid Cancer, BC Cancer, Vancouver, BC, Canada.

When the World Health Organization defined high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements (HGBL-DH/TH) as a clinical category, rearrangements were the only structural variant (SV) incorporated. An "atypical double-hit" category has been proposed, encompassing tumors with concurrent MYC and BCL2 SVs other than cooccurring translocations (ie, copy number variations [CNVs]). Although the identification of a gene expression signature (DHITsig) shared among tumors harboring MYC and BCL2 rearrangements (HGBL-DH/TH-BCL2) has confirmed a common underlying biology, the biological implication of MYC and BCL2 CNVs requires further elucidation. We performed a comprehensive analysis of MYC and BCL2 SVs, as determined by fluorescent in situ hybridization (FISH), in a cohort of 802 de novo tumors with diffuse large B-cell lymphoma morphology. Although BCL2 CNVs were associated with increased expression, MYC CNVs were not. Furthermore, MYC and BCL2 CNVs, in the context of atypical double-hit, did not confer a similar gene expression profile as HGBL-DH/TH-BCL2. Finally, although MYC immunohistochemistry (IHC) has been proposed as a screening tool for FISH testing, 2 mechanisms were observed that uncoupled MYC rearrangement from IHC positivity: (1) low MYC messenger RNA expression; and (2) false-negative IHC staining mediated by a single-nucleotide polymorphism resulting in an asparagine-to-serine substitution at the 11th amino acid residue of MYC (MYC-N11S). Taken together, these results support the current exclusion of MYC and BCL2 CNVs from HGBL-DH/TH and highlight the ability of a molecular-based classification system to identify tumors with shared biology that FISH and IHC fail to fully capture.
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http://dx.doi.org/10.1182/blood.2020007193DOI Listing
April 2021

Gene expression profiling of gray zone lymphoma.

Blood Adv 2020 06;4(11):2523-2535

Centre for Lymphoid Cancer, British Columbia Cancer, Vancouver, BC, Canada.

Gray zone lymphoma (GZL), a B-cell lymphoma with features intermediate between large B-cell lymphoma (LBCL) and classic Hodgkin lymphoma (cHL), is a rare and poorly defined entity. Alongside GZL, a subset of Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) has been described with polymorphic/GZL-like morphology (polymorphic-EBV-L). To fill the important gap in our understanding of the pathogenic process underlying these entities, we performed a gene expression study of a large international cohort of GZL and polymorphic-EBV-L, combined with cHL and primary mediastinal large B-cell lymphoma (PMBCL) cases. In an unsupervised principal component analysis, GZL cases presented with intermediate scores in a spectrum between cHL and PMBCL, whereas polymorphic-EBV-L clustered distinctly. The main biological pathways underlying the GZL spectrum were related to cell cycle, reflecting tumor cell content, and extracellular matrix signatures related to the cellular tumor microenvironment. Differential expression analysis and phenotypic characterization of the tumor microenvironment highlighted the predominance of regulatory macrophages in GZL compared with cHL and PMBCL. Two distinct subtypes of GZL were distinguishable that were phenotypically reminiscent of PMBCL and DLBCL, and we observed an association of PMBCL-type GZL with clinical presentation in the "thymic" anatomic niche. In summary, gene expression profiling (GEP) enabled us to add precision to the GZL spectrum, describe the biological distinction compared with polymorphic-EBV-L, and distinguish cases with and without thymic involvement as 2 subgroups of GZL, namely PMBCL-like and DLBCL-like GZL.
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http://dx.doi.org/10.1182/bloodadvances.2020001923DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284085PMC
June 2020

Coding and noncoding drivers of mantle cell lymphoma identified through exome and genome sequencing.

Blood 2020 07;136(5):572-584

Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.

Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma (NHL) that is incurable with standard therapies. The genetic drivers of this cancer have not been firmly established, and the features that contribute to differences in clinical course remain limited. To extend our understanding of the biological pathways involved in this malignancy, we performed a large-scale genomic analysis of MCL using data from 51 exomes and 34 genomes alongside previously published exome cohorts. To confirm our findings, we resequenced the genes identified in the exome cohort in 191 MCL tumors, each having clinical follow-up data. We confirmed the prognostic association of TP53 and NOTCH1 mutations. Our sequencing revealed novel recurrent noncoding mutations surrounding a single exon of the HNRNPH1gene. In RNA-seq data from 103 of these cases, MCL tumors with these mutations had a distinct imbalance of HNRNPH1 isoforms. This altered splicing of HNRNPH1 was associated with inferior outcomes in MCL and showed a significant increase in protein expression by immunohistochemistry. We describe a functional role for these recurrent noncoding mutations in disrupting an autoregulatory feedback mechanism, thereby deregulating HNRNPH1 protein expression. Taken together, these data strongly imply a role for aberrant regulation of messenger RNA processing in MCL pathobiology.
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http://dx.doi.org/10.1182/blood.2019002385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7440974PMC
July 2020

TMEM30A loss-of-function mutations drive lymphomagenesis and confer therapeutically exploitable vulnerability in B-cell lymphoma.

Nat Med 2020 04 24;26(4):577-588. Epub 2020 Feb 24.

Centre for Lymphoid Cancer, British Columbia Cancer, Vancouver, British Columbia, Canada.

Transmembrane protein 30A (TMEM30A) maintains the asymmetric distribution of phosphatidylserine, an integral component of the cell membrane and 'eat-me' signal recognized by macrophages. Integrative genomic and transcriptomic analysis of diffuse large B-cell lymphoma (DLBCL) from the British Columbia population-based registry uncovered recurrent biallelic TMEM30A loss-of-function mutations, which were associated with a favorable outcome and uniquely observed in DLBCL. Using TMEM30A-knockout systems, increased accumulation of chemotherapy drugs was observed in TMEM30A-knockout cell lines and TMEM30A-mutated primary cells, explaining the improved treatment outcome. Furthermore, we found increased tumor-associated macrophages and an enhanced effect of anti-CD47 blockade limiting tumor growth in TMEM30A-knockout models. By contrast, we show that TMEM30A loss-of-function increases B-cell signaling following antigen stimulation-a mechanism conferring selective advantage during B-cell lymphoma development. Our data highlight a multifaceted role for TMEM30A in B-cell lymphomagenesis, and characterize intrinsic and extrinsic vulnerabilities of cancer cells that can be therapeutically exploited.
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http://dx.doi.org/10.1038/s41591-020-0757-zDOI Listing
April 2020

The double-hit signature identifies double-hit diffuse large B-cell lymphoma with genetic events cryptic to FISH.

Blood 2019 10;134(18):1528-1532

Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.

High-grade B-cell lymphomas with MYC and BCL2 and/or BCL6 rearrangements (HGBL-DH/THs) include a group of diffuse large B-cell lymphomas (DLBCLs) with inferior outcomes after standard chemoimmunotherapy. We recently described a gene expression signature that identifies 27% of germinal center B-cell DLBCLs (GCB-DLBCLs) as having a double-hit-like expression pattern (DHITsig) and inferior outcomes; however, only half of these cases have both MYC and BCL2 translocations identifiable using standard breakapart fluorescence in situ hybridization (FISH). Here, 20 DHITsig+ GCB-DLBCLs apparently lacking MYC and/or BCL2 rearrangements underwent whole-genome sequencing. This revealed 6 tumors with MYC or BCL2 rearrangements that were cryptic to breakapart FISH. Copy-number analysis identified 3 tumors with MYC and 6 tumors with MIR17HG gains or amplifications, both of which may contribute to dysregulation of MYC and its downstream pathways. Focal deletions of the PVT1 promoter were observed exclusively among DHITsig+ tumors lacking MYC translocations; this may also contribute to MYC overexpression. These results highlight that FISH fails to identify all HGBL-DH/THs, while revealing a range of other genetic mechanisms potentially underlying MYC dysregulation in DHITsig+ DLBCL, suggesting that gene expression profiling is more sensitive for identifying the biology underlying poor outcomes in GCB-DLBCL.
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http://dx.doi.org/10.1182/blood.2019002600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839951PMC
October 2019

Molecular and Genetic Characterization of MHC Deficiency Identifies EZH2 as Therapeutic Target for Enhancing Immune Recognition.

Cancer Discov 2019 04 31;9(4):546-563. Epub 2019 Jan 31.

Centre for Lymphoid Cancer, British Columbia Cancer, Vancouver, British Columbia, Canada.

We performed a genomic, transcriptomic, and immunophenotypic study of 347 patients with diffuse large B-cell lymphoma (DLBCL) to uncover the molecular basis underlying acquired deficiency of MHC expression. Low MHC-II expression defines tumors originating from the centroblast-rich dark zone of the germinal center (GC) that was associated with inferior prognosis. MHC-II-deficient tumors were characterized by somatically acquired gene mutations reducing MHC-II expression and a lower amount of tumor-infiltrating lymphocytes. In particular, we demonstrated a strong enrichment of mutations in both MHC-I- and MHC-II-negative primary lymphomas, and observed reduced MHC expression and T-cell infiltrates in murine lymphoma models expressing mutant . Of clinical relevance, EZH2 inhibitors significantly restored MHC expression in -mutated human DLBCL cell lines. Hence, our findings suggest a tumor progression model of acquired immune escape in GC-derived lymphomas and pave the way for development of complementary therapeutic approaches combining immunotherapy with epigenetic reprogramming. SIGNIFICANCE: We demonstrate how MHC-deficient lymphoid tumors evolve in a cell-of-origin-specific context. Specifically, mutations were identified as a genetic mechanism underlying acquired MHC deficiency. The paradigmatic restoration of MHC expression by EZH2 inhibitors provides the rationale for synergistic therapies combining immunotherapies with epigenetic reprogramming to enhance tumor recognition and elimination...
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http://dx.doi.org/10.1158/2159-8290.CD-18-1090DOI Listing
April 2019

Double-Hit Gene Expression Signature Defines a Distinct Subgroup of Germinal Center B-Cell-Like Diffuse Large B-Cell Lymphoma.

J Clin Oncol 2019 01 3;37(3):190-201. Epub 2018 Dec 3.

1 British Columbia Cancer Centre for Lymphoid Cancer, Vancouver, British Columbia, Canada.

Purpose: High-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements (HGBL-DH/TH) has a poor outcome after standard chemoimmunotherapy. We sought to understand the biologic underpinnings of HGBL-DH/TH with BCL2 rearrangements (HGBL-DH/TH- BCL2) and diffuse large B-cell lymphoma (DLBCL) morphology through examination of gene expression.

Patients And Methods: We analyzed RNA sequencing data from 157 de novo germinal center B-cell-like (GCB)-DLBCLs, including 25 with HGBL-DH/TH- BCL2, to define a gene expression signature that distinguishes HGBL-DH/TH- BCL2 from other GCB-DLBCLs. To assess the genetic, molecular, and phenotypic features associated with this signature, we analyzed targeted resequencing, whole-exome sequencing, RNA sequencing, and immunohistochemistry data.

Results: We developed a 104-gene double-hit signature (DHITsig) that assigned 27% of GCB-DLBCLs to the DHITsig-positive group, with only one half harboring MYC and BCL2 rearrangements (HGBL-DH/TH- BCL2). DHITsig-positive patients had inferior outcomes after rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone immunochemotherapy compared with DHITsig-negative patients (5-year time to progression rate, 57% and 81%, respectively; P < .001), irrespective of HGBL-DH/TH- BCL2 status. The prognostic value of DHITsig was confirmed in an independent validation cohort. DHITsig-positive tumors are biologically characterized by a putative non-light zone germinal center cell of origin and a distinct mutational landscape that comprises genes associated with chromatin modification. A new NanoString assay (DLBCL90) recapitulated the prognostic significance and RNA sequencing assignments. Validating the association with HGBL-DH/TH- BCL2, 11 of 25 DHITsig-positive-transformed follicular lymphomas were classified as HGBL-DH/TH- BCL2 compared with zero of 50 in the DHITsig-negative group. Furthermore, the DHITsig was shared with the majority of B-cell lymphomas with high-grade morphology tested.

Conclusion: We have defined a clinically and biologically distinct subgroup of tumors within GCB-DLBCL characterized by a gene expression signature of HGBL-DH/TH- BCL2. This knowledge has been translated into an assay applicable to routinely available biopsy samples, which enables exploration of its utility to guide patient management.
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http://dx.doi.org/10.1200/JCO.18.01583DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804880PMC
January 2019

High-resolution architecture and partner genes of rearrangements in lymphoma with DLBCL morphology.

Blood Adv 2018 10;2(20):2755-2765

Centre for Lymphoid Cancer, BC Cancer, Vancouver, BC, Canada.

Genomic rearrangements in the locus occur in ∼12% of lymphomas with diffuse large B-cell lymphoma (DLBCL) morphology and are associated with inferior outcome. Previous studies exploring rearrangements have primarily used fluorescence in situ hybridization (FISH) assays to characterize break-apart status but have rarely examined breakpoint location, and in some cases have not examined partner identity. We performed targeted sequencing of , , , and the immunoglobulin () loci in 112 tumors with DLBCL morphology harboring rearrangement. We characterized the location of the rearrangement at base pair resolution and identified the partner in 88 cases. We observed a cluster of breakpoints upstream of the coding region and in intron 1 (the "genic cluster"). Genic cluster rearrangements were enriched for translocations involving (80%), whereas nongenic rearrangements occurred mostly downstream of the gene with a variety of partners, including and Other recurrent partners included , , and , which has not previously been described as a partner. We compared 2 commercially available FISH break-apart assays for the locus and observed discordant results in 32% of cases examined, including some with - and - rearrangements. In cases of high-grade B-cell lymphoma with and and/or rearrangement (HGBL-DH), so-called "double-hit" lymphomas, the majority of rearrangements had non- partners (65%), with breakpoints outside the genic cluster (72%). In patients with de novo HGBL-DH of DLBCL morphology, - rearrangements showed a trend toward inferior time to progression and overall survival compared with -non- rearrangements. Our data reveal clinically relevant architecture of rearrangements in lymphomas with DLBCL morphology.
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http://dx.doi.org/10.1182/bloodadvances.2018023572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6199666PMC
October 2018

Genome-wide discovery of somatic regulatory variants in diffuse large B-cell lymphoma.

Nat Commun 2018 10 1;9(1):4001. Epub 2018 Oct 1.

Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.

Diffuse large B-cell lymphoma (DLBCL) is an aggressive cancer originating from mature B-cells. Prognosis is strongly associated with molecular subgroup, although the driver mutations that distinguish the two main subgroups remain poorly defined. Through an integrative analysis of whole genomes, exomes, and transcriptomes, we have uncovered genes and non-coding loci that are commonly mutated in DLBCL. Our analysis has identified novel cis-regulatory sites, and implicates recurrent mutations in the 3' UTR of NFKBIZ as a novel mechanism of oncogene deregulation and NF-κB pathway activation in the activated B-cell (ABC) subgroup. Small amplifications associated with over-expression of FCGR2B (the Fcγ receptor protein IIB), primarily in the germinal centre B-cell (GCB) subgroup, correlate with poor patient outcomes suggestive of a novel oncogene. These results expand the list of subgroup driver mutations that may facilitate implementation of improved diagnostic assays and could offer new avenues for the development of targeted therapeutics.
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http://dx.doi.org/10.1038/s41467-018-06354-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167379PMC
October 2018

The MCL35 gene expression proliferation assay predicts high-risk MCL patients in a Norwegian cohort of younger patients given intensive first line therapy.

Br J Haematol 2018 10 6;183(2):225-234. Epub 2018 Aug 6.

Department of Oncology, Oslo University Hospital, Oslo, Norway.

Patients with mantle cell lymphoma (MCL) generally have a dismal prognosis. Intensified induction treatment with rituximab and high dose cytarabine (R_HDAC), and consolidation with high-dose therapy with autologous stem cell support has resulted in 10-year overall survival (OS) higher than 60%. However, the clinical course varies. Diagnostic tools capable of stratifying patients include the MCL International Prognostic Index (MIPI), gene expression-based proliferation signature, Ki-67 proliferation index or tumour cell morphology. Here, we tested the performance of a newly developed Nanostring-based RNA expression-based proliferation assay (MCL35) on formalin-fixed paraffin-embedded tumour tissue from younger patients recruited in or treated according to Nordic MCL protocols compared to the prognosticators listed above. Seventy-four patients were included and the assay performed well in all cases except four, which had inadequate RNA quality. The patients were evenly distributed in the MCL35 low-, intermediate- and high-risk categories. MCL35 low- and intermediate- risk groups had overlapping progression-free survival (PFS), while patients in the high-risk category had significantly inferior PFS. Combining MCL35 with MIPI or the MIPI-C (MIPI with the addition of binary Ki67 score +/-30%) showed a better discrimination than either assessment alone. In conclusion, the MCL35 assay alone or combined with MIPI or MIPI-C scores can identify patients who still have a dismal outcome despite intensified treatment.
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http://dx.doi.org/10.1111/bjh.15518DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6530911PMC
October 2018

Assessment of Capture and Amplicon-Based Approaches for the Development of a Targeted Next-Generation Sequencing Pipeline to Personalize Lymphoma Management.

J Mol Diagn 2018 03 8;20(2):203-214. Epub 2018 Feb 8.

Centre for Lymphoid Cancer, BC Cancer Agency, Vancouver, British Columbia, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Targeted next-generation sequencing panels are increasingly used to assess the value of gene mutations for clinical diagnostic purposes. For assay development, amplicon-based methods have been preferentially used on the basis of short preparation time and small DNA input amounts. However, capture sequencing has emerged as an alternative approach because of high testing accuracy. We compared capture hybridization and amplicon sequencing approaches using fresh-frozen and formalin-fixed, paraffin-embedded tumor samples from eight lymphoma patients. Next, we developed a targeted sequencing pipeline using a 32-gene panel for accurate detection of actionable mutations in formalin-fixed, paraffin-embedded tumor samples of the most common lymphocytic malignancies: chronic lymphocytic leukemia, diffuse large B-cell lymphoma, and follicular lymphoma. We show that hybrid capture is superior to amplicon sequencing by providing deep more uniform coverage and yielding higher sensitivity for variant calling. Sanger sequencing of 588 variants identified specificity limits of thresholds for mutation calling, and orthogonal validation on 66 cases indicated 93% concordance with whole-genome sequencing. The developed pipeline and assay identified at least one actionable mutation in 91% of tumors from 219 lymphoma patients and revealed subtype-specific mutation patterns and frequencies consistent with the literature. This pipeline is an accurate and sensitive method for identifying actionable gene mutations in routinely acquired biopsy materials, suggesting further assessment of capture-based assays in the context of personalized lymphoma management.
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http://dx.doi.org/10.1016/j.jmoldx.2017.11.010DOI Listing
March 2018

Genetic profiling of and in diffuse large B-cell lymphoma determines cell-of-origin-specific clinical impact.

Blood 2017 05 28;129(20):2760-2770. Epub 2017 Mar 28.

Centre for Lymphoid Cancer.

The clinical significance of and genetic alterations in diffuse large B-cell lymphoma (DLBCL), apart from translocations, has not been comprehensively investigated using high-resolution genetic assays. In this study, we profiled and genetic alterations using next-generation sequencing and high-resolution SNP array in 347 de novo DLBCL cases treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) at the British Columbia Cancer Agency. Cell-of-origin (COO) subtype was determined by Lymph2Cx digital gene expression profiling. We showed that the incidence of / genetic alterations and their clinical significance were largely dependent on COO subtypes. It is noteworthy that the presence of gain/amplification is significantly associated with poor outcome in activated B-cell-like and translocation with poor outcome in germinal center B-cell subtypes, respectively. Both have prognostic significance independent of MYC/BCL2 dual expression and the International Prognostic Index (IPI). Furthermore, the combination of genetic alterations with IPI identifies markedly worse prognostic groups within individual COO subtypes. Thus, high-resolution genomic assays identify extremely poor prognostic groups within each COO subtype on the basis of genetic status in this large, uniformly R-CHOP-treated population-based cohort of DLBCL. These results suggest COO subtype-specific biomarkers based on genetic alterations can be used to risk-stratify patients with DLBCL treated with immunochemotherapy.
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http://dx.doi.org/10.1182/blood-2016-11-747022DOI Listing
May 2017

New Molecular Assay for the Proliferation Signature in Mantle Cell Lymphoma Applicable to Formalin-Fixed Paraffin-Embedded Biopsies.

J Clin Oncol 2017 May 14;35(15):1668-1677. Epub 2017 Mar 14.

David W. Scott, Pau Abrisqueta, Graham W. Slack, Anja Mottok, Diego Villa, Merrill Boyle, Fong Chun Chan, Christian Steidl, Joseph M. Connors, and Randy D. Gascoyne, BC Cancer Agency; Anja Mottok, Christian Steidl, and Randy D. Gascoyne, University of British Columbia, Vancouver, British Columbia; Jan Delabie, University of Toronto, Toronto, Ontario, Canada; Pau Abrisqueta, Vall d'Hebron University Hospital; Pedro Jares, Cristina Royo, Guillem Clot, Magda Pinyol, and Elias Campo, Universitat de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain; George W. Wright, Elaine S. Jaffe, and Louis M. Staudt, National Institutes of Health, Bethesda, MD; Hilka Rauert-Wunderlich and Andreas Rosenwald, University of Würzburg, Würzburg; German Ott, Robert Bosch Hospital and Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany; Rita M. Braziel, Oregon Health & Sciences University, Portland, OR; Wing C. Chan and Dennis D. Weisenburger, City of Hope, Duarte, CA; James R. Cook, Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH; Timothy C. Greiner and Kai Fu, University of Nebraska Medical Center, Omaha, NE; Erlend B. Smeland and Harald Holte, Oslo University Hospital, Oslo, Norway; and Lisa M. Rimsza, Mayo Clinic, Phoenix, AZ.

Purpose Mantle cell lymphoma is an aggressive B-cell neoplasm that displays heterogeneous outcomes after treatment. In 2003, the Lymphoma/Leukemia Molecular Profiling Project described a powerful biomarker-the proliferation signature-using gene expression in fresh frozen material. Herein, we describe the training and validation of a new assay that measures the proliferation signature in RNA derived from routinely available formalin-fixed paraffin-embedded (FFPE) biopsies. Methods Forty-seven FFPE biopsies were used to train an assay on the NanoString platform, using microarray gene expression data of matched fresh frozen biopsies as a gold standard. The locked assay was applied to pretreatment FFPE lymph node biopsies from an independent cohort of 110 patients uniformly treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone. Seventeen biopsies were tested across three laboratories to assess assay reproducibility. Results The MCL35 assay, which contained a 17-gene proliferation signature, yielded gene expression of sufficient quality to assign an assay score and risk group in 108 (98%) of 110 archival FFPE biopsies. The MCL35 assay assigned patients to high-risk (26%), standard-risk (29%), and low-risk (45%) groups, with different lengths of overall survival (OS): a median of 1.1, 2.6, and 8.6 years, respectively (log-rank for trend, P < .001). In multivariable analysis, these risk groups and the Mantle Cell Lymphoma International Prognostic Index were independently associated with OS ( P < .001 for both variables). Concordance of risk assignment across the three independent laboratories was 100%. Conclusion The newly developed and validated MCL35 assay for FFPE biopsies uses the proliferation signature to define groups of patients with significantly different OS independent of the Mantle Cell Lymphoma International Prognostic Index. Importantly, the analytic and clinical validity of this assay defines it as a reliable biomarker to support risk-adapted clinical trials.
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http://dx.doi.org/10.1200/JCO.2016.70.7901DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5455765PMC
May 2017

Histological Transformation and Progression in Follicular Lymphoma: A Clonal Evolution Study.

PLoS Med 2016 Dec 13;13(12):e1002197. Epub 2016 Dec 13.

Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia, Canada.

Background: Follicular lymphoma (FL) is an indolent, yet incurable B cell malignancy. A subset of patients experience an increased mortality rate driven by two distinct clinical end points: histological transformation and early progression after immunochemotherapy. The nature of tumor clonal dynamics leading to these clinical end points is poorly understood, and previously determined genetic alterations do not explain the majority of transformed cases or accurately predict early progressive disease. We contend that detailed knowledge of the expansion patterns of specific cell populations plus their associated mutations would provide insight into therapeutic strategies and disease biology over the time course of FL clinical histories.

Methods And Findings: Using a combination of whole genome sequencing, targeted deep sequencing, and digital droplet PCR on matched diagnostic and relapse specimens, we deciphered the constituent clonal populations in 15 transformation cases and 6 progression cases, and measured the change in clonal population abundance over time. We observed widely divergent patterns of clonal dynamics in transformed cases relative to progressed cases. Transformation specimens were generally composed of clones that were rare or absent in diagnostic specimens, consistent with dramatic clonal expansions that came to dominate the transformation specimens. This pattern was independent of time to transformation and treatment modality. By contrast, early progression specimens were composed of clones that were already present in the diagnostic specimens and exhibited only moderate clonal dynamics, even in the presence of immunochemotherapy. Analysis of somatic mutations impacting 94 genes was undertaken in an extension cohort consisting of 395 samples from 277 patients in order to decipher disrupted biology in the two clinical end points. We found 12 genes that were more commonly mutated in transformed samples than in the preceding FL tumors, including TP53, B2M, CCND3, GNA13, S1PR2, and P2RY8. Moreover, ten genes were more commonly mutated in diagnostic specimens of patients with early progression, including TP53, BTG1, MKI67, and XBP1.

Conclusions: Our results illuminate contrasting modes of evolution shaping the clinical histories of transformation and progression. They have implications for interpretation of evolutionary dynamics in the context of treatment-induced selective pressures, and indicate that transformation and progression will require different clinical management strategies.
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http://dx.doi.org/10.1371/journal.pmed.1002197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5154502PMC
December 2016

Genomic Alterations in CIITA Are Frequent in Primary Mediastinal Large B Cell Lymphoma and Are Associated with Diminished MHC Class II Expression.

Cell Rep 2015 Nov 5;13(7):1418-1431. Epub 2015 Nov 5.

Centre for Lymphoid Cancer, Department of Lymphoid Cancer Research, BC Cancer Agency, Vancouver, BC V5Z 1L3, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC V6T 2B5, Canada. Electronic address:

Primary mediastinal large B cell lymphoma (PMBCL) is an aggressive non-Hodgkin's lymphoma, predominantly affecting young patients. We analyzed 45 primary PMBCL tumor biopsies and 3 PMBCL-derived cell lines for the presence of genetic alterations involving the major histocompatibility complex (MHC) class II transactivator CIITA and found frequent aberrations consisting of structural genomic rearrangements, missense, nonsense, and frame-shift mutations (53% of primary tumor biopsies and all cell lines). We also detected intron 1 mutations in 47% of the cases, and detailed sequence analysis strongly suggests AID-mediated aberrant somatic hypermutation as the mutational mechanism. Furthermore, we demonstrate that genomic lesions in CIITA result in decreased protein expression and reduction of MHC class II surface expression, creating an immune privilege phenotype in PMBCL. In summary, we establish CIITA alterations as a common mechanism of immune escape through reduction of MHC class II expression in PMBCL, with potential implications for future treatments targeting microenvironment-related biology.
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http://dx.doi.org/10.1016/j.celrep.2015.10.008DOI Listing
November 2015

Cell of origin of transformed follicular lymphoma.

Blood 2015 Oct 25;126(18):2118-27. Epub 2015 Aug 25.

Centre for Lymphoid Cancer, BC Cancer Agency, Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, and.

Follicular lymphoma (FL) is an indolent disease but transforms in 2% to 3% of patients per year into aggressive, large cell lymphoma, a critical event in the course of the disease associated with increased lymphoma-related mortality. Early transformation cannot be accurately predicted at the time of FL diagnosis and the biology of transformed FL (TFL) is poorly understood. Here, we assembled a cohort of 126 diagnostic FL specimens including 40 patients experiencing transformation (<5 years) and 86 patients not experiencing transformation for at least 5 years. In addition, we assembled an overlapping cohort of 155 TFL patients, including 114 cases for which paired samples were available, and assessed temporal changes of routinely available biomarkers, outcome after transformation, as well as molecular subtypes of TFL. We report that the expression of IRF4 is an independent predictor of early transformation (Hazard ratio, 13.3; P < .001). We also show that composite histology at the time of transformation predicts favorable prognosis. Moreover, applying the Lymph2Cx digital gene expression assay for diffuse large B-cell lymphoma (DLBCL) cell-of-origin determination to 110 patients with DLBCL-like TFL, we demonstrate that TFL is of the germinal-center B-cell-like subtype in the majority of cases (80%) but that a significant proportion of cases is of the activated B-cell-like (ABC) subtype (16%). These latter cases are commonly negative for BCL2 translocation and arise preferentially from BCL2 translocation-negative and/or IRF4-expressing FLs. Our study demonstrates the existence of molecular heterogeneity in TFL as well as its relationship to the antecedent FL.
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http://dx.doi.org/10.1182/blood-2015-06-649905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4626253PMC
October 2015

Prognostic Significance of Diffuse Large B-Cell Lymphoma Cell of Origin Determined by Digital Gene Expression in Formalin-Fixed Paraffin-Embedded Tissue Biopsies.

J Clin Oncol 2015 Sep 3;33(26):2848-56. Epub 2015 Aug 3.

David W. Scott, Anja Mottok, Daisuke Ennishi, Pedro Farinha, Susana Ben-Neriah, Robert Kridel, Garrett S. Barry, Christoffer Hother, Pau Abrisqueta, Merrill Boyle, Barbara Meissner, Adele Telenius, Kerry J. Savage, Laurie H. Sehn, Graham W. Slack, Christian Steidl, Joseph M. Connors, and Randy D. Gascoyne, British Columbia Cancer Agency, Vancouver, British Columbia, Canada; George W. Wright and Louis M. Staudt, National Cancer Institute, Bethesda, MD; and Lisa M. Rimsza, University of Arizona, Tucson, AZ.

Purpose: To evaluate the prognostic impact of cell-of-origin (COO) subgroups, assigned using the recently described gene expression-based Lymph2Cx assay in comparison with International Prognostic Index (IPI) score and MYC/BCL2 coexpression status (dual expressers).

Patients And Methods: Reproducibility of COO assignment using the Lymph2Cx assay was tested employing repeated sampling within tumor biopsies and changes in reagent lots. The assay was then applied to pretreatment formalin-fixed paraffin-embedded tissue (FFPET) biopsies from 344 patients with de novo diffuse large B-cell lymphoma (DLBCL) uniformly treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) at the British Columbia Cancer Agency. MYC and BCL2 protein expression was assessed using immunohistochemistry on tissue microarrays.

Results: The Lymph2Cx assay provided concordant COO calls in 96% of 49 repeatedly sampled tumor biopsies and in 100% of 83 FFPET biopsies tested across reagent lots. Critically, no frank misclassification (activated B-cell-like DLBCL to germinal center B-cell-like DLBCL or vice versa) was observed. Patients with activated B-cell-like DLBCL had significantly inferior outcomes compared with patients with germinal center B-cell-like DLBCL (log-rank P < .001 for time to progression, progression-free survival, disease-specific survival, and overall survival). In pairwise multivariable analyses, COO was associated with outcomes independent of IPI score and MYC/BCL2 immunohistochemistry. The prognostic significance of COO was particularly evident in patients with intermediate IPI scores and the non-MYC-positive/BCL2-positive subgroup (log-rank P < .001 for time to progression).

Conclusion: Assignment of DLBCL COO by the Lymph2Cx assay using FFPET biopsies identifies patient groups with significantly different outcomes after R-CHOP, independent of IPI score and MYC/BCL2 dual expression.
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http://dx.doi.org/10.1200/JCO.2014.60.2383DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4554747PMC
September 2015

Comprehensive miRNA sequence analysis reveals survival differences in diffuse large B-cell lymphoma patients.

Genome Biol 2015 Jan 29;16:18. Epub 2015 Jan 29.

Background: Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease, with 30% to 40% of patients failing to be cured with available primary therapy. microRNAs (miRNAs) are RNA molecules that attenuate expression of their mRNA targets. To characterize the DLBCL miRNome, we sequenced miRNAs from 92 DLBCL and 15 benign centroblast fresh frozen samples and from 140 DLBCL formalin-fixed, paraffin-embedded tissue samples for validation.

Results: We identify known and candidate novel miRNAs, 25 of which are associated with survival independently of cell-of-origin and International Prognostic Index scores, which are established indicators of outcome. Of these 25 miRNAs, six miRNAs are significantly associated with survival in our validation cohort. Abundant expression of miR-28-5p, miR-214-5p, miR-339-3p, and miR-5586-5p is associated with superior outcome, while abundant expression of miR-324-5p and NOVELM00203M is associated with inferior outcome. Comparison of DLBCL miRNA-seq expression profiles with those from other cancer types identifies miRNAs that were more abundant in B-cell contexts. Unsupervised clustering of miRNAs identifies two clusters of patients that have distinct differences in their outcomes. Our integrative miRNA and mRNA expression analyses reveal that miRNAs increased in abundance in DLBCL appear to regulate the expression of genes involved in metabolism, cell cycle, and protein modification. Additionally, these miRNAs, including one candidate novel miRNA, miR-10393-3p, appear to target chromatin modification genes that are frequent targets of somatic mutation in non-Hodgkin lymphomas.

Conclusions: Our comprehensive sequence analysis of the DLBCL miRNome identifies candidate novel miRNAs and miRNAs associated with survival, reinforces results from previous mutational analyses, and reveals regulatory networks of significance for lymphomagenesis.
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http://dx.doi.org/10.1186/s13059-014-0568-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4308918PMC
January 2015

Recurrent somatic mutations of PTPN1 in primary mediastinal B cell lymphoma and Hodgkin lymphoma.

Nat Genet 2014 Apr 16;46(4):329-35. Epub 2014 Feb 16.

1] Centre for Lymphoid Cancer, BC Cancer Agency, Vancouver, British Columbia, Canada. [2] Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.

Classical Hodgkin lymphoma and primary mediastinal B cell lymphoma (PMBCL) are related lymphomas sharing pathological, molecular and clinical characteristics. Here we discovered by whole-genome and whole-transcriptome sequencing recurrent somatic coding-sequence mutations in the PTPN1 gene. Mutations were found in 6 of 30 (20%) Hodgkin lymphoma cases, in 6 of 9 (67%) Hodgkin lymphoma-derived cell lines, in 17 of 77 (22%) PMBCL cases and in 1 of 3 (33%) PMBCL-derived cell lines, consisting of nonsense, missense and frameshift mutations. We demonstrate that PTPN1 mutations lead to reduced phosphatase activity and increased phosphorylation of JAK-STAT pathway members. Moreover, silencing of PTPN1 by RNA interference in Hodgkin lymphoma cell line KM-H2 resulted in hyperphosphorylation and overexpression of downstream oncogenic targets. Our data establish PTPN1 mutations as new drivers in lymphomagenesis.
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http://dx.doi.org/10.1038/ng.2900DOI Listing
April 2014

Gene expression-based model using formalin-fixed paraffin-embedded biopsies predicts overall survival in advanced-stage classical Hodgkin lymphoma.

J Clin Oncol 2013 Feb 26;31(6):692-700. Epub 2012 Nov 26.

Centre for Lymphoid Cancer, BC Cancer Agency, Vancouver, British Columbia, Canada.

Purpose: Our aim was to reliably identify patients with advanced-stage classical Hodgkin lymphoma (cHL) at increased risk of death by developing a robust predictor of overall survival (OS) using gene expression measured in routinely available formalin-fixed paraffin-embedded tissue (FFPET).

Methods: Expression levels of 259 genes, including those previously reported to be associated with outcome in cHL, were determined by digital expression profiling of pretreatment FFPET biopsies from 290 patients enrolled onto the E2496 Intergroup trial comparing doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) and Stanford V regimens in locally extensive and advanced-stage cHL. A model for OS separating patients into low- and high-risk groups was produced using penalized Cox regression. The model was tested in an independent cohort of 78 patients enriched for treatment failure but otherwise similar to patients in a population-based registry of patients treated with ABVD. Weighted analysis methods generated unbiased estimates of predictor performance in the population-based registry.

Results: A 23-gene outcome predictor was generated. The model identified a population at increased risk of death in the validation cohort. There was a 29% absolute difference in 5-year OS between the high- and low-risk groups (63% v 92%, respectively; log-rank P < .001; hazard ratio, 6.7; 95% CI, 2.6 to 17.4). The predictor was superior to the International Prognostic Score and CD68 immunohistochemistry in multivariate analyses.

Conclusion: A gene expression-based predictor, developed in and applicable to routinely available FFPET biopsies, identifies patients with advanced-stage cHL at increased risk of death when treated with standard-intensity up-front regimens.
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http://dx.doi.org/10.1200/JCO.2012.43.4589DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574267PMC
February 2013

Whole transcriptome sequencing reveals recurrent NOTCH1 mutations in mantle cell lymphoma.

Blood 2012 Mar 30;119(9):1963-71. Epub 2011 Dec 30.

Centre for Lymphoid Cancer, British Columbia Cancer Agency, 675 W.10th Ave.,Vancouver, BC, Canada.

Mantle cell lymphoma (MCL), an aggressive subtype of non-Hodgkin lymphoma, is characterized by the hallmark translocation t(11;14)(q13;q32) and the resulting overexpression of cyclin D1 (CCND1). Our current knowledge of this disease encompasses frequent secondary cytogenetic aberrations and the recurrent mutation of a handful of genes, such as TP53, ATM, and CCND1. However, these findings insufficiently explain the biologic underpinnings of MCL. Here, we performed whole transcriptome sequencing on a discovery cohort of 18 primary tissue MCL samples and 2 cell lines. We found recurrent mutations in NOTCH1, a finding that we confirmed in an extension cohort of 108 clinical samples and 8 cell lines. In total, 12% of clinical samples and 20% of cell lines harbored somatic NOTCH1 coding sequence mutations that clustered in the PEST domain and predominantly consisted of truncating mutations or small frame-shifting indels. NOTCH1 mutations were associated with poor overall survival (P = .003). Furthermore, we showed that inhibition of the NOTCH pathway reduced proliferation and induced apoptosis in 2 MCL cell lines. In summary, we have identified recurrent NOTCH1 mutations that provide the preclinical rationale for therapeutic inhibition of the NOTCH pathway in a subset of patients with MCL.
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http://dx.doi.org/10.1182/blood-2011-11-391474DOI Listing
March 2012

Frequent mutation of histone-modifying genes in non-Hodgkin lymphoma.

Nature 2011 Jul 27;476(7360):298-303. Epub 2011 Jul 27.

Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada.

Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) are the two most common non-Hodgkin lymphomas (NHLs). Here we sequenced tumour and matched normal DNA from 13 DLBCL cases and one FL case to identify genes with mutations in B-cell NHL. We analysed RNA-seq data from these and another 113 NHLs to identify genes with candidate mutations, and then re-sequenced tumour and matched normal DNA from these cases to confirm 109 genes with multiple somatic mutations. Genes with roles in histone modification were frequent targets of somatic mutation. For example, 32% of DLBCL and 89% of FL cases had somatic mutations in MLL2, which encodes a histone methyltransferase, and 11.4% and 13.4% of DLBCL and FL cases, respectively, had mutations in MEF2B, a calcium-regulated gene that cooperates with CREBBP and EP300 in acetylating histones. Our analysis suggests a previously unappreciated disruption of chromatin biology in lymphomagenesis.
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http://dx.doi.org/10.1038/nature10351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210554PMC
July 2011

Somatic mutations at EZH2 Y641 act dominantly through a mechanism of selectively altered PRC2 catalytic activity, to increase H3K27 trimethylation.

Blood 2011 Feb 29;117(8):2451-9. Epub 2010 Dec 29.

Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.

Next-generation sequencing of follicular lymphoma and diffuse-large B-cell lymphoma has revealed frequent somatic, heterozygous Y641 mutations in the histone methyltransferase EZH2. Heterozygosity and the presence of equal quantities of both mutant and wild-type mRNA and expressed protein suggest a dominant mode of action. Surprisingly, B-cell lymphoma cell lines and lymphoma samples harboring heterozygous EZH2(Y641) mutations have increased levels of histone H3 Lys-27-specific trimethylation (H3K27me3). Expression of EZH2(Y641F/N) mutants in cells with EZH2(WT) resulted in an increase of H3K27me3 levels in vivo. Structural modeling of EZH2(Y641) mutants suggests a "Tyr/Phe switch" model whereby structurally neutral, nontyrosine residues at position 641 would decrease affinity for unmethylated and monomethylated H3K27 substrates and potentially favor trimethylation. We demonstrate, using in vitro enzyme assays of reconstituted PRC2 complexes, that Y641 mutations result in a decrease in monomethylation and an increase in trimethylation activity of the enzyme relative to the wild-type enzyme. This represents the first example of a disease-associated gain-of-function mutation in a histone methyltransferase, whereby somatic EZH2 Y641 mutations in lymphoma act dominantly to increase, rather than decrease, histone methylation. The dominant mode of action suggests that allele-specific EZH2 inhibitors should be a future therapeutic strategy for this disease.
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http://dx.doi.org/10.1182/blood-2010-11-321208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062411PMC
February 2011

High resolution analysis of follicular lymphoma genomes reveals somatic recurrent sites of copy-neutral loss of heterozygosity and copy number alterations that target single genes.

Genes Chromosomes Cancer 2010 Aug;49(8):669-81

Center for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, BC, Canada.

A multiplatform approach, including conventional cytogenetic techniques, BAC array comparative genomic hybridization, and Affymetrix 500K SNP arrays, was applied to the study of the tumor genomes of 25 follicular lymphoma biopsy samples with paired normal DNA samples to characterize balanced translocations, copy number imbalances, and copy-neutral loss of heterozygosity (cnLOH). In addition to the t(14;18), eight unique balanced translocations were found. Commonly reported FL-associated copy number regions were revealed including losses of 1p32-36, 6q, and 10q, and gains of 1q, 6p, 7, 12, 18, and X. The most frequent regions affected by copy-neutral loss of heterozygosity were 1p36.33 (28%), 6p21.3 (20%), 12q21.2-q24.33 (16%), and 16p13.3 (24%). We also identified by SNP analysis, 45 aberrant regions that each affected one gene, including CDKN2A, CDKN2B, FHIT, KIT, PEX14, and PTPRD, which were associated with canonical pathways involved in tumor development. This study illustrates the power of using complementary high-resolution platforms on paired tumor/normal specimens and computational analysis to provide potential insights into the significance of single-gene somatic aberrations in FL tumorigenesis.
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http://dx.doi.org/10.1002/gcc.20780DOI Listing
August 2010

Genome-wide copy number analysis of Hodgkin Reed-Sternberg cells identifies recurrent imbalances with correlations to treatment outcome.

Blood 2010 Jul 25;116(3):418-27. Epub 2010 Mar 25.

Department of Pathology and Laboratory Medicine, Centre for Translational and Applied Genomics, BC Cancer Agency, University of British Columbia, Vancouver, BC, Canada.

In classical Hodgkin lymphoma (cHL) the mechanisms underlying primary refractory disease and relapse remain unknown. To gain further insight into cHL pathogenesis and genomic changes linked to treatment response, we studied 53 cHL patients by array comparative genomic hybridization, including 23 patients whose primary treatment failed, using DNA from microdissected HRS cells. Copy number alterations found in more than 20% of cases included gains of 2p, 9p, 16p, 17q, 19q, 20q, and losses of 6q, 11q, and 13q. We identified at high resolution recurrent changes defining minimally gained and lost regions harboring genes involved in nuclear factor kappaB signaling, such as REL, IKBKB, CD40, and MAP3K14. Gains of chromosome 16p11.2-13.3 were significantly more frequent in pretreatment and relapse biopsies of unresponsive patients and were associated with shortened disease-specific survival (P = .028). In the therapy-resistant HL cell line KMH2, we found genomic gains and overexpression of the multidrug resistance gene ABCC1 mapping to cytoband 16p13.11. We show that doxorubicin exposure to KMH2 induces ABCC1 expression and that siRNA silencing of ABCC1 sensitizes KMH2 cells to doxorubicin toxicity in vitro, suggesting that overexpression of ABCC1 contributes to the drug resistance phenotype found in KMH2.
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http://dx.doi.org/10.1182/blood-2009-12-257345DOI Listing
July 2010

Somatic mutations altering EZH2 (Tyr641) in follicular and diffuse large B-cell lymphomas of germinal-center origin.

Nat Genet 2010 Feb 17;42(2):181-5. Epub 2010 Jan 17.

Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia, Canada.

Follicular lymphoma (FL) and the GCB subtype of diffuse large B-cell lymphoma (DLBCL) derive from germinal center B cells. Targeted resequencing studies have revealed mutations in various genes encoding proteins in the NF-kappaB pathway that contribute to the activated B-cell (ABC) DLBCL subtype, but thus far few GCB-specific mutations have been identified. Here we report recurrent somatic mutations affecting the polycomb-group oncogene EZH2, which encodes a histone methyltransferase responsible for trimethylating Lys27 of histone H3 (H3K27). After the recent discovery of mutations in KDM6A (UTX), which encodes the histone H3K27me3 demethylase UTX, in several cancer types, EZH2 is the second histone methyltransferase gene found to be mutated in cancer. These mutations, which result in the replacement of a single tyrosine in the SET domain of the EZH2 protein (Tyr641), occur in 21.7% of GCB DLBCLs and 7.2% of FLs and are absent from ABC DLBCLs. Our data are consistent with the notion that EZH2 proteins with mutant Tyr641 have reduced enzymatic activity in vitro.
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http://dx.doi.org/10.1038/ng.518DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850970PMC
February 2010

Diffuse large B-cell lymphoma: reduced CD20 expression is associated with an inferior survival.

Blood 2009 Apr 24;113(16):3773-80. Epub 2008 Nov 24.

Department of Pathology and Laboratory Medicine, British Columbia Cancer Agency, Vancouver, Canada.

CD19 and CD20 are B cell-specific antigens whose expression is heterogeneous when analyzed by flow cytometry (FCM). We determined the association between CD20 expression and clinical outcome in patients with diffuse large B-cell lymphoma (DLBCL). The mean fluorescence intensity of CD20 and CD19 was determined by FCM, and the cytoplasmic expression of CD20 was determined by immunohistochemistry (IHC) on 272 diagnostic DLBCL samples. Exon 5 of the MS4A1 gene coding for the extracellular component of the CD20 antigen was sequenced in 15 samples. A total of 43 of 272 (16%) samples had reduced CD20 expression by FCM; of these, 35 (13%) had bright CD19 expression. The latter had a markedly inferior survival when treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or rituximab-CHOP (R-CHOP; median survival of 1.2 and 3.0 years vs not reached for the others, P < .001 and P = .001), independent of the International Prognostic Index. A total of 41 of 43 samples with reduced CD20 expression by FCM had strong staining for CD20 by IHC. There were no mutations in exon 5 of the MS4A1 gene to explain the discrepancy between FCM and IHC. CD20 and CD19 expression by FCM should be determined on all biopsies of patients with DLBCL because reduced CD20 expression cannot be reliably detected by IHC.
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http://dx.doi.org/10.1182/blood-2008-09-177469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943836PMC
April 2009