EZH2 mutations in follicular lymphoma distort H3K27me3 profiles and alter transcriptional responses to PRC2 inhibition

Mutations in chromatin regulators are widespread in cancer. Among them, the histone H3 lysine 27 methyltransferase Polycomb Repressive Complex 2 (PRC2) shows distinct alterations according to tumor type. This specificity is poorly understood. Here, we model several PRC2 alterations in one isogenic system to reveal their comparative effects. Focusing then on lymphoma-associated EZH2 mutations, we show that Ezh2Y641F induces aberrant H3K27 methylation patterns even without wild-type Ezh2, which are alleviated by partial PRC2 inhibition. Remarkably, Ezh2Y641F rewires the response to PRC2 inhibition, leading to induction of antigen presentation genes. Using a unique longitudinal follicular lymphoma cohort, we further link EZH2 status to abnormal H3K27 methylation. We also uncover unexpected variability in the mutational landscape of successive biopsies, pointing to frequent co-existence of different clones and cautioning against stratifying patients based on single sampling. Our results clarify how oncogenic PRC2 mutations disrupt chromatin and transcription, and the therapeutic vulnerabilities this creates.

Novel insights into the pathogenesis of follicular lymphoma by molecular profiling of localized and systemic disease forms

Knowledge on the pathogenesis of FL is mainly based on data derived from advanced/systemic stages of FL (sFL) and only small cohorts of localized FL (lFL) have been characterized intensively so far. Comprehensive analysis with profiling of somatic copy number alterations (SCNA) and whole exome sequencing (WES) was performed in 147 lFL and 122 sFL. Putative targets were analyzed for gene and protein expression. Overall, lFL and sFL, as well as BCL2 translocation-positive (BCL2+) and -negative (BCL2-) FL showed overlapping features in SCNA and mutational profiles. Significant differences between lFL and sFL, however, were detected for SCNA frequencies, e.g., in 18q-gains (14% lFL vs. 36% sFL; p = 0.0003). Although rare in lFL, gains in 18q21 were associated with inferior progression-free survival (PFS). The mutational landscape of lFL and sFL included typical genetic lesions. However, ARID1A mutations were significantly more often detected in sFL (29%) compared to lFL (6%, p = 0.0001). In BCL2 + FL mutations in KMT2D, BCL2, ABL2, IGLL5 and ARID1A were enriched, while STAT6 mutations more frequently occurred in BCL2- FL. Although the landscape of lFL and sFL showed overlapping features, molecular profiling revealed novel insights and identified gains in 18q21 as prognostic marker in lFL.

KMT2D acetylation by CREBBP reveals a cooperative functional interaction at enhancers in normal and malignant germinal center B cells

Heterozygous inactivating mutations of the KMT2D methyltransferase and the CREBBP acetyltransferase are among the most common genetic alterations in B cell lymphoma and co-occur in 40 to 60% of follicular lymphoma (FL) and 30% of EZB/C3 diffuse large B cell lymphoma (DLBCL) cases, suggesting they may be coselected. Here, we show that combined germinal center (GC)-specific haploinsufficiency of Crebbp and Kmt2d synergizes in vivo to promote the expansion of abnormally polarized GCs, a common preneoplastic event. These enzymes form a biochemical complex on select enhancers/superenhancers that are critical for the delivery of immune signals in the GC light zone and are only corrupted upon dual Crebbp/Kmt2d loss, both in mouse GC B cells and in human DLBCL. Moreover, CREBBP directly acetylates KMT2D in GC-derived B cells, and, consistently, its inactivation by FL/DLBCL-associated mutations abrogates its ability to catalyze KMT2D acetylation. Genetic and pharmacologic loss of CREBBP and the consequent decrease in KMT2D acetylation lead to reduced levels of H3K4me1, supporting a role for this posttranslational modification in modulating KMT2D activity. Our data identify a direct biochemical and functional interaction between CREBBP and KMT2D in the GC, with implications for their role as tumor suppressors in FL/DLBCL and for the development of precision medicine approaches targeting enhancer defects induced by their combined loss.

Mutations in V-ATPase in follicular lymphoma activate autophagic flux creating a targetable dependency

The recent discovery of recurrent gene mutations in chaperones or components of the vacuolar-type H+-translocating ATPase (V-ATPase) in follicular lymphoma (FL) was an unexpected finding. The application of whole exome sequencing and targeted gene re-sequencing has resulted in the identification of mutations in ATP6AP1, ATP6V1B2 and VMA21 in a combined 30% of FL, together constituting a major novel mutated pathway in this disease. Interestingly, no other human hematological malignancy carries these mutations at more than sporadic occurrences, implicating unique aspects of FL biology requiring these mutations. The mutations in ATP6V1B2 and VMA21 through separate mechanisms impair lysosomal V-ATPase activity resulting in an elevated lysosomal pH. The elevated lysosomal pH impairs protein and peptide hydrolysis and associates with reduced cytoplasmic amino acid concentrations resulting in compensatory activation of autophagic flux. The elevated autophagic flux constitutes a survival dependency for FL cells and can be targeted with inhibitors to ULK1 and multiple recently identified cyclin-dependent kinase inhibitors. Targeting autophagy alone or in combination with other targeted therapies constitutes a novel therapeutic opportunity for FL patients.

Follicular lymphoma-associated mutations in the V-ATPase chaperone VMA21 activate autophagy creating a targetable dependency

The discovery of recurrent mutations in subunits and regulators of the vacuolar-type H⁺-translocating ATPase (V-ATPase) in follicular lymphoma (FL) highlights a role for macroautophagy/autophagy, amino-acid, and nutrient-sensing pathways in the pathogenesis of this disease. Here, we report on novel mutations in the ER-resident chaperone VMA21, which is involved in V-ATPase assembly in 12% of FL. Mutations in a novel VMA21 hotspot (p.93X) result in the removal of a C-terminal non-canonical ER retrieval signal thus causing VMA21 mislocalization to lysosomes. The resulting impairment in V-ATPase activity prevents full lysosomal acidification and function, including impaired pH-dependent protein degradation as shown via lysosomal metabolomics and ultimately causes a degree of amino acid depletion in the cytoplasm. These deficiencies result in compensatory autophagy activation, as measured using multiple complementary assays in human and yeast cells. Of translational significance, the compensatory activation of autophagy creates a dependency for survival for VMA21-mutated primary human FL as shown using inhibitors to ULK1, the proximal autophagy-regulating kinase. Using high-throughput microscopy-based screening assays for autophagy-inhibiting compounds, we identify multiple clinical grade cyclin-dependent kinase inhibitors as promising drugs and thus provide new rationale for innovative clinical trials in FL harboring aberrant V-ATPase.Abbreviations: ALs: autolysosomes; APs: autophagosomes; ER: endoplasmic reticulum; FL: follicular lymphoma; GFP: green fluorescent protein; IP: immunoprecipitation; LE/LY: late endosomes/lysosomes; Lyso-IP: lysosomal immunoprecipitation; OST: oligosaccharide transferase; prApe1: precursor aminopeptidase I; SEP: super ecliptic pHluorin; V-ATPase: vacuolar-type H⁺-translocating ATPase.

DC-SIGN binding to mannosylated B-cell receptors in follicular lymphoma down-modulates receptor signaling capacity

In follicular lymphoma (FL), surface immunoglobulin (sIg) carries mandatory N-glycosylation sites in the variable regions, inserted during somatic hypermutation. These glycosylation sites are tumor-specific, indicating a critical function in FL. Added glycan unexpectedly terminates at high mannose (Mann) and confers capability for sIg-mediated interaction with local macrophage-expressed DC-SIGN lectin resulting in low-level activation of upstream B-cell receptor signaling responses. Here we show that despite being of low-level, DC-SIGN induces a similar downstream transcriptional response to anti-IgM in primary FL cells, characterized by activation of pathways associated with B-cell survival, proliferation and cell-cell communication. Lectin binding was also able to engage post-transcriptional receptor cross-talk pathways since, like anti-IgM, DC-SIGN down-modulated cell surface expression of CXCR4. Importantly, pre-exposure of a FL-derived cell line expressing sIgM-Mann or primary FL cells to DC-SIGN, which does not block anti-IgM binding, reversibly paralyzed the subsequent Ca2+ response to anti-IgM. These novel findings indicate that modulation of sIg function occurs in FL via lectin binding to acquired mannoses. The B-cell receptor alternative engagement described here provides two advantages to lymphoma cells: (i) activation of signaling, which, albeit of low-level, is sufficient to trigger canonical lymphoma-promoting responses, and (ii) protection from exogenous antigen by paralyzing anti-IgM-induced signaling. Blockade of this alternative engagement could offer a new therapeutic strategy.

Frequent loss of CD10 expression in follicular lymphoma with leukaemic presentation

INTRODUCTION

Follicular lymphoma (FL) is usually a nodal lymphoma expressing CD10, rarely with leukaemic presentation (FL-LP).

MATERIALS AND METHODS

We searched for FL-LP in our institution from 2000 to 2018 and characterised the neoplastic cells by flow cytometry, immunohistochemistry and fluorescence in situ hybridization. Thirteen (6.1%) of 212 FL cases were FL-LP, all de novo neoplasms. The leukaemic cells were small in 12 cases and large in one. All had concurrent FL, mostly (92%; 12/13) low-grade. The single case with large leukaemic cells had a concurrent primary splenic low-grade FL and a double-hit large B-cell lymphoma in the marrow.

RESULTS

CD10 was expressed in the leukaemic cells in 38% (5/13) cases by flow cytometry and in 77% (10/13) cases in tumours (p= 0.0471). IGH/BCL2 reciprocal translocation was identified in 85% (11/13) cases. Most patients were treated with chemotherapy. In a median follow-up time of 36 months, nine patients were in complete remission. The 2- and 5-year survival rates were at 100% and 83%, respectively. In this study, we characterised a series of de novo FL-LP in Taiwan. All patients had concurrent nodal and/or tissue tumours, which might suggest that these patients seek medical help too late.

CONCLUSION

The lower CD10 expression rate by flow cytometry than by immunohistochemistry might be due to different epitopes for these assays. Alternatively, loss of CD10 expression might play a role in the pathogenesis of leukaemic change. The clinical course of FL-LP could be aggressive, but a significant proportion of the patients obtained complete remission with chemotherapy.

The Biological Basis of Histologic Transformation

Histologic transformation of follicular lymphoma remains the leading cause of follicular lymphoma-related mortality in the rituximab era. Both the diverse timing of transformation and heterogeneity in associated genomic events suggest that histologic transformation may itself comprise distinct disease entities. Successive indolent and transformation episodes occur by divergent clonal evolution from an inferred common progenitor cell, representing a potential therapeutic target. Existing biological knowledge largely pre-dates anti-CD20 therapy, and further prospective validation is essential. Inclusion of transformation cases in clinical trials incorporating biomarker discovery, and an integrated understanding of the genetic and microenvironmental factors underpinning transformation, may unearth renewed clinical opportunities.

PD1 distribution pattern, regardless of the cell origin, is an independent microenvironmental prognostic factor for progression-free survival in follicular lymphoma

Follicular lymphoma (FL) is a well-studied microenvironment-dependent hematological malignancy, but the crosstalk between various involved cell subtypes is still not fully understood. Recent promising results of immunotherapy in recurrent FL warrant the need for an in-depth analysis of the expression and role of immune system-related proteins in the FL microenvironment. Seventy-one patients with FL and available diagnostic paraffin blocks were enrolled in the retrospective analysis. Histopathological diagnoses were revised according to the World Health Organization recommendations. Patients were either observed (watch and wait/W&W group) or immediately treated with chemo(immuno)therapy regimens according to their clinical status. Immunohistochemical assessment of PD1, PDL1, CD4, CD8, CD163, CD68-KP1, CD68-PGM1 was performed. The scoring methods included both semi-quantitative estimation of positive cells and architectural pattern distribution. The differences between PD1 staining distribution and intensity were classified as intra/perifollicular vs. interfollicular/diffuse cells and presented bright vs. dim immunoreactivity, respectively. No statistically significant differences in the density distribution of the immunohistochemical stainings were found between W&W and chemo(immuno)therapy groups. Interfollicular/diffuse pattern of PD1 expression had significantly decreased progression-free survival when analyzing the whole cohort and patients on chemo(immuno)therapy (p = 0.014 and p = 0.07, respectively). The high dependence was not significant in the W&W group. PD1 positivity of cells did not correlate with CD4 or CD8 immunophenotype. Morphologically FL neoplastic cells were entirely PDL1 negative, but granular and membranous staining was detected in the FL microenvironment. In line with previous studies, PD1/PDL1 expression was predominantly localized in the FL microenvironment, indicating that FL cells might not be the direct target for anti-PDL1 therapy. However, we show that the localization of PD1 expression could be a viable progression-free survival biomarker for FL.

Lipid Trait Variants and the Risk of Non-Hodgkin Lymphoma Subtypes: A Mendelian Randomization Study

BACKGROUND

Lipid traits have been inconsistently linked to risk of non-Hodgkin lymphoma (NHL). We examined the association of genetically predicted lipid traits with risk of diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), and marginal zone lymphoma (MZL) using Mendelian randomization (MR) analysis.

METHODS

Genome-wide association study data from the InterLymph Consortium were available for 2,661 DLBCLs, 2,179 CLLs, 2,142 FLs, 824 MZLs, and 6,221 controls. SNPs associated (P < 5 × 10-8) with high-density lipoprotein (HDL, n = 164), low-density lipoprotein (LDL, n = 137), total cholesterol (TC, n = 161), and triglycerides (TG, n = 123) were used as instrumental variables (IV), explaining 14.6%, 27.7%, 16.8%, and 12.8% of phenotypic variation, respectively. Associations between each lipid trait and NHL subtype were calculated using the MR inverse variance-weighted method, estimating odds ratios (OR) per standard deviation and 95% confidence intervals (CI).

RESULTS

HDL was positively associated with DLBCL (OR = 1.14; 95% CI, 1.00-1.30) and MZL (OR = 1.09; 95% CI, 1.01-1.18), while TG was inversely associated with MZL risk (OR = 0.90; 95% CI, 0.83-0.99), all at nominal significance (P < 0.05). A positive trend was observed for HDL with FL risk (OR = 1.08; 95% CI, 0.99-1.19; P = 0.087). No associations were noteworthy after adjusting for multiple testing.

CONCLUSIONS

We did not find evidence of a clear or strong association of these lipid traits with the most common NHL subtypes. While these IVs have been previously linked to other cancers, our findings do not support any causal associations with these NHL subtypes.

IMPACT

Our results suggest that prior reported inverse associations of lipid traits are not likely to be causal and could represent reverse causality or confounding.

IGHV sequencing reveals acquired N-glycosylation sites as a clonal and stable event during follicular lymphoma evolution

Follicular lymphoma B cells undergo continuous somatic hypermutation (SHM) of their immunoglobulin variable region genes, generating a heterogeneous tumor population. SHM introduces DNA sequences encoding N-glycosylation sites asparagine-X-serine/threonine (N-gly sites) within the V-region that are rarely found in normal B-cell counterparts. Unique attached oligomannoses activate B-cell receptor signaling pathways after engagement with calcium-dependent lectins expressed by tissue macrophages. This novel interaction appears critical for tumor growth and survival. To elucidate the significance of N-gly site presence and loss during ongoing SHM, we tracked site behavior during tumor evolution and progression in a diverse group of patients through next-generation sequencing. A hierarchy of subclones was visualized through lineage trees based on SHM semblance between subclones and their discordance from the germline sequence. We observed conservation of N-gly sites in more than 96% of subclone populations within and across diagnostic, progression, and transformation events. Rare N-gly-negative subclones were lost or negligible from successive events, in contrast to N-gly-positive subclones, which could additionally migrate between anatomical sites. Ongoing SHM of the N-gly sites resulted in subclones with different amino acid compositions across disease events, yet the vast majority of resulting DNA sequences still encoded for an N-gly site. The selection and expansion of only N-gly-positive subclones is evidence of the tumor cells' dependence on sites, despite the changing genomic complexity as the disease progresses. N-gly sites were gained in the earliest identified lymphoma cells, indicating they are an early and stable event of pathogenesis. Targeting the inferred mannose-lectin interaction holds therapeutic promise.

High-Throughput Platform for B-Cell Screening Based on Fluorescent Phage-Display Technology

A system for detection of malignantly transformed cells, including follicular lymphoma Bcells, was developed and experimentally validated. The system is based on the use of bacteriophages carrying exposed ligands for pathogenic B-cell receptors. The efficiency of binding to target cells is several times higher than in systems with chemically synthesized biotinylated peptides. The new method is proposed as a noninvasive diagnostic test for mapping B-cell lymphoma and for determining the specificity of B-cell receptors and high-throughput combinatorial selection of various repertories of B cells.

Clinicopathological characteristics of diffuse large B-cell lymphoma involving small and large intestines: an analysis of 126 patients

We analyzed the clinicopathologic characteristics of 136 intestinal diffuse large B-cell lymphomas (DLBCLs) among 126 patients. The DLBCL sites were categorized as: duodenum (n = 23), ileocecal region (n = 63), other small intestine (n = 29), rectum (n = 7), and other large intestine (n = 14). Patients with DLBCLs of the ileocecal region or other small intestine frequently underwent surgery for ileus or perforations (P < 0.001), were predominantly male (P = 0.042), and had a higher incidence of limited-stage disease (P = 0.001), lower International Prognostic Index (P = 0.015), and lower incidence of lactate dehydrogenase elevation (P = 0.007) than those with DLBCLs of other regions. Half of the intestinal DLBCLs exhibited the germinal center B-cell phenotype. A low-grade B-cell lymphoma background was found in 21% of the cases; the prevalence was significantly lower in the ileocecal region (13%, P = 0.025), suggesting a higher incidence of de novo DLBCLs. Intestinal follicular lymphoma (FL) and mucosa-associated lymphoid tissue (MALT) lymphoma backgrounds were observed in 10% and 0% of the cases, respectively. Five percent (5/107) of intestinal DLBCL cases were Epstein-Barr virus-encoded RNA-1 positive. The clinicopathologic characteristics of the DLBCLs differed by region. Histologic transformation of intestinal FL was observed in around 10% of the intestinal DLBCL cases.

Unraveling transformation of follicular lymphoma to diffuse large B-cell lymphoma

Follicular lymphoma (FL) is an indolent but largely incurable disease. Some patients suffer histological transformation to a more aggressive subtype with poorer prognosis. This study aimed to improve our understanding of the genetics underlying FL histological transformation, and to identify genetic drivers or promoters of the transformation by elucidating the differences between FL samples from patients who did and did not transform. We conducted targeted massive parallel sequencing of 22 pre-transformed FL/transformed diffuse large B-cell lymphoma pairs and 20 diagnostic samples from non-transformed FL patients. Additionally, 22 matched samples from 11 transformed FL patients (pre-transformed FL and diffuse large B-cell lymphoma) and 9 non-transformed FLs were studied for copy number variation using SNP arrays. We identified recurrently mutated genes that were enriched at transformation, most notably LRP1B, GNA13 and POU2AF1, which have roles in B-cell differentiation, GC architecture and migration. Mutations in POU2AF1 might be associated with lower levels of expression, were more frequent in transformed FLs, and seemed to be specific to transformed- compared with de novo-diffuse large B-cell lymphomas. Pre-transformed FLs carried more mutations per sample and had greater subclonal heterogeneity than non-transformed FLs. Finally, we identified four mutated genes in FL samples that differed between patients who did and did not transform: NOTCH2, DTX1, UBE2A and HIST1H1E. The presence of mutations in these genes was associated with shorter time to transformation when mutated in the FL biopsies. This information might be useful for identifying patients at higher risk of transformation.

Management of adverse events associated with idelalisib treatment in chronic lymphocytic leukemia and follicular lymphoma: A multidisciplinary position paper

The introduction of new therapeutic agents in chronic lymphocytic leukemia (CLL) and follicular lymphoma (FL), including the new kinase inhibitor idelalisib, has changed the therapeutic landscape of these diseases. However, the use of idelalisib is associated with a peculiar profile of side effects, which require an optimization of the current approach to prophylaxis and supportive treatment. Moving from the recognition that the abovementioned issue represents an unmet need in CLL and FL, a multidisciplinary panel of experts was convened to produce a consensus document aiming to provide practical recommendations for the management of the side effects during idelalisib therapy for CLL and FL. The present publication represents a consensus document from a series of meetings held during 2017. The Panel generated clinical key questions using the criterion of clinical relevance through a Delphi process and explored 4 domains, ie, diarrhea/colitis, transaminitis, pneumonitis, and infectious complications. Using the consensus method, the Panel was able to shape recommendations which may assist hematologist to minimize adverse events and guarantee adherence to treatment in patients with CLL and FL candidate to receive idelalisib.

Colorectal follicular lymphoma: A case report

RATIONALE

Considering the low incidence of colorectal follicular lymphoma (FL) and its clinical features in endoscopic views, only a few studies have described the pathological diagnosis and treatment of this disease. This study aimed to reveal the overall process of clinical diagnosis and treatment of colorectal FL by conducting a case review.

PATIENT CONCERNS

A 27-year-old female presented to our department because of "severe bloody stool" lasting for more than 1 month. Her primary symptom was melena. Colonoscopy revealed widespread flat polyps with various immunophenotypes (CD10+, BCL2+, BCL6+, cyclin D1-, CD5-) in the colorectal area.

DIAGNOSIS

In accordance with manifestations on positron emission tomography-computed tomography (PET/CT), the patient was diagnosed with stage IV colorectal FL.

INTERVENTIONS

PET/CT reexamination after 2 courses of rituximab, cyclophosphamide, liposomal doxorubicin, vincristine sulfate, and hydroprednisone (R-CHOP) regimen and 3 courses of R-CHOP plus etoposide regimen for chemotherapy indicated a significant reduction in tumor burden. Subsequently, rituximab was administered alone in 2 treatment courses.

OUTCOMES

Lesions on PET/CT disappeared after reexamination. No recurrence was observed within the 12-month follow-up period.

LESSONS

Colorectal FL is a rare disease with an inert clinical course and is common in the ileocecal area. Endoscopic views show multiple polyps. Interventional treatment is usually provided after observation of clinical symptoms or during disease progression. The disease has a relatively good prognosis.

Efficacy, pharmacokinetics, and safety of the biosimilar CT-P10 in comparison with rituximab in patients with previously untreated low-tumour-burden follicular lymphoma: a randomised, double-blind, parallel-group, phase 3 trial

BACKGROUND

Studies in patients with rheumatoid arthritis and advanced follicular lymphoma have shown that CT-P10, a rituximab biosimilar, has equivalent or non-inferior efficacy and pharmacokinetics to rituximab. We aimed to assess the therapeutic equivalence of single-agent CT-P10 and rituximab in patients with newly diagnosed low-tumour burden follicular lymphoma.

METHODS

In this ongoing, randomised, double-blind, parallel-group, active-controlled, phase 3 trial, adult patients (≥18 years) with stage II-IV low-tumour-burden follicular lymphoma were randomly assigned (1:1) using an interactive web or voice response system stratified by region, stage, and age to CT-P10 or US-sourced rituximab. Patients received CT-P10 or rituximab (375 mg/m² intravenous) on day 1 of four 7-day cycles (induction period). Patients who had disease control after the induction period continued to a maintenance period of CT-P10 or rituximab administered every 8 weeks for six cycles and, if completed, a second year of maintenance therapy of additional CT-P10 (every 8 weeks for six cycles) was offered. The study was partially unmasked after database lock (Feb 23, 2018) for all data up to 7 months (before cycle 3 of the maintenance period). The primary endpoint was the proportion of patients who achieved an overall response by 7 months in the intention-to-treat population. Efficacy equivalence was shown if the two-sided 90% CIs for the treatment difference in the proportion of responders between CT-P10 and rituximab was within the equivalence margin of 17%. This trial is registered with ClinicalTrials.gov, number NCT02260804.

FINDINGS

Between Nov 9, 2015, and Jan 4, 2018, 402 patients were assessed for eligibility, of whom 258 were randomly assigned: 130 to CT-P10 and 128 to rituximab. 108 (83%) of 130 patients assigned to CT-P10 and 104 (81%) of 128 assigned to rituximab achieved an overall response by month 7 (treatment difference estimate 1·8%; 90% CI -6·43 to 10·20). Therapeutic equivalence was shown (90% CIs were within the prespecified margin of 17%). The most common grade 3 or 4 treatment-emergent adverse events were decreased neutrophil count (two grade 3 in the CT-P10 group) and neutropenia (one in each group); all other grade 3 or 4 treatment-emergent adverse events occurred in one patient each. Six (5%) of 130 patients who received CT-P10 and three (2%) of 128 who received rituximab experienced at least one treatment-emergent serious adverse event.

INTERPRETATION

CT-P10 was equivalent to rituximab in terms of efficacy and was well tolerated. CT-P10 monotherapy is suggested as a new therapeutic option for patients with low-tumour-burden follicular lymphoma.

FUNDING

Celltrion, Inc.

Sequencing of therapies in relapsed follicular lymphoma

Follicular lymphoma (FL) is an incurable but treatable disease with vast treatment options. Despite the abundance of efficacious treatment modalities, there is no universally agreed upon standard approach to treatment, particularly in the relapsed/refractory setting. There is an increasing need for more robust and clinically available tools to risk-stratify patients and identify those likely to experience early relapse, which is currently recognized as the unmet need in FL. Additionally, the use of gene-expression profiling and next-generation sequencing techniques in recent years has led to a wealth of knowledge regarding the molecular drivers of lymphomagenesis. However, much of this knowledge is not currently available in the clinic to inform treatment decisions. Future studies are needed to generate clinically relevant predictive models adept at incorporating patient-specific and molecular features to inform management strategies along the entire disease continuum as treatment decisions should not be made in a vacuum with a one-size-fits-all approach. Sequencing of therapy in the management of relapsed FL should involve personalized decision-making for care plans that balance patient characteristics, preferences, and comorbidities with treatment-related factors such as efficacy, toxicity profile, and mechanisms of action to achieve a durable, quality remission.

Transformation of double-hit follicular lymphoma to plasmablastic lymphoma: a partial role of MYC gene rearrangement

Follicular lymphoma (FL) is genetically characterized by BCL2/IGH translocation. Some FL cases histologically transform to high-grade lymphoma, and the majority of cases transform to diffuse large B-cell lymphoma. We report herein an unusual FL case that transformed to plasmablastic lymphoma (PBL) with MYC gene rearrangement as early as 12 months after FL diagnosis. IGH/MYC translocation, the most common cytogenetic abnormality seen in de novo PBL, was also detected in the transformed tumor (double-hit lymphoma). The patient became resistant to chemotherapy and died 4 months after transformation. We speculate that the “second hit” of MYC rearrangement played a crucial role in PBL transformation (PBL-T) in this case. Highly specific three-color FISH analysis demonstrated the presence of BCL2/IGH/MYC triple fusion signals on a single chromosome as we expected, but BCL2/IGH and IGH/MYC fusion signals also coexisted in a single nucleus. The PBL-T tumor was genetically heterogeneous, despite being histologically quite homogeneous PBL. Surprisingly, three-color FISH analysis revealed that the preceding FL tumor was also genetically heterogeneous, simultaneously harboring BCL2/IGH, IGH/MYC and BCL2/IGH/MYC fusion signals (i.e. double-hit lymphoma), despite being histologically quite homogeneous FL. This suggests that MYC rearrangement played a partial role in PBL-T. Genetic instability including MYC rearrangement in the preceding FL tumor would contribute to PBL-T and poor outcome in this case. This study will broaden our understanding of the pathogenesis of high-grade transformation of FL and help improve patient outcome.

Diffuse Large B Cell Lymphoma Coexistent with Follicular Cell Lymphoma

BACKGROUND

Diffuse large B cell lymphoma (DLBCL) and follicular cell lymphoma (FL) synchronously occurring in the same individual is unusual. The authors describe a rare case of DLBCL coexisting with FL at diagnosis in a male patient, with intestinal and lymph node involvement.

METHODS

Hematologic investigation, intestinal tumor biopsy, bone marrow examination, cytogenetic analysis, and PCR were performed.

RESULTS

The patient received three courses of R-CHOP regimen chemotherapy, the mesentery lymph nodes were reduced to 2.7 x 1.4 cm compared to 5.4 x 5.0 cm at diagnosis. However, the mesentery lymph nodes were increased to 4.7 x 3.5 cm after four additional courses R-CHOP treatment. Unfortunately, the patient refused chemotherapy treatment or hematopoietic stem cell transplantation (HSCT) and was lost to follow-up.

CONCLUSIONS

The presence of DLBCL coexisting with FL at diagnosis is rare and has generally been the subject of isolated case reports. Further studies are required to better understand the biological insights of the disease and to propose an optimal management strategy for this type of lymphoma.

Reduced lymphotoxin-beta production by tumour cells is associated with loss of follicular dendritic cell phenotype and diffuse growth in follicular lymphoma

Cytokine production is essential for follicular dendritic cell (FDC) maintenance and organization of germinal centres. In follicular lymphoma, FDCs are often disarrayed and may lack antigens indicative of terminal differentiation. We investigated the in situ distribution of cells producing lymphotoxin‐beta (LTB), lymphotoxin‐alpha (LTA), and tumour necrosis factor‐alpha (TNFA) transcripts in human reactive lymph nodes and in follicular lymphomas with follicular or diffuse growth pattern. LTB was the cytokine most abundantly produced in germinal centres. LTB was present in nearly 90% of germinal centre cells whereas LTA and TNFA were detected in 30 and 50%, respectively. Moreover, the amount of LTB expressed in reactive germinal centre cells was 80‐fold higher than that of LTA and 20‐fold higher than that of TNFA. LTB‐positive cells were more numerous in the germinal centre dark zone, whereas expression of the FDC proteins CD21, CD23, VCAM, and CXCL13 was more intense in the light zone. Tumour cells of follicular lymphomas produced less LTB than reactive germinal centre cells. The results of the in situ study were confirmed by RT‐PCR; LTB was significantly more abundant in reactive lymph nodes than in follicular lymphoma, with the lowest values detected in predominantly diffuse follicular lymphoma. In neoplastic follicles, low production of LTB by tumour B cells was associated with weaker expression of CD21+/CD23+ by FDCs. Our findings detail for the first time the distribution of LTA‐, LTB‐, and TNFA‐producing cells in human reactive germinal centres and in follicular lymphoma. They suggest the possibility that impaired tumour‐cell LTB production may represent a determinant of FDC phenotype loss and for defective follicular organization in follicular lymphoma.

Bendamustine plus Rituximab Versus R-CHOP as First-Line Treatment for Patients with Follicular Lymphoma Grade 3A: Evidence from a Multicenter, Retrospective Study

BACKGROUND

Rituximab plus bendamustine (R-B) has been demonstrated to improve outcomes and reduce toxicity compared with rituximab, cyclophosphamide, doxorubicin, and prednisone (R-CHOP) in follicular lymphoma (FL). Nevertheless, in clinical practice, many centers still prefer R-CHOP to R-B in patients with FL grade 3A (FL3A). Therefore, we retrospectively assessed patients with FL3A treated with either R-CHOP or R-B in five European cancer centers and compared their outcomes.

MATERIALS AND METHODS

We retrospectively assessed 132 patients affected by FL grade 3A treated with either R-B or R-CHOP in the first line and evaluated outcome and toxicity according to the type of treatment. This study included 101 patients who were a subgroup of a previously published cohort.

RESULTS

R-B was less toxic and achieved a similar percentage of complete remissions compared with R-CHOP (97% vs. 96%, p = .3). During follow-up, 10 (16%) patients relapsed after R-B and 29 (41%) after R-CHOP (p = .001), leading to a median progression-free survival (PFS) of 15 versus 11.7 years, respectively (p = .03). Furthermore, R-B overcame the negative prognostic impact of BCL2 expression (15 vs. 4.8 years; p = .001). However, median overall survival was similar between both groups (not reached for both; p = .8).

CONCLUSION

R-B as a first-line treatment of FL3A is better tolerated than R-CHOP and seems to induce more profound responses, leading to a significantly lower relapse rate and prolonged PFS. Therefore, R-B is a valid treatment option for FL grade 3A.

IMPLICATIONS FOR PRACTICE

Rituximab plus bendamustine (R-B) has shown to be less toxic and more effective than rituximab, cyclophosphamide, doxorubicin, and prednisone (R-CHOP) in follicular lymphoma grade 3A. Although both regimens can induce a complete remission in >95% of patients, relapses occur more frequently after R-CHOP than R-B, leading to a significantly longer progression-free survival in the latter. R-B is also able to overcome the impact of negative prognosticators, such as BCL2 expression. However, because of the indolent course of this disease and efficient salvage treatments, overall survival was similar in both treatment groups. Therefore, R-B is a valid treatment option in this patient setting.

Follicular lymphoma: are we ready for a risk-adapted approach?

Follicular lymphoma is the most common indolent non-Hodgkin lymphoma in the Western hemisphere. The natural history of FL appears to have been favorably impacted by the introduction of rituximab after randomized clinical trials demonstrated that the addition of rituximab to standard chemotherapy induction has improved the overall survival. Yet, the disease is biologically and clinically heterogeneous with wide variations in outcomes for individual patients. The ability to accurately risk-stratify patients and then tailor therapy to the individual is an area of ongoing research. Historically, tumor grade, tumor burden, and the FL international prognostic index (version 1 and version 2) have been used to distinguish low-risk from high-risk patients. Biologic factors such as mutations in key genes can identify patients at high risk for poor outcomes to first-line therapy (mutational status of 7 genes [EZH2, ARID1A, MEF2B, EP300, FOX01, CREBBP, and CARD11] with Follicular Lymphoma International Prognostic Index). More recently, the quality of the response to initial therapy, as measured by either PET imaging or by remission duration, has been show to identify individuals at high risk. However, several unmet needs remain, including a better ability to identify high-risk patients at diagnosis, the development of predictive biomarkers for targeted agents, and strategies to reduce the risk of transformation.

The routes for transformation of follicular lymphoma

PURPOSE OF REVIEW

Aggressive transformation, a frequent event in the natural history of follicular lymphoma, is associated with increased lymphoma-related mortality and yet the underlying biology remains poorly defined. This review outlines recent advances in our understanding of the genetic basis and evolutionary process leading to transformation.

RECENT FINDINGS

Both the antecedent indolent and transformed follicular lymphoma (tFL) arise through branched divergent evolution with tumors emerging from a founder precursor population, the common progenitor cell. Although the majority of tFLs maintain a germinal center B-cell gene expression signature, an activated B-cell-type (ABC-type) profile appears to predominate in BCL2-translocation negative cases. It does not appear that a single unifying genetic or epigenetic event promotes a fitter and more aggressive clone.

SUMMARY

Transformed follicular tumors are genetically heterogeneous perhaps reflecting the varying clinical behavior and outcomes of this disease event. Follicular lymphoma and tFL remain incurable tumors highlighted by our inability to eradicate the founder common progenitor cell population with current therapies. Progress has now been made in defining the genetic events and evolutionary pathways responsible for transformation. Although more research is required in predicting and understanding the biology of transformation, there are opportunities to improve outcomes by preferentially directing targeted therapies toward 'actionable' early and transformation-specific aberrations.

miR-31 and miR-17-5p levels change during transformation of follicular lymphoma

The 30% of patients whose indolent follicular lymphoma transforms to aggressive diffuse large B-cell lymphoma (DLBCL) have poor survival. Reliable predictors of follicular B-cell lymphoma transformation to DLBCL are lacking, and diagnosis of those that will progress is challenging. MicroRNA, which regulates gene expression, has critical functions in the growth and progression of many cancers and contributes to the pathogenesis of lymphoma. Using 5 paired samples from patients who presented with follicular lymphoma and progressed to DLBCL, we identified specific microRNA differentially expressed between the two. Specifically, miR-17-5p levels were low in follicular lymphoma and increased as the disease transformed. In contrast, miR-31 expression was high in follicular lymphoma and decreased as the lymphoma progressed. These results were confirmed in additional unpaired cases of low-grade follicular lymphoma (n = 13) and high-grade follicular lymphoma grade 3 or DLBCL (n = 17). Loss of miR-31 expression in DLBCL was not due to deletion of the locus. Changes in miR-17-5p and miR-31 were not correlated with immunophenotype, genetics, or status of the MYC oncogene. However, increased miR-17-5p expression did significantly correlate with increased expression of p53 protein, which is indicative of mutant TP53. Two pro-proliferative genes, E2F2 and PI3KC2A, were identified as direct messenger RNA targets of miR-31, suggesting that these may contribute to follicular lymphoma transformation. Our results indicate that changes in miR-31 and miR-17-5p reflect the transformation of follicular lymphoma to an aggressive large B-cell lymphoma and may, along with their targets, be viable markers for this process.

Aequorin as Intracellular Ca2+ Indicator Incorporated in Follicular Lymphoma Cells by Hypoosmotic Shock Treatment

Natural proteins can be used in measuring intracellular Ca(2+) concentration. As one of the Ca(2+)- regulated photoproteins, aequorin has several advantages in comparison to widely used Ca(2+) fluorescence indicators (e.g., fura-2, indo-1 and fluo-3), including high dynamic range and resistance to motion artefacts. However, incorporation of aequorin into cells remains a challenge. Hypoosmotic shock treatment was optimized and used as a method for loading aequorin into the cytoplasm of follicular lymphoma cells. Measurement of aequorin luminescence in the cells was performed using a luminometer with a sensitive photomultiplier tube and the luminescence intensity was recalculated into intracellular [Ca(2+)]. The value of (0.85 ± 0.52)·10-6 M was found. We show that the optimized method of incorporation was effective for loading aequorin into follicular lymphoma cells in vitro. The cell viability remains high immediately after the procedure. This method can also be used for measuring intracellular Ca(2+) concentration in other types of non-adherent cells.

Follicular lymphoma: too many reminders for a memory B cell

Memory B cells are a dynamic subset of the mature B cell population that in some cases can reenter germinal centers (GCs) in response to iterative infections. Such a reactivation can lead to accumulation of genetic lesions in these cells, potentially from repetitive activation of the B cell mutator enzyme AID. Normal memory B cells do not survive repeated reentries into GCs. In this issue, Sungalee et al. demonstrate that memory B cells harboring the oncogenic BCL2:IGH translocation, which results in constitutive BCL2 expression, survive multiple GC entries upon repetitive immunization. Through these multiple GC reentries, the hallmark BCL2:IGH translocation enables AID-induced hypermutation and propagates clonal evolution toward malignant follicular lymphoma.

Germinal center reentries of BCL2-overexpressing B cells drive follicular lymphoma progression

It has recently been demonstrated that memory B cells can reenter and reengage germinal center (GC) reactions, opening the possibility that multi-hit lymphomagenesis gradually occurs throughout life during successive immunological challenges. Here, we investigated this scenario in follicular lymphoma (FL), an indolent GC-derived malignancy. We developed a mouse model that recapitulates the FL hallmark t(14;18) translocation, which results in constitutive activation of antiapoptotic protein B cell lymphoma 2 (BCL2) in a subset of B cells, and applied a combination of molecular and immunofluorescence approaches to track normal and t(14;18)(+) memory B cells in human and BCL2-overexpressing B cells in murine lymphoid tissues. BCL2-overexpressing B cells required multiple GC transits before acquiring FL-associated developmental arrest and presenting as GC B cells with constitutive activation-induced cytidine deaminase (AID) mutator activity. Moreover, multiple reentries into the GC were necessary for the progression to advanced precursor stages of FL. Together, our results demonstrate that protracted subversion of immune dynamics contributes to early dissemination and progression of t(14;18)(+) precursors and shapes the systemic presentation of FL patients.

A case of t(14; 18)-negative follicular lymphoma with atypical immunophenotype: usefulness of immunoarchitecture of Ki67, CD79a and follicular dendritic cell meshwork in making the diagnosis

Follicular lymphoma is characterised by the t(14;18)(q32;q21) chromosomal translocation causing BCL2 protein overexpression. A proportion of follicular lymphomas do not carry the t(14;18) translocation and lacked BCL2 protein expression. We describe a case of a BCL2 protein- and t(14;18)-negative follicular lymphoma that caused diagnostic difficulty. The usefulness of several immunomarkers including Ki67, CD79a and CD21 in aiding the diagnosis is discussed. The patient is a 51-year-old male who presented with gradually enlarging lymphadenopathy. Histopathological examination of the lymph node showed complete architectural effacement by neoplastic follicles containing expanded CD21-positive follicular dendritic cell meshwork. The neoplastic cells expressed pan-B cell markers (CD20, CD79a) and germinal centre marker (BCL6) but not BCL2 and CD10. Of interest are the staining patterns of Ki67 and CD79a. We observed that the Ki67- positive proliferating cells were evenly distributed within the neoplastic follicles without zonation. In addition, CD79a was homogeneously strong within the neoplastic follicles. These staining patterns were distinctly different from that observed in reactive lymphoid follicles. Fluorescent insitu hybridisation (FISH) analysis however showed absence of BCL2 gene rearrangement. Despite the atypical immunophenotype and lack of BCL2 gene rearrangement, the diagnosis of follicular lymphoma was made based on careful observation of the morphology as well as immunoarchitecture of the Ki67, CD79a and CD21 markers.

Targetome profiling and functional genetics implicate miR-618 in lymphomagenesis

Despite the voluminous body of observational evidence concerning the role of miRNAs in cancer, significant knowledge gaps remain concerning the molecular circumstances that underlie the miRNA-cancer connection. In this study, we employ a multidisciplinary approach to establish an association between miR-618 and non-Hodgkin lymphoma (NHL) in a human population and attempt to explicate this association at the molecular level. A high-throughput, transcriptome-wide RIP-Chip-based method was used to identify members of the miR-618 targetome, which were analyzed for functional relevance using a gene network-based approach. Findings were confirmed by genotyping a SNP (rs2682818) in the stem-loop sequence of miR-618 in a population-based case-control study of NHL (455 cases and 527 controls). Lastly, we analyzed the functional impact of rs2682818 on miR-618 expression and its consequent implications for the lymphomagenic process. A total of 128 miR-618 targets were identified, which were enriched for genes that have functional roles in lymphoma-relevant pathways. This is consistent with our finding of a significant association between rs2682818 G>T in the miR-618 stem-loop and follicular lymphoma (FL) (OR: 1.65, 95% CI: 1.05-2.60). In vitro analysis of rs2682818's functional impact revealed that the variant T allele resulted in reduced levels of mature miR-618, which in turn may lead to deregulation of miR-618-controlled pathways relevant to follicular lymphoma. Taken together, our findings implicate miR-618 in follicular lymphomagenesis, identify miR-618 as a potential risk biomarker for follicular lymphoma, and illuminate miR-618-regulated lymphomagenic pathways that can serve as therapeutic targets for follicular lymphoma.

PLK1 and YY1 interaction in follicular lymphoma is associated with unfavourable outcome

AIMS

Ying Yang 1 (YY1) is a transcription factor involved in both proliferation and apoptosis. It is prognostic in follicular lymphoma (FL), increased protein levels being associated with favourable outcome. PLK1 is a critical regulator of mitosis, playing a role in spindle formation and in regulation of the G2/M cell cycle checkpoint. PLK1 phosphorylates YY1 at the G2/M checkpoint with activation of YY1 and resultant progression from G2 into mitosis.

METHODS

This study aims to investigate possible molecular coexpression and interaction of YY1 with PLK1 in FL using Duolink II in situ proximity ligation assay (PLA) in 51 FL samples in a tissue microarray.

RESULTS

Positive PLA signals were present at variable frequency and Kaplan-Meier analysis showed association of signal frequency above the median with unfavourable outcome (p=0.0270). PLA signals were localised to the nuclear edge, with only one signal per cell, suggesting PLK1 and YY1 coexpression at the centrosome. In a minority of cells, two very close PLA signals were present in a single cell, and occasionally, there was a strong ring of semi-confluent fluorescent PLA signals round the nucleus of non-dividing cells, while rarely events were observed in the cytoplasm surrounding dividing cells.

CONCLUSIONS

The results confirm association of YY1 and PLK1 with outcome in FL and suggest coexpression at the centrosome. Given the reported interaction of YY1 with PLK1 at the centriole and promotion of cell division at the G2/M checkpoint, the results would concord with the known association of higher proliferation with poor outcome in FL.

Coding variants at hexa-allelic amino acid 13 of HLA-DRB1 explain independent SNP associations with follicular lymphoma risk

Non-Hodgkin lymphoma represents a diverse group of blood malignancies, of which follicular lymphoma (FL) is a common subtype. Previous genome-wide association studies (GWASs) have identified in the human leukocyte antigen (HLA) class II region multiple independent SNPs that are significantly associated with FL risk. To dissect these signals and determine whether coding variants in HLA genes are responsible for the associations, we conducted imputation, HLA typing, and sequencing in three independent populations for a total of 689 cases and 2,446 controls. We identified a hexa-allelic amino acid polymorphism at position 13 of the HLA-DR beta chain that showed the strongest association with FL within the major histocompatibility complex (MHC) region (multiallelic p = 2.3 × 10⁻¹⁵). Out of six possible amino acids that occurred at that position within the population, we classified two as high risk (Tyr and Phe), two as low risk (Ser and Arg), and two as moderate risk (His and Gly). There was a 4.2-fold difference in risk (95% confidence interval = 2.9-6.1) between subjects carrying two alleles encoding high-risk amino acids and those carrying two alleles encoding low-risk amino acids (p = 1.01 × 10⁻¹⁴). This coding variant might explain the complex SNP associations identified by GWASs and suggests a common HLA-DR antigen-driven mechanism for the pathogenesis of FL and rheumatoid arthritis.

Selective inhibitors of nuclear export for the treatment of non-Hodgkin's lymphomas

The nuclear export protein chromosome maintenance region 1, found to be elevated in non-Hodgkin's lymphomas, controls localization of critical tumor suppressor proteins. Nuclear localization of tumor suppressor proteins is necessary for their cell surveillance function. However, their nuclear exclusion by chromosome maintenance region 1 renders them ineffective making this nuclear transporter an attractive therapeutic target. We have identified selective inhibitors of nuclear export that lock tumor suppressor proteins in the cell nucleus leading to apoptosis of lymphoid but not normal cells. Our inhibitors induce tumor suppressor protein nuclear retention-dependent growth inhibition and apoptosis in a panel of non-Hodgkin's lymphoma cell lines. Western blot of nuclear protein fraction and confocal microscopy analysis demonstrated retention of major tumor suppressor proteins in the cell nucleus. Co-immunoprecipitation studies showed disruption of the tumor suppressor protein-chromosome maintenance region 1 interaction. Small inhibitor RNA knockdown of two major tumor suppressor proteins, p53 in wild-type protein-53 and protein 73 in mutant-protein-53, abrogated inhibitor activity. Oral administration of related inhibitor at 75 and 150 mg/kg resulted in 65 and 70% tumor reduction, respectively and subcutaneous injections of inhibitor (25 and 75 mg/kg) resulted in 70 and 74% suppression of non-Hodgkin's lymphoma tumor growth with no toxicity; residual tumors showed activation of the protein 73 pathway. Our study verifies chromosome maintenance region 1 as a therapeutic target in non-Hodgkin's lymphoma, indicating that this nuclear export protein warrants further clinical investigations.

The BCL2 E17 and SP66 antibodies discriminate 2 immunophenotypically and genetically distinct subgroups of conventionally BCL2-"negative" grade 1/2 follicular lymphomas

Follicular lymphoma (FL) is characterized by the translocation t(14;18)(q32;q21) resulting in constitutive overexpression of BCL2. However, in 10% to 15% of FL grade 1/2, immunohistochemical staining for BCL2 remains negative. To analyze the incidence of BCL2 negativity and the underlying molecular mechanisms in FL grade 1/2, BCL2 expression was investigated with 3 antibodies (clones 100D5, E17, SP66). The presence of a break in the BCL2 locus was determined by fluorescence in situ hybridization. The region of the BCL2 gene where the epitope of the standard BCL2 antibody resides was sequenced. Twenty-two (9.2%) of 240 identified cases of FL grade 1/2 were negative with the standard BCL2 antibody. Of these, 12 cases (55%) carried a break in the BCL2 gene locus, which, in all but one case, correlated with BCL2 expression using the alternative antibodies E17 and SP66 and with missense mutations of BCL2. Ten (45%) of the 22 cases had an intact BCL2 gene locus; 2 cases carried a BCL6/IGH translocation. All 10 cases were negative for the E17/SP66 antibodies and showed a wild-type sequence of BCL2. Six of these showed an aberrant phenotype, with CD10 negativity (30%) or CD23 expression (30%). In summary, the alternative E17/SP66 antibodies identify 2 immunohistochemically and genetically distinct subgroups of BCL2-"negative" FL grade 1/2.

Double-hit and triple-hit lymphomas arising from follicular lymphoma following acquisition of MYC: report of two cases and literature review

Double-hit or triple-hit B-cell lymphomas (DHL and THL) are rare subtype lymphomas usually associated with poor prognosis. It is defined by two or three recurrent chromosome translocations; MYC/8q24 loci, usually in combination with the t (14; 18) (q32; q21) bcl-2 gene or/and BCL6/3q27 chromosomal translocation. DHL was often observed both in de-novo diffuse large B cell lymphomas (DLBCL). It is otherwise unclassifiable, showing features intermediate that of large B-cell lymphoma and Burkitt lymphoma. Here, we present two follicular lymphoma patients; one transformed to THL, another transformed to DHL. Both cases revealed aggressive clinical courses with poor prognosis and associated with acquisition of c-Myc gene (MYC) and central nervous system (CNS) involvement. We reviewed the related literature, correlated the immunophenotype and clinical manifestations such as response to therapy and prognosis. Although the incidence of DHT and THL is low, cytogenetic and FISH analyses should be included when B-cell lymphoma patients experience relapse or refractory course of disease. We concluded that c-Myc may contribute to aggressive transformation, and more mechanism-based therapy should be explored.

Aberration in DNA methylation in B-cell lymphomas has a complex origin and increases with disease severity

Despite mounting evidence that epigenetic abnormalities play a key role in cancer biology, their contributions to the malignant phenotype remain poorly understood. Here we studied genome-wide DNA methylation in normal B-cell populations and subtypes of B-cell non-Hodgkin lymphoma: follicular lymphoma and diffuse large B-cell lymphomas. These lymphomas display striking and progressive intra-tumor heterogeneity and also inter-patient heterogeneity in their cytosine methylation patterns. Epigenetic heterogeneity is initiated in normal germinal center B-cells, increases markedly with disease aggressiveness, and is associated with unfavorable clinical outcome. Moreover, patterns of abnormal methylation vary depending upon chromosomal regions, gene density and the status of neighboring genes. DNA methylation abnormalities arise via two distinct processes: i) lymphomagenic transcriptional regulators perturb promoter DNA methylation in a target gene-specific manner, and ii) aberrant epigenetic states tend to spread to neighboring promoters in the absence of CTCF insulator binding sites.

Follicular lymphomas and diffuse large B-cell lymphomas are the most common non-Hodgkin lymphomas. Although these diseases share many mutant alleles, the underlying cause of the different phenotypes remains unclear. We show that direct comparison of DNA methylation patterning provides insights about gene deregulation during lymphomagenesis and explains the nature of the different clinical behavior.

Dissecting follicular lymphoma: high versus low risk

Progress in the management of follicular lymphoma (FL) has translated to improved outcomes, with most patients surviving a decade or more from the time of diagnosis. However, the disease remains quite heterogeneous and a substantial number of patients have more aggressive disease with short responses to therapy and/or transformation to higher-grade lymphomas. Given the lack of a single standard approach, it is important to understand sources of heterogeneity among patients that influence initial management, surveillance strategies, and overall prognosis. Most of the validated tools, such as the Follicular Lymphoma International Prognostic Index (FLIPI) and FLIPI-2, apply to the frontline setting, and there is an unmet need for prognostic tools in relapsed and refractory disease states. In particular, the number of prior treatment regimens may be less important than the duration of response to the most recent regimen and the type of prior therapy received. Furthermore, despite awareness of progressive genetic and epigenetic derangements and a growing appreciation of the microenvironment's role in FL outcomes, there is no validated means of incorporating biologic data into clinical prognostic indices. This review highlights the current state of knowledge regarding risk stratification in FL.

Expression of BAFF and BAFF-R in follicular lymphoma: correlation with clinicopathologic characteristics and survival outcomes

BACKGROUND

B-cell activation factor (BAFF) and BAFF-receptor (BAFF-R) play crucial roles in the viability and proliferation of malignant lymphoma cells. Limited information exists regarding expression profiles and the prognostic role of BAFF and BAFF-R in follicular lymphoma (FL). We sought to determine the expression profiles of BAFF and BAFF-R in FL and to evaluate the correlation of BAFF and BAFF-R expression with clinicopathologic characteristics and outcome of FL. Correlation between expression levels of BAFF detected by immunohistochemical (IHC) and serum levels of BAFF was also evaluated.

METHODS

Paraffin-embedded specimens from 115 patients were immunohistochemically examined for BAFF and BAFF-R expression. Expression levels were dichotomized into low versus high categories based on immunostaining intensity. The correlation of BAFF and BAFF-R expression with clinicopathologic characteristics and patient outcome was assessed. Serum levels of BAFF in 35 of the 115 patients with IHC data were measured by Enzyme-linked Immunosorbent assay (ELISA).

RESULTS

BAFF and BAFF-R were expressed in 88.7% (102/115) and 87.8% (101/115) of the cases, respectively. BAFF expression was significantly correlated with only one clinicopathologic feature: Ann Arbor stage. No significant correlation was found between expression levels of BAFF detected by IHC and serum levels of BAFF detected by ELISA. High expression of BAFF-R, but not BAFF, was significantly correlated with inferior progression-free survival (PFS; P = 0.013) and overall survival (OS; P = 0.03). High expression of BAFF-R, bulky disease, and elevated lactate dehydrogenase were correlated with inferior PFS and OS in multivariate analysis. A prognostic scoring system incorporating these 3 risk factors identified 3 distinct prognostic groups with 5-year PFS of 59.4%, 41.9%, and 10.7% and OS of 91.3%, 79.7%, and 45.8%, respectively.

CONCLUSIONS

Most patients with FL variably express BAFF and BAFF-R. High expression of BAFF-R, but not BAFF, may be an independent risk factor for PFS and OS in FL.

Comparison of CD20 expression in B-cell lymphoma between newly diagnosed, untreated cases and those after rituximab treatment

Few studies have statistically investigated reduced CD20 expression in B-cell lymphoma after rituximab therapy and genomic mutation of CD20 associated with reduction. We examined CD20-positive rate in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) by flow cytometry (FCM) and immunohistochemical staining (IHS), comparing 138 cases after rituximab therapy with 360 initial, not yet treated cases. Sequence analysis of exons 3 to 8 of CD20 was performed on 22 cases with low CD20-positive rate after rituximab treatment. The results showed a statistical correlation between CD20-positive rate in FCM and IHS. By FCM, the CD20-positive rate among post-rituximab cases was significantly lower than among initial cases in DLBCL, non-germinal center origin B-cell type (average values [avg] 57.8 and 87.9, respectively) (P < 0.0001), FL2 (avg, 93.9; 103.2) (P = 0.0083), and FL3A (avg, 90.6; 100.7) (P = 0.033). Stratified analyses of post-rituximab cases showed significantly lower CD20-positive rate in cases that were resistant at the start of the treatment and cases with progressive disease during rituximab therapy before biopsy. Sequence analysis showed silent mutation of exon 4 (632 C/T) in seven cases, although this number was not statistically significant. These results suggest the influence of B-lymphoma subtype and a therapeutic effect before biopsy on CD20 expression at relapse and contribute to a better therapeutic approach for relapse cases after rituximab therapy.

The composition of the microenvironment in follicular lymphoma is associated with the stage of the disease

The role of regulatory and follicular helper T-cells as prognostic markers in follicular lymphoma was evaluated within the setting of prospective, randomized trials because the previously published results were contradictory. Two hundred sixty-four diagnostic tissue specimens from patients suffering from follicular lymphoma who received therapy within prospective randomized trials of the German Low Grade Lymphoma Study Group were analyzed immunohistochemically for FoxP3 and PD-1 expression to detect regulatory and follicular helper T-cells, respectively. We did not find any correlation between the content of regulatory and follicular helper T-cells and the time to treatment failure or overall survival in patients with advanced stages of follicular lymphoma in need of treatment. However, a perifollicular pattern of regulatory T-cells was associated with a poorer prognosis. The content of regulatory T-cells was positively and the content of follicular helper T-cells inversely correlated with a higher stage of the disease at diagnosis, implying that the microenvironment changes during tumor dissemination. This finding is independent of any therapy administered and needs to be considered when possible biomarkers related to the microenvironment of follicular lymphoma are studied.

A rare fraction of drug-resistant follicular lymphoma cancer stem cells interacts with follicular dendritic cells to maintain tumourigenic potential

Follicular lymphoma (FL) comprises nearly 25% of non-Hodgkin lymphoma cases and is clinically characterized by initial sensitivity to chemotherapy followed by relapse. FL stroma contains a special type of stromal cell found in the germinal centre of lymph nodes-the follicular dendritic cell (FDC). We first isolated tumourigenic cells from the FL cell line FLK-1 by side population (SP) technique, and found that SP cells, which express ABCG2, were enriched by chemotherapy and radiation treatments. In vitro, SP cells were attracted by and adhered to FDCs through chemokine (C-X-C motif) ligand 12/chemokine (C-X-C motif) receptor 4 (CXCL12/CXCR4) signalling. In vivo, limiting dilution assays showed SP cells were highly enriched in cancer stem cells (CSC), but required FDC for tumour formation in non-obese diabetic/severe combined immunodeficiency mice. Treatment with AMD3100, a specific CXCL12/CXCR4 inhibitor, eliminated tumour growth. These findings were then verified with FL cells isolated from an FL patient's ascitic fluid (FLA-1). Finally, we detected the ABCG2 expressing lymphoma cells in FL clinical specimens. Thus, we found that the highly tumourigenic FL cells having CSC-like activities (FL-SC) interact with FDCs in a CXCL12/CXCR4 dependent manner to resist chemotherapy. Our results indicate the importance of FL-SC and niche cell signalling in maintaining tumourigenicity. These signals represent novel targets for CSC eradication.

The Eph-receptor A7 is a soluble tumor suppressor for follicular lymphoma

Insights into cancer genetics can lead to therapeutic opportunities. By cross-referencing chromosomal changes with an unbiased genetic screen we identify the ephrin receptor A7 (EPHA7) as a tumor suppressor in follicular lymphoma (FL). EPHA7 is a target of 6q deletions and inactivated in 72% of FLs. Knockdown of EPHA7 drives lymphoma development in a murine FL model. In analogy to its physiological function in brain development, a soluble splice variant of EPHA7 (EPHA7(TR)) interferes with another Eph-receptor and blocks oncogenic signals in lymphoma cells. Consistent with this drug-like activity, administration of the purified EPHA7(TR) protein produces antitumor effects against xenografted human lymphomas. Further, by fusing EPHA7(TR) to the anti-CD20 antibody (rituximab) we can directly target this tumor suppressor to lymphomas in vivo. Our study attests to the power of combining descriptive tumor genomics with functional screens and reveals EPHA7(TR) as tumor suppressor with immediate therapeutic potential.

In situ follicular lymphoma associated with overt B- or T-cell lymphomas in the same lymph node

In situ follicular lymphoma (FL) is usually an incidental finding in otherwise reactive lymph node [1–3]. However, it may be associated with overt FL, or with lymphomas other than FL or with other malignancies,in other sites or, less commonly, in the same lymph node [2,4–8]. Here we describe two cases of in situ FL, one with concurrent overt FL(Case 1), and one with concurrent peripheral T-cell lymphoma (PTCL),NOS (Case 2) in the same lymph node. Immunohistochemistry, polymerase chain reaction for B and T-cell clonality, and double-staining chromogenic in situ hybridization for BCL2 translocation were performed.In both cases, the in situ FL foci were characterized by strong expression of BCL2 and CD10 in the germinal center B cells of the affected follicles. Case 1 showed the concurrence of an overt B-cell FL with IgH@ rearrangement and expression of B-cell markers, but not BCL2. Case 2 demonstrated the concurrence of a PTCL, NOS with TCRG@ rearrangement and expression of T-cell markers. In conclusion,the association of in situ FL with PTCL expands the spectrum of lymphoproliferations that may coexist with in situ FL and suggests that in situ FL may not behave like a simple precursor for overt FL.