BCL6 gene translocation in follicular lymphoma: a harbinger of eventual transformation to diffuse aggressive lymphoma

Predictive and prognostic molecular biomarkers in lymphomas

Recent advances in molecular diagnostics have markedly expanded our understanding of the genetic underpinnings of lymphomas and catalysed a transformation in not just how we classify lymphomas, but also how we treat, target, and monitor affected patients. Reflecting these advances, the World Health Organization Classification, International Consensus Classification, and National Comprehensive Cancer Network guidelines were recently updated to better integrate these molecular insights into clinical practice. We summarise here the molecular biomarkers of lymphomas with an emphasis on biomarkers that have well-supported prognostic and predictive utility, as well as emerging biomarkers that show promise for clinical practice. These biomarkers include: (1) diagnostic entity-defining genetic abnormalities [e.g., B-cell acute lymphoblastic leukaemia (B-ALL) with KMT2A rearrangement]; (2) molecular alterations that guide patients' prognoses (e.g., TP53 loss frequently conferring worse prognosis); (3) mutations that serve as the targets of, and often a source of acquired resistance to, small molecular inhibitors (e.g., ABL1 tyrosine kinase inhibitors for B-ALL BCR::ABL1, hindered by ABL1 kinase domain resistance mutations); (4) the growing incorporation of molecular measurable residual disease (MRD) in the management of lymphoma patients (e.g., molecular complete response and sequencing MRD-negative criteria in multiple myeloma). Altogether, our review spans the spectrum of lymphoma types, from the genetically defined subclasses of precursor B-cell lymphomas to the highly heterogeneous categories of small and large cell mature B-cell lymphomas, Hodgkin lymphomas, plasma cell neoplasms, and T/NK-cell lymphomas, and provides an expansive summary of our current understanding of their molecular pathology.

Head and neck follicular lymphoma with marginal zone differentiation and BCL2 translocation t(14;18) in both nodular and extranodular sites: a case report with mini-review

OBJECTIVE

Head and neck follicular lymphoma (FL) with marginal zone (MZ) differentiation is a rare high-risk B-cell composite variant that has been reported in nodular but not extranodular sites in the parotid glands. Here we summarize the literature on FL with MZ differentiation in head and neck nodular sites and describe a rare case of extranodular FL with MZ differentiation in the parotid gland.

STUDY DESIGN

We examined both the germinal center and MZ components of the parotid and bone-marrow biopsies of a 65-year-old female histologically, immunohistochemically, and molecularly to identify B-cell, germinal center, and follicular dendritic cell markers.

RESULTS

The immunohistochemical and molecular analysis provided evidence that the FL and the MZ components derived from the same B-cell clone with a similar BCL2/IGH t(14;18) translocation site. The differentiated cells in the MZ did not express germinal center markers BCL6 and CD10. Both the parotid and bone-marrow proliferative B cells showed BCL6, CD2O, and CD79a positivity.

CONCLUSIONS

Head and neck FL with MZ differentiation can develop in both nodular and extranodular sites and is characterized by BCL2 translocation t(14;18). Although the mechanism of MZ differentiation is unclear, the characterization of this rare histopathologic phenomenon might be clinically important.

B-cell Lymphoma 6 (BCL6): From Master Regulator of Humoral Immunity to Oncogenic Driver in Pediatric Cancers

B-cell lymphoma 6 (BCL6) is a protooncogene in adult and pediatric cancers, first identified in diffuse large B-cell lymphoma (DLBCL) where it acts as a repressor of the tumor suppressor TP53, conferring survival, protection, and maintenance of lymphoma cells. BCL6 expression in normal B cells is fundamental in the regulation of humoral immunity, via initiation and maintenance of the germinal centers (GC). Its role in B cells during the production of high affinity immunoglobins (that recognize and bind specific antigens) is believed to underpin its function as an oncogene. BCL6 is known to drive the self-renewal capacity of leukemia-initiating cells (LIC), with high BCL6 expression in acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and glioblastoma (GBM) associated with disease progression and treatment resistance. The mechanisms underpinning BCL6-driven therapy resistance are yet to be uncovered; however, high activity is considered to confer poor prognosis in the clinical setting. BCL6's key binding partner, BCL6 corepressor (BCOR), is frequently mutated in pediatric cancers and appears to act in concert with BCL6. Using publicly available data, here we show that BCL6 is ubiquitously overexpressed in pediatric brain tumors, inversely to BCOR, highlighting the potential for targeting BCL6 in these often lethal and untreatable cancers. In this review, we summarize what is known of BCL6 (role, effect, mechanisms) in pediatric cancers, highlighting the two sides of BCL6 function, humoral immunity, and tumorigenesis, as well as to review BCL6 inhibitors and highlight areas of opportunity to improve the outcomes of patients with pediatric cancer.

Genetics of Transformed Follicular Lymphoma

Histological transformation (HT) to a more aggressive disease–mostly diffuse large B-cell lymphoma–is considered one of the most dismal events in the clinical course of follicular lymphoma (FL). Current knowledge has not found a single biological event specific for HT, although different studies have highlighted common genetic alterations, such as TP53 and CDKN2A/B loss, and MYC translocations, among others. Together, they increase genomic complexity and mutational burden at HT. A better knowledge of HT pathogenesis would presumably help to find diagnostic biomarkers allowing the identification of patients at high-risk of transformation, as well as the discrimination from patients with FL recurrence, and those who remain in remission. This would also help to identify new drug targets and the design of clinical trials for the treatment of transformation. In the present review we provide a comprehensive overview of the genetic events frequently identified in transformed FL contributing to the switch towards aggressive behaviour, and we will discuss current open questions in the field of HT.

Diffuse large b-cell lymphoma of the ocular adnexa with flow cytometry analysis and review of the literature

PURPOSE

The aim of this study was to evaluate the clinicopathological features and flow cytometry (FCM) of tumor tissues in ocular adnexal diffuse large B-cell lymphoma (DLBCL).

METHODS

This retrospective, multicenter case study was designed to evaluate the clinical and immunohistochemical features of tumors. DLBCL was diagnosed based on histopathology, immunoglobulin (Ig) heavy chain gene rearrangement, and FCM in all surgically removed periocular tumor tissues. This study involved assessing percentages (%) of B-cell/T-cell markers, a natural killer cell marker, and cell-surface Ig kappa/lambda (κ/λ) expression measured by FCM analysis in tumor tissues.

RESULTS

Eleven DLBCL patients (4 men and 7 women) with 11 tumors were enrolled in this study. The median age at the time of initial presentation was 73 years. The tumor cells were immunohistochemically positive for cluster of differentiation (CD) 20, while CD5 was negative in all 8 cases tested. At the time of ophthalmic diagnosis, two cases already showed systemic dissemination of DLBCL throughout the body. FCM of tumor tissues detected a high percentage of B-cell markers including CD19 and CD20 in all 11 tumors. One case with high CD10 levels in FCM was histologic transformation from follicular lymphoma. One case with a relatively low CD20 population involved a history of systemic treatments including intravenous rituximab.

CONCLUSION

Although caution should be exercised when interpreting the data, FCM is useful for not only supportive diagnosis complementary to immunohistochemistry, but also facilitates a better understanding of immunopathology including histologic transformation of follicular lymphoma to DLBCL in the ocular adnexa.

Screening of Adverse Prognostic Factors and Construction of Prognostic Index in Previously Untreated Concurrent Follicular Lymphoma and Diffuse Large B-Cell Lymphoma

Objective

Concurrent follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) (defined as FL/DLBCL) have been considered an important pathological feature in cell lymphoma. However, clinicopathological information and prognostic factors in these cases are scarce. The aim of this study was to construct a prediction index to compare with traditional prognostic models.

Methods

Retrospectively enrolled, previously untreated FL/DLBCL (n = 121) patients, as well as those with pure FL 1-3a (n = 471), were assessed. De novo DLBCL (n = 529) were used as controls. Kaplan-Meier curves were plotted to compare the outcomes among the three groups. Multivariate analysis identified risk factors associated with overall survival (OS) in FL/DLBCL patients. A clinicopathological prognosis index (CPPI) was developed to predict OS based on the Cox proportional hazards model.

Results

The outcomes of FL/DLBCL patients were intermediate between pure FL 1-3a and de novo DLBCL patients, with a 5-year PFS of 70%, 59%, and 48% (P < 0.05) and 5-year OS of 80%, 70% and 60% (P < 0.05), respectively. Cox regression analysis showed that the prognostic factors of OS for FL/DLBCL patients included FL grade, cell of origin, and Ann Arbor stage. A nomogram and clinicopathological prognostic index (CPPI) were developed to predict the OS for FL/DLBCL patients based on these factors. The area under the curve (AUC) of the CPPI for 3- and 5-year OS prediction was 0.782 and 0.860, respectively. This was superior to that of the International Prognostic Index (IPI), Follicular Lymphoma International Prognostic Index (FLIPI), and FLIPI2 in the 0.540-0.819 (P < 0.01) range.

Conclusions

A valid OS estimation in FL/DLBCL patients, using the recommended CPPI, may be useful in routine clinical practice.

Frequent mutations of FBXO11 highlight BCL6 as a therapeutic target in Burkitt lymphoma

The expression of BCL6 in B cell lymphoma can be deregulated by chromosomal translocations, somatic mutations in the promoter regulatory regions or reduced proteasome-mediated degradation. FBXO11 was recently identified as a ubiquitin ligase involved in the degradation of BCL6 and is frequently inactivated in lymphoma or other tumors. Here, we show that FBXO11 mutations are found in 23% of Burkitt lymphoma (BL) patients. FBXO11 mutations impaired BCL6 degradation and the deletion of FBXO11 protein completely stabilized BCL6 levels in human BL cell lines. Conditional deletion of either one or two copies of the FBXO11 gene in mice cooperated with oncogenic MYC and accelerated B cell lymphoma onset, providing experimental evidence that FBXO11 is a haplo-insufficient oncosuppressor in B cell lymphoma. In WT and FBXO11-deficient BL mouse and human cell lines, targeting BCL6 via specific degrader or inhibitors partially impaired lymphoma growth in vitro and in vivo. Inhibition of MYC by the Omomyc mini-protein blocked cell proliferation and increased apoptosis, effects further increased by combined BCL6 targeting. Thus, by validating the functional role of FBXO11 mutations in BL we further highlight the key role of BCL6 in BL biology and provide evidence that innovative therapeutic approaches such as BCL6 degraders and direct MYC inhibition could be exploited as a targeted therapy for BL.

Robust detection of translocations in lymphoma FFPE samples using targeted locus capture-based sequencing

In routine diagnostic pathology, cancer biopsies are preserved by formalin-fixed, paraffin-embedding (FFPE) procedures for examination of (intra-) cellular morphology. Such procedures inadvertently induce DNA fragmentation, which compromises sequencing-based analyses of chromosomal rearrangements. Yet, rearrangements drive many types of hematolymphoid malignancies and solid tumors, and their manifestation is instructive for diagnosis, prognosis, and treatment. Here, we present FFPE-targeted locus capture (FFPE-TLC) for targeted sequencing of proximity-ligation products formed in FFPE tissue blocks, and PLIER, a computational framework that allows automated identification and characterization of rearrangements involving selected, clinically relevant, loci. FFPE-TLC, blindly applied to 149 lymphoma and control FFPE samples, identifies the known and previously uncharacterized rearrangement partners. It outperforms fluorescence in situ hybridization (FISH) in sensitivity and specificity, and shows clear advantages over standard capture-NGS methods, finding rearrangements involving repetitive sequences which they typically miss. FFPE-TLC is therefore a powerful clinical diagnostics tool for accurate targeted rearrangement detection in FFPE specimens.

RNA-Based next generation sequencing complements but does not replace fluorescence in situ hybridization studies for the classification of aggressive B-Cell lymphomas

Aggressive B-cell lymphomas are currently classified based in part upon the presence or absence of translocations involving BCL2, BCL6, and MYC. Most clinical laboratories employ fluorescence in situ hybridization (FISH) analysis for the detection of these rearrangements. The potential role of RNA-based sequencing approaches in the evaluation of malignant lymphoma is currently unclear. In this study, we performed RNA sequencing (RNAseq) in 37 cases of aggressive B-cell lymphomas using a commercially available next generation sequencing assay and compared results to previously performed FISH studies. RNAseq detected 1/7 MYC (14%), 3/8 BCL2 (38%) and 4/8 BCL6 (50%) translocations identified by FISH. RNAseq also detected 1 MYC/IGH fusion in a case not initially tested by FISH due to low MYC protein expression and 2 BCL6 translocations that were not detected by FISH. RNAseq identified the partner gene in each detected rearrangement, including a novel EIF4G1-BCL6 rearrangement. In summary, RNAseq complements FISH for the detection of rearrangements of BCL2, BCL6 and MYC in the evaluation and classification of aggressive B-cell lymphomas by detecting rearrangements that may be cryptic by FISH methods and by identifying the rearrangement partner genes. Detection of these clinically important translocations may be optimized by combined use of FISH and RNAseq.

Clinicopathological and prognostic significance of BCL2, BCL6, MYC, and IRF4 copy number gains and translocations in follicular lymphoma: a study by FISH analysis

BCL2 translocation is the genetic hallmark of follicular lymphoma (FL). Besides BCL2 translocation, copy number (CN) gains and translocations of BCL6, MYC, and IRF4 have also been detected in FL, but there is little information regarding their prognostic significance. This retrospective study used fluorescence in situ hybridization (FISH) to analyze BCL2, BCL6, MYC, and IRF4 translocations and CN gains in 105 FL cases. Genetic translocations were detected for BCL2 (n = 64; 72.7%), BCL6 (n = 14; 15.9%), and MYC (n = 2; 2.3%); no case showed IRF4 translocation. Overall, 23 (26.1%), 30 (34.1%), 12 (13.8%), and 10 (11.0%) cases showed CN gains in BCL2, BCL6, MYC, and IRF4, respectively. BCL6 CN gain was a prognostic factor for worse overall survival, demonstrating a trend toward significance in multivariate analysis (HR =8.769, p = 0.056). BCL6 CN gain in FL might be associated with aggressive biologic behavior.

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.

Relapse of follicular lymphoma arising from a non-t(14;18) clone

Intraclonal diversity is commonly observed in patients with follicular lymphoma (FL), whereas tumor cells at the onset and relapse usually share early genetic events such as VDJ rearrangement of the immunoglobulin genes and t(14;18) translocation. We report a case of FL with relapse with FL that was clonally different from the tumor cells at onset. A 59-year-old male presented with paraaortic lymph node swelling and thickening of the right renal pelvic and ureteral wall was histologically diagnosed as FL, grade 1. Karyotypic analysis revealed t(14;18)(q32;q21) with +12 and +der(18)t(14;18). Ten years after the initial diagnosis, he suddenly developed systemic lymphadenopathy as a second relapse, and histological examination led to the diagnosis of FL grade 3B with diffuse large B-cell lymphoma. Surprisingly, karyotypic analysis demonstrated the presence of +12 and 3q27 abnormality, which was proved to be a BCL6 translocation by fluorescence in situ hybridization, but the absence of t(14;18)(q32;q21). We compared VDJ rearrangement of the FL cells at onset and relapse and found that they were completely independent of each other. These tumor cells sharetrisomy 12 as a common genetic abnormality, and it is speculated that trisomy 12 may have occurred earlier than BCL2 and BCL6 translocations. These results suggest that there can even be cases of "relapse" of FL with an independent origin of the primary tumor cells. Our observation highlights the importance of re-biopsy of relapsed FL, especially when it occurs after a long remission with different clinical presentation from that at the onset.

Follicular lymphoma transforming to DLBCL and reverting back to follicular lymphoma at relapse-a case report

BACKGROUND

Transformation of low-grade follicular lymphoma to high-grade diffuse large B cell lymphoma (DLBCL) is known. However, the opposite is not commonly reported. In this report, we present a case of follicular lymphoma that underwent transformation to DLBCL. Three years after treatment for histologic transformation, the patient presented again with low-grade follicular lymphoma at the same site which is unusual in the natural history of follicular lymphoma.

CASE PRESENTATION

A 50-year-old female patient presented to us with complaints of slowly progressing swelling in the neck on the left side for a duration of 1 year. Past history of the patient revealed a diagnosis of follicular lymphoma in 2004 for which the patient had taken prednisolone and chlorambucil. Details of staging were not available with the patient. After a complete work-up, she was diagnosed as DLBCL, stage IIIE. She was treated with 6 cycles of CHOP regimen. She had very good response to chemotherapy. However, she defaulted and was lost to follow-up. She presented again after 3 years with history of painless progressive swelling in the right side of the neck for the last 1 year. Examination revealed cervical lymph nodes and ascites. This time, a repeat biopsy and immunohistochemistry was suggestive of follicular lymphoma. In view of significant ascites, she was started on chemotherapy with CVP regimen. After 6 cycles, she has good partial response and resolution of ascites. She is currently on follow-up.

CONCLUSIONS

We have presented a case of FL that has transformed to DLBCL after 10 years of diagnosis. After HT, she was treated with CHOP chemotherapy and the patient relapsed again after 3 years with follicular lymphoma histology. This case highlights the unique and varied natural history of follicular lymphoma that may be attributed to different subclones of malignant cells that may have arisen from a common progenitor FL cell and differential effect of chemotherapy on these subclones.

A Clinico-Genotypic Prognostic Index for De Novo Composite Diffuse Large B-Cell Lymphoma Arising from Follicular Lymphoma in Asian patients treated in the Rituximab Era

Composite follicular lymphoma with diffuse large B-cell lymphoma (FL/DLBCL) is uncommonly found on lymph node biopsy and represents a rare haematological malignancy. We aim to examine clinico-pathological features of patients with FL/DLBCL and investigate predictors of survival outcome. We included in our retrospective study patients with histologically-proven FL/DLBCL at diagnosis (n = 106) and who were subsequently treated with rituximab-based chemoimmunotherapy from 2002–2017 at the National Cancer Centre. The cohort consisted of 34 women and 72 men with a median age of 59 years (range, 24–82). In a multivariate model inclusive of known clinico-pathological parameters at diagnosis, advanced stage (p = 0.0136), presence of MYC and/or BCL6 rearrangement (p = 0.0376) and presence of B symptoms (p = 0.0405) were independently prognostic for worse overall survival (OS). The only remaining independent prognostic variables for worse OS after including first-line treatment data in the model were use of chemotherapy regimens other than R-CHOP (p = 0.0360) and lack of complete response to chemotherapy (p < 0.0001) besides the presence of B symptoms (p = 0.0022). We generated a Clinico-Genotypic Index by point-wise addition of all five adverse parameters (score of 0–1, 2, 3, 4–5) which revealed four prognostic risk groups with a predicted 5-year OS of 100%, 62%, 40% and 0% (p < 0.0001) accounting for 50.0%, 24.5%, 18.9% and 6.6% of the cohort respectively. We propose that R-CHOP should be the recommended first-line regimen for composite FL/DLBCL.

Follicular lymphoma

Follicular lymphoma (FL) is a systemic neoplasm of the lymphoid tissue displaying germinal centre (GC) B cell differentiation. FL represents ~5% of all haematological neoplasms and ~20-25% of all new non-Hodgkin lymphoma diagnoses in western countries. Tumorigenesis starts in precursor B cells and becomes full-blown tumour when the cells reach the GC maturation step. FL is preceded by an asymptomatic preclinical phase in which premalignant B cells carrying a t(14;18) chromosomal translocation accumulate additional genetic alterations, although not all of these cells progress to the tumour phase. FL is an indolent lymphoma with largely favourable outcomes, although a fraction of patients is at risk of disease progression and adverse outcomes. Outcomes for FL in the rituximab era are encouraging, with ~80% of patients having an overall survival of >10 years. Patients with relapsed FL have a wide range of treatment options, including several chemoimmunotherapy regimens, phosphoinositide 3-kinase inhibitors, and lenalidomide plus rituximab. Promising new treatment approaches include epigenetic therapeutics and immune approaches such as chimeric antigen receptor T cell therapy. The identification of patients at high risk who require alternative therapies to the current standard of care is a growing need that will help direct clinical trial research. This Primer discusses the epidemiology of FL, its molecular and cellular pathogenesis and its diagnosis, classification and treatment.

Dramatic increase in gene mutational burden after transformation of follicular lymphoma into TdT+ B-lymphoblastic leukemia/lymphoma

Transformation of follicular lymphoma (FL) into B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) is rare and results in greatly increased aggressiveness of clinical course. Here we present extensive molecular analysis of this unusual transformation, including immunoglobulin (Ig) gene rearrangement studies, cytogenetic analysis, and whole-exome sequencing (WES) of the patient's FL, B-ALL/LBL, and normal cells. Although FL showed marked somatic hypermutation (SHM) of the Ig genes, SHM appeared to be even more extensive in B-ALL/LBL. Cytogenetically, at least three translocations were identified in the B-ALL/LBL involving the BCL2, BCL6, and MYC genes; two of these, the BCL6 and BCL2 gene rearrangements, were already seen at the FL stage. WES identified 751 single-nucleotide variants with high allelic burden in the patient's cells, with the vast majority (575) present exclusively at the B-ALL/LBL stage. Of note, a TAF3 gene mutation was shared by normal, FL, and B-ALL/LBL tissue. A KMT2D nonsense mutation was identified in both FL and B-ALL/LBL and therefore may have contributed directly to lymphomagenesis. Mutations in KDM6A, SMARCA4, CBX1, and JMY were specific to the B-ALL/LBL stage, possibly contributing to the B-ALL/LBL transformation. Functionally, these identified mutations may lead to dysregulation of DNA repair, transcription, and cell differentiation. Thus, these genetic changes, together with the identified chromosomal translocations, may have contributed to lymphoma development and progression. Our findings may improve the mechanistic understanding of the FL-B-ALL/LBL transformation and may have therapeutic implications for this aggressive disease.

DSB structure impacts DNA recombination leading to class switching and chromosomal translocations in human B cells

Class switch recombination (CSR) requires activation-induced cytidine deaminase (AID) to trigger DNA double strand breaks (DSBs) at the immunoglobulin heavy chain (IGH) in B cells. Joining of AID-dependent DSBs within IGH facilitate CSR and effective humoral immunity, but ligation to DSBs in non-IGH chromosomes leads to chromosomal translocations. Thus, the mechanism by which AID-dependent DSBs are repaired requires careful examination. The random activity of AID in IGH leads to a spectrum of DSB structures. In this report, we investigated how DSB structure impacts end-joining leading to CSR and chromosomal translocations in human B cells, for which models of CSR are inefficient and not readily available. Using CRISPR/Cas9 to model AID-dependent DSBs in IGH and non-IGH genes, we found that DSBs with 5’ and 3’ overhangs led to increased processing during end-joining compared to blunt DSBs. We observed that 5’ overhangs were removed and 3’ overhangs were filled in at recombination junctions, suggesting that different subsets of enzymes are required for repair based on DSB polarity. Surprisingly, while Cas9-mediated switching preferentially utilized NHEJ regardless of DSB structure, A-EJ strongly preferred repairing blunt DSBs leading to translocations in the absence of NHEJ. We found that DSB polarity influenced frequency of Cas9-mediated switching and translocations more than overhang length. Lastly, recombination junctions from staggered DSBs exhibited templated insertions, suggesting iterative resection and filling in during repair. Our results demonstrate that DSB structure biases repair towards NHEJ or A-EJ to complete recombination leading to CSR and translocations, thus helping to elucidate the mechanism of genome rearrangements in human B cells.

The production of different classes of antibodies/immunoglobulins (IgM, IgG, etc.) is essential for protection against diverse pathogens and effective immunity. This cellular process is triggered by the enzyme activation-induced cytidine deaminase (AID). AID mutates DNA predominantly in antibody genes, generating different types of DNA breaks. Repair of DNA breaks initiated by AID leads to the production of different antibody classes. Erroneous repair of this damage can also lead to chromosomal translocations, a hallmark of lymphomas and other cancers. In this study, we used CRISPR/Cas9 technology to model the different types of DNA breaks physiologically produced by AID. We found that the specific structure of these DNA breaks strongly influenced how they were repaired. That is, different types of DNA breaks inform different modes of rejoining. Our findings show that not all types of DNA breaks are treated equally by genome maintenance machinery in the cell. These observations provide insight into the molecular mechanisms behind antibody-dependent immunity and lymphomagenesis.

New concepts in follicular lymphoma biology: From BCL2 to epigenetic regulators and non-coding RNAs

The molecular pathogenesis of follicular lymphoma (FL) was partially revealed 3 decades ago, with the discovery of the translocation that brings BCL2 under the influence of immunoglobulin heavy chain enhancers in a vast majority of cases. Despite the importance of this seminal observation, it has become increasingly clear that additional genetic alterations need to occur to trigger neoplastic transformation and disease progression. The evolution of FL involves developmental arrest and disruption of the normal function of one or more of epigenetic regulators including KMT2D/MLL2, EZH2, CBP/CREBBP, p300/EP300, and HIST1H1 in >95% of cases. B-cells "arrested" in germinal centers acquire dozens of additional genetic aberrations that influence key pathways controlling their physiological development including B Cell Receptor (BCR) signaling, PI3K/AKT, TLR, mTOR, NF-κB, JAK/STAT, MAPK, CD40/CD40L, chemokine, and interleukin signaling. Additionally, most cases of FL do not result from linear accumulation of genomic aberrations, but rather evolve from a common progenitor cell population by diverse evolution, creating multiple FL subclones in one patient. Moreover, one of the subclones might acquire a combination of aberrations involving genes controlling cell survival and proliferation including MDM2, CDKN2A/B, BCL6, MYC, TP53, β2M, FOXO1, MYD88, STAT3, or miR-17-92, and this can lead to the transformation of an initially indolent FL to an aggressive lymphoma (2%-3% risk per year). The complexity of the disease is also underscored by the importance of its interactions with the microenvironment that can substantially influence disease development and prognosis. Interpreting individual aberrations in relation to their impact on normal processes, their frequency, position in the disease evolution, and the consequences of their (co)occurrence, are the basis for understanding FL pathogenesis. This is necessary for the identification of patients with risk of early progression or transformation, for the development of novel targeted therapies, and for personalized treatment approaches. In this review, we summarize recent knowledge of molecular pathways and microenvironmental components involved in FL biology, and discuss them in the context of physiological B-cell development, FL evolution, and targeted therapies.

Generation and characteristics of a novel "double-hit" high grade B-cell lymphoma cell line DH-My6 with MYC/IGH and BCL6/IGH gene arrangements and potential molecular targeted therapies

“Double-hit” lymphoma (DHL) is a high-grade B-cell lymphoma that harbors concurrent MYC and BCL2 or BCL6 rearrangements. Because cases of MYC/BCL6 DHL are uncommon, most reported conclusions have been based on cases of MYC/BCL2 DHL. Lack of experimental MYC/BCL6 DHL models continues to hinder the pathophysiologic and therapeutic investigations of this disorder. We herein describe a novel MYC/BCL6 DHL cell line, designated DH-My6, carrying both the MYC–IGH and BCL6–IGH fusion genes. Interruptions of MYC and BCL6 expressions using short interfering RNAs and chemical inhibitors led to significant attenuation of DH-My6 cell growth. Greater antitumor effects were found when the cells were treated with a combination of MYC and BCL6 inhibitors. Moreover, the PLK1 inhibitor volasertib and the HDAC inhibitor vorinostat synergized strongly when combined with the bromodomain inhibitor JQ1. DH-My6 is a new well-validated MYC/BCL6 DHL cell line that will provide a useful model for studies of the pathogenesis and therapeutics for the less common DHL tumor type. The rationale for approaches targeting both MYC and BCL6, and in combination with PLK1 or HDAC inhibitors for superior suppression of the aggressive MYC/BCL6 DHL warrants further in vivo testing in a preclinical model.

Molecular Fingerprinting of Anatomically and Temporally Distinct B-Cell Lymphoma Samples by Next-Generation Sequencing to Establish Clonal Relatedness

CONTEXT.—

B-cell lymphomas exhibit balanced translocations that involve immunoglobulin loci and result from aberrant V(D)J recombination, class switch recombination, or somatic hypermutation. Although most of the breakpoints in the immunoglobulin loci occur in defined regions, those in the partner genes vary; therefore, it is unlikely that 2 independent clones would share identical breakpoints in both partners. Establishing whether a new lesion in a patient with history of lymphoma represents recurrence or a new process can be relevant. Polymerase chain reaction (PCR)-based clonality assays used in this setting rely only on evaluating the length of a given rearrangement. In contrast, next-generation sequencing (NGS) provides the exact translocation breakpoint at single-base resolution.

OBJECTIVE.—

To determine if translocation breakpoint coordinates can serve as a molecular fingerprint unique to a distinct clonal population.

DESIGN.—

Thirty-eight follicular lymphoma/diffuse large B-cell lymphoma samples collected from different anatomic sites and/or at different time points from 18 patients were analyzed by NGS. For comparison, PCR-based B-cell clonality and fluorescence in situ hybridization studies were performed on a subset of cases.

RESULTS.—

IGH-BCL2 rearrangements were detected in all samples. The breakpoint coordinates on derivative chromosome(s) were identical in all samples from a given patient, but distinct between samples derived from different patients. Additionally, 5 patients carried a second rearrangement also with conserved breakpoint coordinates in the follow-up sample(s).

CONCLUSIONS.—

Breakpoint coordinates in the immunoglobulin and partner genes can be used to establish clonal relatedness of anatomically/temporally distinct lesions. Additionally, an NGS-based approach has the potential to detect secondary translocations that may have prognostic and therapeutic significance.

Unexpected favorable outcome in a patient with high grade B-cell lymphoma with abnormalities of MYC, BCL6 and BCL2 loci

High grade B-cell lymphoma (HGBCL) by WHO 2016 classification requires rearrangements of MYC and BCL2 and/or BCL6, practically covering the so called "double-hit" or "triple hit" lymphomas. We report a case of HGBCL "triple-hit" lymphoma in a 64-year old female. Cytogenetic and fluorescence in situ hybridization (FISH) studies revealed complex karyotype including rearrangement of MYC to a novel, non-IG partner on chromosome 18, and rearrangement of BCL2, BCL6 and IGH as well as ins(3)(q21q27.3q25.1) among other abnormalities. FISH studies showed five copies of MYC and 3-8 copies of BCL2. Gene expression analysis by RNA sequencing showed that MYC, BCL2 and MECOM genes were overexpressed whereas BCL6 was under-expressed. BCL6 was fused to MBNL1 gene due to complex structural rearrangement. MYC was expressed in >70% of cells and BCL2 was diffusely but highly expressed by immunohistochemistry. No pathogenic mutations were identified by sequencing a 26-gene panel including TP53. The patient has unexpectedly been in complete remission for 12 months after diagnosis after intensive chemotherapy including DA-EPOCH regimen despite having HGBCL. The prognostication of HGBCL patients may further be improved by the sub-categorization of these lymphomas on the basis of more detailed genomic markers than merely the WHO 2016 classification.

From genetics to the clinic: a translational perspective on follicular lymphoma

Follicular lymphoma (FL) is the most frequent indolent B cell lymphoma and is still considered to be incurable. In recent years, whole-exome sequencing studies of large cohorts of patients have greatly improved our knowledge of the FL mutational landscape. Moreover, the prolonged evolution of this disease has enabled some insights regarding the early pre-lymphoma lesions as well as the clonal evolution after treatment, allowing an evolutionary perspective on lymphomagenesis. Deciphering the earliest initiating lesions and identifying the molecular alterations leading to disease progression currently represent important goals; accomplishing these could help identify the most relevant targets for precision therapy.

Epigenomic Modifications Mediating Antibody Maturation

Epigenetic modifications, such as histone modifications, DNA methylation status, and non-coding RNAs (ncRNA), all contribute to antibody maturation during somatic hypermutation (SHM) and class-switch recombination (CSR). Histone modifications alter the chromatin landscape and, together with DNA primary and tertiary structures, they help recruit Activation-Induced Cytidine Deaminase (AID) to the immunoglobulin (Ig) locus. AID is a potent DNA mutator, which catalyzes cytosine-to-uracil deamination on single-stranded DNA to create U:G mismatches. It has been shown that alternate chromatin modifications, in concert with ncRNAs and potentially DNA methylation, regulate AID recruitment and stabilize DNA repair factors. We, hereby, assess the combination of these distinct modifications and discuss how they contribute to initiating differential DNA repair pathways at the Ig locus, which ultimately leads to enhanced antibody–antigen binding affinity (SHM) or antibody isotype switching (CSR). We will also highlight how misregulation of epigenomic regulation during DNA repair can compromise antibody development and lead to a number of immunological syndromes and cancer.

Pathogenesis of follicular lymphoma

Follicular lymphoma (FL) is presented as a germinal centre B cell lymphoma that is characterized by an indolent clinical course, but remains - paradoxically - largely incurable to date. The last years have seen significant progress in our understanding of FL lymphomagenesis, which is a multi-step process beginning in the bone marrow with the hallmark t(14;18)(q32;q21) translocation. The pathobiology of FL is complex and combines broad somatic changes at the level of both the genome and the epigenome, the latter evidenced by highly recurrent mutations in chromatin-modifying genes such as KMT2D and CREBBP. While the importance of the FL microenvironment has since long been well understood, it has become evident that somatic lesions within tumour cells re-educate normal immune and stromal cells to their advantage. Enhanced understanding of FL pathogenesis is currently leading to refined therapeutic targeting of perturbed biology, paving the way for precision medicine in this lymphoma subtype.

Retrospective analysis of first-line treatment for follicular lymphoma based on outcomes and medical economics

BACKGROUND

Follicular lymphoma (FL) is the most common type of non-Hodgkin lymphoma (NHL), with indolent progression. Several treatment options are selected, based not only on disease status, quality of life (QOL), and age of patient, but also on recent increasing medical costs. We retrospectively analysed the first-line treatment of FL with regard to treatment outcomes and medical economics, and discuss the appropriate strategies for FL.

METHODS

Data on a total of 69 newly-diagnosed patients with FL was retrospectively collected from 2001 to 2015.

RESULTS

The median age of the patients was 60 years and the median follow-up was 58 months. A total of 25 cases with FL were treated with R monotherapy, and 28 cases were treated with R-CHOP as first-line treatment. The factors affecting the decision of physicians to use R or R-CHOP treatment were serum level of lactate dehydrogenase (LDH) and disease stage. The first-line treatment-associated survival did not show any statistical differences between R and R-CHOP. The average hospitalization and average of all medical costs during the first-line treatment were 4.1 days (R) versus 55.7 days (R-CHOP), and JPY 1,707,693 (USD 15,324) (R) versus JPY 2,136,117 (USD 19,170) (R-CHOP), respectively.

CONCLUSION

R monotherapy for patients whose diseases show low tumor burden and who are not candidates for local treatment has benefits as a first-line treatment compared to R-CHOP, based on the patients' QOL and medical economics.

Transformed follicular lymphoma

Follicular Lymphoma (FL) is the second most common type of non-Hodgkin lymphoma and is considered to be the prototype of indolent lymphomas. Histologic transformation into an aggressive lymphoma, which is expected to occur at a rate of 2 to 3% each year, is associated with rapid progression, treatment resistance, and poor prognosis. Recent modifications to the physiopathologic mechanism of transformed follicular lymphoma (t-FL) have been proposed, including genetic and epigenetic mechanisms as well as a role for the microenvironment. Although t-FL is considered a devastating complication, as it is associated with treatment-refractory disease and a dismal outcome, recent data in the rituximab era have suggested that not only is the prognosis less severe than reported in the previous literature but the risk of transformation is also lower. Thus, this study aimed to review the most recent research on t-FL in an attempt to better understand the clinical meaning of transformation from FL to diffuse large B cell lymphoma (DLBCL) and the impact of current treatment strategies on the curability of this intriguing subentity of lymphoma.

Current prognostic and predictive factors in follicular lymphoma

Follicular lymphoma (FL) is generally considered an indolent disorder. With modern day treatments, long remissions are often achieved both in the front-line and relapsed setting. However, a subset of patients has a more aggressive course and a worse outcome. Their identification is the main purpose of modern day prognostic tools. In this review, we attempt to summarize the evidence concerning prognostic and predictive factors in FL, including (1) pre-treatment factors, from baseline clinical characteristics and imaging tests to histological grade, the microenvironment and genomic abnormalities; (2) post-treatment factors, i.e., depth of response, measured both by imaging tests and minimal residual disease; (3) factors at relapse and duration of response; and (4) prognostic factors in histological transformation. We conclude that, despite the existence of numerous tools, the availability of some of them is still limited; they generally suffer from notable downsides, and most have unproven predictive value, thus having scarce bearing on the choice of regimen at present. However, with the technological and scientific developments of the last few years, the potential for these prognostic factors is promising, particularly in combination, which will probably, in time, help guide therapeutic decisions.

Can histologic transformation of follicular lymphoma be predicted and prevented?

Transformation to aggressive lymphoma is a critical event in the clinical course of follicular lymphoma (FL) patients. Yet, it is a challenge to reliably predict transformation at the time of diagnosis. Understanding the risk of transformation would be useful for guiding and monitoring patients, as well as for evaluating novel treatment strategies that could potentially prevent transformation. Herein, we review the contribution of clinical, pathological, and genetic risk factors to transformation. Patients with multiple clinical high-risk factors are at elevated risk of transformation but we are currently lacking a prognostic index that would specifically address transformation rather than disease progression or overall survival. From the biological standpoint, multiple studies have correlated individual biomarkers with transformation. However, accurate prediction of this event is currently hampered by our limited knowledge of the evolutionary pathways leading to transformation, as well as the scarcity of comprehensive, large-scale studies that assess both the genomic landscape of alterations within tumor cells and the composition of the microenvironment. Liquid biopsies hold great promise for achieving precision medicine. Indeed, mutations detected within circulating tumor DNA may be a better reflection of the inherent intratumoral heterogeneity than the biopsy of a single site. Last, we will assess whether evidence exists in the literature that transformation might be prevented altogether, based on the choice of therapy for FL.

Dysregulated MicroRNA Expression Profiles and Potential Cellular, Circulating and Polymorphic Biomarkers in Non-Hodgkin Lymphoma

A large number of studies have focused on identifying molecular biomarkers, including microRNAs (miRNAs) to aid in the diagnosis and prognosis of the most common subtypes of non-Hodgkin lymphoma (NHL), Diffuse Large B-cell Lymphoma and Follicular Lymphoma. NHL is difficult to diagnose and treat with many cases becoming resistant to chemotherapy, hence the need to identify improved biomarkers to aid in both diagnosis and treatment modalities. This review summarises more recent research on the dysregulated miRNA expression profiles found in NHL, as well as the regulatory role and biomarker potential of cellular and circulating miRNAs found in tissue and serum, respectively. In addition, the emerging field of research focusing on miRNA single nucleotide polymorphisms (miRSNPs) in genes of the miRNA biogenesis pathway, in miRNA genes themselves, and in their target sites may provide new insights on gene expression changes in these genes. These miRSNPs may impact miRNA networks and have been shown to play a role in a host of different cancer types including haematological malignancies. With respect to NHL, a number of SNPs in miRNA-binding sites in target genes have been shown to be associated with overall survival.

Follicular Lymphoma: A Clinicopathological Analysis from a Tertiary Care Institute in Southern India

Introduction

Follicular lymphoma (FL) is an indolent lymphoproliferative disorder of B-cells with variable clinical behavior. It is the second most common subtype of Non-Hodgkin lymphoma in western countries but reported to have a lower incidence in Asia.

Materials and methods

Cases of FL diagnosed in the Department of Pathology of our Institute from January 2009 to June 2015 were included in the study. The clinicopathological parameters including staging, histological details, and immunohistochemical markers CD20, CD10 and BCL-2 were recorded in all the cases.

Results

Of the 497 cases of Non-Hodgkin Lymphoma reported during the study period, 36 (7.2%) cases were follicular lymphoma. The mean age was 50 years with male to female ratio of 3.2:1. Grade 1/2 was seen in 70% cases. 22 % cases had low grade with high proliferation index (Ki67 > 40%). Granulomatous response was seen in two cases. Diffuse large cell lymphoma component was present in four cases. Bone marrow involvement and peripheral blood spill were seen in 12 (37.5%) and six cases (18.8%) respectively. 72% cases were in stage 3 or 4.

Conclusion

The incidence of FL was lower in our study than other Indian studies. FL presented in the elderly, with male predominance and disseminated stage. The study highlights features of low grade with high proliferation index, granulomatous response, leukemic involvement, and transformation to high grade lymphoma.

The tumour microenvironment influences survival and time to transformation in follicular lymphoma in the rituximab era

The tumour microenvironment influences outcome in patients with follicular lymphoma (FL), but its impact on transformation is less studied. We investigated the prognostic significance of the tumour microenvironment on transformation and survival in FL patients treated in the rituximab era. We examined diagnostic and transformed biopsies from 52 FL patients using antibodies against CD3, CD4, CD8, CD21 (CR2), CD57 (B3GAT1), CD68, FOXP3, TIA1, PD-1 (PDCD1), PD-L1 (CD274) and PAX5. Results were compared with a second cohort of 40 FL patients without signs of transformation during a minimum of five years observation time. Cell numbers and localization were semi-quantitatively assessed. Better developed CD21+  follicular dendritic cell (FDC) meshworks at diagnosis was a negative prognostic factor for overall survival (OS), progression-free survival (PFS) and time to transformation (TTT) in patients with subsequently transformed FL. Remnants of FDC meshworks at transformation were associated with shorter OS and PFS from transformation. High degrees of intrafollicular CD68+ and PD-L1+  macrophage infiltration, high total area scores and an extrafollicular/diffuse pattern of FOXP3+  T cells and high intrafollicular scores of CD4+  T cells at diagnosis were associated with shorter TTT. Scores of several T-cell subset markers from the combined patient cohorts were predictive for transformation, especially CD4 and CD57.

Fusion of PDGFRB to MPRIP, CPSF6, and GOLGB1 in three patients with eosinophilia-associated myeloproliferative neoplasms

In eosinophilia-associated myeloproliferative neoplasms (MPN-eo), constitutive activation of protein tyrosine kinases (TK) as consequence of translocations, inversions, or insertions and creation of TK fusion genes is recurrently observed. The most commonly involved TK and their potential TK inhibitors include PDGFRA at 4q12 or PDGFRB at 5q33 (imatinib), FGFR1 at 8p11 (ponatinib), and JAK2 at 9p24 (ruxolitinib). We here report the identification of three new PDGFRB fusion genes in three male MPN-eo patients: MPRIP-PDGFRB in a case with t(5;17)(q33;p11), CPSF6-PDGFRB in a case with t(5;12)(q33;q15), and GOLGB1-PDGFRB in a case with t(3;5)(q13;q33). The fusion proteins identified by 5'-rapid amplification of cDNA ends polymerase chain reaction (PCR) or DNA-based long distance inverse PCR are predicted to contain the TK domain of PDGFRB. The partner genes contain domains like coiled-coil structures, which are likely to cause dimerization and activation of the TK. In all patients, imatinib induced rapid and durable complete remissions.

Cell of origin of transformed follicular lymphoma

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.

Identification and functional characterization of imatinib-sensitive DTD1-PDGFRB and CCDC88C-PDGFRB fusion genes in eosinophilia-associated myeloid/lymphoid neoplasms

Eosinophilia-associated myeloid neoplasms with rearrangement of chromosome bands 5q31-33 are frequently associated with PDGFRB fusion genes, which are exquisitely sensitive to treatment with imatinib. In search for novel fusion partners of PDGFRB, we analyzed three cases with translocation t(5;20)(q33;p11), t(5;14)(q33;q32), and t(5;17;14)(q33;q11;q32) by 5′-rapid amplification of cDNA ends polymerase chain reaction (5′-RACE-PCR) and DNA-based long-distance inverse PCR (LDI-PCR) with primers derived from PDGFRB. LDI-PCR revealed a fusion between CCDC88C exon 25 and PDGFRB exon 11 in the case with t(5;17;14)(q33;q11;q32) while 5′-RACE-PCR identified fusions between CCDC88C exon 10 and PDGFRB exon 12 and between DTD1 exon 4 and PDGFRB exon 12 in the cases with t(5;14)(q33;q32) and t(5;20)(q33;p11), respectively. The PDGFRB tyrosine-kinase domain is predicted to be retained in all three fusion proteins. The partner proteins contained coiled-coil domains or other domains, which putatively lead to constitutive activation of the PDGFRB fusion protein. In vitro functional analyses confirmed transforming activity and imatinib-sensitivity of the fusion proteins. All three patients achieved rapid and durable complete hematologic remissions on imatinib.

Control of asymmetric Hopfield networks and application to cancer attractors

The asymmetric Hopfield model is used to simulate signaling dynamics in gene regulatory networks. The model allows for a direct mapping of a gene expression pattern into attractor states. We analyze different control strategies aimed at disrupting attractor patterns using selective local fields representing therapeutic interventions. The control strategies are based on the identification of signaling bottlenecks, which are single nodes or strongly connected clusters of nodes that have a large impact on the signaling. We provide a theorem with bounds on the minimum number of nodes that guarantee control of bottlenecks consisting of strongly connected components. The control strategies are applied to the identification of sets of proteins that, when inhibited, selectively disrupt the signaling of cancer cells while preserving the signaling of normal cells. We use an experimentally validated non-specific and an algorithmically-assembled specific B cell gene regulatory network reconstructed from gene expression data to model cancer signaling in lung and B cells, respectively. Among the potential targets identified here are TP53, FOXM1, BCL6 and SRC. This model could help in the rational design of novel robust therapeutic interventions based on our increasing knowledge of complex gene signaling networks.

Nature and importance of follicular lymphoma precursors

It is now widely recognized that cancer development is a protracted process requiring the stepwise acquisition of multiple oncogenic events. In humans, this process can take decades, if not a lifetime, blurring the notion of 'healthy' individuals. Follicular lymphoma exemplifies this multistep pathway of oncogenesis. In recent years, variants of follicular lymphoma have been recognized that appear to represent clonal B-cell expansions at an early stage of follicular lymphoma lymphomagenesis. These include follicular lymphoma in situ, duodenal follicular lymphoma, partial involvement by follicular lymphoma, and in the blood circulating follicular lymphoma-like B cells. Recent genetic studies have identified similarities and differences between the early lesions and overt follicular lymphoma, providing important information for understanding their biological evolution. The data indicate that there is already genomic instability at these early stages, even in instances with a low risk for clinical progression. The overexpression of BCL2 in t(14;18)-positive B cells puts them at risk for subsequent genetic aberrations when they re-enter the germinal center and are exposed to the influences of activation-induced cytidine deaminase and somatic hypermutations. The emerging data provide a rationale for clinical management and, in the future, may identify genetic risk factors that warrant early therapeutic intervention.

Whole-genome integrative analysis reveals expression signatures predicting transformation in follicular lymphoma

Whole-genome integrative analyses in FL reveal that genes strongly influenced by copy number are highly enriched for NF-kB pathway regulators. Subsignatures of the NF-kB targets predict transformation in FL.

Genetics of follicular lymphoma transformation

Follicular lymphoma (FL) is an indolent disease, but 30%-40% of cases undergo histologic transformation to an aggressive malignancy, typically represented by diffuse large B cell lymphoma (DLBCL). The pathogenesis of this process remains largely unknown. Using whole-exome sequencing and copy-number analysis, we show here that the dominant clone of FL and transformed FL (tFL) arise by divergent evolution from a common mutated precursor through the acquisition of distinct genetic events. Mutations in epigenetic modifiers and antiapoptotic genes are introduced early in the common precursor, whereas tFL is specifically associated with alterations deregulating cell-cycle progression and DNA damage responses (CDKN2A/B, MYC, and TP53) as well as aberrant somatic hypermutation. The genomic profile of tFL shares similarities with that of germinal center B cell-type de novo DLBCL but also displays unique combinations of altered genes with diagnostic and therapeutic implications.

Follicular lymphoma in young adults: a clinicopathological and molecular study of 200 patients

Follicular lymphoma is clinically heterogenous, and therefore necessitates the identification of prognostic markers to stratify risk groups and optimize clinical management. It is relatively rare in patients younger than 40 years, and the clinicopathologic characteristics and biological behavior in this age group are poorly understood. In the current study, samples from a cohort of 200 patients between 19 and 40 years were evaluated retrospectively with respect to clinical, histologic, and genetic features. These were then correlated with clinical outcome. The median age at presentation was 35 years with a slight female prepoderance (56%). Most of the cases are presented with nodal disease (90%). Concomitant follicular lymphoma and diffuse large B-cell lymphoma were observed in 7 (4%) patients. Immunohistologic studies showed the expression of CD10 (91%), BCL6 (97%), BCL2 (95%), MUM1/IRF4 (12%), MDM2 (17%), and CD23 (25%). BCL2 rearrangement was present in 74%, and BCL6 in 20%. The estimated overall survival of patients was 13 years (mean). The presence of anemia, elevated lactose dehydrogenase, bone marrow involvement, and high-risk follicular lymphoma international prognostic index correlated with adverse overall survival. Our findings revealed that follicular lymphoma in young adults demonstrate similarities with that of older adults, including the frequency of presentation at various anatomic sites, grade, and adverse prognostic factors.

Pathogenesis of follicular lymphoma

The hallmark t(14;18)(q32;q21) in follicular lymphoma (FL) results in constitutive overexpression of the BCL2 protein, allowing B cells to abrogate the default germinal center apoptotic program. Most tumors are characterized by recurrent secondary genetic alterations including genomic gains, losses, and mutations, some providing a growth advantage, including alterations in MLL2, EPHA7, TNFRSF14, and EZH2. The sequence in which these events occur and how they contribute to progression and ultimately to transformation is unclear. Lastly, crosstalk between neoplastic B cells and non-neoplastic immune and stromal cells in the microenvironment plays an important role in sustaining tumor cell growth, cultivating immune privilege, and promoting transformation.