Pathogenesis of follicular lymphoma: genetics to the microenvironment to clinical translation

Patients with Classic Hodgkin Lymphoma and Follicular Lymphoma Compared to Single Malignancy Controls

Classic Hodgkin lymphoma (CHL) can arise in patients with low-grade B-cell lymphoma. The features of CHL arising in follicular lymphoma (FL) and its outcome are still unclear, mainly due to the very few cases reported. This study compares 17 patients with CHL and FL to 2 control groups: 1 of 26 patients with FL and a second of 60 patients older than 40 when diagnosed with CHL. Of the FL and CHL patients, 8 had simultaneous FL and CHL, while 9 had FL first, followed by CHL 4.7 years later on average. The age at the diagnosis of FL was 61 years for patients with synchronous FL and CHL and of 60 years for FL, followed by CHL at 65 years. Patients with FL only were, on average, 59 years old at presentation, while CHL patients were 61. FL was grade 1-2 in 75% of FL and CHL patients and 67% of FL first and CHL second patients, lower proportions than in the FL control group-92%. Epstein-Barr virus (EBV) was detected in a lower fraction (29%) of the FL and CHL group than in CHL-only controls (46%). BCL2 translocations were detected in 4 of the 7 cases with FL, but in positive cases, the rearrangement was also present in the CHL component, indicating a clonal relationship between FL and CHL. Patients with FL and CHL treated for CHL had an initial outcome more similar to FL than to CHL controls.

Chimeric Antigen Receptor T-Cells in Indolent Lymphoma, Mantle Cell Lymphoma, Chronic Lymphocytic Leukemia

The advent of chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment of several hematological malignancies. Although the initial benefit was mainly observed in aggressive leukemias and lymphomas, recent data have resulted in the approval of multiple CAR-T therapies in indolent lymphomas, with ongoing research showing great promise for further improvements and therapeutic optimizations. In this article, we review the published data and approved therapies for CAR-T cell therapy for indolent lymphomas focusing on mantle cell lymphoma and follicular lymphoma while describing the work in chronic lymphocytic leukemia and future strategies.

Oral follicular lymphoma: a clinicopathologic and molecular study

Follicular lymphoma is a hematolymphoid neoplasm that originates from germinal center B cells. It is made up of a combination of small cleaved centrocytes and a varying quantity of larger non-cleaved centroblasts to describe the clinical, microscopic, immunohistochemical, and molecular features of oral follicular lymphomas. Follicular lymphomas affecting the oral cavity were retrieved from pathology files. Immunohistochemistry was performed to confirm the diagnosis, and fluorescence in situ hybridization (FISH) was employed to detect rearrangements in BCL2, BCL6, and MYC genes. Clinical and follow-up data were obtained from the patient's medical and pathology files. Twenty cases were obtained. There was an equal sex distribution (10 males: 10 females) and a mean age of 60.9 years (range: 10-83 years-old). Lesions presented as asymptomatic swellings, usually in the palate (10 cases) and the buccal mucosa (7 cases). Five patients presented with concomitant nodal involvement. Microscopic evaluation depicted the follicular growth pattern with diffuse areas in six cases. Grades 1 and 2 follicular lymphomas represented 12 cases, while grade 3A neoplasms accounted for other 8 cases. Two cases showed rearrangements in MYC, BCL2, and BCL6 genes, while single BCL2 translocation was found in eight cases. Two cases had no translocation. Three patients deceased and the 2-year overall survival achieved 88%. Follicular lymphoma affecting the oral cavity is uncommon, usually affects the palate as a non-ulcerated swelling and the presence of a systemic disease most always be ruled out.

Cytogenomics of B-cell non-Hodgkin lymphomas: The "old" meets the "new"

For the routine diagnosis of haematological neoplasms an integrative approach is used considering the morphology, and the immunophenotypic, and molecular features of the tumor sample, along with clinical information. The identification and characterization of recurrent chromosomal aberrations mainly detected by conventional and molecular cytogenetics in the tumor cells has a major impact on the classification of lymphoid neoplasms. Some of the B-cell non-Hodgkin lymphomas are characterized by particular chromosomal aberrations, highlighting the relevance of conventional and molecular cytogenetic studies in their diagnosis and prognosis. In the current genomics era, next generation sequencing provides relevant information as the mutational profiles of haematological malignancies, improving their classification and also the clinical management of the patients. In addition, other new technologies have emerged recently, such as the optical genome mapping, which can overcome some of the limitations of conventional and molecular cytogenetics and may become more widely used in the cytogenetic laboratories in the upcoming years. Moreover, epigenetic alterations may complement genetic changes for a deeper understanding of the pathogenesis underlying B-cell neoplasms and a more precise risk-based patient stratification. Overall, here we describe the current state of the genomic data integrating chromosomal rearrangements, copy number alterations, and somatic variants, as well as a succinct overview of epigenomic changes, which altogether constitute a comprehensive diagnostic approach in B-cell non-Hodgkin lymphomas.

Location, location, location: mapping the lymphoma tumor microenvironment using spatial transcriptomics

Lymphomas are a heterogenous group of lymphoid neoplasms with a wide variety of clinical presentations. Response to treatment and prognosis differs both between and within lymphoma subtypes. Improved molecular and genetic profiling has increased our understanding of the factors which drive these clinical dynamics. Immune and non-immune cells within the lymphoma tumor microenvironment (TME) can both play a key role in antitumor immune responses and conversely also support lymphoma growth and survival. A deeper understanding of the lymphoma TME would identify key lymphoma and immune cell interactions which could be disrupted for therapeutic benefit. Single cell RNA sequencing studies have provided a more comprehensive description of the TME, however these studies are limited in that they lack spatial context. Spatial transcriptomics provides a comprehensive analysis of gene expression within tissue and is an attractive technique in lymphoma to both disentangle the complex interactions between lymphoma and TME cells and improve understanding of how lymphoma cells evade the host immune response. This article summarizes current spatial transcriptomic technologies and their use in lymphoma research to date. The resulting data has already enriched our knowledge of the mechanisms and clinical impact of an immunosuppressive TME in lymphoma and the accrual of further studies will provide a fundamental step in the march towards personalized medicine.

Genomic landscape of follicular lymphoma across a wide spectrum of clinical behaviors

While some follicular lymphoma (FL) patients do not require treatment or experience prolonged responses, others relapse early, and little is known about genetic alterations specific to patients with a particular clinical behavior. We selected 56 grade 1-3A FL patients according to their need of treatment or timing of relapse: never treated (n = 7), non-relapsed (19), late relapse (14), early relapse or POD24 (11), and primary refractory (5). We analyzed 56 diagnostic and 12 paired relapse lymphoid tissue biopsies and performed copy number alteration (CNA) analysis and next generation sequencing (NGS). We identified six focal driver losses (1p36.32, 6p21.32, 6q14.1, 6q23.3, 9p21.3, 10q23.33) and 1p36.33 copy-neutral loss of heterozygosity (CN-LOH). By integrating CNA and NGS results, the most frequently altered genes/regions were KMT2D (79%), CREBBP (67%), TNFRSF14 (46%) and BCL2 (40%). Although we found that mutations in PIM1, FOXO1 and TMEM30A were associated with an adverse clinical behavior, definitive conclusions cannot be drawn, due to the small sample size. We identified common precursor cells harboring early oncogenic alterations of the KMT2D, CREBBP, TNFRSF14 and EP300 genes and 16p13.3-p13.2 CN-LOH. Finally, we established the functional consequences of mutations by means of protein modeling (CD79B, PLCG2, PIM1, MCL1 and IRF8). These data expand the knowledge on the genomics behind the heterogeneous FL population and, upon replication in larger cohorts, could contribute to risk stratification and the development of targeted therapies.

The pathobiology of follicular lymphoma

Follicular lymphoma is one of the most frequent lymphomas. Histologically, it is characterized by a follicular (nodular) growth pattern of centrocytes and centroblasts; mixed with variable immune microenvironment cells. Clinically, it is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. It is biologically and clinically heterogeneous. In most patients it is indolent, but others have a more aggressive evolution with relapses; and transformation to diffuse large B-cell lymphoma. Tumorigenesis includes an asymptomatic preclinical phase in which premalignant B-lymphocytes with the t(14;18) chromosomal translocation acquire additional genetic alterations in the germinal centers, and clonal evolution occurs, although not all the cells progress to the tumor stage. This manuscript reviews the pathobiology and clinicopathological characteristics of follicular lymphoma. It includes a description of the physiology of the germinal center, the genetic alterations of BCL2 and BCL6, the mutational profile, the immune checkpoint, precision medicine, and highlights in the lymphoma classification. In addition, a comment and review on artificial intelligence and machine (deep) learning are made.

Integrative genomic and transcriptomic analysis reveals genetic alterations associated with the early progression of follicular lymphoma

Follicular lymphoma (FL), the most common indolent lymphoma, is a clinically and genetically heterogeneous disease. However, the prognostic value of driver gene mutations and copy number alterations has not been systematically assessed. Here, we analysed the clinical-biological features of 415 FL patients to identify variables associated with disease progression within 24 months of first-line therapy (POD24). Patients with B symptoms, elevated lactate dehydrogenase and β2-microglobulin levels, unfavourable baseline haemoglobin levels, advanced stage, and high-risk FL International Prognostic Index (FLIPI) scores had an increased risk of POD24, with FLIPI being the most important factor in logistic regression. HIST1H1D, identified as a driver mutation, was correlated with POD24. Gains of 6p22.2 (HIST1H1D) and 18q21.33 (BCL2) and loss of 1p36.13 (NBPF1) predicted POD24 independent of FLIPI. Gene expression profiling of FL samples showed that the POD24 cohort was significantly enriched in the inflammatory response (mediated by interferon and tumour necrosis factor), cell cycle regulation (transcription, replication and proliferation) sets and PI3K-AKT-mTOR signalling. This result was further validated with transcriptome-wide information provided by RNA-seq at single-cell resolution. Our study, performed on a large cohort of FL patients, highlights the importance of distinctive genetic alterations and gene expression relevant to disease diagnosis and early progression.

Personalised therapy in follicular lymphoma - is the dial turning?

Follicular lymphoma is the most common indolent lymphoma accounting for approximately 20%-25% of all new non-Hodgkin lymphoma diagnoses in western countries. Whilst outcomes are mostly favorable, the spectrum of clinical phenotypes includes high-risk groups with significantly inferior outcomes. This review discusses recent updates in risk stratification and treatment approaches from upfront treatment for limited and advanced stage follicular lymphoma to the growing options for relapsed, refractory disease with perspectives on how to approach this from a personalized lens. Notable gaps remain on how one can precisely and prospectively select optimal treatment for patients based on varying risks, with an anticipation that an increased understanding of the biology of these different phenotypes and increasing refinement of imaging- and biomarker-based tools will, in time, allow these gaps to be closed.

Relationship between BCL2 mutations and follicular lymphoma outcome in the chemoimmunotherapy era

How to identify follicular lymphoma (FL) patients with low disease burden but high risk for early progression is unclear. Building on a prior study demonstrating the early transformation of FLs with high variant allele frequency (VAF) BCL2 mutations at activation-induced cytidine deaminase (AICDA) sites, we examined 11 AICDA mutational targets, including BCL2, BCL6, PAX5, PIM1, RHOH, SOCS, and MYC, in 199 newly diagnosed grade 1 and 2 FLs. BCL2 mutations with VAF ≥20% occurred in 52% of cases. Among 97 FL patients who did not initially receive rituximab-containing therapy, nonsynonymous BCL2 mutations at VAF ≥20% were associated with increased transformation risk (HR 3.01, 95% CI 1.04-8.78, p = 0.043) and a trend toward shorter event-free survival (EFS, median 20 months with mutations versus 54 months without, p = 0.052). Other sequenced genes were less frequently mutated and did not increase the prognostic value of the panel. Across the entire population, nonsynonymous BCL2 mutations at VAF ≥20% were associated with decreased EFS (HR 1.55, 95% CI 1.02-2.35, p = 0.043 after correction for FLIPI and treatment) and decreased overall survival after median 14-year follow-up (HR 1.82, 95% CI 1.05-3.17, p = 0.034). Thus, high VAF nonsynonymous BCL2 mutations remain prognostic even in the chemoimmunotherapy era.

Clinicopathological and molecular genetic characteristics of primary gastric follicular lymphoma☆,☆☆,☆☆☆

Primary gastric follicular lymphomas (FLs) have been rarely reported and little is known about their characteristics. In the present study, we report five cases of primary gastric FL and describe their clinicopathological and molecular genetic features. A total of seven samples from five patients were investigated for clinicopathological characteristics and somatic mutations by the targeted sequencing of 50 lymphoma-related genes. Two cases were identified as slightly elevated submucosal tumors and three cases as polypoid tumors. Histologically, all cases were low-grade FLs. The immuno-profile was CD20⁺/CD10⁺/BCL2⁺ in four cases and CD20⁺/CD10⁺/BCL2^- in one case. Immunostaining pattern for CD21 was similar to that of classic FL. BCL2 rearrangement was not identified in fluorescence in situ hybridization studies in any of the five cases. NGS analysis showed mutations in genes involved in epigenetic modifications (KMT2D, ARID1A, EP300, CREBBP), NK-kB pathway (CARD11), and JAK-STAT pathway as found in classic follicular lymphoma. All cases presented with clinical I without the involvement of regional or systemic lymph nodes. Four patients were well, whereas one patient who received endoscopic mucosal resection of tumor without additional chemotherapy or radiotherapy experienced three relapses. In conclusion, primary gastric FL is characterized by a low-grade neoplasm with infrequent BCL2 rearrangement. After resection of the lesion, additional treatment such as radiation therapy or chemotherapy is required as there is a possibility of recurrence.

Follicular Lymphoma in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Biological Data

The conceptual description of Follicular lymphoma (FL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) has undergone significant revision. The vast majority of FL (85%) with a follicular growth pattern are composed of centrocytes and centroblasts, harbor the t(14;18)(q32;q21) translocation and are now termed classic FL (cFL). They are set apart from three related subtypes, FL with predominantly follicular growth pattern, FL with unusual cytological features (uFL) and follicular large B-cell lymphoma (FLBCL). In contrast to the revised 4th edition of the WHO classification of haematolymphoid tumors (WHO-HAEM4R), grading of cFL is no longer mandatory. FL with a predominantly diffuse growth pattern had been previously recognized in WHO-HAEM4R. It frequently occurs as a large tumor in the inguinal region and is associated with CD23 expression. An absence of the IGH::BCL2 fusion and frequent STAT6 mutations along with 1p36 deletion or TNFRSF14 mutation is typical. The newly introduced subtype of uFL includes two subsets that significantly diverge from cFL: one with "blastoid" and one with "large centrocyte" variant cytological features. uFL more frequently displays variant immunophenotypic and genotypic features. FLBCL is largely identical to WHO-HAEM4R FL grade 3B and renaming was done for reasons of consistency throughout the classification. In-situ follicular B-cell neoplasm, pediatric-type FL, duodenal-type FL and primary cutaneous follicle center lymphoma are categorized as discrete entities. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of early and systemic follicular lymphoma will be presented.

Biology of follicular lymphoma: insights and windows of clinical opportunity

Follicular lymphoma (FL) is a heterogeneous disease, both clinically and biologically. The biological behavior and development of FL is a culmination of complex multistep processes underpinned by genetic and nongenetic determinants. Epigenetic deregulation through recurrent genetic alterations is now a recognized major biological hallmark of FL, alongside the t(14;18) translocation. In parallel, there is a strong interplay between the lymphoma B cells and the immune microenvironment, with the microenvironment serving as a critical enabler by creating a tumor-supportive niche and modulating the immune response to favor survival of the malignant B cells. A further layer of complexity arises from the biological heterogeneity that occurs between patients and within an individual, both over the course of the disease and at different sites of disease involvement. Altogether, taking the first steps to bridge the understanding of these various biological components and how to evaluate these clinically may aid and inform future strategies, including logical therapeutic interventions, risk stratification, therapy selection, and disease monitoring.

The prognostic nutritional index, an independent predictor of overall survival for newly diagnosed follicular lymphoma in China

Objective

The prognostic nutritional index (PNI) is an important prognostic factor for survival outcomes in various hematological malignancies. The current study focused on exploring the predictive value of the PNI in newly diagnosed follicular lymphoma (FL) in China.

Materials and methods

The clinical indicators and follow-up data of 176 patients who received chemotherapy or immunotherapy combined with chemotherapy with FL in our hospital from January 2016 to March 2022 were retrospectively analyzed. Cox proportional hazard model was used for univariate and multivariate analyses. Kaplan–Meier curves were used to calculate survival rates and draw survival curves. The log-rank test was applied to compare differences between groups.

Results

The optimal cut-off value of PNI was 44.3. All patients were divided into a high PNI group (>44.3) and a low PNI group (≤44.3). The low PNI group had a low CR rate and a high risk of death, with a tendency toward POD24, and Both OS and PFS were worse than those in the high PNI group. PNI was able to predict OS and PFS in FL patients and was the only independent predictor of OS (P = 0.014 HR 5.024; 95%CI 1.388∼18.178) in multivariate analysis. PNI could re-stratify patients into groups of high FLIPI score, high FLIPI2 score, no POD24, and rituximab combined with chemotherapy. Moreover, integrating PNI into the FLIPI and FLIPI2 models improved the area under the curve (AUC) for more accurate survival prediction and prognosis.

Conclusion

PNI is a significant prognostic indicator for newly diagnosed FL in China that can early identify patients with poor prognosis and guide clinical treatment decisions.

High inter-follicular spatial co-localization of CD8+FOXP3+ with CD4+CD8+ cells predicts favorable outcome in follicular lymphoma

The spatial architecture of the lymphoid tissue in follicular lymphoma (FL) presents unique challenges to studying its immune microenvironment. We investigated the spatial interplay of T cells, macrophages, myeloid cells and natural killer T cells using multispectral immunofluorescence images of diagnostic biopsies of 32 patients. A deep learning-based image analysis pipeline was tailored to the needs of follicular lymphoma spatial histology research, enabling the identification of different immune cells within and outside neoplastic follicles. We analyzed the density and spatial co-localization of immune cells in the inter-follicular and intra-follicular regions of follicular lymphoma. Low inter-follicular density of CD8+FOXP3+ cells and co-localization of CD8+FOXP3+ with CD4+CD8+ cells were significantly associated with relapse (p = 0.0057 and p = 0.0019, respectively) and shorter time to progression after first-line treatment (Logrank p = 0.0097 and log-rank p = 0.0093, respectively). A low inter-follicular density of CD8+FOXP3+ cells is associated with increased risk of relapse independent of follicular lymphoma international prognostic index (FLIPI) (p = 0.038, Hazard ratio (HR) = 0.42 [0.19, 0.95], but not independent of co-localization of CD8+FOXP3+ with CD4+CD8+ cells (p = 0.43). Co-localization of CD8+FOXP3+ with CD4+CD8+ cells is predictors of time to relapse independent of the FLIPI score and density of CD8+FOXP3+ cells (p = 0.027, HR = 0.0019 [7.19 × 10-6 , 0.49], This suggests a potential role of inter-follicular CD8+FOXP3+ and CD4+CD8+ cells in the disease progression of FL, warranting further validation on larger patient cohorts.

Clinical usefulness of a novel classification of T cell distribution patterns in the tumor microenvironment of follicular lymphoma to detect transformation

The clinical course of follicular lymphoma (FL) is thought to be influenced by the infiltrating immune cells in the tumor microenvironment. Focusing on the distribution patterns of T cells may be a promising approach to estimate the prognosis of FL, especially histological transformation. This study was a retrospectively cohort study in the relationship between the pathological distribution pattern of T cells in the tumor microenvironment and clinical course of FL. One hundred twenty-eight patients with FL initially diagnosed at the University of Tokyo Hospital from January 2008 to January 2017 were evaluated. We classified each patient's specimen at initial diagnosis by the distribution pattern of tumor infiltrating CD3-positive cells, intra-follicle focal (IFF), intra-follicle diffuse (IFD), extra-follicle marginal (EFM), and extra-follicle diffuse (EFD). We analyzed the distribution pattern's correlation with other prognostic factors including overall survival (OS), progression free survival (PFS), and transformation. Among 128 cases, 81 had evaluable pathological specimen. Based on our criteria, in the intra-follicle,17 cases (21%) were classified as IFF. Sixty-four cases (79%) were classified as IFD. In the extra follicle, 25 cases (31%) were classified as EFM. Fifty-six cases (69%) were classified as EFD. There was significant difference in risk of transformation between the EFM and EFD around extra-follicle area in the adjusted model (p < 0.05). Also, cases with IFF and EFM had significantly higher risk of transformation compared to cases with other T cell distribution patterns (p < 0.01). We proposed a new classification of CD3-positive T cell distribution patterns around the follicle lesions in FL and demonstrated its clinical significance.

Revising the Treatment Pathways in Lymphoma: New Standards of Care-How Do We Choose?

Diffuse large B-cell lymphoma and follicular lymphoma are the most commonly encountered non-Hodgkin lymphomas in clinical practice. Both are biologically heterogeneous, with management strategies that are becoming increasingly complex. Diffuse large B-cell lymphoma typically exhibits aggressive behavior but can be cured in the majority of cases with immunochemotherapy. While R-CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) has been the standard of care for decades, the recent combination of polatuzumab-vedotin-R-CHP (rituximab plus cyclophosphamide, doxorubicin, and prednisone) has demonstrated improved progression-free survival for patients with intermediate- and intermediate-high-risk disease. Numerous novel therapies, including targeted agents and immunotherapy-based approaches, have recently been approved for relapsed/refractory disease and have led to improved outcomes. Follicular lymphoma is an indolent lymphoma that remains incurable with standard approaches. Overall survival in most patients is excellent, although a proportion of patients will have early relapsing disease and poorer outcomes. The availability of novel agents in the relapsed/refractory setting has shifted the treatment algorithm, which requires thoughtful consideration of sequencing. This article will review recent developments in the treatment of diffuse large B-cell lymphoma and relapsed/refractory follicular lymphoma.

Diversity upon diversity: linking DNA double-strand break repair to blood cancer health disparities

Chromosomal translocations arising from aberrant repair of multiple DNA double-strand breaks (DSBs) are a defining characteristic of many cancers. DSBs are an essential part of physiological processes in antibody-producing B cells. The B cell environment is poised to generate genome instability leading to translocations relevant to the pathology of blood cancers. These are a diverse set of cancers, but limited data from under-represented groups have pointed to health disparities associated with each. We focus on the DSBs that occur in developing B cells and propose the most likely mechanism behind the formation of translocations. We also highlight specific cancers in which these rearrangements occur and address the growing concern of health disparities associated with them.