Chromatin modifying gene mutations in follicular lymphoma

Current and future therapies for follicular lymphoma

Follicular lymphoma (FL) is an indolent, germinal center B cell-derived lymphoid neoplasm, for which recent advances in treatment have substantially improved patient survival. However, FL remains an incurable and heterogeneous disease, with groups of patients experiencing early disease progression, histologic transformation, or a high risk of treatment-related toxicity. Additionally, FL is a continually relapsing disease, and response rates and disease-control intervals decrease with each subsequent line of therapy. In this review, we explore the current treatment landscape for relapsed or refractory FL and promising therapies in development, highlighting the efficacy and potential risks of each treatment. We provide a real-world perspective on the unmet needs of patients with FL. Novel therapeutic approaches in development offer a wide array of options for clinicians when treating relapsed or refractory FL. A nuanced approach is required to address the needs of individual patients, taking into consideration both the risks and benefits of each treatment option, as well as patient preferences.

Feasibility of Circulating Tumor DNA Analysis in Patients with Follicular Lymphoma

PURPOSE

The feasibility of sequencing circulating tumor DNA (ctDNA) in plasma as a biomarker to predict early relapse or poor prognosis in patients with follicular lymphoma (FL) receiving systemic immunochemotherapy is not clear.

MATERIALS AND METHODS

We sequenced DNA from cell-free plasma that was serially obtained from newly diagnosed FL patients undergoing systemic immunochemotherapy. The mutation profiles of ctDNA at the time of diagnosis and at response evaluation and relapse and/or progression were compared with clinical course and treatment outcomes.

RESULTS

Forty samples from patients receiving rituximab-containing immunochemotherapy were analyzed. Baseline sequencing detected mutations in all cases, with the major detected mutations being KMT2C (50%), CREBBP (45%), and KMT2D (45%). The concentration of ctDNA and tumor mutation burden showed a significant association with survival outcome. In particular, the presence of mutations in CREBBP and TP53 showed poor prognosis compared with patients without them. Longitudinal analysis of ctDNA using serially collected plasma samples showed an association between persistence or reappearance of ctDNA mutations and disease relapse or progression.

CONCLUSION

Analysis of ctDNA mutations in plasma at diagnosis might help predict outcome of disease, while analysis during follow-up may help to monitor disease status of patients with advanced FL. However, the feasibility of ctDNA measurement must be improved in order for it to become an appropriate and clinically relevant test in FL patients.

Translational insights into the genetics and immunobiology of relapsed/refractory follicular lymphoma

Although follicular lymphoma (FL) is traditionally classified as an indolent subtype of B cell non-Hodgkin lymphoma, clinical trajectories are often diverse based on unique disease biology, and many patients will eventually experience relapse of their disease. Furthermore, progression of disease within 24 months is associated with increased mortality rates for FL. In the last five years, we have witnessed an upsurge in the commercial availability of targeted therapies for relapsed/refractory (R/R) FL, including chimeric antigen receptor-T (CAR-T) products, bispecific T cell engagers (BiTEs), epigenetic modifier therapies, and next-generation Bruton tyrosine kinase (BTK) inhibitors. Furthermore, clinical trial options have increased tremendously and now include combinatorial strategies that exert synergy against malignant germinal center B cells. Here, we provide a 2024 update of novel therapeutic agents whose development has been informed by recent advances in the genetics and immunobiology of R/R FL. Specifically, we emphasize high-value targeted therapeutics, including anti-CD3 x anti-CD20 BiTEs and adoptive T cell therapies. We discuss prospects on selection and sequencing of BiTEs and CAR-T therapies for patients with R/R FL. We underscore the principles of FL pathobiology that are paving way for future drug discovery and shed insight into therapeutic targeting within nodal basins based on our increasing understanding of the FL microenvironment. Finally, we summarize how a greater knowledge of FL immunobiology can inform risk stratification and therapy selection on a personalized basis for R/R FL in 2025.

Rapid response in relapsed follicular lymphoma to novel anti-CD19 CAR-T therapy with pseudo-progression and cytomegalovirus infection: A case report

CD19-directed chimeric antigen receptor (CAR) T cell therapy has been shown to achieve a considerably durable response in patients with refractory or relapsed B cell non-Hodgkin lymphomas. Most of these CARs were generated by lentivirus. With the exception of Yescarta and Tecartus, few patients with relapsed-/refractory- lymphoma have been treated clinically with a CARs using retroviral vector (RV). Here, we reported a relapsed/refractory grade 2 follicular lymphoma patient with multiple chemotherapy failures, and was treated with a novel CD19 CAR-T cell manufactured from a RV. After tumor burden was reduced with Obinutuzumab and Duvelisib, the patient was infused novel CD19 CAR-T cells at a dose of 3 × 106 cells/ kg. Then he experienced a rapid response and achieved almost complete remission by day 26. Only grade 2 CRS, bilateral submaxillary lymph node enlargement and cytomegalovirus (CMV) infection occurred without neurotoxicity, and the patient's condition improved after a series of symptomatic treatments. In addition, CAR copy number peaked at 532,350 copies/μg on day 15 and continued to expand for 5 months. This may be the first case report of RV preparation of novel CD19 CAR-T cells for direct treatment of recurrent follicular lymphoma. We will observe its long-term efficacy and conduct trials in more patients in the future.

Integrated single cell analysis reveals co-evolution of malignant B cells and tumor micro-environment in transformed follicular lymphoma

Histological transformation of follicular lymphoma (FL) to aggressive forms is associated with poor outcome. Phenotypic consequences of this evolution and its impact on the tumor microenvironment (TME) remain unknown. We perform single-cell whole genome sequencing (scWGS) and transcriptome sequencing (scWTS) of 11 paired pre/post-transformation patient samples and scWTS of additional samples from patients without transformation. Our analysis reveals evolutionary dynamics of transformation at single-cell resolution, highlighting a shifting TME landscape, with an emerging immune-cell exhaustion signature, co-evolving with the shifting malignant B phenotype in a regulatory ecosystem. Integration of scWGS and scWTS identifies malignant cell pathways upregulated during clonal tumor evolution. Using multi-color immunofluorescence, we transfer these findings to a TME-based transformation biomarker, subsequently validated in two independent pretreatment cohorts. Taken together, our results provide a comprehensive view of the combined genomic and phenotypic evolution of malignant cells during transformation and shifting crosstalk between malignant cells and the TME.

B-cell non-Hodgkin lymphomas

B-cell lymphomas occur with an incidence of 20 new cases per 100 000 people per year in high-income countries. They can affect any organ and are characterised by heterogeneous clinical presentations and courses, varying from asymptomatic, to indolent, to very aggressive cases. Since the topic of B-cell non-Hodgkin lymphomas was last reviewed in The Lancet in 2017, a deeper understanding of the biological background of this heterogeneous group of malignancies, the availability of new diagnostic methods, and the development and implementation of new targeted and immunotherapeutic approaches have improved our ability to treat patients. This Seminar provides an overview of the pathobiology, classification, and prognostication of B-cell non-Hodgkin lymphomas and summarises the current knowledge and standard of care regarding biology and clinical management of the most common subtypes of mature B-cell non-Hodgkin lymphomas. It also highlights new findings in deciphering the molecular background of disease development and the implementation of new therapeutic approaches, particularly those targeting the immune system.

Case report: Mutation evolution in a patient with TdT positive high grade B cell lymphoma with MYC and BCL2 rearrangements following the treatment of concurrent follicular lymphoma and diffuse large B-cell lymphoma

BACKGROUND

Concurrent follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL)was reported in some studies, while the diagnosis of TdT (terminal deoxynucleotydil transferase) positive high grade B cell lymphoma (HGBL) with MYC and BCL2 rearrangements ("double hit") transformed from FL/DLBCL has been rarely reported. Herein, we described the clinical features and mutation profiles of a case diagnosed with TdT positive "double hit" HGBL following the treatment of FL/DLBCL.

CASE PRESENTATION

This is a 43-year-old Chinese man who was diagnosed with low grade FL (account for 80%) combined with DLBCL (20%) at a stage of IVB. The patient presented with BCL2/IGH translocation without MYC rearrangement, as well as the expressions of CD20, CD19, CD10 and BCL2 at the initial diagnosis of FL/DLBCL. MYC rearrangement and TdT expression occurred after the treatment. The targeted sequencing revealed mutations in KMT2D, FOXO1, CREBBP, ATM, STAT6, BCL7A, DDX3X, MUC4, FGFR3, ARID5B, DDX11 and PRKCSH genes were the co-mutations shared by the FL/DLBCL and TdT positive "double hit" HGBL, while CCND3, BIRC6, ROBO1 and CHEK2 mutations specifically occurred after the treatment. The overall survival time was 37.8 and 17.8 months after the initial diagnosis of FL/DLBCL and TdT positive "double hit" HGBL, respectively.

CONCLUSION

This study reports a rare case of TdT positive "double hit" HGBL following the treatment of concurrent FL/DLBCL and highlights the mutation characteristics. Collectively, this study will help enrich the knowledge of TdT positive "double hit" HGBL transformed from FL/DLBCL.

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.

Follicular Lymphoma Presenting With Symptomatic Bone Involvement: A Clinicopathologic and Molecular Analysis of 16 Cases

Primary bone lymphoma (PBL) is rare and mostly represented by diffuse large B-cell lymphomas (DLBCL). Follicular lymphoma (FL), albeit commonly disseminating to the bone marrow, rarely presents primarily as bone lesions. Here, we studied 16 patients (12 men:4 women, median age 60 years) who presented with bone pain and/or skeletal radiologic abnormalities revealing bone FL. Lesions were multifocal in 11 patients (spine ± appendicular skeleton), and unifocal in 5 patients (femoral, tibial, or vertebral). An infiltrate of centrocytes and centroblasts (CD20+ CD5- CD10+ BCL2+ BCL6+) with abundant reactive T cells and an increased reticulin fibrosis massively replaced the marrow spaces between preserved bone trabeculae. The pattern was diffuse ± nodular, often with paratrabecular reinforcement and/or peripheral paratrabecular extension. Ki-67 was usually <15%. Two cases had necrosis. BCL2 rearrangement was demonstrated in 14 of 14 evaluable cases (with concomitant BCL6 rearrangement in one). High-throughput sequencing revealed BCL2, KMT2D, and TNFRSF14 to be the most frequently mutated genes. After staging, 5 qualified for PBL (3 limited stage) and 11 had stage IV systemic FL. All patients received rituximab ± polychemotherapy as firstline treatment, and 7 received local therapy (6 radiotherapy and 2 surgery). Three patients experienced transformation to DLBCL. At the last follow-up (15/16, median 48 months), 11 patients achieved complete remission, including all cases with PBL and most patients with limited extraosseous disease (3-year progression-free survival 71%). One patient died of unrelated cause (3-year overall survival 91%). FL may manifest as a localized or polyostotic bone disease. A minority represent PBL, whereas most reveal systemic disease.

Mutational, immune microenvironment, and clinicopathological profiles of diffuse large B-cell lymphoma and follicular lymphoma with BCL6 rearrangement

BCL6-rearrangement (BCL6-R) is associated with a favorable prognosis of follicular lymphoma (FL), but the mechanism is unknown. We analyzed the clinicopathological, immune microenvironment (immune checkpoint, immuno-oncology markers), and mutational profiles of 10 BCL6-R-positive FL, and 19 BCL6-R-positive diffuse large B-cell lymphoma (DLBCL) cases (both BCL2-R and MYC-R negative). A custom-made panel included 168 genes related to aggressive B-cell lymphomas and FL. FL cases were nodal, histological grade 3A in 70%, low Ki67; and had a favorable overall and progression-free survival. DLBCL cases were extranodal in 60%, IPI high in 63%, non-GCB in 60%, EBER-negative; and had a progression-free survival comparable to that of DLBCL NOS. The microenvironment had variable infiltration of M2-like tumor-associated macrophages (TAMs) that were CD163, CSF1R, LAIR1, PD-L1, and CD85A (LILRB3) positive; but had low IL10 and PTX3 expression. In comparison to FL, DLBCL had higher TAMs, IL10, and PTX3 expression. Both lymphoma subtypes shared a common mutational profile with mutations in relevant pathogenic genes such as KMT2D, OSBPL10, CREBBP, and HLA-B (related to chromatin remodeling, metabolism, epigenetic modification, and antigen presentation). FL cases were characterized by a higher frequency of mutations of ARID1B, ATM, CD36, RHOA, PLOD2, and PRPRD (p < 0.05). DLBCL cases were characterized by mutations of BTG2, and PIM1; and mutations of HIST1H1E and MFHAS1 to disease progression (p < 0.05). Interestingly, mutations of genes usually associated with poor prognosis, such as NOTCH1/2 and CDKN2A, were infrequent in both lymphoma subtypes. Some high-confidence variant calls were likely oncogenic, loss-of-function. MYD88 L265P gain-of-function was found in 32% of DLBCL. In conclusion, both BCL6-R-positive FL and BCL6-R-positive DLBCL had a common mutational profile; but also, differences. DLBCL cases had a higher density of microenvironment markers.

Pathogenic Variants Associated with Epigenetic Control and the NOTCH Pathway Are Frequent in Classic Hodgkin Lymphoma

Classic Hodgkin lymphoma (cHL) constitutes a B-cell neoplasm derived from germinal center lymphocytes. Despite high cure rates (80-90%) obtained with the current multiagent protocols, a significant proportion of cHL patients experience recurrences, characterized by a lower sensitivity to second-line treatments. The genomic background of chemorefractory cHL is still poorly understood, limiting personalized treatment strategies based on molecular features. In this study, using a targeted next-generation sequencing (NGS) panel specifically designed for cHL research, we compared chemosensitive and chemorefractory diagnostic tissue samples of cHL patients. Furthermore, we longitudinally examined paired diagnosis-relapsesamples of chemorefractory cHL in order to define patterns of dynamic evolution and clonal selection. Pathogenic variants in NOTCH1 and NOTCH2 genes frequently arise in cHL. Mutations in genes associated with epigenetic regulation (CREBBP and EP300) are particularly frequent in relapsed/refractory cHL. The appearance of novel clones characterized by mutations previously not identified at diagnosis is a common feature in cHL cases showing chemoresistance to frontline treatments. Our results expand current molecular and pathogenic knowledge of cHL and support the performance of molecular studies in cHL prior to the initiation of first-line therapies.

A Population-Based Family Case-Control Study of Sun Exposure and Follicular Lymphoma Risk

BACKGROUND

Epidemiologic evidence suggests an inverse association between sun exposure and follicular lymphoma risk.

METHODS

We conducted an Australian population-based family case-control study based on 666 cases and 459 controls (288 related, 171 unrelated). Participants completed a lifetime residence and work calendar and recalled outdoor hours on weekdays, weekends, and holidays in the warmer and cooler months at ages 10, 20, 30, and 40 years, and clothing types worn in the warmer months. We used a group-based trajectory modeling approach to identify outdoor hour trajectories over time and examined associations with follicular lymphoma risk using logistic regression.

RESULTS

We observed an inverse association between follicular lymphoma risk and several measures of high lifetime sun exposure, particularly intermittent exposure (weekends, holidays). Associations included reduced risk with increasing time outdoors on holidays in the warmer months [highest category OR = 0.56; 95% confidence interval (CI), 0.42-0.76; Ptrend < 0.01], high outdoor hours on weekends in the warmer months (highest category OR = 0.71; 95% CI, 0.52-0.96), and increasing time outdoors in the warmer and cooler months combined (highest category OR = 0.66; 95% CI, 0.50-0.91; Ptrend 0.01). Risk was reduced for high outdoor hour maintainers in the warmer months across the decade years (OR = 0.71; 95% CI, 0.53-0.96).

CONCLUSIONS

High total and intermittent sun exposure, particularly in the warmer months, may be protective against the development of follicular lymphoma.

IMPACT

Although sun exposure is not recommended as a cancer control policy, confirming this association may provide insights regarding the future control of this intractable malignancy.

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.

Machine learning models-based on integration of next-generation sequencing testing and tumor cell sizes improve subtype classification of mature B-cell neoplasms

Background

Next-generation sequencing (NGS) panels for mature B-cell neoplasms (MBNs) are widely applied clinically but have yet to be routinely used in a manner that is suitable for subtype differential diagnosis. This study retrospectively investigated newly diagnosed cases of MBNs from our laboratory to investigate mutation landscapes in Chinese patients with MBNs and to combine mutational information and machine learning (ML) into clinical applications for MBNs, especially for subtype classification.

Methods

Samples from the Catalogue Of Somatic Mutations In Cancer (COSMIC) database were collected for ML model construction and cases from our laboratory were used for ML model validation. Five repeats of 10-fold cross-validation Random Forest algorithm was used for ML model construction. Mutation detection was performed by NGS and tumor cell size was confirmed by cell morphology and/or flow cytometry in our laboratory.

Results

Totally 849 newly diagnosed MBN cases from our laboratory were retrospectively identified and included in mutational landscape analyses. Patterns of gene mutations in a variety of MBN subtypes were found, important to investigate tumorigenesis in MBNs. A long list of novel mutations was revealed, valuable to both functional studies and clinical applications. By combining gene mutation information revealed by NGS and ML, we established ML models that provide valuable information for MBN subtype classification. In total, 8895 cases of 8 subtypes of MBNs in the COSMIC database were collected and utilized for ML model construction, and the models were validated on the 849 MBN cases from our laboratory. A series of ML models was constructed in this study, and the most efficient model, with an accuracy of 0.87, was based on integration of NGS testing and tumor cell sizes.

Conclusions

The ML models were of great significance in the differential diagnosis of all cases and different MBN subtypes. Additionally, using NGS results to assist in subtype classification of MBNs by method of ML has positive clinical potential.

Case report: Clinicopathological and molecular characteristics of pediatric-type follicular lymphoma

Pediatric-type follicular lymphoma (PTFL) is a rare pediatric-type indolent B-cell lymphoma that clinicopathologically differs from adult lymphoma. Accurate diagnosis of PTFL, which is often challenging, is essential to avoid missed diagnosis, misdiagnosis, and overtreatment. To improve our understanding of PTFL, clinicopathological features, differential diagnosis, and molecular mutation characteristics of four patients of PTFL were analyzed using hematoxylin and eosin staining, immunohistochemistry, polymerase chain reaction, fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS). A relevant literature review was also performed. All four PTFL patients were male, with ages of 6, 18, 13, and 15 years, and had St. Jude stage I or III. Microscopic results showed that the structure of the lymph nodes was destroyed; the tumor follicles were enlarged and irregular; medium-large blastoid cells with a consistent shape were visible in tumor follicles, and the nucleus was round or oval; and the "starry sky" pattern was easily observed. Tumor cells expressed CD20, PAX-5, BCL6, and CD10. None of the tumor cells expressed BCL2, CD3, CD5, MUM1, and CyclinD1. CD21 showed dilated growth of a follicular dendritic cell network in tumor follicles. EBER genes were negative in all cases. FISH testing also showed negative BCL2 gene breaks and IRF4 gene breaks in all cases. NGS detected 12 related mutant genes, including KMT2D, CD79B, GNA13, MYD88, PCLO, TCF3, IRF8, MAP2K1, FOXO1, POLE, INPP5D, and FAT4. Two of the four patients had an IRF8 gene mutation, and one patient had a dual mutation of the MAP2K1 gene. Our study revealed the unique clinicopathological features and molecular mutational characteristics of PTFL, consolidated our understanding of PTFL, and identified other rare mutant genes, which may further contribute to the study of the molecular mechanism and differential diagnosis of PTFL.

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.

Leukemic phase follicular lymphoma in a young adult

BACKGROUND

Leukemic presentation of follicular lymphoma (FL) is uncommon, with most cases reported in older adults.

DESIGN

This report describes an unusual case of a young adult diagnosed with leukemic phase of FL. We reviewed the existing literature on this rare presentation of the disease and its potential impact on patient outcomes.

RESULTS

Leukemic phase of FL in young adults can be mistaken for other high-grade hematologic malignancies. Morphology assessment and ancillary testing, such as flow cytometry and FISH analysis, can assist in achieving an accurate diagnosis of the leukemic phase of FL. Notably, our young patient responded well to therapy, which is different from what is typically observed in older patients who have a poorer prognosis. Further cases are needed to investigate the prognostic impact of the leukemic phase of FL in younger patients.

Follicle Center Lymphoma (FCL) of the Lower Female Genital Tract (LFGT): A Novel Variant of Primary Cutaneous Follicle Center Lymphoma (PCFCL)

Primary cutaneous follicle center lymphoma has been distinguished from nodal follicular lymphoma (FL) based on genomic and clinical features. The nature of other extranodal FLs is not well defined. We report 15 cases of follicle center lymphoma involving the lower female genital tract. Cases were evaluated using an immunohistochemical panel for B-cell lymphoma, B-cell clonality, fluorescence in situ hybridization for BCL2 gene rearrangement, and next-generation sequencing. All patients had localized disease with no evidence of bone marrow involvement. Most cases (12/15, 80%) had a follicular pattern, at least focally. Large centrocytes were a prominent feature leading to concern for diffuse large B-cell lymphoma by referring pathologists. Neoplastic cells were positive for CD20 and BCL-6, while BCL-2 was positive in 2/15 (13%) cases. Fluorescence in situ hybridization for BCL2 gene rearrangement was negative in 10/11 (91%) cases. Next-generation sequencing performed in 10 cases revealed TNFRSF14 as the most frequently mutated gene in 6/10 (60%) cases. No case had CREBBP or KMT2D mutations as seen in nodal FL. None of the patients had progressive disease with durable complete remission achieved in 10/12 (83%) cases. The median follow-up period was 7.8 years (range: 0.2 to 20.5 y) with a 5-year overall survival of 100%. We conclude that follicle center lymphoma of the lower female genital tract is a novel variant of primary cutaneous follicle center lymphoma. Despite a frequent component of large cells, it is characterized by localized disease and low risk for dissemination. Awareness and recognition are important to distinguish these lesions from aggressive B-cell lymphomas.

Monitoring of Circulating Tumor DNA Predicts Response to Treatment and Early Progression in Follicular Lymphoma: Results of a Prospective Pilot Study

PURPOSE

Follicular lymphoma (FL) is the most frequent indolent non-Hodgkin lymphoma. Around 20% of patients suffer early disease progression within 24 months (POD24) of diagnosis. This study examined the significance of circulating tumor DNA (ctDNA) in predicting response to therapy and POD24 in patients with FL.

EXPERIMENTAL DESIGN

We collected 100 plasma samples, before and during the treatment, from 36 patients with FL prospectively enrolled in 8 Spanish hospitals. They were treated with a chemotherapy-rituximab regimen and followed up for a median of 3.43 years. We performed targeted deep sequencing in cell-free DNA (cfDNA) and tumor genomic DNA from 31 diagnostic biopsy samples.

RESULTS

Of the alterations detected in the diagnostic tissue samples, 73% (300/411) were also identified in basal cfDNA. The mean numbers of alterations per basal cfDNA sample in patients who suffered progression of disease within 24 months (POD24-pos) or did not achieve complete response (non-CR) were significantly higher than in POD24-neg or CR patients (unpaired samples t test, P = 0.0001 and 0.001, respectively). Pretreatment ctDNA levels, as haploid genome equivalents per milliliter of plasma, were higher in patients without CR (P = 0.02) and in POD24-pos patients compared with POD24-neg patients (P < 0.001). Dynamic analysis showed that ctDNA levels decreased dramatically after treatment, although the reduction was more significant in patients with CR and POD24-neg patients.

CONCLUSIONS

Basal ctDNA levels are associated with the risk of early progression and response to treatment in FL. cfDNA monitoring and genotyping during treatment and follow-up predict response to treatment and early progression.

Molecular characterization of an embryonal rhabdomyosarcoma occurring in a patient with Kabuki syndrome: report and literature review in the light of tumor predisposition syndromes

Kabuki syndrome is a well-recognized syndrome characterized by facial dysmorphism and developmental delay/intellectual disability and in the majority of patients a germline variant in KMT2D is found. As somatic KMT2D variants can be found in 5-10% of tumors a tumor predisposition in Kabuki syndrome is discussed. So far less than 20 patients with Kabuki syndrome and a concomitant malignancy have been published. Here we report on a female patient with Kabuki syndrome and a c.2558_2559delCT germline variant in KMT2D who developed an embryonal rhabdomyosarcoma (ERMS) at 10 years. On tumor tissue we performed DNA-methylation profiling and exome sequencing (ES). Copy number analyses revealed aneuploidies typical for ERMS including (partial) gains of chromosomes 2, 3, 7, 8, 12, 15, and 20 and 3 focal deletions of chromosome 11p. DNA methylation profiling mapped the case to ERMS by a DNA methylation-based sarcoma classifier. Sequencing suggested gain of the wild-type KMT2D allele in the trisomy 12. Including our patient literature review identified 18 patients with Kabuki syndrome and a malignancy. Overall, the landscape of malignancies in patients with Kabuki syndrome was reminiscent of that of the pediatric population in general. Histopathological and molecular data were only infrequently reported and no report included next generation sequencing and/or DNA-methylation profiling. Although we found no strong arguments pointing towards KS as a tumor predisposition syndrome, based on the small numbers any relation cannot be fully excluded. Further planned studies including profiling of additional tumors and long term follow-up of KS-patients into adulthood could provide further insights.

Application of circulating tumour DNA in terms of prognosis prediction in Chinese follicular lymphoma patients

Background: Follicular lymphoma (FL), an indolent non-Hodgkin lymphoma (NHL), is generally incurable. Favourable prognosis and durable remission are crucial for FL patients. The genetic mutation spectrum provides novel biomarkers for determining the prognosis of FL patients, but its detection is easily affected by the collection of tumour tissue biopsies. In this study, we aimed to describe the mutational landscape of FL using circulating tumour DNA (ctDNA) samples and to explore the relationship between mutations and prognostic indicators of clinical outcome in patients with newly diagnosed follicular lymphoma and the prognostic value of such mutations. Methods: A total of 28 patients with newly diagnosed FL were included in this study. A targeted NGS-based 59-gene panel was used to assess the ctDNA mutation profiles. Differences in clinical factors between patients carrying mutations and those without mutations were analysed. We also explored the relationship between gene mutation status, mean VAFs (variant allele frequencies) and clinical factors. The Kaplan‒Meier method was applied to analyse the overall survival (OS) and progression-free survival (PFS) of patients carrying mutations and those without mutations. Results: ctDNA mutations were detectable in 21 (75%) patients. The most commonly mutated genes were CREBBP (54%, 15/28), KMT2D (50%, 14/28), STAT6 (29%, 8/28), CARD11 (18%, 5/28), PCLO (14%, 4/28), EP300 (14%, 4/28), BCL2 (11%, 3/28), and TNFAIP3 (11%, 3/28), with a mutation frequency of >10%. Patients with detectable ctDNA mutation tended to present with advanced Ann Arbor stage (III-IV) (p = 0.009), high FLIPI risk (3-5) (p = 0.023) and severe lymph node involvement (No. of involved areas ≥5) (p = 0.02). In addition, we found that the mean VAF was significantly higher in patients with advanced Ann Arbor stage, high-risk FLIPI, elevated lactate dehydrogenase (LDH: 0-248U/L), advanced pathology grade, bone marrow involvement (BMI) and lymph node involvement. Additionally, KMT2D, EP300, and STAT6 mutations were associated with inferior PFS (p < 0.05). Conclusion: We described the ctDNA mutation landscapes in Chinese patients with newly diagnosed FL and found that ctDNA VAF means reflect tumour burden. Moreover, PFS was shorter in patients with KMT2D, EP300 and STAT6 mutations.

Follicular lymphoma: 2023 update on diagnosis and management

DISEASE OVERVIEW

Follicular lymphoma (FL) is generally an indolent B cell lymphoproliferative disorder of transformed follicular center B cells. FL is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. Extranodal involvement is less common. Cytopenias are relatively common but constitutional symptoms of fever, night sweats, and weight loss are uncommon in the absence of transformation to diffuse large B cell lymphoma.

DIAGNOSIS

The diagnosis is based on histology from a biopsy of a lymph node or other affected tissue. Incisional biopsy is preferred over needle biopsies in order to give adequate tissue to assign grade and assess for transformation. Immunohistochemical staining is positive in virtually all cases for cell surface CD19, CD20, CD10, and monoclonal immunoglobulin, as well as cytoplasmic expression of bcl-2 protein. The overwhelming majority of cases have the characteristic t(14;18) translocation involving the IgH/bcl-2 genes.

RISK STRATIFICATION

The Follicular Lymphoma International Prognostic Index (FLIPI) uses five independent predictors of inferior survival: age >60 years, hemoglobin <12 g/dL, serum LDH > normal, Ann Arbor stage III/IV, number of involved nodal areas >4. The presence of 0-1, 2, and ≥3 adverse factors defines low, intermediate, and high-risk disease. There are other clinical prognostic models but the FLIPI remains the most common. Other factors such as time to relapse of less than 2 years from chemoimmunotherapy and specific gene mutations may also be useful for prognosis. Regardless of the prognostic model used, modern therapies have demonstrably improved prognosis.

RISK-ADAPTED THERAPY

Observation continues to be appropriate for asymptomatic patients with low bulk disease and no cytopenias. There is no overall survival (OS) advantage for early treatment with either chemotherapy or single-agent rituximab. For patients needing therapy, most patients are treated with chemoimmunotherapy, which has improved overall response rates (ORR), DOR, and OS. Randomized studies have shown additional benefits for maintenance of rituximab. Lenalidomide was non-inferior to chemoimmunotherapy in a randomized front-line study and, when combined with rituximab, was superior to rituximab alone in relapsed FL. Kinase inhibitors, stem cell transplantation (SCT), and chimeric antigen receptor T cells (CAR-T) are also considered for recurrent disease.

Panel Sequencing of Primary Cutaneous B-Cell Lymphoma

Background: Primary cutaneous follicular B-cell lymphoma (PCFBCL) represents an indolent subtype of Non-Hodgkin’s lymphomas, being clinically characterized by slowly growing tumors of the skin and common cutaneous relapses, while only exhibiting a low propensity for systemic dissemination or fatal outcome. Up to now, only few studies have investigated underlying molecular alterations of PCFBCL with respect to somatic mutations. Objectives: Our aim was to gain deeper insight into the pathogenesis of PCFBCL and to delineate discriminatory molecular features of this lymphoma subtype. Methods: We performed hybridization-based panel sequencing of 40 lymphoma-associated genes of 10 cases of well-characterized PCFBCL. In addition, we included two further ambiguous cases of atypical B-cell-rich lymphoid infiltrate/B-cell lymphoma of the skin for which definite subtype attribution had not been possible by routine investigations. Results: In 10 out of 12 analyzed cases, we identified genetic alterations within 15 of the selected 40 target genes. The most frequently detected alterations in PCFBCL affected the TNFRSF14, CREBBP, STAT6 and TP53 genes. Our analysis unrevealed novel mutations of the BCL2 gene in PCFBCL. All patients exhibited an indolent clinical course. Both the included arbitrary cases of atypical B-cell-rich cutaneous infiltrates showed somatic mutations within the FAS gene. As these mutations have previously been designated as subtype-specific recurrent alterations in primary cutaneous marginal zone lymphoma (PCMZL), we finally favored the diagnosis of PCMZL in these two cases based on these molecular findings. Conclusions: To conclude, our molecular data support that PCFBCL shows distinct somatic mutations which may aid to differentiate PCFBCL from pseudo-lymphoma as well as from other indolent and aggressive cutaneous B-cell lymphomas. While the detected genetic alterations of PCFBCL did not turn out to harbor any prognostic value in our cohort, our molecular data may add adjunctive discriminatory features for diagnostic purposes on a molecular level.

Lymphoma Microenvironment in DLBCL and PTCL-NOS: the key to uncovering heterogeneity and the potential for stratification

Diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) are the most common subtypes of mature B cell neoplasm and T/NK cell lymphoma, respectively. They share a commonality in that they are, by definition, highly heterogeneous populations. Recent studies are revealing more about the heterogeneity of these diseases, and at the same time, there is an active debate on how to stratify these heterogeneous diseases and make them useful in clinical practice. The various immune cells and non-cellular components surrounding lymphoma cells, i.e., the lymphoma microenvironment, have been the subject of intense research since the late 2000s, and much knowledge has been accumulated over the past decade. As a result, it has become clear that the lymphoma microenvironment, despite its paucity in tissues, significantly impacts the lymphoma pathogenesis and clinical behavior, such as its prognosis and response to therapy. In this article, we review the role of the lymphoma microenvironment in DLBCL and PTCL-NOS, with particular attention given to its impact on the prognosis and stratification.

Genomic and microenvironmental landscape of stage I follicular lymphoma, compared with stage III/IV

Although the genomic and immune microenvironmental landscape of follicular lymphoma (FL) has been extensively investigated, little is known about the potential biological differences between stage I and stage III/IV disease. Using next-generation sequencing and immunohistochemistry, 82 FL nodal stage I cases were analyzed and compared with 139 FL stage III/IV nodal cases. Many similarities in mutations, chromosomal copy number aberrations, and microenvironmental cell populations were detected. However, there were also significant differences in microenvironmental and genomic features. CD8+ T cells (P = .02) and STAT6 mutations (false discovery rate [FDR] <0.001) were more frequent in stage I FL. In contrast, programmed cell death protein 1-positive T cells, CD68+/CD163+ macrophages (P < .001), BCL2 translocation (BCL2trl+) (P < .0001), and KMT2D (FDR = 0.003) and CREBBP (FDR = 0.04) mutations were found more frequently in stage III/IV FL. Using clustering, we identified 3 clusters within stage I, and 2 clusters within stage III/IV. The BLC2trl+ stage I cluster was comparable to the BCL2trl+ cluster in stage III/IV. The two BCL2trl- stage I clusters were unique for stage I. One was enriched for CREBBP (95%) and STAT6 (64%) mutations, without BLC6 translocation (BCL6trl), whereas the BCL2trl- stage III/IV cluster contained BCL6trl (64%) with fewer CREBBP (45%) and STAT6 (9%) mutations. The other BCL2trl- stage I cluster was relatively heterogeneous with more copy number aberrations and linker histone mutations. This exploratory study shows that stage I FL is genetically heterogeneous with different underlying oncogenic pathways. Stage I FL BCL2trl- is likely STAT6 driven, whereas BCL2trl- stage III/IV appears to be more BCL6trl driven.

The metabolic plasticity of B cells

The humoral response requires rapid growth, biosynthetic capacity, proliferation and differentiation of B cells. These processes involve profound B-cell phenotypic transitions that are coupled to drastic changes in metabolism so as to meet the extremely different energetic requirements as B cells switch from resting to an activated, highly proliferative state and to plasma or memory cell fates. Thus, B cells execute a multi-step, energetically dynamic process of profound metabolic rewiring from low ATP production to transient and large increments of energy expenditure that depend on high uptake and consumption of glucose and fatty acids. Such metabolic plasticity is under tight transcriptional and post-transcriptional regulation. Alterations in B-cell metabolism driven by genetic mutations or by extrinsic insults impair B-cell functions and differentiation and may underlie the anomalous behavior of pathological B cells. Herein, we review molecular switches that control B-cell metabolism and fuel utilization, as well as the emerging awareness of the impact of dynamic metabolic adaptations of B cells throughout the different phases of the humoral response.

EZH2 mutations at diagnosis in follicular lymphoma: a promising biomarker to guide frontline treatment

EZH2 is mutated in nearly 25% of follicular lymphoma (FL) cases. Little is known about how EZH2 affects patients’ response to therapy. In this context, the aim of this study was to retrospectively analyze the frequency of mutations in EZH2 at diagnosis in tissue and ctDNA in patients with FL and to assess the patients’ outcomes after receiving immunochemotherapy, depending on the EZH2 mutation status. Among the 154 patients included in the study, 27% had mutated EZH2 (46% with high-grade and 26% with low-grade FL). Of the mutated tissue samples, the mutation in ctDNA was identified in 44% of cases. EZH2 mutation in ctDNA was not identified in any patient unmutated in the tissue.

Unmutated patients who received R-CHOP had significantly more relapses than patients who received R-Bendamustine (16/49 vs. 2/23, p = 0.040). Furthermore, our results show that patients with mutated EZH2 treated with R-CHOP vs. those treated with R-Bendamustine present a lower incidence of relapse (10% vs. 42% p = 0.09 at 4 years), a higher PFS (92% vs. 40% p = 0.039 at 4 years), and higher OS (100% vs. 78% p = 0.039 at 4 years). Based on these data, RCHOP could be a more suitable regimen for mutated patients, and R-bendamustine for unmutated patients. These findings could mean the first-time identification of a useful biomarker to guide upfront therapy in FL.

Follicular Lymphoma Microenvironment Characteristics Associated with Tumor Cell Mutations and MHC Class II Expression

Follicular lymphoma (FL) is a B-cell malignancy with a complex tumor microenvironment that is rich in nonmalignant immune cells. We applied single-cell RNA sequencing to characterize the diverse tumor and immune cell populations of FL and identified major phenotypic subsets of FL T cells, including a cytotoxic CD4 T-cell population. We characterized four major FL subtypes with differential representation or relative depletion of distinct T-cell subsets. By integrating exome sequencing, we observed that somatic mutations are associated with, but not definitive for, reduced MHC expression on FL cells. In turn, expression of MHCII genes by FL cells was associated with significant differences in the proportions and targetable immunophenotypic characteristics of T cells. This provides a classification framework of the FL microenvironment in association with FL genotypes and MHC expression, and informs different potential immunotherapeutic strategies based upon tumor cell MHCII expression.

SIGNIFICANCE

We have characterized the FL-infiltrating T cells, identified cytotoxic CD4 T cells as an important component that is associated with tumor cell-intrinsic characteristics, and identified sets of targetable immune checkpoints on T cells that differed from FLs with normal versus low MHC expression. See related commentary by Melnick, p. 374. This article is highlighted in the In This Issue feature, p. 369.

CD4+/CD57+/CD69+ T lymphocytes and CD14+ dendritic cells accumulate in advanced follicular lymphoma

Follicular lymphoma is the second most frequent non-Hodgkin's lymphoma, accounting for around 20 % of all lymphomas in Western countries. Initially, it behaves indolently, but in time becomes more aggressive and less susceptible to chemotherapy. Multiple features correlate with the survival of the patients and the progression of the disease, such as therapy with rituximab, tumour microenvironment and the intrafollicular proliferation index. Our research was focused on the association of specific components of tumour microenvironment and the tumour behaviour. The presence and the relative percentage of T lymphocytes, follicular dendritic cells, dendritic cells and macrophages was detected by immunohistochemical staining of the antigens specific for certain cell populations. Our results show that T lymphocytes and dendritic cells affect tumour growth, possibly through interactions with tumour cells. Higher patients' ECOG score and the outcome of the disease are associated with the presence of CD14+ dendritic cells in tumour tissue, while the worse overall survival of patients is associated with the increased number of activated helper T lymphocytes that express marker of exhaustion CD57. Taken together, our results suggest that the efficiency of the immune response against follicular lymphoma depends on more than one type of immune cells. Also, we found that the phenotype of these cells, rather than just their number, affects the tumour behaviour and in consequence survival of the patients.

A Promising Future for Precision Epigenetic Therapy for Follicular and Diffuse Large B-Cell Lymphoma?

Epigenetic mechanisms such as DNA hypermethylation or histone deacetylation normally silence gene expression that regulates numerous cellular activities. Germinal center–derived lymphomas such as follicular lymphoma (FL) and diffuse large B cell lymphoma (DLBCL) are characterized by frequent mutations of histone-modifying genes. EZH2 is essential to the formation of germinal center in the secondary lymphoid tissue (eg, lymph nodes and spleen) and is one of the most frequently mutated histone-modifying genes in human lymphomas. EZH2 encodes a histone methyltransferase, mediates transcriptional repression and acts as an oncogene that promotes the development and progression of a variety of human malignancies, including FL and DLBCL. Thus, recurrent mutations in the EZH2 and other non-histone epigenetic regulators represent important targets for therapeutic interventions. Recently, an orally active inhibitor of EZH2, tazemetostat, has received regulatory approval for patients with mutated EZH2 relapsed or refractory FL after ≥2 prior systemic therapies. It is also approved for those with relapsed or refractory FL who have no satisfactory alternative treatment options, regardless of their mutational status of EZH2. Currently, tazemetostat and its combination therapies for patients with relapsed or refractory germinal center-derived lymphomas, as well as frontline therapies for previously untreated patients, are in various phases of clinical investigations. Despite the promise of epigenetic therapies, potential pitfalls such as target selectivity, risk of oncogenic activation, risk of secondary malignancies associated with epigenetic therapies must be carefully monitored. Future applications of epigenetic approach that incorporate clinical and genomic features are needed to determine how individualized treatments can be used for these hematologic malignancies.

m6A-Regulator Expression Signatures Identify a Subset of Follicular Lymphoma Harboring an Exhausted Tumor Microenvironment

The role of N6-methyladenosine (m6A) modification in tumor microenvironment has rarely been explored in follicular lymphoma (FL). To examine the role of m6A modification in biological behavior, especially the immune landscape of FL, we utilized the Gene Expression Omnibus database to determine the expression signatures of m6A-regulators by unsupervised clustering, and then condense into a risk score, which was validated in an external cohort from the Tianjin Medical University Cancer Institute and Hospital. Finally, 16 m6A-regulators in 351 FL patients were evaluated and two m6A clusters were identified, characterized by differences in prognosis and biological behaviors. The m6A score was further developed based on 20-genes to quantify the m6A-regulator expression signature in each patient with FL. The low m6A score was associated with inferior prognosis of patients, with a median survival time of 8.84 (95% confidence interval [CI]: 7.251-10.429) years, which was remarkably shorter than that of patients with high m6A scores (15.73 years, 95% CI: 11.729-19.731; p&lt;0.0001). Genes like TNFRSF14, CREBBP, and CARD11 were shown to be more often mutated in the low m6A group. This group was enriched with immune/inflammatory response but along with the abundant infiltration of exhausted T cells and the upregulated PD-1 and PD-L1 expression. Finally, we verified the m6A score could predict the response to anti-PD-L1 antibodies in an immunotherapy cohort. To conclude, the m6A score recognizes a section of FL patients harboring an exhausted tumor microenvironment and may help guide more effective immunotherapy strategies for patients with FL.

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.

Targeted Therapy for Relapsed/Refractory Follicular Lymphoma: Focus on Clinical Utility of Tazemetostat

The management of follicular lymphoma (FL) in the relapsed and refractory setting is challenging and an area of ongoing investigation. Epigenetic dysregulation has recently been shown to be a hallmark of FL. Mutations in histone-modifying genes are likely early, driver events in FL pathogenesis, and so are attractive targets to drug. Gain-of-function mutations in the histone methyltransferase EZH2 are common in FL and maintained through disease evolution. With mounting data supporting a critical role for EZH2 as an oncogenic driver for FL, the small molecule inhibitor, tazemetostat, was developed. Tazemetostat has shown promising activity in preclinical models and early phase trials. Importantly, responses were seen in patients with high-risk features. Based on these data, tazemetostat was approved in the US in 2020 for EZH2^mut patients with FL who had received at least two prior lines of systemic therapy, or for EZH2^wt patients without alternative treatment options. Here, we will review the biology of FL as it pertains to tazemetostat, the available clinical trial data, and future directions for this new therapy.

Epigenetic, Metabolic, and Immune Crosstalk in Germinal-Center-Derived B-Cell Lymphomas: Unveiling New Vulnerabilities for Rational Combination Therapies

B-cell non-Hodgkin lymphomas (B-NHLs) are highly heterogenous by genetic, phenotypic, and clinical appearance. Next-generation sequencing technologies and multi-dimensional data analyses have further refined the way these diseases can be more precisely classified by specific genomic, epigenomic, and transcriptomic characteristics. The molecular and genetic heterogeneity of B-NHLs may contribute to the poor outcome of some of these diseases, suggesting that more personalized precision-medicine approaches are needed for improved therapeutic efficacy. The germinal center (GC) B-cell like diffuse large B-cell lymphomas (GCB-DLBCLs) and follicular lymphomas (FLs) share specific epigenetic programs. These diseases often remain difficult to treat and surprisingly do not respond advanced immunotherapies, despite arising in secondary lymphoid organs at sites of antigen recognition. Epigenetic dysregulation is a hallmark of GCB-DLBCLs and FLs, with gain-of-function (GOF) mutations in the histone methyltransferase EZH2, loss-of-function (LOF) mutations in histone acetyl transferases CREBBP and EP300, and the histone methyltransferase KMT2D representing the most prevalent genetic lesions driving these diseases. These mutations have the common effect to disrupt the interactions between lymphoma cells and the immune microenvironment, via decreased antigen presentation and responsiveness to IFN-γ and CD40 signaling pathways. This indicates that immune evasion is a key step in GC B-cell lymphomagenesis. EZH2 inhibitors are now approved for the treatment of FL and selective HDAC3 inhibitors counteracting the effects of CREBBP LOF mutations are under development. These treatments can help restore the immune control of GCB lymphomas, and may represent optimal candidate agents for more effective combination with immunotherapies. Here, we review recent progress in understanding the impact of mutant chromatin modifiers on immune evasion in GCB lymphomas. We provide new insights on how the epigenetic program of these diseases may be regulated at the level of metabolism, discussing the role of metabolic intermediates as cofactors of epigenetic enzymes. In addition, lymphoma metabolic adaptation can negatively influence the immune microenvironment, further contributing to the development of immune cold tumors, poorly infiltrated by effector immune cells. Based on these findings, we discuss relevant candidate epigenetic/metabolic/immune targets for rational combination therapies to investigate as more effective precision-medicine approaches for GCB lymphomas.

Follicular lymphoma: updates for pathologists

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and originates from germinal center B-cells (centrocytes and centroblasts) of the lymphoid follicle. Tumorigenesis is believed to initiate early in precursor B-cells in the bone marrow (BM) that acquire the t(14;18)(q32;q21). These cells later migrate to lymph nodes to continue their maturation through the germinal center reaction, at which time they acquire additional genetic and epigeneticabnormalities that promote lymphomagenesis. FLs are heterogeneous in terms of their clinicopathologic features. Most FLs are indolent and clinically characterized by peripheral lymphadenopathy with involvement of the spleen, BM, and peripheral blood in a substantial subset of patients, sometimes accompanied by constitutional symptoms and laboratory abnormalities. Diagnosis is established by the histopathologic identification of a B-cell proliferation usually distributed in an at least partially follicular pattern, typically, but not always, in a lymph node biopsy. The B-cell proliferation is biologically of germinal center cell origin, thus shows an expression of germinal center-associated antigens as detected by immunophenotyping. Although many cases of FLs are typical and histopathologic features are straightforward, the biologic and histopathologic variability of FL is wide, and an accurate diagnosis of FL over this disease spectrum requires knowledge of morphologic variants that can mimic other lymphomas, and rarely non-hematologic malignancies, clinically unique variants, and pitfalls in the interpretation of ancillary studies. The overall survival for most patients is prolonged, but relapses are frequent. The treatment landscape in FL now includes the application of immunotherapy and targeted therapy in addition to chemotherapy.

Incorporation of next-generation sequencing in clinical practice using solid and liquid biopsy for patients with non-Hodgkin's lymphoma

Although next-generation sequencing (NGS) data on lymphomas require further validation before being implemented in daily practice, the clinical application of NGS can be considered right around the corner. The aim of our study was to validate an NGS lymphoid panel for tissue and liquid biopsy with the most common types of non-Hodgkin’s lymphoma [follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL)]. In this series, 372 somatic alterations were detected in 93.6% (44/47) of the patients through tissue biopsy. In FL, we identified 93 somatic alterations, with a median of 7.4 mutations per sample. In DLBCL, we detected 279 somatic variants with a median of 8.6 mutations (range 0–35). In 92% (24/26) of the cases, we were able to detect some variant in the circulating tumor DNA. We detected a total of 386 variants; 63.7% were detected in both types of samples, 13.2% were detected only in the circulating tumor DNA, and 23% were detected only in the tissue biopsy. We found a correlation between the number of circulating tumor DNA mutations, advanced stage, and bulky disease. The genetic alterations detected in this panel were consistent with those previously described at diagnosis. The liquid biopsy sample is therefore a complementary tool that can provide new genetic information, even in cases where a solid biopsy cannot be performed or an insufficient sample was obtained. In summary, we describe and analyze in this study the findings and difficulties encountered when incorporating liquid biopsy into clinical practice in non-Hodgkin’s lymphoma at diagnosis.

Low CCL19 expression is associated with adverse clinical outcomes for follicular lymphoma patients treated with chemoimmunotherapy

Background

This study aimed to recognize the hub genes associated with prognosis in follicular lymphoma (FL) treated with first-line rituximab combined with chemotherapy.

Method

RNA sequencing data of dataset GSE65135 (n = 24) were included in differentially expressed genes (DEGs) analysis. Weighted gene co-expression network analysis (WGCNA) was applied for exploring the coexpression network and identifying hub genes. Validation of hub genes expression and prognosis were applied in dataset GSE119214 (n = 137) and independent patient cohort from Cancer Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College (n = 32), respectively, by analyzing RNAseq expression data and serum protein concentration quantified by ELISA. The Gene Set Enrichment Analysis (GSEA), gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments analysis were performed. CIBERSORT was applied for tumor-infiltrating immune cells (TIICs) subset analysis.

Results

A total of 3260 DEGs were obtained, with 1861 genes upregulated and 1399 genes downregulated. Using WGCNA, eight hub genes, PLA2G2D, MMP9, PTGDS, CCL19, NFIB, YAP1, RGL1, and TIMP3 were identified. Kaplan–Meier analysis and multivariate COX regression analysis indicated that CCL19 independently associated with overall survival (OS) for FL patients treated with rituximab and chemotherapy (HR = 0.47, 95% CI [0.25–0.86], p = 0.014). Higher serum CCL19 concentration was associated with longer progression-free survival (PFS, p = 0.014) and OS (p = 0.039). TIICs subset analysis showed that CCL19 expression had a positive correlation with monocytes and macrophages M1, and a negative correlation with naïve B cells and plasma cells.

Conclusion

CCL19 expression was associated with survival outcomes and might be a potential prognostic biomarker for FL treated with first-line chemoimmunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03078-9.

Simultaneous Follicular Lymphoma and Myelofibrosis: Report of a Case with Review of the Literature

Background

Myelofibrosis (MF) is often associated with chronic myeloid leukemia, myelodysplastic syndrome and primary myeloproliferative neoplasms (MPN), but few number cases of malignant lymphoma with myelofibrosis was reported, and a few cases about follicular lymphoma with MF were found. Here we described a case of follicular lymphoma (FL) complicated by myelofibrosis.

Case Presentation

A 43-year-old man was diagnosed with follicular lymphoma (FL) complicated by MF, besides, the lymphoma staging of this patient was AnnArbor IV B. The cytokines of plated-derived growth factor (PDGF), basic fibroblast growth factor (b-FGF), vascular endothelial growth factor (VEGF), tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), interleukin-2 (IL-2), and transforming growth factor-β (TGF-β) were positive, while JAK2V617F, MPL, and CALR mutations were negative. After first course of chemotherapy, the peripheral blood and MF improved. The systemic superficial lymph nodes and spleen were significantly narrowed after the third cycle of chemotherapy.

Conclusion

The production of various cytokines, such as b-FGF, TNF-α, TGF-β, PDGF, IL-1β, IL-2, IL-6, IL-10, may contribute to the development of MF.

Follicular lymphoma: an update on diagnosis, prognosis, and management

Follicular lymphoma, the most common indolent lymphoma, originates from germinal centre B-cells of the lymphoid follicle, and is characterized by t(14;18). Clinical manifestations include the presence of lymphadenopathy, sometimes accompanied by constitutional symptoms or cytopenia. Diagnosis is established through the identification of a B-cell proliferation of nodular pattern in the lymph node biopsy. Upon staging with PET-CT and bone marrow biopsy, a significant proportion of patients do not need immediate treatment. When therapy is indicated, commonly used regimens include anti-CD20 immunotherapy with or without chemotherapy. Although overall survival for most patients is prolonged, relapses are very frequent, and early relapse and transformation to an aggressive lymphoma portend a much worse prognosis. New therapies are under development, which will most likely change outcomes for FL patients in the near future.

The MLL3/4 H3K4 methyltransferase complex in establishing an active enhancer landscape

Enhancers are cis-regulatory elements that play essential roles in tissue-specific gene expression during development. Enhancer function in the expression of developmental genes requires precise regulation, while deregulation of enhancer function could be the main cause of tissue-specific cancer development. MLL3/KMT2C and MLL4/KMT2D are two paralogous histone modifiers that belong to the SET1/MLL (also named COMPASS) family of lysine methyltransferases and play critical roles in enhancer-regulated gene activation. Importantly, large-scale DNA sequencing studies have revealed that they are amongst the most frequently mutated genes associated with human cancers. MLL3 and MLL4 form identical multi-protein complexes for modifying mono-methylation of histone H3 lysine 4 (H3K4) at enhancers, which together with the p300/CBP-mediated H3K27 acetylation can generate an active enhancer landscape for long-range target gene activation. Recent studies have provided a better understanding of the possible mechanisms underlying the roles of MLL3/MLL4 complexes in enhancer regulation. Moreover, accumulating studies offer new insights into our knowledge of the potential role of MLL3/MLL4 in cancer development. In this review, we summarize recent evidence on the molecular mechanisms of MLL3/MLL4 in the regulation of active enhancer landscape and long-range gene expression, and discuss their clinical implications in human cancers.

Vulnerabilities in the tumor and microenvironment in follicular lymphoma

Follicular lymphoma (FL) is a paradigm of tumors that require the interaction between tumor and microenvironment cells to foster their development from initial steps to progression. Recent large-scale genome studies have uncovered multiple genetic alterations of FL that influence the microenvironment in two main directions, promoting tumor cell survival and proliferation and facilitating their evasion from immune antitumor signals. Understanding the crosstalk between tumor B-cells and the microenvironment will facilitate the identification of vulnerabilities that may offer novel targets for treatment of the patients. This review highlights recent findings showing the effect of common genetic mutations modulating the cell composition of the tumor microenvironment and the novel therapeutic perspectives to target these interactions.

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.

B cell/stromal cell crosstalk in health, disease, and treatment: Follicular lymphoma as a paradigm

Stromal cells organize specific anatomic compartments within bone marrow (BM) and secondary lymphoid organs where they finely regulate the behavior of mature normal B cells. In particular, lymphoid stromal cells (LSCs) form a phenotypically heterogeneous compartment including various cell subsets variably supporting B-cell survival, activation, proliferation, and differentiation. In turn, activated B cells trigger in-depth remodeling of LSC networks within lymph nodes (LN) and BM. Follicular lymphoma (FL) is one of the best paradigms of a B-cell neoplasia depending on a specific tumor microenvironment (TME), including cancer-associated fibroblasts (CAFs) emerging from the reprogramming of LN LSCs or poorly characterized local BM precursors. FL-CAFs support directly malignant B-cell growth and orchestrate FL permissive cell niche by contributing, through a bidirectional crosstalk, to the recruitment and polarization of immune TME subsets. Recent studies have highlighted a previously unexpected level of heterogeneity of both FL B cells and FL TME, underlined by FL-CAF plasticity. A better understanding of the signaling pathways, molecular mechanisms, and kinetic of stromal cell remodeling in FL would be useful to delineate new predictive markers and new therapeutic approaches in this still fatal malignancy.

Genomic landscape of cutaneous follicular lymphomas reveals 2 subgroups with clinically predictive molecular features

Primary cutaneous follicle center lymphomas (PCFCLs) are indolent B-cell lymphomas that predominantly remain skin restricted and manageable with skin-directed therapy. Conversely, secondary cutaneous involvement by usual systemic follicular lymphoma (secondary cutaneous follicular lymphoma [SCFL]) has a worse prognosis and often necessitates systemic therapy. Unfortunately, no histopathologic or genetic features reliably differentiate PCFCL from SCFL at diagnosis. Imaging may miss low-burden internal disease in some cases of SCFLs, leading to misclassification as PCFCL. Whereas usual systemic FL is well characterized genetically, the genomic landscapes of PCFCL and SCFL are unknown. Herein, we analyzed clinicopathologic and immunophenotypic data from 30 cases of PCFCL and 10 of SCFL and performed whole-exome sequencing on 18 specimens of PCFCL and 6 of SCFL. During a median follow-up of 7 years, 26 (87%) of the PCFCLs remained skin restricted. In the remaining 4 cases, systemic disease developed within 3 years of diagnosis. Although the SCFLs universally expressed BCL2 and had BCL2 rearrangements, 73% of the PCFCLs lacked BCL2 expression, and only 8% of skin-restricted PCFCLs had BCL2 rearrangements. SCFLs showed low proliferation fractions, whereas 75% of PCFCLs had proliferation fractions >30%. Of the SCFLs, 67% had characteristic loss-of-function CREBBP or KMT2D mutations vs none in skin-restricted PCFCL. Both SCFL and skin-restricted PCFCL showed frequent TNFRSF14 loss-of-function mutations and copy number loss at chromosome 1p36. These data together establish PCFCL as a unique entity with biological features distinct from usual systemic FL and SCFL. We propose 3 criteria based on BCL2 rearrangement, chromatin-modifying gene mutations (CREBBP, KMT2D, EZH2, and EP300), and proliferation index to classify cutaneous FL specimens based on the likelihood of concurrent or future systemic spread.

The role of tazemetostat in relapsed/refractory follicular lymphoma

Large strides have been made in the treatment of follicular lymphoma (FL) over the last few years. Although the majority of patients respond to upfront therapy, many experience disease progression with a progressive shortening of subsequent treatment free intervals. New treatment options are therefore crucial for such patients. Tazemetostat is a first-in-class, selective, oral inhibitor of enhancer of zester homolog 2 (EZH2), a histone methyltransferase that is mutated in about a quarter of FL cases. Tazemetostat was recently approved for the treatment of patients with relapsed FL after 2 or more prior lines of therapy in the presence of an EZH2 mutation and for those without any other available therapeutic option, independently of EZH2 mutation status. In this review, we will summarize the background and key data that led to the development of tazemetostat, and, ultimately, to its approval for this indication.

Epigenetics of Indolent Lymphoma and How It Drives Novel Therapeutic Approaches-Focus on EZH2-Targeted Drugs

Purpose of Review

Epigenetic modifier gene mutations are common in patients with follicular lymphoma. Here we review the pathogenesis of these mutations and how they are targeted by epigenetic drugs including EZH2 inhibitors in both mutated and wild-type disease.

Recent Findings

The use of EZH2 inhibitor tazematostat in early phase clinical trials has proved encouraging in the treatment of follicular lymphoma harbouring an EZH2 mutation; however, responses are also seen in patients with wild-type disease which is partially explained by the off target effects of EZH2 inhibition on immune cells within the tumour microenvironment.

Summary

Further studies incorporating prospective molecular profiling are needed to allow stratification of patients at both diagnosis and relapse to further our understanding of how epigenetic modifier mutations evolve over time. The use of tazematostat in combination or upfront in patients with an EZH2 mutation remains unanswered; however, given durable responses, ease of oral administration, and tolerability, it is certainly an attractive option.