Summary
Follicular lymphoma (FL) represents a heterogeneous disease both clinically and biologically. The pathognomonic t(14;18) translocation can no longer be thought of as the primary genetic ...driver, with increasing recognition of the biological relevance of recurrent genetic alterations in epigenetic regulators that now feature as a pivotal hallmark of this lymphoma subtype. Furthermore, sequencing studies have provided a near complete catalogue of additional genetic aberrations. Longitudinal and spatial genetic studies add an additional layer to the biological heterogeneity, providing preliminary molecular insights into high‐risk phenotypes such as early progressors and transformation, and also supporting evidence for the existence of persisting re‐populating cells that act as lymphoma reservoirs and harbingers for FL recurrence. Simultaneously, understanding of the tumour microenvironmental cues promoting lymphomagenesis and disease progression continue to broaden. More recently, studies are beginning to unravel the convergence and co‐operation between the genetics, epigenetics and microenvironment. There is a pressing need to marry biology with therapeutics, especially with the burgeoning treatment landscape in FL, to aid in optimising patient selection and guiding the ‘right drug to the right patient’.
Follicular lymphoma is an incurable malignancy, with transformation to an aggressive subtype representing a critical event during disease progression. Here we performed whole-genome or whole-exome ...sequencing on 10 follicular lymphoma-transformed follicular lymphoma pairs followed by deep sequencing of 28 genes in an extension cohort, and we report the key events and evolutionary processes governing tumor initiation and transformation. Tumor evolution occurred through either a 'rich' or 'sparse' ancestral common progenitor clone (CPC). We identified recurrent mutations in linker histone, JAK-STAT signaling, NF-κB signaling and B cell developmental genes. Longitudinal analyses identified early driver mutations in chromatin regulator genes (CREBBP, EZH2 and KMT2D (MLL2)), whereas mutations in EBF1 and regulators of NF-κB signaling (MYD88 and TNFAIP3) were gained at transformation. Collectively, this study provides new insights into the genetic basis of follicular lymphoma and the clonal dynamics of transformation and suggests that personalizing therapies to target key genetic alterations in the CPC represents an attractive therapeutic strategy.
Gain of function mutations in the H3K27 methyltransferase EZH2 represent a promising therapeutic target in germinal center lymphomas. In this study, we assessed the frequency and distribution of EZH2 ...mutations in a large cohort of patients with follicular lymphoma (FL) (n = 366) and performed a longitudinal analysis of mutation during the disease progression from FL to transformed FL (tFL) (n = 33). Mutations were detected at 3 recurrent mutation hot spots (Y646, A682, and A692) in 27% of FL cases with variant allele frequencies (VAF) ranging from 2% to 61%. By comparing VAF of EZH2 with other mutation targets (CREBBP, MLL2, TNFRSF14, and MEF2B), we were able to distinguish patients harboring clonal EZH2 mutation from rarer cases with subclonal mutations. Overall, the high incidence of EZH2 mutations in FL and their stability during disease progression makes FL an appropriate disease to evaluate EZH2 targeted therapy.
Key Points
Follicular lymphoma is an incurable B cell malignancy characterized by the t(14;18) translocation and mutations affecting the epigenome. Although frequent gene mutations in key signaling pathways, ...including JAK-STAT, NOTCH and NF-κB, have also been defined, the spectrum of these mutations typically overlaps with that in the closely related diffuse large B cell lymphoma (DLBCL). Using a combination of discovery exome and extended targeted sequencing, we identified recurrent somatic mutations in RRAGC uniquely enriched in patients with follicular lymphoma (17%). More than half of the mutations preferentially co-occurred with mutations in ATP6V1B2 and ATP6AP1, which encode components of the vacuolar H(+)-ATP ATPase (V-ATPase) known to be necessary for amino acid-induced activation of mTORC1. The RagC variants increased raptor binding while rendering mTORC1 signaling resistant to amino acid deprivation. The activating nature of the RRAGC mutations, their existence in the dominant clone and their stability during disease progression support their potential as an excellent candidate for therapeutic targeting.
The simultaneous growth in our understanding of lymphoma biology and the burgeoning therapeutic options has come with a renewed drive for precision‐based approaches and how best to incorporate them ...into contemporary and future patient care. In the hunt for accurate and sensitive biomarkers, liquid biopsies, particularly circulating tumour DNA, have come to the forefront as a promising tool in multiple cancer types including lymphomas, with considerable implications for clinical practice. Liquid biopsy analyses could supplement existing tissue biopsies with distinct advantages including the minimally invasive nature and the ease with which it can be repeated during a patient's clinical journey. Circulating tumour DNA (ctDNA) analyses has been and continues to be evaluated across lymphoma subtypes with potential applications as a diagnostic, disease monitoring and treatment selection tool. To make the leap into the clinic, these assays must demonstrate accuracy, reliability and a quick turnaround to be employed in the real‐time clinical management of lymphoma patients. Here, we review the available ctDNA assays and discuss key practical and technical issues around improving sensitivity. We then focus on their potential roles in several lymphoma subtypes exemplified by recent studies and provide a glimpse of different features that can be analysed beyond ctDNA.
The prognosis of HIV-infected patients with non-Hodgkin lymphoma in the highly active antiretroviral therapy (HAART) era approaches that of the general population when they are treated with the same ...protocols. We analyzed the outcome of patients with Hodgkin lymphoma (HL) treated with doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) in the HAART era according to HIV serostatus to establish whether this also holds true for HL.
From 1997 to 2010, 224 patients newly diagnosed with HL, of whom 93 were HIV positive, were consecutively treated with ABVD chemotherapy. HIV-positive patients had more high-risk disease according to the International Prognostic Score (IPS) than HIV-negative patients (IPS≥3: 68% v 26%, respectively; P<.001). Forty-seven HIV-positive patients had a CD4 count less than 200/μL, and 92 patients received HAART during chemotherapy.
The complete response rate was 74% for HIV-positive patients and 79% for HIV-negative patients (P=not significant). After a median follow-up of 60 months (range, 8 to 174 months), 23 patients (16 HIV-negative and seven HIV-positive patients) have experienced relapse at a median time of 6 months (range, 1 to 106 months). Five-year event-free survival (EFS) was 59% (95% CI, 47% to 70%) for HIV-positive patients and 66% (95% CI, 57% to 74%) for HIV-negative patients (P=not significant). Five-year overall survival (OS) was 81% (95% CI, 69% to 89%) and 88% (95% CI, 80% to 93%) for HIV-positive and HIV-negative patients, respectively (P=not significant). HIV status did not predict OS or EFS on multivariate analysis including IPS and HIV status.
This mature study demonstrates that HIV-positive patients with HL have more extensive disease with more adverse prognostic factors than HIV-negative patients, but when treated with ABVD, HIV infection does not adversely affect OS or EFS.
The development of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is driven by chronic inflammatory responses and acquired genetic changes. To investigate its genetic ...bases, we performed targeted sequencing of 93 genes in 131 MALT lymphomas including 76 from the thyroid. We found frequent deleterious mutations of TET2 (86%), CD274 (53%), TNFRSF14 (53%), and TNFAIP3 (30%) in thyroid MALT lymphoma. CD274 was also frequently deleted, together with mutation seen in 68% of cases. There was a significant association between CD274 mutation/deletion and TNFRSF14 mutation (p = 0.001). CD274 (PD-L1) and TNFRSF14 are ligands for the co-inhibitory receptor PD1 and BTLA on T-helper cells, respectively, their inactivation may free T-cell activities, promoting their help to malignant B-cells. In support of this, both the proportion of activated T-cells (CD4+CD69+/CD4+) within the proximity of malignant B-cells, and the level of transformed blasts were significantly higher in cases with CD274/TNFRSF14 genetic abnormalities than those without these changes. Both CD274 and TNFRSF14 genetic changes were significantly associated with Hashimoto's thyroiditis (p = 0.01, p = 0.04, respectively), and CD274 mutation/deletion additionally associated with increased erythrocyte sedimentation rate (p = 0.0001). In conclusion, CD274/TNFRSF14 inactivation in thyroid MALT lymphoma B-cells may deregulate their interaction with T-cells, promoting co-stimulations and impairing peripheral tolerance.
Follicular lymphoma (FL) is a heterogeneous disease with varying prognosis owing to differences in clinical, laboratory, and disease parameters. Although generally considered incurable, prognosis for ...early‐ and advanced‐stage disease has improved because of therapeutic advances, several of which have resulted from elucidation of the biologic and molecular basis of the disease. The choice of treatment for FL is highly dependent on patient and disease characteristics. Several tools are available for risk stratification, although limitations in their routine clinical use exist. For limited disease, treatment options include radiotherapy, rituximab monotherapy or combination regimens, and surveillance. Treatment of advanced disease is often determined by tumor burden, with surveillance or rituximab considered for low tumor burden and chemoimmunotherapy for high tumor burden disease. Treatment for relapsed or refractory disease is influenced by initial first‐line therapy and the duration and quality of the response. Presently, there is no consensus for treatment of patients with early or multiply relapsed disease; however, numerous agents, combination regimens, and transplant options have demonstrated efficacy. Although the number of therapies available to treat FL has increased together with an improved understanding of the underlying biologic basis of disease, the best approach to select the most appropriate treatment strategy for an individual patient at a particular time continues to be elucidated. This review considers prognostication and the evolving treatment landscape of FL, including recent and emergent therapies as well as remaining unmet needs.
Implications for Practice
In follicular lymphoma, a personalized approach to management based on disease biology, patient characteristics, and other factors continues to emerge. However, application of current management requires an understanding of the available therapeutic options for first‐line treatment and knowledge of current development in therapies for previously untreated and for relapsed or refractory disease. Thus, this work reviews for clinicians the contemporary data in follicular lymphoma, from advances in characterizing disease biology to current treatments and emerging novel therapies.
Therapeutic advances have improved prognosis for follicular lymphoma, although the disease is still incurable. This comprehensive clinical review considers prognostic approaches and the treatment landscape for follicular lymphoma, including emerging therapies and unmet needs.
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