Jessica Okosun

EZH2 mutations are frequent and represent an early event in follicular lymphoma

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.

HIV Status Does Not Influence Outcome in Patients With Classical Hodgkin Lymphoma Treated With Chemotherapy Using Doxorubicin, Bleomycin, Vinblastine, and Dacarbazine in the Highly Active Antiretroviral Therapy Era

PURPOSE 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. PATIENTS AND METHODS 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. RESULTS 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. CONCLUSION 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.

Disease evolution and outcomes in familial AML with germline CEBPA mutations.

In-depth molecular investigation of familial leukemia has been limited by the rarity of recognized cases. This study examines the genetic events initiating leukemia and details the clinical progression of disease across multiple families harboring germ-line CEBPA mutations. Clinical data were collected from 10 CEBPA-mutated families, representing 24 members with acute myeloid leukemia (AML). Whole-exome (WES) and deep sequencing were performed to genetically profile tumors and define patterns of clonal evolution. Germline CEBPA mutations clustered within the N-terminal and were highly penetrant, with AML presenting at a median age of 24.5 years (range, 1.75-46 years). In all diagnostic tumors tested (n = 18), double CEBPA mutations (CEBPAdm) were detected, with acquired (somatic) mutations preferentially targeting the C-terminal. Somatic CEBPA mutations were unstable throughout the disease course, with different mutations identified at recurrence. Deep sequencing of diagnostic and relapse paired samples confirmed that relapse-associated CEBPA mutations were absent at diagnosis, suggesting recurrence was triggered by novel, independent clones. Integrated WES and deep sequencing subsequently revealed an entirely new complement of mutations at relapse, verifying the presentation of a de novo leukemic episode. The cumulative incidence of relapse in familial AML was 56% at 10 years (n = 11), and 3 patients experienced ≥3 disease episodes over a period of 17 to 20 years. Durable responses to secondary therapies were observed, with prolonged median survival after relapse (8 years) and long-term overall survival (10-year overall survival, 67%). Our data reveal that familial CEBPA-mutated AML exhibits a unique model of disease progression, associated with favorable long-term outcomes.

Recurrent mTORC1-activating RRAGC mutations in follicular lymphoma

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.

Epigenetic dysregulation in follicular lymphoma

The adoption of next-generation sequencing technologies has led to a remarkable shift in our understanding of the genetic landscape of follicular lymphoma. While the disease has been synonymous with the t(14;18), the prevalence of alterations in genes that regulate the epigenome has been established as a pivotal hallmark of these lymphomas. Giant strides are being made in unraveling the biological consequences of these alterations in tumorigenesis opening up new opportunities for directed therapies.

Investigational epigenetically targeted drugs in early phase trials for the treatment of haematological malignancies

Introduction: For decades, cancer research has focussed on the genetic defects that drive tumourigenesis. However, recent high-resolution sequencing studies have uncovered mounting evidence for the complementary role of epigenetic deregulation as a hallmark of haematological malignancies. The reversibility of epigenetic changes makes them suitable candidates for pharmacological manipulation and therapeutic targeting. Areas covered: This review summarises the mechanisms of normal epigenetic regulation and how these are perturbed in haematological malignancies as a result of genetic alterations. The article concludes with how these can be reversed and appraises the investigational epigenetically targeted therapies in preclinical and clinical use. Expert opinion: The identification of recurring alterations in components of the epigenome of leukaemia and lymphoma has driven the rapid development of highly potent epigenetically targeted therapies. This rapid development has alluded to the possibility of a personalised therapeutic approach in selected patient populations. An enhanced understanding of the biological effects of these epigenetic alterations in initiation and progression of haematological malignancies, together with a clear mechanistic insight into how the drugs reverse the phenotypes, will define their translation into routine clinical use.

Interim fluoro-2-deoxy-D-glucose-PET predicts response and progression-free survival in patients with Hodgkin lymphoma and HIV infection

Background:Interim PET scans in HIV-negative patients with Hodgkin lymphoma has emerged as one of the most important prognostic tools. However, equivalent studies in HIV-positive patients are yet to be performed. Objective:We evaluated the prognostic value of interim [18F]-fluoro-2-deoxy-D-glucose–PET (18F-FDG PET) after two or three cycles of chemotherapy using adriamycin, bleomycin, vinblastine and dacarbazine (ABVD) with concomitant HAART in HIV-positive patients with Hodgkin lymphoma. Methods:Patients with advanced HIV–Hodgkin lymphoma (HIV-HL) from six UK centres were included. Interim PET scans after two or three cycles of ABVD (PET-2 or PET-3) were carried out. Prognostic analysis correlated the 2-year progression-free survival (PFS) rate with the interim PET result. Results:Twenty-three evaluable patients were assessed, 21 achieved a negative interim PET and 22 achieved complete remission by computerized tomography scan criteria after ABVD therapy. After a median follow-up of 27 months (range 12–50), disease progression was seen in one patient. Treatment failure was seen in one of the two interim PET-positive patients and none of the interim PET-negative patients. The 2-year PFS for interim PET-positive patients was 50%, and 100% for interim PET-negative patients (P = 0.0012). Conclusion:A negative interim 18F-FDG PET result is highly predictive of treatment success in HIV-HL patients.

Early loss of Crebbp confers malignant stem cell properties on lymphoid progenitors.

Loss-of-function mutations of cyclic-AMP response element binding protein, binding protein (CREBBP) are prevalent in lymphoid malignancies. However, the tumour suppressor functions of CREBBP remain unclear. We demonstrate that loss of Crebbp in murine haematopoietic stem and progenitor cells (HSPCs) leads to increased development of B-cell lymphomas. This is preceded by accumulation of hyperproliferative lymphoid progenitors with a defective DNA damage response (DDR) due to a failure to acetylate p53. We identify a premalignant lymphoma stem cell population with decreased H3K27ac, which undergoes transcriptional and genetic evolution due to the altered DDR, resulting in lymphomagenesis. Importantly, when Crebbp is lost later in lymphopoiesis, cellular abnormalities are lost and tumour generation is attenuated. We also document that CREBBP mutations may occur in HSPCs from patients with CREBBP-mutated lymphoma. These data suggest that earlier loss of Crebbp is advantageous for lymphoid transformation and inform the cellular origins and subsequent evolution of lymphoid malignancies.

The routes for transformation of follicular lymphoma.

Purpose of reviewAggressive transformation, a frequent event in the natural history of follicular lymphoma, is associated with increased lymphoma-related mortality and yet the underlying biology remains poorly defined. This review outlines recent advances in our understanding of the genetic basis and evolutionary process leading to transformation. Recent findingsBoth the antecedent indolent and transformed follicular lymphoma (tFL) arise through branched divergent evolution with tumors emerging from a founder precursor population, the common progenitor cell. Although the majority of tFLs maintain a germinal center B-cell gene expression signature, an activated B-cell-type (ABC-type) profile appears to predominate in BCL2-translocation negative cases. It does not appear that a single unifying genetic or epigenetic event promotes a fitter and more aggressive clone. SummaryTransformed follicular tumors are genetically heterogeneous perhaps reflecting the varying clinical behavior and outcomes of this disease event. Follicular lymphoma and tFL remain incurable tumors highlighted by our inability to eradicate the founder common progenitor cell population with current therapies. Progress has now been made in defining the genetic events and evolutionary pathways responsible for transformation. Although more research is required in predicting and understanding the biology of transformation, there are opportunities to improve outcomes by preferentially directing targeted therapies toward ‘actionable’ early and transformation-specific aberrations.

Genomic profiling reveals spatial intra-tumor heterogeneity in follicular lymphoma.

We are indebted to the patients for donating tumor specimens as part of this study. The authors thank the Centre de Ressources Biologiques (CRB)-Sante of Rennes (BB-0033-00056) for patient samples, Queen Mary University of London Genome Centre for Illumina Miseq sequencing, and the support by the National Institute for Health Research (NIHR) Biomedical Research Centre at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London for Illumina Hiseq sequencing. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health. This work was supported by grants from the Kay Kendall Leukaemia Fund (KKL 757 awarded to J.O.), Cancer Research UK (22742 awarded to J.O., 15968 awarded to J.F., Clinical Research Fellowship awarded to S.A.), Bloodwise through funding of the Precision Medicine for Aggressive Lymphoma (PMAL) consortium, Centre for Genomic Health, Queen Mary University of London, Carte d’Identite des Tumeurs (CIT), Ligue National contre le Cancer, Pole de biologie hospital universitaire de Rennes, CRB-Sante of Rennes (BB-0033-00056), and CeVi/Carnot program.