Molecular MRD is strongly prognostic in patients with NPM1-mutated AML receiving venetoclax-based nonintensive therapy.

ABSTRACT: Assessment of measurable residual disease (MRD) by quantitative reverse transcription polymerase chain reaction is strongly prognostic in patients with NPM1-mutated acute myeloid leukemia (AML) treated with intensive chemotherapy; however, there are no data regarding its utility in venetoclax-based nonintensive therapy, despite high efficacy in this genotype. We analyzed the prognostic impact of NPM1 MRD in an international real-world cohort of 76 previously untreated patients with NPM1-mutated AML who achieved complete remission (CR)/CR with incomplete hematological recovery following treatment with venetoclax and hypomethylating agents (HMAs) or low-dose cytarabine (LDAC). A total of 44 patients (58%) achieved bone marrow (BM) MRD negativity, and a further 14 (18%) achieved a reduction of ≥4 log10 from baseline as their best response, with no difference between HMAs and LDAC. The cumulative rates of BM MRD negativity by the end of cycles 2, 4, and 6 were 25%, 47%, and 50%, respectively. Patients achieving BM MRD negativity by the end of cycle 4 had 2-year overall of 84% compared with 46% if MRD was positive. On multivariable analyses, MRD negativity was the strongest prognostic factor. A total of 22 patients electively stopped therapy in BM MRD-negative remission after a median of 8 cycles, with 2-year treatment-free remission of 88%. In patients with NPM1-mutated AML attaining remission with venetoclax combination therapies, NPM1 MRD provides valuable prognostic information.

Sorafenib plus intensive chemotherapy in newly diagnosed FLT3-ITD AML: a randomized, placebo-controlled study by the ALLG.

Sorafenib maintenance improves outcomes after hematopoietic cell transplant (HCT) for patients with FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) acute myeloid leukemia (AML). Although promising outcomes have been reported for sorafenib plus intensive chemotherapy, randomized data are limited. This placebo-controlled, phase 2 study (ACTRN12611001112954) randomized 102 patients (aged 18-65 years) 2:1 to sorafenib vs placebo (days 4-10) combined with intensive induction: idarubicin 12 mg/m2 on days 1 to 3 plus either cytarabine 1.5 g/m2 twice daily on days 1, 3, 5, and 7 (18-55 years) or 100 mg/m2 on days 1 to 7 (56-65 years), followed by consolidation and maintenance therapy for 12 months (post-HCT excluded) in newly diagnosed patients with FLT3-ITD AML. Four patients were excluded in a modified intention-to-treat final analysis (3 not commencing therapy and 1 was FLT3-ITD negative). Rates of complete remission (CR)/CR with incomplete hematologic recovery were high in both arms (sorafenib, 78%/9%; placebo, 70%/24%). With 49.1-months median follow-up, the primary end point of event-free survival (EFS) was not improved by sorafenib (2-year EFS 47.9% vs 45.4%; hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.51-1.51; P = .61). Two-year overall survival (OS) was 67% in the sorafenib arm and 58% in the placebo arm (HR, 0.76; 95% CI, 0.42-1.39). For patients who received HCT in first remission, the 2-year OS rates were 84% and 67% in the sorafenib and placebo arms, respectively (HR, 0.45; 95% CI, 0.18-1.12; P = .08). In exploratory analyses, FLT3-ITD measurable residual disease (MRD) negative status (<0.001%) after induction was associated with improved 2-year OS (83% vs 60%; HR, 0.4; 95% CI, 0.17-0.93; P = .028). In conclusion, routine use of pretransplant sorafenib plus chemotherapy in unselected patients with FLT3-ITD AML is not supported by this study.

A gene expression-based model predicts outcome in children with intermediate-risk classical Hodgkin lymphoma.

Classical Hodgkin lymphoma (cHL) is a common malignancy in children and adolescents. Although cHL is highly curable, treatment with chemotherapy and radiation often come at the cost of long-term toxicity and morbidity. Effective risk-stratification tools are needed to tailor therapy. Here, we used gene expression profiling (GEP) to investigate tumor microenvironment (TME) biology, to determine molecular correlates of treatment failure, and to develop an outcome model prognostic for pediatric cHL. A total of 246 formalin-fixed, paraffin-embedded tissue biopsies from patients enrolled in the Children's Oncology Group trial AHOD0031 were used for GEP and compared with adult cHL data. Eosinophil, B-cell, and mast cell signatures were enriched in children, whereas macrophage and stromal signatures were more prominent in adults. Concordantly, a previously published model for overall survival prediction in adult cHL did not validate in pediatric cHL. Therefore, we developed a 9-cellular component model reflecting TME composition to predict event-free survival (EFS). In an independent validation cohort, we observed a significant difference in weighted 5-year EFS between high-risk and low-risk groups (75.2% vs 90.3%; log-rank P = .0138) independent of interim response, stage, fever, and albumin. We demonstrate unique disease biology in children and adolescents that can be harnessed for risk-stratification at diagnosis. This trial was registered at www.clinicaltrials.gov as #NCT00025259.

Intestinal-specific Hdac3 deletion increases susceptibility to colitis and small intestinal tumor development in mice fed a high-fat diet.

High-fat (HF) diets (HFDs) and inflammation are risk factors for colon cancer; however, the underlying mechanisms remain to be fully elucidated. The transcriptional corepressor HDAC3 has recently emerged as a key regulator of intestinal epithelial responses to diet and inflammation with intestinal-specific Hdac3 deletion (Hdac3IKO) in mice increasing fatty acid oxidation genes and the rate of fatty acid oxidation in enterocytes. Hdac3IKO mice are also predisposed to experimentally induced colitis; however, whether this is driven by the intestinal metabolic reprogramming and whether this predisposes these mice to intestinal tumorigenesis is unknown. Herein, we examined the effects of intestinal-specific Hdac3 deletion on colitis-associated intestinal tumorigenesis in mice fed a standard (STD) or HFD. Hdac3IKO mice were highly prone to experimentally induced colitis, which was further enhanced by an HFD. Hdac3 deletion also accelerated intestinal tumor development, specifically when fed an HFD and most notably in the small intestine where lipid absorption is maximal. Expression of proteins involved in fatty acid metabolism and oxidation (SCD1, EHHADH) were elevated in the small intestine of Hdac3IKO mice fed an HFD, and these mice displayed increased levels of lipid peroxidation, DNA damage, and apoptosis in their villi, as well as extensive expansion of the stem cell and progenitor cell compartment. These findings reveal a novel role for Hdac3 in suppressing colitis and intestinal tumorigenesis, particularly in the context of consumption of an HFD, and reveal a potential mechanism by which HFDs may increase intestinal tumorigenesis by increasing fatty acid oxidation, DNA damage, and intestinal epithelial cell turnover.NEW & NOTEWORTHY We reveal a novel role for the transcriptional corepressor Hdac3 in suppressing colitis and intestinal tumorigenesis, particularly in the context of consumption of an HFD, and reveal a potential mechanism by which HFDs may increase intestinal tumorigenesis by increasing fatty acid oxidation, DNA damage, and intestinal epithelial cell turnover. We also identify a unique mouse model for investigating the complex interplay between diet, metabolic reprogramming, and tumor predisposition in the intestinal epithelium.

Invasive fungal infection following venetoclax and posaconazole co-administration.

The co-administration of venetoclax, a BCL-2 inhibitor, with a mould-active azole, such a posaconazole, has potential to both prevent invasive fungal infection (IFI) and reduce the required treatment dose, and cost, of venetoclax. Posaconazole drug-level monitoring is critical to ensuring adequate mould prophylaxis. A retrospective audit of 99 patients at a tertiary cancer centre, with myeloid malignancies co-prescribed venetoclax and posaconazole between January 2018 and April 2022, was undertaken to evaluate the adequacy of posaconazole prescribing and the rate of breakthrough IFI. Seventy-six patients (77%) had at least one posaconazole level measured in the study period, with 37% requiring a dose adjustment based on steady-state trough levels. Breakthrough IFI occurred in 4% of patients, typically within 1 month of commencing anti-mould prophylaxis. Close monitoring of posaconazole levels in venetoclax-treated patients, particularly in the early, outpatient setting, is critical.

Attenuated alpha oscillation and hyperresponsiveness reveals impaired perceptual learning in migraineurs.

BACKGROUND: Anomalous phantom visual perceptions coupled to an aversion and discomfort to some visual patterns (especially grating in mid-range spatial frequency) have been associated with the hyperresponsiveness in migraine patients. Previous literature has found fluctuations of alpha oscillation (8-14 Hz) over the visual cortex to be associated with the gating of the visual stream. In the current study, we examined whether alpha activity was differentially modulated in migraineurs in anticipation of an upcoming stimulus as well as post-stimulus periods. METHODS: We used EEG to examine the brain activity in a group of 28 migraineurs (17 with aura /11 without) and 29 non-migraineurs and compared their alpha power in the pre/post-stimulus period relative to the onset of stripped gratings. RESULTS: Overall, we found that migraineurs had significantly less alpha power prior to the onset of the stimulus relative to controls. Moreover, migraineurs had significantly greater post-stimulus alpha suppression (i.e event-related desynchronization) induced by the grating in 3 cycles per degree at the 2nd half of the experiment. CONCLUSIONS: These findings, taken together, provide strong support for the presence of the hyperresponsiveness of the visual cortex of migraine sufferers. We speculate that it could be the consequence of impaired perceptual learning driven by the dysfunction of GABAergic inhibitory mechanism.

Venetoclax induces rapid elimination of NPM1 mutant measurable residual disease in combination with low-intensity chemotherapy in acute myeloid leukaemia.

Based on promising results in older adults with acute myeloid leukaemia (AML), we treated patients with NPM1mut measurable residual disease (MRD) using off-label venetoclax in combination with low-dose cytarabine or azacitidine. Twelve consecutive patients were retrospectively identified, including five with molecular persistence and seven with molecular relapse/progression. All patients with molecular persistence achieved durable molecular complete remission (CRMRD- ) without transplantation. Six of seven patients with molecular relapse/progression achieved CRMRD- after 1-2 cycles of venetoclax. This paper highlights the promising efficacy of venetoclax-based therapy to reduce the relapse risk in patients with persistent or rising NPM1mut MRD.

BET inhibitor resistance emerges from leukaemia stem cells.

Bromodomain and extra terminal protein (BET) inhibitors are first-in-class targeted therapies that deliver a new therapeutic opportunity by directly targeting bromodomain proteins that bind acetylated chromatin marks. Early clinical trials have shown promise, especially in acute myeloid leukaemia, and therefore the evaluation of resistance mechanisms is crucial to optimize the clinical efficacy of these drugs. Here we use primary mouse haematopoietic stem and progenitor cells immortalized with the fusion protein MLL-AF9 to generate several single-cell clones that demonstrate resistance, in vitro and in vivo, to the prototypical BET inhibitor, I-BET. Resistance to I-BET confers cross-resistance to chemically distinct BET inhibitors such as JQ1, as well as resistance to genetic knockdown of BET proteins. Resistance is not mediated through increased drug efflux or metabolism, but is shown to emerge from leukaemia stem cells both ex vivo and in vivo. Chromatin-bound BRD4 is globally reduced in resistant cells, whereas the expression of key target genes such as Myc remains unaltered, highlighting the existence of alternative mechanisms to regulate transcription. We demonstrate that resistance to BET inhibitors, in human and mouse leukaemia cells, is in part a consequence of increased Wnt/ß-catenin signalling, and negative regulation of this pathway results in restoration of sensitivity to I-BET in vitro and in vivo. Together, these findings provide new insights into the biology of acute myeloid leukaemia, highlight potential therapeutic limitations of BET inhibitors, and identify strategies that may enhance the clinical utility of these unique targeted therapies.

Outcomes of non-myeloablative allogeneic stem cell transplant in older patients with acute myeloid leukaemia in first remission.

The benefits of non-myeloablative stem cell transplant in older patients with acute myeloid leukaemia are unclear. We compare the long-term outcomes of this regimen in those aged 55-65 years in first remission with a chemotherapy only cohort that achieved durable morphologic remission. Five-year overall survival was similar (32% vs 33%, P = 0.90), as was relapse-free survival (23% vs 20%, P = 0.37). There was a trend for decreased relapse that was balanced against increased non-relapse mortality with transplantation.

Validation of the RHL30 digital gene expression assay as a prognostic biomarker for relapsed Hodgkin lymphoma.

Despite continuing improvements in the management of classical Hodgkin lymphoma (cHL), relapse remains associated with a risk of lymphoma-related mortality. The biological composition of relapse tumour biopsies shows interpatient variability, which can be leveraged to design prognostic biomarkers. Here, we validated the RHL30 assay, a previously reported gene expression model in an independent cohort of 41 patients with relapsed cHL. Patients classified as high-risk by the RHL30 assay had inferior failure-free survival (FFS) after autologous stem cell transplantation (2-year FFS 41% vs. 92%, P = 0·035). The RHL30 model is a robust biomarker that risk-stratifies patients considered for autologous stem cell transplantation.

Fine-tuning of FOXO3A in cHL as a survival mechanism and a hallmark of abortive plasma cell differentiation.

We recently found that FOXO1 repression contributes to the oncogenic program of classical Hodgkin lymphoma (cHL). Interestingly, FOXO3A, another member of the FOXO family, was reported to be expressed in the malignant Hodgkin and Reed-Sternberg cells of cHL at higher levels than in non-Hodgkin lymphoma subtypes. We thus aimed to investigate mechanisms responsible for the maintenance of FOXO3A as well as the potential role of FOXO3A in cHL. Here, we show that high FOXO3A levels in cHL reflect a B-cell-differentiation-specific pattern. In B cells, FOXO3A expression increases during the process of centroblast to plasma cell (PC) differentiation. FOXO3A levels in cHL were found higher than in germinal center B cells, but lower than in terminally differentiated PCs. This intermediate FOXO3A expression in cHL might manifest the "abortive PC differentiation" phenotype. This assumption was further corroborated by the finding that overexpression of FOXO3A in cHL cell lines induced activation of the master PC transcription factor PRDM1α. As factors attenuating FOXO3A expression in cHL, we identified MIR155 and constitutive activation of extracellular signal-regulated kinase. Finally, we demonstrate the importance of FOXO3A expression in cHL using an RNA interference approach. We conclude that tightly regulated expression of FOXO3A contributes to the oncogenic program and to the specific phenotype of cHL.

Somatic IL4R mutations in primary mediastinal large B-cell lymphoma lead to constitutive JAK-STAT signaling activation.

Primary mediastinal large B-cell lymphoma (PMBCL) is a distinct subtype of diffuse large B-cell lymphoma thought to arise from thymic medullary B cells. Gene mutations underlying the molecular pathogenesis of the disease are incompletely characterized. Here, we describe novel somatic IL4R mutations in 15 of 62 primary cases of PMBCL (24.2%) and in all PMBCL-derived cell lines tested. The majority of mutations (11/21; 52%) were hotspot single nucleotide variants in exon 8, leading to an I242N amino acid change in the transmembrane domain. Functional analyses establish this mutation as gain of function leading to constitutive activation of the JAK-STAT pathway and upregulation of downstream cytokine expression profiles and B cell-specific antigens. Moreover, expression of I242N mutant IL4R in a mouse xenotransplantation model conferred growth advantage in vivo. The pattern of concurrent mutations within the JAK-STAT signaling pathway suggests additive/synergistic effects of these gene mutations contributing to lymphomagenesis. Our data establish IL4R mutations as novel driver alterations and provide a strong preclinical rationale for therapeutic targeting of JAK-STAT signaling in PMBCL.

Molecular disease monitoring using circulating tumor DNA in myelodysplastic syndromes.

The diagnosis and monitoring of myelodysplastic syndromes (MDSs) are highly reliant on bone marrow morphology, which is associated with substantial interobserver variability. Although azacitidine is the mainstay of treatment in MDS, only half of all patients respond. Therefore, there is an urgent need for improved modalities for the diagnosis and monitoring of MDSs. The majority of MDS patients have either clonal somatic karyotypic abnormalities and/or gene mutations that aid in the diagnosis and can be used to monitor treatment response. Circulating cell-free DNA is primarily derived from hematopoietic cells, and we surmised that the malignant MDS genome would be a major contributor to cell-free DNA levels in MDS patients as a result of ineffective hematopoiesis. Through analysis of serial bone marrow and matched plasma samples (n = 75), we demonstrate that cell-free circulating tumor DNA (ctDNA) is directly comparable to bone marrow biopsy in representing the genomic heterogeneity of malignant clones in MDS. Remarkably, we demonstrate that serial monitoring of ctDNA allows concurrent tracking of both mutations and karyotypic abnormalities throughout therapy and is able to anticipate treatment failure. These data highlight the role of ctDNA as a minimally invasive molecular disease monitoring strategy in MDS.

Inhibition of Pol I transcription treats murine and human AML by targeting the leukemia-initiating cell population.

Despite the development of novel drugs, the prospects for many patients with acute myeloid leukemia (AML) remain dismal. This study reveals that the selective inhibitor of RNA polymerase I (Pol I) transcription, CX-5461, effectively treats aggressive AML, including mixed-lineage leukemia-driven AML, and outperforms standard chemotherapies. In addition to the previously characterized mechanism of action of CX-5461 (ie, the induction of p53-dependent apoptotic cell death), the inhibition of Pol I transcription also demonstrates potent efficacy in p53null AML in vivo. This significant survival advantage in both p53WT and p53null leukemic mice treated with CX-5461 is associated with activation of the checkpoint kinases 1/2, an aberrant G2/M cell-cycle progression and induction of myeloid differentiation of the leukemic blasts. The ability to target the leukemic-initiating cell population is thought to be essential for lasting therapeutic benefit. Most strikingly, the acute inhibition of Pol I transcription reduces both the leukemic granulocyte-macrophage progenitor and leukemia-initiating cell (LIC) populations, and suppresses their clonogenic capacity. This suggests that dysregulated Pol I transcription is essential for the maintenance of their leukemia-initiating potential. Together, these findings demonstrate the therapeutic utility of this new class of inhibitors to treat highly aggressive AML by targeting LICs.

Genetic profiling of MYC and BCL2 in diffuse large B-cell lymphoma determines cell-of-origin-specific clinical impact.

The clinical significance of MYC and BCL2 genetic alterations in diffuse large B-cell lymphoma (DLBCL), apart from translocations, has not been comprehensively investigated using high-resolution genetic assays. In this study, we profiled MYC and BCL2 genetic alterations using next-generation sequencing and high-resolution SNP array in 347 de novo DLBCL cases treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) at the British Columbia Cancer Agency. Cell-of-origin (COO) subtype was determined by Lymph2Cx digital gene expression profiling. We showed that the incidence of MYC/BCL2 genetic alterations and their clinical significance were largely dependent on COO subtypes. It is noteworthy that the presence of BCL2 gain/amplification is significantly associated with poor outcome in activated B-cell-like and BCL2 translocation with poor outcome in germinal center B-cell subtypes, respectively. Both have prognostic significance independent of MYC/BCL2 dual expression and the International Prognostic Index (IPI). Furthermore, the combination of BCL2 genetic alterations with IPI identifies markedly worse prognostic groups within individual COO subtypes. Thus, high-resolution genomic assays identify extremely poor prognostic groups within each COO subtype on the basis of BCL2 genetic status in this large, uniformly R-CHOP-treated population-based cohort of DLBCL. These results suggest COO subtype-specific biomarkers based on BCL2 genetic alterations can be used to risk-stratify patients with DLBCL treated with immunochemotherapy.

Novel insights into the disease dynamics of B-cell lymphomas in the Genomics Era.

High-throughput sequencing has significantly contributed to revealing the molecular underpinnings of B-cell lymphomagenesis and disease progression. It is now a widely accepted concept that the diversity of clinical responses to front-line therapy and the development of relapsed/refractory disease are in part explained by 'inter-patient' genetic heterogeneity measurable by individual sets of somatic gene alterations in tumor genomes. Moreover, extensive 'intra-tumor' heterogeneity on the genotypic and phenotypic levels is the product of ongoing tumor evolution and adaptation to various selective pressures during cancer initiation, progression, and therapeutic intervention. As the management of disease progression remains one of the most significant clinical challenges, it is becoming increasingly important to delineate how B-cell lymphomas evolve over time and to develop progression-related biomarker assays. Toward this goal, recent investigations have moved from studying lymphoma biology at initial diagnosis to doing so at multiple time points during the disease course. Profiling progressed tumors, and in particular paired biopsies at initial diagnosis and disease progression of the same patients, has led to novel insights into clonal tumor evolution and tumor microenvironment dynamics. This review discusses the latest findings on genomic alterations and microenvironment biology associated with relapsed/refractory B-cell lymphomas, with a particular emphasis on alterations that are acquired or become more prevalent at disease progression. We also describe overarching tumor evolution patterns, and highlight emerging precision medicine methodologies that can aid in an improved understanding and management of relapsed/refractory disease. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Evidence for distinct clusters of diverse anomalous experiences and their selective association with signs of elevated cortical hyperexcitability.

Visual cortical hyperexcitability is now known to be an underlying factor for aberrant visual experience, including hallucinations, and pattern or light induced visual discomfort. Such factors have also been observed in neurological and non-clinical groups (albeit in attenuated form) - consistent with the notion of a continuum of anomalous experiences. Utilizing an exploratory factor analysis (EFA) approach (n = 300), Study 1 developed a revised proxy screening measure for visual cortical hyperexcitability - the Cortical Hyperexcitability index - II(CHi-II). The EFA revealed a stable 3-factor solution which can be characterised as; (i) Heightened Visual Sensitivity and Discomfort (HVSD); (ii) Aura-like Hallucinatory Experience (AHE); and, (iii) Distorted Visual Perception (DVP). Study 2 tested both a self-reported migraine group and a control group on the CHi-II in conjunction with a computerised pattern-glare task that is known to reflect visual cortical hyperexcitability. The migraine group produced significantly elevated scores on both the AHE and HVSD factors of the CHi-II, relative to controls. Among the non-migraine group, subjects who scored higher in the pattern-glare task also produced significantly elevated scores on the AHE factor compared to those with low pattern-glare task scores. Collectively, these findings support the utility of the CHi-II as an indirect proxy measure for signs of cortical hyperexcitability and reveal new categorical distinctions for the nature of the anomalous perceptions. These perceptions may well reflect diverse neurocognitive underpinnings leading to advancements in our understanding of aberrations in conscious experience.

Acute myeloid leukaemia relapsing after allogeneic haemopoietic stem cell transplantation: prognostic factors and impact of initial therapy of relapse.

BACKGROUND/AIMS: We sought to determine factors associated with the overall survival from relapse (OSR) of acute myeloid leukaemia (AML) after allogeneic haemopoietic stem cell transplantation (alloHSCT) and the effect of first salvage therapy and subsequent graft-versus-host disease (GVHD) on OSR. METHODS: Data on 386 patients from nine Australian centres with relapsed AML post-alloHSCT were collected retrospectively. OSR was calculated using the Kaplan-Meier method. Univariate and multivariate analyses were conducted using the log-rank test and proportional hazards modelling, respectively and a prognostic index for OSR was derived from multivariate modelling. RESULTS: On multivariate analysis, relapse within 6 months (hazard ratio (HR) 2.4, P < 0.001) and grade 3-4 acute GVHD preceding relapse (HR 2.0, P = 0.004), were associated with inferior OSR. Patients with 1-2 factors had inferior OSR compared to those with zero factors (all patients: HR 2.3, P < 0.001, patients given salvage: HR 1.8, P < 0.001). The first salvage therapy used post-relapse was donor cell therapy (DCT) (second alloHSCT or donor lymphocyte infusion) in 75, re-induction chemotherapy (CT) in 103, radiotherapy in 8 and interferon-α in 6. Although re-induction CT death rate was low (2%), survival after CT was inferior to DCT (HR 1.9, P < 0.001). No survival benefit was seen for patients who developed GVHD following salvage therapy (P = 0.405). CONCLUSION: Patients with AML who relapse beyond 6 months from alloHSCT without prior grade 3-4 acute GVHD have a better outcome from salvage therapy. Salvage treatments employing DCT as the initial treatment of AML relapse confer a survival advantage over CT.

Genetic inactivation of TRAF3 in canine and human B-cell lymphoma.

Non-Hodgkin lymphomas (NHLs) are the most common cancer to affect pet dogs. In contrast to the many genes whose mutation contributes to lymphomagenesis in humans, relatively little is known about the acquired genetic alterations that lead to canine B-cell lymphomas (cBCLs). We performed a survey of 84 canine NHL tumors to identify genes affected by somatic point mutations. We found mutations affecting TRAF3, which encodes a negative regulator of nuclear factor (NF)-κB, to be a common feature of cBCLs, with mutations observed in 44% of tumors including a combination of somatic and rare germ-line variants. Overall, 30% of the tumors contained ≥1 somatic TRAF3 mutation. The majority of mutations are predicted to cause loss of TRAF3 protein including those impacting reading frame and splicing. To determine whether TRAF3 loss might be relevant to human NHL, we also analyzed 148 human diffuse large B-cell lymphoma (DLBCL) tumors and identified loss of TRAF3 as a common event, affecting ∼9% of DLBCLs, and reduced expression of TRAF3 among deleted cases. This study implicates mutations affecting NF-κB activity as a novel genetic commonality between human and canine NHLs and supports the potential utility of cBCLs with mutated TRAF3 as a model of the more aggressive activated B-cell subgroup of DLBCL.

Cell of origin of transformed follicular lymphoma.

Follicular lymphoma (FL) is an indolent disease but transforms in 2% to 3% of patients per year into aggressive, large cell lymphoma, a critical event in the course of the disease associated with increased lymphoma-related mortality. Early transformation cannot be accurately predicted at the time of FL diagnosis and the biology of transformed FL (TFL) is poorly understood. Here, we assembled a cohort of 126 diagnostic FL specimens including 40 patients experiencing transformation (<5 years) and 86 patients not experiencing transformation for at least 5 years. In addition, we assembled an overlapping cohort of 155 TFL patients, including 114 cases for which paired samples were available, and assessed temporal changes of routinely available biomarkers, outcome after transformation, as well as molecular subtypes of TFL. We report that the expression of IRF4 is an independent predictor of early transformation (Hazard ratio, 13.3; P < .001). We also show that composite histology at the time of transformation predicts favorable prognosis. Moreover, applying the Lymph2Cx digital gene expression assay for diffuse large B-cell lymphoma (DLBCL) cell-of-origin determination to 110 patients with DLBCL-like TFL, we demonstrate that TFL is of the germinal-center B-cell-like subtype in the majority of cases (80%) but that a significant proportion of cases is of the activated B-cell-like (ABC) subtype (16%). These latter cases are commonly negative for BCL2 translocation and arise preferentially from BCL2 translocation-negative and/or IRF4-expressing FLs. Our study demonstrates the existence of molecular heterogeneity in TFL as well as its relationship to the antecedent FL.