Burkitt lymphoma with a granulomatous reaction: an M1/Th1-polarised microenvironment is associated with controlled growth and spontaneous regression.

AIMS: Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that, in some instances, may show a granulomatous reaction associated with a favourable prognosis and occasional spontaneous regression. In the present study, we aimed to define the tumour microenvironment (TME) in four such cases, two of which regressed spontaneously. METHODS AND RESULTS: All cases showed aggregates of tumour cells with the typical morphology, molecular cytogenetics and immunophenotype of BL surrounded by a florid epithelioid granulomatous reaction. All four cases were Epstein-Barr virus (EBV)-positive with type I latency. Investigation of the TME showed similar features in all four cases. The analysis revealed a proinflammatory response triggered by Th1 lymphocytes and M1 polarised macrophages encircling the neoplastic cells with a peculiar topographic distribution. CONCLUSIONS: Our data provide an in-vivo picture of the role that specific immune cell subsets might play during the early phase of BL, which may be capable of maintaining the tumour in a self-limited state or inducing its regression. These novel results may provide insights into new potential therapeutic avenues in EBV-positive BL patients in the era of cellular immunotherapy.

Generation and validation of a PET radiomics model that predicts survival in diffuse large B cell lymphoma treated with R-CHOP14: A SAKK 38/07 trial post-hoc analysis.

Functional parameters from positron emission tomography (PET) seem promising biomarkers in various lymphoma subtypes. This study investigated the prognostic value of PET radiomics in diffuse large B-cell lymphoma (DLBCL) patients treated with R-CHOP given either every 14 (testing set) or 21 days (validation set). Using the PyRadiomics Python package, 107 radiomics features were extracted from baseline PET scans of 133 patients enrolled in the Swiss Group for Clinical Cancer Research 38/07 prospective clinical trial (SAKK 38/07) [ClinicalTrial.gov identifier: NCT00544219]. The international prognostic indices, the main clinical parameters and standard PET metrics, together with 52 radiomics uncorrelated features (selected using the Spearman correlation test) were included in a least absolute shrinkage and selection operator (LASSO) Cox regression to assess their impact on progression-free (PFS), cause-specific (CSS), and overall survival (OS). A linear combination of the resulting parameters generated a prognostic radiomics score (RS) whose area under the curve (AUC) was calculated by receiver operating characteristic analysis. The RS efficacy was validated in an independent cohort of 107 DLBCL patients. LASSO Cox regression identified four radiomics features predicting PFS in SAKK 38/07. The derived RS showed a significant capability to foresee PFS in both testing (AUC, 0.709; p < 0.001) and validation (AUC, 0.706; p < 0.001) sets. RS was significantly associated also with CSS and OS in testing (CSS: AUC, 0.721; p < 0.001; OS: AUC, 0.740; p < 0.001) and validation (CSS: AUC, 0.763; p < 0.0001; OS: AUC, 0.703; p = 0.004) sets. The RS allowed risk classification of patients with significantly different PFS, CSS, and OS in both cohorts showing better predictive accuracy respect to clinical international indices. PET-derived radiomics may improve the prediction of outcome in DLBCL patients.

EBV renders B cells susceptible to HIV-1 in humanized mice.

HIV and EBV are human pathogens that cause a considerable burden to worldwide health. In combination, these viruses are linked to AIDS-associated lymphomas. We found that EBV, which transforms B cells, renders them susceptible to HIV-1 infection in a CXCR4 and CD4-dependent manner in vitro and that CXCR4-tropic HIV-1 integrates into the genome of these B cells with the same molecular profile as in autologous CD4+ T cells. In addition, we established a humanized mouse model to investigate the in vivo interactions of EBV and HIV-1 upon coinfection. The respective mice that reconstitute human immune system components upon transplantation with CD34+ human hematopoietic progenitor cells could recapitulate aspects of EBV and HIV immunobiology observed in dual-infected patients. Upon coinfection of humanized mice, EBV/HIV dual-infected B cells could be detected, but were susceptible to CD8+ T-cell-mediated immune control.

Toxicity associated with PD-1 blockade after allogeneic haematopoietic cell transplantation.

Cancer immunotherapy with immune checkpoint inhibitors (ICIs) such as programmed death ligand-1 (PD-L1) blockers offers pronounced clinical benefit with durable responses and a manageable safety profile. Patients with a high risk of immune-related adverse events are generally excluded from clinical trials testing ICI therapy. Thus, only a little information on the safety and clinical outcome of patients treated with an ICI after allogeneic haematopoietic cell transplantation (HCT) is currently available. Here, we report the characteristics and outcomes of six patients with, respectively, clear cell renal carcinoma, diffuse large cell B-cell lymphoma, Hodgkin lymphoma, a microsatellite instable colorectal cancer and melanoma who were treated with PD-1 blocking antibodies. All patients had previously undergone allogeneic HCT. Severe grade 3–5 immune-related adverse events were observed in three of five patients who received full-dose ICI therapy. One patient received a lower dose of PD-1 blocking antibody. Only one patient had an objective response, whereas all the other patients had progressive disease. The high toxicity of a full- dose anti-PD-1 treatment regimen suggests that other treatment approaches for patients after allogeneic HCT are needed outside of the context of relapsed Hodgkin disease. In cases where ICI therapy is the only treatment option, reduced dosing should be explored.

Publisher Correction: Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Absence of NKG2D ligands defines leukaemia stem cells and mediates their immune evasion.

Patients with acute myeloid leukaemia (AML) often achieve remission after therapy, but subsequently die of relapse1 that is driven by chemotherapy-resistant leukaemic stem cells (LSCs)2,3. LSCs are defined by their capacity to initiate leukaemia in immunocompromised mice4. However, this precludes analyses of their interaction with lymphocytes as components of anti-tumour immunity5, which LSCs must escape to induce cancer. Here we demonstrate that stemness and immune evasion are closely intertwined in AML. Using xenografts of human AML as well as syngeneic mouse models of leukaemia, we show that ligands of the danger detector NKG2D-a critical mediator of anti-tumour immunity by cytotoxic lymphocytes, such as NK cells6-9-are generally expressed on bulk AML cells but not on LSCs. AML cells with LSC properties can be isolated by their lack of expression of NKG2D ligands (NKG2DLs) in both CD34-expressing and non-CD34-expressing cases of AML. AML cells that express NKG2DLs are cleared by NK cells, whereas NKG2DL-negative leukaemic cells isolated from the same individual escape cell killing by NK cells. These NKG2DL-negative AML cells show an immature morphology, display molecular and functional stemness characteristics, and can initiate serially re-transplantable leukaemia and survive chemotherapy in patient-derived xenotransplant models. Mechanistically, poly-ADP-ribose polymerase 1 (PARP1) represses expression of NKG2DLs. Genetic or pharmacologic inhibition of PARP1 induces NKG2DLs on the LSC surface but not on healthy or pre-leukaemic cells. Treatment with PARP1 inhibitors, followed by transfer of polyclonal NK cells, suppresses leukaemogenesis in patient-derived xenotransplant models. In summary, our data link the LSC concept to immune escape and provide a strong rationale for targeting therapy-resistant LSCs by PARP1 inhibition, which renders them amenable to control by NK cells in vivo.

Targeting compensatory MEK/ERK activation increases JAK inhibitor efficacy in myeloproliferative neoplasms.

Constitutive JAK2 signaling is central to myeloproliferative neoplasm (MPN) pathogenesis and results in activation of STAT, PI3K/AKT, and MEK/ERK signaling. However, the therapeutic efficacy of current JAK2 inhibitors is limited. We investigated the role of MEK/ERK signaling in MPN cell survival in the setting of JAK inhibition. Type I and II JAK2 inhibition suppressed MEK/ERK activation in MPN cell lines in vitro, but not in Jak2V617F and MPLW515L mouse models in vivo. JAK2 inhibition ex vivo inhibited MEK/ERK signaling, suggesting that cell-extrinsic factors maintain ERK activation in vivo. We identified PDGFRα as an activated kinase that remains activated upon JAK2 inhibition in vivo, and PDGF-AA/PDGF-BB production persisted in the setting of JAK inhibition. PDGF-BB maintained ERK activation in the presence of ruxolitinib, consistent with its function as a ligand-induced bypass for ERK activation. Combined JAK/MEK inhibition suppressed MEK/ERK activation in Jak2V617F and MPLW515L mice with increased efficacy and reversal of fibrosis to an extent not seen with JAK inhibitors. This demonstrates that compensatory ERK activation limits the efficacy of JAK2 inhibition and dual JAK/MEK inhibition provides an opportunity for improved therapeutic efficacy in MPNs and in other malignancies driven by aberrant JAK-STAT signaling.

TIRAP p.R81C is a novel lymphoma risk variant which enhances cell proliferation via NF-κB mediated signaling in B-cells.

Diffuse large B-cell lymphoma is the most common malignant lymphoma in adults. By gene-expression profiling, this lymphoma is divided in three cell-of-origin subtypes with distinct molecular and clinical features. Most lymphomas arise sporadically, yet familial clustering is known, suggesting a genetic contribution to disease risk. Familial lymphoma cases are a valuable tool to investigate risk genes. We studied a Swiss/Japanese family with 2 sisters affected by a primary mediastinal B-cell lymphoma and a non-germinal center diffuse large B-cell lymphoma not otherwise specified, respectively. The somatic landscape of both lymphomas was marked by alterations affecting multiple components of the JAK-STAT pathway. Consequently, this pathway was constitutively activated as evidenced by high pJAK2 as well as increased nuclear pSTAT3 and pSTAT6 in malignant cells. Potential lymphoma risk variants were identified by whole exome sequencing of the germline DNA derived from siblings and unaffected family members. This analysis revealed a pathogenic variant in TIRAP, an upstream regulator of NF-κB, in both affected siblings and their mother. We observed increased B-cell proliferation in family members harboring the TIRAP p.R81C variant. B-cell proliferation correlated with TIRAP and NF-κB target gene expression, suggesting enhanced NF-κB pathway activity in TIRAP p.R81C individuals. TIRAP knockdown reduced B-cell survival and NF-κB target gene expression, particularly in individuals with TIRAP p.R81C. Functional studies revealed significantly increased NF-κB activity and resistance to stress-induced cell-death by TIRAP p.R81C. The identification of an inherited TIRAP variant provides evidence for a novel link between genetic alterations affecting the NF-κB pathway and lymphomagenesis.

Population-based outcome analysis of diffuse large B-cell lymphoma in people living with HIV infection and competent individuals.

The prognostic factors and outcome of 58 acquired immunodeficiency syndrome-related diffuse large B-cell lymphoma (AR-DLBCL) patients from the Swiss HIV Cohort Study, diagnosed from 2004 to 2011, were compared with those of 326 immunocompetent (IC)-DLBCL from the Hematology Division of the Amedeo Avogadro University (Italy) and the Oncology Institute of Southern Switzerland. Median follow-up was 6 years; 5-year overall survival (OS) was 68% (95% CI: 63%-73%) in IC-DLBCL and 63% (95% CI: 49%-75%) in AR-DLBCL (P = .220). The acquired immunodeficiency syndrome-related lymphoma international prognostic index predicted OS in AR-DLBCL. Among 148 patients younger than 61 years (40 AR-DLBCL and 108 IC-DLBCL) treated with RCHOP/RCHOP-like regimens, 20 IC-DLBCL and 9 AR-DLBCL patients died and OS was not significantly different. A higher proportion of early deaths occurred in the AR-DLBCL: indeed, 1-year OS was 94% (95% CI: 87%-97%) in IC-DLBCL and 82% (95% CI: 66%-91%) in AR-DLBCL patients. After rituximab and active antiretroviral therapy introduction, AR-DLBCL and IC-DLBCL patients treated with curative intent have similar long-term survival.

A pattern-based approach to reactive lymphadenopathies.

A crucial task in histopathological examination of enlarged lymph nodes is to discriminate malignant form benign processes. The central importance of this issue is reflected by the fact that benign lymphadenopathies mistaken for lymphomas belong to the most commonly misdiagnosed cancers. In addition, recognition of distinct histopathological patterns of reactive lymph node changes narrow down the potential number of causative agents, especially of those that can be specifically identified by means of often very resource-consuming ancillary techniques; thus, the more precise the differential diagnosis established upon histopathological examination is, the more targetable and efficient the application of these techniques will be. This review provides a synopsis on a histopathological pattern-based approach towards reactive lymphadenopathies.

mTORC1/autophagy-regulated MerTK in mutant BRAFV600 melanoma with acquired resistance to BRAF inhibition.

BRAF inhibitors (BRAFi) and the combination therapy of BRAF and MEK inhibitors (MEKi) were recently approved for therapy of metastatic melanomas harbouring the oncogenic BRAFV600 mutation. Although these therapies have shown pronounced therapeutic efficacy, the limited durability of the response indicates an acquired drug resistance that still remains mechanistically poorly understood at the molecular level. We conducted transcriptome gene profiling in BRAFi-treated melanoma cells and identified that Mer tyrosine kinase (MerTK) is specifically upregulated. MerTK overexpression was demonstrated not only in melanomas resistant to BRAFi monotherapy (5 out of 10 samples from melanoma patients) but also in melanoma resistant to BRAFi+MEKi (1 out of 3), although MEKi alone does not affect MerTK. Mechanistically, BRAFi-induced activation of Zeb2 stimulates MerTK in BRAFV600 melanoma through mTORC1-triggered activation of autophagy. Co-targeting MerTK and BRAFV600 significantly reduced tumour burden in xenografted mice, which was pheno-copied by co-inhibition of autophagy and mutant BRAFV600.

The clinicopathologic spectrum of mature aggressive B cell lymphomas.

Our understanding of mature aggressive B cell lymphomas has evolved significantly in the last years as reflected in the 2016 update of the WHO lymphoma classification. A main topic of the 2016 European Association for Haematopathology/Society of Hematopathology lymphoma workshop in Basel therefore was the clinicopathological spectrum of mature aggressive B cell lymphomas with the exception of conventional diffuse large B cell lymphoma. In this review, we summarize two sessions dedicated to "high-grade B cell lymphomas, with MYC and BCL2 and/or BCL6 rearrangements (so-called double/triple-hit lymphomas)" and "high-grade B cell lymphomas, NOS" as defined in the 2016 update of the WHO lymphoma classification, Burkitt lymphoma and related neoplasms, and terminally differentiated aggressive B cell lymphomas. One focus was on cases of Burkitt lymphoma with unusual clinical features such as spontaneous regression or association with immunosuppression, and the new provisional category of Burkitt-like lymphoma with 11q aberration. The large numbers of cases submitted for the new high-grade categories with or without genetic "double/triple hit" demonstrated the broad clinical and pathological spectrum of this group and gave ample opportunity for discussion. In this review, current definitions and our understanding of the main high-grade categories, potential problem areas, and suggestions for the immunophenotypic and genetic work-up of these neoplasms are discussed and illustrated by many interesting and challenging cases submitted to the workshop.

Histiocytic and dendritic cell neoplasms: what have we learnt by studying 67 cases.

Tumors derived from histiocytic and dendritic cells encompass a large and heterogeneous group of neoplastic and reactive conditions, and their diagnosis is challenging both for pathologists and clinicians. Diagnosis is based on morphological and phenotypical findings, but hybrid features are not uncommon. Furthermore, recent studies uncovered the molecular mechanisms driving some of these tumors, improving diagnostic adequacy, and providing the basis for effective therapeutic breakthroughs.Sixty-seven cases were submitted to the accessory cell and histiocytic neoplasms session at the European Association of Haematopathology/Society for Hematopathology workshop 2016 held in Basel, Switzerland. The cases included histiocytic sarcomas (HS), Langerhans cell tumors (LCT), Erdheim-Chester disease, interdigitating dendritic cell sarcomas (IDCS), indeterminate dendritic cell tumors (IND-DCT), follicular dendritic cell sarcomas, and blastic plasmacytoid dendritic cell neoplasms. Rosai-Dorfman disease and, more rare, conditions such as ALK-positive histiocytosis were also submitted. These cases illustrated classical and unexpected features at morphological, phenotypical, and molecular levels, providing a valuable compendium for pathologists confronting with these tumors.The paper summarizes the most notable features of every single group of diseases, with comments about the most challenging issues, in the attempt to provide practical indications for their recognition.

Genetic background and evolution of relapses in aggressive B-cell lymphomas.

Relapses of aggressive B-cell lymphomas pose a higher risk to affected patients because of potential treatment resistance and usually rapid tumor growth. Recent advances, such as targeting Bruton tyrosine kinase, have provided promising results in small numbers of cases, but treatment for the majority of patients remains challenging and outcomes are generally poor. A number of recent studies have utilized state-of-the-art genomic technologies in an attempt to better understand tumor genome evolution during relapse and to identify relapse-specific genetic alterations. It has been found that in some settings (e.g. diffuse large B-cell lymphomas in immunocompromised patients, secondary diffuse large B-cell lymphomas as Richter transformations) a significant part of the recurrences are clonally-unrelated de novo neoplasms, which might have distinct genomic and drug sensitivity profiles as well as different prognoses. Similar to earlier findings in indolent lymphomas, genetic tumor evolution of clonally-related relapsing aggressive B-cell lymphomas is predominantly characterized by two patterns: early divergence from a common progenitor and late divergence/linear evolution from a primary tumor. The clinical implications of these distinct patterns are not yet clear and will require additional investigation; however, it is plausible that these two patterns of recurrence are linked to different treatment-resistance mechanisms. Attempts to identify drivers of relapses result in a very heterogeneous list of affected genes and pathways as well as epigenetic mechanisms and suggest many ways of how recurrent tumors can adapt to treatment and expand their malignant properties.

Diagnostic Utility of Lymphoid Enhancer Binding Factor 1 Immunohistochemistry in Small B-Cell Lymphomas.

OBJECTIVES: Recent studies have shown that lymphoid enhancer binding factor 1 (LEF1) is a useful marker for chronic lymphocytic B-cell leukemia (CLL)/small lymphocytic lymphoma. Yet, it is not still being widely used in a diagnostic setting. In this study, we document the experience with LEF1 immunohistochemistry during routine diagnostics. METHODS: In total, 191 B-cell lymphoma cases from Hammersmith Hospital, Imperial College NHS Healthcare Trust (London, UK) were investigated by immunohistochemistry for LEF1 during routine diagnostic workup. These cases included both bone marrow trephines and lymph node biopsy specimens. The monoclonal antibody clone EPR2029Y was used. RESULTS: LEF1 expression was strong and diffuse (>70% of cells) in most cases. Few CLL cases showed a staining in proliferation centers only. Seventy-seven of 80 CLL cases expressed LEF1. Other entities expressing LEF1 included one of 38 follicular lymphomas, two of 33 marginal zone lymphomas, and one diffuse large B-cell lymphoma with a background of follicular lymphoma grade 3B. Sensitivity for LEF1 for the diagnosis of CLL was 0.96, and specificity was 0.93. CONCLUSIONS: In this study, we could demonstrate the diagnostic utility of LEF1. LEF1 is a sensitive and specific marker for CLL and is helpful in the diagnosis of diagnostically challenging small B-cell lymphomas.

Mutational landscape of B-cell post-transplant lymphoproliferative disorders.

It is currently unclear whether post-transplant diffuse large B-cell lymphomas (PT-DLBCL) display a similar genomic landscape as DLBCL in immunocompetent patients (IC-DLBCL). We investigated 50 post-transplant lymphoproliferative disorders (PTLDs) including 37 PT-DLBCL samples for somatic mutations frequently observed in IC-DLBCL. Targeted Next Generation Sequencing (NGS) using the Ion Torrent platform and a customized panel of 68 genes was performed on genomic DNA. Non-tumoural tissue was sequenced to exclude germline variants in cases where available. A control cohort of 76 IC-DLBCL was available for comparative analyses. In comparison to IC-DLBCLs, PT-DLBCL showed more frequent mutations of TP53 (P = 0·004), and absence of ATM and B2M mutations (P = 0·004 and P = 0·016, respectively). In comparison to IC-DLBCLs, Epstein-Barr virus (EBV)+ PT-DLBCL had fewer mutated genes (P = 0·007) and particularly fewer mutations in nuclear factor-κB pathway-related genes (P = 0·044). TP53 mutations were more frequent in EBV- PT-DLBCL as compared to IC-DLBCL (P = 0·001). Germinal centre B cell (GCB) subtype of PT-DLBCL had fewer mutations and mutated genes than GCB-IC-DLBCLs (P = 0·048 and 0·04 respectively). Polymorphic PTLD displayed fewer mutations as compared to PT-DLBCL (P = 0·001). PT-DLBCL differs from IC-DLBCL with respect to mutations in genes related to DNA damage control and immune-surveillance, and EBV association is likely to have a bearing on the mutational pattern.

Mutations of CREBBP and SOCS1 are independent prognostic factors in diffuse large B cell lymphoma: mutational analysis of the SAKK 38/07 prospective clinical trial cohort.

BACKGROUND/PURPOSE: Recently, the mutational background of diffuse large B cell lymphoma (DLBCL) has been revealed, identifying specific genetic events that drive lymphomagenesis. However, the prognostic value of these mutations remains to be determined. Prognostic biomarkers in DLBCL are urgently needed, since the current clinical parameter-based factors (e.g., International Prognostic Index (IPI)) are insufficient, particularly in identifying patients with poor prognosis who might benefit from alternative treatments. METHODS: We investigated the prognostic value of somatic mutations in DLBCL in a clinical trial (NCT00544219) patient cohort homogenously treated with six cycles of rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisone (R-CHOP), followed by two cycles of R (R-CHOP-14). The primary endpoint was event-free survival (EFS) at 2 years. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Targeted high-throughput sequencing (HTS) of tumor genomic DNA was performed on all exons or hotspots of 68 genes frequently mutated in B cell lymphomas. Mutational data was correlated with the endpoints to identify prognostic associations. RESULTS: Targeted HTS detected somatic mutations in 71/76 (93%) of investigated cases. The most frequently mutated genes were KMT2D, SOCS1, GNA13, and B2M. Survival analysis revealed that CREBBP- and EP300-mutated cases had significantly worse OS, PFS, and EFS. In addition, ATM mutations predicted worse outcomes for all three clinical endpoints in germinal center B cell-like DLBCL. In contrast, SOCS1 mutations were associated with better PFS. On multivariable analysis taken into account IPI and failure to achieve complete remission, CREBBP and EP300 mutations remained significant to predict worse OS, PFS, and EFS. CONCLUSION: Targeted mutation analysis of a uniformly treated prospective clinical trial DLBCL cohort identifies tumor-based genetic prognostic markers that could be useful in the clinical management of such patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT00544219.

Long-term observation reveals high-frequency engraftment of human acute myeloid leukemia in immunodeficient mice.

Repopulation of immunodeficient mice remains the primary method for functional assessment of human acute myeloid leukemia. Published data report engraftment in ~40-66% of cases, mostly of intermediate- or poor-risk subtypes. Here we report that extending follow-up beyond the standard analysis endpoints of 10 to 16 weeks after transplantation permitted leukemic engraftment from nearly every case of xenotransplanted acute myeloid leukemia (18/19, ~95%). Xenogeneic leukemic cells showed conserved immune pheno-types and genetic signatures when compared to corresponding pre-transplant cells and, furthermore, were able to induce leukemia in re-transplantation assays. Importantly, bone marrow biopsies taken at standardized time points failed to detect leukemic cells in 11/18 of cases that later showed robust engraftment (61%, termed "long-latency engrafters"), indicating that leukemic cells can persist over months at undetectable levels without losing disease-initiating properties. Cells from favorable-risk leukemia subtypes required longer to become detectable in NOD/SCID/IL2Rγnull mice (27.5±9.4 weeks) than did cells from intermediate-risk (21.9±9.4 weeks, P<0.01) or adverse-risk (17±7.6 weeks; P<0.0001) subtypes, explaining why the engraftment of the first was missed with previous protocols. Mechanistically, leukemic cells engrafting after a prolonged latency showed inferior homing to the bone marrow. Finally, we applied our model to favorable-risk acute myeloid leukemia with inv(16); here, we showed that CD34+ (but not CD34-) blasts induced robust, long-latency engraftment and expressed enhanced levels of stem cell genes. In conclusion, we provide a model that allows in vivo mouse studies with a wide range of molecular subtypes of acute myeloid leukemia subtypes which were previously considered not able to engraft, thus enabling novel insights into leukemogenesis.