Genome-scale clustered regularly interspaced short palindromic repeats screen identifies nucleotide metabolism as an actionable therapeutic vulnerability in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common malignancy that develops in patients with ataxia-telangiectasia, a cancer-predisposing inherited syndrome characterized by inactivating germline ATM mutations. ATM is also frequently mutated in sporadic DLBCL. To investigate lymphomagenic mechanisms and lymphoma-specific dependencies underlying defective ATM, we applied ribonucleic acid (RNA)-seq and genome-scale loss-offunction clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 screens to systematically interrogate B-cell lymphomas arising in a novel murine model (Atm-/-nu-/-) with constitutional Atm loss, thymic aplasia but residual T-cell populations. Atm-/-nu-/-lymphomas, which phenotypically resemble either activated B-cell-like or germinal center Bcell-like DLBCL, harbor a complex karyotype, and are characterized by MYC pathway activation. In Atm-/-nu-/-lymphomas, we discovered nucleotide biosynthesis as a MYCdependent cellular vulnerability that can be targeted through the synergistic nucleotidedepleting actions of mycophenolate mofetil (MMF) and the WEE1 inhibitor, adavosertib (AZD1775). The latter is mediated through a synthetically lethal interaction between RRM2 suppression and MYC dysregulation that results in replication stress overload in Atm-/-nu-/-lymphoma cells. Validation in cell line models of human DLBCL confirmed the broad applicability of nucleotide depletion as a therapeutic strategy for MYC-driven DLBCL independent of ATM mutation status. Our findings extend current understanding of lymphomagenic mechanisms underpinning ATM loss and highlight nucleotide metabolism as a targetable therapeutic vulnerability in MYC-driven DLBCL.

Testing for t(3;8) in MYC/BCL6-rearranged large B-cell lymphoma identifies a high-risk subgroup with inferior survival.

ABSTRACT: A reciprocal t(3;8) BCL6::MYC fusion is common in large B-cell lymphoma (LBCL) with MYC and BCL6 disruption. These pseudo-double-hit cases are not adverse, whereas t(3;8)-MYC/BCL6 lymphoma has an inferior prognosis relative to other MYC-rearranged LBCL.

MUM1/IRF4 is Highly Expressed in Dermatopathic Lymphadenopathy: Potential Utility in Diagnosis and Differential Diagnosis.

Dermatopathic lymphadenopathy (DL) is a distinctive type of lymph node hyperplasia that typically occurs in the setting of chronic dermatologic diseases. DL generally self-resolves following disappearance of the underlying skin stimulus and does not require any specific therapy. We recently observed multiple myeloma oncogene 1/interferon regulatory factor 4 (MUM1/IRF4) expression in a case of DL using immunohistochemical methods. The goal of this study was to systematically assess DL cases for MUM1/IRF4 expression and to survey other histiocytic and Langerhans cell lesions. We particularly focused on Langerhans cell histiocytosis (LCH) because the differential diagnosis of DL versus LCH in lymph nodes can be challenging. We identified high expression of MUM1/IRF4 in all 22 cases of DL tested. Specifically, MUM1/IRF4+ dendritic cells comprised 50% to 90% (median, 80%) of all dendritic cells in the paracortex of dermatopathic lymph nodes, always showing moderate or strong intensity. Among 10 DL cases stained for MUM1/IRF4 and langerin/CD207 using dual immunohistochemistry, MUM1/IRF4+ and langerin+ Langerhans cells represented 5% to 60% (median, 30%) of paracortical dendritic cells. MUM1/IRF4 was also positive in reactive Langerhans cells in skin biopsy specimens of all cases of spongiotic dermatitis (n=10) and normal skin (n=15), and was negative in all cases of LCH (n=24), Rosai-Dorfman disease (n=10), follicular dendritic cell sarcoma (n=5) and histiocytic sarcoma (n=4). In aggregate, our findings support the utility of MUM1/IRF4 to highlight the dendritic cells of DL and to distinguish DL from other histiocytic and Langerhans cells lesions.

Bone marrow necrosis and fat embolism syndrome in sickle cell disease during COVID-19 infection treated successfully with sequential red cell and plasma exchange.

Fat embolism syndrome (FES) is a rare life-threatening condition that is particularly seen in milder forms of sickle cell disease (SCD). Widespread systemic fat emboli are generated in the context of extensive bone marrow necrosis. Multi-organ failure with a high morbidity and mortality may quickly develop. Infection with Parvovirus B19 is a common precipitant. Here, the authors report the case of a 35-year-old Afro-Caribbean man with HbSC disease who presented with FES having tested positive for SARS-COV-2. He rapidly became critically ill and required admission to the intensive care unit for organ support. He was treated with red cell exchange and plasma exchange and made a good recovery to leave hospital at week 7.

Management of Allogeneic Stem Cell Transplantation for High-Risk AML following SARS-CoV-2 Associated Pancytopenia with Marked Bone Marrow Biopsy Alterations.

The present study describes a patient aged 70 with very high-risk AML who successfully received a nonmyeloablative matched unrelated donor allograft shortly following SARS-CoV-2 infection, which manifested with mild cough, interstitial abnormalities on chest CT, and pancytopenia with profound bone marrow biopsy histological alterations. In parallel, our study provides bone marrow biopsy data in a series of contemporary patients with serious haematological diseases who had a bone marrow biopsy performed within two weeks of PCR confirmation of SARS-CoV-2 infection. This study is notable because there are no published data describing the bone marrow biopsy changes observed in patients with haematological malignancies and SARS-CoV-2 infection. Finally, it is suggested that nonmyeloablative hematopoietic stem cell transplantation for very high-risk haematological malignancies can be successfully performed following recovery from SARS-CoV-2 infection.

First case of near haploid philadelphia negative B-Cell acute lymphoblastic leukaemia relapsing as acute myeloid leukemia following allogeneic hematopoietic stem cell transplantation.

Herein we present a female patient aged 61 with Philadelphia negative acute lymphoblastic leukaemia demonstrating near haploid karyotype and abnormal TP53 expression at diagnosis, who relapsed with lineage switch as Acute Monocytic Leukemia post allogeneic stem cell transplantation. Molecular analysis established that both neoplasms were derived from the same founder clone. The leukemic lineage switch phenomenon has recently re-attracted interest as mechanism of leukemic evasion post treatment with chimeric antigen receptor T-cells but there is paucity of data on its presence post allograft or following novel antibody treatments such as Inotuzumab Ozogamicin or Blinatumomab. Our proposition for cancer research is that near haploidy in ALL could be linked to leukemic stem cell plasticity evading stem cell transplantation and other immunotherapy approaches.

Sphingosine-1-phosphate signalling drives an angiogenic transcriptional programme in diffuse large B cell lymphoma.

Although the over-expression of angiogenic factors is reported in diffuse large B-cell lymphoma (DLBCL), the poor response to anti-VEGF drugs observed in clinical trials suggests that angiogenesis in these tumours might be driven by VEGF-independent pathways. We show that sphingosine kinase-1 (SPHK1), which generates the potent bioactive sphingolipid sphingosine-1-phosphate (S1P), is over-expressed in DLBCL. A meta-analysis of over 2000 cases revealed that genes correlated with SPHK1 mRNA expression in DLBCL were significantly enriched for tumour angiogenesis meta-signature genes; an effect evident in both major cell of origin (COO) and stromal subtypes. Moreover, we found that S1P induces angiogenic signalling and a gene expression programme that is present within the tumour vasculature of SPHK1-expressing DLBCL. Importantly, S1PR1 functional antagonists, including Siponimod, and the S1P neutralising antibody, Sphingomab, inhibited S1P signalling in DLBCL cells in vitro. Furthermore, Siponimod, also reduced angiogenesis and tumour growth in an S1P-producing mouse model of angiogenic DLBCL. Our data define a potential role for S1P signalling in driving an angiogenic gene expression programme in the tumour vasculature of DLBCL and suggest novel opportunities to target S1P-mediated angiogenesis in patients with DLBCL.

Low Expression and Promoter Hypermethylation of the Tumour Suppressor SLIT2, are Associated with Adverse Patient Outcomes in Diffuse Large B Cell Lymphoma.

SLIT2 has been classified as a major tumour suppressor gene due to its frequent inactivation in different cancer types. However, alterations of SLIT2 expression and relation to patient outcomes in diffuse large B cell lymphoma (DLBCL) remain undefined. The aim of this study was to investigate the expression and the methylation status of SLIT2 gene as well as its relation to patient outcomes in DLBCL. Immunohistochemical (IHC) staining was carried out to detect the expression of SLIT2 in a series of 108 DLBCL cases. Re-analysis of previously published dataset (GSE10846) that measured gene expression in DLBCL patients who had received CHOP or R-CHOP therapy was performed to identify associations between SLIT2 and patients survival. Laser capture microdissection was performed to isolate GC B cells and DLBCL primary tumor cells. Bisulfite treatment and methylation-specific PCR (MSP) analysis were done to assess SLIT2 promotor methylation status. We report that the expression of SLIT2 protein was reduced in a subset of DLBCL cases and this was significantly correlated with advanced clinical stage (p = 0.041) and was an independent predictor of worse overall survival (OS) (p = 0.012). Re-analysis of published gene expression data showed that reduced SLIT2 mRNA expression was significantly correlated with worse OS in R-CHOP-treated ABC DLBCL patients (p = <0.01). Hypermethylation of the SLIT2 promotor was significantly correlated with low SLIT2 expression (p = 0.009). Our results provide a novel evidence of reduced expression of SLIT2 that is associated with promoter hypermethylation and adverse outcomes in patients with DLBCL.

Regulation of S1PR2 by the EBV oncogene LMP1 in aggressive ABC-subtype diffuse large B-cell lymphoma.

The Epstein-Barr virus (EBV) is found almost exclusively in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), yet its contribution to this tumour remains poorly understood. We have focused on the EBV-encoded latent membrane protein-1 (LMP1), a constitutively activated CD40 homologue expressed in almost all EBV-positive DLBCLs and which can disrupt germinal centre (GC) formation and drive lymphomagenesis in mice. Comparison of the transcriptional changes that follow LMP1 expression with those that follow transient CD40 signalling in human GC B cells enabled us to define pathogenic targets of LMP1 aberrantly expressed in ABC-DLBCL. These included the down-regulation of S1PR2, a sphingosine-1-phosphate (S1P) receptor that is transcriptionally down-regulated in ABC-DLBCL, and when genetically ablated leads to DLBCL in mice. Consistent with this, we found that LMP1-expressing primary ABC-DLBCLs were significantly more likely to lack S1PR2 expression than were LMP1-negative tumours. Furthermore, we showed that the down-regulation of S1PR2 by LMP1 drives a signalling loop leading to constitutive activation of the phosphatidylinositol-3-kinase (PI3-K) pathway. Finally, core LMP1-PI3-K targets were enriched for lymphoma-related transcription factors and genes associated with shorter overall survival in patients with ABC-DLBCL. Our data identify a novel function for LMP1 in aggressive DLBCL. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Fatal systemic angiomatosis with widespread sclerotic skeletal changes, diagnosed with the aid of a bone marrow biopsy: the lymphatics enter the bone marrow.

A 56-year-old female presented with popliteal venous thrombosis, splenomegaly, and sclerotic bone lesions. Bone marrow biopsy showed fibrosis, proliferation of abnormal blood vessels and lymphatics, bone remodelling, and no significant changes in haematopoietic elements. Following a relatively indolent initial clinical course, one year later she rapidly deteriorated and died of respiratory failure associated with widespread disease. Ingrowth of podoplanin+ lymphatics mixed with CD34+/podoplanin- blood vessels into the bone marrow is a new finding and may be a unique feature of this disease.

Rapidly progressive intravascular primary effusion lymphoma in an HIV-positive renal transplant recipient.

We describe the clinical and post-mortem findings of a case of rapidly progressive, ultimately fatal primary effusion lymphoma (PEL) arising in an HIV-positive man 2 years after renal transplantation. Disseminated multi-organ involvement associated with a peculiar intravascular pattern of growth, as seen in this case, has only been reported once previously. This is also, to our knowledge, the first detailed description of a lymphoma arising post-transplant in an HIV-positive patient.

NK cell function is markedly impaired in patients with chronic lymphocytic leukaemia but is preserved in patients with small lymphocytic lymphoma.

Chronic lymphocytic leukemia (B-CLL) and small lymphocytic lymphoma (SLL) are part of the same disease classification but are defined by differential distribution of tumor cells. B-CLL is characterized by significant immune suppression and dysregulation but this is not typical of patients with SLL. Natural killer cells (NK) are important mediators of immune function but have been poorly studied in patients with B-CLL/SLL. Here we report for the first time the NK cell phenotype and function in patients with B-CLL and SLL alongside their transcriptional profile. We show for the first time impaired B-CLL NK cell function in a xenograft model with reduced activating receptor expression including NKG2D, DNAM-1 and NCRs in-vitro. Importantly, we show these functional differences are associated with transcriptional downregulation of cytotoxic pathway genes, including activating receptors, adhesion molecules, cytotoxic molecules and intracellular signalling molecules, which remain intact in patients with SLL. In conclusion, NK cell function is markedly influenced by the anatomical site of the tumor in patients with B-CLL/SLL and lymphocytosis leads to marked impairment of NK cell activity. These observations have implications for treatment protocols which seek to preserve immune function by limiting the exposure of NK cells to tumor cells within the peripheral circulation.

Synchronous Upper and Lower Gastrointestinal Mucosa-Associated Lymphoid Tissue Lymphomas.

Mucosa-associated lymphoid tissue lymphoma (MALToma) is a subtype of B-cell non-Hodgkin's lymphoma, comprising ∼17% of all gastrointestinal (GI) tract lymphomas. It is associated with chronic inflammation and autoimmunity, for example Helicobacter pylori gastritis and Sjogren's syndrome, respectively. Approximately 50% of GI MALTomas occur in the stomach, with small bowel and colonic lesions being less frequent. Synchronous upper and lower GI MALTomas occur rarely, with few cases reported. We present the case of a 73-year-old patient who presented with change in bowel habit and was found to have synchronous multifocal upper and lower GI MALTomas, which did not respond to H. pylori cure or to rituximab therapy, but did respond to a combination of surgery and chemotherapy with rituximab and bendamustine.

Sclerosing angiomatoid nodular transformation of the spleen.

Sclerosing angiomatoid nodular transformation (SANT) of spleen is a very rare benign entity with unknown etiology. Here, we report this unusual case in a fit middle-aged gentleman and discuss various diagnostic modalities along with the management of this condition.

T-cell number and subtype influence the disease course of primary chronic lymphocytic leukaemia xenografts in alymphoid mice.

Chronic lymphocytic leukaemia (CLL) cells require microenvironmental support for their proliferation. This can be recapitulated in highly immunocompromised hosts in the presence of T cells and other supporting cells. Current primary CLL xenograft models suffer from limited duration of tumour cell engraftment coupled with gradual T-cell outgrowth. Thus, a greater understanding of the interaction between CLL and T cells could improve their utility. In this study, using two distinct mouse xenograft models, we investigated whether xenografts recapitulate CLL biology, including natural environmental interactions with B-cell receptors and T cells, and whether manipulation of autologous T cells can expand the duration of CLL engraftment. We observed that primary CLL xenografts recapitulated both the tumour phenotype and T-cell repertoire observed in patients and that engraftment was significantly shorter for progressive tumours. A reduction in the number of patient T cells that were injected into the mice to 2-5% of the initial number or specific depletion of CD8(+) cells extended the limited xenograft duration of progressive cases to that characteristic of indolent disease. We conclude that manipulation of T cells can enhance current CLL xenograft models and thus expand their utility for investigation of tumour biology and pre-clinical drug assessment.

Reduced intensity allogeneic stem cell transplant for treatment of blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm is a rare, aggressive tumor characterized by skin and/or marrow infiltration by CD4(+) CD56(+) cells. Historically, the tumor was variably thought to arise from either monocytes, T cells or NK cells giving rise to terms such as CD4(+)/CD56(+) acute monoblastic leukemia, primary cutaneous CD4(+)/CD56(+) hematodermic tumor and blastic NK-cell lymphoma. Whilst considerable progress has been made in understanding the histogenesis, the best modality of treatment remains to be defined. We are therefore reporting this case which was successfully treated with a T-deplete allogeneic transplant and the patient is currently alive and in remission 4 years post transplant.