Burkitt lymphoma (BL) is a highly aggressive, rapidly growing B cell non-Hodgkin lymphoma, which manifests in several subtypes including sporadic, endemic, and immunodeficiency-associated forms. Pathologically, BL is classically characterized by translocations of chromosomes 8 and 14 resulting in upregulation of the c-myc protein transcription factor with upregulation of cell proliferation. BL affects nearly every organ system, most commonly the abdomen and pelvis in the sporadic form. Imaging using a multimodality approach plays a crucial role in the management of BL from diagnosis, staging, and evaluation of treatment response to therapy-related complications with ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography playing roles. In this article, we review the pathobiology and classification of BL, illustrate a multimodality imaging approach in evaluating common and uncommon sites of involvement within the trunk and head and neck, and review common therapies and treatment-related complications.

Natural killer cells from acute myeloid leukaemia patients (AML-NK) show a dramatic impairment in cytotoxic activity. The exact reasons for this dysfunction are not fully understood. Here we show that the glycogen synthase kinase beta (GSK3β) expression is elevated in AML-NK cells. Interestingly, GSK3 overexpression in normal NK cells impairs their ability to kill AML cells, while genetic or pharmacological GSK3 inactivation enhances their cytotoxic activity. Mechanistic studies reveal that the increased cytotoxic activity correlates with an increase in AML-NK cell conjugates. GSK3 inhibition promotes the conjugate formation by upregulating LFA expression on NK cells and by inducing ICAM-1 expression on AML cells. The latter is mediated by increased NF-κB activation in response to TNF-α production by NK cells. Finally, GSK3-inhibited NK cells show significant efficacy in human AML mouse models. Overall, our work provides mechanistic insights into the AML-NK dysfunction and a potential NK cell therapy strategy.

Macrophages depend on colony stimulating factor 1 (also known as M-CSF) for their growth and differentiation, but the requirements for intracellular signals that lead to macrophage differentiation and function remain unclear. M-CSF is known to activate ERK1 and ERK2, but the importance of this signaling pathway in macrophage development is unknown. In these studies, we characterized a novel model of Erk1 -/- Erk2 flox/flox Lyz2 Cre/Cre mice in which the ERK2 isoform is deleted from macrophages in the background of global ERK1 deficiency. Cultures of M-CSF-stimulated bone marrow precursors from these mice yielded reduced numbers of macrophages. Whereas macrophages developing from M-CSF-stimulated bone marrow of Erk2 flox/flox Lyz2 Cre/Cre mice showed essentially complete loss of ERK2 expression, the reduced number of macrophages that develop from Erk1 -/- Erk2 flox/flox Lyz2 Cre/Cre bone marrow show retention of ERK2 expression, indicating selective outgrowth of a small proportion of precursors in which Cre-mediated deletion failed to occur. The bone marrow of Erk1 -/- Erk2 flox/flox Lyz2 Cre/Cre mice was enriched for CD11b+ myeloid cells, CD11bhi Gr-1hi neutrophils, Lin- c-Kit+ Sca–1+ hematopoietic stem cells, and Lin- c-Kit+ CD34+ CD16/32+ granulocyte-macrophage progenitors. Culture of bone marrow Lin- cells under myeloid-stimulating conditions yielded reduced numbers of monocytes. Collectively, these data indicate that the defect in production of macrophages is not due to a reduced number of progenitors, but rather due to reduced ability of progenitors to proliferate and produce macrophages in response to M-CSF-triggered ERK signaling. Macrophages from Erk1 -/- Erk2 flox/flox Lyz2 Cre/Cre bone marrow showed reduced induction of M-CSF-regulated genes that depend on the ERK pathway for their expression. These data demonstrate that ERK1/ERK2 play a critical role in driving M-CSF-dependent proliferation of bone marrow progenitors for production of macrophages.

More than half of T-ALL patients harbor gain-of-function mutations in the intracellular domain of Notch1. Diffuse infiltration of the bone marrow commonly occurs in T-ALL and relapsed B-ALL patients, and is associated with worse prognosis. However, the mechanism of leukemia outgrowth in the marrow and the resulting biological impact on hematopoiesis are poorly understood. Here, we investigated targetable cellular and molecular abnormalities in leukemia marrow stroma responsible for the suppression of normal hematopoiesis using a T-ALL mouse model and human T-ALL xenografts. We found that actively proliferating leukemia cells inhibited normal hematopoietic stem and progenitor cell (HSPC) proliferation and homing to the peri-vascular region. In addition, leukemia development was accompanied by the suppression of the endosteum-lining osteoblast population. We further demonstrate that aberrant Notch activation in the stroma plays an important role in negatively regulating the expression of CXLC12 on osteoblasts and their differentiation. Notch blockade reversed attenuated HSPC cycling, leukemia-associated abnormal blood lineage distribution and thrombocytopenia as well as recovered osteoblast and HSPC abundance and improved the hematopoietic-supportive functions of osteoblasts. Finally, we confirmed that reduced osteoblast frequency and enhanced Notch signaling were also features of the marrow stroma of human ALL tissues. Collectively, our findings suggest that therapeutically targeting the leukemia-infiltrated hematopoietic niche may restore HSPC homeostasis and improve the outcome of ALL patients.

Notch receptor signaling is required for T cell development, but its role in NK cell development is poorly understood. We compared the ability of the five mammalian Notch ligands (Jagged1, Jagged2, Delta1, Delta3, or Delta4) to induce NK cell development from human hematopoietic progenitor cells (HPCs). CD34+ HPCs were cultured with OP9 stromal cell lines transduced with one of the Notch ligands or with OP9 stromal cells alone, in the presence of IL-7, Flt3L, and IL-15. Differentiation and expansion of CD56+CD3− cells was greatly accelerated in the presence of Jagged2, Delta-1, or Delta-4, versus culture in the absence of ligand or in the presence of Jagged1 or Delta3. At four weeks, cultures containing Jagged2, Delta1, or Delta4 contained 80–90% NK cells, with the remaining cells being CD33+ myeloid cells. Notch-induced NK (N-NK) cells resembled CD56bright NK cells in that they were CD16-, CD94−, CD117+, and KIR-. They also expressed NKp30, NKp44, NKp46, 2B4, and DNAM-1, with partial expression of NKG2D. The N-NK cells displayed cytotoxic activity against the K562 and RPMI-8226 cell lines, at levels similar to activated peripheral blood NK cells, although killing of Daudi cells was not present. N-NK cells were also capable of IFN-γ secretion. Thus, Notch ligands have differential ability to induce and expand immature but functional NK cells from CD34+ HPCs. The use of Notch ligands to generate functional NK cells in vitro may be significant for cellular therapy purposes.

We sought to identify biologic indicators of prognosis in a series of 94 follicular lymphoma (FL) patients, focusing on markers of the host immune response as well as of B-cell maturation. Immune response was assessed with immunostains for CD68 (for lymphoma-associated macrophages, LAMs) and FOXP3 (regulatory T-cells). Lymphoma cells were evaluated for expression of bcl-2, CD10, and MUM-1. Clinical data were obtained for FLIPI, presence of bulky disease, presence of B-symptoms, treatment, and overall survival (OS). For the 69 initially treated patients, extrafollicular CD68+ cells (ef-CD68) and follicular FOXP3+ cells (f-FOXP3) were associated with shorter OS, while receipt of rituximab was associated with longer OS. Multivariable analysis showed ef-CD68 was the only independent factor associated with shorter OS. In subset analysis, ef-CD68 remained statistically significant in rituximab-naïve but not rituximab-treated patients. We confirm the importance of LAMs and f-FOXP3 as predictors of OS in FL.

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BackgroundNeoplasms derived from plasmacytoid dendritic cells (PDCs) are currently divided into two broad categories: mature PDC proliferations associated with myeloid neoplasms (MPDMN) and blastic plasmacytoid dendritic cell neoplasm (BPDCN); only BPDCN is recognized in the WHO 2016 classification of hematopoietic neoplasms. We present seven patients with high grade myeloid neoplasms (MNs), mostly acute leukemias, having a spectrum of PDC differentiation and not fitting with MPDMN or BPDCN.MethodsWe analyzed seven MN cases having increased myeloblasts and prominent CD56‐negative PDC proliferations comprising 5–26% of bone marrow or blood cellularity as measured by flow cytometry. The cases included five acute myeloid leukemia (three FAB M4 subtype, two unclassified), one mixed phenotype acute leukemia, and one case of unclassified MN.ResultsSix cases demonstrated immunophenotypic evidence of PDC differentiation from leukemic blasts, based on variable expression of CD34, CD45, CD123, and CD304 by the leukemic cells. Four cases had circulating PDC populations in blood. None of the cases met clinical or pathologic criteria for BPDCN. Morphologic review was available for four acute leukemia cases and demonstrated either nodular or interstitial infiltrates of PDCs. All cases had an aggressive clinical course, and three cases had FLT3 ITD mutation.ConclusionsThese cases demonstrate that high grade MNs, in particular AML, can exhibit PDC differentiation, with or without monocytic differentiation, in a manner distinct from MPDMN or BPDCN. The existence of MNs with immature PDC proliferations suggests that there is a broader spectrum of PDC‐associated neoplasms than currently recognized. © 2019 International Clinical Cytometry Society