Translational development of difluoromethylornithine (DFMO) for the treatment of neuroblastoma

Neuroblastoma is a childhood tumor in which MYC oncogenes are commonly activated to drive tumor progression. Survival for children with high-risk neuroblastoma remains poor despite treatment that incorporates high-dose chemotherapy, stem cell support, surgery, radiation therapy and immunotherapy. More effective and less toxic treatments are sought and one approach under clinical development involves re-purposing the anti-protozoan drug difluoromethylornithine (DFMO; Eflornithine) as a neuroblastoma therapeutic. DFMO is an irreversible inhibitor of ornithine decarboxylase (Odc), a MYC target gene, bona fide oncogene, and the rate-limiting enzyme in polyamine synthesis. DFMO is approved for the treatment of Trypanosoma brucei gambiense encephalitis (“African sleeping sickness”) since polyamines are essential for the proliferation of these protozoa. However, polyamines are also critical for mammalian cell proliferation and the finding that MYC coordinately regulates all aspects of polyamine metabolism suggests polyamines may be required to support cancer promotion by MYC. Pre-emptive blockade of polyamine synthesis is sufficient to block tumor initiation in an otherwise fully penetrant transgenic mouse model of neuroblastoma driven by MYCN, underscoring the necessity of polyamines in this process. Moreover, polyamine depletion regimens exert potent anti-tumor activity in pre-clinical models of established neuroblastoma as well, in combination with numerous chemotherapeutic agents and even in tumors with unfavorable genetic features such as MYCN, ALK or TP53 mutation. This has led to the testing of DFMO in clinical trials for children with neuroblastoma. Current trial designs include testing lower dose DFMO alone (2,000 mg/m2/day) starting at the completion of standard therapy, or higher doses combined with chemotherapy (up to 9,000 mg/m2/day) for patients with relapsed disease that has progressed. In this review we will discuss important considerations for the future design of DFMO-based clinical trials for neuroblastoma, focusing on the need to better define the principal mechanisms of anti-tumor activity for polyamine depletion regimens. Putative DFMO activities that are both cancer cell intrinsic (targeting the principal oncogenic driver, MYC) and cancer cell extrinsic (altering the tumor microenvironment to support anti-tumor immunity) will be discussed. Understanding the mechanisms of DFMO activity are critical in determining how it might be best leveraged in upcoming clinical trials. This mechanistic approach also provides a platform by which iterative pre-clinical testing using translational tumor models may complement our clinical approaches

Thymic Stromal-Cell Abnormalities and Dysregulated T-Cell Development in IL-2-Deficient Mice

The role that interleukin-2 (IL-2) plays in T-cell development is not known. To address this issue, we have investigated the nature of the abnormal thymic development and autoimmune disorders that occurs in IL-2-deficient (IL-2(–/–)) mice. After 4 to 5 weeks of birth, IL-2(–/–) mice progressively develop a thymic disorder resulting in the disruption of thymocyte maturation. This disorder is characterized by a dramatic reduction in cellularity, the selective loss of immature CD4(-)8(-) (double negative; DN) and CD4(+)8(+) (double positive; DP) thymocytes and defects in the thymic stromal-cell compartment. Immunohistochemical staining of sections of thymuses from specific pathogen-free and germ-free IL-2(–/–) mice of various ages showed a progressive ,loss of cortical epithelial cells, MHC class II-expressing cells, monocytes, and macrophages. Reduced numbers of macrophages were apparent as early as week after birth. Since IL-2(–/–) thymocyte progenitor populations could mature normally on transfer into a normal thymus, the thymic defect in IL-2(–/–) mice appears to be due to abnormalities among thymic stromal cells. These results underscore the role of IL-2 in maintaining functional microenvironments that are necessary to support thymocyte growth, development, and selection

Emerging Infections and Pertinent Infections Related to Travel for Patients with Primary Immunodeficiencies

Erratum: J Clin Immunol. 2017 Oct;37(7):693-694. doi: 10.1007/s10875-017-0436-0.In today's global economy and affordable vacation travel, it is increasingly important that visitors to another country and their physician be familiar with emerging infections, infections unique to a specific geographic region, and risks related to the process of travel. This is never more important than for patients with primary immunodeficiency disorders (PIDD). A recent review addressing common causes of fever in travelers provides important information for the general population Thwaites and Day (N Engl J Med 376:548-560, 2017). This review covers critical infectious and management concerns specifically related to travel for patients with PIDD. This review will discuss the context of the changing landscape of infections, highlight specific infections of concern, and profile distinct infection phenotypes in patients who are immune compromised. The organization of this review will address the environment driving emerging infections and several concerns unique to patients with PIDD. The first section addresses general considerations, the second section profiles specific infections organized according to mechanism of transmission, and the third section focuses on unique phenotypes and unique susceptibilities in patients with PIDDs. This review does not address most parasitic diseases. Reference tables provide easily accessible information on a broader range of infections than is described in the text.Peer reviewe

Role of interleukin 2 in the development of MHC class II -restricted thymocytes

While TCR:MHC interactions play an essential role in determining the fate of developing thymocytes during selection, the types of APC, costimulatory inputs, and soluble factors encountered by these thymocytes may also modulate the final outcome. Although IL2 had been proposed as a growth factor for developing thymocytes due to its proliferative effect on peripheral T cells, recent evidence implicates IL2 in limiting peripheral T cell responses via AIM Indeed, the T cell-mediated autoimmune disorders that spontaneously develop in IL2−/− and IL2Rα−/− mice may be consequences of an inability of peripheral CD4 T cells to undergo AICD. Whether IL2 plays a similar limiting role in the thymus is unknown. We examined the consequences of IL2-deficiency on thymic architecture and thymocyte development, and investigated the developmental potential of IL2−/− thymocytes within a normal thymic microenvironment. In considering the consequences of the loss of IL2 on thymocyte negative selection, we find that TCR engagement results in the induction of thymocyte apoptosis concomitant with in situ IL2 production, expression of high affinity IL2Rs, and internalization of IL2 protein. These findings demonstrate that the inefficient anti-CD3 mediated thymocyte apoptosis observed in IL2 −/− mice is consistent with a role for IL2/IL2R interactions in the negative selection of thymocytes. Moreover, the restoration of cortical thymocyte apoptosis upon administration of exogenous IL2 and the inhibition of Ag-mediated thymocyte apoptosis in TCR-transgenic mice following administration of IL2R-blocking antibodies strongly corroborates this hypothesis. Our results also suggest that the maximal production of IL2 involves a complex interaction between thymic APC, immature, and mature thymocytes—an interaction which underscores the importance of intact thymic microarchitecture in ensuring efficient thymocyte negative selection. When combined with the finding that IL2 is required for the maintenance of some thymic APC populations, our results help explain the loss of immature thymocytes observed in older IL2 −/− mice. We conclude by presenting a model to explain the multiple roles of IL2 in thymocyte development, the consequences of its loss on central and peripheral tolerance, and the candidate cellular elements and environmental niches necessary for the efficient removal of autoreactive thymocytes

Role of interleukin 2 in the development of MHC class II -restricted thymocytes

While TCR:MHC interactions play an essential role in determining the fate of developing thymocytes during selection, the types of APC, costimulatory inputs, and soluble factors encountered by these thymocytes may also modulate the final outcome. Although IL2 had been proposed as a growth factor for developing thymocytes due to its proliferative effect on peripheral T cells, recent evidence implicates IL2 in limiting peripheral T cell responses via AIM Indeed, the T cell-mediated autoimmune disorders that spontaneously develop in IL2−/− and IL2Rα−/− mice may be consequences of an inability of peripheral CD4 T cells to undergo AICD. Whether IL2 plays a similar limiting role in the thymus is unknown. We examined the consequences of IL2-deficiency on thymic architecture and thymocyte development, and investigated the developmental potential of IL2−/− thymocytes within a normal thymic microenvironment. In considering the consequences of the loss of IL2 on thymocyte negative selection, we find that TCR engagement results in the induction of thymocyte apoptosis concomitant with in situ IL2 production, expression of high affinity IL2Rs, and internalization of IL2 protein. These findings demonstrate that the inefficient anti-CD3 mediated thymocyte apoptosis observed in IL2 −/− mice is consistent with a role for IL2/IL2R interactions in the negative selection of thymocytes. Moreover, the restoration of cortical thymocyte apoptosis upon administration of exogenous IL2 and the inhibition of Ag-mediated thymocyte apoptosis in TCR-transgenic mice following administration of IL2R-blocking antibodies strongly corroborates this hypothesis. Our results also suggest that the maximal production of IL2 involves a complex interaction between thymic APC, immature, and mature thymocytes—an interaction which underscores the importance of intact thymic microarchitecture in ensuring efficient thymocyte negative selection. When combined with the finding that IL2 is required for the maintenance of some thymic APC populations, our results help explain the loss of immature thymocytes observed in older IL2 −/− mice. We conclude by presenting a model to explain the multiple roles of IL2 in thymocyte development, the consequences of its loss on central and peripheral tolerance, and the candidate cellular elements and environmental niches necessary for the efficient removal of autoreactive thymocytes

Antitumor Responses of Invariant Natural Killer T Cells

Natural killer T (NKT) cells are innate-like lymphocytes that were first described in the late 1980s. Since their initial description, numerous studies have collectively shed light on their development and effector function. These studies have highlighted the unique requirements for the activation of these lymphocytes and the functional responses that distinguish these cells from other effector lymphocyte populations such as conventional T cells and NK cells. This body of literature suggests that NKT cells play diverse nonredundant roles in a number of disease processes, including the initiation and propagation of airway hyperreactivity, protection against a variety of pathogens, development of autoimmunity, and mediation of allograft responses. In this review, however, we focus on the role of a specific lineage of NKT cells in antitumor immunity. Specifically, we describe the development of invariant NKT (iNKT) cells and the factors that are critical for their acquisition of effector function. Next, we delineate the mechanisms by which iNKT cells influence and modulate the activity of other immune cells to directly or indirectly affect tumor growth. Finally, we review the successes and failures of clinical trials employing iNKT cell-based immunotherapies and explore the future prospects for the use of such strategies

Cutting Edge: Murine NK Cells Degranulate and Retain Cytotoxic Function without Store-Operated Calcium Entry

International audienceSustained Ca2+ signaling, known as store-operated calcium entry (SOCE), occurs downstream of immunoreceptor engagement and is critical for cytotoxic lymphocyte signaling and effector function. CD8(+) T cells require sustained Ca2+ signaling for inflammatory cytokine production and the killing of target cells; however, much less is known about its role in NK cells. In this study, we use mice deficient in stromal interacting molecules 1 and 2, which are required for SOCE, to examine the contribution of sustained Ca2+ signaling to murine NK cell function. Surprisingly, we found that, although SOCE is required for NK cell IFN-gamma production in an NFAT-dependent manner, NK cell degranulation/cytotoxicity and tumor rejection in vivo remained intact in the absence of sustained Ca2+ signaling. Our data suggest that mouse NK cells use different signaling mechanisms for cytotoxicity compared with other cytotoxic lymphocytes