Combining Immunocytokine and Ex Vivo Activated NK Cells as a Platform for Enhancing Graft-Versus-Tumor Effects Against GD2+ Murine Neuroblastoma

Management for high-risk neuroblastoma (NBL) has included autologous hematopoietic stem cell transplant (HSCT) and anti-GD2 immunotherapy, but survival remains around 50%. The aim of this study was to determine if allogeneic HSCT could serve as a platform for inducing a graft-versus-tumor (GVT) effect against NBL with combination immunocytokine and NK cells in a murine model. Lethally irradiated C57BL/6 (B6) x A/J recipients were transplanted with B6 bone marrow on Day +0. On day +10, allogeneic HSCT recipients were challenged with NXS2, a GD2+ NBL. On days +14-16, mice were treated with the anti-GD2 immunocytokine hu14.18-IL2. In select groups, hu14.18-IL2 was combined with infusions of B6 NK cells activated with IL-15/IL-15Rα and CD137L ex vivo. Allogeneic HSCT alone was insufficient to control NXS2 tumor growth, but the addition of hu14.18-IL2 controlled tumor growth and improved survival. Adoptive transfer of ex vivo CD137L/IL-15/IL-15Rα activated NK cells with or without hu14.18-IL2 exacerbated lethality. CD137L/IL-15/IL-15Rα activated NK cells showed enhanced cytotoxicity and produced high levels of TNF-α in vitro, but induced cytokine release syndrome (CRS) in vivo. Infusing Perforin-/- CD137L/IL-15/IL-15Rα activated NK cells had no impact on GVT, whereas TNF-α-/- CD137L/IL-15/IL-15Rα activated NK cells improved GVT by decreasing peripheral effector cell subsets while preserving tumor-infiltrating lymphocytes. Depletion of Ly49H+ NK cells also improved GVT. Using allogeneic HSCT for NBL is a viable platform for immunocytokines and ex vivo activated NK cell infusions, but must be balanced with induction of CRS. Regulation of TNFα or activating NK subsets may be needed to improve GVT effects.

CXCR4 allows T cell acute lymphoblastic leukemia to escape from JAK1/2 and BCL2 inhibition through CNS infiltration

Targeting the JAK/STAT and BCL2 pathways in patients with relapsed/refractory T cell acute lymphoblastic leukemia (T-ALL) may provide an alternative approach to achieve clinical remissions. Ruxolitinib and venetoclax show a dose-dependent effect on T-ALL individually, but combination treatment reduces survival and proliferation of T-ALL in vitro. Using a xenograft model, the combination treatment fails to improve survival, with death from hind limb paralysis. Despite on-target inhibition by the drugs, histopathology demonstrates increased leukemic infiltration into the central nervous system (CNS) as compared to liver or bone marrow. Liquid chromatography-tandem mass spectroscopy shows that ruxolitinib and venetoclax insufficiently cross into the CNS. The addition of the CXCR4 inhibitor plerixafor with ruxolitinib and venetoclax reduces clinical scores and enhances survival. While combination therapy with ruxolitinib and venetoclax shows promise for treating T-ALL, additional inhibition of the CXCR4-CXCL12 axis may be needed to maximize the possibility of complete remission.

Development of AO-176, a Next-Generation Humanized Anti-CD47 Antibody with Novel Anticancer Properties and Negligible Red Blood Cell Binding

Inhibitors of adaptive immune checkpoints have shown promise as cancer treatments. CD47 is an innate immune checkpoint receptor broadly expressed on normal tissues and overexpressed on many tumors. Binding of tumor CD47 to signal regulatory protein alpha (SIRPα) on macrophages and dendritic cells triggers a "don't eat me" signal that inhibits phagocytosis enabling escape of innate immune surveillance. Blocking CD47/SIRPα interaction promotes phagocytosis reducing tumor burden in numerous xenograft and syngeneic animal models. We have developed a next-generation humanized anti-CD47 antibody, AO-176, that not only blocks the CD47/SIRPα interaction to induce tumor cell phagocytosis, but also induces tumor cytotoxicity in hematologic and solid human tumor cell lines, but not normal noncancerous cells, by a cell autonomous mechanism (not ADCC). AO-176 also binds preferentially to tumor versus many normal cell types. In particular, AO-176 binds negligibly to RBCs in contrast to tumor cells, even at high concentrations up to 200 μg/mL and does not agglutinate RBCs up to 1 mg/mL in vitro These properties are expected not only to decrease the antigen sink, but also to minimize on-target clinical adverse effects observed following treatment with other reported RBC-binding anti-CD47 antibodies. When tested in cynomolgus monkeys, AO-176 was well tolerated with no adverse effects. Finally, we show that AO-176 demonstrates dose-dependent antitumor activity in tumor xenograft models. Taken together, the unique properties and antitumor activity of our next-generation anti-CD47 antibody, AO-176, distinguishes it from other CD47/SIRPα axis targeting agents in clinical development.

Abstract 540: AO-176, a normal cell sparing humanized anti-CD47 antibody

AO-176 is a next generation humanized anti-CD47 IgG2 that binds human and cynomolgus monkey CD47 equivalently. AO-176, like other CD47 antibodies, blocks the interaction of CD47 with SIRPα, inducing phagocytosis of tumor cells by activated macrophages. Unique to AO-176 is its ability to directly kill tumor cells via programmed cell death type III and immunogenic cell death in a cell autonomous (non-ADCC) manner. AO-176 also exhibits preferential binding to tumor vs. normal cells, a notable characteristic, as CD47 is expressed on many normal cells including red blood cells (RBC), platelets, T cells and endothelial cells. While other CD47 antibodies induce hematological toxicities such as anemia and thrombocytopenia in both primate models and in patients, AO-176 negligibly binds RBCs and platelets and even at high doses, minimally impacts hematology in cynomolgus monkey toxicology studies. AO-176 is currently being evaluated in phase 1 clinical trials for the treatment of solid tumors.

In recent head to head experiments conducted with other CD47 antibodies, AO-176 bound all normal cells tested to a significantly lower degree. For example, unlike anti-CD47 antibodies such as Hu-5F9-G4, we observed negligible and minimal ex vivo binding to healthy human RBCs and platelets respectively and significantly lower binding of AO-176 to other hematologic and non-hematologic cells such as T cells and endothelial cells. Although AO-176 binds cynomolgus monkey RBCs to a slightly greater degree than human RBCs ex vivo, AO-176 versus comparative published Hu5F9-G4 findings has demonstrated dramatically reduced receptor occupancy when evaluated in monkey toxicology studies. We have also developed a clinic-ready receptor occupancy assay to measure AO-176 binding to circulating PBMCs in patients treated with AO-176 and to demonstrate minimal binding to CD47 on normal human cells.

We have begun to evaluate mechanisms that may underlie the normal cell sparing effects of AO-176. Published studies have demonstrated that in addition to CD47 protein expression level, clustering and mobility of CD47 at the cell surface may impact binding to ligands, downstream signaling and subsequent cellular responses such as apoptosis. For example, avidity for SIRPα and clearance by macrophages is modulated by CD47 clustering that can be modulated by protein glycosylation, association with lipid rafts, cytoskeleton, integrins or other cis-acting factors. Here, we compare the distribution of CD47 on tumor and RBCs to evaluate receptor association with other cellular membrane components that may impact distribution on the cell surface.

In summary, AO-176 is a next generation anti-CD47 antibody that, aside from induction of phagocytosis, possesses additional attributes that include direct tumor cell killing and preferential binding to tumor versus normal cells. These attributes of AO-176 differentiate it from other CD47 axis targeting agents currently in clinical evaluation.

Citation Format: Prabir Chakraborty, Myriam N. Bouchlaka, Benjamin J. Capoccia, Ronald R. Hiebsch, Michael J. Donio, Robyn J. Puro, Vicki Sung, Daniel S. Pereira. AO-176, a normal cell sparing humanized anti-CD47 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 540.

Abstract 548: Evaluation of novel SIRP antibodies as potential cancer therapeutics

Targeting immune checkpoints of adaptive immunity has shown great therapeutic efficacy in oncology, but in a limited fraction of patients. Innate immune cells represent the most abundant immune cell types in many solid tumors and are often linked to a poor prognosis.

SIRPα is expressed by innate immune cells and its interaction with CD47, expressed by most tumor cells, is an important immune checkpoint of the innate response, involved in the regulation of phagocytosis by macrophages, dendritic cells and neutrophils.

Recently, first generation agents targeting CD47 (CD47 antibodies and SIRPα-Fc fusion proteins) have shown promise in clinical trials, but they have also experienced hematological toxicities such as anemia or thrombocytopenia. Consequently, we have previously reported on the development of AO-176, a next generation anti-CD47 antibody that not only blocks the CD47/SIRPα interaction and induces phagocytosis, but also preferentially binds tumor versus normal cells (including RBCs where it binds negligibly) and directly kills tumor cells via a programmed cell death type III and an immunogenic cell death process.

Here we report the discovery of novel anti-SIRP antibodies that recognize either SIRPα selectively or SIRPα/γ. These antibodies are being evaluated for their ability to induce phagocytosis of tumor cells - we have identified antibodies that induce phagocytosis of tumor cells alone and in combination with Rituxan. The ability of our anti-SIRP antibodies to induce immunomodulatory activities in a variety of ex vivo cultured immune cells expressing either SIRPα or SIRPα/γ is also under investigation and will be presented.

Citation Format: Ronald R. Hiebsch, Myriam N. Bouchlaka, Benjamin J. Capoccia, Michael J. Donio, Prabir Chakraborty, W. Casey Wilson, Robyn J. Puro, Daniel S. Pereira. Evaluation of novel SIRP antibodies as potential cancer therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 548.

An Uncoupling of Canonical Phenotypic Markers and Functional Potency of Ex Vivo-Expanded Natural Killer Cells

Recent advances in cellular therapies for patients with cancer, including checkpoint blockade and ex vivo-expanded, tumor-specific T cells, have demonstrated that targeting the immune system is a powerful approach to the elimination of tumor cells. Clinical efforts have also demonstrated limitations, however, including the potential for tumor cell antigenic drift and neoantigen formation, which promote tumor escape and recurrence, as well as rapid onset of T cell exhaustion in vivo. These findings suggest that antigen unrestricted cells, such as natural killer (NK) cells, may be beneficial for use as an alternative to or in combination with T cell based approaches. Although highly effective in lysing transformed cells, to date, few clinical trials have demonstrated antitumor function or persistence of transferred NK cells. Several recent studies describe methods to expand NK cells for adoptive transfer, although the effects of ex vivo expansion are not fully understood. We therefore explored the impact of a clinically validated 12-day expansion protocol using a K562 cell line expressing membrane-bound IL-15 and 4-1BB ligand with high-dose soluble IL-2 on the phenotype and functions of NK cells from healthy donors. Following expansions using this protocol, we found expression of surface proteins that implicate preferential expansion of NK cells that are not fully mature, as is typically associated with highly cytotoxic NK cell subsets. Despite increased expression of markers associated with functional exhaustion in T cells, we found that ex vivo-expanded NK cells retained cytokine production capacity and had enhanced tumor cell cytotoxicity. The preferential expansion of an NK cell subset that is phenotypically immature and functionally pleiotropic suggests that adoptively transferred cells may persist better in vivo when compared with previous methods using this approach. Ex vivo expansion does not quell killer immunoglobulin-like receptor diversity, allowing responsiveness to various factors in vivo that may influence activation and inhibition. Collectively, our data suggest that in addition to robust NK cell expansion that has been described using this method, expanded NK cells may represent an ideal cell therapy that is longer lived, highly potent, and responsive to an array of activating and inhibitory signals.

Human MEMs are a distinct high IL-6 producing macrophage subset with anti-inflammatory and radioprotective properties in vivo

Macrophages (MØs) can polarize into subsets of “pro-inflammatory” (M1) MØs or “anti-inflammatory” (M2) MØs. Previously we described a unique population of MØs, termed human mesenchymal stem cell (MSC)-educated MØs (MEMs). In this study, we hypothesize that MEMs have potential to attenuate inflammation and promote tissue repair in vivo based on their immunophenotype and secretome. MEMs were generated by isolating monocytes from human peripheral blood and culturing them into MØs, followed by a co-culture with bone marrow-derived MSCs. RNA-Seq analysis showed genes associated with epithelial-mesenchymal transition, collagen formation, tissue development, and cell-cell adhesion were positively correlated with MEMs, while genes associated with oxidative phosphorylation were negatively correlated as compared to M1 MØs. We found increased expression of 8 genes implicated in wound healing, as well as genes representing remodeling enzymes, growth factors and the cytoskeleton. RT-PCR verified MEMs have increased CD206 (p<0.0001), IL-1β (p<0.001), TGFβ (p<0.001) and arginase-1 (p< 0.05), as well as increased IL-6 (p<0.0001) and CD73 (p<0.001) expression. MEMs produced over 4x greater amounts of IL-6 as compared to M2 MØs by ELISA (p<0.001), which could be enhanced with LPS stimulation (p<0.0001) or attenuated by inhibition of COX-2 (p<0.05), arginase-1 (p<0.01) or JAK1/JAK2 (p<0.05). In vivo, MEMs improved survival against lethal GVHD (p<0.01), in part by reducing T cell proliferation (p<0.001). MEMs also enhanced survival of mice from lethal radiation injury (p<0.01), in part by inducing host fibroblast proliferation (p<0.01). MEMs are a unique MØ subset with therapeutic potential for inflammatory disorders.

Human Mesenchymal Stem Cell-Educated Macrophages Are a Distinct High IL-6-Producing Subset that Confer Protection in Graft-versus-Host-Disease and Radiation Injury Models

Mesenchymal stem cells (MSCs) have immunosuppressive and tissue repair properties, but clinical trials using MSCs to prevent or treat graft-versus-host disease (GVHD) have shown mixed results. Macrophages (MØs) are important regulators of immunity and can promote tissue regeneration and remodeling. We have previously shown that MSCs can educate MØs toward a unique anti-inflammatory immunophenotype (MSC-educated MØs [MEMs]); however, their implications for in vivo models of inflammation have not been studied yet. We now show that in comparison with MØs, MEMs have increased expression of the inhibitory molecules PD-L1, PD-L2, in addition to markers of alternatively activated MØs: CD206 and CD163. RNA-Seq analysis of MEMs, as compared with MØs, show a distinct gene expression profile that positively correlates with multiple pathways important in tissue repair. MEMs also show increased expression of IL-6, transforming growth factor-β, arginase-1, CD73, and decreased expression of IL-12 and tumor necrosis factor-α. We show that IL-6 secretion is controlled in part by the cyclo-oxygenase-2, arginase, and JAK1/STAT1 pathway. When tested in vivo, we show that human MEMs significantly enhance survival from lethal GVHD and improve survival of mice from radiation injury. We show these effects could be mediated in part through suppression of human T cell proliferation and may have attenuated host tissue injury in part by enhancing murine fibroblast proliferation. MEMs are a unique MØ subset with therapeutic potential for the management of GVHD and/or protection from radiation-induced injury.

FBXO10 deficiency and BTK activation upregulate BCL2 expression in mantle cell lymphoma

Targeting Bruton tyrosine kinase (BTK) by ibrutinib is an effective treatment for patients with relapsed/refractory mantle cell lymphoma (MCL). However, both primary and acquired resistance to ibrutinib have developed in a significant number of these patients. A combinatory strategy targeting multiple oncogenic pathways is critical to enhance the efficacy of ibrutinib. Here, we focus on the BCL2 anti-apoptotic pathway. In a tissue microarray of 62 MCL samples, BCL2 expression positively correlated with BTK expression. Increased levels of BCL2 were shown to be due to a defect in protein degradation because of no or little expression of the E3 ubiquitin ligase FBXO10, as well as transcriptional upregulation through BTK-mediated canonical nuclear factor-κB activation. RNA-seq analysis confirmed that a set of anti-apoptotic genes (for example, BCL2, BCL-XL and DAD1) was downregulated by BTK short hairpin RNA. The downregulated genes also included those that are critical for B-cell growth and proliferation, such as BCL6, MYC, PIK3CA and BAFF-R. Targeting BCL2 by the specific inhibitor ABT-199 synergized with ibrutinib in inhibiting growth of both ibrutinib-sensitive and -resistant cancer cells in vitro and in vivo. These results suggest co-targeting of BTK and BCL2 as a new therapeutic strategy in MCL, especially for patients with primary resistance to ibrutinib.

(19)F-MRI for monitoring human NK cells in vivo

The availability of clinical-grade cytokines and artificial antigen-presenting cells has accelerated interest in using natural killer (NK) cells as adoptive cellular therapy (ACT) for cancer. One of the technological shortcomings of translating therapies from animal models to clinical application is the inability to effectively and non-invasively track these cells after infusion in patients. We have optimized the nonradioactive isotope fluorine-19 ((19)F) as a means to label and track NK cells in preclinical models using magnetic resonance imaging (MRI). Human NK cells were expanded with interleukin (IL)-2 and labeled in vitro with increasing concentrations of (19)F. Doses as low as 2 mg/mL (19)F were detected by MRI. NK cell viability was only decreased at 8 mg/mL (19)F. No effects on NK cell cytotoxicity against K562 leukemia cells were observed with 2, 4 or 8 mg/mL (19)F. Higher doses of (19)F, 4 mg/mL and 8 mg/mL, led to an improved (19)F signal by MRI with 3 × 10(11) (19)F atoms per NK cell. The 4 mg/mL (19)F labeling had no effect on NK cell function via secretion of granzyme B or interferon gamma (IFNγ), compared to NK cells exposed to vehicle alone. (19)F-labeled NK cells were detectable immediately by MRI after intratumoral injection in NSG mice and up to day 8. When (19)F-labeled NK cells were injected subcutaneously, we observed a loss of signal through time at the site of injection suggesting NK cell migration to distant organs. The (19)F perfluorocarbon is a safe and effective reagent for monitoring the persistence and trafficking of NK cell infusions in vivo, and may have potential for developing novel imaging techniques to monitor ACT for cancer.

Late administration of murine CTLA-4 blockade prolongs CD8-mediated anti-tumor effects following stimulatory cancer immunotherapy

We have demonstrated that immunostimulatory therapies such as interleukin-2 (IL-2) and anti-CD40 (αCD40) can be combined to deliver synergistic anti-tumor effects. While this strategy has shown success, efficacy varies depending on a number of factors including tumor type and severe toxicities can be seen. We sought to determine whether blockade of negative regulators such as cytotoxic T lymphocyte antigen-4 (CTLA-4) could simultaneously prolong CD8(+) T cell responses and augment T cell anti-tumor effects. We devised a regimen in which anti-CTLA-4 was administered late so as to delay contraction and minimize toxicities. This late administration both enhanced and prolonged CD8 T cell activation without the need for additional IL-2. The quality of the T cell response was improved with increased frequency of effector/effector memory phenotype cells along with improved lytic ability and bystander expansion. This enhanced CD8 response translated to improved anti-tumor responses both at the primary and metastatic sites. Importantly, toxicities were not exacerbated with combination. This study provides a platform for rational design of immunotherapy combinations to maximize anti-tumor immunity while minimizing toxicities.

Out-of-Sequence Signal 3 Paralyzes Primary CD4(+) T-Cell-Dependent Immunity

Primary T cell activation involves the integration of three distinct signals delivered in sequence: (1) antigen recognition, (2) costimulation, and (3) cytokine-mediated differentiation and expansion. Strong immunostimulatory events such as immunotherapy or infection induce profound cytokine release causing "bystander" T cell activation, thereby increasing the potential for autoreactivity and need for control. We show that during strong stimulation, a profound suppression of primary CD4(+) T-cell-mediated immune responses ensued and was observed across preclinical models and patients undergoing high-dose interleukin-2 (IL-2) therapy. This suppression targeted naive CD4(+) but not CD8(+) T cells and was mediated through transient suppressor of cytokine signaling-3 (SOCS3) inhibition of the STAT5b transcription factor signaling pathway. These events resulted in complete paralysis of primary CD4(+) T cell activation, affecting memory generation and induction of autoimmunity as well as impaired viral clearance. These data highlight the critical regulation of naive CD4(+) T cells during inflammatory conditions.

Adiposity induces lethal cytokine storm after systemic administration of stimulatory immunotherapy regimens in aged mice

William Murphy’s group at UC Davis previously found that systemic administration of stimulatory immunotherapy (IT) in aged mice resulted in the rapid induction of cytokine storm culminating in multi-organ pathology and rapid lethality. They now show that in addition to age, increased body fat is critical to this adverse reaction, as aged calorie-restricted mice demonstrate protection from IT-induced toxicity. In contrast, young obese mice succumb to cytokine storm, multi-organ pathology, and lethality after systemic IT administration.

Aging is a contributing factor in cancer occurrence. We recently demonstrated that systemic immunotherapy (IT) administration in aged, but not young, mice resulted in induction of rapid and lethal cytokine storm. We found that aging was accompanied by increases in visceral fat similar to that seen in young obese (ob/ob or diet-induced obese [DIO]) mice. Yet, the effects of aging and obesity on inflammatory responses to immunotherapeutics are not well defined. We determine the effects of adiposity on systemic IT tolerance in aged compared with young obese mice. Both young ob/ob- and DIO-generated proinflammatory cytokine levels and organ pathologies are comparable to those in aged ad libitum mice after IT, culminating in lethality. Young obese mice exhibited greater ratios of M1/M2 macrophages within the peritoneal and visceral adipose tissues and higher percentages of TNF⁺ macrophages in response to αCD40/IL-2 as compared with young lean mice. Macrophage depletion or TNF blockade in conjunction with αCD40/IL-2 prevented cytokine storms in young obese mice and protected from lethality. Calorie-restricted aged mice contain less visceral fat and displayed reduced cytokine levels, protection from organ pathology, and protection from lethality upon αCD40/IL-2 administration. Our data demonstrate that adiposity is a critical factor in the age-associated pathological responses to systemic anti-cancer IT.

Increased antitumor effects using IL-2 with anti-TGF-β reveals competition between mouse NK and CD8 T cells

Because of increasing interest in the removal of immunosuppressive pathways in cancer, the combination of IL-2 with Abs to neutralize TGF-β, a potent immunosuppressive cytokine, was assessed. Combination immunotherapy resulted in significantly greater antitumor effects. These were correlated with significant increases in the numbers and functionality of NK cells, NK cell progenitors, and activated CD8 T cells, resulting in the observed antitumor effects. Combination immunotherapy also was accompanied by lesser toxicities than was IL-2 therapy alone. Additionally, we observed a dual competition between NK cells and activated CD8 T cells such that, after immunotherapy, the depletion of either effector population resulted in the increased total expansion of the other population and compensatory antitumor effects. This study demonstrates the efficacy of this combination immunotherapeutic regimen as a promising cancer therapy and illustrates the existence of potent competitive regulatory pathways between NK cells and CD8 T cells in response to systemic activation.

Impact of aging in cancer immunotherapy: The importance of using accurate preclinical models

Cancer immunotherapy holds great promise, yet its efficacy and applicability can be hampered by the rise of systemic toxicities. We have recently shown that the lethal side effects of cancer immunotherapy are markedly exacerbated with aging. Blocking tumor necrosis factor α or macrophages can alleviate the systemic toxicity of immunotherapy while preserving its antineoplastic effects.

Aging predisposes to acute inflammatory induced pathology after tumor immunotherapy

Aging strongly promotes inflammation responses, which may predispose individuals after cancer therapies to lethal system toxicities and pathology that can be partially prevented by TNF blockade.

Cancer commonly occurs in the elderly and immunotherapy (IT) is being increasingly applied to this population. However, the majority of preclinical mouse tumor models assessing potential efficacy and toxicities of therapeutics use young mice. We assessed the impact of age on responses to systemic immune stimulation. In contrast to young mice, systemic cancer IT regimens or LPS given to aged mice resulted in rapid and lethal toxicities affecting multiple organs correlating with heightened proinflammatory cytokines systemically and within the parenchymal tissues. This inflammatory response and increased morbidity with age was independent of T cells or NK cells. However, prior in vivo depletion of macrophages in aged mice resulted in lesser cytokine levels, increased survival, and decreased liver histopathology. Furthermore, macrophages from aged mice and normal human elderly volunteers displayed heightened TNF and IL-6 production upon in vitro stimulation. Treatment of both TNF knockout mice and in vivo TNF blockade in aged mice resulted in significant increases in survival and lessened pathology. Importantly, TNF blockade in tumor-bearing, aged mice receiving IT displayed significant anti-tumor effects. These data demonstrate the critical role of macrophages in the age-associated hyper-inflammatory cytokine responses to systemic immunostimulation and underscore the importance of performing preclinical assessments in aged mice.

Mechanical disruption of tumors by iron particles and magnetic field application results in increased anti-tumor immune responses

The primary tumor represents a potential source of antigens for priming immune responses for disseminated disease. Current means of debulking tumors involves the use of cytoreductive conditioning that impairs immune cells or removal by surgery. We hypothesized that activation of the immune system could occur through the localized release of tumor antigens and induction of tumor death due to physical disruption of tumor architecture and destruction of the primary tumor in situ. This was accomplished by intratumor injection of magneto-rheological fluid (MRF) consisting of iron microparticles, in Balb/c mice bearing orthotopic 4T1 breast cancer, followed by local application of a magnetic field resulting in immediate coalescence of the particles, tumor cell death, slower growth of primary tumors as well as decreased tumor progression in distant sites and metastatic spread. This treatment was associated with increased activation of DCs in the draining lymph nodes and recruitment of both DCs and CD8(+)T cells to the tumor. The particles remained within the tumor and no toxicities were observed. The immune induction observed was significantly greater compared to cryoablation. Further anti-tumor effects were observed when MRF/magnet therapy was combined with systemic low dose immunotherapy. Thus, mechanical disruption of the primary tumor with MRF/magnetic field application represents a novel means to induce systemic immune activation in cancer.

Immunotherapy following hematopoietic stem cell transplantation: potential for synergistic effects

Hematopoietic stem cell transplantation (HSCT) is a particularly important treatment for hematologic malignancies. Unfortunately, following allogeneic HSCT, graft-versus-host disease, immunosuppression and susceptibility to opportunistic infections remain among the most substantial problems restricting the efficacy and use of this procedure, particularly for cancer. Adoptive immunotherapy and/or manipulation of the graft offer ways to attack residual cancer as well as other transplant-related complications. Recent exciting discoveries have demonstrated that HSCT could be expanded to solid tissue cancers with profound effects on the effectiveness of adoptive immunotherapy. This review will provide a background regarding HSCT, discuss the complications that make it such a complex treatment procedure following up with current immunotherapeutic strategies and discuss emerging approaches in applying immunotherapy in HSCT for cancer.