Preclinical Murine Studies Research Articles

Elimination of Human Papillomavirus 16-Positive Tumors by a Mucosal rAd5 Therapeutic Vaccination in a Pre-Clinical Murine Study.

Therapeutic vaccination can harness the body's cellular immune system to target and destroy cancerous cells. Several treatment options are available to eliminate pre-cancerous and cancerous lesions caused by human papillomaviruses (HPV), but may not result in a long-term cure. Therapeutic vaccination may offer an effective, durable, and minimally intrusive alternative. We developed mucosally delivered, recombinant, non-replicating human adenovirus type 5 (rAd5)-vectored vaccines that encode HPV16's oncogenic proteins E6 and E7 alongside a molecular dsRNA adjuvant. The induction of antigen-specific T cells and the therapeutic efficacy of rAd5 were evaluated in a mouse model of HPV tumorigenesis where E6E7-transformed cells, TC-1, were implanted subcutaneously in C57BL/6 mice. After tumor growth, mice were treated intranasally with rAd5 vaccines expressing the wildtype form of E6E7 (rAd5-16/E6E7Wt) in combination with an anti-PD-1 antibody or isotype control. Animals treated with rAd5-16/E6E7Wt with and without anti-PD-1 had significant reductions in tumor volume and increased survival compared to controls. Further, animals treated with rAd5-16/E6E7Wt had increased CD4+ and CD8+ tumor-infiltrating lymphocytes (TILs) and produced a cytotoxic tumor microenvironment. In a second study, the immunogenicity of a non-transformative form of E6E7 (rAd5-16/E6E7Mu) and a vaccine encoding predicted T cell epitopes of E6E7 (rAd5-16/E6E7epi) were evaluated. These vaccines elicited significant reductions in TC-1 tumor volume and increased survival of animals. Antigen-specific CD8+ T effector memory cells were observed in the animals treated with E6E7-encoding rAd5, but not in the rAd5-empty group. The work described here demonstrates that this mucosal vaccination can be used therapeutically to elicit specific cellular immunity and further identifies a clinical candidate with great potential for the treatment and prevention of human cervical cancer.

The Role of Biological Sex in Pre-Clinical (Mouse) mRNA Vaccine Studies.

In this study, we consider the influence of biological sex-specific immune responses on the assessment of mRNA vaccines in pre-clinical murine studies. Recognising the established disparities in immune function attributed to genetic and hormonal differences between individuals of different biological sexes, we compared the mRNA expression and immune responses in mice of both biological sexes after intramuscular injection with mRNA incorporated within lipid nanoparticles. Regarding mRNA expression, no significant difference in protein (luciferase) expression at the injection site was observed between female and male mice following intramuscular administration; however, we found that female BALB/c mice exhibit significantly greater total IgG responses across the concentration range of mRNA lipid nanoparticles (LNPs) in comparison to their male counterparts. This study not only contributes to the scientific understanding of mRNA vaccine evaluation but also emphasizes the importance of considering biological sex in vaccine study designs during pre-clinical evaluation in murine studies.

Trial in Progress: An Open-Label, Multi-Center Phase 2 Study to Assess the Safety and Efficacy of Burixafor (GPC-100) and Propranolol with and without G-CSF for the Mobilization of Stem Cells in Patients with Multiple Myeloma Undergoing Autologous Stem Cell Transplant

Background and Significance: Poor stem cell mobilization with failure to produce the target cell dose of ≥2x10 6 CD34 cells/kg required for autologous stem cell transplant (ASCT) occurs in 15-50% of patients with lymphoma or multiple myeloma (MM). Newer therapies may also have a negative impact on mobilization, supporting a need for newer treatment options. Burixafor (GPC-100) is a potent and selective small molecule antagonist of CXCR4. Previous clinical trials with burixafor alone or in combination with G-CSF have demonstrated safe and effective mobilization of stem cells. Preclinical murine studies demonstrated that burixafor in combination with propranolol is a potent mobilizer of white blood cells and mouse stem cells, and mobilization was further augmented with the addition of G-CSF. The goal of the current clinical study is to evaluate the efficacy of burixafor and propranolol in the presence and absence of G-CSF. The triple combination is predicted to be best in class and can target patients at risk for poor mobilization while burixafor plus propranolol will allow for an option when G-CSF is not tolerated, such as in sickle cell disease or patients with autoimmune disease. Study Design and Methods: This study (NCT05561751) is an open-label, randomized, multi-site (U.S. only) Phase 2 trial. Approximately 40 participants will be enrolled across 8-10 sites and randomized in a 1:1 ratio to one of two treatment arms: Burixafor in combination with propranolol or burixafor in combination with propranolol and G-CSF. The study will employ a Bayesian Optimal Phase 2 (BOP2) design for participant enrollment to characterize the safety and clinical activity of burixafor. Participants must be at least 18 years of age, be diagnosed with MM and be eligible for ASCT. Key exclusion criteria include: no more than one year of therapy administered prior to stem cell mobilization, previous stem cell transplant, history of another malignancy, and history of poorly controlled or uncontrolled cardiovascular or pulmonary disease. All participants will self-administer 30 mg propranolol orally twice daily from Days 1 to 8. For participants in the treatment arm receiving G-CSF, they will receive SC injections of 10g/kg/day G-CSF in the afternoon on Days 3 to 7. On days 7 and 8, participants will receive 3.14 mg/kg dose of burixafor via IV and undergo leukapheresis for stem cell collection two hours post drug administration. Participants may undergo additional optional days of the treatment regimen and stem cell collection, per Investigator's discretion to meet institutional standards. The primary objective is to determine the proportion of patients that will achieve at least ≥2 x 10 6 CD34 + cells/kg in 2 leukapheresis sessions following the treatment regimens. Key secondary objectives include: assessment of safety and tolerability of GPC-100 and propranolol with and without G-CSF, evaluation of the pharmacodynamics by determining levels of circulating CD34 + cell counts and levels of the chemokine CXCL12 in peripheral blood, and assessment of mean time to ANC and platelet count recovery after ASCT. Exploratory objectives are also included to discover key biomarkers for patient selection, to evaluate cancer/stem/immune cell profiles, and to evaluate treatment impact on patient quality of life.

Potential effects of anticoagulants in preclinicalmice modelsof oral cancer: A systematic review.

Oral squamous cell carcinoma (OSCC) is the most common head and neck cancer. There is mounting evidence to suggest that several components of the coagulation system directly affect carcinogenesis. Our recent in vitro studies demonstrated, for the first time, that various anticoagulants have anticancer effects on OSCC. They also showed the need for the immediate translation of these experimental conditions from bench to preclinical animal models. Here, we carried out a systematic review to summarise existing evidence on murine models built around the interactions between anticoagulants and oral cancer. Only one preclinical murine study was included in our systematic review, investigating the role of heparins in tumour pathophysiology. The paucity of evidence regarding the interactions between oral squamous cell carcinoma and anticoagulants emphasises the urgency with which further preclinical research should be conducted.

Magnetic field therapy enhances muscle mitochondrial bioenergetics and attenuates systemic ceramide levels following ACL reconstruction: Southeast Asian randomized-controlled pilot trial.

BackgroundMetabolic disruption commonly follows Anterior Cruciate Ligament Reconstruction (ACLR) surgery. Brief exposure to low amplitude and frequency pulsed electromagnetic fields (PEMFs) has been shown to promote in vitro and in vivo murine myogeneses via the activation of a calcium–mitochondrial axis conferring systemic metabolic adaptations. This randomized-controlled pilot trial sought to detect local changes in muscle structure and function using MRI, and systemic changes in metabolism using plasma biomarker analyses resulting from ACLR, with or without accompanying PEMF therapy.Methods20 patients requiring ACLR were randomized into two groups either undergoing PEMF or sham exposure for 16 weeks following surgery. The operated thighs of 10 patients were exposed weekly to PEMFs (1 ​mT for 10 ​min) for 4 months following surgery. Another 10 patients were subjected to sham exposure and served as controls to allow assessment of the metabolic repercussions of ACLR and PEMF therapy. Blood samples were collected prior to surgery and at 16 weeks for plasma analyses. Magnetic resonance data were acquired at 1 and 16 weeks post-surgery using a Siemens 3T Tim Trio system. Phosphorus (31P) Magnetic Resonance Spectroscopy (MRS) was utilized to monitor changes in high-energy phosphate metabolism (inorganic phosphate (Pi), adenosine triphosphate (ATP) and phosphocreatine (PCr)) as well as markers of membrane synthesis and breakdown (phosphomonoesters (PME) and phosphodiester (PDE)). Quantitative Magnetization Transfer (qMT) imaging was used to elucidate changes in the underlying tissue structure, with T1-weighted and 2-point Dixon imaging used to calculate muscle volumes and muscle fat content.ResultsImprovements in markers of high-energy phosphate metabolism including reductions in ΔPi/ATP, Pi/PCr and (Pi ​+ ​PCr)/ATP, and membrane kinetics, including reductions in PDE/ATP were detected in the PEMF-treated cohort relative to the control cohort at study termination. These were associated with reductions in the plasma levels of certain ceramides and lysophosphatidylcholine species. The plasma levels of biomarkers predictive of muscle regeneration and degeneration, including osteopontin and TNNT1, respectively, were improved, whilst changes in follistatin failed to achieve statistical significance. Liquid chromatography with tandem mass spectrometry revealed reductions in small molecule biomarkers of metabolic disruption, including cysteine, homocysteine, and methionine in the PEMF-treated cohort relative to the control cohort at study termination. Differences in measurements of force, muscle and fat volumes did not achieve statistical significance between the cohorts after 16 weeks post-ACLR.ConclusionThe detected changes suggest improvements in systemic metabolism in the post-surgical PEMF-treated cohort that accords with previous preclinical murine studies. PEMF-based therapies may potentially serve as a manner to ameliorate post-surgery metabolic disruptions and warrant future examination in more adequately powered clinical trials.The Translational Potential of this ArticleSome degree of physical immobilisation must inevitably follow orthopaedic surgical intervention. The clinical paradox of such a scenario is that the regenerative potential of the muscle mitochondrial pool is silenced. The unmet need was hence a manner to maintain mitochondrial activation when movement is restricted and without producing potentially damaging mechanical stress. PEMF-based therapies may satisfy the requirement of non-invasively activating the requisite mitochondrial respiration when mobility is restricted for improved metabolic and regenerative recovery.

Abstract 3152: IFN-gamma stimulated cryopreserved mesenchymal stromal cells for treatment of radiation induced xerostomia

Abstract Purpose/Objectives: There is a critical need for a treatment that will safely and effectively alleviate radiation-induced xerostomia (RIX). Head and neck radiation results in hyposalivation and altered sialochemistry which patients experience as xerostomia. We performed a preclinical and a pilot clinical study to determine if IFN-ɣ stimulated marrow-derived mesenchymal stromal cells (MSC(M)) from HNC patients could function as a source of autologous cells for the treatment of RIX and as a tool in preclinical murine studies of RIX. Materials/Methods: Bone marrow aspirates from HNC patients previously treated with chemoradiation were obtained (IRB #2019-0497, NCT 04007081). MSC(M)s were isolated from bone marrow. MSC(M) were expanded in culture, surface marker expression was confirmed via flow cytometry, stimulated with IFN-ɣ, and cryopreserved. Thawed MSC(M)s were profiled to evaluate their functionality after cryorecovery. Cells were tested for their ability to stimulate salivary production in a murine model of RIX by injecting 1x106 cells into the submandibular gland (SMG) one week after a single 15 Gy fraction of radiation. Efficacy was evaluated by saliva production and histology. Results: MSC(M)s from six patients were expanded to >20x106 cells (median 15.5, range of 8-20 days). Post-thaw cultures demonstrated robust growth, with a median doubling time of 3.1 days. Cultured cells showed an MSC(M) phenotype, positive for CD73, CD90, and CD105 and negative for CD14, CD20, CD34, or CD45. IFN-ɣ stimulated MSC(M)s had immunomodulatory potential based on increased expression of IDO, ICAM-1, PD-L1, MHC I and MHC II expression compared with non-stimulated MSC(M)s (391%, 263%, 114%, 70% and 196% percent increase respectively). In a murine model of RIX, radiation resulted in structural changes to the gland as evidenced by increased fibrosis, decreased acinar size, and immune cell infiltration. Injection of MSC(M)s to the SMG following radiation resulted in improved saliva production, a reduction in fibrosis, and an increase in the size and density of acini within the tissue compared to control. Conclusions: These data strongly support the feasibility of a first-in-human clinical trial of autologous IFN-ɣ stimulated MSC(M)s to treat RIX and the potential of using human-derived MSC(M)s in future murine studies of RIX. Citation Format: Cristina Paz, Grace Blitzer, Annemarie Glassey, Kwangok P. Nickel, Jayeeta Giri, Andrea Pennati, Daniel Robbins, Tadeas Lunga, Susan Thibeault, Jacques Galipeau, Randall Kimple. IFN-gamma stimulated cryopreserved mesenchymal stromal cells for treatment of radiation induced xerostomia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3152.

The Vascular-Dependent and -Independent Actions of Calcitonin Gene-Related Peptide in Cardiovascular Disease.

The treatment of hypertension and heart failure remains a major challenge to healthcare providers. Despite therapeutic advances, heart failure affects more than 26 million people worldwide and is increasing in prevalence due to an ageing population. Similarly, despite an improvement in blood pressure management, largely due to pharmacological interventions, hypertension remains a silent killer. This is in part due to its ability to contribute to heart failure. Development of novel therapies will likely be at the forefront of future cardiovascular studies to address these unmet needs. Calcitonin gene-related peptide (CGRP) is a 37 amino acid potent vasodilator with positive-ionotropic and -chronotropic effects. It has been reported to have beneficial effects in hypertensive and heart failure patients. Interestingly, changes in plasma CGRP concentration in patients after myocardial infarction, heart failure, and in some forms of hypertension, also support a role for CGRP on hemodynamic functions. Rodent studies have played an important role thus far in delineating mechanisms involved in CGRP-induced cardioprotection. However, due to the short plasma half-life of CGRP, these well documented beneficial effects have often proven to be acute and transient. Recent development of longer lasting CGRP agonists may therefore offer a practical solution to investigating CGRP further in cardiovascular disease in vivo. Furthermore, pre-clinical murine studies have hinted at the prospect of cardioprotective mechanisms of CGRP which is independent of its hypotensive effect. Here, we discuss past and present evidence of vascular-dependent and -independent processes by which CGRP could protect the vasculature and myocardium against cardiovascular dysfunction.

Discordance in STING-Induced Activation and Cell Death Between Mouse and Human Dendritic Cell Populations.

Stimulator of Interferon Genes (STING) is a cytosolic sensor of cyclic dinucleotides (CDNs). The activation of dendritic cells (DC) via the STING pathway, and their subsequent production of type I interferon (IFN) is considered central to eradicating tumours in mouse models. However, this contribution of STING in preclinical murine studies has not translated into positive outcomes of STING agonists in phase I & II clinical trials. We therefore questioned whether a difference in human DC responses could be critical to the lack of STING agonist efficacy in human settings. This study sought to directly compare mouse and human plasmacytoid DCs and conventional DC subset responses upon STING activation. We found all mouse and human DC subsets were potently activated by STING stimulation. As expected, Type I IFNs were produced by both mouse and human plasmacytoid DCs. However, mouse and human plasmacytoid and conventional DCs all produced type III IFNs (i.e., IFN-λs) in response to STING activation. Of particular interest, all human DCs produced large amounts of IFN-λ1, not expressed in the mouse genome. Furthermore, we also found differential cell death responses upon STING activation, observing rapid ablation of mouse, but not human, plasmacytoid DCs. STING-induced cell death in murine plasmacytoid DCs occurred in a cell-intrinsic manner and involved intrinsic apoptosis. These data highlight discordance between STING IFN and cell death responses in mouse and human DCs and caution against extrapolating STING-mediated events in mouse models to equivalent human outcomes.

Dasatinib does not exacerbate dexamethasone-induced osteonecrosis in murine models of acute lymphoblastic leukemia therapy.

There are clinical reports that the incorporation of dasatinib may increase the frequency of osteonecrosis in acute lymphoblastic leukemia (ALL) treatment regimens. No rigorous testing of this hypothesis is available to guide clinicians. We tested whether oral dasatinib increased the frequency of dexamethasone-induced osteonecrosis in a murine model and tested its effects on dexamethasone's antileukemic efficacy in a murine BCR-ABL+ model of ALL. Dasatinib did not change the frequency of osteonecrosis (p=.99) nor of arteriopathy (p=.36) in dexamethasone-treated mice when given at dosages that achieved clinically relevant steady-state dasatinib plasma concentrations of 53.1ng/ml (95% CI: 43.5-57.3ng/ml). These dasatinib exposures were not associated with increased dexamethasone plasma exposure in nonleukemia-bearing mice. These same dosages were not associated with any decrement in antileukemic efficacy of dexamethasone in a responsive BCR-ABL+ model of ALL. Based on the results of our preclinical murine studies, we conclude that dasatinib is unlikely to increase the osteonecrotic effects of dexamethasone in ALL regimens.

Hybrid derivative of cathelicidin and human beta defensin-2 against Gram-positive bacteria: A novel approach for the treatment of bacterial keratitis

Bacterial keratitis (BK) is a major cause of corneal blindness globally. This study aimed to develop a novel class of antimicrobial therapy, based on human-derived hybrid host defense peptides (HyHDPs), for treating BK. HyHDPs were rationally designed through combination of functional amino acids in parent HDPs, including LL-37 and human beta-defensin (HBD)-1 to -3. Minimal inhibitory concentrations (MICs) and time-kill kinetics assay were performed to determine the concentration- and time-dependent antimicrobial activity and cytotoxicity was evaluated against human corneal epithelial cells and erythrocytes. In vivo safety and efficacy of the most promising peptide was examined in the corneal wound healing and Staphylococcus aureus (ATCC SA29213) keratitis murine models, respectively. A second-generation HyHDP (CaD23), based on rational hybridization of the middle residues of LL-37 and C-terminal of HBD-2, was developed and was shown to demonstrate good efficacy against methicillin-sensitive and methicillin-resistant S. aureus [MIC = 12.5–25.0 μg/ml (5.2–10.4 μM)] and S. epidermidis [MIC = 12.5 μg/ml (5.2 μM)], and moderate efficacy against P. aeruginosa [MIC = 25-50 μg/ml (10.4–20.8 μM)]. CaD23 (at 25 μg/ml or 2× MIC) killed all the bacteria within 30 min, which was 8 times faster than amikacin (25 μg/ml or 20× MIC). After 10 consecutive passages, S. aureus (ATCC SA29213) did not develop any antimicrobial resistance (AMR) against CaD23 whereas it developed significant AMR (i.e. a 32-fold increase in MIC) against amikacin, a commonly used treatment for BK. Pre-clinical murine studies showed that CaD23 (0.5 mg/ml) achieved a median reduction of S. aureus bioburden by 94% (or 1.2 log10 CFU/ml) while not impeding corneal epithelial wound healing. In conclusion, rational hybridization of human-derived HDPs has led to generation of a potentially efficacious and safe topical antimicrobial agent for treating Gram-positive BK, with no/minimal risk of developing AMR.

Development of immunosuppressive myeloid cells to induce tolerance in solid organ and hematopoietic cell transplant recipients

AbstractReplacement of failed organs followed by safe withdrawal of immunosuppressive drugs has long been the goal of organ transplantation. We studied changes in the balance of T cells and myeloid cells in the blood of HLA-matched and -mismatched patients given living donor kidney transplants followed by total lymphoid irradiation, anti-thymocyte globulin conditioning, and donor hematopoietic cell transplant to induce mixed chimerism and immune tolerance. The clinical trials were based on a conditioning regimen used to establish mixed chimerism and tolerance in mice. In preclinical murine studies, there was a profound depletion of T cells and an increase in immunosuppressive polymorphonuclear (pmn) myeloid-derived suppressor cells (MDSCs) in the spleen and blood following transplant. Selective depletion of pmn MDSCs in mice abrogated mixed chimerism and tolerance. In our clinical trials, patients given an analogous tolerance conditioning regimen developed similar changes, including profound depletion of T cells and a marked increase in MDSCs in blood posttransplant. Posttransplant pmn MDSCs transiently increased expression of lectin-type oxidized LDL receptor-1, a marker of immunosuppression, and production of the T-cell inhibitor arginase-1. These posttransplant pmn MDSCs suppressed the activation, proliferation, and inflammatory cytokine secretion of autologous T-cell receptor microbead-stimulated pretransplant T cells when cocultured in vitro. In conclusion, we elucidated changes in receptors and function of immunosuppressive myeloid cells in patients enrolled in the tolerance protocol that were nearly identical to those of MDSCs required for tolerance in mice. These trials were registered at www.clinicaltrials.gov as #NCT00319657 and #NCT01165762.

Re-Evaluating the Effects of Obesity on Cancer Immunotherapy Outcomes in Renal Cancer: What Do We Really Know?

Obesity has reached global epidemic proportions and its effects on interactions between the immune system and malignancies, particularly as related to cancer immunotherapy outcomes, have come under increasing scrutiny. Although the vast majority of pre-clinical murine studies suggest that host obesity should have detrimental effects on anti-tumor immunity and cancer immunotherapy outcomes, the opposite has been found in multiple retrospective human studies. As a result, acceptance of the “obesity paradox” paradigm, wherein obesity increases cancer risk but then improves patient outcomes, has become widespread. However, results to the contrary do exist and the biological mechanisms that promote beneficial obesity-associated outcomes remain unclear. Here, we highlight discrepancies in the literature regarding the obesity paradox for cancer immunotherapy outcomes, with a particular focus on renal cancer. We also discuss multiple factors that may impact research findings and warrant renewed research attention in future studies. We propose that specific cancer patient populations may be affected in fundamentally different ways by host obesity, leading to divergent effects on anti-tumor immunity and/or immunotherapy outcomes. Continued, thoughtful analysis of this critical issue is therefore needed to permit a more nuanced understanding of the complex effects of host obesity on cancer immunotherapy outcomes in patients with renal cancer or other malignancies.

Terminating Cancer by Blocking VISTA as a Novel Immunotherapy: Hasta la vista, baby.

VISTA is an up-and-coming immune checkpoint molecule that can become the target of new cancer immunotherapy treatments. Immune cells in the tumor microenvironment can largely influence the progression of cancer through inhibitory and stimulatory pathways. Indeed, VISTA is expressed on many immune cells, including T cells, myeloid-derived suppressor cells, tumor-associated macrophages, and dendritic cells. VISTA has predominantly been shown to act in an immune-suppressing manner that enables cancer progression. This review will delve into results from preclinical murine studies of anti-VISTA monoclonal antibody treatments, bring together recent studies that detect VISTA expression on immune cells from patient tumors of various cancers, and discuss ongoing clinical trials involving VISTA.

Mouse Preclinical Cancer Immunotherapy Modeling Involving Anti-PD-1 Therapies Reveals the Need to Use Mouse Reagents to Mirror Clinical Paradigms.

Simple SummaryImmune checkpoint inhibition has revolutionized clinical cancer care. As clinical use of these inhibitors increases, the ability to study the effects of these therapies in preclinical models becomes more important. This study highlights the need for using species appropriate reagents to properly evaluate the efficacy and toxicity of cancer immunotherapy in mouse models.Immune checkpoint inhibition (ICI) has emerged as one of the most powerful tools to reverse cancer induced immune suppression. Monoclonal antibodies (mAbs) targeting programmed cell death 1/programmed cell death ligand 1(PD-1/PD-L1) are FDA-approved and their clinical use is rapidly expanding. As opposed to the clinical paradigm, which can result in significant responses and toxicities, it has been difficult to reproduce these effects preclinically using mouse models. In large part, this is due to models, which employ rapidly growing ex vivo cultured transplantable tumor cell lines engrafted into young naïve inbred laboratory mice. However, another issue concerns the use and repeated application of xenogeneic reagents in mice (i.e., rat or hamster mAbs directed against mouse antigens at variance with clinical use of human or humanized mAbs). Building on our previous studies demonstrating that repeated administration of commonly used xenogeneic anti-PD-1 mAbs derived from both rat and hamster can induce fatal hypersensitivity in some tumor-bearing mice, we sought to compare these result with the effects of a mouse anti-mouse PD-1 mAb. Application of a murine anti-mouse PD-1 (clone: MuDX400) did not result in lethal anaphylaxis in the 4T1 tumor model. It also displayed superior antitumor effects in this and other tumor models, as it did not induce neutralizing antibody responses against the anti-PD-1 mAb, such as were observed when using xenogeneic anti-PD1 mAbs. These results demonstrate that more accurate preclinical modeling necessitates the use of mouse reagents mirroring the clinical scenario to ascertain long-term effects or toxicities, while avoiding xenogeneic responses, which do not occur clinically. Furthermore, these studies suggest a direct mechanism, whereby preclinical murine studies have often failed to recapitulate the clinical efficacy and toxicity of single agent checkpoint inhibition.

Abstract A71: Resistance mechanisms limiting the immunostimulatory and antitumor activity of anti-CSF-1 receptor-mediated macrophage depletion

Abstract Tumor-associated macrophages (TAMs) are present within the stroma of most solid tumors where they contribute to disease progression through production of tumor and angiogenic growth factors, extracellular matrix remodeling, and suppression of immune responses. As such, depletion of tumor-associated macrophages, for instance through the use of blocking antibodies against the CSF-1 receptor (CSF1R), has been widely explored as a therapeutic approach to both inhibit tumor growth/metastasis and stimulate antitumor immune responses. In the context of immunotherapy, multiple preclinical murine studies have demonstrated that anti-CSF1R meditated macrophage depletion can promote antitumor T-cell responses, synergizing with immune checkpoint inhibitor therapy, such as PD1 blockade, and leading to tumor regression. However, some tumor models appear resistant to these beneficial effects of CSF1R blockade. In order to define potential mechanisms of resistance to CSF1R inhibitors, we evaluated the effects of anti-CSF1R treatment in mice bearing subcutaneous Renca renal cell adenocarcinoma tumors. Despite robust macrophage depletion, this model shows only a modest decrease in tumor volume and minimal effector T-cell recruitment or activation in response to anti-CSF1R therapy. Comprehensive flow cytometry-based immunophenotyping and single-cell RNA sequencing on immune cells isolated from anti-CSF1R- and isotype control-treated Renca tumors revealed shifts in gene expression patterns related to vascular remodeling, hypoxic responses, and enhanced regulatory T-cell activity. These studies indicate macrophage depletion may, under some conditions, have negative effects on antitumor immune responses that could limit the clinical benefit of this therapeutic approach. Citation Format: Katarzyna M. Skrzypczynska, Sarah A. O'Brien, Brian Belmontes, Hong Tan, Jessica Orf, Daniel Lu, Ian Driver, Jackson G. Egen. Resistance mechanisms limiting the immunostimulatory and antitumor activity of anti-CSF-1 receptor-mediated macrophage depletion [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A71.

Antibody blockade of semaphorin 4D to sensitize pancreatic cancer to immune checkpoint blockade.

26 Background: Pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis, and will soon become the second leading cause of cancer mortality. Unfortunately, T-cell directed immunotherapies have failed to demonstrate efficacy in PDAC. These failures may in part be mediated by an immunosuppressive tumor microenvironment (TME). Semaphorin 4D (Sema4D) is a glycoprotein which binds its cognate receptors Plexin B1/B2. Here we present our work in blocking Sema4D in a murine model of PDAC. Methods: C57b/6 mice were orthotopically injected with PDAC line (KP2) derived from KRASG12D,TP53Flox/Wt;P48-Cre autochthonous tumors and confirmed for disease by ultrasound. Mice were treated with FOLFIRINOX (5-FU, Irinotecan, Oxaliplatin, weekly), immune checkpoint blockade (ICB) (anti-PD1, anti-CTLA-4 mAbs bi-weekly), and anti-Sema4D mAB (bi-weekly). Human and mouse circulating and tumor infiltrating leukocytes were interrogated through flow cytometry (FACS) for immune subset and expression of Sema4D and Plexin receptors. Archived human PDAC tissues were assessed through quantitative immunohistochemistry (IHC) for presence of Sema4D positive infiltrate. Results: Both FACS and IHC analysis of human PDAC specimens confirm the presence and increased prevalence over normal pancreata of Sema4D lymphocytes and Plexin B1/B2 expressing tumor associated macrophages (TAMs). KP2 orthotopically injected mice exhibited longer survival when treated with the triple combination of FOLFIRINOX, ICB, and anti-Sema4D antibody, compared to FOLFIRINOX alone, FOLFIRINOX plus ICB, or FOLFIRINOX plus anti-Sema4D antibody (P < 0.02). Flow cytometric analysis of anti-Sema4D and ICB treated murine tumors show a doubling of penetration by CD 8+ effector T cells within tumors compared to control groups (P = 0.03). A loss in Sema4D fluorescence signal via FACS in tumor-infiltrating CD3+ leukocytes was observed in mice treated with anti-SEMA4D, confirming penetration and target blockade within the TME. Conclusions: Sema4D and Plexin B1/B2 leukocytes penetrate human PDAC tumors, and treatment with Sema4D blocking antibody improved response to ICB in combination with standard of care FOLFIRINOX in preclinical murine studies.

A toolbox for the longitudinal assessment of healthspan in aging mice.

The number of people aged over 65 is expected to double in the next 30 years. For many, living longer will mean spending more years with the burdens of chronic diseases such as Alzheimer's disease, cardiovascular disease, and diabetes. Although researchers have made rapid progress in developing geroprotective interventions that target mechanisms of aging and delay or prevent the onset of multiple concurrent age-related diseases, a lack of standardized techniques to assess healthspan in preclinical murine studies has resulted in reduced reproducibility and slow progress. To overcome this, major centers in Europe and the United States skilled in healthspan analysis came together to agree on a toolbox of techniques that can be used to consistently assess the healthspan of mice. Here, we describe the agreed toolbox, which contains protocols for echocardiography, novel object recognition, grip strength, rotarod, glucose tolerance test (GTT) and insulin tolerance test (ITT), body composition, and energy expenditure. The protocols can be performed longitudinally in the same mouse over a period of 4-6 weeks to test how candidate geroprotectors affect cardiac, cognitive, neuromuscular, and metabolic health.

Abstract B48: Targeting the semaphorin 4D-plexin B axis to augment FOLFIRINOX in a murine model of pancreatic adenocarcinoma

Abstract Background: Pancreatic adenocarcinoma (PDAC) is the fourth leading cause of cancer-related mortality, with dismal 5-year prognosis of 8%, in part due to poor response to available therapies. Thus, new systemic cancer control therapies are in dire need. Semaphorin 4D (SEMA4D) is a soluble and membrane bound glycoprotein that binds its cognate Plexin B1/B2 receptors, expressed on monocytic and granulocytic leukocytes. Prior work has shown that increased expression of SEMA4D and Plexin B in resected PDAC patients is associated with lymph node and distant metastasis, as well as a worse prognosis. Additionally, SEMA4D blockade has conferred improved immune checkpoint blockade response in murine models of colorectal carcinoma and head and neck squamous cell carcinoma via abrogation of myeloid-derived suppressor cell recruitment and function, as well as enhanced T-cell recruitment and activity within the tumor microenvironment. Here we study the effects of SEMA4D blockade in a murine model of PDAC. Methods: C57b/6 mice were orthotopically injected with murine PDAC line (KP2) derived from KRASG12D,TP53Flox/Wt;P48-Cre autochthonous tumors. Mice were treated with Folfirinox (5-FU, irinotecan, oxaliplatin, weekly), immune checkpoint blockade (ICB) (anti-PD1, anti-CTLA-4 mAbs bi-weekly), and anti-SEMA4D mAB (biweekly). Peripheral blood and tumor-infiltrating leukocytes from patients with PDAC undergoing pancreaticoduodenectomy were assessed for Plexin B1 via flow cytometry. Results: Human PDAC demonstrates penetration of Plexin B1 positive leukocytes, most notably tumor-associated macrophages, neutrophils, and monocytes. Mice injected with KP2 developed tumors detectable via high-frequency ultrasound and exhibited longer survival when treated with the combination of Folfirinox, ICB, and anti-SEMA4D antibody, compared to Folfirinox alone, Folfirinox plus ICB, or Folfirinox plus anti-SEMA4D antibody. Conclusions: Plexin B1+ myeloid subsets penetrate human PDAC tumors, and treatment with SEMA4D-blocking antibody improved response to ICB in combination with standard-of-care Folfirinox in preclinical murine studies. Future work will focus on understanding the immune mechanism of improved therapeutic response, as well as further characterization of the prevalence and prognostic ramifications of the SEMA4D-Plexin B axis in PDAC. Citation Format: Luis I. Ruffolo, Katherine M. Jackson, Nicholas Ullman, Alexander Chacon, Alexa Melucci, Paul Burchard, Mary Georger, Rachel Jewell, Peter Prieto, Brian Belt, Crystal Mallow, Elizabeth Evans, Terrence Fisher, Maurice Zauderer, Christina Wu, Brian Olson, Gregory B. Lesinski, David C. Linehan. Targeting the semaphorin 4D-plexin B axis to augment FOLFIRINOX in a murine model of pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B48.

A Phase 2, Open-Label, Multicenter Study Evaluating the Safety and Efficacy of Axicabtagene Ciloleucel in Combination with Either Rituximab or Lenalidomide in Patients with Refractory Large B-Cell Lymphoma (ZUMA-14)

A Phase 2, Open-Label, Multicenter Study Evaluating the Safety and Efficacy of Axicabtagene Ciloleucel in Combination with Either Rituximab or Lenalidomide in Patients with Refractory Large B-Cell Lymphoma (ZUMA-14)

Pre-Transplant Hepatic Steatosis (fatty liver) Predicts Chronic Graft-Vs-Host Disease but Does Not Affect Mortality

Introduction: Allogeneic hematopoietic stem cell transplant (allo-HCT) remains the only curative treatment for many hematologic conditions. However, significant mortality risk and risk of severe graft-vs-host disease (GvHD) limit its usefulness. Some patient characteristics such as performance status are used routinely as prognostic markers for poor outcomes after transplant. Steatohepatitis is a metabolic dysfunction manifesting as increased hepatic adiposity and resulting inflammation. A pre-clinical murine study suggests steatohepatitis is associated with GvHD. We assessed whether pre-HCT hepatic steatosis was associated with risk of developing GvHD and post transplant mortality. Methods: This retrospective study reviewed adult patients who underwent allogeneic stem cell transplants at Duke University over a 10-year period between 2008 and 2017 and had a computed tomography scan (CT) of the abdomen and pelvis with contrast within a 1-year period preceding the transplant. Patients with an acute illness as the indication for CT were excluded. We measured the attenuation of the liver vs. spleen as an estimate of hepatic steatosis. We used the widely accepted definition of hepatic steatosis as present when the difference in average attenuation between the spleen and liver was greater than or equal to 10 Hounsfield units and as absent when the difference was less than 10 Hounsfield units. Baseline pre-HCT factors as well as post-HCT outcomes were abstracted from the medical record. Results: We identified 80 patients with pre-HCT CT scans; of those, 59 (74%) had hepatic steatosis as defined above. Patients with hepatic steatosis tended to be older (median 52 vs. 38 years, p=0.0522); there were no statistically significant differences in gender, race, ethnicity, height, weight, Karnofsky Performance Status, HCT Comorbidity Index, history of diabetes, history of coronary artery disease, history of elevated liver function tests, primary disease, conditioning regimen, or stem cell source. Hepatic steatosis did not predict acute GvHD grade II-IV (OR 1.003, 95% CI 0.259 - 3.888, p=0.997). However, it was significantly associated with chronic GvHD on both univariate as well as multivariate analysis (Table 1, multivariate OR 3.83, 95% CI 1.11 - 13.28, p=0.023). There was no difference in overall survival or non-relapse mortality between the two groups. Conclusions: This study suggests that hepatic steatosis may predict chronic GvHD but does not predict acute GvHD or overall/non-relapse mortality. This study can be improved by using other imaging techniques such as a noncontrast CT, which is more accurate for assessment of hepatic steatosis. It is also important to note that imaging can only be used to predict the existence of hepatic steatosis; lobular inflammation, which is required to diagnose steatohepatitis, can only be proven on biopsy. Larger studies with liver biopsy or other noninvasive imaging measures of liver stiffness and steatosis will be needed to confirm the above results. Disclosures Gasparetto: Celgene: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed ; Janssen: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed ; BMS: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed . Horwitz:Abbvie Inc: Membership on an entity's Board of Directors or advisory committees. Rizzieri:Gilead Sciences: Consultancy, Speakers Bureau; Pfizer: Consultancy; Novartis: Consultancy; Millennium: Speakers Bureau; Jazz Pharmaceuticals: Speakers Bureau; AbbVie: Consultancy; Spectrum: Consultancy; Kite Pharma: Consultancy; Incyte: Consultancy, Speakers Bureau; TEVA: Consultancy; Seattle Genetics: Consultancy, Speakers Bureau; Amgen: Consultancy. Bashir:Metacrine, Inc.: Research Funding; ProSciento, Inc.: Research Funding; Pinnacle Clinical Research: Research Funding; CymaBay Therapeutics: Research Funding; Siemens Healthcare: Research Funding; NGM Biopharmaceuticals: Research Funding; Madrigal Pharmaceulticals: Research Funding. Sung:Novartis: Research Funding; Merck: Research Funding; Seres: Research Funding.