Immune Response In Cancer Therapy Research Articles

Metal ions-anchored bacterial outer membrane vesicles for enhanced ferroptosis induction and immune stimulation in targeted antitumor therapy

The activation of ferroptosis presents a versatile strategy for enhancing the antitumor immune responses in cancer therapy. However, developing ferroptosis inducers that combine high biocompatibility and therapeutic efficiency remains challenging. In this study, we propose a novel approach using biological nanoparticles derived from outer membrane vesicles (OMVs) of Escherichia coli for tumor treatment, aiming to activate ferroptosis and stimulate the immune responses. Specifically, we functionalize the OMVs by anchoring them with ferrous ions via electrostatic interactions and loading them with the STING agonist-4, followed by tumor-targeting DSPE-PEG-FA decoration, henceforth referred to as OMV/SaFeFA. The anchoring of ferrous ions endows the OMVs with peroxidase-like activity, capable of inducing cellular lipid peroxidation by catalyzing H2O2 to •OH. Furthermore, OMV/SaFeFA exhibits pH-responsive release of ferrous ions and the agonist, along with tumor-targeting capabilities, enabling tumor-specific therapy while minimizing side effects. Notably, the concurrent activation of the STING pathway and ferroptosis elicits robust antitumor responses in colon tumor-bearing mouse models, leading to exceptional therapeutic efficacy and prolonged survival. Importantly, no acute toxicity was observed in mice receiving OMV/SaFeFA treatments, underscoring its potential for future tumor therapy and clinical translation.

Closed-Loop Control of Macrophage Engineering Enabled by Focused-Ultrasound Responsive Mechanoluminescence Nanoplatform for Precise Cancer Immunotherapy.

Macrophage engineering has emerged as a promising approach for modulating the anti-tumor immune response in cancer therapy. However, the spatiotemporal control and real-time feedback of macrophage regulatory process is still challenging, leading to off-targeting effect and delayed efficacy monitoring therefore raising risk of immune overactivation and serious side effects. Herein, a focused ultrasound responsive immunomodulator-loaded optical nanoplatform (FUSION) is designed to achieve spatiotemporal control and status reporting of macrophage engineering in vivo. Under the stimulation of focused ultrasound (FUS), the immune agonist encapsulated in FUSION can be released to induce selective macrophage M1 phenotype differentiation at tumor site and the near-infrared mechanoluminescence of FUSION is generated simultaneously to indicate the initiation of immune activation. Meanwhile, the persistent luminescence of FUSION is enhanced due to hydroxyl radical generation in the pro-inflammatory M1 macrophages, which can report the effectiveness of macrophage regulation. Then, macrophages labeled with FUSION as a living immunotherapeutic agent (FUSION-M) are utilized for tumor targeting and focused ultrasound activated, immune cell-based cancer therapy. By combining the on-demand activation and feedback to form a closed loop, the nanoplatform in this work holds promise in advancing the controllability of macrophage engineering and cancer immunotherapy for precision medicine.

Role Of PD-1 Immune Checkpoint Inhibition in Lung Cancer Treatment

Non-small cell lung cancer (NSCLC) can be distinguished by histopathology and tumor markers. The treatment methods of NSCLC mainly include radiotherapy, chemotherapy, surgical treatment and TCM therapy. PD-1/PD-L1 immunotherapy has an advantage in combination therapy, producing a low-toxic, long-acting antitumor immune response in cancer therapy. This thesis describes the main methods of NSCLC therapy, details the PD-1/PD-L1 pathway and immunotherapy, and studies applications of three monoclonal antibodies in monotherapy and combination therapy. We conclude that the combination therapy has the outstanding advantage of safety, mild effect and prediction, but the problem of drug resistance to PD-1/PD-L1 needs to be solved urgently.

Polymer-mediated nanoformulations: a promising strategy for cancer immunotherapy.

Engineering polymer-based nano-systems have attracted many researchers owing to their unique qualities like shape, size, porosity, mechanical strength, biocompatibility, and biodegradability. Both natural and synthetic polymers can be tuned to get desired surface chemistry and functionalization to improve the efficacy of cancer therapy by promoting targeted delivery to the tumor site. Recent advancements in cancer immunoediting have been able to manage both primary tumor and metastatic lesions via activation of the immune system. The combinations of nano-biotechnology and immunotherapeutic agents have provided positive outcomes by enhancing the host immune response in cancer therapy. The nanoparticles have been functionalized using antibodies, targeted antigens, small molecule ligands, and other novel agents that can interact with biological systems at nanoscale levels. Several polymers, such as polyethylene glycol (PEG), poly(lactic-co-glycolic acid) (PLGA), poly(ε-caprolactone) (PCL), and chitosan, have been approved by the Food and Drug Administration for clinical use in biomedicine. The polymeric nanoformulations such as polymers-antibody/antigen conjugates and polymeric drug conjugates are currently being explored as nanomedicines that can target cancer cells directly or target immune cells to promote anti-cancer immunotherapy. In this review, we focus on scientific developments and advancements on engineered polymeric nano-systems in conjugation with immunotherapeutic agents targeting the tumor microenvironment to improve their efficacy and the safety for better clinical outcomes.

A Therapeutic Whole-Tumor-Cell Vaccine Covalently Conjugated with a TLR7 Agonist.

A single-protein or -peptide vaccine is not sufficient to arouse immune responses in cancer therapy. A whole-tumor-cell vaccine with complete cancer cell antigens and all conformations elicits robust immune responses and is a promising method for the treatment of advanced malignant tumors. In this study, we used 5-azacitidine to stimulate B16-F10 melanoma cells to express toll-like receptor (TLR) 3 on the cell surface and then chemically linked SZU-106, a small-molecule TLR7 agonist, to the cell surface with a pegylated linker to produce a novel whole-tumor-cell vaccine, abbreviated as Aza-BFcell-106. The vaccine stimulated mouse splenic lymphocytes and bone marrow-derived dendritic cells to secrete cytokines, promoted the maturation of dendritic cells and enhanced the capability of dendritic cells to present antigens. In a mouse model of melanoma, the vaccine effectively inhibited tumor growth, decreased tumor volume and prolonged survival. Further combination of the vaccine with a chemokine inhibitor, reparixin, significantly increased the infiltration of CD4+ and CD8+ T cells into the tumor environment, while the antitumor effect was significantly enhanced. The whole-tumor-cell vaccine Aza-BFcell-106 induced immune-activating responses in both in vitro and in vivo experiments, indicating that this vaccine has great potential to treat advanced malignant tumors.

Abstract 3205: Role of RIG-I in tumor endothelium

Abstract The immune microenvironment plays a critical role in the efficacy of cancer treatment. The manipulation of cytosolic nucleic acid sensors has become a strategy to boost the immune response in cancer therapy, but it is critical to understand how these nucleic acid sensors work in the tumor microenvironment. One aspect of the immune microenvironment is the nucleic acid sensor, which recognizes pathogenic nucleic acids and activates an immune response. Retinoic acid-inducible gene I (RIG-I) is an RNA sensor that responds to dsRNA by activating a type I interferon response. It has been found that RIG-I activation can induce an anti-tumor immune response, but its role in the tumor microenvironment is unknown. Prior studies show regulation of the innate immune response in endothelium can increase the anti-tumor response. Understanding the role of RIG-I in endothelial cells, and how this can be used to potentially reprogram the tumor microenvironment, is critical for developing more effective cancer treatments. In addition, my research on the effects of RIG-I in endothelium has wide-reaching implications beyond cancer treatment. I hypothesize RIG-I activation in endothelial cells will produce an anti-tumor immune response. My findings show that endothelial RIG-I activates a robust type I interferon response and inhibits EC function including, inducing apoptosis and inhibiting migration, which is indicative that RIG-I plays a role in the endothelial immune response. RIG-I also plays a role in the expression of the several angiogenic regulators in a tissue-specific manner. This research will provide critical knowledge about the role of RIG-I in tumor angiogenesis, and provide novel treatment avenues for solid tumors. Citation Format: Adrian M. Baris, Eugenia Fraile-Bethencourt, Sokchea Khou, Rebecca Ruhl, Clay Hudson, Sudarshan Anand. Role of RIG-I in tumor endothelium [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 3205.

Role of RIG-I in tumor endothelium.

Abstract The immune microenvironment plays a critical role in the efficacy of cancer treatment. The manipulation of cytosolic nucleic acid sensors has become a strategy to boost the immune response in cancer therapy, but it is critical to understand how these nucleic acid sensors work in the tumor microenvironment. One aspect of the immune microenvironment is the nucleic acid sensor, which recognizes pathogenic nucleic acids and activates an immune response. Retinoic acid-inducible gene I (RIG-I) is an RNA sensor that responds to dsRNA by activating a type I interferon response. It has been found that RIG-I activation can induce an anti-tumor immune response, but its role in the tumor microenvironment is unknown. Prior studies show regulation of the innate immune response in endothelium can increase the anti-tumor response. Understanding the role of RIG-I in endothelial cells, and how this can be used to potentially reprogram the tumor microenvironment, is critical for developing more effective cancer treatments. In addition, my research on the effects of RIG-I in endothelium has wide-reaching implications beyond cancer treatment. I hypothesize RIG-I activation in endothelial cells will produce an anti-tumor immune response. My findings show that endothelial RIG-I activates a robust type I interferon response and inhibits EC function including, inducing apoptosis and inhibiting migration, which is indicative that RIG-I plays a role in the endothelial immune response. RIG-I also plays a role in the expression of the several angiogenic regulators in a tissue-specific manner. This research will provide critical knowledge about the role of RIG-I in tumor angiogenesis, and provide novel treatment avenues for solid tumors. Supported by grants from NIH (T32) and Knight (CVP-002)

Towards an Implantable Fluorescence Image Sensor for Real-Time Monitoring of Immune Response in Cancer Therapy.

Real-time monitoring of cellular-level changes inside the body provides key information regarding disease progression and therapy assessment for critical care including cancer therapy. Current state-of-the-art oncological imaging methods impose unnecessary latencies to detect small cell foci. Invasive methods such as biopsies, on the other hand, cause disruption if deployed on a repeated basis. Therefore, they are not practical for real-time assessments of the tumor tissue. This work presents a proof-of-concept design for an implantable fluorescence lensless image sensor to address the pervasive challenge of real-time tracking of the immune response in immunotherapy. The 2.4x4.7 mm2 integrated circuit (IC) prototype consists of a 36 by 40 pixel array, a laser driver and a power management unit harvesting power and transferring 11.5 kbits/frame through a wireless ultrasound link while implanted 2 cm deep inside the body. Compared to prior art, this is the first full-fledged wireless system implementing chip-scale fluorescence microscopy to the best of our knowledge.Clinical relevance- This prototype can be used to personalize immunotherapy for the 50% of cancer patients who do not initially respond to the therapy.

Advances in Engineered Polymer Nanoparticle Tracking Platforms towards Cancer Immunotherapy-Current Status and Future Perspectives.

Engineering polymeric nanoparticles for their shape, size, surface chemistry, and functionalization using various targeting molecules has shown improved biomedical applications for nanoparticles. Polymeric nanoparticles have created tremendous therapeutic platforms, particularly applications related to chemo- and immunotherapies in cancer. Recently advancements in immunotherapies have broadened this field in immunology and biomedical engineering, where “immunoengineering” creates solutions to target translational science. In this regard, the nanoengineering field has offered the various techniques necessary to manufacture and assemble multifunctional polymeric nanomaterial systems. These include nanoparticles functionalized using antibodies, small molecule ligands, targeted peptides, proteins, and other novel agents that trigger and encourage biological systems to accept the engineered materials as immune enhancers or as vaccines to elevate therapeutic functions. Strategies to engineer polymeric nanoparticles with therapeutic and targeting molecules can provide solutions for developing immune vaccines via maintaining the receptor storage in T- and B cells. Furthermore, cancer immunotherapy using polymeric nanomaterials can serve as a gold standard approach for treating primary and metastasized tumors. The current status of the limited availability of immuno-therapeutic drugs highlights the importance of polymeric nanomaterial platforms to improve the outcomes via delivering anticancer agents at localized sites, thereby enhancing the host immune response in cancer therapy. This review mainly focuses on the potential scientific enhancements and recent developments in cancer immunotherapies by explicitly discussing the role of polymeric nanocarriers as nano-vaccines. We also briefly discuss the role of multifunctional nanomaterials for their therapeutic impacts on translational clinical applications.

Monitoring Cellular Immune Responses in Cancer Therapy

Monitoring Cellular Immune Responses in Cancer Therapy

Ag2S nanoparticle-mediated multiple ablations reinvigorates the immune response for enhanced cancer photo-immunotherapy

Photothermal therapy (PTT) has been widely used in cancer treatment in recent years. However, it is difficult to completely eliminate tumors by single PTT, and the effects of single dose of PTT frequency on the therapeutic outcome of PTT and the multiple PTT-induced immune response in cancer therapy also remain unclear. Here, water-soluble Ag2S nanoparticles (NPs) with optimal particle size (~15 nm) were synthesized and used as the PTT agents. The in vitro and in vivo results demonstrated that Ag2S NPs had good photothermal conversion in response to the irradiation of an 808 nm laser, and the results indicated that the NPs have potential as contrast agents for photoacoustic imaging as well as good biocompatibility. The in vivo results further revealed that the frequency of the Ag2S NP-mediated PTT affected the cancer therapeutic outcome. The increase of frequency efficiently reduced the primary tumor recurrence and alleviated metastasis. The present study suggested that the mechanism involves multiple PTT cycles inhibiting the proliferation of primary tumor cells and stimulating the systematic immune response in the mouse breast cancer model. Therefore, frequency optimization in photothermal ablation may provide a promising strategy to enhance the therapeutic outcome in cancer therapy.

Photodynamic Therapy in Combination with Sorafenib for Enhanced Immunotherapy of Lung Cancer.

The emerging of cancer immunotherapy is a great progress in cancer therapy. However, accumulating evidences have shown that tumor microenvironment (TME) exerted strong inhibition effects on cancer immunotherapy. In order to solve this issue, a cell membrane vehicle (CMV) was developed and employed to encapsulate both chlorins e6 (Ce6) and sorafenib (Sfn). The obtained drug delivery system (DDS, CMV/C-S was expected to enhance the immune response in cancer therapy by remodeling the TME. The results showed that CMV/C-S was highly stable under physiological environment with responsive drug release upon laser irradiations and high tumor targetability, which all contributed to promising anticancer performance in vitro / in vivo. Especially, the photodynamic nature of Ce6 could exert significant immunogenic cell death (ICD) to trigger immune response. At the same time, with the TME regulation effects of Sfn, the outcome of cancer immunotherapy was significantly enhanced as compare to mono-therapies. The study offers a novel approach for effective cancer immunotherapy.

Cord blood stem cell derived CD16+ NK cells eradicated acute lymphoblastic leukemia cells using with anti-CD47 antibody

Acute lymphoblastic leukemia (ALL) is an aggressive cancer in children and adults which possess higher CD47 expression than normal cells. ALL chemotherapy has a lot of side effects and in most cases is ineffective. However arrival of Natural killer (NK) cell immunotherapy raised hopes for successful treatment of cancers, tailoring NK cells to meet clinical requirements is still under investigation. Of note, CD16+ (FCγIIIa) NK cells eliminate tumor cells with antibody dependent cell cytotoxicity (ADCC) mechanism. Therefore, we evaluated ADCC effect of cord blood stem cell derived CD16+ NK cells with using anti CD47 blocking antibody. CD16+ NK cells generated efficiently from CD34 positive cord blood cells in vitro using IL-2, IL-15 and IL-21 cytokines, although it was not dose dependent. CD16+ cells derived from CD34+ cells in day 14 of culture efficiently increased apoptosis in ALL cells, produced INFγ and increased CD107-a expression when used anti CD47 antibody (increased around 30–40%). Interestingly, CD16+ NK cell cytotoxicity slightly increased in combination with macrophages against ALL cells (around 10%). Taken together, our findings induced this hope that cord blood stem cell derived CD16+ NK cells exploit antitumor immune response in cancer therapy with using anti-CD47 antibody.

Extracellular Vesicles Released by Colorectal Cancer Cell Lines Modulate Innate Immune Response in Zebrafish Model: The Possible Role of Human Endogenous Retroviruses.

Extracellular vesicles (EVs) are important components of the metastatic niche and are crucial in infiltration, metastasis, and immune tolerance processes during tumorigenesis. We hypothesized that human endogenous retroviruses (HERV) positive EVs derived from tumor cellsmay have a role in modulating the innate immune response. The study was conducted in two different colorectal cancer cell lines, representing different stages of cancer development: Caco-2, derived from a non-metastatic colorectal adenocarcinoma, and SK-CO-1, derived from metastatic colorectal adenocarcinoma (ascites). Both cell lines were treated with decitabine to induce global hypomethylation and to reactivate HERV expression. EVs were quantified by nanoparticle tracking analysis, and HERV-positive EV concentrations were measured by flow cytometry. The effect of EVs isolated from both untreated and decitabine-treated cells on the innate immune response was evaluated by injecting them in zebrafish embryos and then assessing Interleukin 1β (IL1-β), Interleukin 10 (IL-10), and the myeloperoxidase (mpx) expression levels by real-time qPCR. Interestingly, HERV-K positive EVs concentrations were significantly associated with a reduced expression of IL1-β and mpx, supporting our hypothesis that HERV-positive EVs may act as immunomodulators in tumor progression. The obtained results open new perspectives about the modulation of the immune response in cancer therapy.

Current Status and Future Directions of Nanoparticulate Strategy for Cancer Immunotherapy.

Rapid advancement over the past few decades in cancer immunotherapy provides life-saving options for cancer patients. However, commonly used strategies including small molecules and various biomacromolecule-based therapeutics suffer from serious off-target toxicity and a lack of stability in the circulation. To overcome these problems, various nanoparticulate delivery systems have been developed to achieve controlled and sustained drug release, improved stability and pharmacokinetic profiles, and tumor specificity to reduce off-target adverse effects. We reviewed representative studies on multiple nanoparticulate platform systems for delivering therapeutics in cancer immunotherapy, and discussed the advances and perspectives for the future development of novel therapeutics in cancer immunotherapy. Results and Perspectives: Nanoparticles for the controlled delivery of immune modulating agents represents a viable approach in cancer immunotherapy. Besides seeking novel carrier systems or new materials, efforts need to be contributed to delineating the impact of intrinsic properties of nanoparticles such as material composition, morphology, size distribution, charge, and stiffness in manipulating immune responses in cancer therapy.

Abstract IA29: Mice host selection for patient-derived xenograft (PDX) model development and other critical factors for success

Abstract IA29: Mice host selection for patient-derived xenograft (PDX) model development and other critical factors for success

Abstract LB-050: Patient-derived tumor xenografts in humanized NSG mice: a model to study immune responses in cancer therapy

Abstract Mouse models are frequently used to test the therapeutic efficacy of anti-cancer drugs. However, the translation of murine experimental data to treatments for patients with cancer often fails due to significant differences between the species, including the differences in the immune system. Our goal is to bridge this gap and to establish an in vivo preclinical model of human tumor immunotherapy by engrafting immunodeficient mice expressing a partial human immune system with human tumor implants. Humanized NOD-scid IL2Rγ (null) (hu-NSG) mice were initially generated by transplanting NSG mice with human CD34+ hematopoietic stem and progenitor cells (HSPCs) which support human hematopoietic and immune system development. Hu-NSG mice develop functional human T cells and B cells with high levels of TCR excision circles, complex TCR repertoire diversity and antigen-specific T cell proliferative responses. Several types of patient-derived tumors (non small cell lung cancer, sarcoma, triple negative breast cancer and invasive bladder cancer) were successfully implanted into HLA mismatched hu-NSG mice. Tumor growth curves show a delay in tumor growth in hu-NSG compared to non-humanized NSG mice. In a colon cancer xenograft model, treatment with chemotherapy agent (5-FU) or with a therapeutic antibody directed against VEGF (Avastin) resulted in decreased tumor growth. In addition to PDX tumors we have also tested human cancer cell lines. Tumor growth was observed in all hu-NSG mice implanted with human ovarian tumor cell line SKOV3-Luc-D3 cells at different time points post HSPC engraftment, showing no evidence of tumor rejection. Thus, our model of humanized mice bearing tumor-derived xenografts provides opportunities to study both the safety and efficacy of current cancer therapies. Citation Format: Minan Wang, James G. Keck, Mingshan Cheng, Danying Cai, Leonard Shultz, Karolina Palucka, Jacques Banchereau, Carol Bult, Rick Huntress. Patient-derived tumor xenografts in humanized NSG mice: a model to study immune responses in cancer therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-050. doi:10.1158/1538-7445.AM2015-LB-050

Single Cell Functional Proteomics for Assessing Immune Response in Cancer Therapy: Technology, Methods, and Applications

In the past decade, significant progresses have taken place in the field of cancer immunotherapeutics, which are being developed for most human cancers. New immunotherapeutics, such as Ipilimumab (anti-CTLA-4), have been approved for clinical treatment; cell-based immunotherapies such as adoptive cell transfer (ACT) have either passed the final stage of human studies (e.g., Sipuleucel-T) for the treatment of selected neoplastic malignancies or reached the stage of phase II/III clinical trials. Immunotherapetics has become a sophisticated field. Multimodal therapeutic regimens comprising several functional modules (up to five in the case of ACT) have been developed to provide focused therapeutic responses with improved efficacy and reduced side-effects. However, a major challenge remains: the lack of effective and clinically applicable immune assessment methods. Due to the complexity of antitumor immune responses within patients, it is difficult to provide comprehensive assessment of therapeutic efficacy and mechanism. To address this challenge, new technologies have been developed to directly profile the cellular immune functions and the functional heterogeneity. With the goal to measure the functional proteomics of single immune cells, these technologies are informative, sensitive, high-throughput, and highly multiplex. They have been used to uncover new knowledge of cellular immune functions and have been utilized for rapid, informative, and longitudinal monitoring of immune response in clinical anti-cancer treatment. In addition, new computational tools are required to integrate high-dimensional data sets generated from the comprehensive, single cell level measurements of patient’s immune responses to guide accurate and definitive diagnostic decision. These single cell immune function assessment tools will likely contribute to new understanding of therapy mechanism, pre-treatment stratification of patients, and ongoing therapeutic monitoring and assessment.

Therapeutic efficacy of a fully human anti-CD27 monoclonal antibody in a murine colon carcinoma model (162.23)

Abstract The costimulatory molecule CD27 is constitutively expressed on the majority of mature T cells, memory B cells, and a portion of NK cells. The interaction of CD27 with its ligand CD70 plays an important role in effector capacity and memory in T cells; in clonal B cell expansion and germinal center formation; and in NK cell cytolytic activity. Agonistic anti-mouse CD27 mAbs have been shown to have potent anti-tumor activity. A panel of fully human antibodies recognizing human CD27 was generated and we have previously shown that our lead clone (1F5) can mediate anti-tumor effects using the BCL1 B-lymphoma line in human CD27-transgenic (hCD27-Tg) mice. In order to further investigate the mechanism of this anti-hCD27 monoclonal and its activity in a therapeutic setting we assessed anti-tumor activity using the CT26 murine colon carcinoma line. CT26 cells were delivered s.c. to hCD27-Tg animals and five doses of 1F5 were delivered to mice i.p. beginning on days 3, 5, or 7. In multiple experiments, tumor growth in mice treated with 1F5 was substantially delayed or prevented compared to that of control-treated mice. When 1F5-treated surviving mice were rechallenged with CT26 cells, without additional anti-CD27 antibody treatment, tumors did not grow in most animals. These data support the continued clinical development of this anti-CD27 mAb to enhance immune responses in cancer therapy. Investigations of immune cell subset depletions and combination therapies are ongoing.

Abstract 4560: Anti-tumor activity of a fully human anti-CD27 monoclonal antibody in a transgenic mouse model

Abstract The costimulatory molecule CD27 is a member of the TNF receptor superfamily, and is constitutively expressed on the majority of mature T cells, memory B cells, and a portion of NK cells. The interaction of CD27 with its ligand CD70 plays an important role in the activation, proliferation, survival, and maturation of effector capacity and memory in T cells; in clonal B cell expansion and germinal center formation; and in NK cell cytolytic activity. Previous published work demonstrated that agonistic anti-mouse CD27 mAbs, given without a DC maturation signal, have potent anti-tumor activity through boosting of T cell immunity. To explore the therapeutic potential of this target, a panel of fully human antibodies recognizing human CD27 was generated using human Ig transgenic mice immunized with recombinant CD27. These anti-CD27 mAbs showed specific and high affinity binding to recombinant CD27 and CD27-expressing lymphoma cells. Human CD27-transgenic (hCD27-Tg) mice were generated to evaluate the anti-CD27 mAbs in vivo. The CD27-Tg mouse line was back-crossed onto a Balb/c background in order to assess anti-tumor activity using the BCL1 B-lymphoma line. Approximately 107 BCL1 cells were delivered i.v. to backcrossed animals on day 0. Doses of 150 to 600 ug of our lead anti-CD27 mAb (clone 1F5) were delivered to mice i.p. on days 3, 5, 7, 9 and 11. In multiple experiments, tumor growth in mice treated with the anti-CD27 mAb 1F5 was substantially delayed compared to that of control-treated mice. Further, many anti-CD27 treated animals did not show evidence of tumor growth several weeks past the point where all control animals had been euthanized. These data confirm that anti-human CD27 mAbs can mediate similar anti-tumor effects as the anti-mouse CD27 agonist antibodies. The 1F5 antibody was also demonstrated to cross-react with CD27 from cynomolgus monkeys, and in a small pilot study was well tolerated and without evidence of significant lymphocyte activation. Taken together the data support the therapeutic potential of this anti-CD27 mAb to enhance immune responses in cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4560. doi:10.1158/1538-7445.AM2011-4560