Immunotherapy In Murine Models Research Articles

Inhibition of CDC20 potentiates anti-tumor immunity through facilitating GSDME-mediated pyroptosis in prostate cancer

BackgroundIncreasing evidence suggests that immunotherapy, especially immune checkpoint inhibitors (ICIs), has the potential to facilitate long-term survival in various cancer besides prostate cancer. Emerging evidence indicated that pyroptosis, an immunogenic form of cell death, could trigger an anti-tumor immune microenvironment and enhance the effectiveness of immunotherapy. Nevertheless, the mechanism underlying the regulation of pyroptosis signaling in prostate cancer remains unclear.MethodsThe differential expression of human E3 ligases in prostate cancer was integratedly analyzed from five independent public datasets. Moreover, the immunohistochemistry analysis of a tissue microarray derived from prostate cancer patients confirmed the results from the bioinformatic analysis. Furthermore, prostate cancer cell lines were evaluated via the next-generation RNA sequencing to assess transcriptomic profile upon CDC20 depletion. Next, qRT-PCR, Western blotting, cycloheximide assay, immunoprecipitation, and ubiquitination assay were employed to explore the correlation and interaction between CDC20 and GSDME. Both immune-deficient and immune-competent murine models were utilized to examine the anti-tumor efficacy of CDC20 inhibition with or without the anti-PD1 antibodies, respectively. To analyze the immune microenvironment of the xenografts, the tumor tissues were examined by immunohistochemistry and flow cytometry.ResultsThe analysis of multiple prostate cancer cohorts suggested that CDC20 was the most significantly over-expressed E3 ligase. In addition, CDC20 exerted a negative regulatory effect on the pyroptosis pathway by targeting GSDME for ubiquitination-mediated proteolysis in a degron-dependent manner. Knockdown of CDC20 leads to increased GSDME abundance and a transition from apoptosis to pyroptosis in response to death signals. Furthermore, in our syngeneic murine models, we found that depletion of CDC20 significantly enhances the anti-tumor immunity by promoting the infiltration of CD8+ T lymphocytes dependent on the existence of GSDME, as well as reducing myeloid immune cells. More importantly, Apcin, a small molecular inhibitor that targets CDC20, exhibited synergistic effects with anti-PD1-based immunotherapy in murine models of prostate cancer.ConclusionsOverall, these findings provide new insights into the upstream regulation of GSDME-mediated pyroptosis by CDC20, which specifically interacts with GSDME and facilitates its ubiquitination in a degron-dependent manner. Importantly, our data highlight novel molecular pathways for targeting cellular pyroptosis and enhancing the effectiveness of anti-PD1-based immunotherapy.

Inhibition of tumor intrinsic BANF1 activates antitumor immune responses via cGAS-STING and enhances the efficacy of PD-1 blockade

BackgroundBANF1 is well known as a natural opponent of cyclic GMP-AMP synthase (cGAS) activity on genomic self-DNA. However, the roles of BANF1 in tumor immunity remain unclear. Here, we investigate...

A phase 2, two-stage study of mirvetuximab soravtansine (IMGN853) in combination with pembrolizumab in patients with microsatellite stable (MSS) endometrial cancer (EC).

TPS5611 Background: Folate receptor-alpha (FRα) is expressed on endometrial cancer (EC) cells and is associated with poor prognosis. Mirvetuximab soravtansine (ImmunoGen), an antibody drug conjugate (ADC) comprising a FRα-binding antibody, cleavable linker, and the tubulin-disrupting maytansinoid DM4, showed tolerability and single agent activity in a Phase 1 study with dose expansion in FRα+ advanced/recurrent EC (NCT01609556) and also when combined with chemotherapy, bevacizumab as well as pembrolizumab (NCT02606305). In addition to having direct target-mediated cytotoxicity, ADCs also stimulate the local tumor immune microenvironment. Mirvetuximab soravtansine has been shown to activate monocytes and promote phagocytosis of mirvetuximab-treated FRα-positive tumor cells through a mechanism of Fc-FcγR interaction. Further, the combination of ADCs with immune checkpoint inhibitors (ICI) can overcome primary resistance to immunotherapy in murine models. Given the low response of MSS endometrial cancers to PD-1 blockade, we hypothesized that addition of mirvetuximab may enhance response of these tumors to immunotherapy. Methods: This is a Phase 2, single cohort study of mirvetuximab soravtansine with pembrolizumab in recurrent or persistent EC. Patients must have advanced or recurrent MSS serous endometrial cancer with at least 1 and up to 3 prior lines of therapy. Confirmation of FRα expression (with PS2+ staining intensity in ≥ 50% of cells, performed centrally at Ventana Medical Systems, Inc) is required. Prior receipt of ICI is excluded. Patients will receive the combination of mirvetuximab soravtansine 6 mg/kg AIBW IV and pembrolizumab 200 mg IV administered every 21 days. The co-primary endpoint is progression-free survival at 6 months (PFS6) and objective response rate (ORR) by RECIST 1.1. Translational objectives include assessment of tumor infiltrating lymphocytes (TILs), expression of immune checkpoint markers, and whole exome sequencing (WES) for DNA repair pathway mutations, neoantigens, and polymorphisms in immunologically relevant genes. Statistical considerations are for a Simon two-stage optimal design with 16 patients in Stage 1 and 19 patients in Stage 2, to a total of 35. Prespecified activity for the first stage of accrual was met, and second stage accrual began November 2020. Clinical trial information: NCT03835819.

Tumor Membrane Vesicle Vaccine Augments the Efficacy of Anti-PD1 Antibody in Immune Checkpoint Inhibitor-Resistant Squamous Cell Carcinoma Models of Head and Neck Cancer.

Immune checkpoint inhibitor (ICI) immunotherapy improved the survival of head and neck squamous cell carcinoma (HNSCC) patients. However, more than 80% of the patients are still resistant to this therapy. To test whether the efficacy of ICI therapy can be improved by vaccine-induced immunity, we investigated the efficacy of a tumor membrane-based vaccine immunotherapy in murine models of HNSCC. The tumors, grown subcutaneously, are used to prepare tumor membrane vesicles (TMVs). TMVs are then incorporated with glycolipid-anchored immunostimulatory molecules GPI-B7-1 and GPI-IL-12 by protein transfer to generate the TMV vaccine. This TMV vaccine inhibited tumor growth and improved the survival of mice challenged with SCCVII tumor cells. The tumor-free mice survived for several months, remained tumor-free, and were protected following a secondary tumor cell challenge, suggesting that the TMV vaccine induced an anti-tumor immune memory response. However, no synergy with anti-PD1 mAb was observed in this model. In contrast, the TMV vaccine was effective in inhibiting MOC1 and MOC2 murine oral cancer models and synergized with anti-PD1 mAb in extending the survival of tumor-bearing mice. These observations suggest that tumor tissue based TMV vaccines can be harnessed to develop an effective personalized immunotherapy for HNSCC that can enhance the efficacy of immune checkpoint inhibitors.

Non-thermal histotripsy tumor ablation promotes abscopal immune responses that enhance cancer immunotherapy

BackgroundDeveloping the ability to use tumor-directed therapies to trigger potentially therapeutic immune responses against cancer antigens remains a high priority for cancer immunotherapy. We hypothesized that histotripsy, a novel non-invasive,...

Anti-tumor immunity generated as an artifact of tumor implantation determines the response to immunotherapy in murine models

Abstract Cancer cell lines grown in vitro and implanted into mice are a centerpiece of preclinical modeling. However, tumor implantation is an in vivo vaccination event that can impact tumor growth. Checkpoint inhibitors targeting PD1 or CTLA4 interactions are effective at unleashing suppressed pre-existing immunity in murine models, but do not generate new immune responses. We hypothesized that tumor control by checkpoint inhibitor immunotherapies was dependent on pre-existing immunity generated at tumor implantation. Using cancer cells engineered to express model antigens, spontaneous tumor models with defined trackable antigens, or unmodified cancer cells, we demonstrate that tumor implantation results in initial T cell mediated immunity. As the tumors progress, these cells become undetectable in the periphery and accumulate in the tumor, but do not prevent tumor progression. While tumors respond to checkpoint inhibitors administered closely following implantation, delayed administration results in a loss of efficacy. This efficacy can be recovered by the addition of radiation therapy to checkpoint inhibitors, permitting cure of established murine tumors that are not controlled by either therapy alone. However, blocking the immune response at tumor implantation using a range of approaches results in a complete loss of efficacy of tumor control by all therapies based around checkpoint inhibitors. We demonstrate an approach to ‘silently’ establish tumors in mice to test therapies that can initiate de novo immunity to tumors. These data have significant implications for current clinical attempts to use checkpoint inhibitors, which may not be a solution for patients without pre-existing immunity to their tumor.

Surface biotinylation of cytotoxic T lymphocytes for in vivo tracking of tumor immunotherapy in murine models.

Currently, there is no stable and flexible method to label and track cytotoxic T lymphocytes (CTLs) in vivo in CTL immunotherapy. We aimed to evaluate whether the sulfo-hydroxysuccinimide (NHS)-biotin-streptavidin (SA) platform could chemically modify the cell surface of CTLs for in vivo tracking. CD8+ T lymphocytes were labeled with sulfo-NHS-biotin under different conditions and then incubated with SA-Alexa647. Labeling efficiency was proportional to sulfo-NHS-biotin concentration. CD8+ T lymphocytes could be labeled with higher efficiency with sulfo-NHS-biotin in DPBS than in RPMI (P<0.05). Incubation temperature was not a key factor. CTLs maintained sufficient labeling for at least 72h (P<0.05), without altering cell viability. After co-culturing labeled CTLs with mouse glioma stem cells (GSCs) engineered to present biotin on their surface, targeting CTLs could specifically target biotin-presenting GSCs and inhibited cell proliferation (P<0.01) and tumor spheres formation. In a biotin-presenting GSC brain tumor model, targeting CTLs could be detected in biotin-presenting gliomas in mouse brains but not in the non-tumor-bearing contralateral hemispheres (P<0.05). In vivo fluorescent molecular tomography imaging in a subcutaneous U87 mouse model confirmed that targeting CTLs homed in on the biotin-presenting U87 tumors but not the control U87 tumors. PET imaging with 89Zr-deferoxamine-biotin and SA showed a rapid clearance of the PET signal over 24h in the control tumor, while only minimally decreased in the targeted tumor. Thus, sulfo-NHS-biotin-SA labeling is an efficient method to noninvasively track the migration of adoptive transferred CTLs and does not alter CTL viability or interfere with CTL-mediated cytotoxic activity.

Improved Efficacy of Dendritic Cell–Based Immunotherapy by Cutaneous Laser Illumination

The present study investigates a convenient laser-based approach to enhance dendritic cell (DC) migration and improve DC-based immunotherapy in murine models. Influence of laser illumination on dermal tissue microenvironment and migration of DCs following intradermal injection were determined by whole-mount immunohistochemistry, transmission electron microscope, and flow cytometry. We also investigated in vivo expansion of CTLs by flow cytometry, CTL activity by in vitro CTL assay, and antitumor efficacy of DC immunization following cutaneous laser illumination in both preventive and therapeutic tumor models. Laser illumination was found to significantly enlarge perforations in the perilymphatic basement membrane, disarray collagen fibers, and disrupt cell-matrix interactions in the dermis. The altered dermal tissue microenvironment permitted more efficient migration of intradermally injected DCs from the dermis to the draining lymph nodes (dLN). Laser illumination also slightly but significantly enhanced the expression of costimulatory molecule CD80 and MHC I on inoculated DCs. As a result, more vigorous expansion of tumor-specific IFN-γ(+)CD8(+) T lymphocytes and enhanced CTL activity against 4T1 but not irrelevant tumor cells were obtained in the laser-treated group over the control group. Laser-augmented DC immunization also completely abrogated early growth of 4T1 tumor and B16F10 melanoma in preventive tumor models and significantly extended the survival of 4T1-resected mice in a therapeutic tumor model. These data suggest a simple, safe, laser-based approach to significantly enhance DC-based immunotherapy.

Sensitive In Vivo Detection of Primary T Cells Expressing Membrane-Anchored Gaussia Luciferase for the Study of Adoptive T Cell Immunotherapy in Murine Models of Malignancy.

Current approaches to in vivo bioluminescent imaging (BLI) of T cells utilizing luciferase enzymes may be compromised by poor transduction efficiencies in primary T cells, and low photon emissions. Here we describe a novel and widely applicable approach to in vivo BLI of primary T cells utilizing a membrane-anchored form of the naturally secreted Guassia luciferase (GLuc) enzyme, termed exGLuc. We constructed exGLuc by fusion of the GLuc gene to the coding region of the CD8 transmembrane domain. The resulting exGLuc enzyme is anchored to the cell surface of retrovirally transduced cells. In vitro, cells which expressed the exGLuc enzyme demonstrated a markedly (>9 fold) increased bioluminescent signal when compared to cells which expressed the native GLuc (GLuc), the related Rhenilla luciferase (RLuc), a membrane-anchored form of RLuc (exRLuc), or a green fluorescent protein (GFP)-fire fly luciferase fusion protein. Following injection into SCID-Beige mice, MHC-mismatched C57BL6 T cells transduced to express exGLuc were detected by BLI generating graft versus host disease at an earlier time point and demonstrated a >10 fold increased bioluminescent signal when compared to infused C57BL6 T cells expressing GLuc, RLuc, or exRLuc. We further demonstrate homing of OVA-specific DO11.10 exGLuc+ T cells to A20(OVA) but not A20(GFP) subcutaneous tumors in both SCID-Beige and Balb/c mice. We further successfully applied this strategy to the study of in vivo human T cell homing using a xenogeneic SCID-Beige tumor model. Specifically, we demonstrate that human T cells, retrovirally co-transduced to express both a CD19-specific chimeric antigen receptor (CAR), 19z1, and exGLuc, could be monitored over time, and that these T cells quite rapidly home to subcutaneous CD19+ acute lymphoblastic leukemia (NALM-6) tumors when compared to T cells co-expressing an irrelevant CAR with exGLuc. Furthermore, we were able to demonstrate for the first time specific homing of 19z1/exGLuc+ human T cells to systemic NALM-6 tumor, detecting exGLuc+ T cells in deep tissues including the bone marrow, spleen, and liver. We conclude that the exGLuc enzyme emits a superior bioluminescent signal when compared to other commonly utilized luciferase enzymes; that primary T cells are readily transduced to express the exGLuc enzyme; and that exGLuc+ T cells may be accurately monitored in vivo over time by BLI. Based on these data, we believe that this novel approach to primary T cell in vivo imaging will significantly enhance the study of adoptive T cell immunotherapy in murine models of leukemia and other malignancies.

Allogeneic cell-mediated immunotherapy for eradication of minimal residual disease: Comparison of T-cell and IL-2 activated killer (LAK) cell–mediated adoptive immunotherapy in murine models

In the course of allogeneic bone marrow transplantation (BMT), avoiding graft-versus-host disease (GVHD) while retaining the antileukemic effects of the T cells remains a major challenge. T-cell depletion (TCD) reduces the incidence of GVHD but increases the relapse rate after allogeneic BMT. We attempted to develop a regimen that would retain or increase the graft-versus-leukemia effect induced by donor T cells while preventing GVHD. Immunosuppressed mice were given immunocompetent donor cells, i.e., fresh lymphocytes or lymphokine-activated killer (LAK) cells differing from the host in major (MHC) or minor (MiHC) histocompatibility antigens. Engraftment of donor cells was documented by polymerase chain reaction analysis. Administration of MHC- and MiHC-incompatible allogeneic LAK cells, especially in conjunction with recombinant interleukin-2 (rIL-2), increased disease manifestations and mortality associated with GVHD. On the other hand, irradiated LAK cells or TCD-LAK cells prevented GVHD in both mice models studied. Phenotypic analysis of LAK cells demonstrated that CD8 +-equivalent (Lyt-2) T cells are of significance in aggravation of GVHD. The in vitro cytotoxic capacity of LAK cells against MHC-nonrestricted target cells was not reduced by either irradiation or TCD. These results provide the background for designing improved protocols for immunotherapy of residual disease after BMT. In addition, the data imply that antitumor effects may be retained by irradiated rIL-2–activated allogeneic cells without causing GVHD. Whereas unmodified allogeneic LAK cells can induce more effective graft-versus-leukemia effects at the cost of GVHD, irradiated allogeneic donor LAK cells might play some role in eradication of minimal residual disease following autologous or allogeneic BMT without causing GVHD.