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Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors.

ABSTRACT: Activation of Toll-like receptor 9 (TLR9) is known to foster innate and adaptive immune responses and thus improve immune-mediated control of malignant disease. Lefitolimod is a potent TLR9 agonist without chemical modification developed for immunotherapeutic strategies. Modulation of the tumor microenvironment (TME) is a crucial requirement for the response to various immunotherapies: Immunogenic ("hot") tumors, characterized by their T cell-infiltrated TME, respond better compared to non-immunogenic ("cold") tumors. It has been speculated that the mode-of-action of lefitolimod provides the necessary signals for activation of immune cells, their differentiation into anti-tumor effector cells and their recruitment into the TME. We investigated the effect of lefitolimod on TME, and its potency to induce synergistic anti-tumor effects when combined with immune checkpoint inhibitory antibodies (CPI) in a murine model. Indeed, we could show that treatment with single-agent lefitolimod beneficially modulated the TME, via infiltration of activated CD8+ cells and a shift in the macrophage population toward M1 phenotype. The result was a pronounced anti-tumor effect correlated with the magnitude of infiltrated immune cells and tumor-specific T cell responses. In line with this, lefitolimod led to persistent anti-tumor memory in the EMT-6 model after tumor re-challenge. This was accompanied by an increase of tumor-specific T cell responses and cross-reactivity against different tumor cells. Lefitolimod clearly augmented the limited anti-tumor effect of the CPI anti-PD1 in an A20 and anti-PD-L1 in a CT26 model. These properties of potent immune surveillance reactivation render lefitolimod an ideal candidate as therapeutic agent for immuno-oncology, e.g. improving CPI strategies.

SUBMITTER: Kapp K

PROVIDER: S-EPMC6844329 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors.

Kapp Kerstin K Volz Barbara B Oswald Detlef D Wittig Burghardt B Baumann Matthias M Schmidt Manuel M

Oncoimmunology 20190920 12

Activation of Toll-like receptor 9 (TLR9) is known to foster innate and adaptive immune responses and thus improve immune-mediated control of malignant disease. Lefitolimod is a potent TLR9 agonist without chemical modification developed for immunotherapeutic strategies. Modulation of the tumor microenvironment (TME) is a crucial requirement for the response to various immunotherapies: Immunogenic ("hot") tumors, characterized by their T cell-infiltrated TME, respond better compared to non-immun ...[more]

PMID: 31741757

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Project description:Current therapies for metastatic colorectal cancer only prolong life for approximately 2 years. A more innovative therapy that prolongs life significantly or even cures is needed. Bone marrow transplantation is a curative therapy for patients with leukemias and lymphomas. Tumor eradication in the case of transplantation of the patient’s own marrow (autologous transplantation) is based on the intensive chemotherapy and/or radiotherapy used for conditioning. Tumor eradication in the case of transplantation using the marrow of a normal donor is based on both tumor reduction from conditioning and the immune elimination of tumor cells by T cells in the donor transplant that recognize the foreign tissue antigens expressed by the tumor cells and kill these cells. The use of bone marrow transplantation to treat tumors other than leukemia and lymphoma has been limited, and studies of transplantation of the patient’s own marrow for the treatment of advanced /metastatic breast cancer have not conclusively shown benefit beyond conventional therapy. Recently, the Strober lab developed a preclinical model that effectively treated colon cancer in mice by combining immunotherapy and autologous bone marrow transplantation in order to markedly augment the anti-tumor potency of immunotherapy. They used the CT26 colon cancer as the therapeutic target either as a single subcutaneous tumor nodule, as a disseminated tumor in the lungs and peritoneum, or as a metastatic tumor in the liver depending on the route of administration of the tumor cells in BALB/c mice. Mice were vaccinated mice with established primary tumors or disseminated/ metastatic disease with irradiated tumor cells mixed with the adjuvant CpG, and found that vaccination alone had no effect on tumor growth. Similarly radiation conditioning of tumor bearing hosts followed by transplantation of bone marrow and spleen cells or purified T cells and hematopoietic stem cells from unvaccinated donors of the same strain had no effect. In contrast, radiation conditioning of mice followed by transplantation of hematopoietic and immune cells from donors of the same strain vaccinated with tumor cells and CpG cured almost all subcutaneous primary as well as disseminated and metastatic tumors in the hosts. A similar result was obtained after autologous transplantation of hematopoietic and immune cells from tumor bearing mice that had been vaccinated after tumor establishment. Investigation of tumor infiltrating cells showed that the injected donor T cells do not accumulate in the tumors unless the host has been irradiated before injection. Based on this model, we have assembled a team of Stanford University faculty members with expertise in gastrointestinal cancers, immunotherapy, radiation oncology, and bone marrow transplantation in the Departments of Medicine and Pathology to translate the preclinical findings into a Phase I safety and feasibility clinical study for the treatment of 10 patients with metastatic colorectal cancer. Resected tumor cells will be irradiated and mixed with CpG to create a vaccine. Patients will receive subcutaneous vaccination at weeks 1 and 2 after resection. Six weeks later, immune T cells and then G-CSF "mobilized" purified blood progenitor cells will be harvested from the blood and cryopreserved. If needed patients will receive chemotherapy for tumor reduction. When disease is controlled off chemotherapy, patients will receive a conditioning regimen of fludarabine (30mg/m2 daily x 3 days) followed by intensive fractionated total body irradiation. The dose of fTBI will be escalated using a 3+3 design to ensure safety and will range from 400 to 800 gray. The patient will then undergo hematopoietic and immune cell rescue. They will undergo a third vaccination within 7-14 days after transplant. Thereafter, serial monitoring of tumor burden will continue. Immune monitoring will occur before and after vaccination as well as after transplantation. Tests will include in vitro anti-tumor immune responses of T cells (proliferation, cytotoxicity, cytokine secretion etc.) to stimulation with whole tumor cells and tumor cell lysates pulsed on to antigen presenting cells, anti-tumor antibody responses, and immune reconstitution after transplantation.

Project description:PurposeRecent studies have shown that a new generation of synthetic agonist of Toll-like receptor (TLR) 9 consisting a 3'-3'-attached structure and a dCp7-deaza-dG dinucultodie shows more potent immunostimulatory effects in both mouse and human than conventional CpG oligonucleotides. Radiation therapy (RT) provides a source of tumor antigens that are released from dying, irradiated, tumor cells without causing systemic immunosuppression. We, therefore, examined effect of combining RT with a designer synthetic agonist of TLR9 on anti-tumoral immunity, primary tumor growth retardation and metastases in a murine model of lung cancer.MethodsGrouped C57BL/6 and congenic B cell deficient mice (B(-/-)) bearing footpad 3LL tumors were treated with PBS, TLR9 agonist, control oligonucelotide, RT or the combination of RT and TLR9 agonist. Immune phenotype of splenocytes and serum IFN-? and IL-10 levels were analyzed by FACS and ELISA, 24 h after treatment. Tumor growth, lung metastases and survival rate were monitored and tumor specific antibodies in serum and deposition in tumor tissue were measured by ELISA and immunofluorescence.ResultsTLR9 agonist expanded and activated B cells and plasmacytoid dendritic cells in wild-type mice and natural killer DCs (NKDCs) in B cell-deficient (B(-/-)) mice bearing ectopic Lewis lung adenocarcinoma (3LL). Combined RT with TLR9 agonist treatment inhibited 3LL tumor growth in both wild type and B(-/-) mice. A strong tumor-specific humoral immune response (titer: 1/3200) with deposition of mouse IgG auto-antibodies in tumor tissue were found in wildtype mice, whereas the number of tumor infiltrating NKDCs increased in B(-/-) mice following RT+ TLR9 agonist therapy. Furthermore, mice receiving combination therapy had fewer lung metastases and a higher survival than single treatment cohorts.ConclusionsCombination therapy with TLR9 agonist and RT induces systemic anti-tumoral humoral response, augments tumoral infiltration of NKDCs, reduces pulmonary metastases and improves survival in a murine model of 3LL cancer.

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Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors.

Publications

Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors.

Similar Datasets

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