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Immunostimulatory TLR7 agonist-nanoparticles together with checkpoint blockade for effective cancer immunotherapy.

ABSTRACT: Mono- or dual-checkpoint inhibitors for immunotherapy have changed the paradigm of cancer care; however, only a minority of patients responds to such treatment. Combining small molecule immuno-stimulators can improve treatment efficacy, but they are restricted by poor pharmacokinetics. In this study, TLR7 agonists conjugated onto silica nanoparticles showed extended drug localization after intratumoral injection. The nanoparticle-based TLR7 agonist increased immune stimulation by activating the TLR7 signaling pathway. When treating CT26 colon cancer, nanoparticle conjugated TLR7 agonists increased T cell infiltration into the tumors by > 4× and upregulated expression of the interferon γ gene compared to its unconjugated counterpart by ~2×. Toxicity assays established that the conjugated TLR7 agonist is a safe agent at the effective dose. When combined with checkpoint inhibitors that target programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), a 10-100× increase in immune cell migration was observed; furthermore, 100 mm³ tumors were treated and a 60% remission rate was observed including remission at contralateral non-injected tumors. The data show that nanoparticle based TLR7 agonists are safe and can potentiate the effectiveness of checkpoint inhibitors in immunotherapy resistant tumor models and promote a long-term specific memory immune function.

SUBMITTER: Huang CH

PROVIDER: S-EPMC7904104 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Checkpoint blockade-based immunotherapy has shown unprecedented effect in cancer treatments, but its clinical implementation has been restricted by the low host antitumor response rate. Recently, chemotherapy is well recognized to activate the immune system during some chemotherapeutics-mediated tumor eradication. The enhancement of immune response during chemotherapy might further improve the therapeutic efficiency through the synergetic mechanism. Herein, a synergistic antitumor platform (designated as BMS/RA@CC-Liposome) was constructed by utilizing CT26 cancer-cell-biomimetic nanoparticles that combined chemotherapeutic drug (RA-V) and PD-1/PD-L1 blockade inhibitor (BMS-202) to remarkably enhance antitumor immunity. In this study, the cyclopeptide RA-V as chemotherapeutic drugs directly killing tumor cells and BMS-202 as anti-PD agents eliciting antitumor immune responses were co-encapsulated in a pH-sensitive nanosystem. To achieve the cell-specific targeting drug delivery, the combination therapy nanosystem was functionalized with cancer cell membrane camouflage. The biomimetic drug delivery system perfectly disguised as endogenous substances, and realized elongated blood circulation due to anti-phagocytosis capability. Moreover, the BMS/RA@CC-Liposome also achieved the selective targeting of CT26 cells by taking advantage of the inherent homologous adhesion property of tumor cells. The in vitro and in vivo experiments revealed that the BMS/RA@CC-Liposome realized PD-1/PD-L1 blockade-induced immune response, RA-V-induced PD-L1 down-regulation and apoptosis in cancer cells. Such a system combining the advantages of chemotherapy and checkpoint blockade-based immunotherapy to create an immunogenic tumor microenvironment systemically, demonstrated improved therapeutic efficacy against hypoxic tumor cells and offers an alternative strategy based on the immunology of the PD-1/PD-L1 pathway. Graphical abstract CT26 cancer-cell-biomimetic nanoparticles (BMS/RA@CC-Liposome) sensitized hypoxia tumor to checkpoint blockade-based immunotherapy in virtue of the synergistic effects between RA-V and BMS on PD-1/PD-L1 axis.Image 1

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Immunostimulatory TLR7 agonist-nanoparticles together with checkpoint blockade for effective cancer immunotherapy.

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