Metronomic cancer chemotherapy has displayed the potential to ameliorate immunosuppressive tumor microenvironment (TME) and facilitate antitumor immunotherapy, but this strategy requires uninterrupted administration of low-dose chemotherapeutic agents and suffers from rapid drug clearance. Here, we developed a single-dose in situ immune stimulator storage to achieve prolonged retention and sustained release of drugs in tumor parenchyma. Importantly, this storage could initiate immune responses through photothermal therapy (PTT) and simultaneously remodel TME. In detail, the storage framework (NGOPC) with size of ~60 nm, was composed of Ala-Ala-Asn-Cys-Lys modified nano graphene oxide (NGO-PEG-pep) and 2-cyano-6-aminobenzothiazole modified NGO (NGO-PEG-CABT), and could sufficiently penetrate into deep tumor region. Once NGOPC arrived at the core field, legumain overexpressing in TME could trigger click cycloaddition reaction of NGO-PEG-pep with NGO-PEG-CABT to form network, leading to aggregation and augmented retention in tumor. Additionally, paclitaxel (PTX) that can block immunologic escape was loaded in NGOPC (NGOPC@PTX), which synergistically worked with PTT-generated antitumor immunity. We found that NGOPC@PTX possessed the superior ability to accumulate in tumor and generate antitumor immunological efficacy by improving immune factors: induction of HSP70-mediated immunogenic cell death, reduction of regulatory T cells, and activation of cytotoxic T lymphocyte. This in situ storage, which exhibited excellent tumor growth inhibition effect and prolonged lifespan in combination with PTT, displays the potential for intensified cancer immunotherapy.
Keywords: Cancer immunotherapy; In situ; Metronomic chemotherapy; Photothermal therapy; Tumor microenvironment.
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