Photodynamic immunotherapy using adu-S100-modified nanoparticles combined with icb to treat triple-negative breast cancer Free

Background Tumor immunotherapy is an important cancer treatment that stimulates or modulates the immune system to improve the intrinsic response of the host to tumors. These therapies include immune checkpoint blockade (ICB), cancer vaccines, adoptive T cell immunotherapy, etc. However, the lack of tumor-associated antigens (TAAs) in the tumor microenvironment (TME) and the low antigen presentation ability of antigen-presenting cells (APCs) limit the duration of ICB effects. The cGAS/STING pathway is a promising therapeutic target and it can upregulate innate immunity. However, immunostimulants usually induce only local immune responses at the injection sites, which may be insufficient for inhibiting distant tumor. STING agonists in combination with other immunotherapies and appropriate delivery via drug carriers might be capable of overcoming such problems. Both clinical and preclinical studies have found that photodynamic therapy (PDT) improves the adaptive immune response that triggers immunogenic cell death. PDT induces tumor cell necrosis and/or apoptosis associated with the release of endogenous danger signals and tumor-associated antigens that facilitate DC maturation and T-cell infiltration. Thus, the use of PDT that triggers immune responses, combined with nanometal–organic framework-based STING agonists delivery, may prospectively prevent tumor development. Cancer immunotherapy based on immune checkpoint blockade (ICB) relieves immunosuppression in cancer patients by reactivating cytotoxic T cells of the innate immune system.

Methods STING agonist (ADU-S100)-functionalized porphyrin-based nanoparticles (NP-AS) were prepared and their antitumor properties in terms of cell apoptosis/necrosis and immune activation in triple-negative breast cancer were evaluated. In vitro, DC2.4 cells were cultured, Ifnb and Cxcl10 relative gene expression levels were normalized to those of β-actin and calculated using the Livak method. To determine the photodynamic immune response triggered by NP-AS increased the sensitivity of 4T1 tumors to ICB therapy, BALB/c mice were injected with 4T1 cells subcutaneously in the flank region to establish a bilateral 4T1 tumor-bearing model. In the 4T1 bilateral tumor model, primary and distant tumors were established in mice, the tumor on the right flank was denoted as the primary tumor, which were then treated with saline, anti-PD-L1, NP-AS + laser, or NP-AS + laser + anti-PD-L1. NP-AS (100 μg NPs, 40 μg ADU-S100) was injected intratumorally, followed by laser irradiation (660 nm, 250 mW/cm², 5 min). Anti-PD-L1 (750 μg/kg) was administered intravenously every 3 days. Body weight and tumor size were measured every other day.

Results The mRNA levels of Ifnb and Cxcl10 in DC2.4 cells were significantly higher in the NP-AS group than ADU-S100 group at 4h. Growth of the primary tumors in the NP-AS+laser and NP-AS+laser+anti-PD-L1 groups was almost completely inhibited compared with the saline group, but that in the anti-PD-L1 group was not significantly inhibited. The NP-AS+laser+anti-PD-L1 antibody combination inhibited the growth of distant tumors more effectively than did the NP-AS+laser and anti-PD-L1 antibody treatments alone. The tumor masses were consistent with these results. Immunofluorescent staining was used to detect CD8⁺ T cells in tumor tissues. The NP-AS+laser +anti-PD-L1 antibody combination was associated with more abundant CD8⁺ T cells than were the other treatments, suggesting induction of a systemic immune response.

Conclusion In summary, an efficient ADU-S100 delivery system was developed. ADU-S100 functionalized-NP activated immune responses by enhancing the cGAS/STING pathway and PDT induced immunogenic death. When NP-AS enter cells, ADU-S100 activates the cGAS/STING pathway to increase the innate immune response. After irradiation, increased ROS levels in tumors reduce cell vitality and induce immunogenic cell death., together with ICB alleviates immunosuppression. In a TNBC bilateral mouse model, irradiated NP-AS combined with ICB inhibited local tumor growth and significantly suppressed distant tumor progression. In general, this NP system will have many applications in cancer treatment. (Acknowledgements:This study was supported by Grant from School of Public Health of Southern Medical University, China, Grant No.GW202431; Corresponding author: Hong Cao, gzhcao@smu.edu.cn).