Combination of a STING Agonist and Photothermal Therapy Using Chitosan Hydrogels for Cancer Immunotherapy

A polymeric nanoplatform enhances the cGAS-STING pathway in macrophages to potentiate phagocytosis for cancer immunotherapy

Immunosuppressive tumor-associated macrophages (TAMs) account for a high proportion of the tumor tissue and significantly impede immunoefficacy. Furthermore, the signal regulatory protein α (SIRPα) expressed in TAMs adversely correlates with macrophage activation and phagocytosis, resulting in immunosurveillance escape. To address these difficulties, a mannose-modified, pH-responsive nanoplatform with resiquimod (R848) and 2', 3'-cyclic GMP-AMP (cGAMP) co-encapsulation (named M-PNP@R@C) is designed to polarize TAMs and lower SIRPα expression. The co-delivery of R848 and cGAMP synergistically facilitates the polarization of TAMs from the anti-inflammatory M2 phenotype into the pro-inflammatory M1 phenotype, thereby enhancing antitumor immunotherapy. Remarkably, activation of the cGAMP-mediated stimulator of interferon genes (STING) in TAMs significantly downregulates the expression of SIRPα, which synergizes with the cluster of differentiation 47 (CD47) antibody for the dual blockade of the CD47-SIRPα axis. Further analysis of single-cell RNA sequencing indicates that STING activation downregulates SIRPα by regulating intracellular fatty acid oxidation metabolism. In vivo studies indicate that M-PNP@R@C significantly inhibits tumor growth with a potent antitumor immune response in melanoma graft tumor models. After synergy with anti-CD47, the double blockade strategies of the SIRPα/CD47 axis result in a notable inhibition of lung metastasis. A prolonged survival rate is observed after combination treatment with CD47 and programmed death ligand-1 antibodies for the triple immune checkpoint blockade. In summary, our study provides original insights into the potential role of the STING pathway in macrophage-based immunotherapy, thus offering a potential combinatorial strategy for cancer therapy.

Lipo/TK-CDN/TPP/Y6 nanoparticles inhibit cutaneous melanoma formation

Stimulation of the innate immune stimulator of interferon genes (STING) pathway has been shown to boost anti-tumour immunity. Nevertheless, the systemic delivery of STING agonists to the tumour presents challenges. Therefore, we designed a cyclic dinucleotide (CDN)-based drug delivery system (DDS) combined photothermal therapy (PTT)/photodynamic therapy (PDT)/immunotherapy for cutaneous melanoma. We coencapsulated a reactive oxygen species (ROS)-responsive prodrug thioketone-linked CDN (TK-CDN), and photoresponsive agents chlorin E6 (Y6) within mitochondria-targeting reagent triphenylphosphonium (TPP)-modified liposomes (Lipo/TK-CDN/TPP/Y6). Lipo/TK-CDN/TPP/Y6 exhibited a photothermal effect similar to Y6, along with a superior cellular uptake rate. Upon endocytosis by B16F10 cells, Lipo/TK-CDN/TPP/Y6 generated large amounts of ROS under laser irradiation for PDT. Mice bearing B16F10 tumours were intravenously injected with Lipo/TK-CDN/TPP/Y6 and exposed to irradiation, resulting in a substantial inhibition of tumour growth. Exploration of the mechanism of anti-tumour action showed that Lipo/TK-CDN/TPP/Y6 had a stronger stimulation of STING activation and anti-tumour immune cell infiltration compared to other groups. Hence, the Lipo/TK-CDN/TPP/Y6 nanoparticles offer great potential as a DDS for targeted and on-demand drug release at tumour sites. These nanoparticles exhibit promise as a candidate for precise and controllable combination therapy in the treatment of tumours.

Recent Progress in Photothermal, Photodynamic and Sonodynamic Cancer Therapy: Through the cGAS-STING Pathway to Efficacy-Enhancing Strategies

Photothermal, photodynamic and sonodynamic cancer therapies offer opportunities for precise tumor ablation and reduce side effects. The cyclic guanylate adenylate synthase-stimulator of interferon genes (cGAS-STING) pathway has been considered a potential target to stimulate the immune system in patients and achieve a sustained immune response. Combining photothermal, photodynamic and sonodynamic therapies with cGAS-STING agonists represents a newly developed cancer treatment demonstrating noticeable innovation in its impact on the immune system. Recent reviews have concentrated on diverse materials and their function in cancer therapy. In this review, we focus on the molecular mechanism of photothermal, photodynamic and sonodynamic cancer therapies and the connected role of cGAS-STING agonists in treating cancer.

Chitosan- and hyaluronic acid-based nanoarchitectures in phototherapy: Combination cancer chemotherapy, immunotherapy and gene therapy

Cancer phototherapy has been introduced as a new potential modality for tumor suppression. However, the efficacy of phototherapy has been limited due to a lack of targeted delivery of photosensitizers. Therefore, the application of biocompatible and multifunctional nanoparticles in phototherapy is appreciated. Chitosan (CS) as a cationic polymer and hyaluronic acid (HA) as a CD44-targeting agent are two widely utilized polymers in nanoparticle synthesis and functionalization. The current review focuses on the application of HA and CS nanostructures in cancer phototherapy. These nanocarriers can be used in phototherapy to induce hyperthermia and singlet oxygen generation for tumor ablation. CS and HA can be used for the synthesis of nanostructures, or they can functionalize other kinds of nanostructures used for phototherapy, such as gold nanorods. The HA and CS nanostructures can combine chemotherapy or immunotherapy with phototherapy to augment tumor suppression. Moreover, the CS nanostructures can be functionalized with HA for specific cancer phototherapy. The CS and HA nanostructures promote the cellular uptake of genes and photosensitizers to facilitate gene therapy and phototherapy. Such nanostructures specifically stimulate phototherapy at the tumor site, with particle toxic impacts on normal cells. Moreover, CS and HA nanostructures demonstrate high biocompatibility for further clinical applications.

Alginate-Chitosan Biodegradable and Biocompatible Based Hydrogel for Breast Cancer Immunotherapy and Diagnosis: A Comprehensive Review

Breast cancer is the most common type of cancer and the second leading cause of cancer-related mortality in females. There are many side effects due to chemotherapy and traditional surgery, like fatigue, loss of appetite, skin irritation, and drug resistance to cancer cells. Immunotherapy has become a hopeful approach toward cancer treatment, generating long-lasting immune responses in malignant tumor patients. Recently, hydrogel has received more attention toward cancer therapy due to its specific characteristics, such as decreased toxicity, fewer side effects, and better biocompatibility drug delivery to the particular tumor location. Researchers globally reported various investigations on hydrogel research for tumor diagnosis. The hydrogel-based multilayer platform with controlled nanostructure has received more attention for its antitumor effect. Chitosan and alginate play a leading role in the formation of the cross-link in a hydrogel. Also, they help in the stability of the hydrogel. This review discusses the properties, preparation, biocompatibility, and bioavailability of various research and clinical approaches of the multipolymer hydrogel made of alginate and chitosan for breast cancer treatment. With a focus on cases of breast cancer and the recovery rate, there is a need to find out the role of hydrogel in drug delivery for breast cancer treatment.

Thermo-Responsive Hydrogels Coupled with Photothermal Agents for Biomedical Applications

Intelligent hydrogels are materials with abilities to change their chemical nature or physical structure in response to external stimuli showing promising potential in multitudinous applications. Especially, photo-thermo coupled responsive hydrogels that are prepared by encapsulating photothermal agents into thermo-responsive hydrogel matrix exhibit more attractive advantages in biomedical applications owing to their spatiotemporal control and precise therapy. This work summarizes the latest progress of the photo-thermo coupled responsive hydrogel in biomedical applications. Three major elements of the photo-thermo coupled responsive hydrogel, i.e., thermo-responsive hydrogel matrix, photothermal agents, and construction methods are introduced. Furthermore, the recent developments of these hydrogels for biomedical applications are described with some selected examples. Finally, the challenges and future perspectives for photo-thermo coupled responsive hydrogels are outlined.

A sequential scheme including PTT and 2'3'-cGAMP/CQ-LP reveals the antitumor immune function of PTT through the type I interferon pathway

Photothermal therapy (PTT) is a promising antitumor treatment that is easy to implement, minimally invasive, and precisely controllable, and evokes strong antitumor immunity. We believe that a thorough elucidation of its underlying antitumor immune mechanisms would contribute to the rational design of combination treatments with other antitumor strategies and consequently potentiate clinical use. In this study, PTT using indocyanine green (ICG) induced STING-dependent type I interferon (IFN) production in macrophages (RAW264.7 and bone marrow-derived macrophages (BMDMs)), as proven by the use of a STING inhibitor (C178), and triggered STING-independent type I IFN generation in tumor cells (CT26 and 4T1), which was inhibited by DNase pretreatment. A novel liposome coloaded with the STING agonist 2'3'-cGAMP (cGAMP) and chloroquine (CQ) was constructed to achieve synergistic effect with PTT, in which CQ increased cGAMP entrapment efficiency and prevented STING degradation after IFN signaling activation. The sequential combination treatment caused a significant increase in tumor cell apoptosis, probably due to interferon stimulating gene products 15 and 54 (ISG15 and ISG 54), and achieved a more striking antitumor inhibition effect in the CT26 tumor model than the 4T1 model, likely due to higher STAT1 expression and consequently more intense IFN signal transduction. In the tumor microenvironment, the combination treatment increased infiltrating CD8+T cells (4-fold) and M1-like TAMs (10-fold), and decreased M-MDSCs (over 2-fold) and M2-like TAMs (over 4-fold). Above all, in-depth exploration of the antitumor mechanism of PTT provides guidance for selecting sensitive tumor models and designing reasonable clinical schemes.