Hydroxyethyl starch-based self-reinforced nanomedicine inhibits both glutathione and thioredoxin antioxidant pathways to boost reactive oxygen species-powered immunotherapy.

The adaptive antioxidant systems of tumor cells, predominantly glutathione (GSH) and thioredoxin (TRX) networks, severely impair photodynamic therapy (PDT) potency and anti-tumor immune responses. Here, a multistage redox homeostasis nanodisruptor (Phy@HES-IR), integrated by hydroxyethyl starch (HES)-new indocyanine green (IR820) conjugates with physcion (Phy), an inhibitor of the pentose phosphate pathway (PPP), is rationally designed to achieve PDT primed cancer immunotherapy. In this nanodisruptor, Phy effectively depletes intracellular GSH of tumor cells by inhibiting 6-phosphogluconate dehydrogenase (6PGD) activity. Concurrently, it is observed for the first time that the modified IR820-NH2 molecule not only exerts PDT action but also interferes with TRX antioxidant pathway by inhibiting thioredoxin oxidase (TRXR) activity. The simultaneous weakening of two major antioxidant pathways of tumor cells is favorable to maximize the PDT efficacy induced by HES-IR conjugates. By virtue of the excellent protecting ability of the plasma expander HES, Phy@HES-IR can remain stable in the blood circulation and efficiently enrich in the tumor region. Consequently, PDT and metabolic modulation synergistically induced immunogenic cell death, which not only suppressed primary tumors but also stimulated potent anti-tumor immunity to inhibit the growth of distant tumors in 4T1 tumor-bearing mice.

Hydroxyethyl starch conjugates co-assembled nanoparticles promote photodynamic therapy and antitumor immunity by inhibiting antioxidant systems.

Photodynamic therapy (PDT) can produce high levels of reactive oxygen species (ROS) to kill tumor cells and induce antitumor immunity. However, intracellular antioxidant systems, including glutathione (GSH) system and thioredoxin (Trx) system, limit the accumulation of ROS, resulting in compromised PDT and insufficient immune stimulation. Herein, we designed a nanomedicine PtHPs co-loading photosensitizer pyropheophorbide a (PPa) and cisplatin prodrug Pt-COOH(IV) (Pt (IV)) based on hydroxyethyl starch (HES) to inhibit both GSH and Trx antioxidant systems and achieve potent PDT as well as antitumor immune responses. Specifically, HES-PPa and HES-Pt were obtained by coupling HES with PPa and Pt (IV), and assembled into nanoparticle PtHPs by emulsification method to achieve the purpose of co-delivery of PPa and Pt (IV). PtHPs improved PPa photostability while retaining PPa photodynamic properties. In vitro experiments showed that PtHPs reduced GSH, inhibited Trx system and had better cell-killing effect and ROS generation ability. Subcutaneous tumor models showed that PtHPs had good safety and tumor inhibition effect. Bilateral tumor models suggested that PtHPs promoted the release of damage-associated molecular patterns and the maturation of dendritic cells, induced T cell-mediated immune responses, and thus suppressed the growth of both primary and distal tumors. This study reports a novel platinum-based nanomedicine and provides a new strategy for boosting PDT therapy-mediated antitumor immunity by overcoming intrinsic antioxidant systems.

Hyperbaric Oxygen Activates Enzyme-Driven Cascade Reactions for Cooperative Cancer Therapy and Cancer Stem Cells Elimination.

Tumor starvation induced by intratumor glucose depletion emerges as a promising strategy for anticancer therapy. However, its antitumor potencies are severely compromised by intrinsic tumor hypoxia, low delivery efficiencies, and undesired off-target toxicity. Herein, a multifunctional cascade bioreactor (HCG), based on the self-assembly of pH-responsive hydroxyethyl starch prodrugs, copper ions, and glucose oxidase (GOD), is engineered, empowered by hyperbaric oxygen (HBO) for efficient cooperative therapy against aggressive breast cancers. Once internalized by tumor cells, HCG undergoes disassembly and releases cargoes in response to acidic tumor microenvironment. Subsequently, HBO activates GOD-catalyzed oxidation of glucose to H2 O2 and gluconic acid by ameliorating tumor hypoxia, fueling copper-catalyzed •OH generation and pH-responsive drug release. Meanwhile, HBO degrades dense tumor extracellular matrix, promoting tumor accumulation and penetration of HCG. Moreover, along with the consumption of glucose and the redox reaction of copper ions, the antioxidant capacity of tumor cells is markedly reduced, collectively boosting oxidative stress. As a result, the combination of HCG and HBO can not only remarkably suppress the growth of orthotopic breast tumors but also restrain pulmonary metastases by inhibiting cancer stem cells. Considering the clinical accessibility of HBO, this combined strategy holds significant translational potentials for GOD-based therapies.

A two-pronged strategy to alleviate tumor hypoxia and potentiate photodynamic therapy by mild hyperthermia.

The application of photodynamic therapy (PDT) is limited by tumor hypoxia. To overcome hypoxia, catalase-like nanozymes are often used to catalyze endogenous H2O2 enriched in tumor tissues to O2. Nonetheless, the catalase activity may not be optimal at body temperature and the O2 supply may not meet the rapid O2 consumption of PDT. Herein, we provide a two-pronged strategy to alleviate tumor hypoxia based on hollow mesoporous Prussian blue nanoparticles (HMPB NPs). HMPB NPs can efficiently load the photosensitizer chlorin e6 (Ce6) and exhibit photothermal capability and temperature-dependent catalase activity. Under 808 nm laser irradiation, the photothermal effect of HMPB NPs elevated the catalase activity of HMPB NPs for O2 production. Furthermore, mild hyperthermia reduced cancer associated fibroblasts (CAFs) and induced extracellular matrix (ECM) degradation. The reduction of CAFs and the ECM decreased the solid stress of tumor tissues and normalized the tumor vasculature, which was beneficial for the external supplementation of O2 to tumors. Thereafter, under 606 nm laser irradiation, Ce6-mediated PDT generated excessive reactive oxygen species (ROS) that induced tumor cell apoptosis and achieved a high tumor inhibition rate of 92.2% in 4T1 breast tumors. Our work indicated that the alleviation of tumor hypoxia from both internal and external pathways significantly enhanced Ce6-mediated PDT against breast cancers.