All-in-one glycol chitosan nanoparticles for co-delivery of doxorubicin and anti-PD-L1 peptide in cancer immunotherapy

Bio-orthogonal click chemistry strategy for PD-L1-targeted imaging and pyroptosis-mediated chemo-immunotherapy of triple-negative breast cancer

BACKGROUND

The combination of programmed cell death ligand-1 (PD-L1) immune checkpoint blockade (ICB) and immunogenic cell death (ICD)-inducing chemotherapy has shown promise in cancer immunotherapy. However, triple-negative breast cancer (TNBC) patients undergoing this treatment often face obstacles such as systemic toxicity and low response rates, primarily attributed to the immunosuppressive tumor microenvironment (TME).

METHODS AND RESULTS

In this study, PD-L1-targeted theranostic systems were developed utilizing anti-PD-L1 peptide (APP) conjugated with a bio-orthogonal click chemistry group. Initially, TNBC was treated with azide-modified sugar to introduce azide groups onto tumor cell surfaces through metabolic glycoengineering. A PD-L1-targeted probe was developed to evaluate the PD-L1 status of TNBC using magnetic resonance/near-infrared fluorescence imaging. Subsequently, an acidic pH-responsive prodrug was employed to enhance tumor accumulation via bio-orthogonal click chemistry, which enhances PD-L1-targeted ICB, the pH-responsive DOX release and induction of pyroptosis-mediated ICD of TNBC. Combined PD-L1-targeted chemo-immunotherapy effectively reversed the immune-tolerant TME and elicited robust tumor-specific immune responses, resulting in significant inhibition of tumor progression.

CONCLUSIONS

Our study has successfully engineered a bio-orthogonal multifunctional theranostic system, which employs bio-orthogonal click chemistry in conjunction with a PD-L1 targeting strategy. This innovative approach has been demonstrated to exhibit significant promise for both the targeted imaging and therapeutic intervention of TNBC.

Design of PD-L1-Targeted Lipid Nanoparticles to Turn on PTEN for Efficient Cancer Therapy

Lipid nanoparticles (LNPs) exhibit remarkable mRNA delivery efficiency, yet their majority accumulate in the liver or spleen after injection. Tissue-specific mRNA delivery can be achieved through modulating LNP properties, such as tuning PEGylation or varying lipid components systematically. In this paper, a streamlined method is used for incorporating tumor-targeting peptides into the LNPs; the programmed death ligand 1 (PD-L1) binding peptides are conjugated to PEGylated lipids via a copper-free click reaction, and directly incorporated into the LNP composition (Pep LNPs). Notably, Pep LNPs display robust interaction with PD-L1 proteins, which leads to the uptake of LNPs into PD-L1 overexpressing cancer cells both in vitro and in vivo. To evaluate anticancer immunotherapy mediated by restoring tumor suppressor, mRNA encoding phosphatase and tensin homolog (PTEN) is delivered via Pep LNPs to PTEN-deficient triple-negative breast cancers (TNBCs). Pep LNPs loaded with PTEN mRNA specifically promotes autophagy-mediated immunogenic cell death in 4T1 tumors, resulting in effective anticancer immune responses. This study highlights the potential of tumor-targeted LNPs for mRNA-based cancer therapy.

Nanoparticles in tumor microenvironment remodeling and cancer immunotherapy

Cancer immunotherapy and vaccine development have significantly improved the fight against cancers. Despite these advancements, challenges remain, particularly in the clinical delivery of immunomodulatory compounds. The tumor microenvironment (TME), comprising macrophages, fibroblasts, and immune cells, plays a crucial role in immune response modulation. Nanoparticles, engineered to reshape the TME, have shown promising results in enhancing immunotherapy by facilitating targeted delivery and immune modulation. These nanoparticles can suppress fibroblast activation, promote M1 macrophage polarization, aid dendritic cell maturation, and encourage T cell infiltration. Biomimetic nanoparticles further enhance immunotherapy by increasing the internalization of immunomodulatory agents in immune cells such as dendritic cells. Moreover, exosomes, whether naturally secreted by cells in the body or bioengineered, have been explored to regulate the TME and immune-related cells to affect cancer immunotherapy. Stimuli-responsive nanocarriers, activated by pH, redox, and light conditions, exhibit the potential to accelerate immunotherapy. The co-application of nanoparticles with immune checkpoint inhibitors is an emerging strategy to boost anti-tumor immunity. With their ability to induce long-term immunity, nanoarchitectures are promising structures in vaccine development. This review underscores the critical role of nanoparticles in overcoming current challenges and driving the advancement of cancer immunotherapy and TME modification.

Designing Peptide-Based Nanoinhibitors of Programmed Cell Death Ligand 1 (PD-L1) for Enhanced Chemo-immunotherapy

The combination of immune checkpoint blockade (ICB) and chemotherapy has shown significant potential in the clinical treatment of various cancers. However, circulating regeneration of PD-L1 within tumor cells greatly limits the efficiency of chemo-immunotherapy and consequent patient response rates. Herein, we report the synthesis of a nanoparticle-based PD-L1 inhibitor (FRS) with a rational design for effective endogenous PD-L1 suppression. The nanoinhibitor is achieved through self-assembly of fluoroalkylated competitive peptides that target PD-L1 palmitoylation. The FRS nanoparticles provide efficient protection and delivery of functional peptides to the cytoplasm of tumors, showing greater inhibition of PD-L1 than nonfluorinated peptidic inhibitors. Moreover, we demonstrate that FRS synergizes with chemotherapeutic doxorubicin (DOX) to boost the antitumor activities via simultaneous reduction of PD-L1 abundance and induction of immunogenic cell death in murine colon tumor models. The nano strategy of PD-L1 regulation present in this study is expected to advance the development of ICB inhibitors and overcome the limitations of conventional ICB-assisted chemo-immunotherapy.

Multifunctional Tumor-Targeting Carbon Dots for Tumor Microenvironment Activated Ferroptosis and Immunotherapy in Cancer Treatment

As an emerging cancer treatment strategy, ferroptosis is distinguished by the perturbation of lipid metabolism equilibrium and the accumulation of lipid peroxidation. However, the efficacy is consistently hindered by excessive GSH in the tumor microenvironment (TME). Here, this work designed and prepared multifunctional tumor-targeting carbon dots (FG-CDs@Cu) for ferroptosis and immunotherapy. Cu2+ in FG-CDs@Cu rapidly depletes high concentrations of GSH and inhibits glutathione peroxidase 4 (GPX4) expression in an acidic TME. Meanwhile, the generated Cu+ produced reactive oxygen species (ROS) through Fenton-like reaction. Due to the high efficiency of ROS production and GSH depletion, ferroptosis mediated by oxidative stress is significantly enhanced by FG-CDs@Cu in vivo, which can induce immunogenic cell death and promote CD8+ T cell infiltration. Meanwhile, the generated O2 effectively improves the hypoxic environment of the cells and leads to the reduction of hypoxia factor-1α (HIF-1α) expression, which activates the transformation of tumor-promoting M2-type tumor-associated macrophages (TAMs) to tumor-inhibiting M1-type TAMs, further enhancing the immune response and ferroptosis. The in vivo tests suggested that FG-CDs@Cu could efficiently suppress tumor growth in the mouse model and did not cause obvious toxicity. The combination with antiprogrammed death-ligand 1 (αPD-L1) synergy immune therapy could effectively restrain the growth of distal tumors, suggesting the significant potential of FG-CDs@Cu in augmenting ferroptosis and immunotherapy for efficacious cancer treatment.