Intravenous delivery of STING agonists using acid-sensitive polycationic polymer-modified lipid nanoparticles for enhanced tumor immunotherapy

Acid-Unlocked Two-Layer Ca-Loaded Nanoplatform to Interfere With Mitochondria for Synergistic Tumor Therapy

Background

The development of selective formulations able to target and kill tumor cells without the application of external energy has shown great promise for anti-tumor therapy.

Methods

Here, we report a "nanobomb" that explosively increases Ca content within cells. It can selectively release Ca2+ and generate H2O2 in the tumor microenvironment (TME) by acid-triggered degradation of the two-layer protective shell (ie, unlocking the "double-lock"). This material, termed CaO2@ZIF8:CUR@PAA, comprises a CaO2 core coated with the ZIF-8 framework, which was then loaded with curcumin (CUR) and coated again with polyacrylic acid (PAA).

Results

Under the slightly acidic conditions of the TME, the PAA shell (first lock) breaks down first exposing CaO2@ZIF8 and CUR inside the cell. Then, ZIF8 (second lock) is degraded in response to acid to deposit Ca2+, and H2O2. CUR can promote the release of Ca2+ from the endoplasmic reticulum to the cytoplasm, inhibit the outflow of Ca2+, and accumulates a large amount of Ca2+ intracellularly together with exogenous Ca2+ (calcium storms). The powerful calcium storm that causes mitochondrial dysfunction. The presence of a large amount of exogenous H2O2 causes further oxidative damage to tumor cell membranes and mitochondria where intracellular ROS production far exceeds clearance. CaO2@ZIF8:CUR@PAA NPs can induce cell S cycle arrest and apoptosis to inhibit tumor multiplication and growth. Oxidative damage-triggered immunogenic cell death (ICD) in turn leads to the polarization of macrophages to the M1 phenotype, inducing immunogenic cell death and inhibiting tumor cell proliferation and metastasis.

Discussion

The acid two-step unlocking nanoplatform is a therapeutic modality that combines calcium storm and oxidative damage. The mode triggers apoptosis leading to ICD of tumor cells. The material induces cycle blockade during treatment to inhibit cell proliferation. Robust in vitro and in vivo data demonstrate the efficacy of this approach and CaO2@ZIF8:CUR@PAA as an anticancer platform, paving the way for nanomaterials in immune-triggered cancer therapy.

Nanocarrier-mediated modulation of cGAS-STING signaling pathway to disrupt tumor microenvironment

The cGAS-STING signaling plays an important role in the immune response in a tumor microenvironment (TME) of triple-negative breast cancer (TNBC). The acute and controlled activation of cGAS-STING signaling results in tumor suppression, while chronic activation of cGAS-STING signaling results in immune-suppressive TME that could result in tumor survival. There is a need, therefore, to develop therapeutic strategies for harnessing tumor suppressive effects of cGAS-STING signaling while minimizing the risks associated with chronic activation. Combination therapies and nanocarriers-based delivery of cGAS-STING agonists have emerged as promising strategies in immunotherapy for controlled modulation of cGAS-STING signaling in cancer. These approaches aim to optimize the tumor suppressive effects of the cGAS-STING pathway while minimizing the challenges associated with modulators of cGAS-STING signaling. In the present review, we discuss recent advancements and strategies in combination therapies and nanocarrier-based delivery systems for effectively controlling cGAS-STING signaling in cancer immunotherapy. Further, we emphasized the significance of nanocarrier-based approaches for effective targeting of the cGAS-STING signaling, tackling resistance mechanisms, and overcoming key challenges like immune suppression, tumor heterogeneity, and off-target effects.