A glucose-sensitive nanovaccine delivers CRISPR to tumors, silences immune-suppressing genes, and activates a targeted immune response against cancer.
(Nanowerk Spotlight) Immune-based cancer therapies have expanded the frontiers of oncology by harnessing the body’s own defenses to target malignant cells. Strategies such as checkpoint inhibitors and cancer vaccines have shown potential, yet many tumors remain unresponsive due to complex methods of immune evasion. One major barrier is the suppression of interferon-related pathways. Although interferons help coordinate an immune response, their activity can lead to the increased production of PD-L1, a surface protein that shuts down T cell responses.
In parallel, tumors use molecular regulators to limit the recognition of DNA fragments inside cancer cells, preventing the activation of key immune sensors like the cGAS-STING pathway. These feedback loops weaken the immune system’s ability to detect and destroy tumor cells.
An especially potent immune-suppressive factor is SMARCAL1, a chromatin remodeling protein found at high levels in several types of cancer. It plays a dual role in promoting tumor growth. First, by preserving the stability of tumor DNA, it reduces the presence of abnormal double-stranded DNA fragments in the cytoplasm, which would otherwise activate immune detection.
Second, SMARCAL1 increases the accessibility of chromatin at the PD-L1 gene site, allowing tumors to elevate PD-L1 expression and further inhibit immune responses. Targeting SMARCAL1 offers a potential route to dismantling these suppressive pathways, but doing so selectively in tumors without affecting healthy tissue presents a challenge.
Gene editing technologies such as CRISPR-Cas9 provide a way to directly shut off genes like SMARCAL1 inside tumor cells. However, this approach requires a delivery system that is both precise and responsive to the biochemical conditions within the tumor. Metal-organic frameworks, particularly zeolitic imidazolate frameworks (ZIFs), have emerged as carriers for CRISPR components.
These nanomaterials can respond to environmental triggers and release gene-editing tools at specific sites. Tumor environments offer a unique biochemical profile—especially elevated glucose levels due to their altered metabolism—that can be exploited as a trigger for such systems.
A research team at Hainan Medical University developed a glucose-responsive CRISPR nanovaccine designed to overcome immune suppression and enhance antitumor immunity. Their study, published in Advanced Science (“Advanced Cancer Immunotherapy via SMARCAL1 Blockade Using a Glucose‐Responsive CRISPR Nanovaccine”), describes a nanoparticle system that combines targeted gene editing with local immune activation.
Schematic illustration of glucose-responsive gene editing of SMARCAL1 for synergistically enhancing STING-mediated cancer immunotherapy. a) Preparation of the glucose-responsive gene editor. b) Synergistic strategy to enhance cGAS-STING signaling and PD-L1 inhibition through glucoseresponsive genome editing combined with SMARCAL1 blockade. (click on image to enlarge)
The system responds to the high glucose levels found in tumors, releasing its therapeutic payload only within the cancerous tissue. This approach enables in situ gene editing of SMARCAL1, strengthens interferon signaling via the STING pathway, and prevents the upregulation of PD-L1 that normally dampens immune responses.
The nanovaccine is built from a hybrid framework of zinc and cobalt ions assembled into a porous structure. These ZIF-based particles are loaded with two functional elements: plasmids encoding CRISPR-Cas9 machinery that targets SMARCAL1, and glucose oxidase (GOx), an enzyme that breaks down glucose. The outer layer of the nanoparticle is coated with hyaluronic acid, which binds to CD44 receptors commonly found on cancer cells. This enhances the targeting of the particles to tumor sites.
Once the nanoparticle enters a tumor cell, its glucose-sensitive components become active. GOx catalyzes the conversion of glucose into gluconic acid and hydrogen peroxide. This reaction has several consequences: it lowers the local pH, consumes oxygen, and produces reactive oxygen species (ROS). The acidic environment causes the ZIF structure to break apart, releasing the CRISPR plasmids and the embedded metal ions. The ROS and released DNA fragments further activate the STING pathway, which leads to the production of type I interferons and other immune signals.
At the same time, the CRISPR plasmid silences SMARCAL1. This gene disruption results in an increase in cytosolic DNA fragments, which would otherwise be prevented by SMARCAL1’s genome-stabilizing role. These DNA fragments act as natural activators of the cGAS-STING immune signaling cascade. The elimination of SMARCAL1 also reduces PD-L1 expression by interfering with its transcriptional regulation. This combination allows immune cells to remain active and recognize the tumor more effectively.
In cell culture experiments, the system was shown to be highly dependent on glucose concentration. Tumor cells treated with the nanovaccine in the presence of glucose exhibited reduced SMARCAL1 expression, higher levels of cGAS and interferon signaling, and lower levels of PD-L1. The editing of SMARCAL1 was confirmed using molecular assays, which showed a higher frequency of gene disruption when glucose was present. These findings indicate that the system is selectively activated within tumor environments.
The nanoparticles also performed key metabolic functions. They consumed glucose, leading to a starvation effect in tumor cells, and generated ROS through a series of enzyme-driven reactions. These effects were measured using standard biochemical assays, which confirmed that the particles maintained enzymatic activity and selectively decomposed under acidic conditions. The release of zinc and cobalt ions further enhanced the activation of STING signaling pathways, as these ions play a known role in promoting the immune response to cytosolic DNA.
To evaluate therapeutic potential, the researchers tested the nanovaccine on three-dimensional tumor spheroids made from breast cancer cells. These structures mimic the density and microenvironment of real tumors. The treated spheroids showed significant shrinkage over twelve days, particularly when glucose was present. Tumor cells exhibited markers of cell death, including apoptosis and membrane damage. Cell viability assays confirmed that the cytotoxic effects of the treatment were glucose-dependent and more pronounced than those seen with control particles lacking either the enzyme or the CRISPR plasmid.
The immune effects of the treatment were also investigated. When dendritic cells were exposed to tumor cells treated with the nanovaccine, they released higher levels of immune-stimulating molecules such as TNF-α, IL-6, and type I interferons. The treatment also increased the amount of double-stranded DNA and HMGB1 in the tumor environment, both of which are associated with immunogenic cell death and the activation of dendritic cells. Flow cytometry analysis showed increased expression of maturation markers on these immune cells, indicating that the treatment successfully primed the immune system for a response.
In animal studies using mice with breast cancer tumors, the nanovaccine accumulated preferentially in tumor tissues and showed minimal toxicity in healthy organs. Blood chemistry and histological analyses confirmed the biocompatibility of the nanoparticles. Treated mice experienced slower tumor growth, lower tumor weights, and increased survival compared to control groups. After 35 days, 60% of the mice that received the glucose-responsive treatment were still alive, whereas all control animals had died. Tissue samples showed reduced SMARCAL1 expression and increased cGAS signaling, consistent with the intended mechanism of action.
The treatment also altered the tumor immune landscape. Dendritic cells in the lymph nodes of treated mice showed signs of activation. Tumors displayed increased infiltration by both CD4+ helper T cells and CD8+ cytotoxic T cells. These immune cells play critical roles in identifying and killing cancer cells, and their increased presence suggests that the treatment induced a systemic immune response beyond the local tumor site.
This study demonstrates a strategy that integrates metabolic targeting, gene editing, and immune modulation into a unified therapeutic system. By using the tumor’s elevated glucose levels as a biochemical trigger, the nanovaccine activates only in the cancer microenvironment, minimizing off-target effects. The combination of CRISPR-based gene silencing with enzyme-driven ROS generation and immune signaling offers a multi-pronged approach to overcoming tumor immune suppression.
Although the results are limited to cell cultures and mouse models, the findings suggest that bioresponsive nanocarriers may offer a way to deliver gene-editing therapies in a controlled and targeted manner. The system’s ability to silence genes, modulate immune checkpoints, and enhance innate immune signaling provides a foundation for further development in cancer immunotherapy.
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