Radiotherapy Combined with Novel STING-Targeting Oligonucleotides Results in Regression of Established Tumors

Cytosolic nucleic acid sensors and interferon beta-1 activation drive radiation-induced anti-tumour immune effects in human pancreatic cancer cells

Introduction

Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer-related deaths worldwide with limited treatment options due to extensive radiation and chemotherapy resistance. Monotherapy with immune checkpoint blockade showed no survival benefit. A combination of immunomodulation and radiotherapy may offer new treatment strategies, as demonstrated for non-small cell lung cancer. Radiation-induced anti-tumour immunity is mediated through cytosolic nucleic acid sensing pathways that drive the expression of interferon beta-1 (IFNB1) and proinflammatory cytokines.

Methods

Human PDAC cell lines (PANC-1, MIA PaCa-2, BxPC-3) were treated with X-rays and protons. Immunogenic cell death was measured based on HMGB1 release. Cytosolic dsDNA and dsRNA were analysed by immunofluorescence microscopy. Cell cycle progression, MHC-I and PD-L1 expression were determined by flow cytometry. Galectin-1 and IFNB1 were measured by ELISA. The expression levels and the phosphorylation status of the cGAS/STING and RIG-I/MAVS signalling pathways were analysed by western blotting, the expression of IFNB1 and proinflammatory cytokines was determined by RT-qPCR and genome-wide by RNA-seq. CRISPR-Cas9 knock-outs and inhibitors were used to elucidate the relevance of STING, MAVS and NF-κB for radiation-induced IFNB1 activation.

Results

We demonstrate that a clinically relevant X-ray hypofractionation regimen (3x8 Gy) induces immunogenic cell death and activates IFNB1 and proinflammatory cytokines. Fractionated radiation induces G2/M arrest and accumulation of cytosolic DNA in PDAC cells, which partly originates from mitochondria. RNA-seq analysis shows a global upregulation of type I interferon response and NF-κB signalling in PDAC cells following 3x8 Gy. Radiation-induced immunogenic response is regulated by STING, MAVS and NF-κB. In addition to immunostimulation, radiation also induces immunosuppressive galectin-1. No significant changes in MHC-I or PD-L1 expression were observed. Moreover, PDAC cell lines show similar radiation-induced immune effects when exposed to single-dose protons or photons.

Conclusion

Our findings provide a rationale for combinatorial radiation-immunomodulatory treatment approaches in PDAC using conventional photon-based or proton beam radiotherapy.

The effects of cGAS-STING inhibition in liver disease, kidney disease, and cellular senescence

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is one of the fundamental mechanisms of the body's defense, which responds to the abnormal presence of double-stranded DNA in the cytoplasm to establish an effective natural immune response. In addition to detecting microbial infections, the cGAS pathway may be triggered by any cytoplasmic DNA, which is absent from the normal cytoplasm, and only conditions such as senescence and mitochondrial stress can lead to its leakage and cause sterile inflammation. A growing body of research has shown that the cGAS-STING pathway is strongly associated with sterile inflammation. In this study, we reviewed the regulatory mechanisms and biological functions of the cGAS-STING pathway through its involvement in aseptic inflammation in liver disease, kidney disease, and cellular senescence.

Tumor-derived nanovesicles enhance cancer synergistic chemo-immunotherapy by promoting cGAS/STING pathway activation and immunogenetic cell death

AIMS

Checkpoint blockade immunotherapy is a promising therapeutic modality that has revolutionized cancer treatment; however, the therapy is only effective on a fraction of patients due to the tumor environment. In tumor immunotherapy, the cGAS-STING pathway is a crucial intracellular immune response pathway. Therefore, this study aimed to develop an immunotherapy strategy based on the cGAS-STING pathway.

MATERIALS AND METHODS

The physicochemical properties of the nanoparticles EM@REV@DOX were characterized by TEM, DLS, and WB. Subcutaneous LLC xenograft tumors were used to determine the biodistribution, antitumor efficacy, and immune response. Blood samples and tissues of interest were harvested for hematological analysis and H&E staining.

SIGNIFICANCE

Overall, our designed nanovesicles provide a new perspective on tumor immunotherapy by ICD and cGAS-STING pathway, promoting DCs maturation, macrophage polarization, and activating T cells, offering a meaningful strategy for accelerating the clinical development of immunotherapy.

KEY FINDINGS

EM@REV@DOX accumulated in the tumor site through EPR and homing targeting effect to release REV and DOX, resulting in DNA damage and finally activating the cGAS-STING pathway, thereby promoting DCs maturation, macrophage polarization, and activating T cells. Additionally, EM@REV@DOX increased the production of pro-inflammatory cytokines (e.g., TNF-α and IFN-β). As a result, EM@REV@DOX was effective in treating tumor-bearing mice and prolonged their lifespans. When combined with αPD-L1, EM@REV@DOX significantly inhibited distant tumor growth, extended the survival of mice, and prevented long-term postoperative tumor metastasis, exhibiting great potential in antitumor immunotherapy.

Evaluation of the Immunomodulatory Effects of Radiation for Chimeric Antigen Receptor T Cell Therapy in Glioblastoma Multiforme

Standard-of-care treatment for Glioblastoma Multiforme (GBM) is comprised of surgery and adjuvant chemoradiation. Chimeric Antigen Receptor (CAR) T cell therapy has demonstrated disease-modifying activity in GBM and holds great promise. Radiation, a standard-of-care treatment for GBM, has well-known immunomodulatory properties and may overcome the immunosuppressive tumor microenvironment (TME); however, radiation dose optimization and integration with CAR T cell therapy is not well defined. Murine immunocompetent models of GBM were treated with titrated doses of stereotactic radiosurgery (SRS) of 5, 10, and 20 Gray (Gy), and the TME was analyzed using Nanostring. A conditioning dose of 10 Gy was determined based on tumor growth kinetics and gene expression changes in the TME. We demonstrate that a conditioning dose of 10 Gy activates innate and adaptive immune cells in the TME. Mice treated with 10 Gy in combination with mCAR T cells demonstrated enhanced antitumor activity and superior memory responses to rechallenge with IL13Rα2-positive tumors. Furthermore, 10 Gy plus mCAR T cells also protected against IL13Rα2-negative tumors through a mechanism that was, in part, c-GAS-STING pathway-dependent. Together, these findings support combination conditioning with low-dose 10 Gy radiation in combination with mCAR T cells as a therapeutic strategy for GBM.

The STING agonist IMSA101 enhances chimeric antigen receptor T cell function by inducing IL-18 secretion

As a strategy to improve the therapeutic success of chimeric antigen receptor T cells (CART) directed against solid tumors, we here test the combinatorial use of CART and IMSA101, a newly developed stimulator of interferon genes (STING) agonist. In two syngeneic tumor models, improved overall survival is observed when mice are treated with intratumorally administered IMSA101 in addition to intravenous CART infusion. Transcriptomic analyses of CART isolated from tumors show elevated T cell activation, as well as upregulated cytokine pathway signatures, in particular IL-18, in the combination treatment group. Also, higher levels of IL-18 in serum and tumor are detected with IMSA101 treatment. Consistent with this, the use of IL-18 receptor negative CART impair anti-tumor responses in mice receiving combination treatment. In summary, we find that IMSA101 enhances CART function which is facilitated through STING agonist-induced IL-18 secretion.

Harnessing the cGAS-STING pathway to potentiate radiation therapy: current approaches and future directions

In this review, we cover the current understanding of how radiation therapy, which uses ionizing radiation to kill cancer cells, mediates an anti-tumor immune response through the cGAS-STING pathway, and how STING agonists might potentiate this. We examine how cGAS-STING signaling mediates the release of inflammatory cytokines in response to nuclear and mitochondrial DNA entering the cytoplasm. The significance of this in the context of cancer is explored, such as in response to cell-damaging therapies and genomic instability. The contribution of the immune and non-immune cells in the tumor microenvironment is considered. This review also discusses the burgeoning understanding of STING signaling that is independent of inflammatory cytokine release and the various mechanisms by which cancer cells can evade STING signaling. We review the available data on how ionizing radiation stimulates cGAS-STING signaling as well as how STING agonists may potentiate the anti-tumor immune response induced by ionizing radiation. There is also discussion of how novel radiation modalities may affect cGAS-STING signaling. We conclude with a discussion of ongoing and planned clinical trials combining radiation therapy with STING agonists, and provide insights to consider when planning future clinical trials combining these treatments.

Roles of cGAS-STING Pathway in Radiotherapy Combined with Immunotherapy for Hepatocellular Carcinoma

Although great strides have been made in the management and treatment of hepatocellular carcinoma (HCC), its prognosis is still poor yielding a high mortality. Immunotherapy is recommended for treating advanced HCC, but its efficiency is hampered because of hepatic immunosuppression. Stimulator of interferon genes (STING) pathway, serving as a critical cytoplasmic DNA-sensing process, is reported to initiate the antitumor immune response, and link the innate immunity to the adaptive immune system. Radiotherapy has been well acknowledged to induce destruction and release of tumor-derived DNA into the cytoplasm, which then activates the cGAS-STING pathway. On this basis, radiotherapy can be used as a sensitizer for immunotherapy, and its combination with immunotherapy may bring in changes to the suboptimal efficacy of immune checkpoint inhibitor monotherapy. In this review, we summarized the roles of cGAS-STING pathway in regulation of radiotherapy combined with immunotherapy for treating HCC.

cGAS-STING, an important signaling pathway in diseases and their therapy

Since cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway was discovered in 2013, great progress has been made to elucidate the origin, function, and regulating mechanism of cGAS-STING signaling pathway in the past decade. Meanwhile, the triggering and transduction mechanisms have been continuously illuminated. cGAS-STING plays a key role in human diseases, particularly DNA-triggered inflammatory diseases, making it a potentially effective therapeutic target for inflammation-related diseases. Here, we aim to summarize the ancient origin of the cGAS-STING defense mechanism, as well as the triggers, transduction, and regulating mechanisms of the cGAS-STING. We will also focus on the important roles of cGAS-STING signal under pathological conditions, such as infections, cancers, autoimmune diseases, neurological diseases, and visceral inflammations, and review the progress in drug development targeting cGAS-STING signaling pathway. The main directions and potential obstacles in the regulating mechanism research and therapeutic drug development of the cGAS-STING signaling pathway for inflammatory diseases and cancers will be discussed. These research advancements expand our understanding of cGAS-STING, provide a theoretical basis for further exploration of the roles of cGAS-STING in diseases, and open up new strategies for targeting cGAS-STING as a promising therapeutic intervention in multiple diseases.

Radiation-targeted immunotherapy: A new perspective in cancer radiotherapy

In contemporary oncology, radiation therapy and immunotherapy stand as critical treatments, each with distinct mechanisms and outcomes. Radiation therapy, a key player in cancer management, targets cancer cells by damaging their DNA with ionizing radiation. Its effectiveness is heightened when used alongside other treatments like surgery and chemotherapy. Employing varied radiation types like X-rays, gamma rays, and proton beams, this approach aims to minimize damage to healthy tissue. However, it is not without risks, including potential damage to surrounding normal cells and side effects ranging from skin inflammation to serious long-term complications. Conversely, immunotherapy marks a revolutionary step in cancer treatment, leveraging the body's immune system to target and destroy cancer cells. It manipulates the immune system's specificity and memory, offering a versatile approach either alone or in combination with other treatments. Immunotherapy is known for its targeted action, long-lasting responses, and fewer side effects compared to traditional therapies. The interaction between radiation therapy and immunotherapy is intricate, with potential for both synergistic and antagonistic effects. Their combined use can be more effective than either treatment alone, but careful consideration of timing and sequence is essential. This review explores the impact of various radiation therapy regimens on immunotherapy, focusing on changes in the immune microenvironment, immune protein expression, and epigenetic factors, emphasizing the need for personalized treatment strategies and ongoing research to enhance the efficacy of these combined therapies in cancer care.

The Role of the Toll-like Receptor 2 and the cGAS-STING Pathways in Breast Cancer: Friends or Foes?

Breast cancer stands as a primary malignancy among women, ranking second in global cancer-related deaths. Despite treatment advancements, many patients progress to metastatic stages, posing a significant therapeutic challenge. Current therapies primarily target cancer cells, overlooking their intricate interactions with the tumor microenvironment (TME) that fuel progression and treatment resistance. Dysregulated innate immunity in breast cancer triggers chronic inflammation, fostering cancer development and therapy resistance. Innate immune pattern recognition receptors (PRRs) have emerged as crucial regulators of the immune response as well as of several immune-mediated or cancer cell-intrinsic mechanisms that either inhibit or promote tumor progression. In particular, several studies showed that the Toll-like receptor 2 (TLR2) and the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathways play a central role in breast cancer progression. In this review, we present a comprehensive overview of the role of TLR2 and STING in breast cancer, and we explore the potential to target these PRRs for drug development. This information will significantly impact the scientific discussion on the use of PRR agonists or inhibitors in cancer therapy, opening up new and promising avenues for breast cancer treatment.

Bioorthogonal Guided Activation of cGAS-STING by AIE Photosensitizer Nanoparticles for Targeted Tumor Therapy and Imaging

Photodynamic therapy (PDT) and photothermal therapy (PTT) leverage reactive oxygen species (ROS) and control local hyperthermia by photosensitizer to perturb intracellular redox equilibrium, inducing DNA damage in both mitochondria and nucleus, activating the cGAS-STING pathway, ultimately eliciting antitumor immune responses. However, current photosensitizers are encumbered by limitations such as suboptimal tumor targeting, aggregation-caused quenching (ACQ), and restricted excitation and emission wavelengths. Here, this work designs novel nanoparticles based on aggregation-induced emission (AIE) photosensitizer (BODTPE) for targeted tumor therapy and near-infrared II fluorescence imaging (NIR-II FLI) with enhanced PDT/PTT effects. BODTPE is employed as a monomer, dibenzocyclooctyne (DBCO)-PEG2k -amine serving as an end-capping polymer, to synthesize a BODTPE-containing polymer (DBD). Further, through self-assembly, DBD and mPEG-DSPE2k combined to form nanoparticles (NP-DBD). Notably, the DBCO on the surface of NP-DBD can react with azide groups on cancer cells pretreated with Ac4 ManNAz through a copper-free click reaction. This innovative formulation led to targeted accumulation of NP-DBD within tumor sites, a phenomenon convincingly demonstrated in murine tumor models subjected to N-azidoacetylmannosamine-tetraacylated (Ac4 ManNAz) pretreatment. Significantly, NP-DBD exhibits a multifaceted effect encompassing PDT/PTT/NIR-II FLI upon 808 nm laser irradiation, thereby better activating the cGAS-STING pathway, culminating in a compelling tumor inhibition effect augmented by robust immune modulation.

Chemical Biology Perspectives on STING Agonists as Tumor Immunotherapy

Stimulator of interferon genes (STING) is a crucial adaptor protein in the innate immune response. STING activation triggers cytokine secretion, including type I interferon and initiates T cell-mediated adaptive immunity. The activated immune system converts "cold tumors" into "hot tumors" that are highly responsive to T cells by recruiting them to the tumor microenvironment, ultimately leading to potent and long-lasting antitumor effects. Unlike most immune checkpoint inhibitors, STING agonists represent a groundbreaking class of innate immune agonists that hold great potential for effectively targeting various cancer populations and are poised to become a blockbuster in tumor immunotherapy. This review will focus on the correlation between the STING signaling pathway and tumor immunity, as well as explore the impact of STING activation on other biological processes. Ultimately, we will summarize the development and optimization of STING agonists from a medicinal chemistry perspective, evaluate their potential in cancer therapy, and identify possible challenges for future advancement.

At the Crossroads of the cGAS-cGAMP-STING Pathway and the DNA Damage Response: Implications for Cancer Progression and Treatment

The evolutionary conserved DNA-sensing cGAS-STING innate immunity pathway represents one of the most important cytosolic DNA-sensing systems that is activated in response to viral invasion and/or damage to the integrity of the nuclear envelope. The key outcome of this pathway is the production of interferon, which subsequently stimulates the transcription of hundreds of genes. In oncology, the situation is complex because this pathway may serve either anti- or pro-oncogenic roles, depending on context. The prevailing understanding is that when the innate immune response is activated by sensing cytosolic DNA, such as DNA released from ruptured micronuclei, it results in the production of interferon, which attracts cytotoxic cells to destroy tumors. However, in tumor cells that have adjusted to significant chromosomal instability, particularly in relapsed, treatment-resistant cancers, the cGAS-STING pathway often supports cancer progression, fostering the epithelial-to-mesenchymal transition (EMT). Here, we review this intricate pathway in terms of its association with cancer progression, giving special attention to pancreatic ductal adenocarcinoma and gliomas. As the development of new cGAS-STING-modulating small molecules and immunotherapies such as oncolytic viruses involves serious challenges, we highlight several recent fundamental discoveries, such as the proton-channeling function of STING. These discoveries may serve as guiding lights for potential pharmacological advancements.

Modulation of CD8+ T Cell Responses by Radiotherapy-Current Evidence and Rationale for Combination with Immune Checkpoint Inhibitors

Radiotherapy for cancer has been known to affect the responses of immune cells, especially those of CD8+ T cells that play a pivotal role in anti-tumor immunity. Clinical success of immune checkpoint inhibitors led to an increasing interest in the ability of radiation to modulate CD8+ T cell responses. Recent studies that carefully analyzed CD8+ T cell responses following radiotherapy suggest the beneficial roles of radiotherapy on anti-tumor immunity. In addition, numerous clinical trials to evaluate the efficacy of combining radiotherapy with immune checkpoint inhibitors are currently undergoing. In this review, we summarize the current status of knowledge regarding the changes in CD8+ T cells following radiotherapy from various preclinical and clinical studies. Furthermore, key biological mechanisms that underlie such modulation, including both direct and indirect effects, are described. Lastly, we discuss the current evidence and essential considerations for harnessing radiotherapy as a combination partner for immune checkpoint inhibitors.

Activation of STING in Response to Partial-Tumor Radiation Exposure

PURPOSE

To determine the mechanisms involved in partial volume radiation therapy (RT)-induced tumor response.

METHODS AND MATERIALS

We investigated 67NR murine orthotopic breast tumors in Balb/c mice and Lewis lung carcinoma (LLC cells; WT, Crispr/Cas9 Sting KO, and Atm KO) injected in the flank of C57Bl/6, cGAS, or STING KO mice. RT was delivered to 50% or 100% of the tumor volume using a 2 × 2 cm collimator on a microirradiator allowing precise irradiation. Tumors and blood were collected at 6, 24, and 48 hours post-RT and assessed for cytokine measurements.

RESULTS

There is a significant activation of the cGAS/STING pathway in the hemi-irradiated tumors compared with control and to 100% exposed 67NR tumors. In the LLC model, we determined that an ATM-mediated noncanonical activation of STING is involved. We demonstrated that the partial exposure RT-mediated immune response is dependent on ATM activation in the tumor cells and on the STING activation in the host, and cGAS is dispensable. Our results also indicate that partial volume RT stimulates a proinflammatory cytokine response compared with the anti-inflammatory profile induced by 100% tumor volume exposure.

CONCLUSIONS

Partial volume RT induces an antitumor response by activating STING, which stimulates a specific cytokine signature as part of the immune response. However, the mechanism of this STING activation, via the canonical cGAS/STING pathway or a noncanonical ATM-driven pathway, depends on the tumor type. Identifying the upstream pathways responsible for STING activation in the partial RT-mediated immune response in different tumor types would improve this therapy and its potential combination with immune checkpoint blockade and other antitumor therapies.

Targeting LYPLAL1-mediated cGAS depalmitoylation enhances the response to anti-tumor immunotherapy

Cyclic GMP-AMP synthase (cGAS) binds pathogenic and other cytoplasmic double-stranded DNA (dsDNA) to catalyze the synthesis of cyclic GMP-AMP (cGAMP), which serves as the secondary messenger to activate the STING pathway and innate immune responses. Emerging evidence suggests that activation of the cGAS pathway is crucial for anti-tumor immunity; however, no effective intervention method targeting cGAS is currently available. Here we report that cGAS is palmitoylated by ZDHHC9 at cysteines 404/405, which promotes the dimerization and activation of cGAS. We further identified that lysophospholipase-like 1 (LYPLAL1) depalmitoylates cGAS to compromise its normal function. As such, inhibition of LYPLAL1 significantly enhances cGAS-mediated innate immune response, elevates PD-L1 expression, and enhances anti-tumor response to PD-1 blockade. Our results therefore reveal that targeting LYPLAL1-mediated cGAS depalmitoylation contributes to cGAS activation, providing a potential strategy to augment the efficacy of anti-tumor immunotherapy.

Encapsulation of STING Agonist cGAMP with Folic Acid-Conjugated Liposomes Significantly Enhances Antitumor Pharmacodynamic Effect

Background: 2',3'-cGAMP (2',3'-cyclic AMP-GMP) has been reported as an agonist of the STING (stimulator of interferon genes) signaling pathway. However, cGAMP has poor membrane permeability and can be hydrolyzed by ectonucleotide pyrophosphatase/phosphodiesterase (ENPP1), limiting its ability to activate the STING-IRF3 pathway. This study aimed to investigate that the folate-targeted liposomal cGAMP could overcome the defects of free cGAMP to enhance the antitumor effect. Materials and Methods: cGAMP was encapsulated in PEGylated folic acid-targeted liposomes to construct a carrier-delivered formulation. The particle size and morphology were detected by dynamic light scattering and transmission electron microscopy. The sustained-release ability was measured by drug release and pharmacokinetics. Animal models were applied to evaluate the tumor inhibition efficiency in vivo. Flow cytometry, enzyme-linked immunosorbent assay, and real-time polymerase chain reaction were used to detect the expression of immune cells, secreted cytokines, and target genes. The activation of the STING-IRF3 pathway was evaluated by immunofluorescence. Results: Physical characters of liposomes revealed that the prepared liposomes were stable in neutral humoral environments and released more internal drugs in acidic tumor tissues. Systemic therapy with liposomes on Colorectal 26 tumor-bearing mice in vivo effectively inhibited tumor growth via stimulating the expression of CD8+ T cells and reversed the immunosuppressed tumor microenvironment (TME). Conclusions: The study suggests that the folic acid-targeted cGAMP-loaded liposomes deliver drugs to the TME to enhance the STING agonist activity, improving the efficiency of tumor therapy via the cGAMP-STING-IRF3 pathway.

DNA sensing in cancer: Pro-tumour and anti-tumour functions of cGAS-STING signalling

The DNA sensor cGAS (cyclic GMP-AMP synthase) and its adaptor protein STING (Stimulator of Interferon Genes) detect the presence of cytosolic DNA as a sign of infection or damage. In cancer cells, this pathway can be activated through persistent DNA damage and chromosomal instability, which results in the formation of micronuclei and the exposure of DNA fragments to the cytosol. DNA damage from radio- or chemotherapy can further activate DNA sensing responses, which may occur in the cancer cells themselves or in stromal and immune cells in the tumour microenvironment (TME). cGAS-STING signalling results in the production of type I interferons, which have been linked to immune cell infiltration in 'hot' tumours that are susceptible to immunosurveillance and immunotherapy approaches. However, recent research has highlighted the complex nature of STING signalling, with tumours having developed mechanisms to evade and hijack this signalling pathway for their own benefit. In this mini-review we will explore how cGAS-STING signalling in different cells in the TME can promote both anti-tumour and pro-tumour responses. This includes the role of type I interferons and the second messenger cGAMP in the TME, and the influence of STING signalling on local immune cell populations. We examine how alternative signalling cascades downstream of STING can promote chronic interferon signalling, the activation of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and the production of inflammatory cytokines, which can have pro-tumour functions. An in-depth understanding of DNA sensing in different cell contexts will be required to harness the anti-tumour functions of STING signalling.

Modulation of Skin Cancer by the Stimulator of Interferon Genes

Morbidity and mortality from skin cancer continue to rise domestically and globally, and melanoma and non-melanoma skin cancers are a topic of interest in the dermatology and oncology communities. In this review, we summarize the stimulator of interferon genes (STING) pathway, its specific role in the pathogenesis of DNA damage and skin cancer, and STING-specific therapies that may fight both melanoma and non-melanoma skin (NMSC) cancers. Furthermore, we discuss specific portions of the STING pathway that may be used in addition to previously used therapies to provide a synergistic effect in future oncology treatments and discuss the limitations of current STING-based therapies.

Optogenetic engineering of STING signaling allows remote immunomodulation to enhance cancer immunotherapy

The cGAS-STING signaling pathway has emerged as a promising target for immunotherapy development. Here, we introduce a light-sensitive optogenetic device for control of the cGAS/STING signaling to conditionally modulate innate immunity, called 'light-inducible SMOC-like repeats' (LiSmore). We demonstrate that photo-activated LiSmore boosts dendritic cell (DC) maturation and antigen presentation with high spatiotemporal precision. This non-invasive approach photo-sensitizes cytotoxic T lymphocytes to engage tumor antigens, leading to a sustained antitumor immune response. When combined with an immune checkpoint blocker (ICB), LiSmore improves antitumor efficacy in an immunosuppressive lung cancer model that is otherwise unresponsive to conventional ICB treatment. Additionally, LiSmore exhibits an abscopal effect by effectively suppressing tumor growth in a distal site in a bilateral mouse model of melanoma. Collectively, our findings establish the potential of targeted optogenetic activation of the STING signaling pathway for remote immunomodulation in mice.

ATM inhibition augments type I interferon response and antitumor T-cell immunity when combined with radiation therapy in murine tumor models

BACKGROUND

Radiation therapy (RT) elicits DNA double-strand breaks, resulting in tumor cytotoxicity and a type I interferon (IFN) response via stimulator of interferon genes (STING) activation. We investigated whether combining RT with an ataxia-telangiectasia mutated inhibitor promoted these effects and amplified tumor immunity.

METHODS

Mice-bearing syngeneic flank tumors (MOC2 head and neck squamous cell carcinoma or B78 melanoma) were treated with tumor-directed RT and oral administration of AZD0156. Specific immune cell depletion, type 1 interferon receptor 1 knock-out mice (IFNAR1-KO), and STING-deficient tumor cells were used to investigate tumor-immune crosstalk following RT and AZD0156 treatment.

RESULTS

Combining RT and AZD0156 reduced tumor growth compared with RT or AZD0156 alone in mice bearing MOC2 or B78 tumors. Low-dose AZD0156 (1-100 nM) alone did not affect tumor cell proliferation but suppressed tumor cell clonogenicity in combination with RT. Low-dose AZD0156 with RT synergistically increased IFN-β, major histocompatibility complex (MHC)-I, and programmed death-ligand 1 (PD-L1) expression in tumor cells. In contrast to wild-type mice, IFNAR1-KO mice showed reduced CD8+T cell tumor infiltration and poor survival following RT+AZD0156 treatment. CD8+T cell depletion reduced antitumor response during RT+AZD0156 treatment. STING-deficient MOC2 (MOC2-STING+/-) or B78 (B78-STING-/-) tumors eliminated the effects of RT+AZD0156 on the expression of IFN-β, MHC-I, and PD-L1, and reduced CD8+T cell infiltration and migration. Additional anti-PD-L1 therapy promoted antitumor response by elevation of tumor-MHC-I and lymphocyte activation.

CONCLUSIONS

Combined radiation and AZD0156 increase STING-dependent antitumor response. Tumor-derived cell-autonomous IFN-β amplification drives both MHC-I and PD-L1 induction at the tumor cell surface, which is required by anti-PD-L1 therapy to promote antitumor immune response following RT and AZD0156 combination therapy.

Significance of the cGAS-STING Pathway in Health and Disease

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a significant role in health and disease. In this pathway, cGAS, one of the major cytosolic DNA sensors in mammalian cells, regulates innate immunity and the STING-dependent production of pro-inflammatory cytokines, including type-I interferon. Moreover, the cGAS-STING pathway is integral to other cellular processes, such as cell death, cell senescence, and autophagy. Activation of the cGAS-STING pathway by "self" DNA is also attributed to various infectious diseases and autoimmune or inflammatory conditions. In addition, the cGAS-STING pathway activation functions as a link between innate and adaptive immunity, leading to the inhibition or facilitation of tumorigenesis; therefore, research targeting this pathway can provide novel clues for clinical applications to treat infectious, inflammatory, and autoimmune diseases and even cancer. In this review, we focus on the cGAS-STING pathway and its corresponding cellular and molecular mechanisms in health and disease.

Exogenous DNA enhances DUOX2 expression and function in human pancreatic cancer cells by activating the cGAS-STING signaling pathway

Pro-inflammatory cytokines upregulate the expression of the H2O2-producing NADPH oxidase dual oxidase 2 (DUOX2)2 which, when elevated, adversely affects survival from pancreatic ductal adenocarcinoma (PDAC). Because the cGAS-STING pathway is known to initiate pro-inflammatory cytokine expression following uptake of exogenous DNA, we examined whether activation of cGAS-STING could play a role in the generation of reactive oxygen species by PDAC cells. Here, we found that a variety of exogenous DNA species markedly increased the production of cGAMP, the phosphorylation of TBK1 and IRF3, and the translocation of phosphorylated IRF3 into the nucleus, leading to a significant, IRF3-dependent enhancement of DUOX2 expression, and a significant flux of H2O2 in PDAC cells. However, unlike the canonical cGAS-STING pathway, DNA-related DUOX2 upregulation was not mediated by NF-κB. Although exogenous IFN-β significantly increased Stat1/2-associated DUOX2 expression, intracellular IFN-β signaling that followed cGAMP or DNA exposure did not itself increase DUOX2 levels. Finally, DUOX2 upregulation subsequent to cGAS-STING activation was accompanied by the enhanced, normoxic expression of HIF-1α and VEGF-A as well as DNA double strand cleavage, suggesting that cGAS-STING signaling may support the development of an oxidative, pro-angiogenic microenvironment that could contribute to the inflammation-related genetic instability of pancreatic cancer.

MEK Inhibition Sensitizes Pancreatic Cancer to STING Agonism by Tumor Cell-intrinsic Amplification of Type I IFN Signaling

PURPOSE

Stimulator of interferon genes (STING) agonists are currently in development for treatment of solid tumors, including pancreatic ductal adenocarcinoma (PDAC). Response rates to STING agonists alone have been promising yet modest, and combination therapies will likely be required to elicit their full potency. We sought to identify combination therapies and mechanisms that augment the tumor cell-intrinsic effect of therapeutically relevant STING agonists apart from their known effects on tumor immunity.

EXPERIMENTAL DESIGN

We screened 430 kinase inhibitors to identify synergistic effectors of tumor cell death with diABZI, an intravenously administered and systemically available STING agonist. We deciphered the mechanisms of synergy with STING agonism that cause tumor cell death in vitro and tumor regression in vivo.

RESULTS

We found that MEK inhibitors caused the greatest synergy with diABZI and that this effect was most pronounced in cells with high STING expression. MEK inhibition enhanced the ability of STING agonism to induce type I IFN-dependent cell death in vitro and tumor regression in vivo. We parsed NFκB-dependent and NFκB-independent mechanisms that mediate STING-driven type I IFN production and show that MEK signaling inhibits this effect by suppressing NFκB activation.

CONCLUSIONS

Our results highlight the cytotoxic effects of STING agonism on PDAC cells that are independent of tumor immunity and that these therapeutic benefits of STING agonism can be synergistically enhanced by MEK inhibition.

Lipid-based nanoparticles as drug delivery systems for cancer immunotherapy

Immune checkpoint inhibitors (ICIs) have shown remarkable success in cancer treatment. However, in cancer patients without sufficient antitumor immunity, numerous data indicate that blocking the negative signals elicited by immune checkpoints is ineffective. Drugs that stimulate immune activation-related pathways are emerging as another route for improving immunotherapy. In addition, the development of nanotechnology presents a promising platform for tissue and cell type-specific delivery and improved uptake of immunomodulatory agents, ultimately leading to enhanced cancer immunotherapy and reduced side effects. In this review, we summarize and discuss the latest developments in nanoparticles (NPs) for cancer immuno-oncology therapy with a focus on lipid-based NPs (lipid-NPs), including the characteristics and advantages of various types. Using the agonists targeting stimulation of the interferon genes (STING) transmembrane protein as an exemplar, we review the potential of various lipid-NPs to augment STING agonist therapy. Furthermore, we present recent findings and underlying mechanisms on how STING pathway activation fosters antitumor immunity and regulates the tumor microenvironment and provide a summary of the distinct STING agonists in preclinical studies and clinical trials. Ultimately, we conduct a critical assessment of the obstacles and future directions in the utilization of lipid-NPs to enhance cancer immunotherapy.

Yes-Associated Protein 1 Inhibition Induces Immunogenic Cell Death and Synergizes With Radiation and PD-1 Blockade

PURPOSE

Danger signals released by ionizing radiation (IR) can theoretically stimulate immune activation in the tumor environment (TME), but IR alone is not sufficient to induce an effective immune response in clinical practice. In this study, we investigated whether inhibition of yes-associated protein 1 (YAP1) could induce immunogenic cell death (ICD) and whether the combination of YAP1 inhibition with IR could increase in vivo immune infiltration and thereby boost a tumor response to immunotherapy.

METHODS AND MATERIALS

First, the expression of ICD markers, markers of T-cell activation, and key proteins involved in innate immune signaling were measured after YAP1 inhibition. Next, the expression level of YAP1 protein was measured after different doses of IR. Then, the antitumor effect of YAP1 inhibition combined with IR was investigated in vivo, and the immune status of the TME was evaluated. Finally, the efficacy of a triple therapy including YAP1 inhibition combined with IR and programmed cell death protein 1 blockade in the treatment of resistant tumors was determined.

RESULTS

We found that YAP1 inhibition induced ICD and increased the levels of antigen presentation machinery, effectively causing the activation of T cells. Mechanistically, YAP1 inhibition induced cell DNA damage and activated the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. Surprisingly, IR upregulated YAP1 expression. IR combined with YAP1 inhibition significantly inhibited cancer growth and prolonged survival, which was related to the augmented infiltration, activation, and function of CD8+ T cells in the TME. Moreover, the addition of YAP1 inhibition significantly improved the efficacy of pancreatic cancer treatment when neither radiation nor programmed cell death protein 1 inhibitors were ideal.

CONCLUSIONS

YAP1 inhibition could trigger ICD and is a potential approach to potentiating the therapeutic efficacy of radiation therapy and anti-PD1 immunotherapy.

The immunogenic radiation and new players in immunotherapy and targeted therapy for head and neck cancer

Although treatment modalities for head and neck cancer have evolved considerably over the past decades, survival rates have plateaued. The treatment options remained limited to definitive surgery, surgery followed by fractionated radiotherapy with optional chemotherapy, and a definitive combination of fractionated radiotherapy and chemotherapy. Lately, immunotherapy has been introduced as the fourth modality of treatment, mainly administered as a single checkpoint inhibitor for recurrent or metastatic disease. While other regimens and combinations of immunotherapy and targeted therapy are being tested in clinical trials, adapting the appropriate regimens to patients and predicting their outcomes have yet to reach the clinical setting. Radiotherapy is mainly regarded as a means to target cancer cells while minimizing the unwanted peripheral effect. Radiotherapy regimens and fractionation are designed to serve this purpose, while the systemic effect of radiation on the immune response is rarely considered a factor while designing treatment. To bridge this gap, this review will highlight the effect of radiotherapy on the tumor microenvironment locally, and the immune response systemically. We will review the methodology to identify potential targets for therapy in the tumor microenvironment and the scientific basis for combining targeted therapy and radiotherapy. We will describe a current experience in preclinical models to test these combinations and propose how challenges in this realm may be faced. We will review new players in targeted therapy and their utilization to drive immunogenic response against head and neck cancer. We will outline the factors contributing to head and neck cancer heterogeneity and their effect on the response to radiotherapy. We will review in-silico methods to decipher intertumoral and intratumoral heterogeneity and how these algorithms can predict treatment outcomes. We propose that (a) the sequence of surgery, radiotherapy, chemotherapy, and targeted therapy should be designed not only to annul cancer directly, but to prime the immune response. (b) Fractionation of radiotherapy and the extent of the irradiated field should facilitate systemic immunity to develop. (c) New players in targeted therapy should be evaluated in translational studies toward clinical trials. (d) Head and neck cancer treatment should be personalized according to patients and tumor-specific factors.

Cyto-IL-15 synergizes with the STING agonist ADU-S100 to eliminate prostate tumors and confer durable immunity in mouse models

Introduction

Prostate cancer is one of the most commonly diagnosed malignancies in men with high mortality rates. Despite the recent therapeutic advances, such as immunotherapies, survival of patients with advance disease remains significantly low. Blockade of immune checkpoints has led to low response rates in these patients probably due to the immunosuppressive microenvironment and low mutation burden of prostate tumors. Combination of multiple immunotherapeutic regimes has also been unsatisfactory due to augmented adverse effects. To activate multiple immune-stimulatory pathways in the hostile prostate cancer microenvironment, we used a combination of cytotopically modified interleukin-15 (cyto-IL-15) with the stimulator of interferon genes (STING) agonist, ADU-S100.

Methods

To determine whether this combination regime could lead to both local and systemic anti-tumor effects, intratumoral administration of these agents was used in murine models of prostate cancer. Tumor growth and mouse survival were monitored, and ex vivo analyses, and RNA sequencing were performed on the tumors.

Results

Intratumorally injected ADU-S100 and cyto-IL-15 synergized to eliminate tumors in 58-67% of mice with unilateral tumors and promoted abscopal immunity in 50% of mice with bilateral tumors treated only at one side. Moreover, this combination regime offered immunoprotection against tumor rechallenge in 83% of cured mice. The efficacy of the combination treatment was associated with a strong innate and adaptive immune activation and induction of apoptotic and necrotic cell death. Cytokines, including type I and II interferons, and cytokine signalling pathways were activated, NK and T cell mediated cytotoxicity was increased, and B cells were activated both locally and systemically. While ADU-S100 led to an ulcerative pathology at the injection site, no other adverse effects were observed.

Discussion

Localised administration of a STING agonist together with cyto-IL-15 can confer significant systemic benefits and long-lasting immunity against prostate tumors while reducing immune related toxicities.

Targeted immune activation in pediatric solid tumors: opportunities to complement local control approaches

Surgery or radiation therapy is nearly universally applied for pediatric solid tumors. In many cases, in diverse tumor types, distant metastatic disease is present and evades surgery or radiation. The systemic host response to these local control modalities may lead to a suppression of antitumor immunity, with potential negative impact on the clinical outcomes for patients in this scenario. Emerging evidence suggests that the perioperative immune responses to surgery or radiation can be modulated therapeutically to preserve anti-tumor immunity, with the added benefit of preventing these local control approaches from serving as pro-tumorigenic stimuli. To realize the potential benefit of therapeutic modulation of the systemic response to surgery or radiation on distant disease that evades these modalities, a detailed knowledge of the tumor-specific immunology as well as the immune responses to surgery and radiation is imperative. In this Review we highlight the current understanding of the tumor immune microenvironment for the most common peripheral pediatric solid tumors, the immune responses to surgery and radiation, and current evidence that supports the potential use of immune activating agents in the perioperative window. Finally, we define existing knowledge gaps that limit the current translational potential of modulating perioperative immunity to achieve effective anti-tumor outcomes.

Responsive manganese-based nanoplatform amplifying cGAS-STING activation for immunotherapy

BACKGROUND

The activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) signaling pathway has attracted great attention for its ability to up-regulate innate immune response and thus enhance cancer immunotherapy. However, many STING agonists limit the further advancement of immunotherapy due to weak tumor responsiveness or low activation efficiency. The responsive and effective activation of cGAS-STING signaling in tumors is a highly challenging process.

METHODS

In this study, a manganese-based nanoplatform (MPCZ NPs) was constructed that could responsively and efficiently generate more manganese ions (Mn²⁺) and reactive oxygen species (ROS) to activate cGAS-STING signaling pathway. Briefly, manganese dioxide (MnO₂) was loaded with zinc protoporphyrin IX (ZPP) molecule and coated by polydopamine (PDA) embedded with NH₄HCO₃ to obtain MPCZ NPs. Additionally, MPCZ NPs were evaluated in vitro and in vivo for their antitumor effects by methyl thiazolyl tetrazolium (MTT) assay and TUNEL assays, respectively.

RESULTS

In this system, tumor responsiveness was achieved by exogenous (laser irradiation) and endogenous (high levels GSH) stimulation, which triggered the collapse or degradation of PDA and MnO₂. Moreover, the release of Mn²⁺ augmented the cGAS-STING signaling pathway and enhanced the conversion of hydrogen peroxide (H₂O₂) to hydroxyl radical (·OH) under NIR laser irradiation. Furthermore, the release of ZPP and the elimination of GSH by MPCZ NPs inhibited HO-1 activity and prevented ROS consumption, respectively.

CONCLUSIONS

This adopted open source and reduce expenditure strategy to effectively generate more ROS and Mn²⁺ to responsively activate cGAS-STING signaling pathway, providing a new strategy for improving immunotherapy.

Aerosolized immunotherapeutic nanoparticle inhalation potentiates PD-L1 blockade for locally advanced lung cancer

Despite therapeutic advancements, the prognosis of locally advanced non-small cell lung cancer (LANSCLC), which has invaded multiple lobes or the other lung and intrapulmonary lymph nodes, remains poor. The emergence of immunotherapy with immune checkpoint blockade (ICB) is transforming cancer treatment. However, only a fraction of lung cancer patients benefit from ICB. Significant clinical evidence suggests that the proinflammatory tumor microenvironment (TME) and programmed death-ligand 1 (PD-L1) expression correlate positively with response to the PD-1/PD-L1 blockade. We report here a liposomal nanoparticle loaded with cyclic dinucleotide and aerosolized (AeroNP-CDN) for inhalation delivery to deep-seated lung tumors and target CDN to activate stimulators of interferon (IFN) genes in macrophages and dendritic cells (DCs). Using a mouse model that recapitulates the clinical LANSCLC, we show that AeroNP-CDN efficiently mitigates the immunosuppressive TME by reprogramming tumor-associated macrophage from the M2 to M1 phenotype, activating DCs for effective tumor antigen presentation and increasing tumor-infiltrating CD8⁺ T cells for adaptive anticancer immunity. Intriguingly, activation of interferons by AeroNP-CDN also led to increased PD-L1 expression in lung tumors, which, however, set a stage for response to anti-PD-L1 treatment. Indeed, anti-PD-L1 antibody-mediated blockade of IFNs-induced immune inhibitory PD-1/PD-L1 signaling further prolonged the survival of the LANSCLC-bearing mice. Importantly, AeroNP-CDN alone or combination immunotherapy was safe without local or systemic immunotoxicity. In conclusion, this study demonstrates a potential nano-immunotherapy strategy for LANSCLC, and mechanistic insights into the evolution of adaptive immune resistance provide a rational combination immunotherapy to overcome it.

Immunomodulatory effects of targeted radionuclide therapy

It is now clear that conventional radiation therapy can reinstate cell death immunogenicity. Recent preclinical data indicate that targeted radionuclide therapy that irradiate tumors at continuous low dose rate also can elicit immunostimulatory effects and represents a promising strategy to circumvent immune checkpoint inhibitor resistance. In this perspective, we discuss the accumulating preclinical and clinical data suggesting that activation of the immune system through the cGAS-STING axis and the release of extracellular vesicles by irradiated cells, participate to this antitumor immunity. This should need to be considered for adapting clinical practices to state of the art of the radiobiology and to increase targeted radionuclide therapy effectiveness.

The role of dendritic cells in radiation-induced immune responses

Dendritic cells perform critical functions in bridging innate and adaptive immunity. Their ability to sense adjuvant signals in their environment, migrate on maturation, and cross-present cell-associated antigens enables these cells to carry antigen from tissue sites to lymph nodes, and thereby prime naïve T cells that cannot enter tissues. Despite being an infrequent cell type in tumors, we discuss how dendritic cells impact the immune environment of tumors and their response to cancer therapies. We review how radiation therapy of tumors can impact dendritic cells, through transfer of cell associated antigens to dendritic cells and the release of endogenous adjuvants, resulting in increased antigen presentation in the tumor-draining lymph nodes. We explore how tumor specific factors can result in negative regulation of dendritic cell function in the tumor, and the impact of direct radiation exposure to dendritic cells in the treatment field. These data suggest an important role for dendritic cell subpopulations in activating new T cell responses and boosting existing T cell responses to tumor associated antigens in tumor draining lymph nodes following radiation therapy. It further justifies a focus on the needs of the lymph node T cells to improve systemic anti-immunity following radiation therapy.

Radiotherapy/Chemotherapy-Immunotherapy for Cancer Management: From Mechanisms to Clinical Implications

Cancer immunotherapy has drawn much attention because it can restart the recognition and killing function of the immune system to normalize the antitumor immune response. However, the role of radiotherapy and chemotherapy in cancer treatment cannot be ignored. Due to cancer heterogeneity, combined therapy has become a new trend, and its efficacy has been confirmed in many studies. This review discussed the clinical implications and the underlying mechanisms of cancer immunotherapy in combination with radiotherapy or chemotherapy, offering an outline for clinicians as well as inspiration for future research.

Combination, Modulation and Interplay of Modern Radiotherapy with the Tumor Microenvironment and Targeted Therapies in Pancreatic Cancer: Which Candidates to Boost Radiotherapy?

Pancreatic ductal adenocarcinoma cancer (PDAC) is a highly diverse disease with low tumor immunogenicity. PDAC is also one of the deadliest solid tumor and will remain a common cause of cancer death in the future. Treatment options are limited, and tumors frequently develop resistance to current treatment modalities. Since PDAC patients do not respond well to immune checkpoint inhibitors (ICIs), novel methods for overcoming resistance are being explored. Compared to other solid tumors, the PDAC's tumor microenvironment (TME) is unique and complex and prevents systemic agents from effectively penetrating and killing tumor cells. Radiotherapy (RT) has the potential to modulate the TME (e.g., by exposing tumor-specific antigens, recruiting, and infiltrating immune cells) and, therefore, enhance the effectiveness of targeted systemic therapies. Interestingly, combining ICI with RT and/or chemotherapy has yielded promising preclinical results which were not successful when translated into clinical trials. In this context, current standards of care need to be challenged and transformed with modern treatment techniques and novel therapeutic combinations. One way to reconcile these findings is to abandon the concept that the TME is a well-compartmented population with spatial, temporal, physical, and chemical elements acting independently. This review will focus on the most interesting advancements of RT and describe the main components of the TME and their known modulation after RT in PDAC. Furthermore, we will provide a summary of current clinical data for combinations of RT/targeted therapy (tRT) and give an overview of the most promising future directions.

CD73 Inhibits cGAS-STING and Cooperates with CD39 to Promote Pancreatic Cancer

The ectonucleotidases CD39 and CD73 catalyze extracellular ATP to immunosuppressive adenosine, and as such, represent potential cancer targets. We investigated biological impacts of CD39 and CD73 in pancreatic ductal adenocarcinoma (PDAC) by studying clinical samples and experimental mouse tumors. Stromal CD39 and tumoral CD73 expression significantly associated with worse survival in human PDAC samples and abolished the favorable prognostic impact associated with the presence of tumor-infiltrating CD8+ T cells. In mouse transplanted KPC tumors, both CD39 and CD73 on myeloid cells, as well as CD73 on tumor cells, promoted polarization of infiltrating myeloid cells towards an M2-like phenotype, which enhanced tumor growth. CD39 on tumor-specific CD8+ T cells and pancreatic stellate cells also suppressed IFNγ production by T cells. Although therapeutic inhibition of CD39 or CD73 alone significantly delayed tumor growth in vivo, targeting of both ectonucleotidases exhibited markedly superior antitumor activity. CD73 expression on human and mouse PDAC tumor cells also protected against DNA damage induced by gemcitabine and irradiation. Accordingly, large-scale pharmacogenomic analyses of human PDAC cell lines revealed significant associations between CD73 expression and gemcitabine chemoresistance. Strikingly, increased DNA damage in CD73-deficient tumor cells associated with activation of the cGAS-STING pathway. Moreover, cGAS expression in mouse KPC tumor cells was required for antitumor activity of the CD73 inhibitor AB680 in vivo. Our study, thus, illuminates molecular mechanisms whereby CD73 and CD39 seemingly cooperate to promote PDAC progression.

Crosstalk between cGAS-STING pathway and autophagy in cancer immunity

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is critical in cancer immunity. Autophagy is a highly conserved process that is responsible for the degradation of cytoplasmic material and is involved in both innate and adaptive immunity. Recently, cGAS-STING and autophagy have been shown to be interconnected, which may influence the progression of cancer. Although cGAS-STING and autophagy have been shown to be interrelated in innate immunity, little has been reported about cancer immunity. As cancer immunity is key to treating tumors, it is essential to summarize the relationship and interactions between the two. Based on this, we systematically sorted out the recent findings of cGAS-STING and autophagy in cancer immunity and explored the interactions between cGAS-STING and autophagy, although these interactions have not been extensively studied. Lastly, we provide an outlook on how cGAS-STING and autophagy can be combined, with the hope that our research can help people better understand their potential roles in cancer immunity and bring light to the treatment of cancer.

The cGAS-STING pathway and cancer

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has emerged as a critical innate immune pathway that, following engagement by DNA, promotes distinct immune effector responses that can impact virtually all aspects of tumorigenesis, from malignant cell transformation to metastasis. Here we address how natural tumor-associated processes and traditional cancer therapies are shaped by cGAS-STING signaling, and how this contributes to beneficial or detrimental outcomes of cancer. We consider current efforts to target the cGAS-STING axis in tumors and highlight new frontiers in cGAS-STING biology to inspire thinking about their connection to cancer.

Radiotherapy induced immunogenic cell death by remodeling tumor immune microenvironment

Emerging evidence indicates that the induction of radiotherapy(RT) on the immunogenic cell death (ICD) is not only dependent on its direct cytotoxic effect, changes in the tumor immune microenvironment also play an important role in it. Tumor immune microenvironment (TIME) refers to the immune microenvironment that tumor cells exist, including tumor cells, inflammatory cells, immune cells, various signaling molecules and extracellular matrix. TIME has a barrier effect on the anti-tumor function of immune cells, which can inhibit all stages of anti-tumor immune response. The remodeling of TIME caused by RT may affect the degree of immunogenicity, and make it change from immunosuppressive phenotype to immunostimulatory phenotype. It is of great significance to reveal the causes of immune escape of tumor cells, especially for the treatment of drug-resistant tumor. In this review, we focus on the effect of RT on the TIME, the mechanism of RT in reversing the TIME to suppress intrinsic immunity, and the sensitization effect of the remodeling of TIME caused by RT on the effectiveness of immunotherapy.

Activating Innate Immunity by a STING Signal Amplifier for Local and Systemic Immunotherapy

The number of patients who benefit from acquired immunotherapy is limited. Stimulator of interferon genes (STING) signal activation is a significant component to enhance innate immunity, which has been used to realize broad-spectrum immunotherapy. Here, M@P@HA nanoparticles, as a STING signal amplifier, are constructed to enhance innate immunotherapy. Briefly, when M@P@HA was targeted into tumor cells, the nanoparticles decomposed with Mn²⁺ and activated the release of protoporphyrin (PpIX). Under light irradiation, the generated reactive oxygen species disrupt the cellular redox homeostasis to lead cytoplasm leakage of damaged mitochondrial double-stranded (ds) DNA, which is the initiator of the STING signal. Simultaneously, Mn²⁺ as the immunoregulator could significantly increase the activity of related protein of a STING signal, such as cyclic GMP-AMP synthase (cGAS) and STING, to further amplify the STING signal of tumor cells. Subsequently, the STING signal of tumor-associated macrophages (TAM) is also activated by capturing dsDNA and Mn²⁺ that escaped from tumor cells, so as to enhance innate immunity. It is found that, by amplifying the STING signal of tumor tissue, M@P@HA could not only activate innate immunity but also cascade to activate CD8⁺ T cell infiltration even in a tumor with low immunogenicity.

cGAS and cancer therapy: a double-edged sword

Cyclic guanosine monophosphate-adenosine monophosphate adenosine synthetase (cGAS) is a DNA sensor that detects and binds to cytosolic DNA to generate cyclic GMP-AMP (cGAMP). As a second messenger, cGAMP mainly activates the adapter protein STING, which induces the production of type I interferons (IFNs) and inflammatory cytokines. Mounting evidence shows that cGAS is extensively involved in the innate immune response, senescence, and tumor immunity, thereby exhibiting a tumor-suppressive function, most of which is mediated by the STING pathway. In contrast, cGAS can also act as an oncogenic factor, mostly by increasing genomic instability through inhibitory effects on DNA repair, suggesting its utility as an antitumor target. This article reviews the roles and the underlying mechanisms of cGAS in cancer, particularly focusing on its dual roles in carcinogenesis and tumor progression, which are probably attributable to its classical and nonclassical functions, as well as approaches targeting cGAS for cancer therapy.

The paradox of radiation and T cells in tumors

In this review we consider what appears to be a paradox in immunotherapies based around radiation therapy. The paradox is based on three main points. 1. That T cells are needed for radiation's efficacy; 2. That tumor-specific T cells are enriched in the field of treatment; and 3. That radiation kills T cells in the treatment field. We discuss evidence of the effect of radiation on T cells in the field given their ongoing movement in and out of tissues and the tumor, and how the movement of T cells impacts the treated primary tumor and untreated distant metastases. Given this evidence, we revisit the paradox to understand how the extraordinary efficacy of radiation and immunity in preclinical models is dependent on this radiation sensitive cell.

STING Agonists in Head and Neck Squamous Cell Carcinoma

ABSTRACT

Despite the development of new treatment paradigms and improved biologic understanding of head and neck squamous cell carcinoma (HNSCC), therapeutic resistance remains a substantial problem, and novel treatment approaches are needed. Stimulator of interferon genes (STING) is a critical regulator of the antitumor response through regulation of both immune-dependent and tumor-intrinsic mechanisms. As such, the STING pathway has emerged as a rational pharmacologic target leading to the development of multiple STING agonists. These compounds have impressive preclinical efficacy as single agents and with PD-1 (programmed death-1) axis agents. However, clinical evaluation in this context has yet to show substantial efficacy. In contrast to monotherapy approaches, activation of STING in combination with DNA-damaging agents has been shown to enhance the effect of these agents in preclinical models and represents a promising approach to improve outcomes in patients with HNSCC. In this review, we will discuss the preclinical and clinical data supporting the use of STING agonists and highlight potential avenues of exploration to unlock the potential of these agents in HNSCC.

Enhancing anti-tumour innate immunity by targeting the DNA damage response and pattern recognition receptors in combination with radiotherapy

Radiotherapy is one of the most effective and frequently used treatments for a wide range of cancers. In addition to its direct anti-cancer cytotoxic effects, ionising radiation can augment the anti-tumour immune response by triggering pro-inflammatory signals, DNA damage-induced immunogenic cell death and innate immune activation. Anti-tumour innate immunity can result from recruitment and stimulation of dendritic cells (DCs) which leads to tumour-specific adaptive T-cell priming and immunostimulatory cell infiltration. Conversely, radiotherapy can also induce immunosuppressive and anti-inflammatory mediators that can confer radioresistance. Targeting the DNA damage response (DDR) concomitantly with radiotherapy is an attractive strategy for overcoming radioresistance, both by enhancing the radiosensitivity of tumour relative to normal tissues, and tipping the scales in favour of an immunostimulatory tumour microenvironment. This two-pronged approach exploits genomic instability to circumvent immune evasion, targeting both hallmarks of cancer. In this review, we describe targetable DDR proteins (PARP (poly[ADP-ribose] polymerase); ATM/ATR (ataxia-telangiectasia mutated and Rad3-related), DNA-PKcs (DNA-dependent protein kinase, catalytic subunit) and Wee1 (Wee1-like protein kinase) and their potential intersections with druggable immunomodulatory signalling pathways, including nucleic acid-sensing mechanisms (Toll-like receptors (TLR); cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) and retinoic acid-inducible gene-I (RIG-I)-like receptors), and how these might be exploited to enhance radiation therapy. We summarise current preclinical advances, recent and ongoing clinical trials and the challenges of therapeutic combinations with existing treatments such as immune checkpoint inhibitors.

Lanthanide-Nucleotide Coordination Nanoparticles for STING Activation

Activation of the stimulator of interferon genes (STING) is essential for blocking viral infections and eliciting antitumor immune responses. Local injection of synthetic STING agonists, such as 2'3'-cGAMP [cGAMP = cyclic 5'-guanosine monophosphate (cGMP)-adenosine monophosphate (AMP)], is a promising approach to enhance antiviral functions and cancer immunotherapy. However, the application of such agonists has been hindered by complicated synthetic procedures, high doses, and unsatisfactory systemic immune responses. Herein, we report the design and synthesis of a series of 2'3'-cGAMP surrogates in nanoparticle formulations formed by reactions of AMP, GMP, and coordinating lanthanides. These nanoparticles can stimulate the type-I interferon (IFN) response in both mouse macrophages and human monocytes. We further demonstrate that the use of europium-based nanoparticles as STING-targeted adjuvants significantly promotes the maturation of mouse bone-marrow-derived dendritic cells and major histocompatibility complex class I antigen presentation. Dynamic molecular docking analysis revealed that these nanoparticles bind with high affinity to mouse STING and human STING. Compared with soluble ovalbumin (OVA), subcutaneously immunized europium-based nanovaccines exhibit significantly increased production of primary and secondary anti-OVA antibodies (∼180-fold) in serum, as well as IL-5 (∼28-fold), IFN-γ (∼27-fold), and IFN-α/β (∼4-fold) in splenocytes ex vivo. Compared with the 2'3'-cGAMP/OVA formulation, subcutaneous administration of nanovaccines significantly inhibits B16F10-OVA tumor growth and prolongs the survival of tumor-bearing mice in both therapeutic and protective models. Given the rich supramolecular chemistry with lanthanides, this work will enable a readily accessible platform for potent humoral and cellular immunity while opening new avenues for cost-effective, highly efficient therapeutic delivery of STING agonists.

Activation of Stimulation of Interferon Genes (STING) Signal and Cancer Immunotherapy

Stimulator of interferon gene (STING), an intracellular receptor in the endoplasmic reticulum, could induce the production of cytokines such as type I interferon (IFN) by activating the cGAS-STING signal pathway. In recent years, activation of STING has shown great potential to enhance anti-tumor immunity and reshape the tumor microenvironment, which is expected to be used in tumor immunotherapy. A number of STING agonists have demonstrated promising biological activity and showed excellent synergistic anti-tumor effects in combination with other cancer therapies in preclinical studies and some clinical trials. The combination of STING agonists and ICI also showed a potent effect in improving anti-tumor immunity. In this review, we introduce the cGAS-STING signaling pathway and its effect in tumor immunity and discuss the recent strategies of activation of the STING signaling pathway and its research progress in tumor immunotherapy.

Chromosome instability and aneuploidy as context-dependent activators or inhibitors of antitumor immunity

Chromosome instability (CIN) and its major consequence, aneuploidy, are hallmarks of human cancers. In addition to imposing fitness costs on tumor cells through several cell-intrinsic mechanisms, CIN/aneuploidy also provokes an antitumor immune response. However, as the major contributor to genomic instability, intratumor heterogeneity generated by CIN/aneuploidy helps tumor cells to evolve methods to overcome the antitumor role of the immune system or even convert the immune system to be tumor-promoting. Although the interplay between CIN/aneuploidy and the immune system is complex and context-dependent, understanding this interplay is essential for the success of immunotherapy in tumors exhibiting CIN/aneuploidy, regardless of whether the efficacy of immunotherapy is increased by combination with strategies to promote CIN/aneuploidy or by designing immunotherapies to target CIN/aneuploidy directly.

Activation of STING in the pancreatic tumor microenvironment: A novel therapeutic opportunity

Pancreatic ductal adenocarcinoma (PDAC) is a cancer of poor prognosis that presents with a dense desmoplastic stroma that contributes to therapeutic failure. PDAC patients are mostly unresponsive to immunotherapy. However, hopes to elicit response to immunotherapy have emerged with novel strategies targeting the Stimulator of Interferon Genes (STING) protein, which is a major regulator of tumor-associated inflammation. Combination of STING agonists with conventional immunotherapy approaches has proven to potentiate therapeutic benefits in several cancers. However, recent data underscore that the output of STING activation varies depending on the cellular and tissue context. This suggests that tumor heterogeneity, and in particular the heterogeneity of the tumor microenvironment (TME), is a key factor determining whether STING activation would bear benefits for patients. In this review, we discuss the potential benefits of STING activation in PDAC. To this aim, we describe the major components of the PDAC TME, and the expected consequences of STING activation.

Extracellular vesicle-mediated crosstalk between pancreatic cancer and stromal cells in the tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) interacts closely with the tumor microenvironment (TME). The TME is remodeled by crosstalk between pancreatic cancer cells and stromal cells, and is critical for cancer progression. Extracellular vesicles (EVs), including exosomes and microvesicles, help facilitate an exchange of information both within the TME and to distant organs. EVs have also been identified as potential diagnostic biomarkers, therapeutic targets, and drug carriers for pancreatic cancer treatment. Thus, understanding the selective packaging of EVs cargo and its mechanistic impact will increase our understanding of cancer biology. In this review, we collect and analyze recent findings of the pancreatic cancer-stromal cell interactions mediated by EVs and the mechanisms involved in cancer-related immunity and chemoresistance. These studies demonstrate the vital role of EVs in pancreatic cancer reprogramming and TME remodeling. We also summarize the EVs identified as potential PDAC diagnostic biomarkers and possible therapeutic targets. This greater understanding is a promising avenue for transitioning EVs from bench to bedside.