Cancer cell-intrinsic STING is associated with CD8 + T-cell infiltration and might serve as a potential immunotherapeutic target in hepatocellular carcinoma

Tumor associated macrophages as key contributors and targets in current and future therapies for melanoma

INTRODUCTION

Despite the success of immunotherapies for melanoma in recent years, there remains a significant proportion of patients who do not yet derive benefit from available treatments. Immunotherapies currently licensed for clinical use target the adaptive immune system, focussing on Tcell interactions and functions. However, the most prevalent immune cells within the tumor microenvironment (TME) of melanoma are macrophages, a diverse immune cell subset displaying high plasticity, to which no current therapies are yet directly targeted. Macrophages have been shown not only to activate the adaptive immune response, and enhance cancer cell killing, but, when influenced by factors within the TME of melanoma, these cells also promote melanoma tumorigenesis and metastasis.

AREAS COVERED

We present a review of the most up-to-date literatureavailable on PubMed, focussing on studies from within the last 10 years. We also include data from ongoing and recent clinical trials targeting macrophages in melanoma listed on clinicaltrials.gov.

EXPERT OPINION

Understanding the multifaceted role of macrophages in melanoma, including their interactions with immune and cancer cells, the influence of current therapies on macrophage phenotype and functions and how macrophages could be targeted with novel treatment approaches, are all critical for improving outcomes for patients with melanoma.

The relationship between tumor immunity and the cGAS-STING pathway in breast cancer: An immunohistochemical study

Breast cancer (BC) is classified into four major histological subtypes, namely luminal A, luminal B, HER2, and basal-like, and its treatment is based on these subtypes. The use of immune checkpoint inhibitors against BC depends on the expression of PD-1/PD-L1. Another tumor immune system-the cGAS-STING pathway-is a potential target for cancer immunotherapy. However, the status of the cGAS-STING pathway in BC has not been fully established. Therefore, we investigated the expression status of the cGAS-STING pathway and immune-related proteins in BC. We classified 111 BCs into six groups-29 hormone receptor-positive carcinomas, 12 HER2+ carcinomas (HER2), 8 luminal-HER2 carcinomas, 26 triple-negative breast carcinomas (TNBCs), 21 lobular carcinomas (LC), and 15 carcinomas with apocrine differentiation (CAD)-and investigated the relationship between BC and tumor immunity via the cGAS-STING pathway using histopathological and immunohistochemical methods. Expression of cGAS was high in CADs (100%) and low in TNBCs (35%); STING-positive lymphocytes were high in TNBC (85%, P = 0.0054). Expression of pSTAT3 was significantly high in patients with TNBC (≥10%, 88%). The proportion of PD-L1-positive tumor cells was higher in TNBCs (54%) than in other BCs (30%). SRGN expression was significantly higher in the TNBC group than in the other BC groups (58%). Tumor immune responses may differ among tumor subtypes. The cGAS-STING pathway may be functional in TNBC and CAD but not in LC. Therefore, targeting the cGAS-STING pathway might be useful in BC, particularly TNBC and CAD.

Tumor cell-directed STING agonist antibody-drug conjugates induce type III interferons and anti-tumor innate immune responses

Activating interferon responses with STING agonists (STINGa) is a current cancer immunotherapy strategy, and therapeutic modalities that enable tumor-targeted delivery via systemic administration could be beneficial. Here we demonstrate that tumor cell-directed STING agonist antibody-drug-conjugates (STINGa ADCs) activate STING in tumor cells and myeloid cells and induce anti-tumor innate immune responses in in vitro, in vivo (in female mice), and ex vivo tumor models. We show that the tumor cell-directed STINGa ADCs are internalized into myeloid cells by Fcγ-receptor-I in a tumor antigen-dependent manner. Systemic administration of STINGa ADCs in mice leads to STING activation in tumors, with increased anti-tumor activity and reduced serum cytokine elevations compared to a free STING agonist. Furthermore, STINGa ADCs induce type III interferons, which contribute to the anti-tumor activity by upregulating type I interferon and other key chemokines/cytokines. These findings reveal an important role for type III interferons in the anti-tumor activity elicited by STING agonism and provide rationale for the clinical development of tumor cell-directed STINGa ADCs.

Unraveling the Binding Mode of Cyclic Adenosine-Inosine Monophosphate (cAIMP) to STING through Molecular Dynamics Simulations

The stimulator of interferon genes (STING) plays a significant role in immune defense and protection against tumor proliferation. Many cyclic dinucleotide (CDN) analogues have been reported to regulate its activity, but the dynamic process involved when the ligands activate STING remains unclear. In this work, all-atom molecular dynamics simulations were performed to explore the binding mode between human STING (hSTING) and four cyclic adenosine-inosine monophosphate analogs (cAIMPs), as well as 2',3'-cGMP-AMP (2',3'-cGAMP). The results indicate that these cAIMPs adopt a U-shaped configuration within the binding pocket, forming extensive non-covalent interaction networks with hSTING. These interactions play a significant role in augmenting the binding, particularly in interactions with Tyr167, Arg238, Thr263, and Thr267. Additionally, the presence of hydrophobic interactions between the ligand and the receptor further contributes to the overall stability of the binding. In this work, the conformational changes in hSTING upon binding these cAIMPs were also studied and a significant tendency for hSTING to shift from open to closed state was observed after binding some of the cAIMP ligands.

The dual function of cGAS-STING signaling axis in liver diseases

Numerous liver diseases, such as nonalcoholic fatty liver disease, hepatitis, hepatocellular carcinoma, and hepatic ischemia-reperfusion injury, have been increasingly prevalent, posing significant threats to global health. In recent decades, there has been increasing evidence linking the dysregulation of cyclic-GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING)-related immune signaling to liver disorders. Both hyperactivation and deletion of STING can disrupt the immune microenvironment dysfunction, exacerbating liver disorders. Consequently, there has been a surge in research investigating medical agents or mediators targeting cGAS-STING signaling. Interestingly, therapeutic manipulation of the cGAS-STING pathway has yielded inconsistent and even contradictory effects on different liver diseases due to the distinct physiological characteristics of intrahepatic cells that express and respond to STING. In this review, we comprehensively summarize recent advancements in understanding the dual roles of the STING pathway, highlighting that the benefits of targeting STING signaling depend on the specific types of target cells and stages of liver injury. Additionally, we offer a novel perspective on the suitability of STING agonists and antagonists for clinical assessment. In conclusion, STING signaling remains a highly promising therapeutic target, and the development of STING pathway modulators holds great potential for the treatment of liver diseases.

Update on the STING Signaling Pathway in Developing Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition with limited treatment options. Inflammation caused by metabolic disturbances plays a significant role in NAFLD development. Stimulator of interferon gene (STING), a critical regulator of innate immunity, induces the production of interferons and other pro-inflammatory factors by recognizing cytoplasmic DNA to defend against pathogen infection. The STING-mediated signaling pathway appears to play a vital role in hepatic inflammation, metabolic disorders, and even carcinogenesis. Promisingly, pharmacological interventions targeting STING have shown improvements in the pathological state of NAFLD. Macrophages, dendritic cells, natural killer cells, and T cell pathways regulated by STING present potential novel druggable targets for NAFLD treatment. Further research and development in this area may offer new therapeutic options for managing NAFLD effectively.

Identification and validation of a disulfidptosis-related genes prognostic signature in lung adenocarcinoma

Disulfidptosis, a newly revealed form of cell death, regulated by numerous genes that has been recently identified. The exact role of disulfidptosis in lung adenocarcinoma (LUAD) still uncertain. Objective of this study was to explore potential prognostic markers among disulfidptosis genes in LUAD. By combining transcriptomic information from Gene Expression Omnibus databases and The Cancer Genome Atlas, we identified differentially expressed and prognostic disulfidptosis genes. By conducting least absolute shrinkage and selection operator with multivariate Cox regression, four disulfidptosis genes were selected to create the prognostic signature. The implementation of the signature separated the training and validation cohorts into groups with high- and low-risk. Subsequently, the model was verified by conducting an independent analysis of receiver operating characteristic (ROC) curves. Further comparisons were made between the two risk-divided groups with regards the tumor microenvironment, immune cell infiltration, immunotherapy response, and drug sensitivity. The signature was constructed using four disulfidptosis-related genes: SLC7A11, SLC3A2, NCKAP1, and GYS1. According to ROC curves, the signature was effective for predicting LUAD prognosis. In addition, the prognostic signature correlated with sensitivity to chemotherapeutic agents and the efficacy of immunotherapy in LUAD. Finally, through external validation, we showed that NCKAP1 are correlated with tumor migration, proliferation, and invasion of LUAD cells. GYS1 affects immune cell, especially M2 macrophage infiltration in the tumor microenvironment. The disulfidptosis four-gene model can reliably predict the prognosis of patients diagnosed with LUAD, thereby providing valuable information for clinical applications and immunotherapy.

Caspase-9 inhibition triggers Hsp90-based chemotherapy-mediated tumor intrinsic innate sensing and enhances antitumor immunity

BACKGROUND

Antineoplastic chemotherapies are dramatically efficient when they provoke immunogenic cell death (ICD), thus inducing an antitumor immune response and even tumor elimination. However, activated caspases, the hallmark of most cancer chemotherapeutic agents, render apoptosis immunologically silent. Whether they are dispensable for chemotherapy-induced cell death and the apoptotic clearance of cells in vivo is still elusive.

METHODS

A rational cell-based anticancer drug library screening was performed to explore the immunogenic apoptosis pathway and therapeutic targets under apoptotic caspase inhibition. Based on this screening, the potential of caspase inhibition in enhancing chemotherapy-induced antitumor immunity and the mechanism of actions was investigated by various cells and mouse models.

RESULTS

Heat shock protein 90 (Hsp90) inhibition activates caspases in tumor cells to produce abundant genomic and mitochondrial DNA fragments and results in cell apoptosis. Meanwhile, it hijacks Caspase-9 signaling to suppress intrinsic DNA sensing. Pharmacological blockade or genetic deletion of Caspase-9 causes tumor cells to secrete interferon (IFN)-β via tumor intrinsic mitochondrial DNA/the second messenger cyclic GMP-AMP (cGAS) /stimulator of interferon genes (STING) pathway without impairing Hsp90 inhibition-induced cell death. Importantly, both Caspase-9 and Hsp90 inhibition triggers an ICD, leading to the release of numerous damage-associated molecular patterns such as high-mobility group box protein 1, ATP and type I IFNs in vitro and remarkable antitumor effects in vivo. Moreover, the combination treatment also induces adaptive resistance by upregulating programmed death-ligand 1 (PD-L1). Additional PD-L1 blockade can further overcome this acquired immune resistance and achieve complete tumor regression.

CONCLUSIONS

Blockade of Caspase-9 signaling selectively provokes Hsp90-based chemotherapy-mediated tumor innate sensing, leading to CD8+ T cell-dependent tumor control. Our findings implicate that pharmacological modulation of caspase pathway increases the tumor-intrinsic innate sensing and immunogenicity of chemotherapy-induced apoptosis, and synergizes with immunotherapy to overcome adaptive resistance.

Prognostic significance of STING expression in solid tumor: a systematic review and meta-analysis

Objective

Stimulator of interferon genes (STING) is a key regulator in initiating innate immune response from sensing cytosolic DNA. Recent studies have revealed that the cGAS-STING signaling pathway has a crucial role in tumor development and progression across cancer types. Herein, we conducted a meta-analysis to explore the relationship between the immunoexpression of STING and the survival outcome of patients in various solid tumors. Studies relevant to the subject were searched from PubMed, Embase, and Web of Science.

Results

Eleven studies including 2,345 patients were eligible for the analysis. STING expression in tumor cells was related to improved disease-free survival/recurrence-free survival (DFS/RFS) (HR = 0.656, 95% CI = 0.455-0.946, p = 0.024) but not with overall survival (OS) (HR = 0.779, 95% CI = 0.534-1.136, p = 0.194). STING expression in stromal cells, however, did not show significant correlation with DFS/RFS and OS (HR = 0.979, 95% CI = 0.565-1.697, p-value = 0.940 and HR = 1.295, 95% CI = 0.845-1.985, p = 0.235, respectively). In a subgroup analysis, STING expression in tumor cells was associated with better DFS (HR = 0.622, 95% CI = 0.428-0.903, p = 0.012). In tumor cells, favorable DFS/RFS were also related to studies from univariate analysis and the gastrointestinal system (HR = 0.667, 95% CI = 0.482-0.923, p = 0.015 and HR = 0.566, 95% CI = 0.330-0.971, p = 0.039).

Conclusions

STING expression in tumor cells is associated with favorable outcome in solid tumors.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, registration number: CRD42023427027.

Immunogenicity of small-cell lung cancer associates with STING pathway activation and is enhanced by ATR and TOP1 inhibition

INTRODUCTION

The activation of STING (stimulator of interferon genes) pathway enhances antitumor immunity in small-cell lung cancer (SCLC), while the DNA damage induced by non-cGAMP-based agonists is a potent inducer of STING activity. Here, we investigate the intrinsic expression of STING in cancer cells and evaluate the value of the combination of ATR and TOP1 inhibitors in enhancing antitumor immunity.

METHODS

STING expression was assessed at mRNA and protein levels in SCLC and normal lung tissues. Transcriptomic subsets of SCLC were identified based on STING-related genes. Distinct mutation and immunogenomic profiles of these subsets were determined. The direct antitumor efficacy and the potential of enhancing antitumor immunity of the strategy using the ATR-TOP1-inhibitor combination were tested in SCLC cell lines.

RESULTS

The intrinsic expression of STING was significantly reduced in SCLC compared to normal lung tissues (p < 0.0001). Three STING-related SCLC subtypes were identified in which the STING-high subtype was associated with (1) high immune infiltration, (2) high expression of genes related to MHC and immune checkpoints, and (3) high EMT and ferroptosis score. On the contrary, the STING-low subtype was enriched with pathways related to DNA damage response (DDR) and cell cycle progression. The association between the DDR pathway activity and the STING-IFN innate immune response was verified by in vitro experiments in which the inhibition of ATR and TOP1 triggered the expression of genes encoding type I IFN signaling and pro-inflammatory cytokines/chemokines in a STING-low SCLC cell line.

CONCLUSION

Our study verifies that activation of the STING-IFN response by ATR and TOP1 inhibitors might be a therapeutic strategy to improve the response to immune checkpoint therapy in STING-low SCLC. Furthermore, the combinations of ATR and TOP1 inhibitors can augment tumor inflammation in STING-low SCLC.

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.