Cancer cell-specific cGAS/STING Signaling pathway in the era of advancing cancer cell biology

Cancer cell-extrinsic STING shapes immune-active microenvironment and predicts clinical outcome in gastric cancer

PURPOSE

The activation of cGAS-STING pathway can be triggered by cytosolic double-stranded DNA (dsDNA) in tumor and non-tumor compartments. We aim to assess the constitutive expression of dsDNA-cGAS-STING axis in different cellular contexts and compare their relative contribution to clinical outcomes.

METHODS

A cohort of 154 cases of patients with newly diagnosed gastric cancer were enrolled in this study to evaluate the histo-score of cytosolic dsDNA, cGAS, and STING via immunohistochemistry as well as the types and densities of tumor-infiltrating immune cells. Kaplan-Meier method, multivariable regression, and receiver operating characteristic curve were implemented to analyze the prognostic efficacy of dsDNA-cGAS-STING axis in distinct compartments.

RESULTS

The supra-normal concentration of cytosolic dsDNA correlated with the constitutive expression of cGAS-STING pathway in tumor compartments. In contrast to the lack of STING within cancer cells, the higher STING expression in non-tumor compartments indicated a transcellular cGAS-STING activation. Cancer cell-extrinsic STING was supported to potentiate nucleic acid immunity by sensing tumor-derived dsDNA fragments. Compartmental analyses also confirmed that the level of STING expressed in non-tumor cells was associated with the infiltration of protective immune cells, leading to the prolonged overall survival. Multivariate analysis further identified the independent prognostic value of cancer cell-extrinsic STING and its predictive accuracy could be significantly improved in combination with the immune cell infiltration.

CONCLUSIONS

Cancer cell-extrinsic STING facilitates the remodeling of immune-active tumor microenvironment and acts as an independent prognostic factor in gastric cancer.

Accelerating and protective effects toward cancer growth in cGAS and FcgRIIb deficient mice, respectively, an impact of macrophage polarization

BACKGROUND

Due to the possible influence of inflammation and gut microbiota in cancers.

METHODS

Fc gamma receptor IIb deficient (FcGRIIb-/-) and cyclic GMP-AMP synthase deficient (cGAS-/-) mice, the model with hyperinflammation and hypo-inflammation, respectively, were subcutaneously injected with MC38 cells (a murine colon cancer cell line).

RESULTS

As such, the tumor burdens were most prominent in cGAS-/- mice, while FcGRIIb-/- mice demonstrated the least tumor sizes compared with wild-type (WT). Intra-tumoral mononuclear cells of FcGRIIb-/- (hematoxylin and eosin staining) were more prominent than other groups with the most dominant CD86-positive cells (mostly M1 proinflammatory macrophages) and the least CD206-positive cells (mostly M2 anti-inflammatory macrophages). While fecal microbiome analysis demonstrated a subtle difference among mouse strains with tumors at 24 days post-cancer injection, serum cytokines (TNF-α, IL-6, IL-1α, IFN-β, IFN-γ, IL-23, IL-12p70, GM-CSF, IL-27, and IL-17A) (fluorescence-encoded bead multiplex assay) and the expansion of immune cells in the spleens of FcGRIIb-/- mice (flow cytometry) were more prominent than others. With bone marrow-derived macrophages, prominent M1 (LPS) and M2 polarization (IL4 and cancer supernatant) in FcGRIIb-/- and cGAS-/- macrophages, respectively, were demonstrated using polymerase chain reaction and flow cytometry. The most prominent tumoricidal activity (percentage of F4/80-negative flexible780 viable dye-positive cells using flow cytometry) of LPS-stimulated FcGRIIb-/- macrophages compared with other groups supported dominant pro-inflammatory characteristics of FcGRIIb-/- macrophages.

CONCLUSIONS

In conclusion, the protective and promoting effects of FcGRIIb-/- and cGAS-/- mice, respectively, against cancers are partly related to macrophage functions with a subtle correlation to fecal microbiota, and FcGRIIb inhibitors and cGAS enhancers might be helpful for cancer adjuvant treatment.

The cGAS-STING pathway in cancer immunity: dual roles, therapeutic strategies, and clinical challenges

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is a crucial component of the host's innate immunity and plays a central role in detecting cytosolic double-stranded DNA from endogenous and exogenous sources. Upon activation, cGAS synthesizes cGAMP, which binds to STING, triggering a cascade of immune responses, including the production of type I interferons and pro-inflammatory cytokines. In the context of cancers, the cGAS-STING pathway can exert dual roles: on the one hand, it promotes anti-tumor immunity by enhancing antigen presentation, stimulating T-cell responses, and inducing direct tumor cell apoptosis. On the other hand, chronic activation, particularly in tumors with chromosomal instability, can lead to immune suppression and tumor progression. Persistent cGAS-STING signaling results in the up-regulation of immune checkpoint molecules such as PD-L1, contributing to immune evasion and metastasis. Consequently, anti-tumor strategies targeting the cGAS-STING pathway have to consider the balance of immune activation and the immune tolerance caused by chronic activation. This review explores the mechanisms underlying both the anti-tumor and protumor roles of the cGAS-STING pathway, with a focus on potential therapeutic approaches, and the challenges faced in their clinical application, along with corresponding solutions.

Role of Cell Adhesion in Cancer Metastasis Formation: A Review

Intercellular adhesion is accompanied by several physical quantities and actions. In this review, we tried to collect information about the influence of surface energy and its impact on cell-cell adhesion. It still undergoes development for cancer treatment. Data on receptor-ligand interactions that occur on circulating tumor cells (CTCs) are described, and adhesion receptors as therapeutic targets are collected. Additionally, the impact of surface roughness on the interactions between CTC cells and the surface was monitored. The effects of different cell adhesion molecules (CAMs) on cell adhesion, growth, and proliferation were investigated. This review offers general principles of cell adhesion, through the blockade of adhesion with blocking drugs and inhibitors like computational models that describe the process of adhesion. Some theoretical models based on the minimum of the total free energy of interaction between CAMs and selected organic molecules have been presented. The final aim was to find information on how modulation of the surface of CTCs (by medicals or physically) inhibits cancer metastases formation.

New insight in immunotherapy and combine therapy in colorectal cancer

The advent of immune checkpoint inhibitors (ICIs) in colorectal cancer (CRC) treatment marks a major breakthrough. These therapies have proven safer and more effective than traditional radiotherapy and targeted treatments. Immunotherapies like pembrolizumab, nivolumab, and ipilimumab have pioneered new treatment avenues, potentially improving patient outcomes and quality of life. Additionally, advances in immunotherapy have prompted detailed research into CRC therapies, especially those integrating ICIs with conventional treatments, providing new hope for patients and shaping future research and practice. This review delves into the mechanisms of various ICIs and evaluates their therapeutic potential when combined with radiotherapy, chemotherapy, and targeted therapies in clinical settings. It also sheds light on the current application and research involving ICIs in CRC treatment.

Epigenetic modulation of immune cells: Mechanisms and implications

Epigenetic modulation of the immune response entails modifiable and inheritable modifications that do not modify the DNA sequence. While there have been many studies on epigenetic changes in tumor cells, there is now a growing focus on epigenetically mediated changes in immune cells of both the innate and adaptive systems. These changes have significant implications for both the body's response to tumors and the development of potential therapeutic vaccines. This study primarily discusses the key epigenetic alterations, with a specific emphasis on pseudouridination, as well as non-coding RNAs and their transportation, which can lead to the development of cancer and the acquisition of new phenotypic traits by immune cells. Furthermore, the advancement of therapeutic vaccinations targeting the tumor will be outlined.

FLASH Radiotherapy: Benefits, Mechanisms, and Obstacles to Its Clinical Application

Radiotherapy (RT) has been shown to be a cornerstone of both palliative and curative tumor care. RT has generally been reported to be sharply limited by ionizing radiation (IR)-induced toxicity, thereby constraining the control effect of RT on tumor growth. FLASH-RT is the delivery of ultra-high dose rate (UHDR) several orders of magnitude higher than what is presently used in conventional RT (CONV-RT). The FLASH-RT clinical trials have been designed to examine the UHDR deliverability, the effectiveness of tumor control, the dose tolerance of normal tissue, and the reproducibility of treatment effects across several institutions. Although it is still in its infancy, FLASH-RT has been shown to have potential to rival current RT in terms of safety. Several studies have suggested that the adoption of FLASH-RT is very limited, and the incorporation of this new technique into routine clinical RT will require the use of accurate dosimetry methods and reproducible equipment that enable the reliable and robust measurements of doses and dose rates. The purpose of this review is to highlight the advantages of this technology, the potential mechanisms underpinning the FLASH-RT effect, and the major challenges that need to be tackled in the clinical transfer of FLASH-RT.

Make it STING: nanotechnological approaches for activating cGAS/STING as an immunomodulatory node in osteosarcoma

Osteosarcoma is a highly aggressive bone cancer primarily affecting children, adolescents, and young adults. The current gold standard for treatment of osteosarcoma patients consists of two to three rounds of chemotherapy, followed by extensive surgical intervention from total limb reconstruction to amputation, followed by additional rounds of chemotherapy. Although chemotherapy has advanced the treatment of osteosarcoma significantly, the overall 5-year survival rate in resistant forms of osteosarcoma is still below 20%. The interaction between cancer and the immune system has long been recognized as a critical aspect of tumour growth. Tumour cells within the tumour microenvironment (TME) suppress antitumour immunity, and immunosuppressive cells and cytokines provide the extrinsic factors of tumour drug resistance. Emerging research demonstrates an immunostimulatory role for the cGAS/STING pathway in osteosarcoma, typically considered an immune-cold or immunosuppressed cancer type. cGAS/STING signalling appears to drive an innate immune response against tumours and potentiates the efficacy of other common therapies including chemo and radiotherapy. Nanotechnological delivery systems for improved therapy delivery for osteosarcoma have also been under investigation in recent years. This review provides an overview of cGAS/STING signalling, its divergent roles in the context of cancer, and collates current research which activates cGAS/STING as an adjuvant immunomodulatory target for the treatment of osteosarcoma. It will also discuss current nanotechnological delivery approaches that have been developed to stimulate cGAS/STING. Finally, it will highlight the future directions that we believe will be central to the development of this transformative field.

Radiotherapy and immunology

The majority of cancer patients receive radiotherapy during the course of treatment, delivered with curative intent for local tumor control or as part of a multimodality regimen aimed at eliminating distant metastasis. A major focus of research has been DNA damage; however, in the past two decades, emphasis has shifted to the important role the immune system plays in radiotherapy-induced anti-tumor effects. Radiotherapy reprograms the tumor microenvironment, triggering DNA and RNA sensing cascades that activate innate immunity and ultimately enhance adaptive immunity. In opposition, radiotherapy also induces suppression of anti-tumor immunity, including recruitment of regulatory T cells, myeloid-derived suppressor cells, and suppressive macrophages. The balance of pro- and anti-tumor immunity is regulated in part by radiotherapy-induced chemokines and cytokines. Microbiota can also influence radiotherapy outcomes and is under clinical investigation. Blockade of the PD-1/PD-L1 axis and CTLA-4 has been extensively investigated in combination with radiotherapy; we include a review of clinical trials involving inhibition of these immune checkpoints and radiotherapy.

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.

cGLRs Join Their Cousins of Pattern Recognition Receptor Family to Regulate Immune Homeostasis

Pattern recognition receptors (PRRs) recognize danger signals such as PAMPs/MAMPs and DAMPs to initiate a protective immune response. TLRs, NLRs, CLRs, and RLRs are well-characterized PRRs of the host immune system. cGLRs have been recently identified as PRRs. In humans, the cGAS/STING signaling pathway is a part of cGLRs. cGAS recognizes cytosolic dsDNA as a PAMP or DAMP to initiate the STING-dependent immune response comprising type 1 IFN release, NF-κB activation, autophagy, and cellular senescence. The present article discusses the emergence of cGLRs as critical PRRs and how they regulate immune responses. We examined the role of cGAS/STING signaling, a well-studied cGLR system, in the activation of the immune system. The following sections discuss the role of cGAS/STING dysregulation in disease and how immune cross-talk with other PRRs maintains immune homeostasis. This understanding will lead to the design of better vaccines and immunotherapeutics for various diseases, including infections, autoimmunity, and cancers.

Cyclic GMP-AMP Synthase in Cancer Prevention

Cyclic GMP-AMP (cGAMP), synthesized by cGAMP synthase (cGAS), serves as a secondary messenger that modulates various cellular processes, including cell proliferation, cell death, immune response, and inflammation. cGAS is activated upon detecting cytoplasmic DNA, which may originate from damaged genomic and mitochondrial DNA or from viral and bacterial infections. The presence of DNA in the cytoplasm can trigger a substantial inflammatory reaction and cytokine production via the cGAS-STING signaling pathway. Consequently, specific inhibitors targeting this pathway hold significant potential as chemopreventive agents. In this review, we explore the potential effectiveness of modulating cGAS activity. We discuss the role of cGAMP, the mechanism of action for distinguishing between self and foreign DNA, and the possible functions of cGAS within the nucleus.