Emerging mechanisms of pyroptosis and its therapeutic strategy in cancer

Genetically modified extracellular vesicles loaded with activated gasdermin D potentially inhibit prostate-specific membrane antigen-positive prostate carcinoma growth and enhance immunotherapy

Prostate cancer (PCa) is associated with poor immunogenicity and lymphocytic infiltration, and immunotherapy effective against PCa remains unavailable. Pyroptosis, a novel immunotherapeutic modality for cancer, promotes systemic immune responses leading to immunogenic cell death in solid tumors. This paper describes the preparation and analysis of PSMAscFv-EVN-GSDMD; this genetically engineered recombinant extracellular vesicle (EV) expresses a single-chain variable antibody fragment (scFv) with high affinity for prostate-specific membrane antigen (PSMA) on their surfaces and is loaded with the N-terminal domain of gasdermin D (GSDMD). Both in vitro and in vivo, PSMAscFv-EVN-GSDMD effectively targeted PSMA-positive PCa cells and induced pyroptosis through the carrier properties of EVs and the specificity of PSMAscFv. In the 22RV1 and PSMA-transfected RM-1-inoculated PCa mouse models, PSMAscFv-EVN-GSDMD efficiently inhibited tumor growth and promoted tumor immune responses. In conclusion, PSMAscFv-EVN-GSDMD can convert the immunosuppressive "cold" tumor microenvironment of PCa into an immunogenic "hot" tumor microenvironment.

Allosteric inhibition of the tyrosine phosphatase SHP2 enhances the anti-tumor immunity of interferon α through induction of caspase-1-mediated pyroptosis in renal cancer

Interferon alpha (IFNα) leads to therapeutic effects on various tumors, especially renal cell cancer (RCC), by directly protecting against tumors cell proliferation or indirectly inducing an anti-tumor immune response. However, new combination therapies are needed to enhance the efficacy of IFNα and reduce its adverse effects during long-term treatment. In this study, we found that the anti-proliferative effects of IFNα on RCC cells in vitro and in vivo were greater after the allosteric inhibition of SHP2 by SHP099 than after treatment with enzymatic inhibitors of SHP2. SHP099 increased IFNα-induced pro-caspase-1 expression in RCC cells, activated the NLRP3 inflammasome, and induced pyroptosis. Mechanistically, SHP099 not only increased the expression of NLRP3 inflammasome components via the NF-κB signaling pathway, but also further activated the NLRP3 inflammasome by regulating mitochondrial homeostasis through ANT1-mediated reactive oxygen species modulation. Allosteric inhibition of SHP2 by SHP099 also potently enhanced the anti-tumor immunity induced by IFNα by modulating T cell proliferation and infiltration in vitro and in vivo. These results reveal the new function of SHP2 in NLRP3 inflammasome activation and pyroptosis in RCC and provide a basis for further investigating the combination of allosteric SHP2 inhibitors with IFNα in cancer immunotherapy.

Rabeprazole inhibits lung cancer progression by triggering NLRP3/CASP-1/caspase-dependent pyroptosis

BACKGROUND

Gastric acid-related diseases could be treated using proton pump inhibitors (PPIs), which have been found to have anti-tumor ability. Rabeprazole is a type of PPI whose effect and mechanism in lung cancer remained to be clarified.

METHODS

Lung cancer cells and lung cancer mice were treated with different concentrations of Rabeprazole and then cell proliferation was detected by CCK-8 and colony formation assays. Pyroptosis was assessed by morphological observation and Lactate dehydrogenase (LDH) release assays. Western blot, immunofluorescence and immunohistochemistry were adopted to detect the expressions of GSDMD and NLRP3. Reactive oxygen species (ROS) level, lysosomal damage and autophagic flux were measured by flow cytometry.

RESULTS

Rabeprazole suppressed lung cancer cell proliferation and lung tumor growth in mice in a concentration-dependent manner. Lung cancer cells treated with Rabeprazole showed typical pyroptosis morphology and significantly increased LDH release. Rabeprazole upregulated the expression of GSDMD, NLRP3, and cleaved-Caspase 1, but such an effect was partially blocked by Z-LLSD-FMK. In lung cancer cells treated with Rabeprazole and lung cancer mice injected with Rabeprazole, the expressions of GSDMD, NLRP3 and caspase-1 were promoted, ROS-stained cells were increased significantly, lysosomal damage was aggravated, and autophagic flux was noticeably reduced.

CONCLUSIONS

Rabeprazole activated NLRP3/caspase 1/GSDMD cascade by promoting ROS accumulation and lysosomal destruction, thereby inducing pyroptosis to fulfill its anti-tumor effect on lung cancer.

Dual Role of Lysosome in Cancer Development and Progression

Lysosomes are essential intracellular catabolic organelles that contain digestive enzymes involved in the degradation and recycle of damaged proteins, organelles, etc. Thus, they play an important role in various biological processes, including autophagy regulation, ion homeostasis, cell death, cell senescence. A myriad of studies has shown that the dysfunction of lysosome is implicated in human aging and various age-related diseases, including cancer. However, what is noteworthy is that the modulation of lysosome-based signaling and degradation has both the cancer-suppressive and cancer-promotive functions in diverse cancers depending on stage, biology, or tumor microenvironment. This dual role limits their application as targets in cancer therapy. In this review, we provide an overview of lysosome and autophagy-lysosomal pathway and outline their critical roles in many cellular processes, including cell death. We highlight the different functions of autophagy-lysosomal pathway in cancer development and progression, underscoring its potential as a target for effective cancer therapies.

PD-1+CD8+ T Cell-Mediated Hepatocyte Pyroptosis Promotes Progression of Murine Autoimmune Liver Disease

The specific mechanisms underlying effector pathways in autoimmune liver disease remain enigmatic and therefore constructing appropriate murine models to investigate disease pathogenesis becomes critical. A spontaneous severe murine model of autoimmune liver disease has been previously established in dnTGFβRII Aire-/- mice, exhibiting disease phenotypes that resemble both human primary biliary cholangitis (PBC) and autoimmune hepatitis (AIH). The data suggests that auto-reactive liver-specific CD8+ T cells are the primary pathogenic cells in liver injury. In this study, these data are advanced through the use of both single-cell sequencing and extensive in vitro analysis. The results identify a specific expanded pathogenic subset of PD-1+CD8+ T cells in the liver, exhibiting strong functional activity and cytotoxicity against target cells. Depletion of PD-1+CD8+ T cells using CAR-T cells effectively alleviates the disease. GSDMD-mediated pyroptosis is found to be aberrantly activated in the livers of model mice, and treatment with a GSDMD-specific inhibitor significantly inhibits disease progression. In vitro experiments reveal that PD-1+CD8+ T cells can induce the pyroptosis of hepatocytes through elevated production of granzyme B and perforin-1. These results provide a novel explanation for the cytotoxic activity of pathogenic liver PD-1+CD8+ T cells in autoimmune liver diseases and offer potential therapeutic targets.

Impact of Nordihydroguaiaretic Acid on Proliferation, Energy Metabolism, and Chemosensitization in Non-Small-Cell Lung Cancer (NSCLC) Cell Lines

Lung cancer (LC) is the leading cause of cancer death worldwide. LC can be classified into small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC), with the last subtype accounting for approximately 85% of all diagnosed lung cancer cases. Despite the existence of different types of treatment for this disease, the development of resistance to therapies and tumor recurrence in patients have maintained the need to find new therapeutic options to combat this pathology, where natural products stand out as an attractive source for this search. Nordihydroguaiaretic acid (NDGA) is the main metabolite extracted from the Larrea tridentata plant and has been shown to have different biological activities, including anticancer activity. In this study, H1975, H1299, and A549 cell lines were treated with NDGA, and its effect on cell viability, proliferation, and metabolism was evaluated using a resazurin reduction assay, incorporation of BrdU, and ki-67 gene expression and glucose uptake measurement, respectively. In addition, the combination of NDGA with clinical chemotherapeutics was investigated using an MTT assay and Combenefit software (version 2.02). The results showed that NDGA decreases the viability and proliferation of NSCLC cells and differentially modulates the expression of genes associated with different metabolic pathways. For example, the LDH gene expression decreased in all cell lines analyzed. However, GLUT3 gene expression increased after 24 h of treatment. The expression of the HIF-1 gene decreased early in the H1299 and A549 cell lines. In addition, the combination of NDGA with three chemotherapeutics (carboplatin, gemcitabine, and taxol) shows a synergic pattern in the decrease of cell viability on the H1299 cell line. In summary, this research provides new evidence about the role of NDGA in lung cancer. Interestingly, using NDGA to enhance the anticancer activity of antitumoral drugs could be an improved therapeutic resource against lung cancer.

Cinobufotalin inhibits proliferation, migration and invasion in hepatocellular carcinoma by triggering NOX4/NLRP3/GSDMD-dependent pyroptosis

Introduction

Pyroptosis is an inflammatory form of programmed cell death that plays a significant role in tumorigenesis. Cinobufotalin (CB), a bufadienolide extracted from toad venom, is associated with antitumor effects in various cancers, including liver cancer. However, the role of CB in pyroptosis and its underlying mechanisms have not been well characterized.

Methods

MTT, Colony formation, EdU, Wound healing and Transwell migration and invasion assays were applied to determine the effects of CB on the proliferation, migration, and invasion ability of hepatocellular carcinoma (HCC) cells in vitro. The subcutaneous xenograft mouse model and pulmonary metastasis model were used to evaluate the effect of CB on HCC cells in vivo. PCR, western blot, immunohistochemistry, immunofluorescence, and ELISA were used to verify the expression of proliferation, migration, pyroptosis, and inflammation related molecules after CB treatment. Using si-RNA and inhibitors to interfere with NOX4 and HLRP3 expression to validate the key signaling pathways of pyroptosis induced by CB treatment.

Results

In vivo experiments using nude mice with xenografted HCC cells and in vitro experiments with HCC cell lines demonstrated that CB treatment significantly inhibited the proliferation, migration, and invasiveness of HCC cells. CB treatment also showed dose-dependent activation of the NLRP3 inflammasome complex in HCC cells, leading to gasdermin D-induced pyroptosis. However, these effects were abrogated via the pretreatment of HCC cells with VX-765, a caspase-1 inhibitor. Additionally, CB increased the production of reactive oxygen species (ROS) and H₂O₂, along with upregulating NOX4 protein expression in HCC cells. Conversely, NOX4 silencing or pretreatment with VAS2870 (an NOX4 inhibitor) or NAC (an ROS scavenger) suppressed the activation of the NLRP3 inflammasome complex and pyroptosis in CB-treated HCC cells.

Discussion

Our study demonstrated that CB suppressed the proliferation, migration, and invasiveness of HCC cells by inducing pyroptosis through the activation of the NOX4/NLRP3/GSDMD signaling pathway. Therefore, our results suggest that CB is a promising therapeutic agent for HCC.

Dronedarone hydrochloride (DH) induces pancreatic cancer cell death by triggering mtDNA-mediated pyroptosis

Pancreatic cancer is one of the leading causes of cancer-associated mortality, with a poor treatment approach. Previous study has shown that inducing pyroptosis in pancreatic ductal adenocarcinoma (PDAC) slows the growth of PDACs, implying that pyroptosis inducers are potentially effective for PDAC therapy. Here, we found that Dronedarone hydrochloride (DH), an antiarrhythmic drug, induces pyroptosis in pancreatic cancer cells and inhibits PDAC development in mice. In PANC-1 cells, DH caused cell death in a dosage- and time-dependent manner, with only pyroptosis inhibitors and GSDMD silencing rescuing the cell death, indicating that DH triggered GSDMD-dependent pyroptosis. Further work revealed that DH increased mitochondrial stresses and caused mitochondrial DNA (mtDNA) leakage, activating the cytosolic STING-cGAS and pyroptosis pathways. Finally, we assessed the anti-cancer effects of DH in a pancreatic cancer mouse model and found that DH treatment suppressed pancreatic tumor development in vivo. Collectively, our investigation demonstrates that DH triggers pyroptosis in PDAC and proposes its potential effects on anti-PDAC growth.

Pyroptosis and chemical classification of pyroptotic agents

Pyroptosis, as a lytic-inflammatory type of programmed cell death, has garnered considerable attention due to its role in cancer chemotherapy and many inflammatory diseases. This review will discuss the biochemical classification of pyroptotic inducers according to their chemical structure, pyroptotic mechanism, and cancer type of these targets. A structure-activity relationship study on pyroptotic inducers is revealed based on the surveyed pyroptotic inducer chemotherapeutics. The shared features in the chemical structures of current pyroptotic inducer agents were displayed, including an essential cyclic head, a vital linker, and a hydrophilic tail that is significant for π-π interactions and hydrogen bonding. The presented structural features will open the way to design new hybridized classes or scaffolds as potent pyroptotic inducers in the future, which may represent a solution to the apoptotic-resistance dilemma along with synergistic chemotherapeutic advantage.

An Overview of Hexavalent Chromium-Induced Necroptosis, Pyroptosis, and Ferroptosis

Heavy metals are common environmental industrial pollutants. Due to anthropogenic activity, chromium, especially its hexavalent form [Cr(VI)], is a widespread environmental contaminant that poses a threat to human health. In this review paper, we summarize the currently reported molecular mechanisms involved in chromium toxicity with a focus on the induction of pro-inflammatory non-apoptotic cell death pathways such as necroptosis, pyroptosis, and ferroptosis. The review highlights the ability of chromium to induce necroptosis, pyroptosis, and ferroptosis revealing the signaling pathways involved. Cr(VI) can induce RIPK1/RIPK3-dependent necroptosis both in vitro and in vivo. Chromium toxicity is associated with pyroptotic NLRP3 inflammasome/caspase-1/gasdermin D-dependent secretion of IL-1β and IL-18. Furthermore, this review emphasizes the role of redox imbalance and intracellular iron accumulation in Cr(VI)-induced ferroptosis. Of note, the crosstalk between the investigated lethal subroutines in chromium-induced toxicity is primarily mediated by reactive oxygen species (ROS), which are suggested to act as a rheostat determining the cell death pathway in cells exposed to chromium. The current study provides novel insights into the pro-inflammatory effects of chromium, since necroptosis, pyroptosis, and ferroptosis affect inflammation owing to their immunogenic properties linked primarily with damage-associated molecular patterns. Inhibition of these non-apoptotic lethal subroutines can be considered a therapeutic strategy to reduce the toxicity of heavy metals, including chromium.

CRLF1 bridges AKT and mTORC2 through SIN1 to inhibit pyroptosis and enhance chemo-resistance in ovarian cancer

Ovarian cancer, the second most leading cause of gynecologic cancer mortality worldwide, is challenged by chemotherapy resistance, presenting a significant hurdle. Pyroptosis, an inflammation-linked programmed cell death mediated by gasdermins, has been shown to impact chemoresistance when dysregulated. However, the mechanisms connecting pyroptosis to chemotherapy resistance in ovarian cancer are unclear. We found that cytokine receptor-like factor 1 (CRLF1) is a novel component of mTORC2, enhancing AKT Ser473 phosphorylation through strengthening the interaction between AKT and stress-activated protein kinase interacting protein 1 (SIN1), which in turn inhibits the mitogen-activated protein kinase kinase kinase 5 (ASK1)-JNK-caspase-3-gasdermin E pyroptotic pathway and ultimately confers chemoresistance. High CRLF1-expressing tumors showed sensitivity to AKT inhibition but tolerance to cisplatin. Remarkably, overexpression of binding-defective CRLF1 variants impaired AKT-SIN1 interaction, promoting pyroptosis and chemosensitization. Thus, CRLF1 critically regulates chemoresistance in ovarian cancer by modulating AKT/SIN1-dependent pyroptosis. Binding-defective CRLF1 variants could be developed as tumor-specific polypeptide drugs to enhance chemotherapy for ovarian cancer.

Saikosaponins Targeting Programmed Cell Death as Anticancer Agents: Mechanisms and Future Perspectives

Saikosaponins (SS), which are major bioactive compounds in Radix Bupleuri, have long been used clinically for multicomponent, multitarget, and multipathway therapeutic strategies. Programmed cell death (PCD) induction is among the multiple mechanisms of SS and mediates the anticancer efficacy of this drug family. Although SS show promise for anticancer therapy, the available data to explain how SS mediate their key anticancer effects through PCD (apoptosis, autophagy, ferroptosis, and pyroptosis) remain limited and piecemeal. This review offers an extensive analysis of the key pathways and mechanisms involved in PCD and explores the importance of SS in cancer. We believe that high-quality clinical trials and a deeper understanding of the pharmacological targets involved in the signalling cascades that govern tumour initiation and progression are needed to facilitate the development of innovative SS-based treatments. Elucidating the specific anticancer pathways activated by SS and further clarifying how comprehensive therapies lead to cross-link among the different types of cell death will inspire the clinical translation of SS as cancer treatments.

Co-exposure of microcystin-LR and nitrite induced kidney injury through TLR4/NLRP3/GSDMD-mediated pyroptosis

The degradation of cyanobacterial blooms releases hazardous contaminants such as microcystin-LR (MC-LR) and nitrite, which may collectively exert toxicity on various bodily systems. To evaluate their individual and combined toxicity in the kidney, mice were subjected to different concentrations of MC-LR and/or nitrite over a 6-month period in this study. The results revealed that combined exposure to MC-LR and nitrite exacerbated renal pathological alterations and dysfunction compared to exposure to either compound alone. Specifically, the protein and mRNA expression of kidney injury biomarkers, such as kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), were notably increased in combined exposure group. Concurrently, co-exposure to MC-LR and nitrite remarkedly upregulated levels of proinflammatory cytokines TNF-α, IL-6 and IL-1β, while decreasing the anti-inflammatory cytokine IL-10. Notably, MC-LR and nitrite exhibited synergistic effects on the upregulation of renal IL-1β levels. Moreover, MC-LR combined with nitrite not only elevated mRNA levels of proinflammatory cytokines but also increased protein levels of pyroptosis biomarkers such as IL-1β, Gasdermin D (GSDMD), and Cleaved-GSDMD. Mechanistic investigations revealed that co-exposure to MC-LR and nitrite promoted pyroptosis both in vivo and in vitro, possibly through the activation of the TLR4/NLRP3/GSDMD pathway. Pretreatment with TLR4 inhibitor and NLRP3 inhibitor effectively suppressed pyroptosis induced by the co-exposure of these two toxins in HEK293T cells. These findings provide compelling evidence that MC-LR combined with nitrite synergistically induces pyroptosis in the kidney by activating the TLR4/NLRP3/GSDMD pathway. Overall, this study significantly enhances our comprehension of how environmental toxins interact and induce harm to the kidneys, offering promising avenues for identifying therapeutic targets to alleviate their toxic effects on renal health.

Targeting ROS in cancer: rationale and strategies

Reactive oxygen species (ROS) in biological systems are transient but essential molecules that are generated and eliminated by a complex set of delicately balanced molecular machineries. Disruption of redox homeostasis has been associated with various human diseases, especially cancer, in which increased ROS levels are thought to have a major role in tumour development and progression. As such, modulation of cellular redox status by targeting ROS and their regulatory machineries is considered a promising therapeutic strategy for cancer treatment. Recently, there has been major progress in this field, including the discovery of novel redox signalling pathways that affect the metabolism of tumour cells as well as immune cells in the tumour microenvironment, and the intriguing ROS regulation of biomolecular phase separation. Progress has also been made in exploring redox regulation in cancer stem cells, the role of ROS in determining cell fate and new anticancer agents that target ROS. This Review discusses these research developments and their implications for cancer therapy and drug discovery, as well as emerging concepts, paradoxes and future perspectives.

Gain-of-function variants in GSDME cause pyroptosis and apoptosis associated with post-lingual hearing loss

Gasdermin E (GSDME), a member of the gasdermin protein family, is associated with post-lingual hearing loss. All GSDME pathogenic mutations lead to skipping exon 8; however, the molecular mechanisms underlying hearing loss caused by GSDME mutants remain unclear. GSDME was recently identified as one of the mediators of programmed cell death, including apoptosis and pyroptosis. Therefore, in this study, we injected mice with GSDME mutant (MT) and examined the expression levels to assess its effect on hearing impairment. We observed loss of hair cells in the organ of Corti and spiral ganglion neurons. Further, the N-terminal release from the GSDME mutant in HEI-OC1 cells caused pyroptosis, characterized by cell swelling and rupture of the plasma membrane, releasing lactate dehydrogenase and cytokines such as interleukin-1β. We also observed that the N-terminal release from GSDME mutants could permeabilize the mitochondrial membrane, releasing cytochromes and activating the mitochondrial apoptotic pathway, thereby generating possible positive feedback on the cleavage of GSDME. Furthermore, we found that treatment with disulfiram or dimethyl fumarate might inhibit pyroptosis and apoptosis by inhibiting the release of GSDME-N from GSDME mutants. In conclusion, this study elucidated the molecular mechanism associated with hearing loss caused by GSDME gene mutations, offering novel insights for potential treatment strategies.

Cycloheptylprodigiosin from marine bacterium Spartinivicinus ruber MCCC 1K03745T induces a novel form of cell death characterized by Golgi disruption and enhanced secretion of cathepsin D in non-small cell lung cancer cell lines

Prodiginines have been studied extensively for their anticancer activity, however, the majority of the research has focused on prodigiosin. In this study, cycloheptylprodigiosin (S-1) is extracted from marine bacterium Spartinivicinus ruber MCCC 1K03745T, and its anticancer property was investigated. It exhibits remarkable cytotoxicity against a panel of human lung cancer cell lines, with the IC50 values ranging from 84.89 nM to 661.2 nM. After 6 h of treatment, S-1 gradually accumulates on mitochondria and lysosomes. While lower doses of S-1 induce cell cycle arrest, treatment with higher doses results in cell death in apoptotic independent manner in both NCI-H1299 and NCI-H460 cell lines. Interestingly, treatment with S-1 leads to the accumulation of LC3B-II via pathways that vary among different cell lines. In addition to its role as an autophagy inhibitor, S-1 also promotes autophagy initiation as demonstrated by the increment of EGFP fragment in the EGFP-LC3 degradation assay, however, inhibition of autophagy does not rescue cells from death induced by S-1. Mechanistically, S-1 impairs autophagic flux through disrupting acidic lysosomal pH and blocking the maturation of cathepsin D. Moreover, treatment with S-1 enhanced secretion of both pro- and mature forms of cathepsin D, coincident with disintegration of trans-Golgi network. Interestingly, S-1 does not induce ferroptosis, pyroptosis or necroptosis in NCI-H1299 cells. However, treatment of NCI-H460 cells with S-1 induces methuosis, which can be suppressed by Rac1 inhibitor EHT 1864. Our data demonstrate that S-1 is an effective anticancer agent with potential therapeutic application.

Mitochondrial Quality Control Processes at the Crossroads of Cell Death and Survival: Mechanisms and Signaling Pathways

Biological aging results from an accumulation of damage in the face of reduced resilience. One major driver of aging is cell senescence, a state in which cells remain viable but lose their proliferative capacity, undergo metabolic alterations, and become resistant to apoptosis. This is accompanied by complex cellular changes that enable the development of a senescence-associated secretory phenotype (SASP). Mitochondria, organelles involved in energy provision and activities essential for regulating cell survival and death, are negatively impacted by aging. The age-associated decline in mitochondrial function is also accompanied by the development of chronic low-grade sterile inflammation. The latter shares some features and mediators with the SASP. Indeed, the unloading of damage-associated molecular patterns (DAMPs) at the extracellular level can trigger sterile inflammatory responses and mitochondria can contribute to the generation of DAMPs with pro-inflammatory properties. The extrusion of mitochondrial DNA (mtDNA) via mitochondrial outer membrane permeabilization under an apoptotic stress triggers senescence programs. Additional pathways can contribute to sterile inflammation. For instance, pyroptosis is a caspase-dependent inducer of systemic inflammation, which is also elicited by mtDNA release and contributes to aging. Herein, we overview the molecular mechanisms that may link mitochondrial dyshomeostasis, pyroptosis, sterile inflammation, and senescence and discuss how these contribute to aging and could be exploited as molecular targets for alleviating the cell damage burden and achieving healthy longevity.

Unlocking the potential of pyroptosis in tumor immunotherapy: a new horizon in cancer treatment

Background

The interaction between pyroptosis-a form of programmed cell death-and tumor immunity represents a burgeoning field of interest. Pyroptosis exhibits a dual role in cancer: it can both promote tumor development and counteract it by activating immune responses that inhibit tumor evasion and encourage cell death. Current tumor immunotherapy strategies, notably CAR-T cell therapy and immune checkpoint inhibitors (ICIs), alongside the potential of certain traditional Chinese medicinal compounds, highlight the intricate relationship between pyroptosis and cancer immunity. As research delves deeper into pyroptosis mechanisms within tumor therapy, its application in enhancing tumor immune responses emerges as a novel research avenue.

Purpose

This review aims to elucidate the mechanisms underlying pyroptosis, its impact on tumor biology, and the advancements in tumor immunotherapy research.

Methods

A comprehensive literature review was conducted across PubMed, Embase, CNKI, and Wanfang Database from the inception of the study until August 22, 2023. The search employed keywords such as "pyroptosis", "cancer", "tumor", "mechanism", "immunity", "gasdermin", "ICB", "CAR-T", "PD-1", "PD-L1", "herbal medicine", "botanical medicine", "Chinese medicine", "traditional Chinese medicine", "immunotherapy", linked by AND/OR, to capture the latest findings in pyroptosis and tumor immunotherapy.

Results

Pyroptosis is governed by a complex mechanism, with the Gasdermin family playing a pivotal role. While promising for tumor immunotherapy application, research into pyroptosis's effect on tumor immunity is still evolving. Notably, certain traditional Chinese medicine ingredients have been identified as potential pyroptosis inducers, meriting further exploration.

Conclusion

This review consolidates current knowledge on pyroptosis's role in tumor immunotherapy. It reveals pyroptosis as a beneficial factor in the immunotherapeutic landscape, suggesting that leveraging pyroptosis for developing novel cancer treatment strategies, including those involving traditional Chinese medicine, represents a forward-looking approach in oncology.

Adipocyte pyroptosis occurs in omental tumor microenvironment and is associated with chemoresistance of ovarian cancer

BACKGROUND

Ovarian carcinoma (OC) is a fatal malignancy, with most patients experiencing recurrence and resistance to chemotherapy. In contrast to hematogenous metastasizing tumors, ovarian cancer cells disseminate within the peritoneal cavity, especially the omentum. Previously, we reported omental crown-like structure (CLS) number is associated with poor prognosis of advanced-stage OC. CLS that have pathologic features of a dead or dying adipocyte was surrounded by several macrophages is well known a histologic hallmark for inflammatory adipose tissue. In this study, we attempted to clarify the interaction between metastatic ovarian cancer cells and omental CLS, and to formulate a therapeutic strategy for advanced-stage ovarian cancer.

METHODS

A three-cell (including OC cells, adipocytes and macrophages) coculture model was established to mimic the omental tumor microenvironment (TME) of ovarian cancer. Caspase-1 activity, ATP and free fatty acids (FFA) levels were detected by commercial kits. An adipocyte organoid model was established to assess macrophages migration and infiltration. In vitro and in vivo experiments were performed for functional assays and therapeutic effect evaluations. Clinical OC tissue samples were collected for immunochemistry stain and statistics analysis.

RESULTS

In three-cell coculture model, OC cells-derived IL-6 and IL-8 could induce the occurrence of pyroptosis in omental adipocytes. The pyroptotic adipocytes release ATP to increase macrophage infiltration, release FFA into TME, uptake by OC cells to increase chemoresistance. From OC tumor samples study, we demonstrated patients with high gasdermin D (GSDMD) expression in omental adipocytes is highly correlated with chemoresistance and poor outcome in advanced-stage OC. In animal model, by pyroptosis inhibitor, DSF, effectively retarded tumor growth and prolonged mice survival.

CONCLUSIONS

Omental adipocyte pyroptosis may contribute the chemoresistance in advanced stage OC. Omental adipocytes could release FFA and ATP through the GSDMD-mediate pyroptosis to induce chemoresistance and macrophages infiltration resulting the poor prognosis in advanced-stage OC. Inhibition of adipocyte pyroptosis may be a potential therapeutic modality in advanced-stage OC with omentum metastasis.

Nanomaterials Enhance Pyroptosis-Based Tumor Immunotherapy

Pyroptosis, a pro-inflammatory and lytic programmed cell death pathway, possesses great potential for antitumor immunotherapy. By releasing cellular contents and a large number of pro-inflammatory factors, tumor cell pyroptosis can promote dendritic cell maturation, increase the intratumoral infiltration of cytotoxic T cells and natural killer cells, and reduce the number of immunosuppressive cells within the tumor. However, the efficient induction of pyroptosis and prevention of damage to normal tissues or cells is an urgent concern to be addressed. Recently, a wide variety of nanoplatforms have been designed to precisely trigger pyroptosis and activate the antitumor immune responses. This review provides an update on the progress in nanotechnology for enhancing pyroptosis-based tumor immunotherapy. Nanomaterials have shown great advantages in triggering pyroptosis by delivering pyroptosis initiators to tumors, increasing oxidative stress in tumor cells, and inducing intracellular osmotic pressure changes or ion imbalances. In addition, the challenges and future perspectives in this field are proposed to advance the clinical translation of pyroptosis-inducing nanomedicines.

Boarding pyroptosis onto nanotechnology for cancer therapy

Pyroptosis, a non-apoptotic programmed cellular inflammatory death mechanism characterized by gasdermin (GSDM) family proteins, has gathered significant attention in the cancer treatment. However, the alarming clinical trial data indicates that pyroptosis-mediated cancer therapeutic efficiency is still unsatisfactory. It is essential to integrate the burgeoning biomedical findings and innovations with potent technology to hasten the development of pyroptosis-based antitumor drugs. Considering the rapid development of pyroptosis-driven cancer nanotherapeutics, here we aim to summarize the recent advances in this field at the intersection of pyroptosis and nanotechnology. First, the foundation of pyroptosis-based nanomedicines (NMs) is outlined to illustrate the reliability and effectiveness for the treatment of tumor. Next, the emerging nanotherapeutics designed to induce pyroptosis are overviewed. Moreover, the cross-talk between pyroptosis and other cell death modalities are discussed, aiming to explore the mechanistic level relationships to provide guidance strategies for the combination of different types of antitumor drugs. Last but not least, the opportunities and challenges of employing pyroptosis-based NMs in potential clinical cancer therapy are highlighted.

Nano-microflora Interaction Inducing Pulmonary Inflammation by Pyroptosis

Antimicrobial nanomaterials frequently induce inflammatory reactions within lung tissues and prompt apoptosis in lung cells, yielding a paradox due to the inherent anti-inflammatory character of apoptosis. This paradox accentuates the elusive nature of the signaling cascade underlying nanoparticle (NP)-induced pulmonary inflammation. In this study, we unveil the pivotal role of nano-microflora interactions, serving as the crucial instigator in the signaling axis of NP-induced lung inflammation. Employing pulmonary microflora-deficient mice, we provide compelling evidence that a representative antimicrobial nanomaterial, silver (Ag) NPs, triggers substantial motility impairment, disrupts quorum sensing, and incites DNA leakage from pulmonary microflora. Subsequently, the liberated DNA molecules recruit caspase-1, precipitating the release of proinflammatory cytokines and activating N-terminal gasdermin D (GSDMD) to initiate pyroptosis in macrophages. This pyroptotic cascade culminates in the emergence of severe pulmonary inflammation. Our exploration establishes a comprehensive mechanistic axis that interlinks the antimicrobial activity of Ag NPs, perturbations in pulmonary microflora, bacterial DNA release, macrophage pyroptosis, and consequent lung inflammation, which helps to gain an in-depth understanding of the toxic effects triggered by environmental NPs.

Oxidative photocatalysis on membranes triggers non-canonical pyroptosis

Intracellular membranes composing organelles of eukaryotes include membrane proteins playing crucial roles in physiological functions. However, a comprehensive understanding of the cellular responses triggered by intracellular membrane-focused oxidative stress remains elusive. Herein, we report an amphiphilic photocatalyst localised in intracellular membranes to damage membrane proteins oxidatively, resulting in non-canonical pyroptosis. Our developed photocatalysis generates hydroxyl radicals and hydrogen peroxides via water oxidation, which is accelerated under hypoxia. Single-molecule magnetic tweezers reveal that photocatalysis-induced oxidation markedly destabilised membrane protein folding. In cell environment, label-free quantification reveals that oxidative damage occurs primarily in membrane proteins related to protein quality control, thereby aggravating mitochondrial and endoplasmic reticulum stress and inducing lytic cell death. Notably, the photocatalysis activates non-canonical inflammasome caspases, resulting in gasdermin D cleavage to its pore-forming fragment and subsequent pyroptosis. These findings suggest that the oxidation of intracellular membrane proteins triggers non-canonical pyroptosis.

Eugenol as a potential adjuvant therapy for gingival squamous cell carcinoma

Adoption of plant-derived compounds for the management of oral cancer is encouraged by the scientific community due to emerging chemoresistance and conventional treatments adverse effects. Considering that very few studies investigated eugenol clinical relevance for gingival carcinoma, we ought to explore its selectivity and performance according to aggressiveness level. For this purpose, non-oncogenic human oral epithelial cells (GMSM-K) were used together with the Tongue (SCC-9) and Gingival (Ca9-22) squamous cell carcinoma lines to assess key tumorigenesis processes. Overall, eugenol inhibited cell proliferation and colony formation while inducing cytotoxicity in cancer cells as compared to normal counterparts. The recorded effect was greater in gingival carcinoma and appears to be mediated through apoptosis induction and promotion of p21/p27/cyclin D1 modulation and subsequent Ca9-22 cell cycle arrest at the G0/G1 phase, in a p53-independent manner. At these levels, distinct genetic profiles were uncovered for both cell lines by QPCR array. Moreover, it seems that our active component limited Ca9-22 and SCC-9 cell migration respectively through MMP1/3 downregulation and stimulation of inactive MMPs complex formation. Finally, Ca9-22 behaviour appears to be mainly modulated by the P38/STAT5/NFkB pathways. In summary, we can disclose that eugenol is cancer selective and that its mediated anti-cancer mechanisms vary according to the cell line with gingival squamous cell carcinoma being more sensitive to this phytotherapy agent.

Quinoxaline derivatives: Recent discoveries and development strategies towards anticancer agents

Cancer is a leading cause of death and a major health problem worldwide. While many effective anticancer agents are available, most drugs currently on the market are not specific, raising issues like the common side effects of chemotherapy. However, recent research hold promises for the development of more efficient and safer anticancer drugs. Quinoxaline and its derivatives are becoming recognized as a novel class of chemotherapeutic agents with activity against different tumors. The present review compiles and discusses studies concerning the therapeutic potential of the anticancer activity of quinoxaline derivatives, covering articles published between January 2018 and January 2023.

Crosstalk between hypoxia-induced pyroptosis and immune escape in cancer: From mechanisms to therapy

Pyroptosis can be triggered through both canonical and non-canonical inflammasome pathways, involving the cleavage of gasdermin (GSDM) protein family members, like GSDMD and GSDME. The impact of pyroptosis on tumors is nuanced, because its role in regulating cancer progression and anti-tumor immunity may vary depending on the tumor type, stage, location, and immune status. However, pyroptosis cannot be simply categorized as promoting or inhibiting tumors based solely on whether it is acute or chronic in nature. The interplay between pyroptosis and cancer is intricate, with some evidence suggesting that chronic pyroptosis may facilitate tumor growth, while the acute induction of pyroptosis could stimulate anti-cancer immune responses. Tumor hypoxia activates hypoxia inducible factor (HIF) signaling to modulate pyroptosis and immune checkpoint expression. Targeting this hypoxia-pyroptosis-immune escape axis could be a promising therapeutic strategy. This review highlights the complex crosstalk between hypoxia, pyroptosis, and immune evasion in the TME.

Mitochondria-Derived Vesicles, Sterile Inflammation, and Pyroptosis in Liver Cancer: Partners in Crime or Innocent Bystanders?

Alterations in cellular signaling, chronic inflammation, and tissue remodeling contribute to hepatocellular carcinoma (HCC) development. The release of damage-associated molecular patterns (DAMPs) upon tissue injury and the ensuing sterile inflammation have also been attributed a role in HCC pathogenesis. Cargoes of extracellular vesicles (EVs) and/or EVs themselves have been listed among circulating DAMPs but only partially investigated in HCC. Mitochondria-derived vesicles (MDVs), a subpopulation of EVs, are another missing link in the comprehension of the molecular mechanisms underlying the onset and progression of HCC biology. EVs have been involved in HCC growth, dissemination, angiogenesis, and immunosurveillance escape. The contribution of MDVs to these processes is presently unclear. Pyroptosis triggers systemic inflammation through caspase-dependent apoptotic cell death and is implicated in tumor immunity. The analysis of this process, together with MDV characterization, may help capture the relationship among HCC development, mitochondrial quality control, and inflammation. The combination of immune checkpoint inhibitors (i.e., atezolizumab and bevacizumab) has been approved as a synergistic first-line systemic treatment for unresectable or advanced HCC. The lack of biomarkers that may allow prediction of treatment response and, therefore, patient selection, is a major unmet need. Herein, we overview the molecular mechanisms linking mitochondrial dysfunction, inflammation, and pyroptosis, and discuss how immunotherapy targets, at least partly, these routes.

New Ca2+ based anticancer nanomaterials trigger multiple cell death targeting Ca2+ homeostasis for cancer therapy

Calcium ion (Ca2+) is a necessary element for human and Ca2+ homeostasis plays important roles in various cellular process and functions. Recent reaches have targeted on inducing Ca2+ overload (both intracellular and transcellular) for tumor therapy. With the development of nanotechnology, nanoplatform-mediated Ca2+ overload has been safe theranostic model for cancer therapy, and defined a special calcium overload-induced tumor cell death as "calcicoptosis". However, the underlying mechanism of calcicoptosis in cancer cells remains further identification. In this review, we summarized multiple cell death types due to Ca2+ overload that induced by novel anticancer nanomaterials in tumor cells, including apoptosis, autophagy, pyroptosis, and ferroptosis. We reviewed the roles of these anticancer nanomaterials on Ca2+ homeostasis, including transcellular Ca2+ influx and efflux, and intracellular Ca2+ change in the cytosolic and organelles, and connection of Ca2+ overload with other metal ions. This review provides the knowledge of these nano-anticancer materials-triggered calcicoptosis accompanied with multiple cell death by regulating Ca2+ homeostasis, which could not only enhance their efficiency and specificity, but also enlighten to design new cancer therapeutic strategies and biomedical applications.

Exploring beyond Common Cell Death Pathways in Oral Cancer: A Systematic Review

Oral squamous cell carcinoma (OSCC) is the most common and lethal type of head and neck cancer in the world. Variable response and acquisition of resistance to traditional therapies show that it is essential to develop novel strategies that can provide better outcomes for the patient. Understanding of cellular and molecular mechanisms of cell death control has increased rapidly in recent years. Activation of cell death pathways, such as the emerging forms of non-apoptotic programmed cell death, including ferroptosis, pyroptosis, necroptosis, NETosis, parthanatos, mitoptosis and paraptosis, may represent clinically relevant novel therapeutic opportunities. This systematic review summarizes the recently described forms of cell death in OSCC, highlighting their potential for informing diagnosis, prognosis and treatment. Original studies that explored any of the selected cell deaths in OSCC were included. Electronic search, study selection, data collection and risk of bias assessment tools were realized. The literature search was carried out in four databases, and the extracted data from 79 articles were categorized and grouped by type of cell death. Ferroptosis, pyroptosis, and necroptosis represented the main forms of cell death in the selected studies, with links to cancer immunity and inflammatory responses, progression and prognosis of OSCC. Harnessing the potential of these pathways may be useful in patient-specific prognosis and individualized therapy. We provide perspectives on how these different cell death types can be integrated to develop decision tools for diagnosis, prognosis, and treatment of OSCC.

Characterization of immunomodulating agents from Staphylococcus aureus for priming immunotherapy in triple-negative breast cancers

Immunotherapy, specifically immune checkpoint blockade (ICB), has revolutionized the treatment paradigm of triple-negative breast cancers (TNBCs). However, a subset of TNBCs devoid of tumor-infiltrating T cells (TILs) or PD-L1 expression generally has a poor response to immunotherapy. In this study, we aimed to sensitize TNBCs to ICB by harnessing the immunomodulating potential of S. aureus, a breast-resident bacterium. We show that intratumoral injection of spent culture media from S. aureus recruits TILs and suppresses tumor growth in a preclinical TNBC model. We further demonstrate that α-hemolysin (HLA), an S. aureus-produced molecule, increases the levels of CD8+ T cells and PD-L1 expression in tumors, delays tumor growth, and triggers tumor necrosis. Mechanistically, while tumor cells treated with HLA display Gasdermin E (GSDME) cleavage and a cellular phenotype resembling pyroptosis, splenic T cells incubated with HLA lead to selective expansion of CD8+ T cells. Notably, intratumoral HLA injection prior to ICB augments the therapeutic efficacy compared to ICB alone. This study uncovers novel immunomodulatory properties of HLA and suggests that intratumoral administration of HLA could be a potential priming strategy to expand the population of TNBC patients who may respond to ICB.

CASP1 is a target for combination therapy in pancreatic cancer

Gemcitabine (GEM) is commonly used as the first-line chemotherapeutic agent for treating pancreatic cancer (PC) patients. However, drug resistance is a major hurdle in GEM-based chemotherapy for PC. Recent studies have shown that pyroptosis, a type of programmed death, plays a significant regulatory role in cancer development and therapy. In this study, we observed an increase in the expression of Caspase-1(CASP1)/Gasdermin-D (GSDMD) in PC and found that high expression of CASP1 and GSDMD was associated with poor overall survival (OS) and progression-free survival (PFS) of PC patients. Knockdown of either CASP1 or GSDMD resulted in the inhibition of cell viability and migration in PC cells. More importantly, the knockdown of CASP1 or GSDMD enhanced GEM-induced cell death in PC cells. Interestingly, subsequent investigations demonstrated that enzymatically active CASP1 promoted GEM-induced cell death in PC cells. The activation of CASP1 by the DPP8/DPP9 inhibitor (Val-boroPro, VbP) increased GEM-induced cell death by inducing pyroptosis. These findings suggest that inhibiting CASP1 to suppress its oncogenic effects or activating it to promote cell pyroptosis both enhance the sensitivity of PC cells to GEM therapy.

Signalling in pancreatic cancer: from pathways to therapy

Pancreatic cancer (PC) is a common malignant tumour in the digestive system. Due to the lack of sensitive diagnostic markers, strong metastasis ability, and resistance to anti-cancer drugs, the prognosis of PC is inferior. In the past decades, increasing evidence has indicated that the development of PC is closely related to various signalling pathways. With the exploration of RAS-driven, epidermal growth factor receptor, Hedgehog, NF-κB, TGF-β, and NOTCH signalling pathways, breakthroughs have been made to explore the mechanism of pancreatic carcinogenesis, as well as the novel therapies. In this review, we discussed the signalling pathways involved in PC and summarised current targeted agents in the treatment of PC. Furthermore, opportunities and challenges in the exploration of potential therapies targeting signalling pathways were also highlighted.

Distinct Types of Cell Death and Implications in Liver Diseases: An Overview of Mechanisms and Application

Cell death is associated with a variety of liver diseases, and hepatocyte death is a core factor in the occurrence and progression of liver diseases. In recent years, new cell death modes have been identified, and certain biomarkers have been detected in the circulation during various cell death modes that mediate liver injury. In this review, cell death modes associated with liver diseases are summarized, including some cell death modes that have emerged in recent years. We described the mechanisms associated with liver diseases and summarized recent applications of targeting cell death in liver diseases. It provides new ideas for the diagnosis and treatment of liver diseases. In addition, multiple cell death modes can contribute to the same liver disease. Different cell death modes are not isolated, and they interact with each other in liver diseases. Future studies may focus on exploring the regulation between various cell death response pathways in liver diseases.

Gasdermin D: A Potential New Auxiliary Pan-Biomarker for the Detection and Diagnosis of Diseases

Pyroptosis is a form of programmed cell death mediated by gasdermins, particularly gasdermin D (GSDMD), which is widely expressed in tissues throughout the body. GSDMD belongs to the gasdermin family, which is expressed in a variety of cell types including epithelial cells and immune cells. It is involved in the regulation of anti-inflammatory responses, leading to its differential expression in a wide range of diseases. In this review, we provide an overview of the current understanding of the major activation mechanisms and effector pathways of GSDMD. Subsequently, we examine the importance and role of GSDMD in different diseases, highlighting its potential as a pan-biomarker. We specifically focus on the biological characteristics of GSDMD in several diseases and its promising role in diagnosis, early detection, and differential diagnosis. Furthermore, we discuss the application of GSDMD in predicting prognosis and monitoring treatment efficacy in cancer. This review proposes a new strategy to guide therapeutic decision-making and suggests potential directions for further research into GSDMD.

A pyroptosis gene-based prognostic model for predicting survival in low-grade glioma

Background

Pyroptosis, a lytic form of programmed cell death initiated by inflammasomes, has been reported to be closely associated with tumor proliferation, invasion and metastasis. However, the roles of pyroptosis genes (PGs) in low-grade glioma (LGG) remain unclear.

Methods

We obtained information for 1,681 samples, including the mRNA expression profiles of LGGs and normal brain tissues and the relevant corresponding clinical information from two public datasets, TCGA and GTEx, and identified 45 differentially expressed pyroptosis genes (DEPGs). Among these DEPGs, nine hub pyroptosis genes (HPGs) were identified and used to construct a genetic risk scoring model. A total of 476 patients, selected as the training group, were divided into low-risk and high-risk groups according to the risk score. The area under the curve (AUC) values of the receiver operating characteristic (ROC) curves verified the accuracy of the model, and a nomogram combining the risk score and clinicopathological characteristics was used to predict the overall survival (OS) of LGG patients. In addition, a cohort from the Gene Expression Omnibus (GEO) database was selected as a validation group to verify the stability of the model. qRT-PCR was used to analyze the gene expression levels of nine HPGs in paracancerous and tumor tissues from 10 LGG patients.

Results

Survival analysis showed that, compared with patients in the low-risk group, patients in the high-risk group had a poorer prognosis. A risk score model combining PG expression levels with clinical features was considered an independent risk factor. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated that immune-related genes were enriched among the DEPGs and that immune activity was increased in the high-risk group.

Conclusion

In summary, we successfully constructed a model to predict the prognosis of LGG patients, which will help to promote individualized treatment and provide potential new targets for immunotherapy.

The 'speck'-tacular oversight of the NLRP3-pyroptosis pathway on gastrointestinal inflammatory diseases and tumorigenesis

The NLRP3 inflammasome is an intracellular sensor and an essential component of the innate immune system involved in danger recognition. An important hallmark of inflammasome activation is the formation of a single supramolecular punctum, known as a speck, per cell, which is the site where the pro-inflammatory cytokines IL-1β and IL-18 are converted into their bioactive form. Speck also provides the platform for gasdermin D protein activation, whose N-terminus domain perforates the plasma membrane, allowing the release of mature cytokines alongside with a highly inflammatory form of cell death, namely pyroptosis. Although controlled NLRP3 inflammasome-pyroptosis pathway activation preserves mucosal immunity homeostasis and contributes to host defense, a prolonged trigger is deleterious and could lead, in genetically predisposed subjects, to the onset of inflammatory bowel disease, including Crohn's disease and ulcerative colitis, as well as to gastrointestinal cancer. Experimental evidence shows that the NLRP3 inflammasome has both protective and pathogenic abilities. In this review we highlight the impact of the NLRP3-pyroptosis axis on the pathophysiology of the gastrointestinal tract at molecular level, focusing on newly discovered features bearing pro- and anti-inflammatory and neoplastic activity, and on targeted therapies tested in preclinical and clinical trials.

Engineered Bacteria Labeled with Iridium(III) Photosensitizers for Enhanced Photodynamic Immunotherapy of Solid Tumors

Despite metal-based photosensitizers showing great potential in photodynamic therapy for tumor treatment, the application of the photosensitizers is intrinsically limited by their poor cancer-targeting properties. Herein, we reported a metal-based photosensitizer-bacteria hybrid, Ir-HEcN, via covalent labeling of an iridium(III) photosensitizer to the surface of genetically engineered bacteria. Due to its intrinsic self-propelled motility and hypoxia tropism, Ir-HEcN selectively targets and penetrates deeply into tumor tissues. Importantly, Ir-HEcN is capable of inducing pyroptosis and immunogenic cell death of tumor cells under irradiation, thereby remarkably evoking anti-tumor innate and adaptive immune responses in vivo and leading to the regression of solid tumors via combinational photodynamic therapy and immunotherapy. To the best of our knowledge, Ir-HEcN is the first metal complex decorated bacteria for enhanced photodynamic immunotherapy.

The role of novel programmed cell death in head and neck squamous cell carcinoma: from mechanisms to potential therapies

Head and neck squamous cell carcinoma (HNSCC) is a common oral cancer with poor prognosis and for which no targeted therapeutic strategies are currently available. Accumulating evidence has demonstrated that programmed cell death (PCD) is essential in the development of HNSCC as a second messenger. PCD can be categorized into numerous different subroutines: in addition to the two well-known types of apoptosis and autophagy, novel forms of programmed cell death (e.g., necroptosis, pyroptosis, ferroptosis, and NETosis) also serve as key alternatives in tumorigenesis. Cancer cells are not able to avoid all types of cell death simultaneously, since different cell death subroutines follow different regulatory pathways. Herein, we summarize the roles of novel programmed cell death in tumorigenesis and present our interpretations of the molecular mechanisms with a view to the development of further potential therapies.

Molecular mechanisms of pyroptosis and its role in anti-tumor immunity

Pyroptosis is a form of cell death that is characterized by the destruction of the cell, and it has implications in both the immune system and cancer immunotherapy. The gasdermin family is responsible for the activation of pyroptosis, which involves the formation of pores in the cellular membrane that permit the discharge of inflammatory factors. The inflammasome response is a powerful mechanism that helps to eliminate bacteria and cancer cells when cellular damage occurs. As tumor cells become more resilient to apoptosis, other treatments for cancer are becoming more popular. It is essential to gain a thorough understanding of pyroptosis in order to use it in cancer treatment, considering the intricate association between pyroptosis and the immune system's defensive reaction against tumors. This review offers an overview of the mechanisms of pyroptosis, the relationship between the gasdermin family and pyroptosis, and the interplay between pyroptosis and anti-tumor immunity. In addition, the potential implications of pyroptosis in cancer immunotherapy are discussed. Additionally, we explore future research possibilities and introduce a novel approach to tumor treatment.

mRNA lipid nanoparticle-mediated pyroptosis sensitizes immunologically cold tumors to checkpoint immunotherapy

Synergistically improving T-cell responsiveness is promising for favorable therapeutic outcomes in immunologically cold tumors, yet current treatments often fail to induce a cascade of cancer-immunity cycle for effective antitumor immunity. Gasdermin-mediated pyroptosis is a newly discovered mechanism in cancer immunotherapy; however, cleavage in the N terminus is required to activate pyroptosis. Here, we report a single-agent mRNA nanomedicine-based strategy that utilizes mRNA lipid nanoparticles (LNPs) encoding only the N-terminus of gasdermin to trigger pyroptosis, eliciting robust antitumor immunity. In multiple female mouse models, we show that pyroptosis-triggering mRNA/LNPs turn cold tumors into hot ones and create a positive feedback loop to promote antitumor immunity. Additionally, mRNA/LNP-induced pyroptosis sensitizes tumors to anti-PD-1 immunotherapy, facilitating tumor growth inhibition. Antitumor activity extends beyond the treated lesions and suppresses the growth of distant tumors. We implement a strategy for inducing potent antitumor immunity, enhancing immunotherapy responses in immunologically cold tumors.

Lymphocyte infiltration and antitumoral effect promoted by cytotoxic inflammatory proteins formulated as self-assembling, protein-only nanoparticles

Two human proteins involved in the inflammatory cell death, namely Gasdermin D (GSDMD) and the Mixed Lineage Kinase Domain-Like (MLKL) protein have been engineered to accommodate an efficient ligand of the tumoral cell marker CXCR4, and a set of additional peptide agents that allow their spontaneous self-assembling. Upon production in bacterial cells and further purification, both proteins organized as stable nanoparticles of 46 and 54 nm respectively, that show, in this form, a moderate but dose-dependent cytotoxicity in cell culture. In vivo, and when administered in mouse models of colorectal cancer through repeated doses, the nanoscale forms of tumor-targeted GSDMD and, at a lesser extent, of MLKL promoted CD8⁺ and CD20⁺ lymphocyte infiltration in the tumor and an important reduction of tumor size, in absence of systemic toxicity. The potential of these novel pharmacological agents as anticancer drugs is discussed in the context of synergistic approaches to more effective cancer treatments.

Pyroptosis-related lncRNA prognostic signatures for cutaneous melanoma and tumor microenvironment status

Aims: To explore whether the expression of pyroptosis-related lncRNAs makes a difference in the prognosis and antitumor immunity of cutaneous melanoma (CM) patients. Methods: A series of analyses were conducted to establish a prognostic risk model and validate its accuracy. Immune-related analyses were performed to further assess the associations among immune status, tumor microenvironment and the prognostic risk model. Results: Eight pyroptosis-related lncRNAs relevant to prognosis were ascertained and applied to establish the prognostic risk model. The low-risk group had a higher overall survival rate. Conclusion: The established prognostic risk model presents better prediction ability for the prognosis of CM patients and provides new possible therapeutic targets for CM.

Aryl-functionalised α,α'-Trehalose 6,6'-Glycolipid Induces Mincle-independent Pyroptotic Cell Death

α,α'-Trehalose 6,6'-glycolipids have long been known for their immunostimulatory properties. The adjuvanticity of α,α'-trehalose 6,6'-glycolipids is mediated by signalling through the macrophage inducible C-type lectin (Mincle) and the induction of an inflammatory response. Herein, we present an aryl-functionalised trehalose glycolipid, AF-2, that leads to the release of cytokines and chemokines, including IL-6, MIP-2 and TNF-α, in a Mincle-dependent manner. Furthermore, plate-coated AF-2 also leads to the Mincle-independent production of IL-1β, which is unprecedented for this class of glycolipid. Upon investigation into the mode of action of plate-coated AF-2, it was observed that the treatment of WT and Mincle^-/- bone marrow derived macrophages (BMDM), murine RAW264.7 cells, and human monocytes with AF-2 led to lytic cell death, as evidenced using Sytox Green and lactate dehydrogenase assays, and confocal and scanning electron microscopy. The requirement for functional Gasdermin D and Caspase-1 for IL-1β production and cell death by AF-2 confirmed pyroptosis as the mode of action of AF-2. The inhibition of NLRP3 and K⁺ efflux reduced AF-2 mediated IL-1β production and cell death, and allowed us to conclude that AF-2 leads to Capase-1 dependent NLRP3 inflammasome-mediated cell death. The unique mode of action of plate-coated AF-2 was surprising and highlights how the physical presentation of Mincle ligands can lead to dramatically different immunological outcomes.

Resisting T cell attack: tumor-cell-intrinsic defense and reparation mechanisms

Cytotoxic T lymphocytes (CTLs) are antigen-specific killer cells equipped to identify and eliminate host cells that have been altered through infection or transformation. Both chimeric antigen-receptor (CAR) T cell therapies and immune checkpoint blockade (ICB) therapies are based on successful elimination of tumor cells by cytotoxic effectors. In this opinion article, we outline cell-intrinsic mechanisms by which tumor cells defend against CTLs, highlighting pathways that confer resistance and proposing opportunities for combination therapies. We discuss how exogenous killing entities [e.g., supramolecular attack particles (SMAPs)] offer a novel strategy to circumvent cellular resistance mechanisms. Our opinion article highlights the importance of identifying, quantifying, and targeting tumor defense mechanisms at the interface between tumor cells and CTLs as a critical consideration in the development of immunotherapy approaches.

A novel risk score model based on pyroptosis-related genes for predicting survival and immunogenic landscape in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the third leading cause of cancer worldwide, with high incidence and mortality. Pyroptosis, a form of inflammatory-regulated cell death, is closely associated with oncogenesis.

METHODS

Expression profiles of HCC were downloaded from the TCGA database and validated using the ICGC and GEO databases. Consensus clustering analysis was used to determine distinct clusters. The pyroptosis-related genes (PRGs) included in the pyroptosis-related signature were selected by univariate Cox regression and LASSO regression analysis. Kaplan-Meier and receiver operating characteristic (ROC) analyses were performed to estimate the prognostic potential of the model. The characteristics of infiltration of immune cells between different groups of HCC were explored.

RESULTS

Two independent clusters were identified according to PRG expression. Cluster 2 showed upregulated expression, poor prognosis, increased immune cell infiltration and worse immunotherapy response than cluster 1. A prognostic risk signature consisting of five genes (GSDME, NOD1, PLCG1, NLRP6 and NLRC4) was identified. In the high-risk score group, HCC patients showed decreased survival rates. In particular, multiple clinicopathological characteristics and immune cell infiltration were significantly associated with the risk score. Notably, the 5 PRGs in the risk score have been implicated in carcinogenesis, immunological pathways and drug sensitivity.

CONCLUSIONS

A prognostic signature comprising five PRGs can be used as a potential prognostic factor for HCC. The PRG-related signature provides an in-depth understanding of the association between pyroptosis and chemotherapy or immunotherapy for HCC patients.

Identification of Pyroptosis-Relevant Signature in Tumor Immune Microenvironment and Prognosis in Skin Cutaneous Melanoma Using Network Analysis

Background

Pyroptosis is closely related to the programmed death of cancer cells as well as the tumor immune microenvironment (TIME) via the host-tumor crosstalk. However, the role of pyroptosis-related genes as prognosis and TIME-related biomarkers in skin cutaneous melanoma (SKCM) patients remains unknown.

Methods

We evaluated the expression profiles, copy number variations, and somatic mutations (CNVs) of 27 genes obtained from MSigDB database regulating pyroptosis among TCGA-SKCM patients. Thereafter, we conducted single-sample gene set enrichment analysis (ssGSEA) for evaluating pyroptosis-associated expression patterns among cases and for exploring the associations with clinicopathological factors and prognostic outcome. In addition, a prognostic pyroptosis-related signature (PPRS) model was constructed by performing Cox regression, weighted gene coexpression network analysis (WGCNA), and least absolute shrinkage and selection operator (LASSO) analysis to score SKCM patients. On the other hand, we plotted the ROC and survival curves for model evaluation and verified the robustness of the model through external test sets (GSE22153, GSE54467, and GSE65904). Meanwhile, we examined the relations of clinical characteristics, oncogene mutations, biological processes (BPs), tumor stemness, immune infiltration degrees, immune checkpoints (ICs), and treatment response with PPRS via multiple methods, including immunophenoscore (IPS) analysis, gene set variation analysis (GSVA), ESTIMATE, and CIBERSORT. Finally, we constructed a nomogram incorporating PPRS and clinical characteristics to improve risk evaluation of SKCM.

Results

Many pyroptosis-regulated genes showed abnormal expression within SKCM. TP53, TP63, IL1B, IL18, IRF2, CASP5, CHMP4C, CHMP7, CASP1, and GSDME were detected with somatic mutations, among which, a majority displayed CNVs at high frequencies. Pyroptosis-associated profiles established based on pyroptosis-regulated genes showed markedly negative relation to low stage and superior prognostic outcome. Blue module was found to be highly positively correlated with pyroptosis. Later, this study established PPRS based on the expression of 8 PAGs (namely, GBP2, HPDL, FCGR2A, IFITM1, HAPLN3, CCL8, TRIM34, and GRIPAP1), which was highly associated with OS, oncogene mutations, tumor stemness, immune infiltration degrees, IC levels, treatment responses, and multiple biological processes (including cell cycle and immunoinflammatory response) in training and test set samples.

Conclusions

Based on our observations, analyzing modification patterns associated with pyroptosis among diverse cancer samples via PPRS is important, which can provide more insights into TIME infiltration features and facilitate immunotherapeutic development as well as prognosis prediction.

Crosstalk among N6-methyladenosine modification and RNAs in central nervous system injuries

Central nervous system (CNS) injuries, including traumatic brain injury (TBI), intracerebral hemorrhage (ICH) and ischemic stroke, are the most common cause of death and disability around the world. As the most common modification on ribonucleic acids (RNAs), N6-methyladenosine (m6A) modification has recently attracted great attentions due to its functions in determining the fate of RNAs through changes in splicing, translation, degradation and stability. A large number of studies have suggested that m6A modification played an important role in brain development and involved in many neurological disorders, particularly in CNS injuries. It has been proposed that m6A modification could improve neurological impairment, inhibit apoptosis, suppress inflammation, reduce pyroptosis and attenuate ferroptosis in CNS injuries via different molecules including phosphatase and tensin homolog (PTEN), NLR family pyrin domain containing 3 (NLRP3), B-cell lymphoma 2 (Bcl-2), glutathione peroxidase 4 (GPX4), and long non-coding RNA (lncRNA). Therefore, m6A modification showed great promise as potential targets in CNS injuries. In this article, we present a review highlighting the role of m6A modification in CNS injuries. Hence, on the basis of these properties and effects, m6A modification may be developed as therapeutic agents for CNS injury patients.

Sinapic Acid Alleviates Acute Pancreatitis in Association with Attenuation of Inflammation, Pyroptosis, and the AMPK/NF-κB Signaling Pathway

Among the diseases of the digestive system, the incidence of acute pancreatitis (AP) has increased. Although the AP is primarily self-limited, mortality remains high when it progressed to severe acute pancreatitis (SAP). Despite significant advances in new drug development, treatments for AP are not ideal. Here, we discovered a novel hydroxycinnamic acid, sinapic acid (SA), which is widely distributed in plants and is an effective treatment for AP. Using in vitro and in vivo models, we demonstrated that pretreatment with SA ameliorated cerulein-induced pancreatic damage and inflammation and inhibited the activation of Caspase-1 and Caspase-11, which mediate pyroptosis of pancreatic acinar cells during AP. These effects may occur through the inhibition of AMPK phosphorylation and downregulation of NF-[Formula: see text]B. Our findings demonstrate the therapeutic effects and reveal the underlying mechanisms of SA, which warrants its further study as an effective treatment for AP.