Gasdermins deliver a deadly punch to cancer

The application of nanoparticles-based ferroptosis, pyroptosis and autophagy in cancer immunotherapy

Immune checkpoint blockers (ICBs) have been applied for cancer therapy and achieved great success in the field of cancer immunotherapy. Nevertheless, the broad application of ICBs is limited by the low response rate. To address this issue, increasing studies have found that the induction of immunogenic cell death (ICD) in tumor cells is becoming an emerging therapeutic strategy in cancer treatment, not only straightly killing tumor cells but also enhancing dying cells immunogenicity and activating antitumor immunity. ICD is a generic term representing different cell death modes containing ferroptosis, pyroptosis, autophagy and apoptosis. Traditional chemotherapeutic agents usually inhibit tumor growth based on the apoptotic ICD, but most tumor cells are resistant to the apoptosis. Thus, the induction of non-apoptotic ICD is considered to be a more efficient approach for cancer therapy. In addition, due to the ineffective localization of ICD inducers, various types of nanomaterials have been being developed to achieve targeted delivery of therapeutic agents and improved immunotherapeutic efficiency. In this review, we briefly outline molecular mechanisms of ferroptosis, pyroptosis and autophagy, as well as their reciprocal interactions with antitumor immunity, and then summarize the current progress of ICD-induced nanoparticles based on different strategies and illustrate their applications in the cancer therapy.

Role of GSDM family members in airway epithelial cells of lung diseases: a systematic and comprehensive transcriptomic analysis

Gasdermin (GSDM) family, the key executioners of pyroptosis, play crucial roles in anti-pathogen and anti-tumor immunities, although little is known about the expression of GSDM in lung diseases at single-cell resolution, especially in lung epithelial cells. We comprehensively investigated the transcriptomic profiles of GSDM members in various lung tissues from healthy subjects or patients with different lung diseases at single cell level, e.g., chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), lung adenocarcinoma (LUAD), or systemic sclerosis (SSC). The expression of GSDM members varied among pulmonary cell types (immune cells, structural cells, and especially epithelial cells) and even across lung diseases. Regarding disease-associated specificities, we found that GSDMC or GSDMD altered significantly in ciliated epithelia of COPD or LUAD, GSDMD in mucous, club, and basal cells of LUAD and GSDMC in mucous epithelia of para-tumor tissue, as compared with the corresponding epithelia of other diseases. The phenomic specificity of GSDM in lung cancer subtypes was noticed by comparing with 15 non-pulmonary cancers and para-cancer samples. GSDM family gene expression changes were also observed in different lung epithelial cell lines (e.g., HBE, A549, H1299, SPC-1, or H460) in responses to external challenges, including lipopolysaccharide (LPS), lysophosphatidylcholine (lysoPC), cigarette smoking extract (CSE), cholesterol, and AR2 inhibitor at various doses or durations. GSDMA is rarely expressed in those cell lines, while GSDMB and GSDMC are significantly upregulated in human lung epithelia. Our data indicated that the heterogeneity of GSDM member expression exists at different cells, pathologic conditions, challenges, probably dependent upon cell biological phenomes, functions, and behaviors, upon cellular responses to external changes, and the nature and severity of lung disease. Thus, the deep exploration of GSDM phenomes may provide new insights into understanding the single-cell roles in the tissue, regulatory roles of the GSDM family in the pathogenesis, and potential values of biomarker identification and development.

The role of pyroptosis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the main histologic type of liver cancer. It accounts for the majority of all diagnoses and deaths due to liver cancer. The induction of tumor cell death is an effective strategy to control tumor development. Pyroptosis is an inflammatory programmed cell death caused by microbial infection, accompanied by activation of inflammasomes and release of pro-inflammatory cytokines, interleukin-1β (IL-1β), and interleukin-18 (IL-18). The cleavage of gasdermins (GSDMs) promotes the occurrence of pyroptosis leading to cell swelling, lysis, and death. Accumulating evidence has indicated that pyroptosis influences the progression of HCC by regulating immune-mediated tumor cell death. Currently, some researchers hold the view that inhibition of pyroptosis-related components may prevent the incidence of HCC, but more researchers have the view that activation of pyroptosis exerts a tumor-inhibitory effect. Growing evidence indicates that pyroptosis can prevent or promote tumor development depending on the type of tumor. In this review, pyroptosis pathways and pyroptosis-related components were discussed. Next, the role of pyroptosis and its components in HCC was described. Finally, the therapeutic significance of pyroptosis in HCC was discussed.

Stepwise Size Shrinkage Cascade-Activated Supramolecular Prodrug Boosts Antitumor Immunity by Eliciting Pyroptosis

Effective pyroptosis induction is a promising approach to potentiate cancer immunotherapy. However, the actual efficacy of the present pyroptosis inducers can be weakened by successive biological barriers. Here, a cascaded pH-activated supramolecular nanoprodrug (PDNP) with a stepwise size shrinkage property is developed as a pyroptosis inducer to boost antitumor immune response. PDNPs comprise multiple poly(ethylene glycol) (PEG) and doxorubicin (DOX) drug-polymer hybrid repeating blocks conjugated by ultra-pH-sensitive benzoic imine (bzi) and hydrazone (hyd) bonds. The PEG units endow its "stealth" property and ensure sufficient tumor accumulation. A sharp switch in particle size and detachment of PEG shielding can be triggered by the acidic extracellular pH to achieve deep intratumor penetration. Following endocytosis, second-stage size switching can be initiated by more acidic endolysosomes, and PDNPs disassociate into ultrasmall cargo to ensure accurate intracellular delivery. The cascaded pH activation of PDNPs can effectively elicit gasdermin E (GSDME)-mediated pyroptosis to enhance the immunological response. In combination with anti-PD-1 antibody, PDNPs can amplify tumor suppression and extend the survival of mice, which suggests a powerful immune adjuvant and pave the way for high-efficiency immune checkpoint blockade therapy.

Immunogenic Cell Death and Role of Nanomaterials Serving as Therapeutic Vaccine for Personalized Cancer Immunotherapy

Immunogenic cell death (ICD) is a rapidly growing research area representing one of the emerging therapeutic strategies of cancer immunotherapy. ICD is an umbrella term covering several cell death modalities including apoptosis, necroptosis, ferroptosis and pyroptosis, and is the product of a balanced combination of adjuvanticity (damage-associated molecular patterns and chemokines/cytokines) and antigenicity (tumor associated antigens). Only a limited number of anti-cancer therapies are available to induce ICD in experimental cancer therapies and even much less is available for clinical use. To overcome this limitation, nanomaterials can be used to increase the immunogenicity of cancer cells killed by anti-cancer therapy, which in themselves are not necessarily immunogenic. In this review, we outline the current state of knowledge of ICD modalities and discuss achievements in using nanomaterials to increase the immunogenicity of dying cancer cells. The emerging trends in modulating the immunogenicity of dying cancer cells in experimental and translational cancer therapies and the challenges facing them are described. In conclusion, nanomaterials are expected to drive further progress in their use to increase efficacy of anti-cancer therapy based on ICD induction and in the future, it is necessary to validate these strategies in clinical settings, which will be a challenging research area.

Pyroptosis: Mechanisms and Links with Fibrosis

Fibrosis is responsible for approximately 45% of deaths in the industrialized world and has been a major global healthcare burden. Excessive fibrosis is the primary cause of organ failure. However, there are currently no approved drugs available for the prevention or treatment of fibrosis-related diseases. It has become evident that fibrosis is characterized by inflammation. In a large number of studies of various organs in mice and humans, pyroptosis has been found to play a significant role in fibrosis. Pyroptosis is a form of programmed cell death mediated by the N-terminal fragment of cysteinyl aspartate-specific proteinase (caspase)-1-cleaved gasdermin D (GSDMD, producing GSDMD-N) that gives rise to inflammation via the release of some proinflammatory cytokines, including IL-1β, IL-18 and HMGB1. These cytokines can initiate the activation of fibroblasts. Inflammasomes, an important factor upstream of GSDMD, can activate caspase-1 to trigger the maturation of IL-1β and IL-18. Moreover, the inhibition of inflammasomes, proinflammatory cytokines and GSDMD can prevent the progression of fibrosis. This review summarizes the growing evidence indicating that pyroptosis triggers fibrosis, and highlights potential novel targets for antifibrotic therapies.

Inflammation-related pyroptosis, a novel programmed cell death pathway, and its crosstalk with immune therapy in cancer treatment

In recent decades, chemotherapies targeting apoptosis have emerged and demonstrated remarkable achievements. However, emerging evidence has shown that chemoresistance is mediated by impairing or bypassing apoptotic cell death. Several novel types of programmed cell death, such as ferroptosis, necroptosis, and pyroptosis, have recently been reported to play significant roles in the modulation of cancer progression and are considered a promising strategy for cancer treatment. Thus, the switch between apoptosis and pyroptosis is also discussed. Cancer immunotherapy has gained increasing attention due to breakthroughs in immune checkpoint inhibitors; moreover, ferroptosis, necroptosis, and pyroptosis are highly correlated with the modulation of immunity in the tumor microenvironment. Compared with necroptosis and ferroptosis, pyroptosis is the primary mechanism for host defense and is crucial for bridging innate and adaptive immunity. Furthermore, recent evidence has demonstrated that pyroptosis exerts benefits on cancer immunotherapies, including immune checkpoint inhibitors (ICIs) and chimeric antigen receptor T-cell therapy (CAR-T). Hence, in this review, we elucidate the role of pyroptosis in cancer progression and the modulation of immunity. We also summarize the potential small molecules and nanomaterials that target pyroptotic cell death mechanisms and their therapeutic effects on cancer.

Cell biology of inflammasome activation

Organelles are critical structures in mediating the assembly and activation of inflammasomes in mammalian cells, resulting in inflammation and cell death. Assembly of inflammasomes can occur at the mitochondria, endoplasmic reticulum, nucleus, trans-Golgi network, or pathogen surface, facilitated by the overarching architecture of the cytoskeleton. NLRP3 and Pyrin inflammasome sensors may form smaller speckles and converge on a single larger speck at the microtubule-organizing center (MTOC). This signaling hub activates multiple mammalian inflammatory and apoptotic caspases, cytokine substrates, the pore-forming protein gasdermin D, and the plasma membrane rupture protein ninjurin-1 (NINJ1), allowing pyroptosis, cellular disintegration, and inflammation to ensue. In this review, we highlight the role of mammalian cell types and organellar architectures in executing inflammasome responses.

Role of pyroptosis in diabetic retinopathy and its therapeutic implications

Pyroptosis has recently been established as a term of programmed-inflammatory cell death. Pyroptosis is mainly divided into two molecular signaling pathways, including caspase-1-dependent canonical and caspase-4/5/11-dependent non-canonical inflammasome pathways. Extensive investigations have reported inflammasome activation facilitates the maturation and secretion of the inflammatory factors interleukin-1β/18 (IL-1β/18), cleavage of gasdermin D (GSDMD), and leading to the stimulation of pyroptosis-mediated cell death. Furthermore, accumulating studies report NLRP3 inflammasome activation plays a significant role in triggering the pyroptosis-mediated cell death and promotes the pathogenesis of diabetic retinopathy (DR). Our current review elaborates on the molecular mechanisms of pyroptosis-signaling pathways and their potential roles in the pathogenesis and impact of DR development. We also emphasize several investigational molecules regulating key steps in pyroptotic-cell death to create new comprehensions and findings to explore the pathogenesis of DR advancement. Our narrative review concisely suggests these potential pharmacological agents could be promising therapies to treat and manage DR in the future.

Natural Products as Inducers of Non-Canonical Cell Death: A Weapon against Cancer

Simple Summary

Anticancer therapeutic approaches based solely on apoptosis induction are often unsuccessful due to the activation of resistance mechanisms. The identification and characterization of compounds capable of triggering non-apoptotic, also called non-canonical cell death pathways, could represent an important strategy that may integrate or offer alternative approaches to the current anticancer therapies. In this review, we critically discuss the promotion of ferroptosis, necroptosis, and pyroptosis by natural compounds as a new anticancer strategy.

Abstract

Apoptosis has been considered the main mechanism induced by cancer chemotherapeutic drugs for a long time. This paradigm is currently evolving and changing, as increasing evidence pointed out that antitumor agents could trigger various non-canonical or non-apoptotic cell death types. A considerable number of antitumor drugs derive from natural sources, both in their naturally occurring form or as synthetic derivatives. Therefore, it is not surprising that several natural compounds have been explored for their ability to induce non-canonical cell death. The aim of this review is to highlight the potential antitumor effects of natural products as ferroptosis, necroptosis, or pyroptosis inducers. Natural products have proven to be promising non-canonical cell death inducers, capable of overcoming cancer cells resistance to apoptosis. However, as discussed in this review, they often lack a full characterization of their antitumor activity together with an in-depth investigation of their toxicological profile.

Targeting immunogenic cancer cell death by photodynamic therapy: past, present and future

The past decade has witnessed major breakthroughs in cancer immunotherapy. This development has been largely motivated by cancer cell evasion of immunological control and consequent tumor resistance to conventional therapies. Immunogenic cell death (ICD) is considered one of the most promising ways to achieve total tumor cell elimination. It activates the T-cell adaptive immune response and results in the formation of long-term immunological memory. ICD can be triggered by many anticancer treatment modalities, including photodynamic therapy (PDT). In this review, we first discuss the role of PDT based on several classes of photosensitizers, including porphyrins and non-porphyrins, and critically evaluate their potential role in ICD induction. We emphasize the emerging trend of ICD induction by PDT in combination with nanotechnology, which represents third-generation photosensitizers and involves targeted induction of ICD by PDT. However, PDT also has some limitations, including the reduced efficiency of ICD induction in the hypoxic tumor microenvironment. Therefore, we critically evaluate strategies for overcoming this limitation, which is essential for increasing PDT efficiency. In the final part, we suggest several areas for future research for personalized cancer immunotherapy, including strategies based on oxygen-boosted PDT and nanoparticles. In conclusion, the insights from the last several years increasingly support the idea that PDT is a powerful strategy for inducing ICD in experimental cancer therapy. However, most studies have focused on mouse models, but it is necessary to validate this strategy in clinical settings, which will be a challenging research area in the future.