Necroptosis: an alternative cell death program defending against cancer

Therapeutic effects of exendin-4 on spinal cord injury via restoring autophagy function and decreasing necroptosis in neuron

AIMS

Necroptosis is one of programmed death that may aggravate spinal cord injury (SCI). We aimed to investigate the effect and mechanism of exendin-4 (EX-4) on the recovery of motor function and necroptosis after SCI.

METHODS

The SD rats with left hemisection in the T10 spinal cord as SCI model were used. The behavior tests were measured within 4 weeks. The effects of EX-4 on necroptosis-associated proteins and autophagy flux were explored. In addition, the SHSY5Y cell model was introduced to explore the direct effect of EX-4 on neurons. The effect of lysosome was explored using mTOR activator and AO staining.

RESULTS

EX-4 could improve motor function and limb strength, promote the recovery of autophagy flux, and accelerate the degradation of necroptosis-related protein at 3 d after injury in rats. EX-4 reduced lysosome membrane permeability, promoted the recovery of lysosome function and autophagy flux, and accelerated the degradation of necroptosis-related proteins by inhibiting the phosphorylation level of mTOR in the SHSY5Y cell model.

CONCLUSION

Our results demonstrated that EX-4 may improve motor function after SCI via inhibiting mTOR phosphorylation level and accelerating the degradation of necroptosis-related proteins in neurons. Our findings may provide new therapeutic targets for clinical treatment after SCI.

Human adipose-derived stem cells genetically programmed to induce necroptosis for cancer immunotherapy

Herein, we present human adipose-derived stem cells (ADSCs) inserted with the receptor-interacting protein kinase-3 (RIP3) gene (RP@ADSCs), which induces cell necroptosis, for tumor immunotherapy. Necroptosis has characteristics of both apoptosis, such as programmed cell death, and necrosis, such as swelling and plasma membrane rupture, during which damage-related molecular patterns are released, triggering an immune response. Therefore, necroptosis has the potential to be used as an effective anticancer immunotherapy. RP@ADSCs were programmed to necroptosis after a particular time after being injected in vivo, and various pro-inflammatory cytokines secreted during the stem cell death process stimulated the immune system, showing local and sustained anticancer effects. It was confirmed that RIP3 protein expression increased in ADSCs after RP transfection. RP@ADSCs continued to induce ADSCs death for 7 days, and various pro-inflammatory cytokines were secreted through ADSCs death. The efficacy of RP@ADSCs-mediated immunotherapy was evaluated in mouse models bearing GL-26 (glioblastoma) and K1735 (melanoma), and it was found that RP resulted in an increase in the population of long-term cytotoxic T cells and a decrease in the population of regulatory T cells. This shows that RP@ADSCs have potential and applicability as an excellent anticancer immunotherapy agent in clinical practice.

Identification of necroptosis-related gene signatures for predicting the prognosis of ovarian cancer

Ovarian cancer (OC) is one of the most prevalent and fatal malignant tumors of the female reproductive system. Our research aimed to develop a prognostic model to assist inclinical treatment decision-making.Utilizing data from The Cancer Genome Atlas (TCGA) and copy number variation (CNV) data from the University of California Santa Cruz (UCSC) database, we conducted analyses of differentially expressed genes (DEGs), gene function, and tumor microenvironment (TME) scores in various clusters of OC samples.Next, we classified participants into low-risk and high-risk groups based on the median risk score, thereby dividing both the training group and the entire group accordingly. Overall survival (OS) was significantly reduced in the high-risk group, and two independent prognostic factors were identified: age and risk score. Additionally, three genes-C-X-C Motif Chemokine Ligand 10 (CXCL10), RELB, and Caspase-3 (CASP3)-emerged as potential candidates for an independent prognostic signature with acceptable prognostic value. In Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, pathways related to immune responses and inflammatory cell chemotaxis were identified. Cellular experiments further validated the reliability and precision of our findings. In conclusion, necroptosis-related genes play critical roles in tumor immunity, and our model introduces a novel strategy for predicting the prognosis of OC patients.

Excessive intragastric alcohol administration exacerbates hepatic encephalopathy and provokes neuronal cell death in male rats with chronic liver disease

Hepatic encephalopathy (HE) is defined as decline in neurological function during chronic liver disease (CLD). Alcohol is a major etiological factor in the pathogenesis of fibrosis/cirrhosis and has also been documented to directly impact the brain. However, the role of alcohol in the development of HE in CLD remains unclear. Here, we investigated the impact of excessive alcohol administration on neurological deterioration in rats with CLD. Starting day 7 post-BDL surgery, rats were administered alcohol twice daily (51% v/v ethanol, 3 g/kg, via gavage) for 4 weeks. Motor coordination was assessed weekly using rotarod and anxiety-like behavior was evaluated with open field and elevated plus maze at 5 weeks. Upon sacrifice, brains were collected for western blot and immunohistochemical analyses to investigate neuronal integrity and oxidative stress status. Alcohol worsened motor coordination performance and increased anxiety-like behavior in BDL rats. Impairments were associated with decreased neuronal markers of NeuN and SMI311, increased apoptotic markers of cleaved/pro-caspase-3 and Bax/Bcl2, increased necroptosis markers of pRIP3 and pMLKL, decreased total antioxidant capacity (TAC), and increased 4-hydroxynonenal (4-HNE)modified proteins in the cerebellum of BDL-alcohol rats when compared to respective controls. Immunofluorescence confirmed the colocalization of cleaved caspase-3 and pMLKL in the granular neurons of the cerebellum of BDL-alcohol rats. Excessive alcohol consumption exacerbates HE which leads to associated apoptotic and necroptotic neuronal loss in the cerebellum of BDL-alcohol rats. Additionally, higher levels of 4-HNE and decreased TAC in the cerebellum of BDL-alcohol rats suggest oxidative stress is the triggering factor of apoptotic and necroptotic neuronal loss/injury.

Exploring the logic and conducting a comprehensive evaluation of AdipoRon-based adiponectin replacement therapy against hormone-related cancers-a systematic review

The potential benefits of adiponectin replacement therapy extend to numerous human diseases, with current research showing particular interest in its effectiveness against specific cancer forms, especially hormone-related. However, limitations in the pharmacological use of the intact protein have led to a focus on alternative options. AdipoRon is an extensively studied non-peptidic drug candidate for adiponectin replacement therapy. While researchers have explored the efficacy and therapeutic applications of AdipoRon in various disease conditions, their effects against cancer models advanced more, with no review regarding AdipoRon's efficacy against hormone-related cancers being published. The present systematic review aims to fill this gap. Preclinical evidence was compiled from PubMed, EMBASE, COCHRANE, and Google Scholar following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the manuscript's quality assessment was conducted using the Joanna Briggs Institute (JBI) Checklist Critical Appraisal Tool for Systematic Reviews' Quality. The included nine studies incorporated various cell and animal models of the pancreas, gynaecological system, and osteosarcoma cancers. AdipoRon demonstrated effectiveness against pancreatic cancer by activating p44/42 MAPK, mitochondrial dysfunction, and AMPK-mediated inhibition of ACC1. In gynaecological cancers, it exhibited promising anticancer effects through the activation of AMPK, potential inhibition of mTOR, and modulation of the SET1B/BOD1/AdipoR1 signaling cascade. Against osteosarcoma, AdipoRon worked by perturbing ERK1/2 signaling and reducing p70S6K phosphorylation. AdipoRon shows promise in preclinical studies, but human trials are crucial for clinical safety and effectiveness. Caution is needed due to potential off-target effects, especially in cancer therapy with multi-target approaches. Structural biology and computational methods can help predict these effects.

Intratumoral Injection of Large Surface Area Microparticle Taxanes in Carcinomas Increases Immune Effector Cell Concentrations, Checkpoint Expression, and Synergy with Checkpoint Inhibitors: A Review of Preclinical and Clinical Studies

This review summarizes development of large surface area microparticle paclitaxel (LSAM-PTX) and docetaxel (LSAM-DTX) for local treatment of primary carcinomas with emphasis on immunomodulation. Intratumoral (IT) delivery of LSAM-PTX and LSAM-DTX provides continuous, therapeutic drug levels for several weeks. Preclinical studies and clinical trials reported a reduction in tumor volume (TV) and immunomodulation in primary tumor and peripheral blood with increases in innate and adaptive immune cells and decreases in suppressor cells. Increased levels of checkpoint expression of immune cells occurred in clinical trials of high-risk non-muscle-invasive bladder cancer (LSAM-DTX) and unresectable localized pancreatic cancer (LSAM-PTX). TV reduction and increases in immune effector cells occurred following IT LSAM-DTX and IT LSAM-PTX together with anti-mCTLA-4 and anti-mPD-1, respectively. Synergistic benefits from combinatorial therapy in a 4T1-Luc breast cancer model included reduction of metastasis with IT LSAM-DTX + anti-mCTLA-4. IT LSAM-PTX and LSAM-DTX are tumoricidal, immune enhancing, and may improve solid tumor response to immune checkpoint inhibitors without additional systemic toxicity.

Dopaminergic neuronal death via necroptosis in Parkinson's disease: A review of the literature

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive dysfunction and loss of dopaminergic neurons of the substantia nigra pars compacta (SNc). Several pathways of programmed cell death are likely to play a role in dopaminergic neuron death, such as apoptosis, necrosis, pyroptosis and ferroptosis, as well as cell death associated with proteasomal and mitochondrial dysfunction. A better understanding of the molecular mechanisms underlying dopaminergic neuron death could inform the design of drugs that promote neuron survival. Necroptosis is a recently characterized regulated cell death mechanism that exhibits morphological features common to both apoptosis and necrosis. It requires activation of an intracellular pathway involving receptor-interacting protein 1 kinase (RIP1 kinase, RIPK1), receptor-interacting protein 3 kinase (RIP3 kinase, RIPK3) and mixed lineage kinase domain-like pseudokinase (MLKL). The potential involvement of this programmed cell death pathway in the pathogenesis of PD has been studied by analysing biomarkers for necroptosis, such as the levels and oligomerization of phosphorylated RIPK3 (pRIPK3) and phosphorylated MLKL (pMLKL), in several PD preclinical models and in PD human tissue. Although there is evidence that other types of cell death also have a role in DA neuron death, most studies support the hypothesis that this cell death mechanism is activated in PD tissues. Drugs that prevent or reduce necroptosis may provide neuroprotection for PD. In this review, we summarize the findings from these studies. We also discuss how manipulating necroptosis might open a novel therapeutic approach to reduce neuronal degeneration in PD.

Non-apoptotic cell death programs in cervical cancer with an emphasis on ferroptosis

BACKGROUND

Cervical cancer, a pernicious gynecological malignancy, causes the mortality of hundreds of thousands of females worldwide. Despite a considerable decline in mortality, the surging incidence rate among younger women has raised serious concerns. Immortality is the most important characteristic of tumor cells, hence the carcinogenesis of cervical cancer cells pivotally requires compromising with cell death mechanisms.

METHODS

The current study comprehensively reviewed the mechanisms of non-apoptotic cell death programs to provide possible disease management strategies.

RESULTS

Comprehensive evidence has stated that focusing on necroptosis, pyroptosis, and autophagy for disease management is associated with significant limitations such as insufficient understanding, contradictory functions, dependence on disease stage, and complexity of intracellular pathways. However, ferroptosis represents a predictable role in cervix carcinogenesis, and ferroptosis-related genes demonstrate a remarkable correlation with patient survival and clinical outcomes.

CONCLUSION

Ferroptosis may be an appropriate option for disease management strategies from predicting prognosis to treatment.

Intratumoral Treatment of Melanoma Tumors with Large Surface Area Microparticle Paclitaxel and Synergy with Immune Checkpoint Inhibition

The effects of intratumoral (IT) large surface area microparticle paclitaxel (LSAM-PTX) alone and in combination with systemic administration of the programmed cell death protein antibody (anti-mPD-1) were evaluated in a syngeneic murine model of melanoma. Groups of mice with subcutaneously implanted Clone M3 (Cloudman S91) tumors were treated with single and combination therapies. Tumor volume (TV) measurements, body weights, and clinical observations were followed in-life. At end of study, tumor-site tissues were collected, measured, and processed for flow cytometry along with blood and lymph nodes. The combination of LSAM-PTX + anti-mPD-1 resulted in an antitumoral response, which produced a significant decrease in TV compared to control animals. TV decreases also occurred in the LSAM-PTX and anti-mPD-1 groups. Flow cytometry analysis found increases in granulocytes and M2 macrophages and decreases in dendritic cells (DC) and monocytic myeloid-derived suppressor cells (M-MDSC) in tumor-site tissues. Increases in granulocytes and decreases in CD4+ T cells, macrophages, and M1 macrophages were found in the blood of animals administered the combination treatment. Increases in natural killer (NK) cells were found in lymph node tissue in the combination treatment group. These findings suggest that IT LSAM-PTX may provide benefit in the local treatment of melanomas and may synergize with systemic anti-PD-1 therapy, leading to additional tumoricidal outcomes without added systemic toxicity.

Inflammatory cell death induced by 5-aminolevulinic acid-photodynamic therapy initiates anticancer immunity

Background

Inflammatory cell death is a form of programmed cell death (PCD) that induces inflammatory mediators during the process. The production of inflammatory mediators during cell death is beneficial in standard cancer therapies as it can break the immune silence in cancers and induce anticancer immunity. Photodynamic therapy (PDT) is a cancer therapy with photosensitizer molecules and light sources to destroy cancer cells, which is currently used for treating different types of cancers in clinical settings. In this study, we investigated if PDT using 5-aminolevulinic (5-ALA-PDT) causes inflammatory cell death and, subsequently, increases the immunogenicity of cancer cells.

Methods

Mouse breast cancer (4T1) and human colon cancer (DLD-1) cells were treated with 5-ALA for 4 hours and then irradiated with a light source. PCD induction was measured by western blot analysis and FACS. Morphological changes were determined by transmission electron microscopy (TEM). BALB/c mice were injected with cell-free media, supernatant of freeze/thaw cells or supernatant of PDT cells intramuscular every week for 4 weeks and then challenged with 4T1 cells at the right hind flank of BALB/c. Tumor growth was monitored for 12 days.

Results

We found that 5-ALA-PDT induces inflammatory cell death, but not apoptosis, in 4T1 cells and DLD-1 cells in vitro. Moreover, when mice were pretreated with 5-ALA-PDT culture supernatant, the growth of 4T1 tumors was significantly suppressed compared to those pretreated with freeze and thaw (F/T) 4T1 culture supernatant.

Conclusion

These results indicate that 5-ALA-PDT induces inflammatory cell death which promotes anticancer immunity in vivo.

Involvement of necroptosis in the selective toxicity of the natural compound (±) gossypol on squamous skin cancer cells in vitro

Cutaneous basal and squamous cell carcinoma reflect the first and second most common type of non-melanoma skin cancer, respectively. Especially cutaneous squamous cell carcinoma has the tendency to metastasize, finally resulting in a rather poor prognosis. Therapeutic options comprise surgery, radiation therapy, and a systemic or targeted chemotherapy. There are some good treatment results, but overall, the response rate of newly developed drugs is still modest. Drug repurposing represents an alternative approach where already available and clinically approved substances are used, which originally intended for other clinical benefits. In this context, we tested the effect of the naturally occurring polyphenolic aldehyde (±) gossypol with concentrations between 1 and 5 µM on the invasive squamous cell carcinoma cell line SCL-1 and normal human epidermal keratinocytes. Gossypol treatment up to 96 h resulted in a selective cytotoxicity of SCL-1 cells (IC50: 1.7 µM, 96 h) compared with normal keratinocytes (IC50: ≥ 5.4 µM, 96 h) which is mediated by mitochondrial dysfunction and finally leading to necroptotic cell death. Taken together, gossypol shows a high potential as an alternative anticancer drug for the treatment of cutaneous squamous cell carcinoma.

V. J, Pal S, Nair BG, Kar R, Mishra N. Paraptosis: a unique cell death mode for targeting cancer

Programmed cell death (PCD) is the universal process that maintains cellular homeostasis and regulates all living systems' development, health and disease. Out of all, apoptosis is one of the major PCDs that was found to play a crucial role in many disease conditions, including cancer. The cancer cells acquire the ability to escape apoptotic cell death, thereby increasing their resistance towards current therapies. This issue has led to the need to search for alternate forms of programmed cell death mechanisms. Paraptosis is an alternative cell death pathway characterized by vacuolation and damage to the endoplasmic reticulum and mitochondria. Many natural compounds and metallic complexes have been reported to induce paraptosis in cancer cell lines. Since the morphological and biochemical features of paraptosis are much different from apoptosis and other alternate PCDs, it is crucial to understand the different modulators governing it. In this review, we have highlighted the factors that trigger paraptosis and the role of specific modulators in mediating this alternative cell death pathway. Recent findings include the role of paraptosis in inducing anti-tumour T-cell immunity and other immunogenic responses against cancer. A significant role played by paraptosis in cancer has also scaled its importance in knowing its mechanism. The study of paraptosis in xenograft mice, zebrafish model, 3D cultures, and novel paraptosis-based prognostic model for low-grade glioma patients have led to the broad aspect and its potential involvement in the field of cancer therapy. The co-occurrence of different modes of cell death with photodynamic therapy and other combinatorial treatments in the tumour microenvironment are also summarized here. Finally, the growth, challenges, and future perspectives of paraptosis research in cancer are discussed in this review. Understanding this unique PCD pathway would help to develop potential therapy and combat chemo-resistance in various cancer.

RIPK1-dependent necroptosis promotes vasculogenic mimicry formation via eIF4E in triple-negative breast cancer

Necroptosis is a caspase-independent form of programmed cell death. Receptor interacting protein kinase 1 (RIPK1) is a key molecule in the initiation of necroptosis and the formation of the necrotic complex. Vasculogenic mimicry (VM) provides a blood supply to tumor cells that is not dependent on endothelial cells. However, the relationship between necroptosis and VM in triple-negative breast cancer (TNBC) is not fully understood. In this study, we found that RIPK1-dependent necroptosis promoted VM formation in TNBC. Knockdown of RIPK1 significantly suppressed the number of necroptotic cells and VM formation. Moreover, RIPK1 activated the p-AKT/eIF4E signaling pathway during necroptosis in TNBC. eIF4E was blocked by knockdown of RIPK1 or AKT inhibitors. Furthermore, we found that eIF4E promoted VM formation by promoting epithelial-mesenchymal transition (EMT) and the expression and activity of MMP2. In addition to its critical role in necroptosis-mediated VM, eIF4E was essential for VM formation. Knockdown of eIF4E significantly suppressed VM formation during necroptosis. Finally, through clinical significance, the results found that eIF4E expression in TNBC was positively correlated with the mesenchymal marker vimentin, the VM marker MMP2, and the necroptosis markers MLKL and AKT. In conclusion, RIPK1-dependent necroptosis promotes VM formation in TNBC. Necroptosis promotes VM formation by activating RIPK1/p-AKT/eIF4E signaling in TNBC. eIF4E promotes EMT and MMP2 expression and activity, leading to VM formation. Our study provides a rationale for necroptosis-mediated VM and also providing a potential therapeutic target for TNBC.

Reovirus Type 3 Dearing Variants Do Not Induce Necroptosis in RIPK3-Expressing Human Tumor Cell Lines

Reoviruses are used as oncolytic viruses to destroy tumor cells. The concomitant induction of anti-tumor immune responses enhances the efficacy of therapy in tumors with low amounts of immune infiltrates before treatment. The reoviruses should provoke immunogenic cell death (ICD) to stimulate a tumor cell-directed immune response. Necroptosis is considered a major form of ICD, and involves receptor-interacting protein kinase 1 (RIPK1), RIPK3 and phosphorylation of mixed-lineage kinase domain-like protein (MLKL). This leads to cell membrane disintegration and the release of damage-associated molecular patterns that can activate immune responses. Reovirus Type 3 Dearing (T3D) can induce necroptosis in mouse L929 fibroblast cells and mouse embryonic fibroblasts. Most human tumor cell lines have a defect in RIPK3 expression and consequently fail to induce necroptosis as measured by MLKL phosphorylation. We used the human colorectal adenocarcinoma HT29 cell line as a model to study necroptosis in human cells since this cell line has frequently been described in necroptosis-related studies. To stimulate MLKL phosphorylation and induce necroptosis, HT29 cells were treated with a cocktail consisting of TNFα, the SMAC mimetic BV6, and the caspase inhibitor Z-VAD-FMK. While this treatment induced necroptosis, three different reovirus T3D variants, i.e., the plasmid-based reverse genetics generated virus (T3D^K), the wild-type reovirus T3D isolate R124, and the junction adhesion molecule-A-independent reovirus mutant (jin-1) failed to induce necroptosis in HT29 cells. In contrast, these viruses induced MLKL phosphorylation in murine L929 cells, albeit with varying efficiencies. Our study shows that while reoviruses efficiently induce necroptosis in L929 cells, this is not a common phenotype in human cell lines. This study emphasizes the difficulties of translating the results of ICD studies from murine cells to human cells.

Mixed lineage kinase domain-like pseudokinase: Conventional (necroptosis) and unconventional (necroptosis-independent) functions and features

Mixed lineage kinase domain-like pseudokinase (MLKL) is the terminal and indispensable mediator of necroptosis. Necroptosis, also known as programmed cell necrosis, is a caspase-independent cell death mechanism involved in various pathologic and inflammatory processes. Triggering necroptosis could be an alternative approach in treating apoptosis-resistant cancer cells to prevent recurrent disease. In addition to its function in necroptosis, MLKL plays a role as a regulator in many cellular processes independent of necroptosis. A better understanding of the intracellular function of MLKL and its role in various diseases and pathologic conditions is needed to enable discovery of new targeted therapies. Various necroptosis-dependent and independent functions of MLKL are reviewed in this chapter, with a focus on functions of MLKL in necroptosis, autophagy, inflammation, tissue regeneration, and endosomal trafficking.

Regulation of programmed cell death by Brd4

Epigenetic factor Brd4 has emerged as a key regulator of cancer cell proliferation. Targeted inhibition of Brd4 suppresses growth and induces apoptosis of various cancer cells. In addition to apoptosis, Brd4 has also been shown to regulate several other forms of programmed cell death (PCD), including autophagy, necroptosis, pyroptosis, and ferroptosis, with different biological outcomes. PCD plays key roles in development and tissue homeostasis by eliminating unnecessary or detrimental cells. Dysregulation of PCD is associated with various human diseases, including cancer, neurodegenerative and infectious diseases. In this review, we discussed some recent findings on how Brd4 actively regulates different forms of PCD and the therapeutic potentials of targeting Brd4 in PCD-related human diseases. A better understanding of PCD regulation would provide not only new insights into pathophysiological functions of PCD but also provide new avenues for therapy by targeting Brd4-regulated PCD.

Necroptosis: A Pathogenic Negotiator in Human Diseases

Over the past few decades, mechanisms of programmed cell death have attracted the scientific community because they are involved in diverse human diseases. Initially, apoptosis was considered as a crucial mechanistic pathway for programmed cell death; recently, an alternative regulated mode of cell death was identified, mimicking the features of both apoptosis and necrosis. Several lines of evidence have revealed that dysregulation of necroptosis leads to pathological diseases such as cancer, cardiovascular, lung, renal, hepatic, neurodegenerative, and inflammatory diseases. Regulated forms of necrosis are executed by death receptor ligands through the activation of receptor-interacting protein kinase (RIPK)-1/3 and mixed-lineage kinase domain-like (MLKL), resulting in the formation of a necrosome complex. Many papers based on genetic and pharmacological studies have shown that RIPKs and MLKL are the key regulatory effectors during the progression of multiple pathological diseases. This review focused on illuminating the mechanisms underlying necroptosis, the functions of necroptosis-associated proteins, and their influences on disease progression. We also discuss numerous natural and chemical compounds and novel targeted therapies that elicit beneficial roles of necroptotic cell death in malignant cells to bypass apoptosis and drug resistance and to provide suggestions for further research in this field.

Effect of Size and Concentration of Copper Nanoparticles on the Antimicrobial Activity in Escherichia coli through Multiple Mechanisms

Metal and metal oxide nanoparticles, including copper nanoparticles (CuNPs), display antimicrobial activities and are regarded as promising microorganism inhibitors. Here, we explored the antimicrobial activity of CuNPs in Escherichia coli (E. coli) using two particle sizes (20 and 60 nm) and five concentrations (1, 5, 10, 50 and 100 μg/mL). The result showed a concentration-dependent trend of bactericidal activities for both size groups, with 20 nm particles more effective than 60 nm particles at low concentrations. The membrane disruption caused by CuNPs was confirmed by electron microscopy, PI staining and protein leaking analysis. However, the results of reactive oxygen species generation and genomic DNA damage revealed that the size and concentration of CuNPs were factors affecting the induction of multiple bactericidal mechanisms simultaneously on different scales. Further results of annexin V-PI staining supported this hypothesis by showing the shifting composition of the early-, late- and non-apoptotic dead cells across the CuNP groups. Many CuNP treatment groups were rescued when four mammalian modulators-wortmannin, necrosulfonamide, Z-VAD-FMK, and SBI-0206965-were applied separately. The results suggest the possible existence of bacterial programmed cell death pathways in E. coli which could be triggered by CuNP treatments.

Transcriptome Analysis of Duck and Chicken Brains Infected with Aquatic Bird Bornavirus-1 (ABBV-1)

Aquatic bird bornavirus 1 (ABBV-1) is a neurotropic virus that infects waterfowls, resulting in persistent infection. Experimental infection showed that both Muscovy ducks and chickens support persistent ABBV-1 infection in the central nervous system (CNS), up to 12 weeks post-infection (wpi), without the development of clinical disease. The aim of the present study was to describe the transcriptomic profiles in the brains of experimentally infected Muscovy ducks and chickens infected with ABBV-1 at 4 and 12 wpi. Transcribed RNA was sequenced by next-generation sequencing and analyzed by principal component analysis (PCA) and differential gene expression. The functional annotation of differentially expressed genes was evaluated by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The PCA showed that the infected ducks sampled at both 4 and 12 wpi clustered separately from the controls, while only the samples from the chickens at 12 wpi, but not at 4 wpi, formed a separate cluster. In the ducks, more genes were differentially expressed at 4 wpi than 12 wpi, and the majority of the highly differentially expressed genes (DEG) were upregulated. On the other hand, the infected chickens had fewer DEGs at 4 wpi than at 12 wpi, and the majority of those with high numbers of DEGs were downregulated at 4 wpi and upregulated at 12 wpi. The functional annotation showed that the most enriched GO terms were immune-associated in both species; however, the terms associated with the innate immune response were predominantly enriched in the ducks, whereas the chickens had enrichment of both the innate and adaptive immune response. Immune-associated pathways were also enriched according to the KEGG pathway analysis in both species. Overall, the transcriptomic analysis of the duck and chicken brains showed that the main biological responses to ABBV-1 infection were immune-associated and corresponded with the levels of inflammation in the CNS.

Ferroptosis in glioma treatment: Current situation, prospects and drug applications

Ferroptosis is a regulatory form of iron-dependent cell death caused by the accumulation of lipid-based reactive oxygen species (ROS) and differs from apoptosis, pyroptosis, and necrosis. Especially in neoplastic diseases, the susceptibility of tumor cells to ferroptosis affects prognosis and is associated with complex effects. Gliomas are the most common primary intracranial tumors, accounting for disease in 81% of patients with malignant brain tumors. An increasing number of studies have revealed the particular characteristics of iron metabolism in glioma cells. Therefore, agents that target a wide range of molecules involved in ferroptosis may regulate this process and enhance glioma treatment. Here, we review the underlying mechanisms of ferroptosis and summarize the potential therapeutic options for targeting ferroptosis in glioma.

Advances in RIPK1 kinase inhibitors

Programmed necrosis is a new modulated cell death mode with necrotizing morphological characteristics. Receptor interacting protein 1 (RIPK1) is a critical mediator of the programmed necrosis pathway that is involved in stroke, myocardial infarction, fatal systemic inflammatory response syndrome, Alzheimer's disease, and malignancy. At present, the reported inhibitors are divided into four categories. The first category is the type I ATP-competitive kinase inhibitors that targets the area occupied by the ATP adenylate ring; The second category is type Ⅱ ATP competitive kinase inhibitors targeting the DLG-out conformation of RIPK1; The third category is type Ⅲ kinase inhibitors that compete for binding to allosteric sites near ATP pockets; The last category is others. This paper reviews the structure, biological function, and recent research progress of receptor interaction protein-1 kinase inhibitors.

Research progress in endothelial cell injury and repair

Endothelial cells, which are important metabolic and endocrine cells, play an important role in regulating vascular function. The occurrence and development of various cardiovascular and cerebrovascular diseases are associated with endothelial dysfunction. However, the underlying mechanism of vascular endothelial injury is not fully understood. It has been reported that the mechanism of endothelial injury mainly involves inflammation and oxidative stress. Moreover, endothelial progenitor cells are regarded as important contributors in repairing damaged endothelium. Multiple interventions (including chemical drugs and traditional Chinese medicines) exert endothelial protection by decreasing the release of inducing factors, suppressing inflammation and oxidative stress, and preventing endothelial cell senescence.

Potential of Black Phosphorus in Immune-Based Therapeutic Strategies

Black phosphorus (BP) consists of phosphorus atoms, an essential element of bone and nucleic acid, which covalently bonds to three adjacent phosphorus atoms to form a puckered bilayer structure. With its anisotropy, band gap, biodegradability, and biocompatibility properties, BP is considered promising for cancer therapy. For example, BP under irradiation can convert near-infrared (NIR) light into heat and reactive oxygen species (ROS) to damage cancer cells, called photothermal therapy (PTT) and photodynamic therapy (PDT). Compared with PTT and PDT, the novel techniques of sonodynamic therapy (SDT) and photoacoustic therapy (PAT) exhibit amplified ROS generation and precise photoacoustic-shockwaves to enhance anticancer effect when BP receives ultrasound or NIR irradiation. Based on the prospective phototherapy, BP with irradiation can cause a “double-kill” to tumor cells, involving tumor-structure damage induced by heat, ROS, and shockwaves and a subsequent anticancer immune response induced by in situ vaccines construction in tumor site, which is referred to as photoimmunotherapy (PIT). In conclusion, BP shows promise in natural antitumor biological activity, biological imaging, drug delivery, PTT/PDT/SDT/PAT/PIT, nanovaccines, nanoadjuvants, and combination immunotherapy regimens.

Hepatocellular Carcinoma Intrinsic Cell Death Regulates Immune Response and Prognosis

Ablative and locoregional treatment options, such as radiofrequency, ethanol injection, microwave, and cryoablation, as well as irreversible electroporation, are effective therapies for early-stage hepatocellular carcinoma (HCC). Hepatocyte death caused by ablative procedures is known to increase the release of tumor-associated antigen, thus enhancing tumor immunogenicity. In addition, the heat ablative resection induces pyroptotic cell death accompanied by the release of several inflammatory factors and immune-related proteins, including damage-associated molecular patterns (DAMPs), heat shock proteins (HSPs), ficolin 3, ATP, and DNA/RNA, which potentiate the antitumoral immune response. Surgical approaches that enhance tumor necrosis and reduce hypoxia in the residual liver parenchyma have been shown to increase the disease-free survival rate by reducing the host’s immunosuppressive response. Scalpel devices and targeted surgical approach combined with immune-modulating drugs are an interesting and promising area to maximize therapeutic outcomes after HCC ablation.

The cooperative interplay among inflammation, necroptosis and YAP pathway contributes to the folate deficiency-induced liver cells enlargement

Change in cell size may bring in profound impact to cell function and survival, hence the integrity of the organs consisting of those cells. Nevertheless, how cell size is regulated remains incompletely understood. We used the fluorescent zebrafish transgenic line Tg-GGH/LR that displays inducible folate deficiency (FD) and hepatomegaly upon FD induction as in vivo model. We found that FD caused hepatocytes enlargement and increased liver stiffness, which could not be prevented by nucleotides supplementations. Both in vitro and in vivo studies indicated that RIPK3/MLKL-dependent necroptotic pathway and Hippo signaling interactively participated in this FD-induced hepatocytic enlargement in a dual chronological and cooperative manner. FD also induced hepatic inflammation, which convenes a dialog of positive feedback loop between necroptotic and Hippo pathways. The increased MMP13 expression in response to FD elevated TNFα level and further aggravated the hepatocyte enlargement. Meanwhile, F-actin was circumferentially re-allocated at the edge under cell membrane in response to FD. Our results substantiate the interplay among intracellular folate status, pathways regulation, inflammatory responses, actin cytoskeleton and cell volume control, which can be best observed with in vivo platform. Our data also support the use of this Tg-GGH/LR transgenic line for the mechanistical and therapeutic research for the pathologic conditions related to cell size alteration.

Antagonizing RARγ Drives Necroptosis of Cancer Stem Cells

There is a need for agents that eliminate cancer stem cells, which sustain cancer and are also largely responsible for disease relapse and metastasis. Conventional chemotherapeutics and radiotherapy are often highly effective against the bulk of cancer cells, which are proliferating, but spare cancer stem cells. Therapeutics that target cancer stem cells may also provide a bona fide cure for cancer. There are two rationales for targeting the retinoic acid receptor (RAR)γ. First, RARγ is expressed selectively within primitive cells. Second, RARγ is a putative oncogene for a number of human cancers, including cases of acute myeloid leukemia, cholangiocarcinoma, and colorectal, renal and hepatocellular carcinomas. Prostate cancer cells depend on active RARγ for their survival. Antagonizing all RARs caused necroptosis of prostate and breast cancer stem cell-like cells, and the cancer stem cells that gave rise to neurospheres from pediatric patients’ primitive neuroectodermal tumors and an astrocytoma. As tested for prostate cancer, antagonizing RARγ was sufficient to drive necroptosis. Achieving cancer-selectively is a longstanding paradigm for developing new treatments. The normal prostate epithelium was less sensitive to the RARγ antagonist and pan-RAR antagonist than prostate cancer cells, and fibroblasts and blood mononuclear cells were insensitive. The RARγ antagonist and pan-RAR antagonist are promising new cancer therapeutics.

Necroptosis as a Novel Facet of Mitotic Catastrophe

Mitotic catastrophe is a defensive mechanism that promotes elimination of cells with aberrant mitosis by triggering the cell-death pathways and/or cellular senescence. Nowadays, it is known that apoptosis, autophagic cell death, and necrosis could be consequences of mitotic catastrophe. Here, we demonstrate the ability of a DNA-damaging agent, doxorubicin, at 600 nM concentration to stimulate mitotic catastrophe. We observe that the inhibition of caspase activity leads to accumulation of cells with mitotic catastrophe hallmarks in which RIP1-dependent necroptotic cell death is triggered. The suppression of autophagy by a chemical inhibitor or ATG13 knockout upregulates RIP1 phosphorylation and promotes necroptotic cell death. Thus, in certain conditions mitotic catastrophe, in addition to apoptosis and autophagy, can precede necroptosis.

Oxidative stress in cancer therapy: Friend or enemy?

Excessive cellular oxidative stress is widely perceived as a key factor in pathophysiological conditions and cancer development. Healthy cells use several mechanisms to maintain intracellular levels of reactive oxygen species (ROS) and overall redox homeostasis to avoid damage to DNA, proteins, and lipids. Cancer cells, in contrast, exhibit elevated ROS levels and upregulated protective antioxidant pathways. Counterintuitively, such elevated oxidative stress and enhanced antioxidant defence mechanisms in cancer cells provide a therapeutic opportunity for the development of drugs with different anticancer mechanisms of action (MoA). In this review, oxidative stress and the role of ROS in cells are described. The tumour-suppressive and tumour-promotive functions of ROS are discussed to compare these two different therapeutic strategies (increasing or decreasing ROS to fight cancer). Clinically approved drugs with demonstrated oxidative stress anticancer MoAs are highlighted before describing examples of metal-based anticancer drug candidates causing oxidative stress in cancer cells via novel MoAs.

Reperfusion Cardiac Injury: Receptors and the Signaling Mechanisms

It has been documented that Ca2+ overload and increased production of reactive oxygen species play a significant role in reperfusion injury (RI) of cardiomyocytes. Ischemia/reperfusion induces cell death as a result of necrosis, necroptosis, apoptosis, and possibly autophagy, pyroptosis and ferroptosis. It has also been demonstrated that the NLRP3 inflammasome is involved in RI of the heart. An increase in adrenergic system activity during the restoration of coronary perfusion negatively affected cardiac resistance to RI. Toll-like receptors are involved in RI of the heart. Angiotensin II and endothelin-1 aggravated ischemic/reperfusion injury of the heart. Activation of neutrophils, monocytes, CD4+ T-cells and platelets contributes to cardiac ischemia/reperfusion injury. Our review outlines the role of these factors in reperfusion cardiac injury.

Astaxanthin induces NADPH oxidase activation and receptor‑interacting protein kinase 1‑mediated necroptosis in gastric cancer AGS cells

Astaxanthin (ASX), a red-colored xanthophyll carotenoid, functions as an antioxidant or pro-oxidant. ASX displays anticancer effects by reducing or increasing oxidative stress. Reactive oxygen species (ROS) promote cancer cell death by necroptosis mediated by receptor-interacting protein kinase 1 (RIP1) and RIP3. NADPH oxidase is a major source of ROS that may promote necroptosis in some cancer cells. The present study aimed to investigate whether ASX induces necroptosis by increasing NADPH oxidase activity and ROS levels in gastric cancer AGS cells. AGS cells were treated with ASX with or without ML171 (NADPH oxidase 1 specific inhibitor), N-acetyl cysteine (NAC; antioxidant), z-VAD (pan-caspase inhibitor) or Necrostatin-1 (Nec-1; a specific inhibitor of RIP1). As a result, ASX increased NADPH oxidase activity, ROS levels and cell death, and these effects were suppressed by ML171 and NAC. Furthermore, ASX induced RIP1 and RIP3 activation, ultimately inducing mixed lineage kinase domain-like protein (MLKL) activation, lactate dehydrogenase (LDH) release and cell death. Moreover, the ASX-induced decrease in cell viability was reversed by Nec-1 treatment and RIP1 siRNA transfection, but not by z-VAD. ASX did not increase the ratio of apoptotic Bax/anti-apoptotic Bcl-2, the number of Annexin V-positive cells, or caspase-9 activation, which are apoptosis indices. In conclusion, ASX induced necroptotic cell death by increasing NADPH oxidase activity, ROS levels, LDH release and the number of propidium iodide-positive cells, as well as activating necroptosis-regulating proteins, RIP1/RIP3/MLKL, in gastric cancer AGS cells. The results of this study demonstrated the necroptotic effect of ASX on gastric cancer AGS cells, which required NADPH oxidase activation and RIP1/RIP3/MLKL signaling in vitro.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.

Molecular subtypes based on ferroptosis-related genes and tumor microenvironment infiltration characterization in lung adenocarcinoma

Recently, several molecular subtypes with different prognosis have been found in lung adenocarcinoma (LUAD). However, the characteristics of the ferroptosis molecular subtypes and the associated tumor microenvironment (TME) cell infiltration have not been fully studied in LUAD. Using 1160 lung adenocarcinoma samples, we explored the molecular subtypes mediated by ferroptosis-related genes, along with the associated TME cell infiltration. The ferroptosis score was constructed using the least absolute shrinkage and selection operator regression (LASSO) method to quantify the ferroptosis characteristics of a single tumor. Three different molecular subtypes related to ferroptosis, with different prognoses, were identified in LUAD. Analysis of TME cell infiltration revealed immune heterogeneity among the three subtypes. Cluster A was characterized by immunosuppression and was associated with stromal activation. Cluster C was characterized by a large number of immune cells infiltrating the TME, promoting tumor immune response, and it was significantly enriched in immune activation-related signaling pathways. Relatively less infiltration of immune cells was a feature of cluster B. The ferroptosis score can predict tumor subtype, immunity and prognosis. A low ferroptosis score was characterized by immune activation and good prognosis, as seen in the cluster C subtype. Relative immunosuppression and poor prognosis were the characteristics of a high ferroptosis score, as seen in cluster A and B subtypes. At the same time, the anti-PD-1/L1 immunotherapy cohort demonstrated that a low ferroptosis score was associated with higher efficacy of immunotherapy. The ferroptosis score is a promising biomarker that could be of great significance to determine the prognosis, molecular subtypes, TME cell infiltration characteristics and immunotherapy effects in patients with LUAD.

Construction and analysis of a novel ferroptosis-related gene signature predicting prognosis in lung adenocarcinoma

Ferroptosis is a newly discovered, iron‐dependent, nonapoptotic form of programmed cell death that plays an important role in the development of lung adenocarcinoma (LUAD). In this study, ferroptosis‐related genes (FRGs) were identified from the FerrDb dataset, and the mRNA expression profiles and corresponding clinical data of LUAD patients were downloaded from the University of California, Santa Cruz (UCSC) databases. Data from LUAD patients from the Gene Expression Omnibus (GEO) dataset were used as the verification set. Cox and Lasso regression analyses were used to screen the FRGs with prognostic value, and six prognostic‐related FRGs were selected to construct prognostic risk score signatures. Immunohistochemistry was utilized to manifest the differential expression of six FRGs in tumor and normal tissues at the protein level. Functional enrichment analysis indicated that FRGs were mainly enriched in ferroptosis‐related pathways. Patients were divided into high‐ and low‐risk groups based on the median risk score. The Kaplan–Meier survival curves confirmed that patients with a high score had significantly worse overall survival. Receiver operating characteristic (ROC) curves proved that the prognostic signature has good sensitivity and specificity for predicting the prognosis of LUAD patients. Nomogram analysis showed that the prognostic signature has potential independent prognostic value. Moreover, the prognostic signature has been shown to be significantly associated with some clinical features (T stage, N stage, tumor stage, and survival status) as well as many immune‐activity‐related genes and immune‐checkpoint‐related genes. In conclusion, we constructed a prognostic signature consisting of six FGRs, which can provide a reference for predicting the prognosis of LUAD patients.

RIP3-dependent necroptosis contributes to the pathogenesis of chronic obstructive pulmonary disease

Necroptosis has emerged as a potential mechanism in the pathogenesis of chronic obstructive pulmonary disease (COPD). Here, we found that markers of necroptosis, including high mobility group box 1 release and phosphorylation of mixed lineage kinase domain-like protein (p-MLKL), were markedly induced in the late stage of cigarette smoking-induced (CS-induced) emphysema in mouse lung tissue as well as in lung epithelial cells and organoids with higher dosage of or more prolonged exposure to cigarette smoking extract (CSE). Apoptotic signals were also detected and maximally induced in the early stage of CS-exposed mice and CSE-treated epithelial cells. Inhibition of apoptosis by Z-VAD, a pan-caspase inhibitor, switched the cellular stress to enhanced necroptosis in lung epithelial cells and organoids treated with CSE. Depletion or inhibition of receptor-interacting protein kinase 3 (RIP3) or MLKL attenuated the CSE-induced cell death, suggesting that necroptosis contributes to CSE-induced cell death. Silencing or inhibition of RIP1 had no protective effect, indicating a RIP1-independent RIP3 activation pathway. CSE-induced necroptosis released more damage-associated molecular patterns and evoked greater engulfment but slower clearance by bone marrow-derived macrophages, leading to enhanced expression of proinflammatory cytokines Tnfα and Il6. Finally, our in vivo data verified that inhibition of necroptosis by RIP3 inhibitor GSK'872 protected mice from CS-induced emphysema and suppressed the lung inflammation. In conclusion, we provide evidence that necroptosis contributes to the pathogenesis of COPD. Targeting RIP3 and its downstream pathway may be an effective therapy for COPD.

Pigmentation Levels Affect Melanoma Responses to Coriolus versicolor Extract and Play a Crucial Role in Melanoma-Mononuclear Cell Crosstalk

Melanoma, the malignancy originating from pigment-producing melanocytes, is the most aggressive form of skin cancer and has a poor prognosis once the disease starts to metastasize. The process of melanin synthesis generates an immunosuppressive and mutagenic environment, and can increase melanoma cell resistance to different treatment modalities, including chemo-, radio- or photodynamic therapy. Recently, we have shown that the presence of melanin pigment inhibits the melanoma cell response to bioactive components of Coriolus versicolor (CV) Chinese fungus. Herein, using the same human melanoma cell line in which the level of pigmentation can be controlled by the L-tyrosine concentration in culture medium, we tested the effect of suppression of melanogenesis on the melanoma cell response to CV extract and investigated the cell death pathway induced by fungus extract in sensitized melanoma cells. Our data showed that susceptibility to CV-induced melanoma cell death is significantly increased after cell depigmentation. To the best of our knowledge, we are the first to demonstrate that CV extract can induce RIPK1/RIPK3/MLKL-mediated necroptosis in depigmented melanoma cells. Moreover, using the co-culture system, we showed that inhibition of the tyrosinase activity in melanoma cells modulates cytokine expression in co-cultured mononuclear cells, indicating that depigmentation of melanoma cells may activate immune cells and thereby influence a host anticancer response.

The potential role of necroptosis in clinical diseases (Review)

As an important type of programmed cell death in addition to apoptosis, necroptosis occurs in a variety of pathophysiological processes, including infections, liver diseases, kidney injury, neurodegenerative diseases, cardiovascular diseases, and human tumors. It can be triggered by a variety of factors, such as tumor necrosis factor receptor and Toll‑like receptor families, intracellular DNA and RNA sensors, and interferon, and is mainly mediated by receptor‑interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain‑like protein. A better understanding of the mechanism of necroptosis may be useful in the development of novel drugs for necroptosis‑related diseases. In this review, the focus is on the molecular mechanisms of necroptosis, exploring the role of necroptosis in different pathologies, discussing their potential as a novel therapeutic target for disease therapy, and providing suggestions for further study in this area.

The Role of Necroptosis: Biological Relevance and Its Involvement in Cancer

Simple Summary

A new form of programmed necrosis called necroptosis has emerged. This new and well-documented type of programmed cell death is involved in several human diseases, including cancer. RIPK1, the main mediator of necroptosis, in response to different stimuli, activates several molecular pathways leading to inflammation, cell survival, or cell death. Targeting necroptosis could be a new strategy for advanced therapies. In this review, we focus on the biological relevance of this type of programmed cell death and its main executor RIPK1 in pathogenesis to find novel potential clinical intervention strategies.

Abstract

Regulated cell death mechanisms are essential for the maintenance of cellular homeostasis. Evasion of cell death is one of the most important hallmarks of cancer. Necroptosis is a caspase independent form of regulated cell death, investigated as a novel therapeutic strategy to eradicate apoptosis resistant cancer cells. The process can be triggered by a variety of stimuli and is controlled by the activation of RIP kinases family as well as MLKL. The well-studied executor, RIPK1, is able to modulate key cellular events through the interaction with several proteins, acting as strategic crossroads of several molecular pathways. Little evidence is reported about its involvement in tumorigenesis. In this review, we summarize current studies on the biological relevance of necroptosis, its contradictory role in cancer and its function in cell fate control. Targeting necroptosis might be a novel therapeutic intervention strategy in anticancer therapies as a pharmacologically controllable event.

Clinical Significance of Receptor-Interacting Protein 3 and Parkin, Essential Molecules for Necroptosis, in Breast Cancer

Purpose

Receptor-interacting protein 3 (RIP3) is the main initiator of necroptosis. Parkin prevents the formation of the RIP1–RIP3 complex by promoting polyubiquitination of RIP3. However, the mechanism by which necroptosis affects the clinical features of breast cancer and prognosis is not known. Here, we aimed to study the effect of necroptosis on the clinical features and prognosis of breast cancer by assessing the expression of RIP3 and Parkin.

Methods

Tissue microarrays (TMAs) were constructed from 257 cases of breast cancer. Immunohistochemistry was performed on 4-μm tissue sections from each TMA block. The χ² test, Kaplan-Meier survival analysis with log-rank test, and Cox regression proportional hazard model were used for statistical analysis.

Results

Low RIP3 expression resulted in a large tumor size and high nuclear grade. Low RIP3 expression was correlated with human epidermal growth factor receptor 2 positivity, short overall survival (OS), and short disease-free survival (DFS). The triple negative breast cancer group with low RIP3 expression and lymph node (LN) positive group with low RIP3 expression had the shortest OS. High Parkin expression was associated with high histological grade, estrogen and/or progesterone receptor negativity, and lymphatic emboli, but was not correlated with OS and DFS. OS was correlated with LN metastasis and RIP3 loss and DFS with large tumor size, LN metastasis, and RIP3 loss.

Conclusion

Low RIP3 and high Parkin expression are associated with aggressive clinical features in breast cancer. RIP3, a molecular marker of necroptosis, is an independent factor associated with survival in breast cancer. Further in-depth studies are needed to investigate the role of necroptosis in breast cancer development, metastasis, and treatment in the future.

Local administration of submicron particle paclitaxel to solid carcinomas induces direct cytotoxicity and immune-mediated tumoricidal effects without local or systemic toxicity: preclinical and clinical studies

This report describes local administration of submicron particle paclitaxel (SPP) (NanoPac®: ~ 800-nm-sized particles with high relative surface area with each particle containing ~ 2 billion molecules of paclitaxel) in preclinical models and clinical trials evaluating treatment of carcinomas. Paclitaxel is active in the treatment of epithelial solid tumors including ovarian, peritoneal, pancreatic, breast, esophageal, prostate, and non-small cell lung cancer. SPP has been delivered directly to solid tumors, where the particles are retained and continuously release the drug, exposing primary tumors to high, therapeutic levels of paclitaxel for several weeks. As a result, tumor cell death shifts from primarily apoptosis to both apoptosis and necroptosis. Direct local tumoricidal effects of paclitaxel, as well as stimulation of innate and adaptive immune responses, contribute to antineoplastic effects. Local administration of SPP may facilitate tumor response to systemically administered chemotherapy, targeted therapy, or immunotherapy without contributing to systemic toxicity. Results of preclinical and clinical investigations described here suggest that local administration of SPP achieves clinical benefit with negligible toxicity and may complement standard treatments for metastatic disease.

2-Hydroxyglutarate in Cancer Cells

Significance: Cancer cells are stabilized in an undifferentiated state similar to stem cells. This leads to profound modifications of their metabolism, which further modifies their genetics and epigenetics as malignancy progresses. Specific metabolites and enzymes may serve as clinical markers of cancer progression. Recent Advances: Both 2-hydroxyglutarate (2HG) enantiomers are associated with reprogrammed metabolism, in grade III/IV glioma, glioblastoma, and acute myeloid leukemia cells, and numerous other cancer types, while acting also in the cross talk of tumors with immune cells. 2HG contributes to specific alternations in cancer metabolism and developed oxidative stress, while also inducing decisions on the differentiation of naive T lymphocytes, and serves as a signal messenger in immune cells. Moreover, 2HG inhibits chromatin-modifying enzymes, namely 2-oxoglutarate-dependent dioxygenases, and interferes with hypoxia-inducible factor (HIF) transcriptome reprogramming and mammalian target of rapamycin (mTOR) pathway, thus dysregulating gene expression and further promoting cancerogenesis. Critical Issues: Typically, heterozygous mutations within the active sites of isocitrate dehydrogenase isoform 1 (IDH1)^R132H and mitochondrial isocitrate dehydrogenase isoform 2 (IDH2)^R140Q provide cells with millimolar r-2-hydroxyglutarate (r-2HG) concentrations, whereas side activities of lactate and malate dehydrogenase form submillimolar s-2-hydroxyglutarate (s-2HG). However, even wild-type IDH1 and IDH2, notably under shifts toward reductive carboxylation glutaminolysis or changes in other enzymes, lead to "intermediate" 0.01-0.1 mM 2HG levels, for example, in breast carcinoma compared with 10^-8M in noncancer cells. Future Directions: Uncovering further molecular metabolism details specific for given cancer cell types and sequence-specific epigenetic alternations will lead to the design of diagnostic approaches, not only for predicting patients' prognosis or uncovering metastases and tumor remissions but also for early diagnostics.

Apigenin causes necroptosis by inducing ROS accumulation, mitochondrial dysfunction, and ATP depletion in malignant mesothelioma cells

Apigenin, a naturally occurring flavonoid, is known to exhibit significant anticancer activity. This study was designed to determine the effects of apigenin on two malignant mesothelioma cell lines, MSTO-211H and H2452, and to explore the underlying mechanism(s). Apigenin significantly inhibited cell viability with a concomitant increase in intracellular reactive oxygen species (ROS) and caused the loss of mitochondrial membrane potential (ΔΨm), and ATP depletion, resulting in apoptosis and necroptosis in monolayer cell culture. Apigenin upregulated DNA damage response proteins, including the DNA double strand break marker phospho (p)-histone H2A.X. and caused a transition delay at the G₂/M phase of cell cycle. Western blot analysis showed that apigenin treatment upregulated protein levels of cleaved caspase-3, cleaved PARP, p-MLKL, and p-RIP3 along with an increased Bax/Bcl-2 ratio. ATP supplementation restored cell viability and levels of DNA damage-, apoptosis- and necroptosis-related proteins that apigenin caused. In addition, N-acetylcysteine reduced ROS production and improved ΔΨm loss and cell death that were caused by apigenin. In a 3D spheroid culture model, ROS-dependent necroptosis was found to be a mechanism involved in the anti-cancer activity of apigenin against malignant mesothelioma cells. Taken together, our findings suggest that apigenin can induce ROS-dependent necroptotic cell death due to ATP depletion through mitochondrial dysfunction. This study provides us a possible mechanism underlying why apigenin could be used as a therapeutic candidate for treating malignant mesothelioma.

The molecular mechanisms of MLKL-dependent and MLKL-independent necrosis

Necrosis, a type of unwanted and passive cell demise, usually occurs under the excessive external stress and is considered to be unregulated. However, under some special conditions such as caspase inhibition, necrosis is regulable in a well-orchestrated way. The term 'regulated necrosis' has been proposed to describe such programed necrosis. Recently, several forms of necrosis, including necroptosis, pyroptosis, ferroptosis, parthanatos, oxytosis, NETosis, and Na+/K+-ATPase-mediated necrosis, have been identified, and some crucial regulators governing regulated necrosis have also been discovered. Mixed lineage kinase domain-like pseudokinase (MLKL), a core regulator in necroptosis, acts as an executioner in response to ligands of death receptor family. Its activation requires the receptor-interacting protein kinases, RIP1 and RIP3. However, MLKL is only involved in necroptosis, i.e. MLKL is dispensable for necrosis. Therefore, this review is aimed at summarizing the molecular mechanisms of MLKL-dependent and MLKL-independent necrosis.

Hepatic inflammation after burn injury is associated with necroptotic cell death signaling

BACKGROUND

Burn injury still has a high attributable mortality. The elevated mortality rate of severe burns is still concerning. Hepatic inflammation and injury are common after burns and are associated with poor outcomes. Necroptosis is a programmed cell death linked with inflammation. Thus, assessing necroptotic pathways in the liver can lead to new therapeutic modalities to improve mortality after severe burns.

METHODS

Mice underwent 15% total body surface area burn or sham injury. Three hours after burn, the mice were euthanized to collect blood and livers. Histology, injury markers, genes expression, and tissue protein levels were compared between groups.

RESULTS

Compared with sham, burned mice had heightened liver inflammatory cell infiltration and edema. Serum aspartate aminotransferase and alanine aminotransferase were increased by 4.9- and 3.4-fold, respectively, in burned mice relative to sham (p < 0.05). Expression of tumor necrosis factor α, interleukin-6, interleukin-1β, and CXCL1 (KC) genes were elevated in livers of burned mice by 10-, 86-, 10-, and 828-fold, respectively, compared with sham (p < 0.05). Expression of necroptotic genes, namely, receptor-interacting protein kinases 1 and 3, and mixed lineage kinase domain-like in livers of burned mice were increased by 10-, 13-, and 4.5-fold, respectively, relative to sham (p < 0.05). Receptor-interacting protein kinase 1 and phosphorylated mixed lineage kinase domain-like protein levels measured by Western-blot in livers after burn injury were elevated by 22- and 17-fold, respectively, compared with sham (p < 0.05).

CONCLUSION

Liver damage occurs early after burns in mice and is associated with elevation of proinflammatory cytokines, chemokine, and proteins involved in the necroptotic pathway. This study suggests that necroptosis plays a role in the pathogenesis of liver failure secondary to burn injury.

Targeting necroptosis in anticancer therapy: mechanisms and modulators

Necroptosis, a genetically programmed form of necrotic cell death, serves as an important pathway in human diseases. As a critical cell-killing mechanism, necroptosis is associated with cancer progression, metastasis, and immunosurveillance. Targeting necroptosis pathway by small molecule modulators is emerging as an effective approach in cancer therapy, which has the advantage to bypass the apoptosis-resistance and maintain antitumor immunity. Therefore, a better understanding of the mechanism of necroptosis and necroptosis modulators is necessary to develop novel strategies for cancer therapy. This review will summarize recent progress of the mechanisms and detecting methods of necroptosis. In particular, the relationship between necroptosis and cancer therapy and medicinal chemistry of necroptosis modulators will be focused on.

Up-Regulation of RIP3 Alleviates Prostate Cancer Progression by Activation of RIP3/MLKL Signaling Pathway and Induction of Necroptosis

Background

The receptor-interacting protein kinase 3 (RIP3/RIPK3) was recently found to be a critical regulator of programmed necrosis/necroptosis. However, the biological role and clinical significance of RIP3 in prostate cancer remain obscure.

Methods

Western blotting and QRT-PCR were performed to detect the level of RIP3 in prostate cancer cells. Fixed cancer tissue and normal tissue specimens were subjected to immunohistochemical analysis of RIP3. Cell migration and invasion abilities were evaluated by transwell assays. In vitro proliferative ability was examed by MTS. And in vivo nude mice model were used to evaluate the effect of RIP3 ectopic expression on proliferative capability. Cell cycle of prostate cancer cells were analyzed by flow cytometry. Changes in some related proteins caused by RIP3 overexpression were explored using Western blotting.

Results

RIP3 was significantly down-regulated in prostate cancer cell lines and clinical prostate tumor samples. And over-expressing RIP3 suppressed the migration and invasion of prostate cancer cells. Two important matrix metalloproteinases MMP2, MMP9 which enables the destruction of the histological barrier of tumor cell invasion and three mesenchymal markers Vimentin, fibronectin, and N-cadherin were under-expressed due to the overexpression of RIP3, but the E-cadherin level which is the epithelial marker was increased. Furthermore, our results also showed that RIP3 can inhibit the proliferation and tumorigenicity of prostate cancer cells both in vitro and in vivo by phosphorylating MLKL, which were reversed by MLKL inhibitor treatment, indicating that necroptosis was involved in cell death.

Conclusion

Taken together, these findings indicated that RIP3 is responsible for the progression of prostate cancer, suggesting that RIP3 might have the potential to be a prognostic marker or a therapeutic target against prostate cancer.

Necroptosis Induced by Ruthenium(II) Complexes as Dual Catalytic Inhibitors of Topoisomerase I/II

Inducing necroptosis in cancer cells is an effective approach to circumvent drug-resistance. Metal-based triggers have, however, rarely been reported. Ruthenium(II) complexes containing 1,1-(pyrazin-2-yl)pyreno[4,5-e][1,2,4]triazine were developed with a series of different ancillary ligands (Ru1-7). The combination of the main ligand with bipyridyl and phenylpyridyl ligands endows Ru7 with superior nucleus-targeting properties. As a rare dual catalytic inhibitor, Ru7 effectively inhibits the endogenous activities of topoisomerase (topo) I and II and kills cancer cells by necroptosis. The cell signaling pathway from topo inhibition to necroptosis was elucidated. Furthermore, Ru7 displays significant antitumor activity against drug-resistant cancer cells in vivo. To the best of our knowledge, Ru7 is the first Ru-based necroptosis-inducing chemotherapeutic agent.

Double agents of cell death: novel emerging functions of apoptotic regulators

Apoptosis is a highly regulated form of cell death that is required for many homeostatic and pathological processes. Recently, alternative cell death pathways have emerged whose regulation is dependent on proteins with canonical functions in apoptosis. Dysregulation of apoptotic signaling frequently underlies the pathogenesis of many cancers, reinforcing the need to develop therapies that initiate alternative cell death processes. This review outlines the convergence points between apoptosis and other death pathways with the purpose of identifying novel strategies for the treatment of apoptosis-refractory cancers. Apoptosis proteins can play key roles in the initiation, regulation, and execution of nonapoptotic death processes that include necroptosis, autophagy, pyroptosis, mPTP-mediated necrosis, and ferroptosis. Notably, recent evidence illustrates that dying cells can exhibit biochemical and molecular characteristics of more than one different type of regulated cell death. Thus, this review highlights the amazing complexity and interconnectivity of cell death processes and also raises the idea that a top-to-bottom approach to describing cell death mechanisms may be inadequate for fully understanding the means by which cells die.

Prognostic Significance of CHIP and RIPK3 in Non-Small Cell Lung Cancer

RIPK3 is a key regulator of necroptosis, which plays a double-edged sword role in tumor progression. CHIP is an E3 ubiquitin ligase that regulates necroptosis by degrading RIPK3. Here, we investigated the prognostic value of RIPK3 and CHIP expression in 404 patients with non-small cell lung cancer (NSCLC). Expressions of CHIP and RIPK3 showed opposite correlations with survival. CHIP expression was associated with the longer overall survival (OS), whereas RIPK3 expression was associated with the shorter OS. RIPK3 positivity showed marginal association with shorter OS and disease-free survival (DFS) in adjuvant radiotherapy recipients but not in non-recipients, suggesting that necroptosis may induce radioresistance. In multivariate analysis, CHIP expression was associated with longer OS. Compared with other patients, CHIP(-)/RIPK3(+) patients had shorter OS and DFS. In summary, in patients with NSCLC, the expression of CHIP was an independent favorable prognostic factor while that of RIPK3 was an adverse prognostic factor.

CuS-NiS2 nanomaterials for MRI guided phototherapy of gastric carcinoma via triggering mitochondria-mediated apoptosis and MLKL/CAPG-mediated necroptosis

Gastric carcinoma is one of the most lethal malignant tumors. As part of our long-term efforts on seeking effective diagnosis and therapeutic strategies of gastric cancer, we present herein novel ternary copper-based chalcogenide nanoplatform CuS-NiS₂ nanomaterials with outstanding photothermal (PT)/photodynamic (PD) property that could effectively suppress human gastric cancer in vitro and in vivo without obvious side effects. We revealed that CuS-NiS₂ induced reactive oxygen species (ROS) generation, leading to apoptosis through Bcl-2/Bax pathway of human gastric cancer cells under 808 nm near-infrared (NIR) irradiation. In addition, we also confirmed that the combination of CuS-NiS₂ and 808 nm NIR laser treatment triggered necroptosis by regulating the novel pathway MLKL/CAPG of human gastric cancer cells. Moreover, the CuS-NiS₂ exhibited excellent contrast enhancement according to magnetic resonance imaging (MRI). Taken together, we reported new ternary copper-based chalcogenide nanomaterials CuS-NiS₂, which could be successfully applied for MRI-guided PT/PD therapy of gastric carcinoma through mitochondria-mediated apoptosis and MLKL/CAPG-mediated necroptosis.