MLKL-PITPα signaling-mediated necroptosis contributes to cisplatin-triggered cell death in lung cancer A549 cells

Investigation of Lung Cancer Cell Response to Cryoablation and Adjunctive Gemcitabine-Based Cryo-Chemotherapy Using the A549 Cell Line

Due to the rising annual incidence of lung cancer (LC), new treatment strategies are needed. While various options exist, many, if not all, remain suboptimal. Several studies have shown cryoablation to be a promising approach. Yet, a lack of basic information pertaining to LC response to freezing and requirement for percutaneous access has limited clinical use. In this study, we investigated the A549 lung carcinoma cell line response to freezing. The data show that a single 5 min freeze to -15 °C did not affect cell viability, whereas -20 °C and -25 °C result in a significant reduction in viability 1 day post freeze to <10%. These populations, however, were able to recover in culture. Application of a repeat (double) freeze resulted in complete cell death at -25 °C. Studies investigating the impact of adjunctive gemcitabine (75 nM) pretreatment in combination with freezing were then conducted. Exposure to gemcitabine alone resulted in minimal cell death. The combination of gemcitabine pretreatment and a -20 °C single freeze as well as combination treatment with a -15 °C repeat freeze both resulted in complete cell death. This suggests that gemcitabine pretreatment may be synergistically effective when combined with freezing. Studies into the modes of cell death associated with the increased cell death revealed the increased involvement of necroptosis in combination treatment. In summary, these results suggest that repeat freezing to -20 °C to -25 °C results in a high degree of LC destruction. Further, the data suggest that the combination of gemcitabine pretreatment and freezing resulted in a shift of the minimum lethal temperature for LC from -25 °C to -15 °C. These findings, in combination with previous reports, suggest that cryoablation alone or in combination with chemotherapy may provide an improved path for the treatment of LC.

VDAC1, as a downstream molecule of MLKL, participates in OGD/R-induced necroptosis by inducing mitochondrial damage

Ischemia-reperfusion (I/R) injury constitutes a significant risk factor for a range of diseases, including ischemic stroke, myocardial infarction, and trauma. Following the restoration of blood flow post-tissue ischemia, oxidative stress can lead to various forms of cell death, including necrosis, apoptosis, autophagy, and necroptosis. Recent evidence has highlighted the crucial role of mitochondrial dysfunction in I/R injury. Nevertheless, there remains much to be explored regarding the molecular signaling network governing cell death under conditions of oxidative stress. Voltage-dependent anion channel 1 (VDAC1), a major component in the outer mitochondrial membrane, is closely involved in the regulation of cell death. In a cellular model of oxygen-glucose deprivation and reoxygenation (OGD/R), which effectively simulates I/R injury in vitro, our study reveals that OGD/R induces VDAC1 oligomerization, consequently exacerbating cell death. Furthermore, we have revealed the translocation of mixed lineage kinase domain-like protein (MLKL) to the mitochondria, where it interacts with VDAC1 following OGD/R injury, leading to an increased mitochondrial membrane permeability. Notably, the inhibition of MLKL by necrosulfonamide hinders the binding of MLKL to VDAC1, primarily by affecting the membrane translocation of MLKL, and reduces OGD/R-induced VDAC1 oligomerization. Collectively, our findings provide preliminary evidence of the functional association between MLKL and VDAC1 in the regulation of necroptosis.

Implications of different cell death patterns for prognosis and immunity in lung adenocarcinoma

In recent years, lung adenocarcinoma (LUAD) has become a focus of attention due to its low response to treatment, poor prognosis, and lack of reliable indicators to predict the progression or therapeutic effect of LUAD. Different cell death patterns play a crucial role in tumor development and are promising for predicting LUAD prognosis. From the TCGA and GEO databases, we obtained bulk transcriptomes, single-cell transcriptomes, and clinical information. Genes in 15 types of cell death were analyzed for cell death index (CDI) signature establishment. The CDI signature using necroptosis + immunologic cell death-related genes was established in the TCGA cohort with the 1-, 2-, 3-, 4- and 5-year AUC values were 0.772, 0.736, 0.723, 0.795, and 0.743, respectively. The prognosis was significantly better in the low CDI group than in the high CDI group. We also investigated the relationship between the CDI signature and clinical variables, published prognosis biomarkers, immune cell infiltration, functional enrichment pathways, and immunity biomarkers. In vitro assay showed that HNRNPF and FGF2 promoted lung cancer cell proliferation and migration and were also involved in cell death. Therefore, as a robust prognosis biomarker, CDI signatures can screen for patients who might benefit from immunotherapy and improve diagnostic accuracy and LUAD patient outcomes.

Arsenic trioxide-induced cytotoxicity in A549 cells: The role of necroptosis

INTRODUCTION

Lung cancer is one of the deadliest cancers globally. Arsenic trioxide (ATO) is still present as a highly effective drug in treating acute promyelocytic leukemia (APL). Chemotherapy resistance is one of the major problems in cancer therapy. Necroptosis, can overcomes resistance to apoptosis, and can promote cancer treatment. This study examines the necroptosis pathway in A549 cancer cells exposed to ATO.

METHODS

We used the MTT test to determine the ATO effects on the viability of A549 cells at three different time intervals. Also, the reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were performed in three-time intervals. The effect of ATO on apoptosis was evaluated by Annexin V / PI staining and, the RIPK1 and MLKL gene expression were measured by Real-Time PCR.

RESULTS

The ATO has dose and time-dependent cytotoxic effects, so at 24, 48, and 72 h, the IC50 doses were 33.81 '11.44 '2.535 µM respectively. A 50 μM ATO is the most appropriate to increase the MMP loss significantly at all three times. At 24 and 48 h after exposure of cells to ATO, the ROS levels increased. The RIPK1 gene expression increased significantly compared to the control group at concentrations of 50 and 100 μM; however, MLKL gene expression decreased.

CONCLUSIONS

The A549 cells, after 48 h exposure to ATO at 50 and 100 μM, induces apoptosis and necroptosis. Due to the reduced expression of MLKL, it can be concluded that ATO is probably effective in the metastatic stage of cancer cells.

A necroptosis-related gene signature to predict prognosis and immune features in hepatocellular carcinoma

BACKGROUND AND AIM

Necroptosis plays an important role in hepatocellular carcinoma (HCC) development, recurrence, and immunotherapy tolerance. We aimed to build a new prognostic necroptosis-related gene signature that could be used for survival and immunotherapy prediction in HCC patients.

METHODS

We found that necroptosis was associated with HCC progression and survival outcomes and was involved in the immune infiltration of HCC. Multiple bioinformatics methods including WGCNA, LASSO-Cox regression, stepwise Cox regression, and Random Forest and Boruta model analysis, were used to establish a prognostic profile related to necroptosis. The necroptosis-related gene signature was validated in ICGC and GSE14520 datasets.

RESULTS

This five-gene signature showed excellent predictive performance and was an independent risk factor for patients' overall survival outcome in the three cohorts. Moreover, this signature was an exact predictor using fewer genes than previous gene signatures. Finally, qRT-PCR and immunohistochemical staining investigations were performed in previously collected fresh frozen tumor tissues from HCC patients and their paracancerous normal tissues, and the results were consistent with the bioinformatics results. We found that LGALS3 not only affected the proliferation and migration ability of HepG2 cells but also affected necroptosis and the expression of inflammatory cytokines.

CONCLUSION

In summary, we established and validated an individualized prognostic profile related to necroptosis to forecast the therapeutic response to immune therapy, which might offer a potential non-apoptotic therapeutic target for HCC patients.

Prussian Blue nanoparticles: An FDA-approved substance that may quickly degrade at physiological pH

Prussian blue (PB) is a coordination polymer based on the Fe^2+…CN^…Fe³⁺ sequence. It is an FDA-approved drug, intended for oral use at the acidic pH of the stomach and of most of the intestine track. However, based on FDA approval, a huge number of papers proposed the use of PB nanoparticles (PBnp) under "physiological conditions", meaning pH buffered at 7.4 and high saline concentration. While most of these papers report that PBnp are stable at this pH, a small number of papers describes instead PBnp degradation at the same or similar pH values, i.e. in the 7-8 range. Here we give a definitively clear picture: PBnp are intrinsically unstable at pH ≥ 7, degrading with the fast disappearance of their 700 nm absorption band, due to the formation of OH^- complexes from the labile Fe³⁺ centers. However, we show also that the presence of a polymeric coating (PVP) can protect PBnp at pH 7.4 for over 24 h. Moreover, we demonstrate that when "physiological conditions" include serum, a protein corona is rapidly formed on PBnp, efficiently avoiding degradation. We also show that the viability of PBnp-treated EA.hy926, NCI-H1299, and A549 cells is not affected in a wide range of conditions that either prevent or promote PBnp degradation.

A novel mechanism of 6-methoxydihydroavicine in suppressing ovarian carcinoma by disrupting mitochondrial homeostasis and triggering ROS/ MAPK mediated apoptosis

Introduction: Alkaloids derived from M. cordata (Papaveraceae family), have been found to display antineoplastic activity in several types of cancer. However, the antitumor effects and mechanisms of a new alkaloid extracted from the fruits of M. cordata, named 6-Methoxydihydroavicine (6-ME), remains unclear in the case of ovarian cancer (OC). Methods: CCK-8 assay was employed to analyze the cell viabilities of OC cells. RTCA, and colony-formation assays were performed to measure OC cell growth. Alterations in apoptosis and ROS levels were detected by flow cytometry in accordance with the instructions of corresponding assay kits. A Seahorse XFe96 was executed conducted to confirm the effects of 6-ME on cellular bioenergetics. Western blot and q-RT-PCR were conducted to detect alterations in target proteins. The subcutaneous xenografted tumor model of OC was used to further validate the anti-tumor activity of 6-ME in vivo. Results: Here, we reported for the first time that 6-ME inhibits OC cells growth in vitro and in vivo. Meanwhile, we found that 6-ME showed great antineoplastic activities by disrupting mitochondria homeostasis and promoting apoptosis in OC cells. Further investigation of the upstream signaling of apoptosis revealed that 6-ME-triggered apoptosis was induced by reactive oxygen species (ROS)-mediated mitogen-activated protein kinase (MAPK) activation and mitochondria dysfunction in OC cells. Furthermore, we found oxaloacetic acid (OAA), a crucial metabolite has been proved to be related to NADPH production, can block the cytotoxicity and accumulation of ROS caused by 6-ME in OC cells. Discussion: In summary, our data show that 6-ME exhibits cytotoxicity to OC cells in a ROS-dependent manner by interrupting mitochondrial respiration homeostasis and inducing MAPK-mediated apoptosis. This evidence suggests that 6-ME is a promising remedy for OC intervention.

Necroptosis pathways in tumorigenesis

Necroptosis is a caspase-independent form of programmed cell death executed by the receptor interacting protein kinase 1 (RIPK1)-RIPK3-mixed lineage kinase domain-like protein (MLKL) signaling cascade, deregulation of which can cause various human diseases including cancer. Escape from programmed cell death is a hallmark of cancer, leading to uncontrolled growth and drug resistance. Therefore, it is crucial to further understand whether necroptosis plays a key role in therapeutic resistance. In this review, we summarize the recent findings of the link between necroptosis and cancer, and discuss that targeting necroptosis is a new strategy to overcome apoptosis resistance in tumor therapy.

The Prediction of Necroptosis-Related lncRNAs in Prognosis and Anticancer Therapy of Colorectal Cancer

Background

Colorectal cancer is one of the most common gastrointestinal malignancies globally. Necroptosis has been proved to play a role in the occurrence and development of the tumor, which makes it a new target for molecular therapy. However, the role of necroptosis in colorectal cancer remains unknown yet. Our study aims to build a prognostic signature of necroptosis-related lncRNAs (nrlncRNAs) to predict the outcomes of patients with colorectal cancer and facilitate in anticancer therapy.

Method

We obtained RNA-seq and clinical data of colorectal adenocarcinoma from the TCGA database and got prognosis-related nrlncRNAs by univariate regression analysis. Then, we carried out the LASSO regression and multivariate regression analysis to build the prognostic signature, whose predictive ability was tested by the Kaplan-Meier as well as ROC curves and verified by the internal cohort. Moreover, we divided the cohort into 2 groups based on median of risk scores: high- and low-risk groups. By analyzing the difference in the tumor microenvironment, microsatellite instability, and tumor mutation burden between the two groups, we explored the potential chemotherapy and immunotherapy drugs.

Results

We screened out 9 nrlncRNAs and built a prognostic signature based on them. With its good prognostic ability, the risk scores can act as an independent prognostic factor for patients with colorectal cancer. The overall survival rate of patients in high-risk group was significantly higher than the low-risk one. Furthermore, risk scores can also give us hints about the tumor microenvironment and facilitate in predicting the response to the CTLA-4 blocker treatment and other chemotherapeutic agents with potential efficacy such as cisplatin and staurosporine.

Conclusions

In conclusion, our prognostic signature of necroptosis-related lncRNAs can facilitate in predicting the prognosis and response to the anticancer therapy of colorectal cancer patients.

The protective effect of rabeprazole on cisplatin-induced apoptosis and necroptosis of renal proximal tubular cells

Nephrotoxicity is a major adverse reaction of cisplatin-based chemotherapy. Organic cation transporter 2 (OCT2) which is located on the basement membrane of human proximal renal tubules is responsible for the renal accumulation of cisplatin and its nephrotoxicity. This study aimed to investigate the protective effect of PPIs to CP-induced nephrotoxicity. Three kinds of PPIs including lansoprazole, omeprazole and rabeprazole (Rab) were co-administrated with CP to mice. In addition, OCT2-overexpressed HEK293, HK-2 and A549 cells were co-incubated with CP and PPIs. The results showed that PPIs can attenuate CP-induced increase of CRE, BUN and histological damage of kidney. Among the three PPIs, Rab was found with a superior protective effect. It significantly reduced the accumulation of CP in OCT2-overexpressed HEK293 cells and in the renal cortex tissues of mice, but not in HK-2 cells. Moreover, Rab reduced the expression levels of cleaved-caspase-3, RIPK1, RIPK3, MLKL and p-MLKL and the apoptosis rate of renal tubular cells induced by CP in vivo, but not in HK-2 cells. However, Rab increased the viability of CP-treated cells in a concentration-dependent manner and attenuated CP-induced apoptosis and necroptosis in OCT2 over-expressed HEK293 cells. Finally, we demonstrated that Rab have no influence on the antitumor effect of CP. In conclusion, Rab attenuate CP-induced nephrotoxicity mainly through inhibiting OCT2-mediated CP uptake, without interfering with its anti-tumor property of inducing apoptosis and necroptosis.

Upregulation of wild-type p53 by small molecule-induced elevation of NQO1 in non-small cell lung cancer cells

The tumor suppressor p53 is usually inactivated by somatic mutations in malignant neoplasms, and its reactivation represents an attractive therapeutic strategy for cancers. Here, we reported that a new quinolone compound RYL-687 significantly inhibited non-small cell lung cancer (NSCLC) cells which express wild type (wt) p53, in contract to its much weaker cytotoxicity on cells with mutant p53. RYL-687 upregulated p53 in cells with wt but not mutant p53, and ectopic expression of wt p53 significantly enhanced the anti-NSCLC activity of this compound. RYL-687 induced production of reactive oxygen species (ROS) and upregulation of Nrf2, leading to an elevation of the NAD(P)H:quinoneoxidoreductase-1 (NQO1) that can protect p53 by inhibiting its degradation by 20S proteasome. RYL-687 bound NQO1, facilitating the physical interaction between NQO1 and p53. NQO1 was required for RYL-687-induced p53 accumulation, because silencing of NQO1 by specific siRNA or an NQO1 inhibitor uridine, drastically suppressed RYL-687-induced p53 upregulation. Moreover, a RYL-687-related prodrug significantly inhibited tumor growth in NOD-SCID mice inoculated with NSCLC cells and in a wt p53-NSCLC patient-derived xenograft mouse model. These data indicate that targeting NQO1 is a rational strategy to reactivate p53, and RYL-687 as a p53 stabilizer bears therapeutic potentials in NSCLCs with wt p53.

Stratifin promotes renal dysfunction in ischemic and nephrotoxic AKI mouse models via enhancing RIPK3-mediated necroptosis

Stratifin (SFN) is a member of the 14-3-3 family of highly conserved soluble acidic proteins, which regulates a variety of cellular activities such as cell cycle, cell growth and development, cell survival and death, and gene transcription. Acute kidney injury (AKI) is prevalent disorder characterized by inflammatory response, oxidative stress, and programmed cell death in renal tubular epithelial cells, but there is still a lack of effective therapeutic target for AKI. In this study, we investigated the role of SFN in AKI and the underlying mechanisms. We established ischemic and nephrotoxic AKI mouse models caused by ischemia-reperfusion (I/R) and cisplatin, respectively. We conducted proteomic and immunohistochemical analyses and found that SFN expression levels were significantly increased in AKI patients, cisplatin- or I/R-induced AKI mice. In cisplatin- or hypoxia/reoxygenation (H/R)-treated human proximal tubule epithelial cells (HK2), we showed that knockdown of SFN significantly reduced the expression of kidney injury marker Kim-1, attenuated programmed cell death and inflammatory response. Knockdown of SFN also significantly alleviated the decline of renal function and histological damage in cisplatin-caused AKI mice in vivo. We further revealed that SFN bound to RIPK3, a key signaling modulator in necroptosis, to induce necroptosis and the subsequent inflammation in cisplatin- or H/R-treated HK2 cells. Overexpression of SFN increased Kim-1 protein levels in cisplatin-treated MTEC cells, which was suppressed by RIPK3 knockout. Taken together, our results demonstrate that SFN that enhances cisplatin- or I/R-caused programmed cell death and inflammation via interacting with RIPK3 may serve as a promising therapeutic target for AKI treatment.

Necroptosis in Pulmonary Diseases: A New Therapeutic Target

In the past decades, apoptosis has been the most well-studied regulated cell death (RCD) that has essential functions in tissue homeostasis throughout life. However, a novel form of RCD called necroptosis, which requires receptor-interacting protein kinase-3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), has recently been receiving increasing scientific attention. The phosphorylation of RIPK3 enables the recruitment and phosphorylation of MLKL, which oligomerizes and translocates to the plasma membranes, ultimately leading to plasma membrane rupture and cell death. Although apoptosis elicits no inflammatory responses, necroptosis triggers inflammation or causes an innate immune response to protect the body through the release of damage-associated molecular patterns (DAMPs). Increasing evidence now suggests that necroptosis is implicated in the pathogenesis of several human diseases such as systemic inflammation, respiratory diseases, cardiovascular diseases, neurodegenerative diseases, neurological diseases, and cancer. This review summarizes the emerging insights of necroptosis and its contribution toward the pathogenesis of lung diseases.

Necrosulfonamide reverses pyroptosis-induced inhibition of proliferation and differentiation of osteoblasts through the NLRP3/caspase-1/GSDMD pathway

The acute inflammatory stimulation occurring after a bone fracture regulates the repair and healing of local bone injury; however, under certain conditions, pyroptosis may occur in osteoblasts, which affects osteoblast proliferation and differentiation, thereby affecting the growth, development and morphological changes of bone tissue. The aim of the present study was to examine the effect of the pyroptosis inhibitor necrosulfonamide (NSA) on the proliferation and differentiation of osteoblasts and elucidate the underlying mechanism. The results revealed that NSA reversed the effects of ATP/lipopolysaccharide (LPS) on cell viability and pyroptosis, and on the mRNA and protein expression of pyroptosis-related genes. It also suppressed the secretion of IL-6, TNF-α and IL-1β and reversed the effects of ATP/LPS on the activity of ALP and the mRNA expression of differentiation-related genes in osteoblasts. The fact that overexpression of caspase-1, gasdermin D (GSDMD) and NLRP3 abolished the effects of NSA on the viability and pyroptosis of osteoblasts, as well as the mRNA expression of differentiation-related genes and the activity of ALP in osteoblasts, indicated that NSA promoted the proliferation and differentiation of osteoblasts by inhibiting the NLRP3/caspase-1/GSDMD pyroptosis pathway. The present study provides proof supporting the potential application of NSA for improving the function of osteoblasts in fracture repair and indicates the value of the NLRP3/caspase-1/GSDMD pyroptosis pathway as a pharmaceutical target.

MLKL in cancer: more than a necroptosis regulator

Mixed lineage kinase domain-like protein (MLKL) emerged as executioner of necroptosis, a RIPK3-dependent form of regulated necrosis. Cell death evasion is one of the hallmarks of cancer. Besides apoptosis, some cancers suppress necroptosis-associated mechanisms by for example epigenetic silencing of RIPK3 expression. Conversely, necroptosis-elicited inflammation by cancer cells can fuel tumor growth. Recently, necroptosis-independent functions of MLKL were unraveled in receptor internalization, ligand-receptor degradation, endosomal trafficking, extracellular vesicle formation, autophagy, nuclear functions, axon repair, neutrophil extracellular trap (NET) formation, and inflammasome regulation. Little is known about the precise role of MLKL in cancer and whether some of these functions are involved in cancer development and metastasis. Here, we discuss current knowledge and controversies on MLKL, its structure, necroptosis-independent functions, expression, mutations, and its potential role as a pro- or anti-cancerous factor. Analysis of MLKL expression patterns reveals that MLKL is upregulated by type I/II interferon, conditions of inflammation, and tissue injury. Overall, MLKL may affect cancer development and metastasis through necroptosis-dependent and -independent functions.

Polychlorinated biphenyl quinone regulates MLKL phosphorylation that stimulates exosome biogenesis and secretion via a short negative feedback loop

Polychlorinated biphenyls (PCBs) are one of the most refractory organic environmental pollutants that ubiquitous existence in nature. Due to the polymorphism of their metabolic pathway and corresponding downstream metabolites, PCBs' toxicities are complicated and need extended investigation. In the present study, we discovered a novel regulatory mechanism of PCB quinone metabolite-driven programmed cell death (PCD), namely, necroptosis. We first confirmed that PCB quinone induces cancerous HeLa and MDA-MB-231 cells necroptosis via the phosphorylation of mixed lineage kinase domain-like MLKL (p-MLKL). Then, we found that PCB quinone-stimulated p-MLKL enhances exosome biogenesis and secretion. Exosome interacts with p-MLKL and releases p-MLKL to the outside of the cell, and ultimately alleviating PCB quinone-induced necroptosis. The inhibition of exosome secretion by GW4869 significantly elevated necroptotic level, indicating the establishment of a short negative feedback loop of MLKL-exosome secretion upon PCB quinone challenge. Since exosome-mediated signaling showed great implications in various human diseases, this work may provide a new mechanism for PCBs-associated toxicity.

Visualization of Necroptotic Cell Death through Transmission Electron Microscopy

Transmission electron microscopy (TEM) is an all-in-one tool to visualize the complex systems of any specimen that is 1 nm in size or smaller. The current chapter provides detailed guidelines for imaging morphological changes during programmed cell necrosis using TEM as a single-step methodology. In this protocol, a novel aldehyde dehydrogenase inhibitor is used to induce cell programmed necrosis in ovarian cancer cell lines (A2780 and SKOV3). This process is followed by gradient dehydration with ethanol, chemical fixation, sampled grid preparation, and staining with 0.75% uranyl formate. Following fixation and grid preparation, cells are imaged using TEM. The resulting images reveal morphological changes consistent with necrotic morphology, including swelling of cells and organelles, appearance of vacuoles, and plasma membrane rupture followed by leakage of cellular contents. The current approach allows a single-step methodology for characterization of cell-programmed necrosis in cells based on morphology.

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.

Necroptosis in Immuno-Oncology and Cancer Immunotherapy

Immune-checkpoint blockers (ICBs) have revolutionized oncology and firmly established the subfield of immuno-oncology. Despite this renaissance, a subset of cancer patients remain unresponsive to ICBs due to widespread immuno-resistance. To "break" cancer cell-driven immuno-resistance, researchers have long floated the idea of therapeutically facilitating the immunogenicity of cancer cells by disrupting tumor-associated immuno-tolerance via conventional anticancer therapies. It is well appreciated that anticancer therapies causing immunogenic or inflammatory cell death are best positioned to productively activate anticancer immunity. A large proportion of studies have emphasized the importance of immunogenic apoptosis (i.e., immunogenic cell death or ICD); yet, it has also emerged that necroptosis, a programmed necrotic cell death pathway, can also be immunogenic. Emergence of a proficient immune profile for necroptosis has important implications for cancer because resistance to apoptosis is one of the major hallmarks of tumors. Putative immunogenic or inflammatory characteristics driven by necroptosis can be of great impact in immuno-oncology. However, as is typical for a highly complex and multi-factorial disease like cancer, a clear cause versus consensus relationship on the immunobiology of necroptosis in cancer cells has been tough to establish. In this review, we discuss the various aspects of necroptosis immunobiology with specific focus on immuno-oncology and cancer immunotherapy.

Development and Characterization of Biocompatible Mannose Functionalized Mesospheres: an Effective Chemotherapeutic Approach for Lung Cancer Targeting

The aim of the present study was to analyze the lung targeting potential of surface engineered mesospheres loaded with doxorubicin hydrochloride (DOX). Gelatin-based DOX encapsulated mesospheres were prepared using a steric stabilization process and surface modified with mannose, using the amino group present on the surface of the mesospheres. Gelatin-DOX-mesospheres (M₁) and gelatin-mannosylated-DOX-mesospheres (M₂) were characterized for particle size, polydispersity index, zeta potential, and % entrapment efficiency which were found respectively 8.7 ± 0.35, 0.671 ± 0.018, 1.74 ± 0.27, and 80.4 ± 1.2 for (M₁) and 9.8 ± 0.41, 0.625 ± 0.010, 0.85 ± 0.11, and 75.1 ± 0.7 for (M₂). Furthermore, the mesospheres were characterized by FTIR, DSC, SEM, and TEM. In vitro drug release study of optimized formulation was carried out using the dialysis tube method. The cumulative percent drug release was found to be 79.2 ± 0.1% and 69.6 ± 0.52% respectively for gelatin-DOX-mesospheres and gelatin-mannosylated-DOX-mesospheres. In vitro cytotoxicity of formulations was determined using xenograft A-549 tumor cell lines. The cytotoxicity recorded as IC₅₀ was more in the case of M₂ compared to M₁. In addition, mesospheres exhibited minimal hemolytic toxicity and appear to be promising for sustained drug delivery of DOX to the lungs. Cytotoxicity assay was conducted on the A-549 cell line. The results revealed that gelatin-mannosylated-DOX-mesospheres were maximally cytotoxic as compared to free DOX as well as gelatin-DOX-mesospheres. The lung's accumulation of drug was measured and found maximum after administration of M₂. It may, therefore, be inferred that gelatin-mannosylated-DOX-mesospheres are capable to carry bioactive(s) and can be used specifically to target the lung cancer with minimal side effects.

Pidotimod enhanced the anti-growth effect of cisplatin on lung cancer in mice via promoting anti-tumor immune response

Cisplatin-based chemotherapeutics represent a mainstay of lung cancer therapy, but resistance limits their curative potential. In the current study, we reported that Pidotimod, which is an immunostimulant and used for the prevention of acute respiratory infections, elevated cisplatin sensitivity, leading to the synergistic attenuation of tumor growth in mouse lewis lung cancer (LLC) model. With further exploration, we found that Pidotimod enhanced the anti-growth effect of cisplatin on LLC via promoting anti-tumor response, such as increased infiltration of dendrite cells (DCs) and CD8⁺ T cells as well as enhancement of IFN-γ and Granzyme B expression. In summary, Pidotimod affects the anti-tumor function of cisplatin via promoting anti-tumor immune response and these findings provide a novel approach for the development of therapeutic strategies for lung cancer.

DHA attenuates Aβ-induced necroptosis through the RIPK1/RIPK3 signaling pathway in THP-1 monocytes

Monocytes play a crucial role in Alzheimer's disease (AD), and docosahexaenoic acid (DHA) has a neuroprotective effect for many neurodegenerative diseases. However, mechanisms that regulate monocyte and Aβ protein interaction in AD and the effects of DHA on monocytes in the context of AD are not fully understood. The experiments were designed to further explore possible mechanisms of interaction between monocytes and Aβ plaques. Another objective of this study was to investigate a potential mechanism for Aβ-induced necroptosis involving the activation of MAPK and NF-kB signaling pathways in human THP-1 monocytes, as well as how these pathways might be modulated by DHA. Our findings indicate that Aβ25-35 has a "Hormesis" effect on cell viability and necroptosis in THP-1 cells, and Aβ25-35 influences THP-1 cells differentiation as analyzed by flow cytometry. Pretreatment of THP-1 monocytes with DHA effectively inhibited Aβ-induced activation and markedly suppressed protein expression of necroptosis (RIPK1, RIPK3, MLKL) and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6). Moreover, our findings indicate that Aβ25-35 activated the ERK1/2 and p38 signaling pathways, but not NF-κB/p65 signaling, while pre-treatment with DHA followed by Aβ25-35 treatment suppressed only ERK1/2 signaling. Further study revealed that the expression level of RIPK3 is reduced much more during coadministration with DHA and necrostatin-1 (NEC-1) than administration alone with either of them, indicating that DHA may have additional targets. Meanwhile, this finding indicates that DHA can prevent Aβ-induced necroptosis of THP-1 cells via the RIPK1/RIPK3 signaling pathway. Our results also indicate that DHA treatment restored migration of THP-1 monocytes induced by Aβ25-35, and DHA treatment could be a promising new therapy for AD management.

Fenretinide induces a new form of dynamin-dependent cell death in pediatric sarcoma

Alveolar rhabdomyosarcoma (aRMS) is a highly malicious childhood malignancy characterized by specific chromosomal translocations mostly encoding the oncogenic transcription factor PAX3-FOXO1 and therefore also referred to as fusion-positive RMS (FP-RMS). Previously, we have identified fenretinide (retinoic acid p-hydroxyanilide) to affect PAX3-FOXO1 expression levels as well as FP-RMS cell viability. Here, we characterize the mode of action of fenretinide in more detail. First, we demonstrate that fenretinide-induced generation of reactive oxygen species (ROS) depends on complex II of the mitochondrial respiratory chain, since ROS scavenging as well as complexing of iron completely abolished cell death. Second, we co-treated cells with a range of pharmacological inhibitors of specific cell death pathways including z-vad (apoptosis), necrostatin-1 (necroptosis), 3-methyladenine (3-MA) (autophagy), and ferrostatin-1 (ferroptosis) together with fenretinide. Surprisingly, none of these inhibitors was able to prevent cell death. Also genetic depletion of key players in the apoptotic and necroptotic pathway (BAK, BAX, and RIPK1) confirmed the pharmacological data. Interestingly however, electron microscopy of fenretinide-treated cells revealed an excessive accumulation of cytoplasmic vacuoles, which were distinct from autophagosomes. Further flow cytometry and fluorescence microscopy experiments suggested a hyperstimulation of macropinocytosis, leading to an accumulation of enlarged early and late endosomes. Surprisingly, pharmacological inhibition as well as genetic depletion of large dynamin GTPases completely abolished fenretinide-induced vesicle formation and subsequent cell death, suggesting a new form of dynamin-dependent programmed cell death. Taken together, our data identify a new form of cell death mediated through the production of ROS by fenretinide treatment, highlighting the value of this compound for treatment of sarcoma patients including FP-RMS.

Current translational potential and underlying molecular mechanisms of necroptosis

Cell death has a fundamental impact on the evolution of degenerative disorders, autoimmune processes, inflammatory diseases, tumor formation and immune surveillance. Over the past couple of decades extensive studies have uncovered novel cell death pathways, which are independent of apoptosis. Among these is necroptosis, a tightly regulated, inflammatory form of cell death. Necroptosis contribute to the pathogenesis of many diseases and in this review, we will focus exclusively on necroptosis in humans. Necroptosis is considered a backup mechanism of apoptosis, but the in vivo appearance of necroptosis indicates that both caspase-mediated and caspase-independent mechanisms control necroptosis. Necroptosis is regulated on multiple levels, from the transcription, to the stability and posttranslational modifications of the necrosome components, to the availability of molecular interaction partners and the localization of receptor-interacting serine/threonine-protein kinase 1 (RIPK1), receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL). Accordingly, we classified the role of more than seventy molecules in necroptotic signaling based on consistent in vitro or in vivo evidence to understand the molecular background of necroptosis and to find opportunities where regulating the intensity and the modality of cell death could be exploited in clinical interventions. Necroptosis specific inhibitors are under development, but >20 drugs, already used in the treatment of various diseases, have the potential to regulate necroptosis. By listing necroptosis-modulated human diseases and cataloging the currently available drug-repertoire to modify necroptosis intensity, we hope to kick-start approaches with immediate translational potential. We also indicate where necroptosis regulating capacity should be considered in the current applications of these drugs.

The DNA-damage response and nuclear events as regulators of nonapoptotic forms of cell death

The maintenance of genome stability is essential for the cell as the integrity of genomic information guaranties reproduction of a whole organism. DNA damage occurring in response to different natural and nonnatural stimuli (errors in DNA replication, UV radiation, chemical agents, etc.) is normally detected by special cellular machinery that induces DNA repair. However, further accumulation of genetic lesions drives the activation of cell death to eliminate cells with defective genome. This particular feature is used for targeting fast-proliferating tumor cells during chemo-, radio-, and immunotherapy. Among different cell death modalities induced by DNA damage, apoptosis is the best studied. Nevertheless, nonapoptotic cell death and adaptive stress responses are also activated following genotoxic stress and play a crucial role in the outcome of anticancer therapy. Here, we provide an overview of nonapoptotic cell death pathways induced by DNA damage and discuss their interplay with cellular senescence, mitotic catastrophe, and autophagy.

Guidelines for evaluating myocardial cell death

Cell death is a fundamental process in cardiac pathologies. Recent studies have revealed multiple forms of cell death, and several of them have been demonstrated to underlie adverse cardiac remodeling and heart failure. With the expansion in the area of myocardial cell death and increasing concerns over rigor and reproducibility, it is important and timely to set a guideline for the best practices of evaluating myocardial cell death. There are six major forms of regulated cell death observed in cardiac pathologies, namely apoptosis, necroptosis, mitochondrial-mediated necrosis, pyroptosis, ferroptosis, and autophagic cell death. In this article, we describe the best methods to identify, measure, and evaluate these modes of myocardial cell death. In addition, we discuss the limitations of currently practiced myocardial cell death mechanisms.

C-Phycocyanin Suppresses the In Vitro Proliferation and Migration of Non-Small-Cell Lung Cancer Cells through Reduction of RIPK1/NF-κB Activity

Phycocyanin, derived from Spirulina platensis, is a type of natural antineoplastic marine protein. It is known that phycocyanin exerts anticancer effects on non-small-cell lung cancer (NSCLC) cells, but its underlying mechanism has not been elucidated. Herein, the antitumor function and regulatory mechanism of phycocyanin were investigated in three NSCLC cell lines for the first time: H358, H1650, and LTEP-a2. Cell phenotype experiments suggested that phycocyanin could suppress the survival rate, proliferation, colony formation, and migration abilities, as well as induce apoptosis of NSCLC cells. Subsequently, transcriptome analysis revealed that receptor-interacting serine/threonine-protein kinase 1 (RIPK1) was significantly down-regulated by phycocyanin in the LTEP-a2 cell, which was further validated by qRT-PCR and Western blot analysis in two other cell lines. Interestingly, similar to phycocyanin-treated assays, siRNA knockdown of RIPK1 expression also resulted in growth and migration inhibition of NSCLC cells. Moreover, the activity of NF-κB signaling was also suppressed after silencing RIPK1 expression, indicating that phycocyanin exerted anti-proliferative and anti-migratory function through down-regulating RIPK1/NF-κB activity in NSCLC cells. This study proposes a mechanism of action for phycocyanin involving both NSCLC apoptosis and down regulation of NSCLC genes.

Role of Retinoic Acid Receptor-γ in DNA Damage-Induced Necroptosis

DNA-damaging compounds, commonly used as chemotherapeutic drugs, are known to trigger cells to undergo programmed cell death such as apoptosis and necroptosis. However, the molecular mechanism of DNA damage-induced cell death is not fully understood. Here, we report that RARγ has a critical role in DNA damage-induced programmed cell death, specifically in necroptosis. The loss of RARγ abolishes the necroptosis induced by DNA damage. In addition, cells that lack RARγ are less susceptible to extrinsic apoptotic pathway activated by DNA-damaging agents whereas the intrinsic apoptotic pathway is not affected. We demonstrate that RARγ is essential for the formation of RIPK1/RIPK3 death complex, known as Ripoptosome, in response to DNA damage. Furthermore, we show that RARγ plays a role in skin cancer development by using RARγ1 knockout mice and human squamous cell carcinoma biopsies. Hence, our study reveals that RARγ is a critical component of DNA damage-induced cell death.

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RARγ plays a key role in DNA damage-induced cell death

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RARγ is essential for RIPK1-mediated necroptosis and apoptosis following DNA damage

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RARγ is required for the formation of Ripoptosome in response to DNA damage

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Loss of RARγ correlates with skin cancer development

Redox biology of regulated cell death in cancer: A focus on necroptosis and ferroptosis

Redox changes and generation of reactive oxygen species (ROS) are part of normal cell metabolism. While low ROS levels are implicated in cellular signaling pathways necessary for survival, higher levels play major roles in cancer development as well as cell death signaling and execution. A role for redox changes in apoptosis has been long established; however, several new modalities of regulated cell death have been brought to light, for which the importance of ROS production as well as ROS source and targets are being actively investigated. In this review, we summarize recent findings on the role of ROS and redox changes in the activation and execution of two major forms of regulated cell death, necroptosis and ferroptosis. We also discuss the potential of using modulators of these two forms of cell death to exacerbate ROS as a promising anticancer therapy.

2-Deoxyglucose-Modified Folate Derivative: Self-Assembling Nanoparticle Able to Load Cisplatin

Folic acid has been widely introduced into nano-drug delivery systems to give nanoparticle-targeted characteristics. However, the poor water solubility of folic acid may hinder the exploitation of its ability to load antineoplastic drugs. In the present study, we designed a new folate derivative (FA-2-DG) synthesized from folic acid and 2-Deoxyglucose (2-DG). The aim of this study was to evaluate the self-assembly characteristics of FA-2-DG, and its ability of loading cisplatin. The critical micelle concentration was 7.94 × 10^-6 mol L^-1. Fourier transform infrared spectroscopy indicated that hydrogen bonding interaction is a main driving force for the self⁻assembly of FA-2-DG. The particle was stable in pure water or 0.5% bovine serum albumin dispersions. By forming a coordination bond, the particles assembled from FA-2-DG can load cisplatin. The loading efficiency was maximal when the molar ratio of FA-2-DG to cisplatin was 2:1.

The NS1 Protein of Influenza A Virus Participates in Necroptosis by Interacting with MLKL and Increasing Its Oligomerization and Membrane Translocation

Elimination of infected cells by programmed cell death is a well-recognized host defense mechanism to control the spread of infection. In addition to apoptosis, necroptosis is also one of the mechanisms of cell death that can be activated by viral infection. Activation of necroptosis leads to the phosphorylation of mixed-lineage kinase domain-like protein (MLKL) by receptor-interacting protein kinase 3 (RIPK3) and results in MLKL oligomerization and membrane translocation, leading to membrane disruption and a loss of cellular ion homeostasis. It has recently been reported that influenza A virus (IAV) infection induces necroptosis. However, the underlying mechanism of the IAV-mediated necroptosis process, particularly the roles of IAV proteins in necroptosis, remains unexplored. Here, we report that IAV infection induces necroptosis in macrophages and epithelial cells. We demonstrate that the NS1 protein of IAV interacts with MLKL. Coiled-coil domain 2 of MLKL has a predominant role in mediating the MLKL interaction with NS1. The interaction of NS1 with MLKL increases MLKL oligomerization and membrane translocation. Moreover, the MLKL-NS1 interaction enhances MLKL-mediated NLRP3 inflammasome activation, leading to increased interleukin-1β (IL-1β) processing and secretion.IMPORTANCE Necroptosis is a programmed cell death that is inflammatory in nature owing to the release of danger-associated molecular patterns from the ruptured cell membrane. However, necroptosis also constitutes an important arm of host immune responses. Thus, a balanced inflammatory response determines the disease outcome. We report that the NS1 protein of IAV participates in necroptosis by interacting with MLKL, resulting in increased MLKL oligomerization and membrane translocation. These results reveal a novel function of the NS1 protein and the mechanism by which IAV induces necroptosis. Moreover, we show that this interaction enhances NLRP3 inflammasome activation and IL-1β processing and secretion. This information may contribute to a better understanding of the role of necroptosis in IAV-induced inflammation.

Bulnesia sarmientoi Supercritical Fluid Extract Exhibits Necroptotic Effects and Anti-Metastatic Activity on Lung Cancer Cells

Bulnesia sarmientoi (BS) has long been used as an analgesic, wound-healing and anti-inflammatory medicinal plant. The aqueous extract of its bark has been demonstrated to have anti-cancer activity. This study investigated the anti-proliferative and anti-metastatic effects of BS supercritical fluid extract (BSE) on the A549 and H661 lung cancer cell lines. The cytotoxicity on cancer cells was assessed by an MTT assay. After 72 h treatment of A549 and H661 cells, the IC₅₀ values were 18.1 and 24.7 μg/mL, respectively. The cytotoxicity on MRC-5 normal cells was relatively lower (IC₅₀ = 61.1 μg/mL). BSE arrested lung cancer cells at the S and G₂/M growth phase. Necrosis of A549 and H661 cells was detected by flow cytometry with Annexin V-FITC/PI double staining. Moreover, the cytotoxic effect of BSE on cancer cells was significantly reverted by Nec-1 pretreatment, and BSE induced TNF-α and RIP-1 expression in the absence of caspase-8 activity. These evidences further support that BSE exhibited necroptotic effects on lung cancer cells. By wound healing and Boyden chamber assays, the inhibitory effects of BSE on the migration and invasion of lung cancer cells were elucidated. Furthermore, the chemical composition of BSE was examined by gas chromatography-mass analysis where ten constituents of BSE were identified. α-Guaiene, (−)-guaiol and β-caryophyllene are responsible for most of the cytotoxic activity of BSE against these two cancer cell lines. Since BSE possesses significant cytotoxicity and anti-metastatic activity on A549 and H661 cells, it may serve as a potential target for the treatment of lung cancer.

Comparing the effects of different cell death programs in tumor progression and immunotherapy

Our conception of programmed cell death has expanded beyond apoptosis to encompass additional forms of cell suicide, including necroptosis and pyroptosis; these cell death modalities are notable for their diverse and emerging roles in engaging the immune system. Concurrently, treatments that activate the immune system to combat cancer have achieved remarkable success in the clinic. These two scientific narratives converge to provide new perspectives on the role of programmed cell death in cancer therapy. This review focuses on our current understanding of the relationship between apoptosis and antitumor immune responses and the emerging evidence that induction of alternate death pathways such as necroptosis could improve therapeutic outcomes.

Curcumol induces RIPK1/RIPK3 complex-dependent necroptosis via JNK1/2-ROS signaling in hepatic stellate cells

It is generally recognized that hepatic fibrogenesis is an end result of increased extracellular matrix (ECM) production from the activation and proliferation of hepatic stellate cells (HSCs). An in-depth understanding of the mechanisms of HSC necroptosis might provide a new therapeutic strategy for prevention and treatment of hepatic fibrosis. In this study, we attempted to investigate the effect of curcumol on necroptosis in HSCs, and further to explore the molecular mechanisms. We found that curcumol ameliorated the carbon tetrachloride (CCl₄)-induced mice liver fibrosis and suppressed HSC proliferation and activation, which was associated with regulating HSC necroptosis through increasing the phosphorylation of receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3). Moreover, curcumol promoted the migration of RIPK1 and RIPK3 into necrosome in HSCs. RIPK3 depletion impaired the anti-fibrotic effect of curcumol. Importantly, we showed that curcumol-induced RIPK3 up-regulation significantly increased mitochondrial reactive oxygen species (ROS) production and mitochondrial depolarization. ROS scavenger, N-acetyl-L-cysteine (NAC) impaired RIPK3-mediated necroptosis. In addition, our study also identified that the activation of c-Jun N-terminal kinase1/2 (JNK1/2) was regulated by RIPK3, which mediated curcumol-induced ROS production. Down-regulation of RIPK3 expression, using siRIPK3, markedly abrogated JNK1/2 expression. The use of specific JNK1/2 inhibitor (SP600125) resulted in the suppression of curcumol-induced ROS production and mitochondrial depolarization, which in turn, contributed to the inhibition of curcumol-triggered necroptosis. In summary, our study results reveal the molecular mechanism of curcumol-induced HSC necroptosis, and suggest a potential clinical use of curcumol-targeted RIPK1/RIPK3 complex-dependent necroptosis via JNK1/2-ROS signaling for the treatment of hepatic fibrosis.

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Curcumol exerted anti-hepatic fibrogenesis effects in CCl₄-treated mice.

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Curcumol inhibited the activation of hepatic stellate cell in vitro.

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Curcumol promoted the generation of RIPK1/RIPK3-complex to induce hepatic stellate cell necroptosis.

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Curcumol modulated RIPK3/JNK/ROS signaling axis.