Cell Death Subroutines Research Articles

Immunohistochemistry for Assessing Toxicity and Mechanism of Action of Anticancer Drugs During Preclinical Trials. Part II. Cell Death, Vasculogenesis and Angiogenesis

About 120 chemical compounds are registered in Russia as anticancer drugs, and screening and investigation of novel therapies remain an urgent task for specialists in pathophysiology, pharmacology and oncology. Among them, treatments targeting neovascularisation and regulated cell death of atypical cells within the malignant tumours are of utmost importance. Hence, development of novel anti-cancer drugs must include testing of their pro-apoptotic and anti-angiogenic activity. Here we review the markers of angiogenesis and regulated cell death during the tumor development and the respective immunohistochemical applications for preclinical trials. Here we discuss relevant molecular markers for studying primary cell death subroutines which can be targeted by anticancer agents. The most sensitive and specific immunohistochemical markers of programmed cell death are tumor necrosis factor alpha (TNF-α) for necrosis and anti-cellular apoptosis susceptibility/CSE1L, Bcl-2, and apoptotic protease activating factor-1 (APAF1) for apoptosis. Primary markers of angiogenesis include vascular endothelial growth factor A (VEGF-A), hypoxia-inducible factor 1-alpha (HIF-1α), and platelet-derived growth factor (PDGF). Analysis of tumour blood supply, metastasis and apoptosis has both theoretical and practical significance with direct implications for the pharmaceutical industry.

A developmentally controlled cellular decompartmentalization process executes programmed cell death in the Arabidopsis root cap.

Programmed cell death (PCD) is a fundamental cellular process crucial to development, homeostasis, and immunity in multicellular eukaryotes. In contrast to our knowledge on the regulation of diverse animal cell death subroutines, information on execution of PCD in plants remains fragmentary. Here, we make use of the accessibility of the Arabidopsis (Arabidopsis thaliana) root cap to visualize the execution process of developmentally controlled PCD. We identify a succession of selective decompartmentalization events and ion fluxes as part of the terminal differentiation program that is orchestrated by the NO APICAL MERISTEM, ARABIDOPSIS THALIANA ACTIVATING FACTOR, CUP-SHAPED COTYLEDON (NAC) transcription factor SOMBRERO. Surprisingly, the breakdown of the large central vacuole is a relatively late and variable event, preceded by an increase of intracellular calcium levels and acidification, release of mitochondrial matrix proteins, leakage of nuclear and endoplasmic reticulum lumina, and release of fluorescent membrane reporters into the cytosol. In analogy to animal apoptosis, the plasma membrane remains impermeable for proteins during and after PCD execution. Elevated intracellular calcium levels and acidification are sufficient to trigger cell death execution specifically in terminally differentiated root cap cells, suggesting that these ion fluxes act as PCD-triggering signals. This detailed information on the cellular processes occurring during developmental PCD in plants is a pivotal prerequisite for future research into the molecular mechanisms of cell death execution.

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

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

Death-seq identifies regulators of cell death and senolytic therapies

Selectively ablating damaged cells is an evolving therapeutic approach for age-related disease. Current methods for genome-wide screens to identify genes whose deletion might promote the death of damaged or senescent cells are generally underpowered because of the short timescales of cell death as well as the difficulty of scaling non-dividing cells. Here, we establish "Death-seq," a positive-selection CRISPR screen optimized to identify enhancers and mechanisms of cell death. Our screens identified synergistic enhancers of cell death induced by the known senolytic ABT-263. The screen also identified inducers of cell death and senescent cell clearance in models of age-related diseases by a related compound, ABT-199, which alone is not senolytic but exhibits less toxicity than ABT-263. Death-seq enables the systematic screening of cell death pathways to uncover molecular mechanisms of regulated cell death subroutines and identifies drug targets for the treatment of diverse pathological states such as senescence, cancer, and fibrosis.

Regulated cell death in cancer: from pathogenesis to treatment.

Regulated cell death (RCD), including apoptosis, pyroptosis, necroptosis, and ferroptosis, is regulated by a series of evolutionarily conserved pathways, and is required for development and tissue homeostasis. Based on previous genetic and biochemical explorations of cell death subroutines, the characteristics of each are generally considered distinctive. However, recent in-depth studies noted the presence of crosstalk between the different forms of RCD; hence, the concept of PANoptosis appeared. Cancer, a complex genetic disease, is characterized by stepwise deregulation of cell apoptosis and proliferation, with significant morbidity and mortality globally. At present, studies on the different RCD pathways, as well as the intricate relationships between different cell death subroutines, mainly focus on infectious diseases, and their roles in cancer remain unclear. As cancers are characterized by dysregulated cell death and inflammatory responses, most current treatment strategies aim to selectively induce cell death via different RCD pathways in cancer cells. In this review, we describe five types of RCD pathways in detail with respect to tumorigenesis and cancer progression. The potential value of some of these key effector molecules in tumor diagnosis and therapeutic response has also been raised. We then review and highlight recent progress in cancer treatment based on PANoptosis and ferroptosis induced by small-molecule compounds, immune checkpoint inhibitors, and nanoparticles. Together, these findings may provide meaningful evidence to fill in the gaps between cancer pathogenesis and RCD pathways to develop better cancer therapeutic strategies.

PANoptosis: new insights in regulated cell death in ischemia/reperfusion models.

PANoptosis: new insights in regulated cell death in ischemia/reperfusion models.

Aggregation-Induced Emission Luminogens for Cell Death Research.

Cell death is closely related to various diseases, and monitoring and controlling cell death is a promising strategy to develop efficient therapy. Aggregation-induced emission luminogens (AIEgens) are ideal candidates for developing novel theranostic agents because of their intriguing properties in the aggregate state. The rational application of AIE materials in cell death-related research is still in its infancy but has shown great clinical potential. This review discussed the research frontier and our understanding of AIE materials in various subroutines of cell death, including apoptosis, necrosis, immunogenic cell death, pyroptosis, autophagy, lysosome-dependent cell death, and ferroptosis. We hope that the new insights can be offered to this growing field and attract more researchers to provide valuable contributions.

Детекция окислительного стресса в артериальных эндотелиальных клетках человека при воздействии кальций-фосфатных бионов

Введение. Кальций-фосфатные бионы (КФБ) формируются в организме человека при перенасыщении сыворотки ионами кальция и фосфора и вызывают дисфункцию эндотелия, однако молекулярные механизмы нарушения функционирования эндотелия при воздействии КФБ не ясны. Цель исследования - выяснение роли кальций-фосфатных бионов различной формы в развитии окислительного стресса в артериальных эндотелиальных клетках (ЭК) человека. Методика. Для детекции окислительного стресса к конфлюэнтным культурам первичных ЭК коронарной и внутренней грудной артерии человека добавляли равные концентрации КФБ сферической или игольчатой формы (СКФБ и ИКФБ соответственно) с последующим культивированием в течение 1 и 4 ч, добавлением флюоресцентных индикаторов окислительного стресса MitoSOX Red и CellROX Green и конфокальной микроскопией. Измеряли концентрацию продуктов перекисного окисления липидов в культуральной жидкости через 24 ч экспозиции эндотелиальных клеток КФБ. Анализ нейтрализации цитотоксических эффектов перекисного окисления липидов проводили путем добавления к ЭК супероксиддисмутазы и каталазы на 4 или 24 ч (одновременно с КФБ). Для сравнения механизмов клеточной гибели при воздействии СКФБ и ИКФБ анализировали цитотоксичность обоих типов бионов при одновременном воздействии лизосомального ингибитора бафиломицина А1. Результаты. Значимого увеличения генерации активных форм кислорода (АФК) в результате экспозиции СКФБ (независимо от линии ЭК и продолжительности экспозиции) не было выявлено. В то же время наблюдалось повышение генерации супероксида через 4 ч, а иных свободных радикалов через 1 ч после добавления ИКФБ к ЭК. Предварительная нейтрализация АФК супероксиддисмутазой и каталазой частично защищала ЭК от индуцируемой ИКФБ гибели. При этом добавление бафиломицина А1 к ЭК частично защищало их от гибели только при воздействии СКФБ, но не ИКФБ. Заключение. Гибель ЭК при воздействии СКФБ происходит в результате первичного повреждения лизосом, а при воздействии ИКФБ - в первую очередь вследствие окислительного стресса. Background. Calcium phosphate bions (CPB) form in the human blood upon its supersaturation with calcium and phosphate and provoke endothelial dysfunction; however, the molecular mechanisms of these pathological processes remain unclear. Aim. To elucidate the role of differently shaped CPBs in induction of oxidative stress in human arterial endothelial cells (Ecs). Methods. For detection of oxidative stress, equal concentrations of spherical CPB (CPB-S) or needle-shaped CPB (CPB-N) were added to confluent cultures of primary human coronary artery and internal thoracic artery ECs for 1 and 4 h; this was followed by MitoSOX Red and CellROX Green staining and subsequent confocal microscopy. Concentration of thiobarbituric acid-reactive substances was measured in the EC culture supernatant at 24 h of the CPB exposure. The lipid peroxidation cytotoxicity was neutralized by adding superoxide dismutase and catalase to ECs for 4 or 24 h. To compare cell death subroutines induced by CPB-S and CPB-N, the effect of bafilomycin A1, a lysosomal inhibitor, on CRB cytotoxicity was studied. Results. No increase in reactive oxygen species generation was observed in the CPB-S exposure, regardless of the EC line and exposure duration. However, addition of CPB-N to ECs increased the production of superoxide and other free radicals after four- and one-hour exposure, respectively. Prior neutralization of reactive oxygen species with superoxide dismutase and catalase partially protected ECs from CPB-N- but not CPB-S-induced death while bafilomycin A1, vice versa, protected ECs from CPB-S- but not CPB-N-induced death. Conclusion. CPB-S cause cell death due to primary damage of lysosomes whereas CPB-N induce apoptosis due to oxidative stress.

Cell Death in Liver Diseases: A Review.

Regulated cell death (RCD) is pivotal in directing the severity and outcome of liver injury. Hepatocyte cell death is a critical event in the progression of liver disease due to resultant inflammation leading to fibrosis. Apoptosis, necrosis, necroptosis, autophagy, and recently, pyroptosis and ferroptosis, have all been investigated in the pathogenesis of various liver diseases. These cell death subroutines display distinct features, while sharing many similar characteristics with considerable overlap and crosstalk. Multiple types of cell death modes can likely coexist, and the death of different liver cell populations may contribute to liver injury in each type of disease. This review addresses the known signaling cascades in each cell death pathway and its implications in liver disease. In this review, we describe the common findings in each disease model, as well as the controversies and the limitations of current data with a particular focus on cell death-related research in humans and in rodent models of alcoholic liver disease, non-alcoholic fatty liver disease and steatohepatitis (NASH/NAFLD), acetaminophen (APAP)-induced hepatotoxicity, autoimmune hepatitis, cholestatic liver disease, and viral hepatitis.

The Quantitative-Phase Dynamics of Apoptosis and Lytic Cell Death

Cell viability and cytotoxicity assays are highly important for drug screening and cytotoxicity tests of antineoplastic or other therapeutic drugs. Even though biochemical-based tests are very helpful to obtain preliminary preview, their results should be confirmed by methods based on direct cell death assessment. In this study, time-dependent changes in quantitative phase-based parameters during cell death were determined and methodology useable for rapid and label-free assessment of direct cell death was introduced. The goal of our study was distinction between apoptosis and primary lytic cell death based on morphologic features. We have distinguished the lytic and non-lytic type of cell death according to their end-point features (Dance of Death typical for apoptosis versus swelling and membrane rupture typical for all kinds of necrosis common for necroptosis, pyroptosis, ferroptosis and accidental cell death). Our method utilizes Quantitative Phase Imaging (QPI) which enables the time-lapse observation of subtle changes in cell mass distribution. According to our results, morphological and dynamical features extracted from QPI micrographs are suitable for cell death detection (76% accuracy in comparison with manual annotation). Furthermore, based on QPI data alone and machine learning, we were able to classify typical dynamical changes of cell morphology during both caspase 3,7-dependent and -independent cell death subroutines. The main parameters used for label-free detection of these cell death modalities were cell density (pg/pixel) and average intensity change of cell pixels further designated as Cell Dynamic Score (CDS). To the best of our knowledge, this is the first study introducing CDS and cell density as a parameter typical for individual cell death subroutines with prediction accuracy 75.4% for caspase 3,7-dependent and -independent cell death.

The impact of endothelial cell death in the brain and its role after stroke: A systematic review

The supply of oxygen and nutrients to the brain is vital for its function and requires a complex vascular network that, when disturbed, results in profound neurological dysfunction. As part of the pathology in stroke, endothelial cells die. As endothelial cell death affects the surrounding cellular environment and is a potential target for the treatment and prevention of neurological disorders, we have systematically reviewed important aspects of endothelial cell death with a particular focus on stroke. After screening 2876 publications published between January 1, 2010 and August 7, 2019, we identified 154 records to be included. We found that endothelial cell death occurs rapidly as well as later after the onset of stroke conditions. Among the different cell death mechanisms, apoptosis was the most widely investigated (92 records), followed by autophagy (20 records), while other, more recently defined mechanisms received less attention, such as lysosome-dependent cell death (2 records) and necroptosis (2 records). We also discuss the differential vulnerability of brain cells to injury after stroke and the role of endothelial cell death in the no-reflow phenomenon with a special focus on the microvasculature. Further investigation of the different cell death mechanisms using novel tools and biomarkers will greatly enhance our understanding of endothelial cell death. For this task, at least two markers/criteria are desirable to determine cell death subroutines according to the recommendations of the Nomenclature Committee on Cell Death.

Necrosome Formation and Necroptosis in Experimental Cholestasis.

Necroptosis is emerging as a critical pathogenic mechanism in several liver diseases, including cholestatic disorders. Necroptosis was recently described as a novel cell death subroutine, activated downstream of death receptor stimulation and dependent on receptor-interacting serine/threonine-protein kinase 3 activity and mixed lineage kinase domain-like oligomerization and translocation to cell membrane. Here, we describe a combination of methods to evaluate necroptosis triggering in in vitro and in vivo models of cholestasis. Particularly, we detail alternative protocols to isolate total and soluble/insoluble protein extracts from tissues and cell cultures, as well as in vitro receptor-interacting serine/threonine-protein kinase 3 kinase activity assays, and subsequent Western blot analysis.

Cell death in drug-induced liver injury.

Drug-induced liver injury (DILI) is an important cause of liver toxicity which can have varying clinical presentations, the most severe of which being acute liver failure. Hepatocyte death as a cause of drug toxicity is a feature of DILI. There are multiple cell death subroutines; some, like apoptosis, necroptosis, autophagy, and necrosis have been extensively studied, while others such as pyroptosis and ferroptosis have been more recently described. The mode of cell death in DILI depends on the culprit drug, as it largely dictates the mechanism and extent of injury. The main cell death subroutines in DILI are apoptosis and necrosis, with mitochondrial involvement being pivotal for the execution of both. A few drugs such as acetaminophen (APAP) can cause direct, dose-dependent toxicity, while the majority of drugs cause idiosyncratic DILI (IDILI). IDILI is an unpredictable form of liver injury that is not dose dependent, occurs in individuals with a genetic predisposition, and presents with variable latency. APAP-induced programmed necrosis has been extensively studied. However, the mechanisms and pathogenesis of cell death from drugs causing IDILI are harder to elucidate due to the complex and multifactorial nature of the disease. Cell death in IDILI is likely death receptor-mediated apoptosis and the result of an activated innate and adaptive immune system, compounded by other host factors such as genetics, gender, age, and capacity for immune tolerance. This chapter will review the different modes of cell death, namely apoptosis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis and their pertinence to DILI.

Characterization of a Mouse Model of Hypereosinophilic Syndrome

Introduction: Hypereosinophilic syndrome is characterized by sustained blood and/or tissue hypereosinophilia leading to tissue damage and organ dysfunction. Nearly half the cases are classified as idiopathic, since no known cause is identified and there is no evidence of a clonal disorder. In such cases, nonspecific treatment approaches, including corticosteroids, hydroxyurea and interferon-alpha, are used aimed at mitigating eosinophil-mediated organ damage. However, mortality occurs primarily due to cardiac and thromboembolic complications. Understanding the cause and mechanism of disease would aid in the development of targeted therapies with greater efficacy and fewer side effects. For instance, while the traditional view is that eosinophils are detrimental via toxicity of their granule proteins, recent studies suggest other mechanisms including non-canonical cell death subroutines, such as regulated necrosis, release of pro-thrombotic DNA “traps” and others. Lack of a mouse model hinders testing such hypotheses in vivo. We have developed a mouse model of eosinophil-associated hypereosinophilic syndrome characterized by multi-organ involvement including lethal prothrombotic myocardial damage.Results: We discovered a spontaneous mouse mutant in our colony with a hypereosinophilic phenotype. Mice develop peripheral blood eosinophilia, infiltration of lungs, spleen and heart by eosinophils, and extensive myocardial damage and remodeling. This ultimately leads to heart failure and premature death, often by 14 weeks of age. Histopathologic assessment of the hearts from affected mice (Fig. 1) revealed a robust inflammatory infiltrate of the ventricular myocardium. Immunohistochemistry demonstrated that this infiltrate is composed primarily of eosinophils (MBP) and B lymphocytes (B220), leading to myocardial damage and replacement fibrosis. In some cases, hearts showed dilatation and thinning of the right ventricular wall, suggestive of an inflammatory dilated cardiomyopathy. An exam of most mice revealed primarily atrial thrombi, which often filled the entire/majority of the chamber. Expression analysis by protein multiplex assay in heart homogenates revealed overexpression of Th1 and Th2 cytokines and chemokines, including IL-4, IL-6, LIF, IL-16, IP-10/Cxcl10, MIG/Cxcl9, Eotaxin-1/Ccl11, RANTES/Ccl5, MIP-1β/Ccl4, MIP-3β/Ccl19, MCP-1/Ccl2, MCP-3/Ccl7, MDC/Ccl22 and TARC/Ccl17.Conclusion: The pathologies observed in the mutant line are reminiscent of those seen in patients with hypereosinophilia, where cardiac-related morbidities, like congestive heart failure and thrombi, are the most common causes of death. As such, our model provides an opportunity to test mechanistic hypotheses and develop targeted therapies. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Methods for Assessing Apoptosis and Anoikis in Normal Intestine/Colon and Colorectal Cancer.

Caspase-dependent apoptosis, including its distinct cell death subroutine known as anoikis, perform essential roles during organogenesis, as well as in the maintenance and repair of tissues. To this effect, the continuous renewal of the human intestinal/colon epithelium is characterized by the exfoliation by anoikis of differentiated cells, whereas immature/undifferentiated cells may occasionally undergo apoptosis in order to evacuate daughter cells that are damaged or defective. Dysregulated epithelial apoptosis is a significant component of inflammatory bowel diseases. Conversely, the acquisition of a resistance to apoptosis represents one of the hallmarks of cancer initiation and progression, including for colorectal cancer (CRC). Furthermore, the emergence of anoikis resistance constitutes a critical step in cancer progression (including CRC), as well as a limiting one that enables invasion and metastasis.Considering the implications of apoptosis/anoikis dysregulation in gut physiopathology, it therefore becomes incumbent to understand the functional determinants that underlie such dysregulation-all the while having to monitor, assess, or evidence apoptosis and/or anoikis. In this chapter, methodologies that are typically used to assess caspase-dependent apoptosis and anoikis in intestinal/colonic normal and CRC cells, whether in vivo, ex vivo, or in cellulo, are provided.

GPx4, Lipid Peroxidation, and Cell Death: Discoveries, Rediscoveries, and Open Issues.

Iron-dependent lipid peroxidation is a complex oxidative process where phospholipid hydroperoxides (PLOOH) are produced in membranes and finally transformed into a series of decomposition products, some of which are endowed with biological activity. It is specifically prevented by glutathione peroxidase 4 (GPx4), the selenoenzyme that reduces PLOOH by glutathione (GSH). PLOOH is both a product and the major initiator of peroxidative chain reactions, as well as an activator of lipoxygenases. α-Tocopherol both specifically breaks peroxidative chain propagation and inhibits lipoxygenases. Thus, GPx4, GSH, and α-tocopherol are integrated in a concerted anti-peroxidant mechanism. Recent Advances: Ferroptosis has been recently identified as a cell death subroutine that is specifically activated by missing GPx4 activity and inhibited by iron chelation or α-tocopherol supplementation. Ferroptosis induction may underlie spontaneous human diseases, such as major neurodegeneration and neuroinflammation, causing an excessive cell death. The basic mechanism of ferroptosis, therefore, fits the features of activation of lipid peroxidation. Still lacking are convincing proofs that lipoxygenases are involved in ferroptosis. Also, unknown are the molecules eventually killing cells and the mechanisms underlying the drop of the cellular anti-peroxidant capacity. Molecular events and mechanisms of ferroptosis to be unraveled and validated on animal models are GPx4 inactivation, role of GSH concentration, increased iron availability, and membrane structure and composition. This is expected to drive drug discovery that is aimed at halting cell death in degenerative diseases or boosting it in cancer cells. Antioxid. Redox Signal. 29, 61-74.

Drug-Induced Liver Injury: Cascade of Events Leading to Cell Death, Apoptosis or Necrosis.

Drug-induced liver injury (DILI) can broadly be divided into predictable and dose dependent such as acetaminophen (APAP) and unpredictable or idiosyncratic DILI (IDILI). Liver injury from drug hepatotoxicity (whether idiosyncratic or predictable) results in hepatocyte cell death and inflammation. The cascade of events leading to DILI and the cell death subroutine (apoptosis or necrosis) of the cell depend largely on the culprit drug. Direct toxins to hepatocytes likely induce oxidative organelle stress (such as endoplasmic reticulum (ER) and mitochondrial stress) leading to necrosis or apoptosis, while cell death in idiosyncratic DILI (IDILI) is usually the result of engagement of the innate and adaptive immune system (likely apoptotic), involving death receptors (DR). Here, we review the hepatocyte cell death pathways both in direct hepatotoxicity such as in APAP DILI as well as in IDILI. We examine the known signaling pathways in APAP toxicity, a model of necrotic liver cell death. We also explore what is known about the genetic basis of IDILI and the molecular pathways leading to immune activation and how these events can trigger hepatotoxicity and cell death.

Targeting Programmed Cell Death Using Small‐Molecule Compounds to Improve Potential Cancer Therapy

Evasion of cell death is one of the hallmarks of cancer cells, beginning with long-established apoptosis and extending to other new forms of cell death. An elaboration of cell death pathways thus will contribute to a better understanding of cancer pathogenesis and therapeutics. With the recent substantial biochemical and genetic explorations of cell death subroutines, their classification has switched from primarily morphological to more molecular definitions. According to their measurable biochemical features and intricate mechanisms, cell death subroutines can be divided into apoptosis, autophagic cell death, mitotic catastrophe, necroptosis, parthanatos, ferroptosis, pyroptosis, pyronecrosis, anoikis, cornification, entosis, and NETosis. Supportive evidence has gradually revealed the prime molecular mechanisms of each subroutine and thus providing series of possible targets in cancer therapy, while the intricate relationships between different cell death subroutines still remain to be clarified. Over the past decades, cancer drug discovery has significantly benefited from the use of small-molecule compounds to target classical modalities of cell death such as apoptosis, while newly identified cell death subroutines has also emerging their potential for cancer drug discovery in recent years. In this review, we comprehensively focus on summarizing 12 cell death subroutines and discussing their corresponding small-molecule compounds in potential cancer therapy. Together, these inspiring findings may provide more evidence to fill in the gaps between cell death subroutines and small-molecule compounds to better develop novel cancer therapeutic strategies.

Macromitophagy, neutral lipids synthesis, and peroxisomal fatty acid oxidation protect yeast from “liponecrosis”, a previously unknown form of programmed cell death

We identified a form of cell death called “liponecrosis.” It can be elicited by an exposure of the yeast Saccharomyces cerevisiae to exogenous palmitoleic acid (POA). Our data imply that liponecrosis is: (1) a programmed, regulated form of cell death rather than an accidental, unregulated cellular process and (2) an age-related form of cell death. Cells committed to liponecrotic death: (1) do not exhibit features characteristic of apoptotic cell death; (2) do not display plasma membrane rupture, a hallmark of programmed necrotic cell death; (3) akin to cells committed to necrotic cell death, exhibit an increased permeability of the plasma membrane for propidium iodide; (4) do not display excessive cytoplasmic vacuolization, a hallmark of autophagic cell death; (5) akin to cells committed to autophagic death, exhibit a non-selective en masse degradation of cellular organelles and require the cytosolic serine/threonine protein kinase Atg1p for executing the death program; and (6) display a hallmark feature that has not been reported for any of the currently known cell death modalities—namely, an excessive accumulation of lipid droplets where non-esterified fatty acids (including POA) are deposited in the form of neutral lipids. We therefore concluded that liponecrotic cell death subroutine differs from the currently known subroutines of programmed cell death. Our data suggest a hypothesis that liponecrosis is a cell death module dynamically integrated into a so-called programmed cell death network, which also includes the apoptotic, necrotic, and autophagic modules of programmed cell death. Based on our findings, we propose a mechanism underlying liponecrosis.

Cancer immunogenicity, danger signals, and DAMPs: What, when, and how?

Cancer immunosurvelliance usually leads to formation of cancer cells that have been "immunoedited" to resist anti-tumor immunity. One of the consequences of immunoediting that is, reduced immunogenicity, is an important roadblock in revival of stable and long-lasting anti-tumor immune responses. Research done during the last decade has shown that emission by the dying cancer cells of immunomodulatory factors or damage-associated molecular patterns (DAMPs), which can act as danger signals, is a critical event in accentuating the immunogenicity of cancer cells, in response to a subset of anticancer treatments. Recent evidence has defined that an apoptotic cell death subroutine and its underlying biochemistry, which has been termed as "immunogenic cell death (ICD)" or "immunogenic apoptosis," is required for the efficient emission of DAMPs and inciting anti-tumor immunity. Here, we review the basic concepts of ICD, like cancer immunogenicity, danger signals, and DAMPs. Moreover, we discuss the emerging molecular links between endoplasmic reticulum (ER) stress, induction of a viral response-like gene expression, danger signals, and anti-tumor immunity. We envisage that along with ER stress-based trafficking of DAMPs (which is a "short-range communicator" of danger), the accompanying induction of a viral response-like gene expression and the secretion of anti-tumorigenic cytokines may become a crucial signature of ICD induction by anticancer therapy.