Mechanisms and consequences of entosis

Molecular mechanisms of tetrabromobisphenol A (TBBPA) toxicity: Insights from various biological systems

Tetrabromobisphenol A (TBBPA) is a ubiquitous brominated flame retardant extensively incorporated into a wide range of products. As its utilization has escalated, its environmental exposure risks have concomitantly increased. The molecular properties of TBBPA allow it to persist in the environment and within organisms. In this review, we comprehensively examine the toxicity of TBBPA across different organ systems and elucidate the underlying molecular mechanisms. We particularly emphasize TBBPA's impact on biological signaling pathways, protein functionality, cellular architecture, and epigenetic regulation, which collectively lead to disruptions in endocrine, hepatic, neurological, reproductive, and other biological systems. The analysis of these toxicological phenomena and their fundamental molecular mechanisms has substantially enhanced our understanding of TBBPA's hazardous characteristics. This review also examines potential avenues for future research, with a focus on uncovering novel molecular mechanisms and assessing the toxicological impacts of TBBPA exposure, particularly in relation to interactions with other environmental contaminants. We propose a greater focus on examining the toxic effects and molecular mechanisms of long-term TBBPA exposure at environmentally relevant concentrations to facilitate more accurate assessments of human health risks.

Navigating the complexities of cell death: Insights into accidental and programmed cell death

Cell death is a critical biological phenomenon that can be categorized into accidental cell death (ACD) and programmed cell death (PCD), each exhibiting distinct signaling, mechanistic and morphological characteristics. This paper provides a comprehensive overview of seven types of ACD, including coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous and secondary necrosis, discussing their pathological implications in conditions such as ischemia and inflammation. Additionally, we review eighteen forms of PCD, encompassing autophagy, apoptosis, necroptosis, pyroptosis, paraptosis, ferroptosis, anoikis, entosis, NETosis, eryptosis, parthanatos, mitoptosis, and newly recognized types such as methuosis, autosis, alkaliptosis, oxeiptosis, cuprotosis and erebosis. The implications of these cell death modalities for cellular processes, development, and disease-particularly in the context of neoplastic and neurodegenerative disorders-are also covered. Furthermore, we explore the crosstalk between various forms of PCD, emphasizing how apoptotic mechanisms can influence pathways like necroptosis and pyroptosis. Understanding this interplay is crucial for elucidating cellular responses to stress, as well as for its potential relevance in clinical applications and therapeutic strategies. Future research should focus on clarifying the molecular mechanisms that govern different forms of PCD and their interactions.

Sphingolipid metabolism and regulated cell death in malignant melanoma

Malignant melanoma (MM) is a highly invasive and therapeutically resistant skin malignancy, posing a significant clinical challenge in its treatment. Programmed cell death plays a crucial role in the occurrence and progression of MM. Sphingolipids (SP), as a class of bioactive lipids, may be associated with many kinds of diseases. SPs regulate various forms of programmed cell death in tumors, including apoptosis, necroptosis, ferroptosis, and more. This review will delve into the mechanisms by which different types of SPs modulate various forms of programmed cell death in MM, such as their regulation of cell membrane permeability and signaling pathways, and how they influence the survival and death fate of MM cells. An in-depth exploration of the role of SPs in programmed cell death in MM aids in unraveling the molecular mechanisms of melanoma development and holds significant importance in developing novel therapeutic strategies.

A bibliometric and visualization analysis of entosis research from 2007 to 2024

Objective

In 2007, entosis was proposed as a form of programmed cell death, distinct from apoptosis. This process involves a living cell (internalized cell) actively invading a neighboring live cell of the same type (host cell), forming a cell-in-cell structure. Recently, entosis has been increasingly associated with cancer, leading to significant advancements in research. Despite this progress, a comprehensive and unbiased review of the current state of entosis research is lacking. This study aims to evaluate the developments in the field of entosis over the past decade and highlight emerging research trends.

Materials and methods

We performed a literature search for studies published since the introduction of the entosis concept, using the Web of Science Core Collection database. The bibliometric analysis was conducted using VOSviewer, CiteSpace, Microsoft Excel, and the Bibliometrix R package.

Results

A total of 196 articles from 39 countries and 346 institutions were included. Between 2007 and 2024, research on entosis has seen rapid growth, with most publications originating from China and the United States. The United States also leads in total citations, with Memorial Sloan Kettering Cancer Center emerging as the top research institution. Sun Qiang is the most prolific author in this field, while Overholtzer M has the highest number of citations. Current Molecular Medicine has published the most articles related to entosis. Frequently occurring keywords include "entosis," "cannibalism," "autophagy," and "apoptosis." In recent years, keywords such as "phagocytosis," "drug resistance," and "human cancers" have surged, indicating a growing focus on understanding the role of entosis in tumor progression and exploring its potential as a therapeutic target for cancer treatment.

Conclusions

This study provides the first bibliometric analysis of entosis, detailing its evolution over the last decade. It highlights critical areas of interest, including the development of inhibitors targeting entosis and their potential clinical applications. This research aims to guide future investigations and serve as a valuable resource for scholars exploring entosis in cancer biology.

LC3-associated phagocytosis of neutrophils triggers tumor ferroptotic cell death in glioblastoma

Necrosis in solid tumors is commonly associated with poor prognostic but how these lesions expand remains unclear. Studies have found that neutrophils associate with and contribute to necrosis development in glioblastoma by inducing tumor cell ferroptosis through transferring myeloperoxidase-containing granules. However, the mechanism of neutrophilic granule transfer remains elusive. We performed an unbiased small molecule screen and found that statins inhibit neutrophil-induced tumor cell death by blocking the neutrophilic granule transfer. Further, we identified a novel process wherein neutrophils are engulfed by tumor cells before releasing myeloperoxidase-containing contents into tumor cells. This neutrophil engulfment is initiated by integrin-mediated adhesion, and further mediated by LC3-associated phagocytosis (LAP), which can be blocked by inhibiting the Vps34-UVRAG-RUBCN-containing PI3K complex. Myeloperoxidase inhibition or Vps34 depletion resulted in reduced necrosis formation and prolonged mouse survival in an orthotopic glioblastoma mouse model. Thus, our study unveils a critical role for LAP-mediated neutrophil internalization in facilitating the transfer of neutrophilic granules, which in turn triggers tumor cell death and necrosis expansion. Targeting this process holds promise for improving glioblastoma prognosis.

Research progress on morphology and mechanism of programmed cell death

Programmed cell death (PCD) is a basic process of life that is closely related to the growth, development, aging and disease of organisms and is one of the hotspots of life science research today. PCD is a kind of genetic control, autonomous and orderly important cell death that involves the activation, expression, and regulation of a series of genes. In recent years, with the deepening of research in this field, new mechanisms of multiple PCD pathways have been revealed. This article reviews and summarizes the multiple PCD pathways that have been discovered, analyses and compares the morphological characteristics and biomarkers of different types of PCD, and briefly discusses the role of various types of PCD in the diagnosis and treatment of different diseases, especially malignant tumors.

Non-apoptotic regulated cell death mediates reprogramming of the tumour immune microenvironment by macrophages

Tumour immune microenvironment (TIME) plays an indispensable role in tumour progression, and tumour-associated macrophages (TAMs) are the most abundant immune cells in TIME. Non-apoptotic regulated cell death (RCD) can avoid the influence of tumour apoptosis resistance on anti-tumour immune response. Specifically, autophagy, ferroptosis, pyroptosis and necroptosis mediate the crosstalk between TAMs and tumour cells in TIME, thus reprogram TIME and affect the progress of tumour. In addition, although some achievements have been made in immune checkpoint inhibitors (ICIs), there is still defect that ICIs are only effective for some people because non-apoptotic RCD can bypass the apoptosis resistance of tumour. As a result, ICIs combined with targeting non-apoptotic RCD may be a promising solution. In this paper, the basic molecular mechanism of non-apoptotic RCD, the way in which non-apoptotic RCD mediates crosstalk between TAMs and tumour cells to reprogram TIME, and the latest research progress in targeting non-apoptotic RCD and ICIs are reviewed.

The Emerging Role of Deubiquitinases in Radiosensitivity

Radiation therapy is a primary treatment for cancer, but radioresistance remains a significant challenge in improving efficacy and reducing toxicity. Accumulating evidence suggests that deubiquitinases (DUBs) play a crucial role in regulating cell sensitivity to ionizing radiation. Traditional small-molecule DUB inhibitors have demonstrated radiosensitization effects, and novel deubiquitinase-targeting chimeras (DUBTACs) provide a promising strategy for radiosensitizer development by harnessing the ubiquitin-proteasome system. This review highlights the mechanisms by which DUBs regulate radiosensitivity, including DNA damage repair, the cell cycle, cell death, and hypoxia. Progress on DUB inhibitors and DUBTACs is summarized, and their potential radiosensitization effects are discussed. Developing drugs targeting DUBs appears to be a promising alternative approach to overcoming radioresistance, warranting further research into their mechanisms.

Entosis: the core mechanism and crosstalk with other cell death programs

Cell death pathways play critical roles in organism development and homeostasis as well as in the pathogenesis of various diseases. While studies over the last decade have elucidated numerous different forms of cell death that can eliminate cells in various contexts, how certain mechanisms impact physiology is still not well understood. Moreover, recent studies have shown that multiple forms cell death can occur in a cell population, with different forms of death eliminating individual cells. Here, we aim to describe the known molecular mechanisms of entosis, a non-apoptotic cell engulfment process, and discuss signaling mechanisms that control its induction as well as its possible crosstalk with other cell death mechanisms.

Exploring diverse programmed cell-death patterns to develop a novel gene signature for predicting the prognosis of lung adenocarcinoma patients

Background

Programmed cell death (PCD) plays a critical role in tumor progression and malignancy, and exploring its relationship with lung adenocarcinoma (LUAD)'s survival outcomes is important for personalized diagnosis and treatment. This study aimed to identify survival-related genes and construct an effective prognostic indicator for LUAD based on 12 forms of PCD.

Methods

A total of 1,933 candidate genes related to PCD were collected from published studies and public data center. A prognostic gene signature, called the cell death index (CDI), was established based on RNA-Seq and immunohistochemistry (IHC). IHC staining on tissue microarray was applied for the validation of protein level. Moreover, GSE42127, GSE72094 were used as validation datasets.

Results

The CDI based on expression level of nine genes (CCNB2, HMGA1, CACNA2D2, BUB1B, BTG2, KIF14, PTGDS, SERPINB5, BRCA1) was highly predictive for overall survival (OS) of LUAD in our cohort [36-month area under the curve (AUC): 0.750, 60-month AUC: 0.809]. The CDI was further validated in independent cohorts (GSE72094, 36-month AUC: 0.717, 60-month AUC: 0.737; GSE42127, 12-month AUC: 0.829, 60-month AUC: 0.663). And the CDI was found to be an independent prognostic factor after adjusting for other clinical characteristics. Furthermore, the high-CDI group was associated with upregulated tumor immune infiltration compared to the low-CDI group.

Conclusions

This study identified a 9-gene signature (CDI) based on PCD-related genes that accurately predicted the prognosis of LUAD patients. The CDI could serve as a valuable prognostic indicator and guide personalized therapeutic strategies for LUAD.

Loss of RND3/RHOE controls entosis through LAMP1 expression in hepatocellular carcinoma

Entosis is a process that leads to the formation of cell-in-cell structures commonly found in cancers. Here, we identified entosis in hepatocellular carcinoma and the loss of Rnd3 (also known as RhoE) as an efficient inducer of this mechanism. We characterized the different stages and the molecular regulators of entosis induced after Rnd3 silencing. We demonstrated that this process depends on the RhoA/ROCK pathway, but not on E-cadherin. The proteomic profiling of entotic cells allowed us to identify LAMP1 as a protein upregulated by Rnd3 silencing and implicated not only in the degradation final stage of entosis, but also in the full mechanism. Moreover, we found a positive correlation between the presence of entotic cells and the metastatic potential of tumors in human patient samples. Altogether, these data suggest the involvement of entosis in liver tumor progression and highlight a new perspective for entosis analysis in medicine research as a novel therapeutic target.

Cell death classification: A new insight based on molecular mechanisms

Cells tend to disintegrate themselves or are forced to undergo such destructive processes in critical circumstances. This complex cellular function necessitates various mechanisms and molecular pathways in order to be executed. The very nature of cell death is essentially important and vital for maintaining homeostasis, thus any type of disturbing occurrence might lead to different sorts of diseases and dysfunctions. Cell death has various modalities and yet, every now and then, a new type of this elegant procedure gets to be discovered. The diversity of cell death compels the need for a universal organizing system in order to facilitate further studies, therapeutic strategies and the invention of new methods of research. Considering all that, we attempted to review most of the known cell death mechanisms and sort them all into one arranging system that operates under a simple but subtle decision-making (If \ Else) order as a sorting algorithm, in which it decides to place and sort an input data (a type of cell death) into its proper set, then a subset and finally a group of cell death. By proposing this algorithm, the authors hope it may solve the problems regarding newer and/or undiscovered types of cell death and facilitate research and therapeutic applications of cell death.

Types of Cell Death from a Molecular Perspective

The former conventional belief was that cell death resulted from either apoptosis or necrosis; however, in recent years, different pathways through which a cell can undergo cell death have been discovered. Various types of cell death are distinguished by specific morphological alterations in the cell's structure, coupled with numerous biological activation processes. Various diseases, such as cancers, can occur due to the accumulation of damaged cells in the body caused by the dysregulation and failure of cell death. Thus, comprehending these cell death pathways is crucial for formulating effective therapeutic strategies. We focused on providing a comprehensive overview of the existing literature pertaining to various forms of cell death, encompassing apoptosis, anoikis, pyroptosis, NETosis, ferroptosis, autophagy, entosis, methuosis, paraptosis, mitoptosis, parthanatos, necroptosis, and necrosis.

Identification of hub gene and lncRNA signature related to entotic cell death in cutaneous melanoma for prognostic and immune prediction

Entotic cell death (ECD), a cell death program observed in cancer cell competition, predominantly occurs in an autophagy protein-dependent, non-apoptotic manner. However, the relationship between cutaneous melanoma (CM) and ECD-associated genes and lncRNAs has remained unclear. This study aimed to elucidate the role and mechanism of ECD-associated genes in CM. To achieve this, 4 mechanism learning algorithms and integrated bioinformatic analyses were employed to identify the core ECD-associated genes and lncRNAs. Subsequently, 2 risk signatures based on ECD-associated genes and hub lncRNAs were constructed for CM patients. As a result, we observed significant differential expression of ECD-associated genes in CM, indicating their potential as valuable predictors for CM patients. Moreover, RHOA was identified as a core ECD-associated gene in CM, and its expression was found to be associated with patients' survival and immune infiltration, suggesting its relevance as a potential therapeutic target. Additionally, this study provided clarification on hub ECD-associated lncRNAs in CM, offering insights into their roles in the disease. Through bioinformatic analyses, we identified 2 risk signatures based on the expression of ECD-associated genes and hub ECD-associated lncRNAs, respectively. Both risk signatures were strongly linked to the prognosis and cancer growth of CM, underscoring their potential as valuable prognostic indicators. Furthermore, mechanistic analyses suggested a significant association between the risk signature and the immune microenvironment in CM, highlighting potential immune-related implications in disease progression. In conclusion, we propose that ECD-associated genes and lncRNAs hold promise as potential targets in CM. Moreover, our findings revealed a significant correlation between ECD and the immune microenvironment, providing crucial insights for guiding individualized treatment strategies in CM.

Diversity and complexity of cell death: a historical review

Death is the inevitable fate of all living organisms, whether at the individual or cellular level. For a long time, cell death was believed to be an undesirable but unavoidable final outcome of nonfunctioning cells, as inflammation was inevitably triggered in response to damage. However, experimental evidence accumulated over the past few decades has revealed different types of cell death that are genetically programmed to eliminate unnecessary or severely damaged cells that may damage surrounding tissues. Several types of cell death, including apoptosis, necrosis, autophagic cell death, and lysosomal cell death, which are classified as programmed cell death, and pyroptosis, necroptosis, and NETosis, which are classified as inflammatory cell death, have been described over the years. Recently, several novel forms of cell death, namely, mitoptosis, paraptosis, immunogenic cell death, entosis, methuosis, parthanatos, ferroptosis, autosis, alkaliptosis, oxeiptosis, cuproptosis, and erebosis, have been discovered and advanced our understanding of cell death and its complexity. In this review, we provide a historical overview of the discovery and characterization of different forms of cell death and highlight their diversity and complexity. We also briefly discuss the regulatory mechanisms underlying each type of cell death and the implications of cell death in various physiological and pathological contexts. This review provides a comprehensive understanding of different mechanisms of cell death that can be leveraged to develop novel therapeutic strategies for various diseases.

Cell-in-Cell Structures in Gastrointestinal Tumors: Biological Relevance and Clinical Applications

This review summarizes information about cell-in-cell (CIC) structures with a focus on gastrointestinal tumors. The phenomenon when one cell lives in another one has attracted an attention of researchers over the past decades. We briefly discuss types of CIC structures and mechanisms of its formation, as well as the biological basis and consequences of the cell-engulfing process. Numerous clinico-histopathological studies demonstrate the significance of these structures as prognostic factors, mainly correlated with negative prognosis. The presence of CIC structures has been identified in all gastrointestinal tumors. However, the majority of studies concern pancreatic cancer. In this field, in addition to the assessment of the prognostic markers, the attempts to manipulate the ability of cells to form CISs have been done in order to stimulate the death of the inner cell. Number of CIC structures also correlates with genetic features for some gastrointestinal tu-mors. The role of CIC structures in the responses of tumors to therapies, both chemotherapy and immunotherapy, seems to be the most poorly studied. However, there is some evidence of involvement of CIC structures in treatment failure. Here, we summarized the current literature on CIC structures in cancer with a focus on gastrointestinal tumors and specified future perspectives for investigation.

Cell-in-Cell Structures in Gastrointestinal Tumors: Biological Relevance and Clinical Applications

This review summarizes information about cell-in-cell (CIC) structures with a focus on gastrointestinal tumors. The phenomenon when one cell lives in another one has attracted an attention of researchers over the past decades. We briefly discuss types of CIC structures and mechanisms of its formation, as well as the biological basis and consequences of the cell-engulfing process. Numerous clinico-histopathological studies demonstrate the significance of these structures as prognostic factors, mainly correlated with negative prognosis. The presence of CIC structures has been identified in all gastrointestinal tumors. However, the majority of studies concern pancreatic cancer. In this field, in addition to the assessment of the prognostic markers, the attempts to manipulate the ability of cells to form CISs have been done in order to stimulate the death of the inner cell. Number of CIC structures also correlates with genetic features for some gastrointestinal tu-mors. The role of CIC structures in the responses of tumors to therapies, both chemotherapy and immunotherapy, seems to be the most poorly studied. However, there is some evidence of involvement of CIC structures in treatment failure. Here, we summarized the current literature on CIC structures in cancer with a focus on gastrointestinal tumors and specified future perspectives for investigation.

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.

Different Ways to Die: Cell Death Pathways and Their Association With Spinal Cord Injury

Cell death is a systematic/nonsystematic process of cessation of normal morphology and functional properties of the cell to replace and recycle old cells with new also promoting inflammation in some cases. It is a complicated process comprising multiple pathways. Some are well-explored, and others have just begun to be. The research on appropriate control of cell death pathways after acute and chronic damage of neuronal cells is being widely researched today due to the lack of regeneration and recovering potential of a neuronal cell after sustaining damage and the inability to control the direction of neuronal growth. In the progression and onset of various neurological diseases, impairments in programmed cell death signaling processes, like necroptosis, apoptosis, ferroptosis, pyroptosis, and pathways directly or indirectly linked, like autophagy as in nonprogrammed necrosis, are observed. Spinal cord injury (SCI) involves the temporary or permanent disruption of motor activities due to the death of a neuronal and glial cell in the spinal cord accompanied by axonal degeneration. Recent years have seen a significant increase in research on the intricate biochemical interactions that occur after a SCI. Different cell death pathways may significantly impact the subsequent damage processes that lead to the eventual neurological deficiency after an injury to the spinal cord. A better knowledge of the molecular basis of the involved cell death pathways might help enhance neuronal and glial survival and neurological deficits, promoting a curative path for SCI.

Polydopamine conjugated SiO2 nanoparticles as potential drug carriers for melanoma treatment

Silica nanoparticles (SiO₂) are increasingly investigated for biomedical applications. Aim: This study aimed to analyze the potential use of a SiO₂ nanoparticles coated with biocompatible polydopamine (SiO₂@PDA) as a potential chemotherapeutic drug carrier. Materials & methods: SiO₂ morphology and PDA adhesion was analyzed by dynamic light scattering, electron microscopy and nuclear magnetic resonance. Cytotoxicity studies and morphology analyses (immunofluorescence, scanning and transmission electron microscopy) were used to assess the cellular reaction to the SiO₂@PDA nanoparticles and to identify a biocompatible (safe use) window. Results & conclusion: Concentrations above 10 μg/ml and up to 100 μg/ml SiO₂@PDA showed the best biocompatibility on human melanoma cells at 24 h and represent a potential drug carrier template for targeted melanoma cancer treatment.

Orai1 is an Entotic Ca2+ Channel for Non-Apoptotic Cell Death, Entosis in Cancer Development

Entosis is a non-apoptotic cell death process that forms characteristic cell-in-cell structures in cancers, killing invading cells. Intracellular Ca²⁺ dynamics are essential for cellular processes, including actomyosin contractility, migration, and autophagy. However, the significance of Ca²⁺ and Ca²⁺ channels participating in entosis is unclear. Here, it is shown that intracellular Ca²⁺ signaling regulates entosis via SEPTIN-Orai1-Ca²⁺ /CaM-MLCK-actomyosin axis. Intracellular Ca²⁺ oscillations in entotic cells show spatiotemporal variations during engulfment, mediated by Orai1 Ca²⁺ channels in plasma membranes. SEPTIN controlled polarized distribution of Orai1 for local MLCK activation, resulting in MLC phosphorylation and actomyosin contraction, leads to internalization of invasive cells. Ca²⁺ chelators and SEPTIN, Orai1, and MLCK inhibitors suppress entosis. This study identifies potential targets for treating entosis-associated tumors, showing that Orai1 is an entotic Ca²⁺ channel that provides essential Ca²⁺ signaling and sheds light on the molecular mechanism underlying entosis that involves SEPTIN filaments, Orai1, and MLCK.

A reliable elasticity sensing method for analysis of cell entosis using microfluidic cytometer

Cell entosis is a novel cell death process starting from cell-in-cell invasion. In general, cancer cells own higher incidence rate of cell entosis comparing to non-cancerous cells. Studies arguing whether cell entosis is a tumor suppressing process or a tumor accelerating process can deepen our understanding of tumor development. Cell elasticity is recognized as one of tumor malignant biomarkers. There have been some researchers studying cell elasticity in cell entosis. However, existing cell elasticity sensing technique (i.e. micropipette aspiration) can hardly be reliable neither high-throughput. In this work, we introduce an elasticity sensing method for quantifying both cell elasticity in cell-in-cell structures and single floating cells using a microfluidic cytometer. We not only argue our cell elasticity sensing method is reliable for already occurred entosis but also apply such method on predicting the "outer" cells in entosis of different cell types. The elasticity sensing method proposed in this manuscript is able to provide an effective and reliable way to further study deeper mechanism in cell entosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13534-023-00264-0.

An entosis-like process induces mitotic disruption in Pals1 microcephaly pathogenesis

Entosis is cell cannibalism utilized by tumor cells to engulf live neighboring cells for pro- or anti-tumorigenic purposes. It is unknown whether this extraordinary cellular event can be pathogenic in other diseases such as microcephaly, a condition characterized by a smaller than normal brain at birth. We find that mice mutant for the human microcephaly-causing gene Pals1, which exhibit diminished cortices due to massive cell death, also exhibit nuclei enveloped by plasma membranes inside of dividing cells. These cell-in-cell (CIC) structures represent a dynamic process accompanied by lengthened mitosis and cytokinesis abnormalities. As shown in tumor cells, ROCK inhibition completely abrogates CIC structures and restores the normal length of mitosis. Moreover, genetic elimination of Trp53 produces a remarkable rescue of cortical size along with substantial reductions of CIC structures and cell death. These results provide a novel pathogenic mechanism by which microcephaly is produced through entotic cell cannibalism.

The lysophosphatidic acid-regulated signal transduction network in ovarian cancer cells and its role in actomyosin dynamics, cell migration and entosis

Lysophosphatidic acid (LPA) species accumulate in the ascites of ovarian high-grade serous cancer (HGSC) and are associated with short relapse-free survival. LPA is known to support metastatic spread of cancer cells by activating a multitude of signaling pathways via G-protein-coupled receptors of the LPAR family. Systematic unbiased analyses of the LPA-regulated signal transduction network in ovarian cancer cells have, however, not been reported to date. Methods: LPA-induced signaling pathways were identified by phosphoproteomics of both patient-derived and OVCAR8 cells, RNA sequencing, measurements of intracellular Ca²⁺ and cAMP as well as cell imaging. The function of LPARs and downstream signaling components in migration and entosis were analyzed by selective pharmacological inhibitors and RNA interference. Results: Phosphoproteomic analyses identified > 1100 LPA-regulated sites in > 800 proteins and revealed interconnected LPAR1, ROCK/RAC, PKC/D and ERK pathways to play a prominent role within a comprehensive signaling network. These pathways regulate essential processes, including transcriptional responses, actomyosin dynamics, cell migration and entosis. A critical component of this signaling network is MYPT1, a stimulatory subunit of protein phosphatase 1 (PP1), which in turn is a negative regulator of myosin light chain 2 (MLC2). LPA induces phosphorylation of MYPT1 through ROCK (T853) and PKC/ERK (S507), which is majorly driven by LPAR1. Inhibition of MYPT1, PKC or ERK impedes both LPA-induced cell migration and entosis, while interference with ROCK activity and MLC2 phosphorylation selectively blocks entosis, suggesting that MYPT1 figures in both ROCK/MLC2-dependent and -independent pathways. We finally show a novel pathway governed by LPAR2 and the RAC-GEF DOCK7 to be indispensable for the induction of entosis. Conclusion: We have identified a comprehensive LPA-induced signal transduction network controlling LPA-triggered cytoskeletal changes, cell migration and entosis in HGSC cells. Due to its pivotal role in this network, MYPT1 may represent a promising target for interfering with specific functions of PP1 essential for HGSC progression.

Loss of contact inhibition of locomotion in the absence of JAM-A promotes entotic cell engulfment

Entosis is a cell competition process during which tumor cells engulf other tumor cells. It is initiated by metabolic stress or by loss of matrix adhesion, and it provides the winning cell with resources derived from the internalized cell. Using micropatterns as substrates for single cell migration, we find that the depletion of the cell adhesion receptor JAM-A strongly increases the rate of entosis in matrix-adherent cells. The activity of JAM-A in suppressing entosis depends on phosphorylation at Tyr280, which is a binding site for C-terminal Src kinase, and which we have previously found to regulate tumor cell motility and contact inhibition of locomotion (CIL). Loss of JAM-A triggers entosis in matrix-adherent cells but not matrix-deprived cells. Our findings strongly suggest that the increased motility and the perturbed CIL response after the depletion of JAM-A promote entotic cell engulfment, and they link a dysregulation of CIL to entosis in breast cancer cells.

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Cell adhesion receptor JAM-A acts as a suppressor of entosis in tumor cells

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JAM-A suppresses entosis by recruiting Csk, thus limiting Src activity

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Limiting Src activity is required to regulate contact inhibition of locomotion (CIL)

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JAM-A links the regulation of CIL to entosis

Transient cell-in-cell formation underlies tumor relapse and resistance to immunotherapy

Despite the remarkable successes of cancer immunotherapies, the majority of patients will experience only partial response followed by relapse of resistant tumors. While treatment resistance has frequently been attributed to clonal selection and immunoediting, comparisons of paired primary and relapsed tumors in melanoma and breast cancers indicate that they share the majority of clones. Here, we demonstrate in both mouse models and clinical human samples that tumor cells evade immunotherapy by generating unique transient cell-in-cell structures, which are resistant to killing by T cells and chemotherapies. While the outer cells in this cell-in-cell formation are often killed by reactive T cells, the inner cells remain intact and disseminate into single tumor cells once T cells are no longer present. This formation is mediated predominantly by IFNγ-activated T cells, which subsequently induce phosphorylation of the transcription factors signal transducer and activator of transcription 3 (STAT3) and early growth response-1 (EGR-1) in tumor cells. Indeed, inhibiting these factors prior to immunotherapy significantly improves its therapeutic efficacy. Overall, this work highlights a currently insurmountable limitation of immunotherapy and reveals a previously unknown resistance mechanism which enables tumor cells to survive immune-mediated killing without altering their immunogenicity.

Cancer immunotherapies use the body’s own immune system to fight off cancer. But, despite some remarkable success stories, many patients only see a temporary improvement before the immunotherapy stops being effective and the tumours regrow.

It is unclear why this occurs, but it may have to do with how the immune system attacks cancer cells. Immunotherapies aim to activate a special group of cells known as killer T-cells, which are responsible for the immune response to tumours. These cells can identify cancer cells and inject toxic granules through their membranes, killing them. However, killer T-cells are not always effective. This is because cancer cells are naturally good at avoiding detection, and during treatment, their genes can mutate, giving them new ways to evade the immune system. Interestingly, when scientists analysed the genes of tumour cells before and after immunotherapy, they found that many of the genes that code for proteins recognized by T-cells do not change significantly. This suggests that tumours’ resistance to immune attack may be physical, rather than genetic.

To investigate this hypothesis, Gutwillig et al. developed several mouse tumour models that stop responding to immunotherapy after initial treatment. Examining cells from these tumours revealed that when the immune system attacks, they reorganise by getting inside one another. This allows some cancer cells to hide under many layers of cell membrane. At this point killer T-cells can identify and inject the outer cell with toxic granules, but it cannot reach the cells inside.

This ability of cancer cells to hide within one another relies on them recognising when the immune system is attacking. This happens because the cancer cells can detect certain signals released by the killer T-cells, allowing them to hide. Gutwillig et al. identified some of these signals, and showed that blocking them stopped cancer cells from hiding inside each other, making immunotherapy more effective.

This new explanation for how cancer cells escape the immune system could guide future research and lead to new cancer treatments, or approaches to boost existing treatments. Understanding the process in more detail could allow scientists to prevent it from happening, by revealing which signals to block, and when, for best results.

Dynamin-Independent Mechanisms of Endocytosis and Receptor Trafficking

Endocytosis is a fundamental mechanism by which cells perform housekeeping functions. It occurs via a variety of mechanisms and involves many regulatory proteins. The GTPase dynamin acts as a “molecular scissor” to form endocytic vesicles and is a critical regulator among the proteins involved in endocytosis. Some GTPases (e.g., Cdc42, arf6, RhoA), membrane proteins (e.g., flotillins, tetraspanins), and secondary messengers (e.g., calcium) mediate dynamin-independent endocytosis. These pathways may be convergent, as multiple pathways exist in a single cell. However, what determines the specific path of endocytosis is complex and challenging to comprehend. This review summarizes the mechanisms of dynamin-independent endocytosis, the involvement of microRNAs, and factors that contribute to the cellular decision about the specific route of endocytosis.

Cell-in-cell phenomenon in urinary sediment: a case report

The internalization of apoptotic cells by non-phagocytic cells has been observed in different tissues and could be an important mechanism for the elimination of dying cells. Here, we describe a probable event of phagocytosis of apoptotic cells mediated by urothelial cells in urinary sediment. A 90-years-old male patient was admitted unconscious to the hospital, visible signs included: pale skin and dry mucous membranes, presumptively diagnosed as dehydration. Blood test revealed anaemia (haemoglobin 130 g/L) and hyperglycaemia (glucose 7.8 mmol/L), urinalysis showed a picture of urinary tract infection (leukocyturia and bacteriuria). The microscopic analysis of urinary sediment revealed the presence of urothelial cells and leukocytes internalized in urothelial cells. Anti-CD68 (membrane marker of macrophages) was tested by immunocytochemistry and a negative result was observed. Based on the findings phagocytosis of apoptotic cells mediated by urothelial cells was identified. This phenomenon can be observed in urinary sediment and should not be confused with a neoplastic process since it is a physiological event of cell elimination.

Cell Fusion-Related Proteins and Signaling Pathways, and Their Roles in the Development and Progression of Cancer

Cell fusion is involved in many physiological and pathological processes, including gamete binding, and cancer development. The basic processes of cell fusion include membrane fusion, cytoplasmic mixing, and nuclear fusion. Cell fusion is regulated by different proteins and signaling pathways. Syncytin-1, syncytin-2, glial cell missing 1, galectin-1 and other proteins (annexins, myomaker, myomerger etc.) involved in cell fusion via the cyclic adenosine-dependent protein kinase A, mitogen-activated protein kinase, wingless/integrase-1, and c-Jun N-terminal kinase signaling pathways. In the progression of malignant tumors, cell fusion is essential during the organ-specific metastasis, epithelial-mesenchymal transformation, the formation of cancer stem cells (CSCs), cancer angiogenesis and cancer immunity. In addition, diploid cells can be induced to form polyploid giant cancer cells (PGCCs) via cell fusion under many kinds of stimuli, including cobalt chloride, chemotherapy, radiotherapy, and traditional Chinese medicine. PGCCs have CSC-like properties, and the daughter cells derived from PGCCs have a mesenchymal phenotype and exhibit strong migration, invasion, and proliferation abilities. Therefore, exploring the molecular mechanisms of cell fusion can enable us better understand the development of malignant tumors. In this review, the basic process of cell fusion and its significance in cancer is discussed.

Preliminary evidence for the presence of multiple forms of cell death in diabetes cardiomyopathy

Diabetic mellitus (DM) is a common degenerative chronic metabolic disease often accompanied by severe cardiovascular complications (DCCs) as major causes of death in diabetic patients with diabetic cardiomyopathy (DCM) as the most common DCC. The metabolic disturbance in DCM generates the conditions/substrates and inducers/triggers and activates the signaling molecules and death executioners leading to cardiomyocyte death which accelerates the development of DCM and the degeneration of DCM to heart failure. Various forms of programmed active cell death including apoptosis, pyroptosis, autophagic cell death, autosis, necroptosis, ferroptosis and entosis have been identified and characterized in many types of cardiac disease. Evidence has also been obtained for the presence of multiple forms of cell death in DCM. Most importantly, published animal experiments have demonstrated that suppression of cardiomyocyte death of any forms yields tremendous protective effects on DCM. Herein, we provide the most updated data on the subject of cell death in DCM, critical analysis of published results focusing on the pathophysiological roles of cell death, and pertinent perspectives of future studies.

RNA modifications act as regulators of cell death

Currently, more than one hundred types of RNA modifications have been found, and many of these modifications are reversible and dynamically regulated. RNA modifications can regulate RNA stability and translation and are thus involved in multiple biological activities. Recently, RNA modifications have been shown to have important roles in the regulation of cell death. Cell death is a critical process that maintains tissue homoeostasis and is regulated by multiple pathways in response to specific stimuli. In this review, we summarize the current understanding of the roles of RNA modifications in cell death mediation and discuss the prospects of such research.Abbreviations: m6A, N6-Methyladenosine; m6Am, N6,2'-O-Dimethyladenosine; m1A, N1-Methyladenosine; m5C, 5-Methylcytosine; hm5C, 5-Hydroxymethylcytosine; Ψ, pseudouridine; A-to-I, adenosine-to- inosine; hnRNPs, heterogeneous nuclear ribonucleoproteins; MOMP, mitochondrial outer membrane permeabilization; DD, death domain; DISC, death-inducing signalling complex; DED, death effector domain; FADD, FAS-associated protein with the death domain; TRADD, TNF receptor-associated protein with death domain; CMA, chaperone- mediated autophagy; PE, phosphatidylethanolamine; AD, alzheimer's disease; AML, acute myeloid leukaemia; miR, microRNA; 6-OHDA, 6-hydroxydopamine hydrochloride; R-2HG, R-2-hydroxyglutarate; IRES, internal ribosome entry site; BMSCs, bone-derived mesenchymal stem cells; NPCs, nucleus pulposus cells; HsCG, human chorionic gonadotropin; snoRNAs, small nucleolar RNAs; ER, endoplasmic reticulum; lncRNAs, long noncoding RNAs; TNM, tumour-node-metastasis.

TRAIL signaling promotes entosis in colorectal cancer

Entosis is a form of nonphagocytic cell-in-cell (CIC) interaction where a living cell enters into another. Tumors show evidence of entosis; however, factors controlling entosis remain to be elucidated. Here, we find that besides inducing apoptosis, TRAIL signaling is a potent activator of entosis in colon cancer cells. Initiation of both apoptosis and entosis requires TRAIL receptors DR4 and DR5; however, induction of apoptosis and entosis diverges at caspase-8 as its structural presence is sufficient for induction of entosis but not apoptosis. Although apoptosis and entosis are morphologically and biochemically distinct, knockout of Bax and Bak, or inhibition of caspases, also inhibits entotic cell death and promotes survival and release of inner cells. Analysis of colorectal cancer tumors reveals a significant association between TRAIL signaling and CIC structures. Finally, the presence of CIC structures in the invasive front regions of colorectal tumors shows a strong correlation with adverse patient prognosis.

The roles of GTPase-activating proteins in regulated cell death and tumor immunity

GTPase-activating protein (GAP) is a negative regulator of GTPase protein that is thought to promote the conversion of the active GTPase-GTP form to the GTPase-GDP form. Based on its ability to regulate GTPase proteins and other domains, GAPs are directly or indirectly involved in various cell requirement processes. We reviewed the existing evidence of GAPs regulating regulated cell death (RCD), mainly apoptosis and autophagy, as well as some novel RCDs, with particular attention to their association in diseases, especially cancer. We also considered that GAPs could affect tumor immunity and attempted to link GAPs, RCD and tumor immunity. A deeper understanding of the GAPs for regulating these processes could lead to the discovery of new therapeutic targets to avoid pathologic cell loss or to mediate cancer cell death.

Exploring rare cellular activity in more than one million cells by a transscale scope

In many phenomena of biological systems, not a majority, but a minority of cells act on the entire multicellular system causing drastic changes in the system properties. To understand the mechanisms underlying such phenomena, it is essential to observe the spatiotemporal dynamics of a huge population of cells at sub-cellular resolution, which is difficult with conventional tools such as microscopy and flow cytometry. Here, we describe an imaging system named AMATERAS that enables optical imaging with an over-one-centimeter field-of-view and a-few-micrometer spatial resolution. This trans-scale-scope has a simple configuration, composed of a low-power lens for machine vision and a hundred-megapixel image sensor. We demonstrated its high cell-throughput, capable of simultaneously observing more than one million cells. We applied it to dynamic imaging of calcium ions in HeLa cells and cyclic-adenosine-monophosphate in Dictyostelium discoideum, and successfully detected less than 0.01% of rare cells and observed multicellular events induced by these cells.

Mechanisms of Regulated Cell Death: Current Perspectives

Balancing cell survival and cell death is fundamental to development and homeostasis. Cell death is regulated by multiple interconnected signaling pathways and molecular mechanisms. Regulated cell death (RCD) is implicated in fundamental processes such as organogenesis and tissue remodeling, removal of unnecessary structures or cells, and regulation of cell numbers. RCD can also be triggered by exogenous perturbations of the intracellular or extracellular microenvironment when the adaptive processes that respond to stress fail. During the past few years, many novel forms of non-apoptotic RCD have been identified, and the characterization of RCD mechanisms at a molecular level has deepened our understanding of diseases encountered in human and veterinary medicine. Given the complexity of these processes, it has become clear that the identification of RCD cannot be based simply on morphologic characteristics and that descriptive and diagnostic terms presently used by pathologists-such as individual cell apoptosis or necrosis-appear inadequate and possibly misleading. In this review, the current understanding of the molecular machinery of each type of non-apoptotic RCD mechanisms is outlined. Due to the continuous discovery of new mechanisms or nuances of previously described processes, the limitations of the terms apoptosis and necrosis to indicate microscopic findings are also reported. In addition, the need for a standard panel of biomarkers and functional tests to adequately characterize the underlying RCD and its role as a mechanism of disease is considered.

Different types of cell death in vascular diseases

In a mature organism, tissue homeostasis is regulated by cell division and cell demise as the two major physiological procedures. There is increasing evidence that deregulation of these processes is important in the pathogenicity of main diseases, including myocardial infarction, stroke, atherosclerosis, and inflammatory diseases. Therefore, there are ongoing efforts to discover modulating factors of the cell cycle and cell demise planners aiming at shaping innovative therapeutically modalities to the therapy of such diseases. Although the life of a cell is terminated by several modes of action, a few cell deaths exist-some of which resemble apoptosis and/or necrosis, and most of them are different from one another-that contribute to a wide range of functions to either support or disrupt the homoeostasis. Even in normal physiological conditions, cell life is severe within the cardiovascular system. Cells are persistently undergoing stretch, contraction, injurious metabolic byproducts, and hemodynamic forces, and a few of cells sustain decade-long lifetimes. The duration of vascular disease causes further exposure of vascular cells to a novel range of offences, most of which induce cell death. There is growing evidence on consequences of direct damage to a cell, as well as on responses of adjacent and infiltrating cells, which also have an effect on the pathology. In this study, by focusing on different pathways of cell death in different vascular diseases, an attempt is made to open a new perspective on the therapeutic goals associated with cell death in these diseases.

The implication of ROCK 2 as a potential senotherapeutic target via the suppression of the harmful effects of the SASP: Do senescent cancer cells really engulf the other cells?

Chemotherapy-induced senescent cancer cells secrete several factors in their microenvironment called SASP. Accumulated evidence states that SASP is responsible for some of the harmful effects of chemotherapy such as drug resistance and the induction of cancer cell proliferation, migration, and invasion. Therefore, to develop senolytic and/or senomorphic drugs, targeting the senescent cells gains importance as a new strategy for preventing the damage that senescent cancer cells cause. In the current work, we evaluated whether Rho/Rho kinase pathway has the potential to be used as a target pathway for the development of senolytic and/or senomorphic drugs in doxorubicin-induced senescent cancer cell lines. We have determined that inhibition of Rho/Rho kinase pathway with CT04 and Y27632 reduced the secretory activity of senescent cancer cells and changed the composition of SASP. Our results indicate that ROCK 2 isoform was responsible for these observed effects on the SASP. In addition, non-senescent cancer cell proliferation and migration accelerated by senescent cells were set back to the pre-induction levels after ROCK inhibition. Moreover, contrary to the previous observations, another important finding of the current work is that senescent HeLa and A549 cells did not engulf the non-senescent HeLa, A549 cells, and non-cancer HUVEC. These results indicate that ROCK inhibitors, in particular ROCK 2 specific inhibitors, have the potential to be developed as novel senomorphic drugs. In addition, we found that all senescent cancer cells do not share the same engulfment ability, and this process should not be generalized.

Cell-cell fusions and cell-in-cell phenomena in healthy cells and cancer: Lessons from protists and invertebrates

Herein we analyze two special routes of the multinucleated cells' formation - the fusion of mononuclear cells and the formation of cell-in-cell structures - in the healthy tissues and in tumorigenesis. There are many theories of tumorigenesis based on the phenomenon of emergence of the hybrid cancer cells. We consider the phenomena, which are rarely mentioned in those theories: namely, cellularization of syncytium or coenocytes, and the reversible or irreversible somatogamy. The latter includes the short-term and the long-term vegetative (somatic) cells' fusions in the life cycles of unicellular organisms. The somatogamy and multinuclearity have repeatedly and independently emerged in various groups of unicellular eukaryotes. These phenomena are among dominant survival and biodiversity sustaining strategies in protists and we admit that they can likely play an analogous role in cancer cells.

CNS-localized myeloid cells capture living invading T cells during neuroinflammation

To study the role of myeloid cells in the central nervous system (CNS) in the pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), we used intravital microscopy, assessing local cellular interactions in vivo in EAE animals and ex vivo in organotypic hippocampal slice cultures. We discovered that myeloid cells actively engulf invading living Th17 lymphocytes, a process mediated by expression of activation-dependent lectin and its T cell–binding partner, N-acetyl-D-glucosamine (GlcNAc). Stable engulfment resulted in the death of the engulfed cells, and, remarkably, enhancement of GlcNAc exposure on T cells in the CNS ameliorated clinical EAE symptoms. These findings demonstrate the ability of myeloid cells to directly react to pathogenic T cell infiltration by engulfing living T cells. Amelioration of EAE via GlcNAc treatment suggests a novel first-defense pathway of myeloid cells as an initial response to CNS invasion and demonstrates that T cell engulfment by myeloid cells can be therapeutically exploited in vivo.

Role of tumor cell senescence in non-professional phagocytosis and cell-in-cell structure formation

Background

Non-professional phagocytosis is usually triggered by stimuli such as necrotic cell death. In tumor therapy, the tumors often disappear slowly and only long time after the end of therapy. Here, tumor therapy inactivates the cells by inducing senescence. Therefore, study focused whether senescence is a stimulus for non-professional phagocytosis or whether senescent cells themselves phagocytize non-professionally.

Results

Senescence was induced in cell lines by camptothecin and a phagocytosis assay was performed. In tissue of a cohort of 192 rectal cancer patients senescence and non-professional phagocytosis was studied by anti-histone H3K9me3 and anti-E-cadherin staining. Senescent fibroblasts and pancreas carcinoma cells phagocytize necrotic cells but are not phagocytized. In the tissue of rectal carcinoma, senescent cells can phagocytize and can be phagocytized. A high number of senescent cells and, at the same time, high numbers of non-professional phagocytizing cells in the rectal carcinoma tissue lead to an extremely unfavorable prognosis regarding overall survival.

Conclusion

Senescent cells can be non-professionally phagocytized and at the same time they can non-professionally phagocytize in vivo. In vitro experiments indicate that it is unlikely that senescence is a strong trigger for non-professional phagocytosis. Combined high rates of non-professional phagocytosis and high rates of senescence are an extremely poor prognostic factor for overall survival.

Entosis and apical cell extrusion constitute a tumor-suppressive mechanism downstream of Matriptase

Armistead et al. show that in a bilayered epithelium in vivo, apical cell extrusion of basal cells is achieved via their engulfment by surface cells. In zebrafish hai1a mutants, this constitutes a tumor-suppressive mechanism, revealing a double face of Matriptase.

The type II transmembrane serine protease Matriptase 1 (ST14) is commonly known as an oncogene, yet it also plays an understudied role in suppressing carcinogenesis. This double face is evident in the embryonic epidermis of zebrafish loss-of-function mutants in the cognate Matriptase inhibitor Hai1a (Spint1a). Mutant embryos display epidermal hyperplasia, but also apical cell extrusions, during which extruding outer keratinocytes carry out an entosis-like engulfment and entrainment of underlying basal cells, constituting a tumor-suppressive effect. These counteracting Matriptase effects depend on EGFR and the newly identified mediator phospholipase D (PLD), which promotes both mTORC1-dependent cell proliferation and sphingosine-1-phosphate (S1P)–dependent entosis and apical cell extrusion. Accordingly, hypomorphic hai1a mutants heal spontaneously, while otherwise lethal hai1a amorphs are efficiently rescued upon cotreatment with PLD inhibitors and S1P. Together, our data elucidate the mechanisms underlying the double face of Matriptase function in vivo and reveal the potential use of combinatorial carcinoma treatments when such double-face mechanisms are involved.

Cell death in animal development

Cell death is an important facet of animal development. In some developing tissues, death is the ultimate fate of over 80% of generated cells. Although recent studies have delineated a bewildering number of cell death mechanisms, most have only been observed in pathological contexts, and only a small number drive normal development. This Primer outlines the important roles, different types and molecular players regulating developmental cell death, and discusses recent findings with which the field currently grapples. We also clarify terminology, to distinguish between developmental cell death mechanisms, for which there is evidence for evolutionary selection, and cell death that follows genetic, chemical or physical injury. Finally, we suggest how advances in understanding developmental cell death may provide insights into the molecular basis of developmental abnormalities and pathological cell death in disease.

Cell-in-Cell Structures in the Liver: A Tale of Four E's

The liver is our largest internal organ and it plays major roles in drug detoxification and immunity, where the ingestion of extracellular material through phagocytosis is a critical pathway. Phagocytosis is the deliberate endocytosis of large particles, microbes, dead cells or cell debris and can lead to cell-in-cell structures. Various types of cell endocytosis have been recently described for hepatic epithelia (hepatocytes), which are non-professional phagocytes. Given that up to 80% of the liver comprises hepatocytes, the biological impact of cell-in-cell structures in the liver can have profound effects in liver regeneration, inflammation and cancer. This review brings together the latest reports on four types of endocytosis in the liver -efferocytosis, entosis, emperipolesis and enclysis, with a focus on hepatocyte biology.

Cell death mechanisms in eukaryotes

Like the organism they constitute, the cells also die in different ways. The death can be predetermined, programmed, and cleanly executed, as in the case of apoptosis, or it can be traumatic, inflammatory, and sudden as many types of necrosis exemplify. Nevertheless, there are a number of cell deaths-some of them bearing a resemblance to apoptosis and/or necrosis, and many, distinct from each-that serve a multitude of roles in either supporting or disrupting the homoeostasis. Apoptosis is coordinated by death ligands, caspases, b-cell lymphoma-2 (Bcl-2) family proteins, and their downstream effectors. Events that can lead to apoptosis include mitotic catastrophe and anoikis. Necrosis, although it has been considered an abrupt and uncoordinated cell death, has many molecular events associated with it. There are cell death mechanisms that share some standard features with necrosis. These include methuosis, necroptosis, NETosis, pyronecrosis, and pyroptosis. Autophagy, generally a catabolic pathway that operates to ensure cell survival, can also kill the cell through mechanisms such as autosis. Other cell-death mechanisms include entosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Cell-in-Cell Phenomenon and Its Relationship With Tumor Microenvironment and Tumor Progression: A Review

The term cell-in-cell, morphologically, refers to the presence of one cell within another. This phenomenon can occur in tumors but also among non-tumor cells. The cell-in-cell phenomenon was first observed 100 years ago, and it has since been found in a variety of tumor types. Recently, increasing attention has been paid to this phenomenon and the underlying mechanism has gradually been elucidated. There are three main related process: cannibalism, emperipolesis, and entosis. These processes are affected by many factors, including the tumor microenvironment, mitosis, and genetic factors. There is considerable evidence to suggest that the cell-in-cell phenomenon is associated with the prognosis of cancers, and it promotes tumor progression in most situations. Notably, in pancreatic cancer, the cell-in-cell phenomenon is associated with reduced metastasis, which is the opposite of what happens in other tumor types. Thus, it can also inhibit tumor progression. Studies show that cell-in-cell structure formation is affected by the tumor microenvironment, and that it may lead to changes in cellular characteristics. In this review, we summarize the different cell-in-cell processes and discuss their role in tumor progression and how they are regulated by different mechanisms.

Chemotherapy-induced senescent cancer cells engulf other cells to enhance their survival

In chemotherapy-treated breast cancer, wild-type p53 preferentially induces senescence over apoptosis, resulting in a persisting cell population constituting residual disease that drives relapse and poor patient survival via the senescence-associated secretory phenotype. Understanding the properties of tumor cells that allow survival after chemotherapy treatment is paramount. Using time-lapse and confocal microscopy to observe interactions of cells in treated tumors, we show here that chemotherapy-induced senescent cells frequently engulf both neighboring senescent or nonsenescent tumor cells at a remarkable frequency. Engulfed cells are processed through the lysosome and broken down, and cells that have engulfed others obtain a survival advantage. Gene expression analysis showed a marked up-regulation of conserved macrophage-like program of engulfment in chemotherapy-induced senescent cell lines and tumors. Our data suggest compelling explanations for how senescent cells persist in dormancy, how they manage the metabolically expensive process of cytokine production that drives relapse in those tumors that respond the worst, and a function for their expanded lysosomal compartment.

Fundamental Mechanisms of Regulated Cell Death and Implications for Heart Disease

Twelve regulated cell death programs have been described. We review in detail the basic biology of nine including death receptor-mediated apoptosis, death receptor-mediated necrosis (necroptosis), mitochondrial-mediated apoptosis, mitochondrial-mediated necrosis, autophagy-dependent cell death, ferroptosis, pyroptosis, parthanatos, and immunogenic cell death. This is followed by a dissection of the roles of these cell death programs in the major cardiac syndromes: myocardial infarction and heart failure. The most important conclusion relevant to heart disease is that regulated forms of cardiomyocyte death play important roles in both myocardial infarction with reperfusion (ischemia/reperfusion) and heart failure. While a role for apoptosis in ischemia/reperfusion cannot be excluded, regulated forms of necrosis, through both death receptor and mitochondrial pathways, are critical. Ferroptosis and parthanatos are also likely important in ischemia/reperfusion, although it is unclear if these entities are functioning as independent death programs or as amplification mechanisms for necrotic cell death. Pyroptosis may also contribute to ischemia/reperfusion injury, but potentially through effects in non-cardiomyocytes. Cardiomyocyte loss through apoptosis and necrosis is also an important component in the pathogenesis of heart failure and is mediated by both death receptor and mitochondrial signaling. Roles for immunogenic cell death in cardiac disease remain to be defined but merit study in this era of immune checkpoint cancer therapy. Biology-based approaches to inhibit cell death in the various cardiac syndromes are also discussed.

Improving tumour budding evaluation in colon cancer by extending the assessment area in colectomy specimens

AIMS

It is recommended that tumour budding in colon cancer be counted on haematoxylin and eosin-stained sections in a hotspot area of 0.785 mm² with a ×20 microscope objective. However, tumour buds may be difficult to visualise on haematoxylin and eosin-stained sections, and counting in such a limited area may result in overestimation in cases with focal budding. The aim of this study was to assess the contributions of various factors to improving tumour budding risk stratification: increasing the number of fields counted, using cytokeratin immunostaining, and recording proliferation, the apoptotic index and the emperipoletic index in tumour buds.

METHODS AND RESULTS

We created an exploratory series composed of 172 cases of colon cancer in all stages, and we analysed the survival probability in a second cohort of 158 stage I-II patients. According to our results, counting of budding in 10 fields was the only factor that was significantly correlated with disease-free survival probability in stage I-II patients [hazard ratio (HR) for high versus low grade of 7.64, 95% confidence interval (CI) 5.54-27.92, P = 0.01; HR for intermediate versus low grade of 3.02, 95% CI 1.54-26.72, P = 0.04). Emperipolesis was frequently observed in tumour buds, whereas the mitotic index and the apoptotic index were extremely low. Although cytokeratin immunostaining increased interobserver concordance, it did not improve the accuracy of tumour budding grading.

CONCLUSIONS

According to our results, counting in 10 fields significantly enhanced the budding grade risk stratification in colon cancer patients, and cytokeratin immunostaining could be reserved as a complementary technique for challenging cases with an inflammatory infiltrate and/or striking fibrosis.