RIPK1 Binds MCU to Mediate Induction of Mitochondrial Ca2+ Uptake and Promotes Colorectal Oncogenesis

Autophagy modulation in cancer therapy: Challenges coexist with opportunities

Autophagy, a crucial intracellular degradation process facilitated by lysosomes, plays a pivotal role in maintaining cellular homeostasis. The elucidation of autophagy key genes and signaling pathways has significantly advanced our understanding of this process and has led to the exploration of autophagy as a promising therapeutic approach. This review comprehensively assesses the latest developments in small molecule modulators targeting autophagy. Moreover, the review delves into the most recent strategies for drug discovery, specifically focusing on selective agents that exploit autophagosomes and lysosomes for targeted protein degradation. Additionally, this article highlights the prevailing challenges and outlines potential future advancements in the field. By amalgamating the cutting-edge knowledge in the field, we aim to offer valuable insights and references for the anti-cancer drug development of autophagy-targeted therapies, thus contributing to the advancement of novel therapeutic interventions.

Mitochondrial calcium uniporter complex: Unveiling the interplay between its regulators and calcium homeostasis

The mitochondrial calcium uniporter complex (MCUc), serving as the specific channel for calcium influx into the mitochondrial matrix, is integral to calcium homeostasis and cellular integrity. Given its importance, ongoing research spans various disease models to understand the properties of the MCUc in pathophysiological contexts, but reported a different conclusion. Therefore, this review delves into the profound connection between MCUc-mediated calcium transients and cellular signaling pathways, mitochondrial dynamics, metabolism, and cell death. Additionally, we shed light on the recent advancements concerning the structural intricacies and auxiliary components of the MCUc in both resting and activated states. Furthermore, emphasis is placed on novel extrinsic and intrinsic regulators of the MCUc and their therapeutic implications across a spectrum of diseases. Meanwhile, we employed molecular docking simulations and identified candidate traditional Chinese medicine components with potential binding sites to the MCUc, potentially offering insights for further research on MCUc modulation.

The mitochondrial calcium uniporter: Balancing tumourigenic and anti-tumourigenic responses

Increased malignancy and poor treatability associated with solid tumour cancers have commonly been attributed to mitochondrial calcium (Ca2+) dysregulation. The mitochondrial Ca2+ uniporter complex (mtCU) is the predominant mode of Ca2+ uptake into the mitochondrial matrix. The main components of mtCU are the pore-forming mitochondrial Ca2+ uniporter (MCU) subunit, MCU dominant-negative beta (MCUb) subunit, essential MCU regulator (EMRE) and the gatekeeping mitochondrial Ca2+ uptake 1 and 2 (MICU1 and MICU2) proteins. In this review, we describe mtCU-mediated mitochondrial Ca2+ dysregulation in solid tumour cancer types, finding enhanced mtCU activity observed in colorectal cancer, breast cancer, oral squamous cell carcinoma, pancreatic cancer, hepatocellular carcinoma and embryonal rhabdomyosarcoma. By contrast, decreased mtCU activity is associated with melanoma, whereas the nature of mtCU dysregulation remains unclear in glioblastoma. Furthermore, we show that numerous polymorphisms associated with cancer may alter phosphorylation sites on the pore forming MCU and MCUb subunits, which cluster at interfaces with EMRE. We highlight downstream/upstream biomolecular modulators of MCU and MCUb that alter mtCU-mediated mitochondrial Ca2+ uptake and may be used as biomarkers or to aid in the development of novel cancer therapeutics. Additionally, we provide an overview of the current small molecule inhibitors of mtCU that interact with the Asp residue of the critical Asp-Ile-Met-Glu motif or through other allosteric regulatory mechanisms to block Ca2+ permeation. Finally, we describe the relationship between MCU- and MCUb-mediating microRNAs and mitochondrial Ca2+ uptake that should be considered in the discovery of new treatment approaches for cancer.

Mitochondrial Ca2+ signaling is a hallmark of specific adipose tissue-cancer crosstalk

Obesity is associated with increased risk and worse prognosis of many tumours including those of the breast and of the esophagus. Adipokines released from the peritumoural adipose tissue promote the metastatic potential of cancer cells, suggesting the existence of a crosstalk between the adipose tissue and the surrounding tumour. Mitochondrial Ca2+ signaling contributes to the progression of carcinoma of different origins. However, whether adipocyte-derived factors modulate mitochondrial Ca2+ signaling in tumours is unknown. Here, we show that conditioned media derived from adipose tissue cultures (ADCM) enriched in precursor cells impinge on mitochondrial Ca2+ homeostasis of target cells. Moreover, in modulating mitochondrial Ca2+ responses, a univocal crosstalk exists between visceral adipose tissue-derived preadipocytes and esophageal cancer cells, and between subcutaneous adipose tissue-derived preadipocytes and triple-negative breast cancer cells. An unbiased metabolomic analysis of ADCM identified creatine and creatinine for their ability to modulate mitochondrial Ca2+ uptake, migration and proliferation of esophageal and breast tumour cells, respectively.

MCU complex: Exploring emerging targets and mechanisms of mitochondrial physiology and pathology

BACKGROUND

Globally, the onset and progression of multiple human diseases are associated with mitochondrial dysfunction and dysregulation of Ca2+ uptake dynamics mediated by the mitochondrial calcium uniporter (MCU) complex, which plays a key role in mitochondrial dysfunction. Despite relevant studies, the underlying pathophysiological mechanisms have not yet been fully elucidated.

AIM OF REVIEW

This article provides an in-depth analysis of the current research status of the MCU complex, focusing on its molecular composition, regulatory mechanisms, and association with diseases. In addition, we conducted an in-depth analysis of the regulatory effects of agonists, inhibitors, and traditional Chinese medicine (TCM) monomers on the MCU complex and their application prospects in disease treatment. From the perspective of medicinal chemistry, we conducted an in-depth analysis of the structure-activity relationship between these small molecules and MCU and deduced potential pharmacophores and binding pockets. Simultaneously, key structural domains of the MCU complex in Homo sapiens were identified. We also studied the functional expression of the MCU complex in Drosophila, Zebrafish, and Caenorhabditis elegans. These analyses provide a basis for exploring potential treatment strategies targeting the MCU complex and provide strong support for the development of future precision medicine and treatments.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The MCU complex exhibits varying behavior across different tissues and plays various roles in metabolic functions. It consists of six MCU subunits, an essential MCU regulator (EMRE), and solute carrier 25A23 (SLC25A23). They regulate processes, such as mitochondrial Ca2+ (mCa2+) uptake, mitochondrial adenosine triphosphate (ATP) production, calcium dynamics, oxidative stress (OS), and cell death. Regulation makes it a potential target for treating diseases, especially cardiovascular diseases, neurodegenerative diseases, inflammatory diseases, metabolic diseases, and tumors.

Kinase signalling adaptation supports dysfunctional mitochondria in disease

Mitochondria form a critical control nexus which are essential for maintaining correct tissue homeostasis. An increasing number of studies have identified dysregulation of mitochondria as a driver in cancer. However, which pathways support and promote this adapted mitochondrial function? A key hallmark of cancer is perturbation of kinase signalling pathways. These pathways include mitogen activated protein kinases (MAPK), lipid secondary messenger networks, cyclic-AMP-activated (cAMP)/AMP-activated kinases (AMPK), and Ca2+/calmodulin-dependent protein kinase (CaMK) networks. These signalling pathways have multiple substrates which support initiation and persistence of cancer. Many of these are involved in the regulation of mitochondrial morphology, mitochondrial apoptosis, mitochondrial calcium homeostasis, mitochondrial associated membranes (MAMs), and retrograde ROS signalling. This review will aim to both explore how kinase signalling integrates with these critical mitochondrial pathways and highlight how these systems can be usurped to support the development of disease. In addition, we will identify areas which require further investigation to fully understand the complexities of these regulatory interactions. Overall, this review will emphasize how studying the interaction between kinase signalling and mitochondria improves our understanding of mitochondrial homeostasis and can yield novel therapeutic targets to treat disease.

Mitochondrial Calcium Uniporter (MCU) that Modulates Mitochondrial Calcium Uptake and Facilitates Endometrial Cancer Progression through Interaction with VDAC1

BACKGROUND

Although endometrial cancer represents a frequently diagnosed malignancy of the female reproductive tract, we know very little about the factors that control endometrial cancer.

OBJECTIVE

Our study was presented to investigate the function of MCU in endometrial tumorigenesis and the molecular mechanisms involved.

MATERIALS AND METHODS

A total of 94 endometrial cancer patients were recruited into our cohort. MCU and VDAC1 expression was examined in tumor and normal tissues via immunohistochemistry and immunofluorescence. Associations of MCU and VDAC1 expression with clinicopathological characteristics were evaluated. After transfection with shRNA targeting MCU or full-length MCU plasmids, clone formation, wound healing, transwell and MitoTracker Red staining were separately presented in Ishikawa and RL95-2 cells. Moreover, Western blotting or immunofluorescence was utilized to examine the expression of MCU, VDAC1, Na+/Ca2+/Li+ exchanger (NCLX), and β-catenin under VDAC1 knockdown and/or MCU overexpression or knockdown.

RESULTS

MCU and VDAC1 expression were prominently up-regulated in endometrial cancer tissues and were significantly associated with histological grade, depth of myometrial invasion and lymph node status. MCU up-regulation enhanced clone formation, migration, and mitochondrial activity of endometrial cancer cells. The opposite results were investigated when MCU was silenced. MCU or VDAC1 silencing reduced the expression of MCU, VDAC1, NCLX, and β-catenin. Moreover, VDAC1 knockdown alleviated the promoting effect of MCU overexpression on the above proteins.

CONCLUSION

This investigation demonstrated that MCU-induced mitochondrial calcium uptake plays a critical role in endometrial tumorigenesis through interaction with VDAC1.

Receptor-interacting protein kinase 1 (RIPK1) regulates cervical cancer cells via NF-κB-TNF-α pathway: An in vitro study

INTRODUCTION

Cervical cancer (CC) is associated with high morbidity and mortality rates in women. Members of the receptor-interacting protein kinase (RIPK) family are important regulators of inflammation and cell death. However, the characteristics, molecular functions, and expression mechanisms of RIPK1 in CC remain unclear.

MATERIAL AND METHODS

To determine whether RIPK1 can be used for targeted therapy of CC, we assessed the clinical importance, biological function, and potential impact of RIPK1 in CC in 50 patients with CC. We utilized immunohistochemical staining, transfection, western blotting, cell counting kit-8 assay, colony formation assay, and wound healing assays among others, to elucidate the role of RIPK1 in CC.

RESULTS

RIPK1 expression was higher in tumor tissues than in paracancerous tissues. Poor prognosis of CC was linked to RIPK1 upregulation. Furthermore, silencing RIPK1 significantly inhibited the proliferation, migration, and invasion of CC cells in vitro. We also established that RIPK1 increased cell migration, invasion, and multiplication by regulating nuclear factor kappa-B (NF-κB) and tumor necrosis factor (TNF).

DISCUSSION

RIPK1 activates NF-κB and regulates TNF release to enhance the proliferation and spread of CC cells while suppressing their apoptosis. Therefore, RIPK1 plays a key role in the formation and progression of CC and is a potential target for CC treatment.

A novel RIP1-mediated canonical WNT signaling pathway that promotes colorectal cancer metastasis via β -catenin stabilization-induced EMT

RIP1 (receptor-interacting protein kinase 1) is an important component of TNF-α signaling that contributes to various pathological effects. Here, we revealed new potential roles of RIP1 in controlling WNT/β-catenin canonical signaling to enhance metastasis of colorectal cancer (CRC). First, we showed that WNT3A treatment sequentially increased the expression of RIP1 and β-catenin. Immunohistochemical analyses of human CRC tissue arrays consisting of normal, primary, and metastatic cancers indicated that elevated RIP1 expression might be related to β-catenin expression, carcinogenesis, and metastasis. Intravenous injection of RIP1 over-expressed CRC cells into mice has demonstrated that RIP1 may promote metastasis. Immunoprecipitation (IP) results indicated that WNT3A treatment induces direct binding between RIP1 and β-catenin, and that this stabilizes the β-catenin protein in a manner that depends on the regulation of RIP1 ubiquitination via downregulation of the E3 ligase, cIAP1/2. Elimination of cIAP1/2 expression and inhibition of its ubiquitinase activity enhance WNT3A-induced RIP1 and β-catenin protein expression and binding, which stimulates endothelial-mesenchymal transition (EMT) induction to enhance the migration and invasion of CRC cells in vitro. The results of the in vitro binding assay and IP of exogenous RIP1-containing CRC cells additionally verified the direct binding of RIP1 and β-catenin. RIP1 expression can destroy the β-catenin-β-TrCP complex. Taken together, these results suggest a novel EMT-enhancing role of RIP1 in the WNT pathway and suggest a new canonical WNT3A-RIP1-β-catenin pathway that contributes to CRC malignancy by promoting EMT.

The Mitochondrial Calcium Uniporter (MCU): Molecular Identity and Role in Human Diseases

Calcium (Ca2+) ions act as a second messenger, regulating several cell functions. Mitochondria are critical organelles for the regulation of intracellular Ca2+. Mitochondrial calcium (mtCa2+) uptake is ensured by the presence in the inner mitochondrial membrane (IMM) of the mitochondrial calcium uniporter (MCU) complex, a macromolecular structure composed of pore-forming and regulatory subunits. MtCa2+ uptake plays a crucial role in the regulation of oxidative metabolism and cell death. A lot of evidence demonstrates that the dysregulation of mtCa2+ homeostasis can have serious pathological outcomes. In this review, we briefly discuss the molecular structure and the function of the MCU complex and then we focus our attention on human diseases in which a dysfunction in mtCa2+ has been shown.

Implications of MCU complex in metabolic diseases

Metabolic diseases are considered the primary culprit for physical and mental health of individuals. Although the diagnosis of these diseases is relatively easy, more effective and convenient potent drugs are still being explored. Ca2+ across the inner mitochondrial membrane is a vital intracellular messenger that regulates energy metabolism and cellular Ca2+ homeostasis and is involved in cell death. Mitochondria rely on a selective mitochondrial Ca2+ unidirectional transport complex (MCU complex) in their inner membrane for Ca2+ uptake. We found that the channel contains several subunits and undergoes dramatic transformations in various pathological processes, especially in metabolic diseases. In this way, we believe that the MCU complex becomes a target with significant potential for these diseases. However, there is no review linking the two factors, thus hindering the possibility of new drug production. Here, we highlight the connection between MCU complex-related Ca2+ transport and the pathophysiology of metabolic diseases, adding understanding and insight at the molecular level to provide new insights for targeting MCU to reverse metabolism-related diseases.

The mitochondrial calcium uniporter complex–A play in five acts

Mitochondrial Ca²⁺ (mitCa²⁺) uptake controls both intraorganellar and cytosolic functions. Within the organelle, [Ca²⁺] increases regulate the activity of tricarboxylic acid (TCA) cycle enzymes, thus sustaining oxidative metabolism and ATP production. Reactive oxygen species (ROS) are also generated as side products of oxygen consumption. At the same time, mitochondria act as buffers of cytosolic Ca²⁺ (cytCa²⁺) increases, thus regulating Ca²⁺-dependent cellular processes. In pathological conditions, mitCa²⁺ overload triggers the opening of the mitochondrial permeability transition pore (mPTP) and the release of apoptotic cofactors. MitCa²⁺ uptake occurs in response of local [Ca²⁺] increases in sites of proximity between the endoplasmic reticulum (ER) and the mitochondria and is mediated by the mitochondrial Ca²⁺ uniporter (MCU), a highly selective channel of the inner mitochondrial membrane (IMM). Both channel and regulatory subunits form the MCU complex (MCUC). Cryogenic electron microscopy (Cryo-EM) and crystal structures revealed the correct assembly of MCUC and the function of critical residues for the regulation of Ca²⁺ conductance.

Ca2+ signaling and cell death

Multiple forms of regulated cell death (RCD) have been characterized, each of which originates from the activation of a dedicated molecular machinery. RCD can occur in purely physiological settings or upon failing cellular adaptation to stress. Ca²⁺ions have been shown to physically interact with - and hence regulate - various components of the RCD machinery. Moreover, intracellular Ca²⁺ accumulation can promote organellar dysfunction to degree that can be overtly cytotoxic or sensitize cells to RCD elicited by other stressors. Here, we provide an overview of the main links between Ca²⁺and different forms of RCD, including apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Calcium homeostasis and cancer: insights from endoplasmic reticulum-centered organelle communications

Calcium ion (Ca²⁺) is a ubiquitous and versatile signaling molecule controlling a wide variety of cellular processes, such as proliferation, cell death, migration, and immune response, all fundamental processes essential for the establishment of cancer. In recent decades, the loss of Ca²⁺ homeostasis has been considered an important driving force in the initiation and progression of malignant diseases. The primary intracellular Ca²⁺ store, the endoplasmic reticulum (ER), plays an essential role in maintaining Ca²⁺ homeostasis by coordinating with other organelles and the plasma membrane. Here, we discuss the dysregulation of ER-centered Ca²⁺ homeostasis in cancer, summarize Ca²⁺-based anticancer therapeutics, and highlight the significance of furthering our understanding of Ca²⁺ homeostasis regulation in cancer.

Identification of necroptosis-related genes for predicting prognosis and exploring immune infiltration landscape in colon adenocarcinoma

Background

Necroptosis is a recently discovered form of cell death that plays an important role in the occurrence and development of colon adenocarcinoma (COAD). Our study aimed to construct a risk score model to predict the prognosis of patients with COAD based on necroptosis-related genes.

Methods

The gene expression data of COAD and normal colon samples were obtained from the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx). The least absolute shrinkage and selection operator (LASSO) Cox regression analysis was used to calculate the risk score based on prognostic necroptosis-related differentially expressed genes (DEGs). Based on the risk score, patients were classified into high- and low-risk groups. Then, nomogram models were built based on the risk score and clinicopathological features. Otherwise, the model was verified in the Gene Expression Omnibus (GEO) database. Additionally, the tumor microenvironment (TME) and the level of immune infiltration were evaluated by "ESTIMATE" and single-sample gene set enrichment analysis (ssGSEA). Functional enrichment analysis was carried out to explore the potential mechanism of necroptosis in COAD. Finally, the effect of necroptosis on colon cancer cells was explored through CCK8 and transwell assays. The expression of necroptosis-related genes in colon tissues and cells treated with necroptotic inducers (TNFα) and inhibitors (NEC-1) was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The risk score was an independent prognostic risk factor in COAD. The predictive value of the nomogram based on the risk score and clinicopathological features was superior to TNM staging. The effectiveness of the model was well validated in GSE152430. Immune and stromal scores were significantly elevated in the high-risk group. Moreover, necroptosis may influence the prognosis of COAD via influencing the cancer immune response. In in-vitro experiments, the inhibition of necroptosis can promote proliferation and invasion ability. Finally, the differential expression of necroptosis-related genes in 16 paired colon tissues and colon cancer cells was found.

Conclusion

A novel necroptosis-related gene signature for forecasting the prognosis of COAD has been constructed, which possesses favorable predictive ability and offers ideas for the necroptosis-associated development of COAD.

Bacterial-agglutinating and opsonic activities of RIPK1 in zebrafish

Many studies have demonstrated that receptor interacting protein kinase-1 acts as a crucial mediator in the regulation of immune response, but evidence remains lacking for its direct interaction with bacteria. In this study, we found that challenge with lipopolysaccharide and lipoteichoic acid resulted in a significantly increased transcriptional expression of receptor interacting protein kinase-1 in zebrafish, suggesting the receptor interacting protein kinase-1 is implicated in anti-infectious responses. In accordance, we found that recombinant receptor interacting protein kinase-1 was not only able to bind to Gram-negative and -positive bacteria via interaction with lipopolysaccharide and lipoteichoic acid, but also agglutinate both Gram-negative and -positive bacteria in a Ca²⁺-dependent manner.

Balancing life and death: BCL-2 family members at diverse ER-mitochondrial contact sites

The outer mitochondrial membrane is a busy place. One essential activity for cellular survival is the regulation of membrane integrity by the BCL-2 family of proteins. Another critical facet of the outer mitochondrial membrane is its close approximation with the endoplasmic reticulum. These mitochondrial-associated membranes (MAMs) occupy a significant fraction of the mitochondrial surface and serve as key signaling hubs for multiple cellular processes. Each of these pathways may be considered as forming their own specialized MAM subtype. Interestingly, like membrane permeabilization, most of these pathways play critical roles in regulating cellular survival and death. Recently, the pro-apoptotic BCL-2 family member BOK has been found within MAMs where it plays important roles in their structure and function. This has led to a greater appreciation that multiple BCL-2 family proteins, which are known to participate in numerous functions throughout the cell, also have roles within MAMs. In this review, we evaluate several MAM subsets, their role in cellular homeostasis, and the contribution of BCL-2 family members to their functions.

Regulated cell death (RCD) in cancer: key pathways and targeted therapies

Regulated cell death (RCD), also well-known as programmed cell death (PCD), refers to the form of cell death that can be regulated by a variety of biomacromolecules, which is distinctive from accidental cell death (ACD). Accumulating evidence has revealed that RCD subroutines are the key features of tumorigenesis, which may ultimately lead to the establishment of different potential therapeutic strategies. Hitherto, targeting the subroutines of RCD with pharmacological small-molecule compounds has been emerging as a promising therapeutic avenue, which has rapidly progressed in many types of human cancers. Thus, in this review, we focus on summarizing not only the key apoptotic and autophagy-dependent cell death signaling pathways, but the crucial pathways of other RCD subroutines, including necroptosis, pyroptosis, ferroptosis, parthanatos, entosis, NETosis and lysosome-dependent cell death (LCD) in cancer. Moreover, we further discuss the current situation of several small-molecule compounds targeting the different RCD subroutines to improve cancer treatment, such as single-target, dual or multiple-target small-molecule compounds, drug combinations, and some new emerging therapeutic strategies that would together shed new light on future directions to attack cancer cell vulnerabilities with small-molecule drugs targeting RCD for therapeutic purposes.

Mitochondrial adaptation in cancer drug resistance: prevalence, mechanisms, and management

Drug resistance represents a major obstacle in cancer management, and the mechanisms underlying stress adaptation of cancer cells in response to therapy-induced hostile environment are largely unknown. As the central organelle for cellular energy supply, mitochondria can rapidly undergo dynamic changes and integrate cellular signaling pathways to provide bioenergetic and biosynthetic flexibility for cancer cells, which contributes to multiple aspects of tumor characteristics, including drug resistance. Therefore, targeting mitochondria for cancer therapy and overcoming drug resistance has attracted increasing attention for various types of cancer. Multiple mitochondrial adaptation processes, including mitochondrial dynamics, mitochondrial metabolism, and mitochondrial apoptotic regulatory machinery, have been demonstrated to be potential targets. However, recent increasing insights into mitochondria have revealed the complexity of mitochondrial structure and functions, the elusive functions of mitochondria in tumor biology, and the targeting inaccessibility of mitochondria, which have posed challenges for the clinical application of mitochondrial-based cancer therapeutic strategies. Therefore, discovery of both novel mitochondria-targeting agents and innovative mitochondria-targeting approaches is urgently required. Here, we review the most recent literature to summarize the molecular mechanisms underlying mitochondrial stress adaptation and their intricate connection with cancer drug resistance. In addition, an overview of the emerging strategies to target mitochondria for effectively overcoming chemoresistance is highlighted, with an emphasis on drug repositioning and mitochondrial drug delivery approaches, which may accelerate the application of mitochondria-targeting compounds for cancer therapy.

Identification and validation of necroptosis-related prognostic gene signature and tumor immune microenvironment infiltration characterization in esophageal carcinoma

Background

Esophageal carcinoma (ESCA) is a common malignancy with a poor prognosis. Previous research has suggested that necroptosis is involved in anti-tumor immunity and promotes oncogenesis and cancer metastasis, which in turn affects tumor prognosis. However, the role of necroptosis in ESCA is unclear. This study aimed to investigate the relationships between necroptosis-related genes (NRGs) and ESCA.

Methods and results

The clinical data and gene expression profiles of ESCA patients were extracted from The Cancer Genome Atlas (TCGA), and 159 NRGs were screened from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. We then identified 52 differentially expressed NRGs associated with ESCA and used them for further analysis. Gene ontology (GO) and KEGG functional enrichment analyses showed that these NRGs were mostly associated with the regulation of necroptosis, Influenza A, apoptosis, NOD-like receptor, and NF-Kappa B signaling pathway. Next, univariate and multivariate Cox regression and LASSO analysis were used to identify the correlation between NRGs and the prognosis of ESCA. We constructed a prognostic model to predict the prognosis of ESCA based on SLC25A5, PPIA, and TNFRSF10B; the model classified patients into high- and low-risk subgroups based on the patient’s risk score. Furthermore, the receiver operating characteristic (ROC) curve was plotted, and the model was affirmed to perform moderately well for prognostic predictions. In addition, Gene Expression Omnibus (GEO) datasets were selected to validate the applicability and prognostic value of our predictive model. Based on different clinical variables, we compared the risk scores between the subgroups of different clinical features. We also analyzed the predictive value of this model for drug sensitivity. Moreover, Immunohistochemical (IHC) validation experiments explored that these three NRGs were expressed significantly higher in ESCA tissues than in adjacent non-tumor tissues. In addition, a significant correlation was observed between the three NRGs and immune-cell infiltration and immune checkpoints in ESCA.

Conclusions

In summary, we successfully constructed and validated a novel necroptosis-related signature containing three genes (SLC25A5, PPIA, and TNFRSF10B) for predicting prognosis in patients with ESCA; these three genes might also play a crucial role in the progression and immune microenvironment of ESCA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02423-6.

Establishment of a Necroptosis Related Genes Signature to Predict Prognosis and Therapeutic Response in Colon Cancer

Necroptosis, as a form of programmed cell death, is involved in many physiological and pathological processes. However, its role in cancer progression and therapeutic response remains controversial. Colon cancer is one of the leading causes of cancer death and patients’ response to immune checkpoint blockade vary to a large degree. In this study, we investigated necroptosis related genes (NRGs) alterations in colon cancer by bioinformatics analysis. Colon cancer patients were classified into two subtypes with distinct clinical and molecular features based on NRGs. After finding differentially expressed genes and lasso regression, a prognostic model based on four necroptosis signature genes was constructed. The necroptosis signature was also a good predictor in the field of chemotherapy and immunotherapy in colon cancer. Altogether, this study illustrates the relationship between necroptosis and colon cancer, and establishes a novel scoring method to predict prognosis and therapeutic response in colon cancer patients.

Non-Canonical Programmed Cell Death in Colon Cancer

Simple Summary

Non-canonical PCD is an important player in colon cancer cell suicide. It influences colon cancer in many ways, such as through tumorigenesis, treatment, and prognosis. In this review, we present the mechanism, application, and prospect of different types of non-canonical PCD in colon cancer.

Abstract

Programmed cell death (PCD) is an evolutionarily conserved process of cell suicide that is regulated by various genes and the interaction of multiple signal pathways. Non-canonical programmed cell death (PCD) represents different signaling excluding apoptosis. Colon cancer is the third most incident and the fourth most mortal worldwide. Multiple factors such as alcohol, obesity, and genetic and epigenetic alternations contribute to the carcinogenesis of colon cancer. In recent years, emerging evidence has suggested that diverse types of non-canonical programmed cell death are involved in the initiation and development of colon cancer, including mitotic catastrophe, ferroptosis, pyroptosis, necroptosis, parthanatos, oxeiptosis, NETosis, PANoptosis, and entosis. In this review, we summarized the association of different types of non-canonical PCD with tumorigenesis, progression, prevention, treatments, and prognosis of colon cancer. In addition, the prospect of drug-resistant colon cancer therapy related to non-canonical PCD, and the interaction between different types of non-canonical PCD, was systemically reviewed.

The Regulatory Roles of Mitochondrial Calcium and the Mitochondrial Calcium Uniporter in Tumor Cells

Mitochondria, as the main site of cellular energy metabolism and the generation of oxygen free radicals, are the key switch for mitochondria-mediated endogenous apoptosis. Ca²⁺ is not only an important messenger for cell proliferation, but it is also an indispensable signal for cell death. Ca²⁺ participates in and plays a crucial role in the energy metabolism, physiology, and pathology of mitochondria. Mitochondria control the uptake and release of Ca²⁺ through channels/transporters, such as the mitochondrial calcium uniporter (MCU), and influence the concentration of Ca²⁺ in both mitochondria and cytoplasm, thereby regulating cellular Ca²⁺ homeostasis. Mitochondrial Ca²⁺ transport-related processes are involved in important biological processes of tumor cells including proliferation, metabolism, and apoptosis. In particular, MCU and its regulatory proteins represent a new era in the study of MCU-mediated mitochondrial Ca²⁺ homeostasis in tumors. Through an in-depth analysis of the close correlation between mitochondrial Ca²⁺ and energy metabolism, autophagy, and apoptosis of tumor cells, we can provide a valuable reference for further understanding of how mitochondrial Ca²⁺ regulation helps diagnosis and therapy.

Mitochondrial calcium exchange in physiology and disease

The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.

Lon upregulation contributes to cisplatin resistance by triggering NCLX-mediated mitochondrial Ca2+ release in cancer cells

Mitochondria are the major organelles in sensing cellular stress and inducing the response for cell survival. Mitochondrial Lon has been identified as an important stress protein involved in regulating proliferation, metastasis, and apoptosis in cancer cells. However, the mechanism of retrograde signaling by Lon on mitochondrial DNA (mtDNA) damage remains to be elucidated. Here we report the role of Lon in the response to cisplatin-induced mtDNA damage and oxidative stress, which confers cancer cells on cisplatin resistance via modulating calcium levels in mitochondria and cytosol. First, we found that cisplatin treatment on oral cancer cells caused oxidative damage of mtDNA and induced Lon expression. Lon overexpression in cancer cells decreased while Lon knockdown sensitized the cytotoxicity towards cisplatin treatment. We further identified that cisplatin-induced Lon activates the PYK2-SRC-STAT3 pathway to stimulate Bcl-2 and IL-6 expression, leading to the cytotoxicity resistance to cisplatin. Intriguingly, we found that activation of this pathway is through an increase of intracellular calcium (Ca²⁺) via NCLX, a mitochondrial Na⁺/Ca²⁺ exchanger. We then verified that NCLX expression is dependent on Lon levels; Lon interacts with and activates NCLX activity. NCLX inhibition increased the level of mitochondrial calcium and sensitized the cytotoxicity to cisplatin in vitro and in vivo. In summary, mitochondrial Lon-induced cisplatin resistance is mediated by calcium release into cytosol through NCLX, which activates calcium-dependent PYK2-SRC-STAT3-IL-6 pathway. Thus, our work uncovers the novel retrograde signaling by mitochondrial Lon on resistance to cisplatin-induced mtDNA stress, indicating the potential use of Lon and NCLX inhibitors for better clinical outcomes in chemoresistant cancer patients.

Tumor-intrinsic and immune modulatory roles of receptor-interacting protein kinases

Receptor-interacting protein kinase 1 (RIPK1) and RIPK3 are signaling adaptors that critically regulate cell death and inflammation. Tumors have adapted to subvert RIPK-dependent cell death, suggesting that these processes have key roles in tumor regulation. Moreover, RIPK-driven cancer cell death might bolster durable antitumor immunity. By contrast, there are examples in which RIPKs induce inflammation and aid tumor progression. Furthermore, the RIPKs can exert their effects on tumor growth through regulating the activity of immune effectors in the tumor microenvironment, thus highlighting the context-dependent roles of RIPKs. Here, we review recent advances in the regulation of RIPK activity in tumors and immune cells and how these processes coordinate with each other to control tumorigenesis.

Dihydroartemisinin represses oral squamous cell carcinoma progression through downregulating mitochondrial calcium uniporter

Dysregulation of mitochondrial calcium uniporter (MCU) exerts a carcinogenic effect in several cancers. Nevertheless, the roles of MCU in oral squamous cell carcinoma (OSCC) remain elusive. It has been reported that dihydroartemisinin (DHA) may suppress the progression of OSCC but its associated mechanisms have not been investigated. The purpose of our research was to observe the biological function of MCU on OSCC and its regulatory relationship with DHA. MCU, MICU1, MICU2, N-cadherin, TGF-β and vimentin expression was detected in OSCC and peritumoral tissues by immunohistochemistry and Western blot. Following DHA treatment, the expression of the aforementioned proteins was detected in CAL-27 cells transfected with shMCU or pcDNA3.1-MCU by Western blot or immunofluorescence. Furthermore, clone formation, mitochondrial membrane potential (MMP), wound healing and transwell assays were presented in CAL-27 cells treated with DHA, shMCU or pcDNA3.1-MCU. Our results showed that the members of MCU complex (MCU, MICU1 and MICU2) were overexpressed in OSCC than peritumoral tissues. Furthermore, TGF-β and epithelial to mesenchymal transition (EMT) proteins (N-cadherin and vimentin) exhibited higher expression in OSCC. DHA treatment significantly lowered the expression of MCU in CAL-27 cells. MCU overexpression reversed the inhibitory effects of DHA on MICU1, MICU2, N-cadherin, TGF-β and vimentin. MCU knockdown or DHA suppressed proliferation, MMP and migration of CAL-27 cells. DHA treatment could reverse the effects of MCU overexpression. Collectively, our study demonstrated that MCU was an oncogene of OSCC and DHA exerted a suppressive role on proliferation and migration of OSCC cells by suppressing MCU expression.

Pre-diagnosis Dairy Product Intake and Ovarian Cancer Mortality: Results From the Ovarian Cancer Follow-Up Study (OOPS)

Background: Dairy product consumption is associated with ovarian cancer (OC) incidence. However, limited evidence is available on its influence on OC mortality.

Methods: The association between pre-diagnostic dairy product intake and OC mortality was investigated in the OC follow-up study, which included a hospital-based cohort (n = 853) of women diagnosed with epithelial OC between 2015 and 2020. Pre-diagnosis diet information was collected using a validated food frequency questionnaire. Deaths were ascertained up to March 31, 2021 via death registry linkage. Cox proportional hazards model was used to estimate the adjusted hazard ratio (HR) and 95% confidence interval (CI) for the aforementioned association.

Results: A total of 130 women died during the median follow-up of 37.2 months (interquartile: 24.7–50.2 months). Comparisons of highest to lowest tertile intake showed that pre-diagnosis dairy product use was associated with total OC mortality (HR = 2.03, 95% CI = 1.21–3.40, p trend = 0.06). In addition, short survival was separately associated with protein (HR = 2.09, 95% CI = 1.25–3.49, p trend < 0.05), fat (HR = 2.16, 95% CI = 1.30–3.61, p trend < 0.05), and calcium (HR = 2.03, 95% CI = 1.21–3.4, p trend = 0.06) from dairy intake. Similar positive magnitudes were observed for menopausal status, residual lesions, histological type, and body mass index, although not all of these factors showed statistical significance.

Conclusion: Pre-diagnosis dairy product consumption, including protein, fat, and calcium from dairy intake, was associated with higher mortality among OC survivors.

The latest information on the RIPK1 post-translational modifications and functions

RIPK1 is a protein kinase that simultaneously regulates inflammation, apoptosis, and necroptosis. It is thought that RIPK1 has separate functions through its scaffold structure and kinase domains. Moreover, different post-translational modifications in RIPK1 play distinct or even opposing roles. Under different conditions, in different cells and species, and/or upon exposure to different stimuli, infections, and substrates, RIPK1 activation can lead to diverse results. Despite continuous research, many of the conclusions that have been drawn regarding the complex interactions of RIPK1 are controversial. This review is based on an examination and analysis of recent studies on the RIPK1 structure, post-translational modifications, and activation conditions, which can affect its functions. Finally, because of the diverse functions of RIPK1 and their relevance to the pathogenesis of many diseases, we briefly introduce the roles of RIPK1 in inflammatory and autoimmune diseases and the prospects of its use in future diagnostics and treatments.

MCUR1 is a prognostic biomarker for ovarian cancer patients

PURPOSE

To propose MCUR1 gene as a potential biomarker for ovarian cancer prognosis.

METHODS

The ovarian cancer patient specimen from TCGA database were analyzed using survival analysis. The immune cell infiltration ratio and checkpoints had also been investigated for different expression group of MCUR1. The function of MCUR1 as a ovarian cancer prognosis biomarker was verified in clinic.

RESULTS

The low expression of MCUR1 was associated with the poor prognosis of ovarian cancer patients. The expressions of majority of immune cells and 6 checkpoints in low expression group of MCUR1 were significantly lower than that in high expression group of MCUR1 (P< 0.05). The MCUR1 could be utilized as a prognostic biomarker for ovarian cancer patients in clinic.

CONCLUSION

This study has proposed a potential prognostic biomarker for ovarian cancer patients, which offers a beneficial reference for future ovarian cancer administration.

RIPK3 Activates MLKL-mediated Necroptosis and Inflammasome Signaling during Streptococcus Infection

Community-acquired pneumonia is the most common type of pneumonia and remains a leading cause of morbidity and mortality worldwide. Although many different pathogens can contribute to pneumonia, Streptococcus pneumoniae is one of the common bacterial pathogens that underlie community-acquired pneumonia. RIPK3 (receptor-interacting protein kinase 3) is widely recognized as a key modulator of inflammation and cell death. To elucidate a potential role of RIPK3 in pneumonia, we examined plasma from healthy control subjects and patients positive for streptococcal pneumonia. In human studies, RIPK3 protein concentrations were significantly elevated and were identified as a potential plasma marker of pneumococcal pneumonia. To expand these findings, we used an in vivo murine model of pneumococcal pneumonia to demonstrate that RIPK3 deficiency leads to reduced bacterial clearance, severe pathological damage, and high mortality. Our results illustrated that RIPK3 forms a complex with RIPK1, MLKL (mixed-lineage kinase domain-like protein), and MCU (mitochondrial calcium uniporter) to induce mitochondrial calcium uptake and mitochondrial reactive oxygen species(mROS) production during S. pneumoniae infection. In macrophages, RIPK3 initiated necroptosis via the mROS-mediated mitochondrial permeability transition pore opening and NLRP3 inflammasome activation via the mROS-AKT pathway to protect against S. pneumoniae. In conclusion, our study demonstrated a mechanism by which RIPK3-initiated necroptosis is essential for host defense against S. pneumoniae.

Identification and functional validation of FDA-approved positive and negative modulators of the mitochondrial calcium uniporter

The mitochondrial calcium uniporter (MCU), the highly selective channel responsible for mitochondrial Ca²⁺ entry, plays important roles in physiology and pathology. However, only few pharmacological compounds directly and selectively modulate its activity. Here, we perform high-throughput screening on a US Food and Drug Administration (FDA)-approved drug library comprising 1,600 compounds to identify molecules modulating mitochondrial Ca²⁺ uptake. We find amorolfine and benzethonium to be positive and negative MCU modulators, respectively. In agreement with the positive effect of MCU in muscle trophism, amorolfine increases muscle size, and MCU silencing is sufficient to blunt amorolfine-induced hypertrophy. Conversely, in the triple-negative breast cancer cell line MDA-MB-231, benzethonium delays cell growth and migration in an MCU-dependent manner and protects from ceramide-induced apoptosis, in line with the role of mitochondrial Ca²⁺ uptake in cancer progression. Overall, we identify amorolfine and benzethonium as effective MCU-targeting drugs applicable to a wide array of experimental and disease conditions.

•

We screen an FDA-approved drug library for mitochondrial Ca²⁺ uptake modulators

•

Amorolfine and benzethonium modulate MCU activity

•

Amorolfine increases MCU-dependent mitochondrial metabolism and muscle size

•

Benzethonium decreases MCU-dependent cancer cell growth and migration

Receptor-interacting protein in malignant digestive neoplasms

A deep and comprehensive understanding of factors that contribute to cancer initiation, progression, and evolution is of essential importance. Among them, the serine/threonine and tyrosine kinase-like kinases, also known as receptor interacting proteins (RIPs) or receptor interacting protein kinases (RIPKs), is emerging as important tumor-related proteins due to its complex regulation of cell survival, apoptosis, and necrosis. In this review, we mainly review the relevance of RIP to various malignant digestive neoplasms, including esophageal cancer, gastric cancer, colorectal cancer, hepatocellular carcinoma, gallbladder cancer, cholangiocarcinoma, and pancreatic cancer. Consecutive research on RIPs and its relationship with malignant digestive neoplasms is required, as it ultimately conduces to the etiology and treatment of cancer.

RIPK1 is a negative mediator in Aquaporin 1-driven triple-negative breast carcinoma progression and metastasis

The triple-negative breast carcinoma (TNBC) is the most aggressive subtype of breast cancer. In TNBC, Aquaporin 1 (AQP1), a water-transporting transmembrane protein, is aberrantly enriched in cytoplasm and causes tumor cell death evasion. However, the carcinogenetic bioactivities of cytoplasmic AQP1 cannot be attributed to the canonical "osmotic engine model". In the present study, the receptor-interacting protein kinase 1 (RIPK1), a cell death regulator, was identified to negatively mediate AQP1-driven TNBC progression and metastasis. AQP1 overabundance and RIPK1 depletion occurred in TNBC, which were correlated with aggressive oncological features and poor prognosis. AQP1 bound with RIPK1, resulting in the inhibition of RIPK1/RIPK3/MLKL-mediated necroptosis and RIPK1/caspase-8/caspase-3-mediated apoptosis. Genetic inhibition of RIPK1 significantly exacerbated the pro-tumor effect of AQP1, while ectopic expression of RIPK1 notably blunted AQP1 signaling. Mechanistically, AQP1 binds to the D324 site of RIPK1, and facilitates RIPK1 cleavage and inactivation by excessively activating the caspase-8/RIPK1 negative feedback loop. RIPK1D324K overexpression significantly prevented RIPK1 cleavage and weakened the aggressiveness of AQP1-enriched TNBC cells. Overall, our findings clarify the underlying mechanism of cytoplasmic AQP1-driven TNBC progression and metastasis, in which RIPK1 exerts an essential role as a negative mediator and exhibits the potential as a therapeutic target for TNBC.

Mitochondria: Insights into Crucial Features to Overcome Cancer Chemoresistance

Mitochondria are key regulators of cell survival and are involved in a plethora of mechanisms, such as metabolism, Ca²⁺ signaling, reactive oxygen species (ROS) production, mitophagy and mitochondrial transfer, fusion, and fission (known as mitochondrial dynamics). The tuning of these processes in pathophysiological conditions is fundamental to the balance between cell death and survival. Indeed, ROS overproduction and mitochondrial Ca²⁺ overload are linked to the induction of apoptosis, while the impairment of mitochondrial dynamics and metabolism can have a double-faceted role in the decision between cell survival and death. Tumorigenesis involves an intricate series of cellular impairments not yet completely clarified, and a further level of complexity is added by the onset of apoptosis resistance mechanisms in cancer cells. In the majority of cases, cancer relapse or lack of responsiveness is related to the emergence of chemoresistance, which may be due to the cooperation of several cellular protection mechanisms, often mitochondria-related. With this review, we aim to critically report the current evidence on the relationship between mitochondria and cancer chemoresistance with a particular focus on the involvement of mitochondrial dynamics, mitochondrial Ca²⁺ signaling, oxidative stress, and metabolism to possibly identify new approaches or targets for overcoming cancer resistance.

The ER-mitochondria Ca2+ signaling in cancer progression: Fueling the monster

Cancer is a leading cause of death worldwide. All major tumor suppressors and oncogenes are now recognized to have fundamental connections with metabolic pathways. A hallmark feature of cancer cells is a reprogramming of their metabolism even when nutrients are available. Increasing evidence indicates that most cancer cells rely on mitochondrial metabolism to sustain their energetic and biosynthetic demands. Mitochondria are functionally and physically coupled to the endoplasmic reticulum (ER), the major calcium (Ca²⁺) storage organelle in mammalian cells, through special domains known as mitochondria-ER contact sites (MERCS). In this domain, the release of Ca²⁺ from the ER is mainly regulated by inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), a family of Ca²⁺ release channels activated by the ligand IP3. IP3R mediated Ca²⁺ release is transferred to mitochondria through the mitochondrial Ca²⁺ uniporter (MCU). Once in the mitochondrial matrix, Ca²⁺ activates several proteins that stimulate mitochondrial performance. The role of IP3R and MCU in cancer, as well as the other proteins that enable the Ca²⁺ communication between these two organelles is just beginning to be understood. Here, we describe the function of the main players of the ER mitochondrial Ca²⁺ communication and discuss how this particular signal may contribute to the rise and development of cancer traits.

Molecular machinery regulating mitochondrial calcium levels: The nuts and bolts of mitochondrial calcium dynamics

Mitochondria play vital role in regulating the cellular energetics and metabolism. Further, it is a signaling hub for cell survival and apoptotic pathways. One of the key determinants that calibrate both cellular energetics and survival functions is mitochondrial calcium (Ca2+) dynamics. Mitochondrial Ca2+ regulates three Ca2+-sensitive dehydrogenase enzymes involved in tricarboxylic acid cycle (TCA) cycle thereby directly controlling ATP synthesis. On the other hand, excessive Ca2+ concentration within the mitochondrial matrix elevates mitochondrial reactive oxygen species (mROS) levels and causes mitochondrial membrane depolarization. This leads to opening of the mitochondrial permeability transition pore (mPTP) and release of cytochrome c into cytosol eventually triggering apoptosis. Therefore, it is critical for cell to maintain mitochondrial Ca2+ concentration. Since cells can neither synthesize nor metabolize Ca2+, it is the dynamic interplay of Ca2+ handling proteins involved in mitochondrial Ca2+ influx and efflux that take the center stage. In this review we would discuss the key molecular machinery regulating mitochondrial Ca2+ concentration. We would focus on the channel complex involved in bringing Ca2+ into mitochondrial matrix i.e. Mitochondrial Ca2+ Uniporter (MCU) and its key regulators Mitochondrial Ca2+ Uptake proteins (MICU1, 2 and 3), MCU regulatory subunit b (MCUb), Essential MCU Regulator (EMRE) and Mitochondrial Ca2+ Uniporter Regulator 1 (MCUR1). Further, we would deliberate on major mitochondrial Ca2+ efflux proteins i.e. Mitochondrial Na+/Ca2+/Li+ exchanger (NCLX) and Leucine zipper EF hand-containing transmembrane1 (Letm1). Moreover, we would highlight the physiological functions of these proteins and discuss their relevance in human pathophysiology. Finally, we would highlight key outstanding questions in the field.

Chemerin reverses the malignant phenotype and induces differentiation of human hepatoma SMMC7721 cells

Chemerin exhibits an inhibitory effect on hepatocellular carcinoma; however, the underlying mechanism is unclear. Here, low chemerin expression was confirmed in samples of liver cancer patients and hepatoma cells. Chemerin altered hepatoma cell morphology but had no effect on normal hepatocytes. Chemerin inhibited proliferation of several human hepatoma cell lines. Real-time PCR detection of hepatocellular carcinoma markers showed that mRNA levels of albumin and A-type gamma-glutamyl transferase increased whereas those of alpha-fetoprotein, alkaline phosphatase, B-type gamma-glutamyl transferase, insulin-like growth factor II, and human telomerase reverse transcriptase decreased in chemerin-treated SMMC7721 cells. Western blotting revealed that chemerin up-regulated albumin and vimentin expressions, and downregulated alpha-fetoprotein expression. Phosphorylated STAT3 was significantly up-regulated, whereas phosphorylated ERK and AKT were significantly downregulated by chemerin. Chemerin decreased phosphorylated ERK and AKT expression and the cell proliferation induced by PI3K activator 740 Y-P but could not significantly alter phosphorylated STAT3 expression and the cell growth induced by STAT3 inhibitor NSC74859. In conclusion, chemerin reversed the malignant phenotype and induced SMMC7721 cell differentiation by inhibiting MAPK/ERK and PI3K/AKT signaling; growth inhibition by chemerin is not directly related to the JAK/STAT signaling pathway. Our study provides novel evidence that chemerin could be utilized for liver cancer treatment.

BIRD-2, a BH4-domain-targeting peptide of Bcl-2, provokes Bax/Bak-independent cell death in B-cell cancers through mitochondrial Ca2+-dependent mPTP opening

Anti-apoptotic Bcl-2 critically controls cell death by neutralizing pro-apoptotic Bcl-2-family members at the mitochondria. Bcl-2 proteins also act at the endoplasmic reticulum, the main intracellular Ca²⁺-storage organelle, where they inhibit IP₃ receptors (IP₃R) and prevent pro-apoptotic Ca²⁺-signaling events. IP₃R channels are targeted by the BH4 domain of Bcl-2. Some cancer types rely on the IP₃R-Bcl-2 interaction for survival. We previously developed a cell-permeable, BH4-domain-targeting peptide that can abrogate Bcl-2's inhibitory action on IP₃Rs, named Bcl-2 IP₃ receptor disrupter-2 (BIRD-2). This peptide kills several Bcl-2-dependent cancer cell types, including diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukaemia (CLL) cells, by eliciting intracellular Ca²⁺ signalling. However, the exact mechanisms by which these excessive Ca²⁺ signals triggered by BIRD-2 provoke cancer cell death remain elusive. Here, we demonstrate in DLBCL that although BIRD-2 activates caspase 3/7 and provokes cell death in a caspase-dependent manner, the cell death is independent of pro-apoptotic Bcl-2-family members, Bim, Bax and Bak. Instead, BIRD-2 provokes mitochondrial Ca²⁺ overload that is rapidly followed by opening of the mitochondrial permeability transition pore (mPTP). Inhibiting mitochondrial Ca²⁺ overload using Ru265, an inhibitor of the mitochondrial Ca²⁺ uniporter complex counteracts BIRD-2-induced cancer cell death. Finally, we validated our findings in primary CLL patient samples where BIRD-2 provoked mitochondrial Ca²⁺ overload and Ru265 counteracted BIRD-2-induced cell death. Overall, this work reveals the mechanisms by which BIRD-2 provokes cell death, which occurs via mitochondrial Ca²⁺ overload but acts independently of pro-apoptotic Bcl-2-family members.

Altered mitochondrial calcium handling and cell death by necroptosis: An emerging paradigm

The classical necroptosis signaling is mediated by death receptors (DRs) that work in synergy with traditional caspase inhibitory signals. Currently, potential therapeutic molecules are in various phases of clinical trials for a spectrum of pathological conditions associated with necroptosis. However, a non-classical model of necroptosis has also emerged over the last decade with a relatively unexplored molecular mechanism. Although in vitro studies and preclinical models have shown its close association with mitochondrial dysfunction (mito-dysfunction), contradictory reports have emerged which complicate its definitiveness. Though impaired mitochondrial calcium ([Ca²⁺]_m) handling is established in necrotic cell death, how this interplay regulates necroptosis is yet to be elucidated. Taking these questions into consideration, we have discussed various molecular aspects of necroptosis with the emerging role of mito-dysfunction. Based on the central role of altered [Ca²⁺]_m handling in mito-dysfunction mediated necroptosis, we have provided a comprehensive molecular insight into this emerging paradigm. Potential reasons for the contradictory findings regarding the role of mito-dysfunction in necroptosis in general and mitochondrial-dependent necroptosis in specific are discussed. We also provide insights into the current understanding of how [Ca²⁺]_m can be a critical determinant in deciding the cell fate under certain pathological conditions, while under others it may be dispensable. Lastly, we have highlighted the key molecular targets which have a direct implication for therapeutic intervention in conditions that are associated with impaired [Ca²⁺]_m handling and cell death by necroptosis.

MCU-induced mitochondrial calcium uptake promotes mitochondrial biogenesis and colorectal cancer growth

Mitochondrial calcium uniporter (MCU) has an important role in regulating mitochondrial calcium (Ca²⁺) homeostasis. Dysregulation of mitochondrial Ca²⁺ homeostasis has been implicated in various cancers. However, it remains unclear whether MCU regulates mitochondrial Ca²⁺ uptake to promote cell growth in colorectal cancer (CRC). Therefore, in the present study the expression of MCU in CRC tissues and its clinical significance were examined. Following which, the biological function of MCU-mediated mitochondrial Ca²⁺ uptake in CRC cell growth and the underlying mechanisms were systematically evaluated using in in vitro and in vivo assays, which included western blotting, cell viability and apoptosis assays, as well as xenograft nude mice models. Our results demonstrated that MCU was markedly upregulated in CRC tissues at both the mRNA and protein levels. Upregulated MCU was associated with poor prognosis in patients with CRC. Our data reported that upregulation of MCU enhanced the mitochondrial Ca²⁺ uptake to promote mitochondrial biogenesis, which in turn facilitated CRC cell growth in vitro and in vivo. In terms of the underlying mechanism, it was identified that MCU-mediated mitochondrial Ca²⁺ uptake inhibited the phosphorylation of transcription factor A, mitochondrial (TFAM), and thus enhanced its stability to promote mitochondrial biogenesis. Furthermore, our data indicated that increased mitochondrial Ca²⁺ uptake led to increased mitochondrial production of ROS via the upregulation of mitochondrial biogenesis, which subsequently activated NF-κB signaling to accelerate CRC growth. In conclusion, the results indicated that MCU-induced mitochondrial Ca²⁺ uptake promotes mitochondrial biogenesis by suppressing phosphorylation of TFAM, thus contributing to CRC cell growth. Our findings reveal a novel mechanism underlying mitochondrial Ca²⁺-mediated CRC cell growth and may provide a potential pharmacological target for CRC treatment.

The function of Piezo1 in colon cancer metastasis and its potential regulatory mechanism

OBJECTIVE

Increasing evidence has revealed that mechanical stress and elevated mechanical signals promote malignant tumor transformation and metastasis. This study aimed to explore the function of the mechanically activated ion-channel Piezo1 in the colon cancer metastasis and its potential regulatory mechanism.

METHODS

First, we examined the expression levels of Piezo1 and mitochondrial calcium uniporter (MCU) both in colon cancer tissues and assessed the prognostic value of Piezo1 and MCU in a colon cancer cohort (n = 110). Second, functional assays were performed to investigate the effects of Piezo1 and MCU on colon cancer cell migration, invasion, and mitochondrial membrane potential. Third, we analyzed the expression of Piezo1, MCU, and HIF-1α by overexpressing/silencing each other's expression.

RESULTS

We found that Piezo1 was up-regulated and MCU was down-regulated in colon cancer tissues. Piezo1 and MCU were both correlated with poor prognosis of patients with colon cancer. Overexpressing Piezo1 and silencing MCU could promote colon cancer cell migration and metastasis, reduce mitochondrial membrane potential, and promote each other's expression. We also found that HIF-1α was up-regulated in colon cancer tissues. Additionally, silencing Piezo1 inhibited the expression of HIF-1α and VEGF, which was contrary to MCU silencing. Intriguingly, Piezo1-overexpressing cells did not regain their migration behaviors when HIF-1α expression was inhibited, which was accompanied with the re-expression of MCU and VEGF.

CONCLUSION

In our study, Piezo1 is involved in colon cancer cell metastasis. Furthermore, our findings indicated a possible Piezo1-MCU-HIF-1α-VEGF axis, which still need further exploration.

The Role of Mitochondrial Calcium Signaling in the Pathophysiology of Cancer Cells

The pioneering work of Richard Altman on the presence of mitochondria in cells set in motion a field of research dedicated to uncovering the secrets of the mitochondria. Despite limitations in studying the structure and function of the mitochondria, advances in our understanding of this organelle prompted the development of potential treatments for various diseases, from neurodegenerative conditions to muscular dystrophy and cancer. As the powerhouses of the cell, the mitochondria represent the essence of cellular life and as such, a selective advantage for cancer cells. Much of the function of the mitochondria relies on Ca²⁺ homeostasis and the presence of effective Ca²⁺ signaling to maintain the balance between mitochondrial function and dysfunction and subsequently, cell survival. Ca²⁺ regulates the mitochondrial respiration rate which in turn increases ATP synthesis, but too much Ca²⁺ can also trigger the mitochondrial apoptosis pathway; however, cancer cells have evolved mechanisms to modulate mitochondrial Ca²⁺ influx and efflux in order to sustain their metabolic demand and ensure their survival. Therefore, targeting the mitochondrial Ca²⁺ signaling involved in the bioenergetic and apoptotic pathways could serve as potential approaches to treat cancer patients. This chapter will review the role of Ca²⁺ signaling in mediating the function of the mitochondria and its involvement in health and disease with special focus on the pathophysiology of cancer.

Cancer-Related Increases and Decreases in Calcium Signaling at the Endoplasmic Reticulum-Mitochondria Interface (MAMs)

Endoplasmic reticulum (ER)-mitochondria regions are specialized subdomains called also mitochondria-associated membranes (MAMs). MAMs allow regulation of lipid synthesis and represent hubs for ion and metabolite signaling. As these two organelles can module both the amplitude and the spatiotemporal patterns of calcium (Ca²⁺) signals, this particular interaction controls several Ca²⁺-dependent pathways well known for their contribution to tumorigenesis, such as metabolism, survival, sensitivity to cell death, and metastasis. Mitochondria-mediated apoptosis arises from mitochondrial Ca²⁺ overload, permeabilization of the mitochondrial outer membrane, and the release of mitochondrial apoptotic factors into the cytosol. Decreases in Ca²⁺ signaling at the ER-mitochondria interface are being studied in depth as failure of apoptotic-dependent cell death is one of the predominant characteristics of cancer cells. However, some recent papers that linked MAMs Ca²⁺ crosstalk-related upregulation to tumor onset and progression have aroused the interest of the scientific community.In this review, we will describe how different MAMs-localized proteins modulate the effectiveness of Ca²⁺-dependent apoptotic stimuli by causing both increases and decreases in the ER-mitochondria interplay and, specifically, by modulating Ca²⁺ signaling.

Inhibitors of the mitochondrial calcium uniporter for the treatment of disease

The mitochondrial calcium uniporter (MCU) is a protein located in the inner mitochondrial membrane that is responsible for mitochondrial Ca²⁺ uptake. Under certain pathological conditions, dysregulation of Ca²⁺ uptake through the MCU results in cellular dysfunction and apoptotic cell death. Given the role of the MCU in human disease, researchers have developed compounds capable of inhibiting mitochondrial calcium uptake as tools for understanding the role of this protein in cell death. In this article, we describe recent findings on the role of the MCU in mediating pathological conditions and the search for small-molecule inhibitors of this protein for potential therapeutic applications.

Necroptosis regulates tumor repopulation after radiotherapy via RIP1/RIP3/MLKL/JNK/IL8 pathway

Background

Tumor cell repopulation after radiotherapy is a major cause for the tumor radioresistance and recurrence. This study aims to investigate the underlying mechanism of tumor repopulation after radiotherapy, with focus on whether and how necroptosis takes part in this process.

Methods

Necroptosis after irradiation were examined in vitro and in vivo. And the growth-promoting effect of necroptotic cells was investigated by chemical inhibitors or shRNA against necroptosis associated proteins and genes in in vitro and in vivo tumor repopulation models. Downstream relevance factors of necroptosis were identified by western blot and chemiluminescent immunoassays. Finally, the immunohistochemistry staining of identified necroptosis association growth stimulation factor was conducted in human colorectal tumor specimens to verify the relationship with clinical outcome.

Results

Radiation-induced necroptosis depended on activation of RIP1/RIP3/MLKL pathway, and the evidence in vitro and in vivo demonstrated that the inhibition of necroptosis attenuated growth-stimulating effects of irradiated tumor cells on living tumor reporter cells. The JNK/IL-8 were identified as downstream molecules of pMLKL during necroptosis, and inhibition of JNK, IL-8 or IL-8 receptor significantly reduced tumor repopulation after radiotherapy. Moreover, the high expression of IL-8 was associated with poor clinical prognosis in colorectal cancer patients.

Conclusions

Necroptosis associated tumor repopulation after radiotherapy depended on activation of RIP1/RIP3/MLKL/JNK/IL-8 pathway. This novel pathway provided new insight into understanding the mechanism of tumor radioresistance and repopulation, and MLKL/JNK/IL-8 could be developed as promising targets for blocking tumor repopulation to enhance the efficacy of colorectal cancer radiotherapy.

Atrazine induces necroptosis by miR-181-5p targeting inflammation and glycometabolism in carp lymphocytes

Atrazine (ATR) causes environmental problems and damages the health of fish and aquatic animals. MicroRNAs (miRNAs) play important roles in immune regulation. However, the immunotoxicity mechanism of ATR in fish lymphocytes and the role of miRNA in this process remain unclear. To further study these mechanisms, spleen lymphocytes were exposed to 20, 40 and 60 μg/ml ATR for 18 h. Fluorescence staining and flow cytometry showed that the number of necrotic lymphocytes increased after ATR exposure. Compared with the control group, the mRNA expression of miR-181-5p was inhibited and the mRNA levels of TNF-α and HK2 were increased after ATR exposure. Additionally, the NF-κB inflammatory pathway and the levels of glycometabolism-related genes were upregulated. These results suggest that ATR induces inflammation and elevates glycometabolism in lymphocytes. We further found that the mRNA levels of receptor-interacting serine-threonine kinase 1 (RIP1), receptor-interacting serine-threonine kinase 3 (RIP3), mixed lineage kinase domain-like pseudokinase (MLKL), cylindromatosis (CYLD) and Fas-Associated protein with Death Domain (FADD) and the protein levels of RIP3 and MLKL in the treatment groups were significantly increased compared to those in control group, suggesting that ATR causes lymphocyte necroptosis. We conclude that miR-181-5p plays a key role in necroptosis in carp lymphocytes exposed to ATR by downregulating the expression of HK and TNF-α, which increases the level of glycometabolism and induces the inflammatory response, respectively.

Mitochondrial Calcium Uniporter Structure and Function in Different Types of Muscle Tissues in Health and Disease

Calcium ions (Ca²⁺) influx to mitochondrial matrix is crucial for the life of a cell. Mitochondrial calcium uniporter (mtCU) is a protein complex which consists of the pore-forming subunit (MCU) and several regulatory subunits. MtCU is the main contributor to inward Ca²⁺ currents through the inner mitochondrial membrane. Extensive investigations of mtCU involvement into normal and pathological molecular pathways started from the moment of discovery of its molecular components. A crucial role of mtCU in the control of these pathways is now recognized in both health and disease. In particular, impairments of mtCU function have been demonstrated for cardiovascular and skeletal muscle-associated pathologies. This review summarizes the current state of knowledge on mtCU structure, regulation, and function in different types of muscle tissues in health and disease.

Chlorogenic acid effectively treats cancers through induction of cancer cell differentiation

Rationale: Inducing cancer differentiation is a promising approach to treat cancer. Here, we identified chlorogenic acid (CA), a potential differentiation inducer, for cancer therapy, and elucidated the molecular mechanisms underlying its differentiation-inducing effects on cancer cells.

Methods: Cancer cell differentiation was investigated by measuring malignant behavior, including growth rate, invasion/migration, morphological change, maturation, and ATP production. Gene expression was analyzed by microarray analysis, qRT-PCR, and protein measurement, and molecular biology techniques were employed for mechanistic studies. LC/MS analysis was the method of choice for chemical detection. Finally, the anticancer effect of CA was evaluated both in vitro and in vivo.

Results: Cancer cells treated with CA showed reduced proliferation rate, migration/invasion ability, and mitochondrial ATP production. Treating cancer cells with CA resulted in elevated SUMO1 expression through acting on its 3'UTR and stabilizing the mRNA. The increased SUMO1 caused c-Myc sumoylation, miR-17 family downregulation, and p21 upregulation leading to G₀/G₁ arrest and maturation phenotype. CA altered the expression of differentiation-related genes in cancer cells but not in normal cells. It inhibited hepatoma and lung cancer growth in tumor-bearing mice and prevented new tumor development in naïve mice. In glioma cells, CA increased expression of specific differentiation biomarkers Tuj1 and GFAP inducing differentiation and reducing sphere formation. The therapeutic efficacy of CA in glioma cells was comparable to that of temozolomide. CA was detectable both in the blood and brain when administered intraperitoneally in animals. Most importantly, CA was safe even at very high doses.

Conclusion: CA might be a safe and effective differentiation-inducer for cancer therapy. “Educating” cancer cells to differentiate, rather than killing them, could be a novel therapeutic strategy for cancer.