VDAC1 is a molecular target in glioblastoma, with its depletion leading to reprogrammed metabolism and reversed oncogenic properties

Silencing the Mitochondrial Gatekeeper VDAC1 as a Potential Treatment for Bladder Cancer

The strategy for treating bladder cancer (BC) depends on whether there is muscle invasion or not, with the latter mostly treated with intravesical therapy, such as with bacillus Calmette-Guérin (BCG). However, BCG treatment is unsuccessful in 70% of patients, who are then subjected to radical cystectomy. Although immune-checkpoint inhibitors have been approved as a second-line therapy for a subset of BC patients, these have failed to meet primary endpoints in clinical trials. Thus, it is crucial to find a new treatment. The mitochondrial gatekeeper protein, the voltage-dependent anion channel 1 (VDAC1), mediates metabolic crosstalk between the mitochondria and cytosol and is involved in apoptosis. It is overexpressed in many cancer types, as shown here for BC, pointing to its significance in high-energy-demanding cancer cells. The BC cell lines UM-UC3 and HTB-5 express high VDAC1 levels compared to other cancer cell lines. VDAC1 silencing in these cells using siRNA that recognizes both human and mouse VDAC1 (si-m/hVDAC1-B) reduces cell viability, mitochondria membrane potential, and cellular ATP levels. Here, we used two BC mouse models: subcutaneous UM-UC3 cells and chemically induced BC using the carcinogen N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Subcutaneous UM-UC3-derived tumors treated with si-m/hVDAC1 showed inhibited tumor growth and reprogrammed metabolism, as reflected in the reduced expression of metabolism-related proteins, including Glut1, hexokinase, citrate synthase, complex-IV, and ATP synthase, suggesting reduced metabolic activity. Furthermore, si-m/hVDAC1-B reduced the expression levels of cancer-stem-cell-related proteins (cytokeratin-14, ALDH1a), modifying the tumor microenvironment, including decreased angiogenesis, extracellular matrix, tumor-associated macrophages, and inhibited epithelial-mesenchymal transition. The BBN-induced BC mouse model showed a clear carcinoma, with damaged bladder morphology and muscle-invasive tumors. Treatment with si-m/hVDAC1-B encapsulated in PLGA-PEI nanoparticles that were administered intravesically directly to the bladder showed a decreased tumor area and less bladder morphology destruction and muscle invasion. Overall, the obtained results point to the potential of si-m/hVDAC1-B as a possible therapeutic tool for treating bladder cancer.

Association Between Diverse Cell Death Patterns Related Gene Signature and Prognosis, Drug Sensitivity, and Immune Microenvironment in Glioblastoma

Glioblastoma (GBM) is the most invasive type of glioma and is difficult to treat. Diverse programmed cell death (PCD) patterns have a significant association with tumor initiation and progression. A novel prognostic model based on PCD genes may serve as an effective tool to predict the prognosis of GBM. The study incorporated 11 PCD patterns, namely apoptosis, necroptosis, pyroptosis, ferroptosis, cuproptosis, entotic cell death, netotic cell death, parthanatos, lysosome-dependent cell death, autophagy-dependent cell death, alkaliptosis, and oxeiptosis, to develop the model. To construct and validate the model, both bulk and single-cell transcriptome data, along with corresponding clinical data from GBM cases, were obtained from the TCGA-GBM, REMBRANDT, CGGA, and GSE162631 datasets. A cell death-related signature containing 14 genes was constructed with the TCGA-GBM cohort and validated in the REMBRANDT and CGGA datasets. GBM patients with a higher cell death index (CDI) were significantly associated with poorer survival outcomes. Two separate clusters associated with clinical outcomes emerged from unsupervised analysis. A multivariate Cox regression analysis was conducted to examine the association of CDI with clinical characteristics, and a prognostic nomogram was developed. Drug sensitivity analysis revealed high-CDI GBM patients might be resistant to carmustine while sensitive to 5-fluorouracil. Less abundance of natural killer cells was found in GBM cases with high CDI and bulk transcriptome data. A cell death-related prognostic model that could predict the prognosis of GBM patients with good performance was established, which could discriminate between the prognosis and drug sensitivity of GBM.

Identification and validation of voltage-dependent anion channel 1-related genes and immune cell infiltration in diabetic nephropathy

AIMS/INTRODUCTION

This study investigated the roles of voltage-dependent anion channel 1-related differentially expressed genes (VRDEGs) in diabetic nephropathy (DN).

MATERIALS AND METHODS

We downloaded two datasets from patients with DN, namely, GSE30122 and GSE30529, from the Gene Expression Omnibus database. VRDEGs associated with DN were obtained from the intersection of voltage-dependent anion channel 1-related genes from the GeneCards database, and differentially expressed genes were screened according to group (DN/healthy) in the two datasets. The enriched pathways of the VRDEGs were analyzed. Hub genes were selected using a protein-protein interaction network, and their predictive value was verified through receiver operating characteristic curve analysis. The CIBERSORTx software examined hub genes and immune cell infiltration associations. The protein expression of hub genes was verified through immunohistochemistry in 16-week-old db/db mice for experimentation as a model of type 2 DN. Finally, potential drugs targeting hub genes that inhibit DN development were identified.

RESULTS

A total of 57 VRDEGs were identified. The two datasets showed high expression of the PI3K, Notch, transforming growth factor-β, interleukin-10 and interleukin-17 pathways in DN. Five hub genes (ITGAM, B2M, LYZ, C3 and CASP1) associated with DN were identified and verified. Immunohistochemistry showed that the five hub genes were highly expressed in db/db mice, compared with db/m mice. The infiltration of immune cells was significantly correlated with the five hub genes.

CONCLUSIONS

Five hub genes were significantly correlated with immune cell infiltration and might be crucial to DN development. This study provides insight into the mechanisms involved in the pathogenesis of DN.

Role of Glycolytic and Glutamine Metabolism Reprogramming on the Proliferation, Invasion, and Apoptosis Resistance through Modulation of Signaling Pathways in Glioblastoma

Glioma cells exhibit genetic and metabolic alterations that affect the deregulation of several cellular signal transduction pathways, including those related to glucose metabolism. Moreover, oncogenic signaling pathways induce the expression of metabolic genes, increasing the metabolic enzyme activities and thus the critical biosynthetic pathways to generate nucleotides, amino acids, and fatty acids, which provide energy and metabolic intermediates that are essential to accomplish the biosynthetic needs of glioma cells. In this review, we aim to explore how dysregulated metabolic enzymes and their metabolites from primary metabolism pathways in glioblastoma (GBM) such as glycolysis and glutaminolysis modulate anabolic and catabolic metabolic pathways as well as pro-oncogenic signaling and contribute to the formation, survival, growth, and malignancy of glioma cells. Also, we discuss promising therapeutic strategies by targeting the key players in metabolic regulation. Therefore, the knowledge of metabolic reprogramming is necessary to fully understand the biology of malignant gliomas to improve patient survival significantly.

Combining nano-differential scanning fluorimetry and microscale thermophoresis to investigate VDAC1 interaction with small molecules

The mitochondrial voltage-dependent anion channel 1 (VDAC1) plays a central role in metabolism and apoptosis, which makes it a promising therapeutic target. Nevertheless, molecular mechanisms governing VDAC1 functioning remain unclear. Small-molecule ligands specifically interacting with the channel provide an attractive way of exploring its structure-function relationships and can possibly be used as founding stones for future drug-candidates. While around 30 VDAC1 ligands have been identified over the years, various techniques have been used by research teams, making a fair and direct comparison between compounds impossible. To tackle this issue, we performed ligand-binding assays on a representative set of seventeen known VDAC1 ligands using nano-differential scanning fluorimetry and microscale thermophoresis. While all the compounds have been confirmed as VDAC1 ligands by at least one method, combining both technologies lead to the selection of four molecules (cannabidiol, curcumin, DIDS and VBIT4) as chemical starting points for future design of VDAC1 selective ligands.

VDAC as a voltage-dependent mitochondrial gatekeeper under physiological conditions

Mitochondria, composed of two membranes, play a key role in energy production in eukaryotic cells. The main function of the inner membrane is oxidative phosphorylation, while the mitochondrial outer membrane (MOM) seems to control the energy flux and exchange of various charged metabolites between mitochondria and the cytosol. Metabolites cross MOM via the various isoforms of voltage-dependent anion channel (VDAC). In turn, VDACs interact with some enzymes, other proteins and molecules, including drugs. This work aimed to analyze various literature experimental data related to targeting mitochondrial VDACs and VDAC-kinase complexes on the basis of the hypothesis of generation of the outer membrane potential (OMP) and OMP-dependent reprogramming of cell energy metabolism. Our previous model of the VDAC-hexokinase-linked generation of OMP was further complemented in this study with an additional regulation of the MOM permeability by the OMP-dependent docking of cytosolic proteins like tubulin to VDACs. Computational analysis of the model suggests that OMP changes might be involved in the mechanisms of apoptosis promotion through the so-called transient hyperpolarization of mitochondria. The high concordance of the performed computational estimations with many published experimental data allows concluding that OMP generation under physiological conditions is highly probable and VDAC might function as an OMP-dependent gatekeeper of mitochondria, controlling cell life and death. The proposed model of OMP generation allows understanding in more detail the mechanisms of cancer death resistance and anticancer action of various drugs and treatments influencing VDAC voltage-gating properties, VDAC content, mitochondrial hexokinase activity and VDAC-kinase interactions in MOM.

Increase in primary cilia number and length upon VDAC1 depletion contributes to attenuated proliferation of cancer cells

Primary cilia (PCs) that are present in most human cells and perform sensory function or signal transduction are lost in many solid tumors. Previously, we identified VDAC1, best known to regulate mitochondrial bioenergetics, to negatively regulate ciliogenesis. Here, we show that downregulation of VDAC1 in pancreatic cancer-derived Panc1 and glioblastoma-derived U-87MG cells significantly increased ciliation. Those PCs were significantly longer than the control cells. Such increased ciliation possibly inhibited cell cycle, which contributed to reduced proliferation of these cells. VDAC1-depletion also led to longer PCs in quiescent RPE1 cells. Therefore, serum-induced PC disassembly was slower in VDAC1-depleted RPE1 cells. Overall, this study reiterates the importance of VDAC1 in modulating tumorigenesis, due to its novel role in regulating PC disassembly and cilia length.

Glioblastoma Metabolism: Insights and Therapeutic Strategies

Tumor metabolism is emerging as a potential target for cancer therapies. This new approach holds particular promise for the treatment of glioblastoma, a highly lethal brain tumor that is resistant to conventional treatments, for which improving therapeutic strategies is a major challenge. The presence of glioma stem cells is a critical factor in therapy resistance, thus making it essential to eliminate these cells for the long-term survival of cancer patients. Recent advancements in our understanding of cancer metabolism have shown that glioblastoma metabolism is highly heterogeneous, and that cancer stem cells exhibit specific metabolic traits that support their unique functionality. The objective of this review is to examine the metabolic changes in glioblastoma and investigate the role of specific metabolic processes in tumorigenesis, as well as associated therapeutic approaches, with a particular focus on glioma stem cell populations.

Apoptotic proteins with non-apoptotic activity: expression and function in cancer

Apoptosis is a process of programmed cell death in which a cell commits suicide while maintaining the integrity and architecture of the tissue as a whole. Apoptosis involves activation of one of two major pathways: the extrinsic pathway, where extracellular pro-apoptotic signals, transduced through plasma membrane death receptors, activate a caspase cascade leading to apoptosis. The second, the intrinsic apoptotic pathway, where damaged DNA, oxidative stress, or chemicals, induce the release of pro-apoptotic proteins from the mitochondria, leading to the activation of caspase-dependent and independent apoptosis. However, it has recently become apparent that proteins involved in apoptosis also exhibit non-cell death-related physiological functions that are related to the cell cycle, differentiation, metabolism, inflammation or immunity. Such non-conventional activities were predominantly reported in non-cancer cells although, recently, such a dual function for pro-apoptotic proteins has also been reported in cancers where they are overexpressed. Interestingly, some apoptotic proteins translocate to the nucleus in order to perform a non-apoptotic function. In this review, we summarize the unconventional roles of the apoptotic proteins from a functional perspective, while focusing on two mitochondrial proteins: VDAC1 and SMAC/Diablo. Despite having pro-apoptotic functions, these proteins are overexpressed in cancers and this apparent paradox and the associated pathophysiological implications will be discussed. We will also present possible mechanisms underlying the switch from apoptotic to non-apoptotic activities although a deeper investigation into the process awaits further study.

Pro-Apoptotic and Anti-Cancer Activity of the Vernonanthura Nudiflora Hydroethanolic Extract

The mitochondrial voltage-dependent anion channel 1 (VDAC1) protein is involved in several essential cancer hallmarks, including energy and metabolism reprogramming and apoptotic cell death evasion. In this study, we demonstrated the ability of hydroethanolic extracts from three different plants, Vernonanthura nudiflora (Vern), Baccharis trimera (Bac), and Plantago major (Pla), to induce cell death. We focused on the most active Vern extract. We demonstrated that it activates multiple pathways that lead to impaired cell energy and metabolism homeostasis, elevated ROS production, increased intracellular Ca²⁺, and mitochondria-mediated apoptosis. The massive cell death generated by this plant extract's active compounds involves the induction of VDAC1 overexpression and oligomerization and, thereby, apoptosis. Gas chromatography of the hydroethanolic plant extract identified dozens of compounds, including phytol and ethyl linoleate, with the former producing similar effects as the Vern hydroethanolic extract but at 10-fold higher concentrations than those found in the extract. In a xenograft glioblastoma mouse model, both the Vern extract and phytol strongly inhibited tumor growth and cell proliferation and induced massive tumor cell death, including of cancer stem cells, inhibiting angiogenesis and modulating the tumor microenvironment. Taken together, the multiple effects of Vern extract make it a promising potential cancer therapeutic.

Ion Channels in Gliomas-From Molecular Basis to Treatment

Ion channels provide the basis for the nervous system's intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Targeting the Mitochondrial Protein VDAC1 as a Potential Therapeutic Strategy in ALS

Impaired mitochondrial function has been proposed as a causative factor in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), caused by motor neuron degeneration. Mutations in superoxide dismutase (SOD1) cause ALS and SOD1 mutants were shown to interact with the voltage-dependent anion channel 1 (VDAC1), affecting its normal function. VDAC1 is a multi-functional channel located at the outer mitochondrial membrane that serves as a mitochondrial gatekeeper controlling metabolic and energetic crosstalk between mitochondria and the rest of the cell and it is a key player in mitochondria-mediated apoptosis. Previously, we showed that VDAC1 interacts with SOD1 and that the VDAC1-N-terminal-derived peptide prevented mutant SOD1 cytotoxic effects. In this study, using a peptide array, we identified the SOD1 sequence that interacts with VDAC1. Synthetic peptides generated from the identified VDAC1-binding sequences in SOD1 directly interacted with purified VDAC1. We also show that VDAC1 oligomerization increased in spinal cord mitochondria isolated from mutant SOD1G93A mice and rats. Thus, we used the novel VDAC1-specific small molecules, VBIT-4 and VBIT-12, inhibiting VDAC1 oligomerization and subsequently apoptosis and associated processes such as ROS production, and increased cytosolic Ca2+. VBIT-12 was able to rescue cell death induced by mutant SOD1 in neuronal cultures. Finally, although survival was not affected, VBIT-12 administration significantly improved muscle endurance in mutant SOD1G93A mice. Therefore, VBIT-12 may represent an attractive therapy for maintaining muscle function during the progression of ALS.

Silencing VDAC1 to Treat Mesothelioma Cancer: Tumor Reprograming and Altering Tumor Hallmarks

Mesothelioma, an aggressive cancer with a poor prognosis, is linked to asbestos exposure. However, carbon nanotubes found in materials we are exposed to daily can cause mesothelioma cancer. Cancer cells reprogram their metabolism to support increased biosynthetic and energy demands required for their growth and motility. Here, we examined the effects of silencing the expression of the voltage-dependent anion channel 1 (VDAC1), controlling the metabolic and energetic crosstalk between mitochondria and the rest of the cell. We demonstrate that VDAC1 is overexpressed in mesothelioma patients; its levels increase with disease stage and are associated with low survival rates. Silencing VDAC1 expression using a specific siRNA identifying both mouse and human VDAC1 (si-m/hVDAC1-B) inhibits cell proliferation of mesothelioma cancer cells. Treatment of xenografts of human-derived H226 cells or mouse-derived AB1 cells with si-m/hVDAC1-B inhibited tumor growth and caused metabolism reprogramming, as reflected in the decreased expression of metabolism-related proteins, including glycolytic and tricarboxylic acid (-)cycle enzymes and the ATP-synthesizing enzyme. In addition, tumors depleted of VDAC1 showed altered microenvironments and inflammation, both associated with cancer progression. Finally, tumor VDAC1 silencing also eliminated cancer stem cells and induced cell differentiation to normal-like cells. The results show that silencing VDAC1 expression leads to reprogrammed metabolism and to multiple effects from tumor growth inhibition to modulation of the tumor microenvironment and inflammation, inducing differentiation of malignant cells. Thus, silencing VDAC1 is a potential therapeutic approach to treating mesothelioma.

Signal pathways and precision therapy of small-cell lung cancer

Small-cell lung cancer (SCLC) encounters up 15% of all lung cancers, and is characterized by a high rate of proliferation, a tendency for early metastasis and generally poor prognosis. Most of the patients present with distant metastatic disease at the time of clinical diagnosis, and only one-third are eligible for potentially curative treatment. Recently, investigations into the genomic make-up of SCLC show extensive chromosomal rearrangements, high mutational burden and loss-of-function mutations of several tumor suppressor genes. Although the clinical development of new treatments for SCLC has been limited in recent years, a better understanding of oncogenic driver alterations has found potential novel targets that might be suitable for therapeutic approaches. Currently, there are six types of potential treatable signaling pathways in SCLC, including signaling pathways targeting the cell cycle and DNA repair, tumor development, cell metabolism, epigenetic regulation, tumor immunity and angiogenesis. At this point, however, there is still a lack of understanding of their role in SCLC tumor biology and the promotion of cancer growth. Importantly optimizing drug targets, improving drug pharmacology, and identifying potential biomarkers are the main focus and further efforts are required to recognize patients who benefit most from novel therapies in development. This review will focus on the current learning on the signaling pathways, the status of immunotherapy, and targeted therapy in SCLC.

VDAC1 negatively regulates melanogenesis through the Ca2+-calcineurin-CRTC1-MITF pathway

This study revealed an important and novel role of mitochondrial VDAC1 in regulating melanogenesis in resting melanocytes through a Ca²⁺-regulated pathway that is independent of the alpha-MSH/UVB pathway.

Melanocytes produce melanin for protecting DNA from ultraviolet exposure to maintain genomic stability. However, the precise regulation of melanogenesis is not fully understood. VDAC1, which is mainly localized in the outer mitochondrial membrane, functions as a gatekeeper for the entry or exit of Ca²⁺ between mitochondria and the cytosol and participates in multiple physiological processes. Here, we showed a novel role of VDAC1 in melanogenesis. Depletion of VDAC1 increased pigment content and up-regulated melanogenic genes, TYR, TYRP1, and TYRP2. Knockdown of VDAC1 increased free cytosolic Ca²⁺ in cultured melanocytes at the resting state, which activated calcineurin through the Ca²⁺-calmodulin-CaN pathway. The activated CaN dephosphorylated CRTC1 to facilitate its nuclear translocation and ultimately up-regulated the transcription of the master regulator of melanogenesis MITF. Consistently, depletion of Vdac1 in mice led to up-regulation of the transcription of MITF and thereafter its targeted melanogenic genes. These findings suggest that VDAC1 is an important negative regulator of melanogenesis, which expands our knowledge about pigment production and implies its potential role in melanoma.

Identification and validation of serum autoantibodies in children with B-cell acute lymphoblastic leukemia by serological proteome analysis

Background

B-cell acute lymphoblastic leukemia (B-ALL) is the most common malignancy of childhood. Even though significant progresses have been made in the treatment of B-ALL, some pediatric B-ALL have still poor prognosis. The identification of tumor autoantibodies may have utility in early cancer diagnosis and immunotherapy. In this study, we used serological proteome analysis (SERPA) to screen serum autoantibodies of pediatric B-ALL, aiming to contribute to the early detection of B-ALL in children.

Methods

The total proteins from three pooled B-ALL cell lines (NALM-6, REH and BALL-1 cells) were separated using two-dimensional gel electrophoresis (2-DE), which was followed by Western blot by mixed serum samples from children with B-ALL (n=20) or healthy controls (n=20). We analyzed the images of 2-D gel and Western blot by PDQuest software, and then identified the spots of immune responses in B-ALL samples compared with those in control samples. The proteins from spots were identified using mass spectrometry (MS). The autoantibodies against alpha-enolase (α-enolase) and voltage-dependent anion-selective channel protein 1 (VDAC1) were further validated in sera from another 30 children with B-ALL and 25 normal individuals by the use of enzyme-linked immunosorbent assay (ELISA). The protein expression levels of the candidate antigens α-enolase and VDAC1 in B-ALL were thoroughly studied by immunohistochemical analysis.

Results

Utilizing the SERPA approach, α-enolase and VDAC1 were identified as candidate autoantigens in children with B-ALL. The frequencies of autoantibodies against α-enolase and VDAC1 in children with B-ALL were 27% and 23% by using ELISA analysis, respectively, which were significantly higher than those in normal controls (4% and 0, p<0.05). Immunohistochemical analysis showed the expression of α-enolase and VDAC1 was positive in 95% and 85% of B-ALL patients, respectively, but negative expression levels were showed in the control group.

Conclusions

This study incidated that α-enolase and VDAC1 may be the autoantigens associated with B-ALL. Therefore, α-enolase and VDAC1 autoantibodies may be the potential serological markers for children with B-ALL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12953-021-00184-w.

Adverse Effects of Metformin From Diabetes to COVID-19, Cancer, Neurodegenerative Diseases, and Aging: Is VDAC1 a Common Target?

Metformin has been used for treating diabetes mellitus since the late 1950s. In addition to its antihyperglycemic activity, it was shown to be a potential drug candidate for treating a range of other diseases that include various cancers, cardiovascular diseases, diabetic kidney disease, neurodegenerative diseases, renal diseases, obesity, inflammation, COVID-19 in diabetic patients, and aging. In this review, we focus on the important aspects of mitochondrial dysfunction in energy metabolism and cell death with their gatekeeper VDAC1 (voltage-dependent anion channel 1) as a possible metformin target, and summarize metformin’s effects in several diseases and gut microbiota. We question how the same drug can act on diseases with opposite characteristics, such as increasing apoptotic cell death in cancer, while inhibiting it in neurodegenerative diseases. Interestingly, metformin’s adverse effects in many diseases all show VDAC1 involvement, suggesting that it is a common factor in metformin-affecting diseases. The findings that metformin has an opposite effect on various diseases are consistent with the fact that VDAC1 controls cell life and death, supporting the idea that it is a target for metformin.

A Robust Panel Based on Mitochondrial Localized Proteins for Prognostic Prediction of Lung Adenocarcinoma

Due to high energy and material metabolism requirements, mitochondria are frequently active in tumor cells. Our study found that the high energy metabolism status is positively correlated with the poor prognosis of patients with lung adenocarcinoma. We constructed a scoring system (mitoRiskscore) based on the gene expression of specific mitochondrial localized proteins through univariate and LASSO cox regression. It has been shown that high mitoRiskscore was correlated with a shorter survival time after surgery in patients with lung adenocarcinoma. Compared with the typical TNM grading system, the mitoRiskscore gene panel had higher prediction accuracy. A vast number of external verification results ensured its universality. Additionally, the mitoRiskscore could evaluate the metabolic pattern and chemotherapy sensitivity of the tumor samples. Lung adenocarcinoma with higher mitoRiskscore was more active in glycolysis, and oxidative phosphorylation expression of proliferation-related pathway genes was also significantly upregulated. In contrast, patients with low mitoRiskscore had similar metabolic patterns to normal tissues. In order to improve the accuracy of prediction ability and promote clinical usage, we developed a nomogram that combined mitoRiskscore and clinical prognostic factors to predict the 3-year, 5-year, and 10-year survival rates of patients. We also performed in vitro experiments to verify the function of the key genes in the mitoRiskscore panel. In conclusion, the mitoRiskscore scoring system may assist clinicians to judge the postoperative survival rate and chemotherapy of patients with lung adenocarcinoma.

Advances in Intracellular Calcium Signaling Reveal Untapped Targets for Cancer Therapy

Intracellular Ca2+ distribution is a tightly regulated process. Numerous Ca2+ chelating, storage, and transport mechanisms are required to maintain normal cellular physiology. Ca2+-binding proteins, mainly calmodulin and calbindins, sequester free intracellular Ca2+ ions and apportion or transport them to signaling hubs needing the cations. Ca2+ channels, ATP-driven pumps, and exchangers assist the binding proteins in transferring the ions to and from appropriate cellular compartments. Some, such as the endoplasmic reticulum, mitochondria, and lysosomes, act as Ca2+ repositories. Cellular Ca2+ homeostasis is inefficient without the active contribution of these organelles. Moreover, certain key cellular processes also rely on inter-organellar Ca2+ signaling. This review attempts to encapsulate the structure, function, and regulation of major intracellular Ca2+ buffers, sensors, channels, and signaling molecules before highlighting how cancer cells manipulate them to survive and thrive. The spotlight is then shifted to the slow pace of translating such research findings into anticancer therapeutics. We use the PubMed database to highlight current clinical studies that target intracellular Ca2+ signaling. Drug repurposing and improving the delivery of small molecule therapeutics are further discussed as promising strategies for speeding therapeutic development in this area.

VDAC1 Silencing in Cancer Cells Leads to Metabolic Reprogramming That Modulates Tumor Microenvironment

Simple Summary

Tumors are comprised of proliferating cancer cells, and their microenvironment consists of the extracellular matrix, blood vessels, and a variety of tissue cells. The tumor microenvironment functions in cell growth, proliferation, migration, immunity, malignant transformation, and apoptosis. Understanding the molecular interactions between cancer cells and their microenvironment would facilitate the development of therapeutic strategies to disrupt these interactions and fight cancer. Here, we demonstrate that depleting the mitochondrial gatekeeper VDAC1 in human cancer cells in tumors led to metabolic reprogramming, inhibited tumor growth, and disrupted tumor–host interactions. A next-generation sequencing analysis of human lung cell-derived tumors expressing or depleted of VDAC1 allows distinguishing genes of human or murine origin, thus enabling the separation of the bidirectional cross-talk between malignant cells and the tumor microenvironment. A battery of human cancer cell and mouse genes associated with tumor microenvironment formation and remodeling were altered. The results point to VDAC1 as a novel target for both inhibiting tumor growth and modulating the tumor microenvironment, thus influencing cancer progression, migration, and invasion.

Abstract

The tumor microenvironment (TME) plays an important role in cell growth, proliferation, migration, immunity, malignant transformation, and apoptosis. Thus, better insight into tumor–host interactions is required. Most of these processes involve the metabolic reprogramming of cells. Here, we focused on this reprogramming in cancerous cells and its effect on the TME. A major limitation in the study of tumor–host interactions is the difficulty in separating cancerous from non-cancerous signaling pathways within a tumor. Our strategy involved specifically silencing the expression of VDAC1 in the mitochondria of human-derived A549 lung cancer xenografts in mice, but not in the mouse-derived cells of the TME. Next-generation sequencing (NGS) analysis allows distinguishing the human or mouse origin of genes, thus enabling the separation of the bidirectional cross-talk between the TME and malignant cells. We demonstrate that depleting VDAC1 in cancer cells led to metabolic reprogramming, tumor regression, and the disruption of tumor–host interactions. This was reflected in the altered expression of a battery of genes associated with TME, including those involved in extracellular matrix organization and structure, matrix-related peptidases, angiogenesis, intercellular interacting proteins, integrins, and growth factors associated with stromal activities. We show that metabolic rewiring upon mitochondrial VDAC1 silencing in cancer cells affected several components of the TME, such as structural protein matrix metalloproteinases and Lox, and elicited a stromal response resembling the reaction to a foreign body in wound healing. As tumor progression requires a cooperative interplay between the host and cancer cells, and the ECM is intensively remodeled during cancer progression, VDAC1 depletion induced metabolic reprogramming that targeted both tumor cells and resulted in the alteration of the whole spectrum of TME-related genes, affecting the reciprocal feedback between ECM molecules, host cells, and cancer cells. Thus, VDAC1 depletion using si-VDAC1 represents therapeutic potential, inhibiting cancer cell proliferation and also inducing the modulation of TME components, which influences cancer progression, migration, and invasion.

Small interfering RNA (siRNA) to target genes and molecular pathways in glioblastoma therapy: Current status with an emphasis on delivery systems

Glioblastoma multiforme (GBM) is one of the worst brain tumors arising from glial cells, causing many deaths annually. Surgery, chemotherapy, radiotherapy and immunotherapy are used for GBM treatment. However, GBM is still an incurable disease, and new approaches are required for its successful treatment. Because mutations and amplifications occurring in several genes are responsible for the progression and aggressive behavior of GBM cells, genetic approaches are of great importance in its treatment. Small interfering RNA (siRNA) is a new emerging tool to silence the genes responsible for disease progression, particularly cancer. SiRNA can be used for GBM treatment by down-regulating genes such as VEGF, STAT3, ELTD1 or EGFR. Furthermore, the use of siRNA can promote the chemosensitivity of GBM cells. However, the efficiency of siRNA in GBM is limited via its degradation by enzymes, and its off-targeting effects. SiRNA-loaded carriers, especially nanovehicles that are ligand-functionalized by CXCR4 or angiopep-2, can be used for the protection and targeted delivery of siRNA. Nanostructures can provide a platform for co-delivery of siRNA plus anti-tumor drugs as another benefit. The prepared nanovehicles should be stable and biocompatible in order to be tested in human studies.

Mitochondria and nucleus cross-talk: Signaling in metabolism, apoptosis, and differentiation, and function in cancer

The cross-talk between the mitochondrion and the nucleus regulates cellular functions, including differentiation and adaptation to stress. Mitochondria supply metabolites for epigenetic modifications and other nuclear-associated activities and certain mitochondrial proteins were found in the nucleus. The voltage-dependent anion channel 1 (VDAC1), localized at the outer mitochondrial membrane (OMM) is a central protein in controlling energy production, cell growth, Ca2+ homeostasis, and apoptosis. To alter the cross-talk between the mitochondria and the nucleus, we used specific siRNA to silence the expression of VDAC1 in glioblastoma (GBM) U87-MG and U118-MG cell-derived tumors, and then monitored the nuclear localization of mitochondrial proteins and the methylation and acetylation of histones. Depletion of VDAC1 from tumor cells reduced metabolism, leading to inhibition of tumor growth, and several tumor-associated processes and signaling pathways linked to cancer development. In addition, we demonstrate that certain mitochondrial pro-apoptotic proteins such as caspases 3, 8, and 9, and p53 were unexpectedly overexpressed in tumors, suggesting that they possess additional non-apoptotic functions. VDAC1 depletion and metabolic reprograming altered their expression levels and subcellular localization, specifically their translocation to the nucleus. In addition, VDAC1 depletion also leads to epigenetic modifications of histone acetylation and methylation, suggesting that the interchange between metabolism and cancer signaling pathways involves mitochondria-nucleus cross-talk. The mechanisms regulating mitochondrial protein trafficking into and out of the nucleus and the role these proteins play in the nucleus remain to be elucidated.

A Calcium Guard in the Outer Membrane: Is VDAC a Regulated Gatekeeper of Mitochondrial Calcium Uptake?

Already in the early 1960s, researchers noted the potential of mitochondria to take up large amounts of Ca²⁺. However, the physiological role and the molecular identity of the mitochondrial Ca²⁺ uptake mechanisms remained elusive for a long time. The identification of the individual components of the mitochondrial calcium uniporter complex (MCUC) in the inner mitochondrial membrane in 2011 started a new era of research on mitochondrial Ca²⁺ uptake. Today, many studies investigate mitochondrial Ca²⁺ uptake with a strong focus on function, regulation, and localization of the MCUC. However, on its way into mitochondria Ca²⁺ has to pass two membranes, and the first barrier before even reaching the MCUC is the outer mitochondrial membrane (OMM). The common opinion is that the OMM is freely permeable to Ca²⁺. This idea is supported by the presence of a high density of voltage-dependent anion channels (VDACs) in the OMM, forming large Ca²⁺ permeable pores. However, several reports challenge this idea and describe VDAC as a regulated Ca²⁺ channel. In line with this idea is the notion that its Ca²⁺ selectivity depends on the open state of the channel, and its gating behavior can be modified by interaction with partner proteins, metabolites, or small synthetic molecules. Furthermore, mitochondrial Ca²⁺ uptake is controlled by the localization of VDAC through scaffolding proteins, which anchor VDAC to ER/SR calcium release channels. This review will discuss the possibility that VDAC serves as a physiological regulator of mitochondrial Ca²⁺ uptake in the OMM.

Renaissance of VDAC: New Insights on a Protein Family at the Interface between Mitochondria and Cytosol

It has become impossible to review all the existing literature on Voltage-Dependent Anion selective Channel (VDAC) in a single article. A real Renaissance of studies brings this protein to the center of decisive knowledge both for cell physiology and therapeutic application. This review, after highlighting the similarities between the cellular context and the study methods of the solute carriers present in the inner membrane and VDAC in the outer membrane of the mitochondria, will focus on the isoforms of VDAC and their biochemical characteristics. In particular, the possible reasons for their evolutionary onset will be discussed. The variations in their post-translational modifications and the differences between the regulatory regions of their genes, probably the key to understanding the current presence of these genes, will be described. Finally, the situation in the higher eukaryotes will be compared to that of yeast, a unicellular eukaryote, where there is only one active isoform and the role of VDAC in energy metabolism is better understood.

The Two-Way Relationship Between Calcium and Metabolism in Cancer

Calcium ion (Ca²⁺) signaling is critical to many physiological processes, and its kinetics and subcellular localization are tightly regulated in all cell types. All Ca²⁺ flux perturbations impact cell function and may contribute to various diseases, including cancer. Several modulators of Ca²⁺ signaling are attractive pharmacological targets due to their accessibility at the plasma membrane. Despite this, the number of specific inhibitors is still limited, and to date there are no anticancer drugs in the clinic that target Ca²⁺ signaling. Ca²⁺ dynamics are impacted, in part, by modifications of cellular metabolic pathways. Conversely, it is well established that Ca²⁺ regulates cellular bioenergetics by allosterically activating key metabolic enzymes and metabolite shuttles or indirectly by modulating signaling cascades. A coordinated interplay between Ca²⁺ and metabolism is essential in maintaining cellular homeostasis. In this review, we provide a snapshot of the reciprocal interaction between Ca²⁺ and metabolism and discuss the potential consequences of this interplay in cancer cells. We highlight the contribution of Ca²⁺ to the metabolic reprogramming observed in cancer. We also describe how the metabolic adaptation of cancer cells influences this crosstalk to regulate protumorigenic signaling pathways. We suggest that the dual targeting of these processes might provide unprecedented opportunities for anticancer strategies. Interestingly, promising evidence for the synergistic effects of antimetabolites and Ca²⁺-modulating agents is emerging.

VDAC1 at the Intersection of Cell Metabolism, Apoptosis, and Diseases

The voltage-dependent anion channel 1 (VDAC1) protein, is an important regulator of mitochondrial function, and serves as a mitochondrial gatekeeper, with responsibility for cellular fate. In addition to control over energy sources and metabolism, the protein also regulates epigenomic elements and apoptosis via mediating the release of apoptotic proteins from the mitochondria. Apoptotic and pathological conditions, as well as certain viruses, induce cell death by inducing VDAC1 overexpression leading to oligomerization, and the formation of a large channel within the VDAC1 homo-oligomer. This then permits the release of pro-apoptotic proteins from the mitochondria and subsequent apoptosis. Mitochondrial DNA can also be released through this channel, which triggers type-Ι interferon responses. VDAC1 also participates in endoplasmic reticulum (ER)-mitochondria cross-talk, and in the regulation of autophagy, and inflammation. Its location in the outer mitochondrial membrane, makes VDAC1 ideally placed to interact with over 100 proteins, and to orchestrate the interaction of mitochondrial and cellular activities through a number of signaling pathways. Here, we provide insights into the multiple functions of VDAC1 and describe its involvement in several diseases, which demonstrate the potential of this protein as a druggable target in a wide variety of pathologies, including cancer.

Ion Channels and Their Role in the Pathophysiology of Gliomas

Malignant gliomas are the most common primary central nervous system tumors and their prognosis is very poor. In recent years, ion channels have been demonstrated to play important roles in tumor pathophysiology such as regulation of gene expression, cell migration, and cell proliferation. In this review, we summarize the current knowledge on the role of ion channels on the development and progression of gliomas. Cell volume changes through the regulation of ion flux, accompanied by water flux, are essential for migration and invasion. Signaling pathways affected by ion channel activity play roles in cell survival and cell proliferation. Moreover, ion channels are involved in glioma-related seizures, sensitivity to chemotherapy, and tumor metabolism. Ion channels are potential targets for the treatment of these lethal tumors. Despite our increased understanding of the contributions of ion channels to glioma biology, this field remains poorly studied. This review summarizes the current literature on this important topic.

Advances in Therapeutic Targeting of Cancer Stem Cells within the Tumor Microenvironment: An Updated Review

Despite great strides being achieved in improving cancer patients' outcomes through better therapies and combinatorial treatment, several hurdles still remain due to therapy resistance, cancer recurrence and metastasis. Drug resistance culminating in relapse continues to be associated with fatal disease. The cancer stem cell theory posits that tumors are driven by specialized cancer cells called cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells known to be resistant to therapy and cause metastasis. Whilst the debate on whether CSCs are the origins of the primary tumor rages on, CSCs have been further characterized in many cancers with data illustrating that CSCs display great abilities to self-renew, resist therapies due to enhanced epithelial to mesenchymal (EMT) properties, enhanced expression of ATP-binding cassette (ABC) membrane transporters, activation of several survival signaling pathways and increased immune evasion as well as DNA repair mechanisms. CSCs also display great heterogeneity with the consequential lack of specific CSC markers presenting a great challenge to their targeting. In this updated review we revisit CSCs within the tumor microenvironment (TME) and present novel treatment strategies targeting CSCs. These promising strategies include targeting CSCs-specific properties using small molecule inhibitors, immunotherapy, microRNA mediated inhibitors, epigenetic methods as well as targeting CSC niche-microenvironmental factors and differentiation. Lastly, we present recent clinical trials undertaken to try to turn the tide against cancer by targeting CSC-associated drug resistance and metastasis.

Mitochondrial Metabolism in PDAC: From Better Knowledge to New Targeting Strategies

Cancer cells reprogram their metabolism to meet bioenergetics and biosynthetic demands. The first observation of metabolic reprogramming in cancer cells was made a century ago (“Warburg effect” or aerobic glycolysis), leading to the classical view that cancer metabolism relies on a glycolytic phenotype. There is now accumulating evidence that most cancers also rely on mitochondria to satisfy their metabolic needs. Indeed, the current view of cancer metabolism places mitochondria as key actors in all facets of cancer progression. Importantly, mitochondrial metabolism has become a very promising target in cancer therapy, including for refractory cancers such as Pancreatic Ductal AdenoCarcinoma (PDAC). In particular, mitochondrial oxidative phosphorylation (OXPHOS) is an important target in cancer therapy. Other therapeutic strategies include the targeting of glutamine and fatty acids metabolism, as well as the inhibition of the TriCarboxylic Acid (TCA) cycle intermediates. A better knowledge of how pancreatic cancer cells regulate mitochondrial metabolism will allow the identification of metabolic vulnerabilities and thus novel and more efficient therapeutic options for the benefit of each patient.

The Mitochondrial Protein VDAC1 at the Crossroads of Cancer Cell Metabolism: The Epigenetic Link

Carcinogenesis is a complicated process that involves the deregulation of epigenetics, resulting in cellular transformational events, such as proliferation, differentiation, and metastasis. Most chromatin-modifying enzymes utilize metabolites as co-factors or substrates and thus are directly dependent on such metabolites as acetyl-coenzyme A, S-adenosylmethionine, and NAD+. Here, we show that using specific siRNA to deplete a tumor of VDAC1 not only led to reprograming of the cancer cell metabolism but also altered several epigenetic-related enzymes and factors. VDAC1, in the outer mitochondrial membrane, controls metabolic cross-talk between the mitochondria and the rest of the cell, thus regulating the metabolic and energetic functions of mitochondria, and has been implicated in apoptotic-relevant events. We previously demonstrated that silencing VDAC1 expression in glioblastoma (GBM) U-87MG cell-derived tumors, resulted in reprogramed metabolism leading to inhibited tumor growth, angiogenesis, epithelial-mesenchymal transition and invasiveness, and elimination of cancer stem cells, while promoting the differentiation of residual tumor cells into neuronal-like cells. These VDAC1 depletion-mediated effects involved alterations in transcription factors regulating signaling pathways associated with cancer hallmarks. As the epigenome is sensitive to cellular metabolism, this study was designed to assess whether depleting VDAC1 affects the metabolism-epigenetics axis. Using DNA microarrays, q-PCR, and specific antibodies, we analyzed the effects of si-VDAC1 treatment of U-87MG-derived tumors on histone modifications and epigenetic-related enzyme expression levels, as well as the methylation and acetylation state, to uncover any alterations in epigenetic properties. Our results demonstrate that metabolic rewiring of GBM via VDAC1 depletion affects epigenetic modifications, and strongly support the presence of an interplay between metabolism and epigenetics.

RNA-based pharmacotherapy for tumors: From bench to clinic and back

RNA therapy is a treatment that regulates cell proteins and cures diseases by affecting the metabolism of mRNAs in cells, which has cut a figure in the studies on various incurable illnesses like hereditary diseases, tumors, etc. In this review, we introduced the discovery and development of RNA therapy and discussed its classification, mechanisms, advantages, and challenges. Moreover, we highlighted how RNA therapy works in killing tumor cells as well as what progresses it has made in related researches. And the development of RNA anti-tumor drugs and the clinical trial process were also included.

From old to new - Repurposing drugs to target mitochondrial energy metabolism in cancer

Although we have entered the era of personalized medicine and tailored therapies, drugs that target a large variety of cancers regardless of individual patient differences would be a major advance nonetheless. This review article summarizes current concepts and therapeutic opportunities in the area of targeting aerobic mitochondrial energy metabolism in cancer. Old drugs previously used for diseases other than cancer, such as antibiotics and antidiabetics, have the potential to inhibit the growth of various tumor entities. Many drugs are reported to influence mitochondrial metabolism. However, here we consider only those drugs which predominantly inhibit oxidative phosphorylation.

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.

PMEPA1 isoform a drives progression of glioblastoma by promoting protein degradation of the Hippo pathway kinase LATS1

The Hippo signaling pathway controls organ development and is also known, in cancer, to have a tumor suppressing role. Within the Hippo pathway, we here demonstrate, in human gliomas, a functional interaction of a transmembrane protein, prostate transmembrane protein, androgen induced 1 (PMEPA1) with large tumor suppressor kinase 1 (LATS1). We show that PMEPA1 is upregulated in primary human gliomas. The PMEPA1 isoform PMEPA1a was predominantly expressed in glioma specimens and cell lines, and ectopic expression of the protein promoted glioma growth and invasion in vitro and in an orthotopic xenograft model in nude mice. In co-immunoprecipitation experiments, PMEPA1a associated with the Hippo tumor suppressor kinase LATS1. This interaction led to a proteasomal degradation of LATS1 through recruitment of the ubiquitin ligase, neural precursor cell expressed, developmentally downregulated 4 (NEDD4), which led to silencing of Hippo signaling. Alanine substitution in PMEPA1a at PY motifs resulted in failed LATS1 degradation. Targeting of a downstream component in the Hippo signaling pathway, YAP, with shRNA, interfered with the growth promoting activities of PMEPA1a in vitro and in vivo. In conclusion, the presented work shows that PMEPA1a contributes to glioma progression by a dysregulation of the Hippo signaling pathway and thus represents a promising target for the treatment of gliomas.

Prognostic implications of metabolism-associated gene signatures in colorectal cancer

Colorectal cancer (CRC) is one of the most common and deadly malignancies. Novel biomarkers for the diagnosis and prognosis of this disease must be identified. Besides, metabolism plays an essential role in the occurrence and development of CRC. This article aims to identify some critical prognosis-related metabolic genes (PRMGs) and construct a prognosis model of CRC patients for clinical use. We obtained the expression profiles of CRC from The Cancer Genome Atlas database (TCGA), then identified differentially expressed PRMGs by R and Perl software. Hub genes were filtered out by univariate Cox analysis and least absolute shrinkage and selection operator Cox analysis. We used functional enrichment analysis methods, such as Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis, to identify involved signaling pathways of PRMGs. The nomogram predicted overall survival (OS). Calibration traces were used to evaluate the consistency between the actual and the predicted survival rate. Finally, a prognostic model was constructed based on six metabolic genes (NAT2, XDH, GPX3, AKR1C4, SPHK1, and ADCY5), and the risk score was an independent prognostic prognosticator. Genetic expression and risk score were significantly correlated with clinicopathologic characteristics of CRC. A nomogram based on the clinicopathological feature of CRC and risk score accurately predicted the OS of individual CRC cancer patients. We also validated the results in the independent colorectal cancer cohorts GSE39582 and GSE87211. Our study demonstrates that the risk score is an independent prognostic biomarker and is closely correlated with the malignant clinicopathological characteristics of CRC patients. We also determined some metabolic genes associated with the survival and clinical stage of CRC as potential biomarkers for CRC diagnosis and treatment.

The Metabolic Landscape of Lung Cancer: New Insights in a Disturbed Glucose Metabolism

Metabolism encompasses the biochemical processes that allow healthy cells to keep energy, redox balance and building blocks required for cell development, survival, and proliferation steady. Malignant cells are well-documented to reprogram their metabolism and energy production networks to support rapid proliferation and survival in harsh conditions via mutations in oncogenes and inactivation of tumor suppressor genes. Despite the histologic and genetic heterogeneity of tumors, a common set of metabolic pathways sustain the high proliferation rates observed in cancer cells. This review with a focus on lung cancer covers several fundamental principles of the disturbed glucose metabolism, such as the “Warburg” effect, the importance of the glycolysis and its branching pathways, the unanticipated gluconeogenesis and mitochondrial metabolism. Furthermore, we highlight our current understanding of the disturbed glucose metabolism and how this might result in the development of new treatments.

Rewiring of Cancer Cell Metabolism by Mitochondrial VDAC1 Depletion Results in Time-Dependent Tumor Reprogramming: Glioblastoma as a Proof of Concept

Reprograming of the metabolism of cancer cells is an event recognized as a hallmark of the disease. The mitochondrial gatekeeper, voltage-dependent anion channel 1 (VDAC1), mediates transport of metabolites and ions in and out of mitochondria, and is involved in mitochondria-mediated apoptosis. Here, we compared the effects of reducing hVDAC1 expression in a glioblastoma xenograft using human-specific si-RNA (si-hVDAC1) for a short (19 days) and a long term (40 days). Tumors underwent reprograming, reflected in rewired metabolism, eradication of cancer stem cells (CSCs) and differentiation. Short- and long-term treatments of the tumors with si-hVDAC1 similarly reduced the expression of metabolism-related enzymes, and translocator protein (TSPO) and CSCs markers. In contrast, differentiation into cells expressing astrocyte or neuronal markers was noted only after a long period during which the tumor cells were hVDAC1-depleted. This suggests that tumor cell differentiation is a prolonged process that precedes metabolic reprograming and the “disappearance” of CSCs. Tumor proteomics analysis revealing global changes in the expression levels of proteins associated with signaling, synthesis and degradation of proteins, DNA structure and replication and epigenetic changes, all of which were highly altered after a long period of si-hVDAC1 tumor treatment. The depletion of hVDAC1 greatly reduced the levels of the multifunctional translocator protein TSPO, which is overexpressed in both the mitochondria and the nucleus of the tumor. The results thus show that VDAC1 depletion-mediated cancer cell metabolic reprograming involves a chain of events occurring in a sequential manner leading to a reversal of the unique properties of the tumor, indicative of the interplay between metabolism and oncogenic signaling networks.

Metabolic implications of organelle-mitochondria communication

Cellular organelles are not static but show dynamism-a property that is likely relevant for their function. In addition, they interact with other organelles in a highly dynamic manner. In this review, we analyze the proteins involved in the interaction between mitochondria and other cellular organelles, especially the endoplasmic reticulum, lipid droplets, and lysosomes. Recent results indicate that, on one hand, metabolic alterations perturb the interaction between mitochondria and other organelles, and, on the other hand, that deficiency in proteins involved in the tethering between mitochondria and the ER or in specific functions of the interaction leads to metabolic alterations in a variety of tissues. The interaction between organelles is an emerging field that will permit to identify key proteins, to delineate novel modulation pathways, and to elucidate their implications in human disease.

Metabolic Reprograming Via Silencing of Mitochondrial VDAC1 Expression Encourages Differentiation of Cancer Cells

The mitochondrial gatekeeper voltage-dependent anion channel 1 (VDAC1) controls metabolic and energy cross-talk between mitochondria and the rest of the cell and is involved in mitochondria-mediated apoptosis. Here, we compared the effects of downregulated VDAC1 expression in the U-87MG glioblastoma, MDA-MB-231 triple-negative breast cancer (TNBC), and A549 lung cancer cell lines, using small interfering RNA (siRNA) specific to human VDAC1 (si-hVDAC1). The cells were subjected to si-hVDAC1 (50 nM) treatment for 5–20 days. Although VDAC1 silencing occurred within a day, the cells underwent reprograming with respect to rewiring metabolism, elimination of cancer stem cells (CSCs), and alteration of transcription factor (TF) expression and proteins associated with differentiation, with maximal changes being observed after 3 weeks of silencing VDAC1 expression. The differentiation into fewer tumorigenic cells may be associated with the elimination of CSCs. These alterations are interconnected, as protein up- or downregulation occurred simultaneously, starting 15–20 days after VDAC1 levels were first decreased. Moreover, the VDAC1 depletion-mediated effects on a network of key regulators of cell metabolism, CSCs, TFs, and other factors leading to differentiation are coordinated and are common to the glioblastoma multiforme (GBM) and lung and breast cancer cell lines, despite differing in origin and carried mutations. Thus, our study showed that VDAC1 depletion triggers reprograming of malignant cancer cells into terminally differentiated cells and that this may be a promising therapeutic approach for various cancers.

Development of a patient-derived xenograft model of glioblastoma via intravitreal injection in mice

Currently, the two primary patient-derived xenograft (PDX) models of glioblastoma are established through intracranial or subcutaneous injection. In this study, a novel PDX model of glioblastoma was developed via intravitreal injection to facilitate tumor formation in a brain-mimicking microenvironment with improved visibility and fast development. Glioblastoma cells were prepared from the primary and recurrent tumor tissues of a 39-year-old female patient. To demonstrate the feasibility of intracranial tumor formation, U-87 MG and patient-derived glioblastoma cells were injected into the brain parenchyma of Balb/c nude mice. Unlike the U-87 MG cells, the patient-derived glioblastoma cells failed to form intracranial tumors until 6 weeks after tumor cell injection. In contrast, the patient-derived cells effectively formed intraocular tumors, progressing from plaques at 2 weeks to masses at 4 weeks after intravitreal injection. The in vivo tumors exhibited the same immunopositivity for human mitochondria, GFAP, vimentin, and nestin as the original tumors in the patient. Furthermore, cells isolated from the in vivo tumors also demonstrated morphology similar to that of their parental cells and immunopositivity for the same markers. Overall, a novel PDX model of glioblastoma was established via the intravitreal injection of tumor cells. This model will be an essential tool to investigate and develop novel therapeutic alternatives for the treatment of glioblastoma.

An improved strategy for cultivating patient-derived tumors in mice gives researchers a faster, more accurate means for testing glioblastoma treatments. Such ‘xenograft’ models are powerful tools for characterizing a patient’s cancer, but current cultivation techniques are too slow or fail to capture key features of this deadly disease. Researchers led by Jeong Hun Kim and Sun Ha Paek at Seoul National University Hospital in South Korea have demonstrated that glioblastoma cells injected into the mouse eye produce growths that mirror key characteristics of the original tumor. The tissue environment of the retina is physiologically similar to that of the brain, and cancer cells injected into the eye form glioblastoma-like tumors twice as quickly as the same cells injected into the skull. This means clinical researchers can assess drug response and accordingly adjust patient care more quickly.

Antimicrobial Peptide TP4 Induces ROS-Mediated Necrosis by Triggering Mitochondrial Dysfunction in Wild-Type and Mutant p53 Glioblastoma Cells

Antimicrobial peptide tilapia piscidin 4 (TP4) from Oreochromis niloticus exhibits potent bactericidal and anti-tumorigenic effects. In a variety of cancers, the mutation status of p53 is a decisive factor for therapeutic sensitivity. Therefore, we investigated the impact of p53 status on TP4-induced cytotoxicity in glioblastoma cell lines and the molecular mechanisms that govern cytotoxic effects. Both U87MG (wild-type/WT p53) and U251 (mutant p53) glioblastoma cell lines were sensitive to TP4-induced cytotoxicity. The necrosis inhibitors Necrostatin-1 and GSK’872 attenuated TP4-induced cytotoxicity, and TP4 treatment induced the release of cyclophilin A, a biomarker of necrosis. Moreover, TP4 induced mitochondrial hyperpolarization and dysfunction, which preceded the elevation of intracellular reactive oxygen species, DNA damage, and necrotic cell death in both U87MG and U251 glioblastoma cells. p38 was also activated by TP4, but did not contribute to cytotoxicity. SB202190, a specific p38 inhibitor, enhanced TP4-induced oxidative stress, mitochondrial dysfunction, and cytotoxicity, suggesting a protective role of p38. Furthermore, TP4-induced cytotoxicity, oxidative stress, phosphorylation of p38, and DNA damage were all attenuated by the mitochondrial-targeted reactive oxygen species (ROS) scavenger MitoTEMPO, or the reactive oxygen species scavenger N-acetyl-L-cysteine. Based on these data, we conclude that TP4 induces necrosis in both WT and mutant p53 glioblastoma cells through a mitochondrial ROS-dependent pathway.

Mitochondrial VDAC1 Silencing Leads to Metabolic Rewiring and the Reprogramming of Tumour Cells into Advanced Differentiated States

Oncogenic properties, along with the metabolic reprogramming necessary for tumour growth and motility, are acquired by cancer cells. Thus, tumour metabolism is becoming a target for cancer therapy. Here, cancer cell metabolism was tackled by silencing the expression of voltage-dependent anion channel 1 (VDAC1), a mitochondrial protein that controls cell energy, as well as metabolic and survival pathways and that is often over-expressed in many cancers. We demonstrated that silencing VDAC1 expression using human-specific siRNA (si-hVDAC1) inhibited cancer cell growth, both in vitro and in mouse xenograft models of human glioblastoma (U-87MG), lung cancer (A549), and triple negative breast cancer (MDA-MB-231). Importantly, treatment with si-hVDAC1 induced metabolic rewiring of the cancer cells, reversing their oncogenic properties and diverting them towards differentiated-like cells. The si-hVDAC1-treated residual “tumour” showed reprogrammed metabolism, decreased proliferation, inhibited stemness and altered expression of genes and proteins, leading to cell differentiation toward less malignant lineages. These VDAC1 depletion-mediated effects involved alterations in master transcription factors associated with cancer hallmarks, such as highly increased expression of p53 and decreased expression of HIF-1a and c-Myc that regulate signalling pathways (e.g., AMPK, mTOR). High expression of p53 and the pro-apoptotic proteins cytochrome c and caspases without induction of apoptosis points to functions for these proteins in promoting cell differentiation. These results clearly show that VDAC1 depletion similarly leads to a rewiring of cancer cell metabolism in breast and lung cancer and glioblastoma, regardless of origin or mutational status. This metabolic reprogramming results in cell growth arrest and inhibited tumour growth while encouraging cell differentiation, thus generating cells with decreased proliferation capacity. These results further suggest VDAC1 to be an innovative and markedly potent therapeutic target.

Sulindac sulfone inhibits the mTORC1 pathway in colon cancer cells by directly targeting voltage-dependent anion channel 1 and 2

Sulindac sulfone is a metabolite of sulindac, a non-steroidal anti-inflammatory drug (NSAID), without anti-inflammatory ability. However, sulindac sulfone has been reported to significantly reduce polyps in patients with colorectal adenomatous polyposis in clinical trials. Thus, sulindac sulfone is expected to be useful for the chemoprevention of neoplasia with few side effects related to anti-inflammatory ability. To date, the molecular targets of sulindac sulfone have not yet fully investigated. Therefore, in order to newly identify sulindac sulfone-binding proteins, we generated sulindac sulfone-fixed FG beads and purified sulindac sulfone-binding proteins from human colon cancer HT-29 cells. we identified mitochondrial outer membrane proteins voltage-dependent anion channel (VDAC) 1 and VDAC2 as novel molecular targets of sulindac sulfone, and sulindac sulfone directly bound to both VDAC1 and VDAC2. Double knockdown of VDAC1 and VDAC2 by siRNA inhibited growth and arrested the cell cycle at G1 phase in HT-29 cells. Depletion of VDAC1 and VDAC2 also inhibited the mTORC1 pathway with a reduction in cyclin D1. Interestingly, these effects were consistent with those of sulindac sulfone against human colon cancer cells, suggesting that sulindac sulfone negatively regulates the function of VDAC1 and VDAC2. In the present study, our data suggested that VDAC1 and VDAC2 are direct targets of sulindac sulfone which suppresses the mTORC1 pathway and induces G1 arrest.

Traumatic glioblastoma: commentary and suggested mechanism

The role of head trauma in the development of glioblastoma is highly controversial and has been minimized since first put forward. This is not unexpected because skull injuries are overwhelmingly more common than glioblastoma. This paper presents a commentary based on the contributions of James Ewing, who established a major set of criteria for the recognition of an official relationship between trauma and cancer. Ewing's criteria were very stringent. The scholars who succeeded Ewing have facilitated the characterization of traumatic brain injuries since the introduction of computed tomography and magnetic resonance imaging. Discussions of the various criteria that have since developed are now being conducted, and those of an unnecessarily limiting nature are being highlighted. Three transcription factors associated with traumatic brain injury have been identified: p53, hypoxia-inducible factor-1α, and c-MYC. A role for these three transcription factors in the relationship between traumatic brain injury and glioblastoma is suggested; this role may support a cause-and-effect link with the subsequent development of glioblastoma.

Selective induction of cancer cell death by VDAC1-based peptides and their potential use in cancer therapy

Mitochondrial VDAC1 mediates cross talk between the mitochondria and other parts of the cell by transporting anions, cations, ATP, Ca²⁺, and metabolites and serves as a key player in apoptosis. As such, VDAC1 is involved in two important hallmarks of cancer development, namely energy and metabolic reprograming and apoptotic cell death evasion. We previously developed cell‐penetrating VDAC1‐derived peptides that interact with hexokinase (HK), Bcl‐2, and Bcl‐xL to prevent the anti‐apoptotic activities of these proteins and induce cancer cell death, with a focus on leukemia and glioblastoma. In this study, we demonstrated the sensitivity of a panel of genetically characterized cancer cell lines, differing in origin and carried mutations, to VDAC1‐based peptide‐induced apoptosis. Noncancerous cell lines were less affected by the peptides. Furthermore, we constructed additional VDAC1‐based peptides with the aim of improving targeting, selectivity, and cellular stability, including R‐Tf‐D‐LP4, containing the transferrin receptor internalization sequence (Tf) that allows targeting of the peptide to cancer cells, known to overexpress the transferrin receptor. The mode of action of the VDAC1‐based peptides involves HK detachment, interfering with the action of anti‐apoptotic proteins, and thus activating multiple routes leading to an impairment of cell energy and metabolism homeostasis and the induction of apoptosis. Finally, in xenograft glioblastoma, lung, and breast cancer mouse models, R‐Tf‐D‐LP4 inhibited tumor growth while inducing massive cancer cell death, including of cancer stem cells. Thus, VDAC1‐based peptides offer an innovative new conceptual framework for cancer therapy.

Metabolism and Transcription in Cancer: Merging Two Classic Tales

Cellular plasticity, or the ability of a cancer cell to adapt to changes in the microenvironment, is a major determinant of cell survival and functionality that require the coordination of transcriptional programs with signaling and metabolic pathways. In this scenario, these pathways sense and integrate nutrient signals for the induction of coordinated gene expression programs in cancer. This minireview focuses on recent advances that shed light on the bidirectional relationship between metabolism and gene transcription, and their biological outcomes in cancer. Specifically, we will discuss how metabolic changes occurring in cancer cells impact on gene expression, both at the level of the epigenetic landscape and transcription factor regulation.

VDAC1 at the crossroads of cell metabolism, apoptosis and cell stress

This review presents current knowledge related to VDAC1 as a multi-functional mitochondrial protein acting on both sides of the coin, regulating cell life and death, and highlighting these functions in relation to disease. It is now recognized that VDAC1 plays a crucial role in regulating the metabolic and energetic functions of mitochondria. The location of VDAC1 at the outer mitochondrial membrane (OMM) allows the control of metabolic cross-talk between mitochondria and the rest of the cell and also enables interaction of VDAC1 with proteins involved in metabolic and survival pathways. Along with regulating cellular energy production and metabolism, VDAC1 is also involved in the process of mitochondria-mediated apoptosis by mediating the release of apoptotic proteins and interacting with anti-apoptotic proteins. VDAC1 functions in the release of apoptotic proteins located in the mitochondrial intermembrane space via oligomerization to form a large channel that allows passage of cytochrome c and AIF and their release to the cytosol, subsequently resulting in apoptotic cell death. VDAC1 also regulates apoptosis via interactions with apoptosis regulatory proteins, such as hexokinase, Bcl2 and Bcl-xL, some of which are also highly expressed in many cancers. This review also provides insight into VDAC1 function in Ca²⁺ homeostasis, oxidative stress, and presents VDAC1 as a hub protein interacting with over 100 proteins. Such interactions enable VDAC1 to mediate and regulate the integration of mitochondrial functions with cellular activities. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target.

Voltage-Dependent Anion Channel 1 As an Emerging Drug Target for Novel Anti-Cancer Therapeutics

Cancer cells share several properties, high proliferation potential, reprogramed metabolism, and resistance to apoptotic cues. Acquiring these hallmarks involves changes in key oncogenes and non-oncogenes essential for cancer cell survival and prosperity, and is accompanied by the increased energy requirements of proliferating cells. Mitochondria occupy a central position in cell life and death with mitochondrial bioenergetics, biosynthesis, and signaling are critical for tumorigenesis. Voltage-dependent anion channel 1 (VDAC1) is situated in the outer mitochondrial membrane (OMM) and serving as a mitochondrial gatekeeper. VDAC1 allowing the transfer of metabolites, fatty acid ions, Ca²⁺, reactive oxygen species, and cholesterol across the OMM and is a key player in mitochondrial-mediate apoptosis. Moreover, VDAC1 serves as a hub protein, interacting with diverse sets of proteins from the cytosol, endoplasmic reticulum, and mitochondria that together regulate metabolic and signaling pathways. The observation that VDAC1 is over-expressed in many cancers suggests that the protein may play a pivotal role in cancer cell survival. However, VDAC1 is also important in mitochondria-mediated apoptosis, mediating release of apoptotic proteins and interacting with anti-apoptotic proteins, such as B-cell lymphoma 2 (Bcl-2), Bcl-xL, and hexokinase (HK), which are also highly expressed in many cancers. Strategically located in a “bottleneck” position, controlling metabolic homeostasis and apoptosis, VDAC1 thus represents an emerging target for anti-cancer drugs. This review presents an overview on the multi-functional mitochondrial protein VDAC1 performing several functions and interacting with distinct sets of partners to regulate both cell life and death, and highlights the importance of the protein for cancer cell survival. We address recent results related to the mechanisms of VDAC1-mediated apoptosis and the potential of associated proteins to modulate of VDAC1 activity, with the aim of developing VDAC1-based approaches. The first strategy involves modification of cell metabolism using VDAC1-specific small interfering RNA leading to inhibition of cancer cell and tumor growth and reversed oncogenic properties. The second strategy involves activation of cancer cell death using VDAC1-based peptides that prevent cell death induction by anti-apoptotic proteins. Finally, we discuss the potential therapeutic benefits of treatments and drugs leading to enhanced VDAC1 expression or targeting VDAC1 to induce apoptosis.