Cl- and K+ channels and their role in primary brain tumour biology

Targeting Ion Channels: Blockers Suppress Calcium Signals and Induce Cytotoxicity Across Medulloblastoma Cell Models

Medulloblastoma (MB) groups 3 and 4 lack targeted therapies despite their dismal prognoses. Ion channels and pumps have been implicated in promoting MB metastasis and growth; however, their roles remain poorly understood. In this study, we repurposed FDA-approved channel blockers and modulators to investigate their potential anti-tumor effects in MB cell lines (DAOY and D283) and primary cell cultures derived from a patient with MB. For the first time, we report spontaneous calcium signaling in MB cells. Spontaneous calcium signals were significantly reduced by mibefradil (calcium channel blocker), paxilline (calcium-activated potassium channel blocker), and thioridazine (potassium channel blocker). These drugs induced dose-dependent cytotoxicity in both the DAOY and D283 cell lines, as well as in primary cell cultures of a patient with group 3 or 4 MB. In contrast, digoxin and ouabain, inhibitors of the Na/K pump, reduced the calcium signaling by over 90% in DAOY cells and induced approximately 90% cell death in DAOY cells and 80% cell death in D283 cells. However, these effects were significantly diminished in the cells derived from a patient with MB, highlighting the variability in drug sensitivity among MB models. These findings demonstrate that calcium signaling is critical for MB cell survival and that the targeted inhibition of calcium pathways suppresses tumor cell growth across multiple MB models.

SLC12A9 is an immunological and prognostic biomarker for glioma

BACKGROUND

Glioma is one of the most common malignant brain tumors. It has a high rate of progression and a poor prognosis, and effective biomarkers still need to be identified. The solute carrier family 12 (SLC12) family has been reported to be involved in various physiological and pathological processes, but their functional roles in glioma remain unclear.

METHODS

Using public datasets, we studied the mutation and expression level of SLC12 family genes in glioma and identified the significantly differentially expressed member solute carrier family 12 member 9 (SLC12A9). We further predicted the prognostic role of SLC12A9 in glioma by using the Kaplan-Meier method and Cox regression analysis. Then, we performed biological functional enrichment analysis. We focused on the relationships between SLC12A9 expression and immune infiltration in glioma. Meanwhile, we conducted in vitro experiments to evaluate the effect of SLC12A9 expression on glioma cells.

RESULTS

Among the members of the SLC12 family, SLC12A9 had the highest mutation rate in glioma, with gene amplification as the major mutation type, and its expression was significantly upregulated in glioma. Higher SLC12A9 expression was significantly associated with older age, higher grade, wild-type isocitrate dehydrogenase (IDH), and a worse prognosis. The functional enrichment analysis indicated that SLC12A9 is mainly related to ion channel annotation. Gene set enrichment analysis (GSEA) revealed that SLC12A9 was mainly related to the DNA replication pathway. Furthermore, we found that SLC12A9 correlated with tumor-infiltrating immune cells and immune checkpoints. Thus, SLC12A9 may be involved in regulating the immune response of glioma. Finally, our in vitro experiments revealed that silencing SLC12A9 dramatically inhibited glioma cell growth and migration.

CONCLUSIONS

We showed that SLC12A9 may be a new predictive biomarker for glioma diagnosis, prognosis, and immunotherapy response, offering helpful guidelines to advance glioma treatment.

LRRC8A-containing anion channels promote glioblastoma proliferation via a WNK1/mTORC2-dependent mechanism

Leucine-rich repeat-containing protein 8A (LRRC8A) is the essential subunit of ubiquitous volume-regulated anion channels (VRACs). LRCC8A is overexpressed in several cancers and promotes negative survival outcomes via a poorly defined mechanism. Here, we explored the role of LRRC8A and VRACs in the progression of glioblastoma (GBM), the most common and deadly primary brain tumor. We found that, as compared to healthy controls, LRRC8A mRNA was strongly upregulated in surgical GBM specimens, patient-derived GBM cell lines, and GBM datasets from The Cancer Genome Atlas (TCGA). Our in-silico analysis indicated that patients belonging to the lowest LRRC8A expression quartile demonstrated a trend for extended life expectancy. In patient-derived GBM cultures, siRNA-driven LRRC8A knockdown reduced cell proliferation and additionally decreased intracellular chloride levels and inhibited activity of mTOR complex 2. The antiproliferative effect of LRRC8A downregulation was recapitulated with a pharmacological inhibitor of VRAC. Our ensuing biochemical and molecular biology analyses established that the LRRC8A-containing VRACs facilitate GBM proliferation via a new mechanism involving non-enzymatic actions of the chloride-sensitive protein kinase WNK1. Accordingly, the chloride-bound WNK1 stimulates mTORC2 and the mTORC2-dependent protein kinases AKT and SGK, which promote proliferation. These findings establish the new mTORC2-centric axis for VRAC dependent regulation of cellular functions and uncover potential targets for GBM intervention.

Cancer neuroscience and glioma: clinical implications

In recent years, it has been increasingly recognized that tumor growth relies not only on support from the surrounding microenvironment but also on the tumors capacity to adapt to - and actively manipulate - its niche. While targeting angiogenesis and modulating the local immune environment have been explored as therapeutic approaches, these strategies have yet to yield effective treatments for brain tumors and remain under refinement. More recently, the nervous system itself has been explored as a critical environmental support for cancer, with extensive neuro-tumoral interactions observed both intracranially and in extracranial sites containing neural components. In the brain, interactions between glioma cells as well as metastatic lesions with neural components have clinical implications for diagnostics, risk assessments, neurological sequelae, and the development of innovative therapeutics. Here, we review these neuro-tumoral dynamics, emphasizing aspects relevant to neurosurgical practice.

Gene choice in cancer cells is exclusive in ion transport but concurrent in DNA replication

Cancers share common cellular and physiological features. Little is known about whether distinctive gene expression patterns can be displayed at the single-cell level by gene families in cancer cells. The expression of gene homologs within a family can exhibit concurrence and exclusivity. Concurrence can promote all-or-none expression patterns of related genes and underlie alternative physiological states. Conversely, exclusive gene families express the same or similar number of homologs in each cell, allowing a broad repertoire of cell identities to be generated. We show that gene families involved in the cell-cycle and antigen presentation are expressed concurrently. Concurrence in the DNA replication complex MCM reflects the replicative status of cells, including cell lines and cancer-derived organoids. Exclusive expression requires precise regulatory mechanism, but cancer cells retain this form of control for ion homeostasis and extend it to gene families involved in cell migration. Thus, the cell adhesion-based identity of healthy cells is transformed to an identity based on migration in the population of cancer cells, reminiscent of epithelial-mesenchymal transition.

Sphaeropsidin A C15-C16 Cross-Metathesis Analogues with Potent Anticancer Activity

We recently discovered that sphaeropsidin A (SphA), a fungal metabolite from Diplodia cupressi, overcomes apoptosis resistance in cancer cells by inducing cellular shrinkage by impairing regulatory volume increase. Previously, we prepared a pyrene-conjugated derivative of SphA by a cross-metathesis reaction involving the phytotoxin's C15,C16-alkene. This derivative's evaluation in a cancer cell panel revealed a significant increase in potency, with the IC50 values 5-10× lower than those displayed by the original natural product. Herein, we describe the preparation and anticancer evaluation of fifteen novel C15,C16-alkene cross-metathesis analogues in which the pyrene moiety was replaced with other aromatic or non-aromatic hydrophobic groups. The idea for this replacement was to prepare a family of compounds that would not be predicted to be mutagenic compared with the original pyrene analogue. We predict several of our new compounds to be non-mutagenic, while retaining the high potency of the original pyrene-containing analogues. Examples of these potential lead compounds included those containing pentamethylphenyl and triphenylethylene pendant groups. As an additional feature of the current investigation, we prepared several deuterated pyrene-containing compounds to overcome intellectual property issues associated with non-patentability of the original pyrene derivative.

Mechanisms of Glioblastoma Replication: Ca2+ Flares and Cl- Currents

Glioblastoma (GBM) is amongst the deadliest types of cancers, with no resolutive cure currently available. GBM cell proliferation in the patient's brain is a complex phenomenon controlled by multiple mechanisms. The aim of this study was to determine whether the ionic fluxes controlling cell duplication could represent a target for GBM therapy. In this work, we combined multi-channel Ca2+ and Cl- imaging, optical tweezers, electrophysiology, and immunohistochemistry to describe the role of ion fluxes in mediating the cell volume changes that accompany mitosis of U87 GBM cells. We identified three main steps: (i) in round GBM cells undergoing mitosis, during the transition from anaphase to telophase and cytokinesis, large Ca2+ flares occur, reaching values of 0.5 to 1 μmol/L; (ii) these Ca2+ flares activate Ca2+-dependent Cl- channels, allowing the entry of Cl- ions; and (iii) to maintain osmotic balance, GBM cells swell to complete mitosis. This sequence of steps was validated by electrophysiological experiments showing that Cl- channels are activated either directly or indirectly by Ca2+, and by additional live-cell imaging experiments. Cl- channel blockers with different molecular structures, such as niflumic acid and carbenoxolone, blocked GBM replication by arresting GBM cells in a round configuration. These results describe the central role of Ca2+ flares and Cl- fluxes during mitosis and show that inhibition of Ca2+-activated Cl- channels blocks GBM replication, opening the way to new approaches for the clinical treatment of GBM. Implications: Our work identifies ionic fluxes occurring during cell division as targets for devising novel therapies for glioblastoma treatment.

DNA Methylation in Recurrent Glioblastomas: Increased TEM8 Expression Activates the Src/PI3K/AKT/GSK-3β/B-Catenin Pathway

BACKGROUND/AIM

Glioblastomas (GBM) are infiltrative malignant brain tumors which mostly recur within a year's time following surgical resection and chemo-radiation therapy. Studies on glioblastoma cells following radio-chemotherapy, have been demonstrated to induce trans-differentiation, cellular plasticity, activation of DNA damage response and stemness. As glioblastomas are heterogenous tumors that develop treatment resistance and plasticity, we investigated if there exist genome-wide DNA methylation changes in recurrent tumors.

MATERIALS AND METHODS

Utilizing genome-wide DNA methylation arrays, we compared the DNA methylation profile of 11 primary (first occurrence) tumors with 13 recurrent (relapsed) GBM, to delineate the contribution of epigenetic changes associated with therapy exposure, therapy resistance, and relapse of disease.

RESULTS

Our data revealed 1,224 hypermethylated- and 526 hypomethylated-probes in recurrent glioblastomas compared to primary disease. We found differential methylation of solute carrier and ion channel genes, interleukin receptor/ligand genes, tumor-suppressor genes and genes associated with metastasis. We functionally characterized one such hypomethylated-up-regulated gene, namely anthrax toxin receptor 1/tumor endothelial marker 8 (ANTXR1/TEM8), whose expression was validated to be significantly up-regulated in recurrent glioblastomas compared to primary tumors and confirmed by immunohistochemistry. Using overexpression and knockdown approaches, we showed that TEM8 induces proliferation, invasion, migration, and chemo-radioresistance in glioblastoma cells. Additionally, we demonstrated a novel mechanism of β-catenin stabilization and activation of the β-catenin transcriptional program due to TEM8 overexpression via a Src/PI3K/AKT/GSK3β/β-catenin pathway.

CONCLUSION

We report genome-wide DNA methylation changes in recurrent GBM and suggest involvement of the TEM8 gene in GBM recurrence and progression.

Neurosteroids in Glioma: A Novel Therapeutic Concept

Glioma, a diverse group of brain and spinal cord tumors arising from glial cells, is characterized by varying degrees of malignancy, with some types exhibiting highly aggressive behavior, rapid proliferation, and invasive growth patterns, posing significant therapeutic challenges. This review delves into the complex interactions between glioma cells, neurotransmitters, and neurosteroids, emphasizing their potential as therapeutic targets. Key neurotransmitters, like glutamate and gamma-aminobutyric acid (GABA), play crucial roles in glioma growth, invasion, and treatment response. This review examines the involvement of neurosteroids in glioma biology and explores innovative therapeutic strategies targeting these systems. It encompasses the biosynthesis and mechanisms of neurosteroids, interactions between gliomas and neurotransmitters, the spatial distribution of neurosteroid synthesis in gliomas, the role of ion channels, hormonal influences, enzyme modulation, and the neuroimmune system in glioma progression. Additionally, it highlights the potential of neurosteroids to modulate these pathways for therapeutic benefit.

Differential Impact of Valproic Acid on SLC5A8, SLC12A2, SLC12A5, CDH1, and CDH2 Expression in Adult Glioblastoma Cells

Valproic acid (VPA) has anticancer, anti-inflammatory, and epigenetic effects. The study aimed to determine the expression of carcinogenesis-related SLC5A8, SLC12A2, SLC12A5, CDH1, and CDH2 in adult glioblastoma U87 MG and T98G cells and the effects of 0.5 mM, 0.75 mM, and 1.5 mM doses of VPA. RNA gene expression was determined by RT-PCR. GAPDH was used as a control. U87 and T98G control cells do not express SLC5A8 or CDH1. SLC12A5 was expressed in U87 control but not in T98G control cells. The SLC12A2 expression in the U87 control was significantly lower than in the T98G control. T98G control cells showed significantly higher CDH2 expression than U87 control cells. VPA treatment did not affect SLC12A2 expression in U87 cells, whereas treatment dose-dependently increased SLC12A2 expression in T98G cells. Treatment with 1.5 mM VPA induced SLC5A8 expression in U87 cells, while treatment of T98G cells with VPA did not affect SLC5A8 expression. Treatment of U87 cells with VPA significantly increased SLC12A5 expression. VPA increases CDH1 expression depending on the VPA dose. CDH2 expression was significantly increased only in the U87 1.5 mM VPA group. Tested VPA doses significantly increased CDH2 expression in T98G cells. When approaching treatment tactics, assessing the cell's sensitivity to the agent is essential.

Repositioning of antiarrhythmics for prostate cancer treatment: a novel strategy to reprogram cancer-associated fibroblasts towards a tumor-suppressive phenotype

BACKGROUND

Cancer-associated fibroblasts (CAFs) play a significant role in fueling prostate cancer (PCa) progression by interacting with tumor cells. A previous gene expression analysis revealed that CAFs up-regulate genes coding for voltage-gated cation channels, as compared to normal prostate fibroblasts (NPFs). In this study, we explored the impact of antiarrhythmic drugs, known cation channel inhibitors, on the activated state of CAFs and their interaction with PCa cells.

METHODS

The effect of antiarrhythmic treatment on CAF activated phenotype was assessed in terms of cell morphology and fibroblast activation markers. CAF contractility and migration were evaluated by 3D gel collagen contraction and scratch assays, respectively. The ability of antiarrhythmics to impair CAF-PCa cell interplay was investigated in CAF-PCa cell co-cultures by assessing tumor cell growth and expression of epithelial-to-mesenchymal transition (EMT) markers. The effect on in vivo tumor growth was assessed by subcutaneously injecting PCa cells in SCID mice and intratumorally administering the medium of antiarrhythmic-treated CAFs or in co-injection experiments, where antiarrhythmic-treated CAFs were co-injected with PCa cells.

RESULTS

Activated fibroblasts show increased membrane conductance for potassium, sodium and calcium, consistently with the mRNA and protein content analysis. Antiarrhythmics modulate the expression of fibroblast activation markers. Although to a variable extent, these drugs also reduce CAF motility and hinder their ability to remodel the extracellular matrix, for example by reducing MMP-2 release. Furthermore, conditioned medium and co-culture experiments showed that antiarrhythmics can, at least in part, reverse the protumor effects exerted by CAFs on PCa cell growth and plasticity, both in androgen-sensitive and castration-resistant cell lines. Consistently, the transcriptome of antiarrhythmic-treated CAFs resembles that of tumor-suppressive NPFs. In vivo experiments confirmed that the conditioned medium or the direct coinjection of antiarrhythmic-treated CAFs reduced the tumor growth rate of PCa xenografts.

CONCLUSIONS

Collectively, such data suggest a new therapeutic strategy for PCa based on the repositioning of antiarrhythmic drugs with the aim of normalizing CAF phenotype and creating a less permissive tumor microenvironment.

In vitro biocompatibility evaluation of functional electrically stimulating microelectrodes on primary glia

Neural interfacing devices interact with the central nervous system to alleviate functional deficits arising from disease or injury. This often entails the use of invasive microelectrode implants that elicit inflammatory responses from glial cells and leads to loss of device function. Previous work focused on improving implant biocompatibility by modifying electrode composition; here, we investigated the direct effects of electrical stimulation on glial cells at the electrode interface. A high-throughput in vitro system that assesses primary glial cell response to biphasic stimulation waveforms at 0 mA, 0.15 mA, and 1.5 mA was developed and optimized. Primary mixed glial cell cultures were generated from heterozygous CX3CR-1+/EGFP mice, electrically stimulated for 4 h/day over 3 days using 75 μm platinum-iridium microelectrodes, and biomarker immunofluorescence was measured. Electrodes were then imaged on a scanning electron microscope to assess sustained electrode damage. Fluorescence and electron microscopy analyses suggest varying degrees of localized responses for each biomarker assayed (Hoescht, EGFP, GFAP, and IL-1β), a result that expands on comparable in vivo models. This system allows for the comparison of a breadth of electrical stimulation parameters, and opens another avenue through which neural interfacing device developers can improve biocompatibility and longevity of electrodes in tissue.

Pan-cancer ion transport signature reveals functional regulators of glioblastoma aggression

Ion channels, transporters, and other ion-flux controlling proteins, collectively comprising the "ion permeome", are common drug targets, however, their roles in cancer remain understudied. Our integrative pan-cancer transcriptome analysis shows that genes encoding the ion permeome are significantly more often highly expressed in specific subsets of cancer samples, compared to pan-transcriptome expectations. To enable target selection, we identified 410 survival-associated IP genes in 33 cancer types using a machine-learning approach. Notably, GJB2 and SCN9A show prominent expression in neoplastic cells and are associated with poor prognosis in glioblastoma, the most common and aggressive brain cancer. GJB2 or SCN9A knockdown in patient-derived glioblastoma cells induces transcriptome-wide changes involving neuron projection and proliferation pathways, impairs cell viability and tumor sphere formation in vitro, perturbs tunneling nanotube dynamics, and extends the survival of glioblastoma-bearing mice. Thus, aberrant activation of genes encoding ion transport proteins appears as a pan-cancer feature defining tumor heterogeneity, which can be exploited for mechanistic insights and therapy development.

TRP Channels in Cancer: Signaling Mechanisms and Translational Approaches

Ion channels play a crucial role in a wide range of biological processes, including cell cycle regulation and cancer progression. In particular, the transient receptor potential (TRP) family of channels has emerged as a promising therapeutic target due to its involvement in several stages of cancer development and dissemination. TRP channels are expressed in a large variety of cells and tissues, and by increasing cation intracellular concentration, they monitor mechanical, thermal, and chemical stimuli under physiological and pathological conditions. Some members of the TRP superfamily, namely vanilloid (TRPV), canonical (TRPC), melastatin (TRPM), and ankyrin (TRPA), have been investigated in different types of cancer, including breast, prostate, lung, and colorectal cancer. TRP channels are involved in processes such as cell proliferation, migration, invasion, angiogenesis, and drug resistance, all related to cancer progression. Some TRP channels have been mechanistically associated with the signaling of cancer pain. Understanding the cellular and molecular mechanisms by which TRP channels influence cancer provides new opportunities for the development of targeted therapeutic strategies. Selective inhibitors of TRP channels are under initial scrutiny in experimental animals as potential anti-cancer agents. In-depth knowledge of these channels and their regulatory mechanisms may lead to new therapeutic strategies for cancer treatment, providing new perspectives for the development of effective targeted therapies.

Interplay of Ca2+ and K+ signals in cell physiology and cancer

The cytoplasmic Ca2+ concentration and the activity of K+ channels on the plasma membrane regulate cellular processes ranging from mitosis to oriented migration. The interplay between Ca2+ and K+ signals is intricate, and different cell types rely on peculiar cellular mechanisms. Derangement of these mechanisms accompanies the neoplastic progression. The calcium signals modulated by voltage-gated (KV) and calcium-dependent (KCa) K+ channel activity regulate progression of the cell division cycle, the release of growth factors, apoptosis, cell motility and migration. Moreover, KV channels regulate the cell response to the local microenvironment by assembling with cell adhesion and growth factor receptors. This chapter summarizes the pathophysiological roles of Ca2+ and K+ fluxes in normal and cancer cells, by concentrating on several biological systems in which these functions have been studied in depth, such as early embryos, mammalian cell lines, T lymphocytes, gliomas and colorectal cancer cells. A full understanding of the underlying mechanisms will offer a comprehensive view of the ion channel implication in cancer biology and suggest potential pharmacological targets for novel therapeutic approaches in oncology.

Ca2+ -activated K+ channels regulate cell volume in human glioblastoma cells

Glioblastoma (GBM), the most lethal form of brain tumors, bases its malignancy on the strong ability of its cells to migrate and invade the narrow spaces of healthy brain parenchyma. Cell migration and invasion are both critically dependent on changes in cell volume and shape driven by the transmembrane transport of osmotically important ions such as K+ and Cl- . However, while the Cl- channels participating in cell volume regulation have been clearly identified, the precise nature of the K+ channels involved is still uncertain. Using a combination of electrophysiological and imaging approaches in GBM U87-MG cells, we found that hypotonic-induced cell swelling triggered the opening of Ca2+ -activated K+ (KCa ) channels of large and intermediate conductance (BKCa and IKCa , respectively), both highly expressed in GBM cells. The influx of Ca2+ mediated by the hypotonic-induced activation of mechanosensitive channels was found to be a key step for opening both the BKCa and the IKCa channels. Finally, the activation of both KCa channels mediated by mechanosensitive channels was found to be essential for the development of the regulatory volume decrease following hypotonic shock. Taken together, these data indicate that KCa channels are the main K+ channels responsible for the volume regulation in U87-MG cells.

Role of Na+/Ca2+ Exchanger (NCX) in Glioblastoma Cell Migration (In Vitro)

Glioblastoma (GBM) is the most malignant form of primary brain tumor. It is characterized by the presence of highly invasive cancer cells infiltrating the brain by hijacking neuronal mechanisms and interacting with non-neuronal cell types, such as astrocytes and endothelial cells. To enter the interstitial space of the brain parenchyma, GBM cells significantly shrink their volume and extend the invadopodia and lamellipodia by modulating their membrane conductance repertoire. However, the changes in the compartment-specific ionic dynamics involved in this process are still not fully understood. Here, using noninvasive perforated patch-clamp and live imaging approaches on various GBM cell lines during a wound-healing assay, we demonstrate that the sodium-calcium exchanger (NCX) is highly expressed in the lamellipodia compartment, is functionally active during GBM cell migration, and correlates with the overexpression of large conductance K+ channel (BK) potassium channels. Furthermore, a NCX blockade impairs lamellipodia formation and maintenance, as well as GBM cell migration. In conclusion, the functional expression of the NCX in the lamellipodia of GBM cells at the migrating front is a conditio sine qua non for the invasion strategy of these malignant cells and thus represents a potential target for brain tumor treatment.

Diagnostic and Therapeutic Approaches for Glioblastoma and Neuroblastoma Cancers Using Chlorotoxin Nanoparticles

Glioblastoma multiforme (GB) and high-risk neuroblastoma (NB) are known to have poor therapeutic outcomes. As for most cancers, chemotherapy and radiotherapy are the current mainstay treatments for GB and NB. However, the known limitations of systemic toxicity, drug resistance, poor targeted delivery, and inability to access the blood-brain barrier (BBB), make these treatments less satisfactory. Other treatment options have been investigated in many studies in the literature, especially nutraceutical and naturopathic products, most of which have also been reported to be poorly effective against these cancer types. This necessitates the development of treatment strategies with the potential to cross the BBB and specifically target cancer cells. Compounds that target the endopeptidase, matrix metalloproteinase 2 (MMP-2), have been reported to offer therapeutic insights for GB and NB since MMP-2 is known to be over-expressed in these cancers and plays significant roles in such physiological processes as angiogenesis, metastasis, and cellular invasion. Chlorotoxin (CTX) is a promising 36-amino acid peptide isolated from the venom of the deathstalker scorpion, Leiurus quinquestriatus, demonstrating high selectivity and binding affinity to a broad-spectrum of cancers, especially GB and NB through specific molecular targets, including MMP-2. The favorable characteristics of nanoparticles (NPs) such as their small sizes, large surface area for active targeting, BBB permeability, etc. make CTX-functionalized NPs (CTX-NPs) promising diagnostic and therapeutic applications for addressing the many challenges associated with these cancers. CTX-NPs may function by improving diffusion through the BBB, enabling increased localization of chemotherapeutic and genotherapeutic drugs to diseased cells specifically, enhancing imaging modalities such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), optical imaging techniques, image-guided surgery, as well as improving the sensitization of radio-resistant cells to radiotherapy treatment. This review discusses the characteristics of GB and NB cancers, related treatment challenges as well as the potential of CTX and its functionalized NP formulations as targeting systems for diagnostic, therapeutic, and theranostic purposes. It also provides insights into the potential mechanisms through which CTX crosses the BBB to bind cancer cells and provides suggestions for the development and application of novel CTX-based formulations for the diagnosis and treatment of GB and NB in the future.

Potassium Ion Channels in Glioma: From Basic Knowledge into Therapeutic Applications

Ion channels, specifically those controlling the flux of potassium across cell membranes, have recently been shown to exhibit an important role in the pathophysiology of glioma, the most common primary central nervous system tumor with a poor prognosis. Potassium channels are grouped into four subfamilies differing by their domain structure, gating mechanisms, and functions. Pertinent literature indicates the vital functions of potassium channels in many aspects of glioma carcinogenesis, including proliferation, migration, and apoptosis. The dysfunction of potassium channels can result in pro-proliferative signals that are highly related to calcium signaling as well. Moreover, this dysfunction can feed into migration and metastasis, most likely by increasing the osmotic pressure of cells allowing the cells to initiate the "escape" and "invasion" of capillaries. Reducing the expression or channel blockage has shown efficacy in reducing the proliferation and infiltration of glioma cells as well as inducing apoptosis, priming several approaches to target potassium channels in gliomas pharmacologically. This review summarizes the current knowledge on potassium channels, their contribution to oncogenic transformations in glioma, and the existing perspectives on utilizing them as potential targets for therapy.

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.

Risk of Glioblastoma Multiforme in Patients Taking Ion Channel Blockers

Background

Ion channels play a role in the development and progression of glioblastoma multiforme. This study investigates the association between the risk of developing glioblastoma multiforme in patients taking these medications.

Methods

A retrospective propensity score-matched analysis was performed using the TriNetX multinational electronic health record database for patients taking verapamil, digoxin, amiodarone, or diltiazem versus those not taking these medications. The outcome of interest was the incidence of glioblastoma multiforme.

Results

Verapamil users had an OR of 0.494 (p < 0.0001) of developing glioblastoma versus verapamil non-users. Patients on digoxin had an OR of 0.793 (p = 0.2393), patients on amiodarone had an OR of 0.600 (p = 0.0035), patients on diltiazem had an OR of 0.584 (p < 0.0001), and patients on verapamil, digoxin, amiodarone, or diltiazem had an OR of 0.641 (p < 0.0001) of developing glioblastoma versus patients not taking these medications.

Conclusion

In patients taking the ion channel blockers diltiazem, amiodarone, or verapamil, the odds of developing glioblastoma multiforme were lower than in patients not taking these medications.

Cell-based analysis of CLIC5A and SLC12A2 variants associated with hearing impairment in two African families

We have previously reported CLIC5A and SLC12A2 variants in two families from Cameroon and Ghana, segregating non-syndromic hearing impairment (NSHI). In this study, biological assays were performed to further functionally investigate the pathogenicity of CLIC5 [c.224T>C; p.(L75P)] and SCL12A2 [c.2935G>A: p.(E979K)] variants. Ectopic expression of the proteins in a cell model shows that compared to wild-type, both the CLIC5A and SLC12A2 variants were overexpressed. The mutant CLIC5A protein appears as aggregated perinuclear bodies while the wild-type protein was evenly distributed in the cytoplasm. Furthermore, cells transfected with the wild-type CLIC5A formed thin membrane filopodia-like protrusions which were absent in the CLIC5A mutant expressing and control cells. On the other hand, the wild-type SLC12A2 expressing cells had an axon-like morphology which was not observed in the mutant expressing and control cells. A network analysis revealed that CLIC5A can interact with at least eight proteins at the base of the stereocilia. This study has generated novel biological data associated with the pathogenicity of targeted variants in CLIC5A and SLC12A2, found in two African families, and therefore expands our understanding of their pathobiology in hearing impairment.

Metabolic Reprogramming in Cancer Cells: Emerging Molecular Mechanisms and Novel Therapeutic Approaches

The constant changes in cancer cell bioenergetics are widely known as metabolic reprogramming. Reprogramming is a process mediated by multiple factors, including oncogenes, growth factors, hypoxia-induced factors, and the loss of suppressor gene function, which support malignant transformation and tumor development in addition to cell heterogeneity. Consequently, this hallmark promotes resistance to conventional anti-tumor therapies by adapting to the drastic changes in the nutrient microenvironment that these therapies entail. Therefore, it represents a revolutionary landscape during cancer progression that could be useful for developing new and improved therapeutic strategies targeting alterations in cancer cell metabolism, such as the deregulated mTOR and PI3K pathways. Understanding the complex interactions of the underlying mechanisms of metabolic reprogramming during cancer initiation and progression is an active study field. Recently, novel approaches are being used to effectively battle and eliminate malignant cells. These include biguanides, mTOR inhibitors, glutaminase inhibition, and ion channels as drug targets. This review aims to provide a general overview of metabolic reprogramming, summarise recent progress in this field, and emphasize its use as an effective therapeutic target against cancer.

A rare variant analysis framework using public genotype summary counts to prioritize disease-predisposition genes

Sequencing cases without matched healthy controls hinders prioritization of germline disease-predisposition genes. To circumvent this problem, genotype summary counts from public data sets can serve as controls. However, systematic inflation and false positives can arise if confounding factors are not controlled. We propose a framework, consistent summary counts based rare variant burden test (CoCoRV), to address these challenges. CoCoRV implements consistent variant quality control and filtering, ethnicity-stratified rare variant association test, accurate estimation of inflation factors, powerful FDR control, and detection of rare variant pairs in high linkage disequilibrium. When we applied CoCoRV to pediatric cancer cohorts, the top genes identified were cancer-predisposition genes. We also applied CoCoRV to identify disease-predisposition genes in adult brain tumors and amyotrophic lateral sclerosis. Given that potential confounding factors were well controlled after applying the framework, CoCoRV provides a cost-effective solution to prioritizing disease-risk genes enriched with rare pathogenic variants.

Recombinantly expressed MeICT, a new toxin from Mesobuthus eupeus scorpion, inhibits glioma cell proliferation and downregulates Annexin A2 and FOXM1 genes

Gliomas are highly invasive and lethal malignancy that do not respond to current therapeutic approaches. Novel therapeutic agents are required to target molecular mechanisms involved in glioma progression. MeICT is a new short-chain toxin isolated from Mesobuthus eupeus scorpion venom. This toxin contained 34 amino acid residues and belongs to chloride channels toxins. In this study, the coding sequence of MeICT was cloned into the pET32Rh vector and a high yield of soluble recombinant MeICT was expressed and purified. Recombinant MeICT-His significantly inhibited the proliferation and migration of glioma cells at low concentration. In vivo studies showed that MeICT was not toxic when administrated to mice at high doses. We also determined the effect of MeICT on the mRNA expression of MMP-2, Annexin A2 and FOXM-2 that are key molecules in the progression and invasion of glioma. Expression of Annexin A2 and FOXM1 mRNA was significantly down-regulated following treatment with MeICT. However, no significant decrease in the expression of MMP-2 gene was identified. In this study a short toxin with four disulfide bonds was successfully produced and its anti-cancer effects was detected. Our findings suggest that recombinant MeICT can be considered as a new potent agent for glioma targeting.

Bioelectric Dysregulation in Cancer Initiation, Promotion, and Progression

Cancer is primarily a disease of dysregulation – both at the genetic level and at the tissue organization level. One way that tissue organization is dysregulated is by changes in the bioelectric regulation of cell signaling pathways. At the basis of bioelectricity lies the cellular membrane potential or V_mem, an intrinsic property associated with any cell. The bioelectric state of cancer cells is different from that of healthy cells, causing a disruption in the cellular signaling pathways. This disruption or dysregulation affects all three processes of carcinogenesis – initiation, promotion, and progression. Another mechanism that facilitates the homeostasis of cell signaling pathways is the production of extracellular vesicles (EVs) by cells. EVs also play a role in carcinogenesis by mediating cellular communication within the tumor microenvironment (TME). Furthermore, the production and release of EVs is altered in cancer. To this end, the change in cell electrical state and in EV production are responsible for the bioelectric dysregulation which occurs during cancer. This paper reviews the bioelectric dysregulation associated with carcinogenesis, including the TME and metastasis. We also look at the major ion channels associated with cancer and current technologies and tools used to detect and manipulate bioelectric properties of cells.

A guide to plasma membrane solute carrier proteins

This review aims to serve as an introduction to the solute carrier proteins (SLC) superfamily of transporter proteins and their roles in human cells. The SLC superfamily currently includes 458 transport proteins in 65 families that carry a wide variety of substances across cellular membranes. While members of this superfamily are found throughout cellular organelles, this review focuses on transporters expressed at the plasma membrane. At the cell surface, SLC proteins may be viewed as gatekeepers of the cellular milieu, dynamically responding to different metabolic states. With altered metabolism being one of the hallmarks of cancer, we also briefly review the roles that surface SLC proteins play in the development and progression of cancer through their influence on regulating metabolism and environmental conditions.

Cilostazol eliminates radiation-resistant glioblastoma by re-evoking big conductance calcium-activated potassium channel activity

In spite of radio- and chemotherapy, glioblastoma (GBM) develops therapeutic resistance leading to recurrence and poor prognosis. Therefore, understanding the underlying mechanisms of resistance is important to improve the treatment of GBM. To this end, we developed a radiation-resistant cell model by exposure to consecutive periods of irradiation. Simultaneously, single high-dose irradiation was introduced to determine "when" GBM developed consecutive irradiation-induced resistance (CIIR). We found that CIIR promoted TGF-β secretion, activated pro-survival Akt, and downregulated p21 in a p53-independent manner. Furthermore, CIIR upregulated multidrug-resistant proteins, resulting in temozolomide resistance. CIIR GBM also enhanced cell mobility and accelerated cell proliferation. The big-conductance calcium-activated potassium channel (BK channel) is highly expressed and activated in GBM. However, CIIR diminishes BK channel activity in an expression-independent manner. Cilostazol is a phosphodiesterase-3 inhibitor for the treatment of intermittent claudication and was able to reverse CIIR-induced BK channel inactivation. Paxilline, a BK channel blocker, promoted cell migration and proliferation in parental GBM cells. In contrast, Cilostazol inhibited CIIR-induced cell motility, proliferation, and the ability to form tumor spheres. Moreover, we established a radiation-resistant GBM in vivo model by intracranially injecting CIIR GBM cells into the brains of NOD/SCID mice. We found that Cilostazol delayed tumor in vivo growth and prolonged survival. As such, inactivation of the BK channel assists GBM in developing radiation resistance. Accordingly, restoring BK channel activity may be an effective strategy to improve therapeutic efficacy, and cilostazol could be repurposed to treat GBM.

A Drastic Shift in Lipid Adducts in Colon Cancer Detected by MALDI-IMS Exposes Alterations in Specific K+ Channels

Even though colorectal cancer (CRC) is one of the most preventable cancers, it is one of the deadliest, and recent data show that the incidence in people <50 years has unexpectedly increased. While new techniques for CRC molecular classification are emerging, no molecular feature is as yet firmly associated with prognosis. Imaging mass spectrometry (IMS) lipidomic analyses have demonstrated the specificity of the lipid fingerprint in differentiating pathological from healthy tissues. During IMS lipidomic analysis, the formation of ionic adducts is common. Of particular interest is the [Na⁺]/[K⁺] adduct ratio, which already functions as a biomarker for homeostatic alterations. Herein, we show a drastic shift of the [Na⁺]/[K⁺] adduct ratio in adenomatous colon mucosa compared to healthy mucosa, suggesting a robust increase in K⁺ levels. Interrogating public databases, a strong association was found between poor diagnosis and voltage-gated potassium channel subunit beta-2 (KCNAB2) overexpression. We found this overexpression in three CRC molecular subtypes defined by the CRC Subtyping Consortium, making KCNAB2 an interesting pharmacological target. Consistently, its pharmacological inhibition resulted in a dramatic halt in commercial CRC cell proliferation. Identification of potential pharmacologic targets using lipid adduct information emphasizes the great potential of IMS lipidomic techniques in the clinical field.

Megalencephalic leukoencephalopathy with subcortical cysts 1 (MLC1) promotes glioblastoma cell invasion in the brain microenvironment

Glioblastoma (GBM), or grade IV astrocytoma, is a malignant brain cancer that contains subpopulations of proliferative and invasive cells that coordinately drive primary tumor growth, progression, and recurrence after therapy. Here, we have analyzed functions for megalencephalic leukoencephalopathy with subcortical cysts 1 (Mlc1), an eight-transmembrane protein normally expressed in perivascular brain astrocyte end feet that is essential for neurovascular development and physiology, in the pathogenesis of GBM. We show that Mlc1 is expressed in human stem-like GBM cells (GSCs) and is linked to the development of primary and recurrent GBM. Genetically inhibiting MLC1 in GSCs using RNAi-mediated gene silencing results in diminished growth and invasion in vitro as well as impaired tumor initiation and progression in vivo. Biochemical assays identify the receptor tyrosine kinase Axl and its intracellular signaling effectors as important for MLC1 control of GSC invasive growth. Collectively, these data reveal key functions for MLC1 in promoting GSC growth and invasion, and suggest that targeting the Mlc1 protein or its associated signaling effectors may be a useful therapy for blocking tumor progression in patients with primary or recurrent GBM.

Ion Channels as Therapeutic Targets in High Grade Gliomas

Simple Summary

Glioblastoma multiforme is an aggressive grade IV lethal brain tumour with a median survival of 14 months. Despite surgery to remove the tumour, and subsequent concurrent chemotherapy and radiotherapy, there is little in terms of effective treatment options. Because of this, exploring new treatment avenues is vital. Brain tumours are intrinsically electrically active; expressing unique patterns of ion channels, and this is a characteristic we can exploit. Ion channels are specialised proteins in the cell’s membrane that allow for the passage of positive and negatively charged ions in and out of the cell, controlling membrane potential. Membrane potential is a crucial biophysical signal in normal and cancerous cells. Research has identified that specific classes of ion channels not only move the cell through its cell cycle, thus encouraging growth and proliferation, but may also be essential in the development of brain tumours. Inhibition of sodium, potassium, calcium, and chloride channels has been shown to reduce the capacity of glioblastoma cells to grow and invade. Therefore, we propose that targeting ion channels and repurposing commercially available ion channel inhibitors may hold the key to new therapeutic avenues in high grade gliomas.

Abstract

Glioblastoma multiforme (GBM) is a lethal brain cancer with an average survival of 14–15 months even with exhaustive treatment. High grade gliomas (HGG) represent the leading cause of CNS cancer-related death in children and adults due to the aggressive nature of the tumour and limited treatment options. The scarcity of treatment available for GBM has opened the field to new modalities such as electrotherapy. Previous studies have identified the clinical benefit of electrotherapy in combination with chemotherapeutics, however the mechanistic action is unclear. Increasing evidence indicates that not only are ion channels key in regulating electrical signaling and membrane potential of excitable cells, they perform a crucial role in the development and neoplastic progression of brain tumours. Unlike other tissue types, neural tissue is intrinsically electrically active and reliant on ion channels and their function. Ion channels are essential in cell cycle control, invasion and migration of cancer cells and therefore present as valuable therapeutic targets. This review aims to discuss the role that ion channels hold in gliomagenesis and whether we can target and exploit these channels to provide new therapeutic targets and whether ion channels hold the mechanistic key to the newfound success of electrotherapies.

Therapeutic Anticancer Uses of the Active Principles of "Rhopalurus junceus" Venom

The Rhopalurus junceus is a scorpion belonging to the Buthidae family that finds its habitat in Cuba. This scorpion is known by the common name of "Blue Scorpion". The venom is used on the island of Cuba as an alternative cure for cancer and, more recently, in the research of active components for biomedicine. Recently, the venom has been tested in several studies to investigate its effects on cancer cell lines, and the initial results of in vitro studies demonstrated how this poison can be effective on certain carcinoma cell lines (Hela, SiHa, Hep-2, NCI-H292, A549, MDA-MB-231, MDA-MB-468, and HT-29). The aim of this review is, therefore, to describe the effects of the venom on carcinoma lines and to investigate all anti-cancer properties studied in the literature. The research was conducted using four databases, Pub Med, Scopus, EBSCO, and Web of Science, through the use of keywords, by two independent reviewers following the PRISMA protocol, identifying 57 records. The results led to a total of 13 articles that met the eligibility criteria. The data extracted for the purpose of meta-analysis included the IC₅₀ of the venom on carcinoma cell lines. The results of the meta-analysis provided a pooled mean of the IC₅₀ of 0.645 mg/mL (95% CI: 0.557, 0.733), with a standard error (SE) = 0.045, p < 0.001. The analysis of the subgroups, differentiated by the type of cell line used, provided insight regarding how the scorpion venom was effective on the cell lines of lung origin (NCI-H292, A549, and MRC-5) with a pooled mean of IC50 0.460 mg/mL (95% CI: 0.290, 0.631) SE (0.087) p < 0.001. The results described in the literature for in vitro studies are encouraging, and further investigations should be carried out and deepened.

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Role of NKCC1 Activity in Glioma K+ Homeostasis and Cell Growth: New Insights With the Bumetanide-Derivative STS66

Introduction: Na⁺-K⁺-2Cl⁻ cotransporter isoform 1 (NKCC1) is important in regulating intracellular K⁺ and Cl⁻ homeostasis and cell volume. In this study, we investigated a role of NKCC1 in regulating glioma K⁺ influx and proliferation in response to apoptosis inducing chemotherapeutic drug temozolomide (TMZ). The efficacy of a new bumetanide (BMT)-derivative NKCC1 inhibitor STS66 [3-(butylamino)-2-phenoxy-5-[(2, 2, 2-trifluoroethylamino) methyl] benzenesulfonamide] in blocking NKCC1 activity was compared with well-established NKCC1 inhibitor BMT.

Methods: NKCC1 activity in cultured mouse GL26 and SB28-GFP glioma cells was measured by Rb⁺ (K⁺) influx. The WNK1-SPAK/OSR1-NKCC1 signaling and AKT/ERK-mTOR signaling protein expression and activation were assessed by immunoblotting. Cell growth was determined by bromodeoxyuridine (BrdU) incorporation assay, MTT proliferation assay, and cell cycle analysis. Impact of STS66 and BMT on cell Rb⁺ influx and growth was measured in glioma cells treated with or without TMZ.

Results: Rb⁺ influx assay showed that 10 μM BMT markedly decreased the total Rb⁺ influx and no additional inhibition detected at >10 μM BMT. In contrast, the maximum effects of STS66 on Rb⁺ influx inhibition were at 40–60 μM. Both BMT and STS66 reduced TMZ-mediated NKCC1 activation and protein upregulation. Glioma cell growth can be reduced by STS66. The most robust inhibition of glioma growth, cell cycle, and AKT/ERK signaling was achieved by the TMZ + STS66 treatment.

Conclusion: The new BMT-derivative NKCC1 inhibitor STS66 is more effective than BMT in reducing glioma cell growth in part by inhibiting NKCC1-mediated K⁺ influx. TMZ + STS66 combination treatment reduces glioma cell growth via inhibiting cell cycle and AKT-ERK signaling.

Blockade of Cell Volume Regulatory Protein NKCC1 Increases TMZ-Induced Glioma Apoptosis and Reduces Astrogliosis

Glioma is one of the most common primary malignant tumors of the central nervous system accounting for approximately 40% of all intracranial tumors. Temozolomide is a conventional chemotherapy drug for adjuvant treatment of patients with high-risk gliomas, including grade II to grade IV. Our bioinformatic analysis of The Cancer Genome Atlas and Chinese Glioma Genome Atlas datasets and immunoblotting assay show that SLC12A2 gene and its encoded Na+-K+-2Cl- cotransporter isoform 1 (NKCC1) protein are abundantly expressed in grade II-IV gliomas. NKCC1 regulates cell volume and intracellular Cl- concentration, which promotes glioma cell migration, resistance to temozolomide, and tumor-related epilepsy in experimental glioma models. Using mouse syngeneic glioma models with intracranial transplantation of two different glioma cell lines (GL26 and SB28), we show that NKCC1 protein in glioma tumor cells as well as in tumor-associated reactive astrocytes was significantly upregulated in response to temozolomide monotherapy. Combination therapy of temozolomide with the potent NKCC1 inhibitor bumetanide reduced tumor proliferation, potentiated the cytotoxic effects of temozolomide, decreased tumor-associated reactive astrogliosis, and restored astrocytic GLT-1 and GLAST glutamate transporter expression. The combinatorial therapy also led to suppressed tumor growth and prolonged survival of mice bearing GL26 glioma cells. Taken together, these results demonstrate that NKCC1 protein plays multifaceted roles in the pathogenesis of glioma tumors and presents as a therapeutic target for reducing temozolomide-mediated resistance and tumor-associated astrogliosis.

Squaring the Circle: A New Study of Inward and Outward-Rectifying Potassium Currents in U251 GBM Cells

In the present study, the functional role of the inwardly rectifying K+ channel, Kir4.1, and large-conductance Ca2+-activated K+ (BK) channel during cell migration in U251 cell line was investigated. We focused on polarised cells which are positive for the active-Cdc42 migration marker. The perforated patch technique was used to avoid intracellular dialysis and to maintain physiological changes in intracellular calcium. Wound healing was employed to assay migration after 24 h. Polarised cells recorded displayed different hallmarks of undifferentiated glial cells: depolarised resting membrane potential and high membrane resistance. Cells recorded outside wounded area did not display either constitutive inward or outward rectification. After migration, U251 cells were characterised by a constitutively smaller Kir4.1 and larger BK currents with a linearly related amplitude. Menthol modulation increased both currents in a linearly dependent manner, indicating a common mechanism triggered by activation of transient receptor potential melastatin 8 (TRPM8), a Ca2+-permeable non-selective cation channel. We hypothesised that both migration and menthol modulation would share an increase of intracellular calcium triggering the increase in Kir4.1 and BK channels. Immunocytochemistry demonstrated the cytoplasmic expression of both Kir4.1 and BK channels and a mislocation in the nucleus under basal conditions. Before and after migration, polarised cells increased the expression of Kir4.1 and BK channels both in the cytoplasm and nucleus. TEM ultrastructural analysis displayed a different nuclear distribution of Kir4.1 and BK channels. In the present study, the physiological role of Kir4.1 and BK currents at membrane potential, their involvement in migration, and the functional role of nuclear channels were discussed.

Quinine-Based Semisynthetic Ion Transporters with Potential Antiproliferative Activities

Synthetic ion transporters have attracted tremendous attention for their therapeutic potential against various ion-transport-related diseases, including cancer. Inspired by the structure and biological activities of natural products, we synthesized a small series of squaramide and thiourea derivatives of quinine and investigated their ion transport activities. The involvement of a quinuclidine moiety for the cooperative interactions of Cl^- and H⁺ ions with the thiourea or squaramide moiety resulted in an effectual transport of these ions across membranes. The interference of ionic equilibrium by the potent Cl^- ion carrier selectively induced cancer cell death by endorsing caspase-arbitrated apoptosis. In vivo assessment of the potent ionophore showed an efficient reduction in tumor growth with negligible immunotoxicity to other organs.

Scorpion venoms and associated toxins as anticancer agents: update on their application and mechanism of action

Cancer remains one of the deadliest non-infectious diseases of the 21^st century, causing millions of mortalities per year worldwide. Analyses of conventional treatments, such as radiotherapy and chemotherapy, have shown not only a lower therapeutic efficiency rate but also plethora of side-effects. Considering the desperate need to identify promising anticancer agents, researchers are in quest to design and develop new tumoricidal drugs from natural sources. Over the past few years, scorpion venoms have shown exemplary roles as pivotal anticancer agents. Scorpion venoms associated metabolites, particularly toxins demonstrated in vitro anticancer attributes against diversified cell lines by inhibiting the growth and progression of the cell cycle, inhibiting metastasis by blocking ion channels such as K⁺ and Cl^- , and/or inducing apoptosis by intrinsic and extrinsic pathways. This review sheds light not only on in vitro anticancer properties of distinct scorpion venoms and their toxins, but also on their mechanism of action for designing and developing new therapeutic drugs in future.

NKCC1 involvement in the epithelial-to-mesenchymal transition is a prognostic biomarker in gliomas

Background

Gliomas are the most prevalent type of intracranial tumors. NKCC1 is an important regulator in tumor cell volume. We noticed that abnormally high NKCC1 expression resulted in changes in the shape and adhesion of glioma cells. However, little is known about the role of NKCC1 in the epithelial-mesenchymal transition (EMT) of gliomas. This study aims to clarify the biological function of NKCC1 in glioblastoma multiforme (GBM) progression.

Methods

Using data from The Cancer Genome Atlas (TCGA), we performed a Kaplan–Meier analysis on NKCC1 expression levels to estimate the rate of survival of mesenchymal GBM patients. The correlation between NKCC1 and EMT-related proteins was analyzed from the Gene Expression Profiling Interactive Analysis (GEPIA) server. We conducted Gene Set Enrichment Analysis (GSEA) to verify molecular signatures and pathways. We then studied the expression of NKCC1 in grade I–IV glioma tissue samples collected from patients using immunohistochemistry (IHC). Finally, we evaluated the effects of NKCC1 migration and invasion on the cellular behaviors of U251 cells using the transwell assay and western blots.

Results

High NKCC1 expression was associated with poor prognoses in mesenchymal GBM. Our results suggest a correlation between NKCC1 and EMT-protein markers: CDH2 and VIM. GSEA showed that gliomas, TGF-beta signaling and EMT were enriched in the NKCC1 high expression phenotype. Higher expression levels of NKCC1 in gliomas correlate with higher glioma grades. Transwell assay and western blot results demonstrated that the knockdown of NKCC1 led to a reduction in migration and invasion, while also inhibiting MMP-2 and MMP-9 expression in U251.

Conclusion

These results suggest that high expression of NKCC1 regulates EMT in gliomas, providing a new therapeutic strategy for addressing the spread of gliomas by inhibiting the spread of intracranial tumors.

Pleiotropic Anticancer Properties of Scorpion Venom Peptides: Rhopalurus princeps Venom as an Anticancer Agent

To date, the success of conventional chemotherapy, radiotherapy, and targeted biological therapies in cancer treatment is not satisfactory. The main reasons for such outcomes rely on low target selectivity, primarily in chemo- and radiotherapy, ineffectiveness to metastatic disease, drug resistance, and severe side effects. Although immune checkpoint inhibitors may offer better clinical promise, success is still limited. Since cancer is a complex systemic disease, the need for new therapeutic modalities that can target or block several steps of cancer cell characteristics, modulate or repolarize immune cells, and are less toxic to healthy tissues is essential. Of these promising therapeutic modalities are pleiotropic natural products in which scorpion venom (SV) is an excellent example. SV consists of complex bioactive peptides that are disulfide-rich of different peptides’ length, potent, stable, and exerts various multi-pharmacological actions. SV peptides also contain ion channel inhibitors. These ion channels are dysregulated and overexpressed in cancer cells, and play essential roles in cancer development and invasion, as well as depolarizing immune cells. Furthermore, SV has been found to induce cancer cell apoptosis, and inhibit cancer cells proliferation, invasion, metastasis, and angiogenesis. In the current review, we are presenting data that show the pleiotropic effect of SV against different types of human cancer as well as revealing one potential anticancer agent, Rhopalurus princeps venom. Furthermore, we are addressing what is needed to be done to translate these potential cancer therapeutics to the clinic.

Selective Inhibition of Liver Cancer Cells Using Venom Peptide

Increasingly cancer is being viewed as a channelopathy because the passage of ions via ion channels and transporters mediate the regulation of tumor cell survival, death, and motility. As a result, a potential targeted therapy for cancer is to use venom peptides that are selective for ion channels and transporters overexpressed in tumor cells. Here we describe the selectivity and mechanism of action of terebrid snail venom peptide, Tv1, for treating the most common type of liver cancer, hepatocellular carcinoma (HCC). Tv1 inhibited the proliferation of murine HCC cells and significantly reduced tumor size in Tv1-treated syngeneic tumor-bearing mice. Tv1's mechanism of action involves binding to overexpressed transient receptor potential (TRP) channels leading to calcium dependent apoptosis resulting from down-regulation of cyclooxygenase-2 (COX-2). Our findings demonstrate the importance of modulating ion channels and the unique potential of venom peptides as tumor specific ligands in the quest for targeted cancer therapies.

New Perspectives in the Treatment of Tumor Cells by Electromagnetic Radiation at Resonance Frequencies in Cellular Membrane Channels

Background:

The use of electromagnetic fields has been considered as adjuvant therapy for the treatment of cancer given that some clinical trials have shown that the irradiation of cancer cells with electromagnetic fields can slow down the disease progression.

Aims:

We hypothesize that this effect could be amplified by irradiating tumor cells with electromagnetic fields having frequencies close to the natural resonant frequencies of membrane channels in tumor cells, in order to obtain a significant change of the ion flux across tumor cell membrane channels, inducing the largest harmful alteration in their cellular function.

Methods:

Neuronal-like cells were used as a cell model and exposed for 6 h to electromagnetic fields at different frequencies (0, 50 Hz, 900 MHz) at the same intensity of 2 mT. The exposure system was represented by two Helmholtz coils driven by a power amplifier in current mode and an arbitrary function generator. FTIR spectroscopy was used to evaluate the results of the exposure.

Results:

The results of this study showed that the Amide I vibration band increased in intensity with the increase of the frequency, leading us to assume that the displacement of the cell channels α-helices depends on the frequency of the applied electromagnetic fields.

Conclusion:

This preliminary result leads us to plan future research aimed at searching for the natural frequencies of membrane channels in tumor cells using resonant electromagnetic fields in order to damage the cellular functions of tumor cells. Clinical trials are needed to confirm such a hypothesis derived from this physical study.

Altered expression and functional role of ion channels in leukemia: bench to bedside

Leukemic cells' (LCs) survival, proliferation, activation, differentiation, and invasiveness/migration can be mediated through the function of cation and anion channels that are involved in volume regulation, polarization, cytoskeleton, and extracellular matrix reorganization. This study will review the expression of ion channels in LCs and their possible function in leukemia progression. We searched relevant literature by a PubMed (2002-2019) of English-language literature using the terms "ion channels", "leukemia", "proliferation", "differentiation", "apoptosis", and "migration". Altered expression and dysfunction of ion channels can have a strong impact on hematopoietic cell and LCs physiology and signaling, which contributes to the vital processes such as proliferation, differentiation, and apoptosis. Indeed, it can be stated that changing expression of ion channels can affect the onset and progression as well as clinical features and therapeutic responses of leukemia via inducing the maintenance of LCs. Since ion channels are membrane proteins, they can be easily accessible in LCs for understanding their influence on leukemia progression. On the other hand, ion channels can be new potential targets for chemotherapeutic agents, which may open a novel clinical and pharmaceutical field in leukemia therapy.