Sodium channel-inhibiting drugs and survival of breast, colon and prostate cancer: a population-based study

Repurposing of nervous system drugs for cancer treatment: recent advances, challenges, and future perspectives

The nervous system plays a critical role in developmental biology and oncology, influencing processes from ontogeny to the complex dynamics of cancer progression. Interactions between the nervous system and cancer significantly affect oncogenesis, tumor growth, invasion, metastasis, treatment resistance, inflammation that promotes tumors, and the immune response. A comprehensive understanding of the signal transduction pathways involved in cancer biology is essential for devising effective anti-cancer strategies and overcoming resistance to existing therapies. Recent advances in cancer neuroscience promise to establish a new cornerstone of cancer therapy. Repurposing drugs originally developed for modulating nerve signal transduction represent a promising approach to target oncogenic signaling pathways in cancer treatment. This review endeavors to investigate the potential of repurposing neurological drugs, which target neurotransmitters and neural pathways, for oncological applications. In this context, it aims to bridge the interdisciplinary gap between neurology, psychiatry, internal medicine, and oncology. By leveraging already approved drugs, researchers can utilize existing extensive safety and efficacy data, thereby reducing both the time and financial resources necessary for the development of new cancer therapies. This strategy not only promises to enhance patient outcomes but also to expand the array of available treatments, thereby enriching the therapeutic landscape in oncology.

Insights into the Emerging Therapeutic Targets of Triple-negative Breast Cancer

Triple-negative Breast Cancer (TNBC), the most aggressive breast cancer subtype, is characterized by the non-appearance of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Clinically, TNBC is marked by its low survival rate, poor therapeutic outcomes, high aggressiveness, and lack of targeted therapies. Over the past few decades, many clinical trials have been ongoing for targeted therapies in TNBC. Although some classes, such as Poly (ADP Ribose) Polymerase (PARP) inhibitors and immunotherapies, have shown positive therapeutic outcomes, however, clinical effects are not much satisfiable. Moreover, the development of drug resistance is the major pattern observed in many targeted monotherapies. The heterogeneity of TNBC might be the cause for limited clinical benefits. Hence,, there is a need for the potential identification of new therapeutic targets to address the above limitations. In this context, some novel targets that can address the above-mentioned concerns are emerging in the era of TNBC therapy, which include Hypoxia Inducible Factor (HIF-1α), Matrix Metalloproteinase 9 (MMP-9), Tumour Necrosis Factor-α (TNF-α), β-Adrenergic Receptor (β-AR), Voltage Gated Sodium Channels (VGSCs), and Cell Cycle Regulators. Currently, we summarize the ongoing clinical trials and discuss the novel therapeutic targets in the management of TNBC.

Sodium channels in non-excitable cells: powerful actions and therapeutic targets beyond Hodgkin and Huxley

Voltage-gated sodium channels (VGSCs) are best known for their role in the generation and propagation of action potentials in neurons, muscle cells, and cardiac myocytes, which have traditionally been labeled as 'excitable'. However, emerging evidence challenges this traditional perspective. It is now clear that VGSCs are also expressed in a broad spectrum of cells outside the neuromuscular realm, where they regulate diverse cellular functions. In this review, we summarize current knowledge on the expression, regulation, and function of VGSCs in non-neuromuscular cells, highlighting their contributions to physiological processes and pathological conditions. Dynamic expression patterns of VGSCs in different cell types, involvement of VGSCs in cellular functions, such as phagocytosis, motility, and cytokine release, and their potential as therapeutic targets for diseases that include inflammatory disorders, osteoarthritis (OA), and cancer, are discussed. This new understanding of VGSCs and their effects on cells outside the neuromuscular realm opens new avenues for research and therapeutic interventions.

Disrupting Na+ ion homeostasis and Na+/K+ ATPase activity in breast cancer cells directly modulates glycolysis in vitro and in vivo

BACKGROUND

Glycolytic flux is regulated by the energy demands of the cell. Upregulated glycolysis in cancer cells may therefore result from increased demand for adenosine triphosphate (ATP), however it is unknown what this extra ATP turnover is used for. We hypothesise that an important contribution to the increased glycolytic flux in cancer cells results from the ATP demand of Na+/K+-ATPase (NKA) due to altered sodium ion homeostasis in cancer cells.

METHODS

Live whole-cell measurements of intracellular sodium [Na+]i were performed in three human breast cancer cells (MDA-MB-231, HCC1954, MCF-7), in murine breast cancer cells (4T1), and control human epithelial cells MCF-10A using triple quantum filtered 23Na nuclear magnetic resonance (NMR) spectroscopy. Glycolytic flux was measured by 2H NMR to monitor conversion of [6,6-2H2]D-glucose to [2H]-labelled L-lactate at baseline and in response to NKA inhibition with ouabain. Intracellular [Na+]i was titrated using isotonic buffers with varying [Na+] and [K+] and introducing an artificial Na+ plasma membrane leak using the ionophore gramicidin-A. Experiments were carried out in parallel with cell viability assays, 1H NMR metabolomics of intracellular and extracellular metabolites, extracellular flux analyses and in vivo measurements in a MDA-MB-231 human-xenograft mouse model using 2-deoxy-2-[18F]fluoroglucose (18F-FDG) positron emission tomography (PET).

RESULTS

Intracellular [Na+]i was elevated in human and murine breast cancer cells compared to control MCF-10A cells. Acute inhibition of NKA by ouabain resulted in elevated [Na+]i and inhibition of glycolytic flux in all three human cancer cells which are ouabain sensitive, but not in the murine cells which are ouabain resistant. Permeabilization of cell membranes with gramicidin-A led to a titratable increase of [Na+]i in MDA-MB-231 and 4T1 cells and a Na+-dependent increase in glycolytic flux. This was attenuated with ouabain in the human cells but not in the murine cells. 18FDG PET imaging in an MDA-MB-231 human-xenograft mouse model recorded lower 18FDG tumour uptake when treated with ouabain while murine tissue uptake was unaffected.

CONCLUSIONS

Glycolytic flux correlates with Na+-driven NKA activity in breast cancer cells, providing evidence for the 'centrality of the [Na+]i-NKA nexus' in the mechanistic basis of the Warburg effect.

Ranolazine: a potential anti-metastatic drug targeting voltage-gated sodium channels

BACKGROUND

Multi-faceted evidence from a range of cancers suggests strongly that de novo expression of voltage-gated sodium channels (VGSCs) plays a significant role in driving cancer cell invasiveness. Under hypoxic conditions, common to growing tumours, VGSCs develop a persistent current (INaP) which can be blocked selectively by ranolazine.

METHODS

Several different carcinomas were examined. We used data from a range of experimental approaches relating to cellular invasiveness and metastasis. These were supplemented by survival data mined from cancer patients.

RESULTS

In vitro, ranolazine inhibited invasiveness of cancer cells especially under hypoxia. In vivo, ranolazine suppressed the metastatic abilities of breast and prostate cancers and melanoma. These data were supported by a major retrospective epidemiological study on breast, colon and prostate cancer patients. This showed that risk of dying from cancer was reduced by ca.60% among those taking ranolazine, even if this started 4 years after the diagnosis. Ranolazine was also shown to reduce the adverse effects of chemotherapy on heart and brain. Furthermore, its anti-cancer effectiveness could be boosted by co-administration with other drugs.

CONCLUSIONS

Ranolazine, alone or in combination with appropriate therapies, could be reformulated as a safe anti-metastatic drug offering many potential advantages over current systemic treatment modalities.

Voltage-gated sodium channels, sodium transport and progression of solid tumours

Sodium (Na+) concentration in solid tumours of different origin is highly dysregulated, and this corresponds to the aberrant expression of Na+ transporters. In particular, the α subunits of voltage gated Na+ channels (VGSCs) raise intracellular Na+ concentration ([Na+]i) in malignant cells, which influences the progression of solid tumours, predominantly driving cancer cells towards a more aggressive and metastatic phenotype. Conversely, re-expression of VGSC β subunits in cancer cells can either enhance tumour progression or promote anti-tumourigenic properties. Metastasis is the leading cause of cancer-related mortality, highlighting an important area of research which urgently requires improved therapeutic interventions. Here, we review the extent to which VGSC subunits are dysregulated in solid tumours, and consider the implications of such dysregulation on solid tumour progression. We discuss current understanding of VGSC-dependent mechanisms underlying increased invasive and metastatic potential of solid tumours, and how the complex relationship between the tumour microenvironment (TME) and VGSC expression may further drive tumour progression, in part due to the interplay of infiltrating immune cells, cancer-associated fibroblasts (CAFs) and insufficient supply of oxygen (hypoxia). Finally, we explore past and present clinical trials that investigate utilising existing VGSC modulators as potential pharmacological options to support adjuvant chemotherapies to prevent cancer recurrence. Such research demonstrates an exciting opportunity to repurpose therapeutics in order to improve the disease-free survival of patients with aggressive solid tumours.

Voltage-gated sodium channels: from roles and mechanisms in the metastatic cell behavior to clinical potential as therapeutic targets

During the second half of the last century, the prevalent knowledge recognized the voltage-gated sodium channels (VGSCs) as the proteins responsible for the generation and propagation of action potentials in excitable cells. However, over the last 25 years, new non-canonical roles of VGSCs in cancer hallmarks have been uncovered. Their dysregulated expression and activity have been associated with aggressive features and cancer progression towards metastatic stages, suggesting the potential use of VGSCs as cancer markers and prognostic factors. Recent work has elicited essential information about the signalling pathways modulated by these channels: coupling membrane activity to transcriptional regulation pathways, intracellular and extracellular pH regulation, invadopodia maturation, and proteolytic activity. In a promising scenario, the inhibition of VGSCs with FDA-approved drugs as well as with new synthetic compounds, reduces cancer cell invasion in vitro and cancer progression in vivo. The purpose of this review is to present an update regarding recent advances and ongoing efforts to have a better understanding of molecular and cellular mechanisms on the involvement of both pore-forming α and auxiliary β subunits of VGSCs in the metastatic processes, with the aim at proposing VGSCs as new oncological markers and targets for anticancer treatments.

SCN5A channelopathy: arrhythmia, cardiomyopathy, epilepsy and beyond

Influx of sodium ions through voltage-gated sodium channels in cardiomyocytes is essential for proper electrical conduction within the heart. Both acquired conditions associated with sodium channel dysfunction (myocardial ischaemia, heart failure) as well as inherited disorders secondary to mutations in the gene SCN5A encoding for the cardiac sodium channel Nav1.5 are associated with life-threatening arrhythmias. Research in the last decade has uncovered the complex nature of Nav1.5 distribution, function, in particular within distinct subcellular subdomains of cardiomyocytes. Nav1.5-based channels furthermore display previously unrecognized non-electrogenic actions and may impact on cardiac structural integrity, leading to cardiomyopathy. Moreover, SCN5A and Nav1.5 are expressed in cell types other than cardiomyocytes as well as various extracardiac tissues, where their functional role in, e.g. epilepsy, gastrointestinal motility, cancer and the innate immune response is increasingly investigated and recognized. This review provides an overview of these novel insights and how they deepen our mechanistic knowledge on SCN5A channelopathies and Nav1.5 (dys)function. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

Morphoceuticals: perspectives for discovery of drugs targeting anatomical control mechanisms in regenerative medicine, cancer and aging

Morphoceuticals are a new class of interventions that target the setpoints of anatomical homeostasis for efficient, modular control of growth and form. Here, we focus on a subclass: electroceuticals, which specifically target the cellular bioelectrical interface. Cellular collectives in all tissues form bioelectrical networks via ion channels and gap junctions that process morphogenetic information, controlling gene expression and allowing cell networks to adaptively and dynamically control growth and pattern formation. Recent progress in understanding this physiological control system, including predictive computational models, suggests that targeting bioelectrical interfaces can control embryogenesis and maintain shape against injury, senescence and tumorigenesis. We propose a roadmap for drug discovery focused on manipulating endogenous bioelectric signaling for regenerative medicine, cancer suppression and antiaging therapeutics. Teaser: By taking advantage of the native problem-solving competencies of cells and tissues, a new kind of top-down approach to biomedicine becomes possible. Bioelectricity offers an especially tractable interface for interventions targeting the software of life for regenerative medicine applications.

Sodium channel-inhibiting drugs and cancer-specific survival: a population-based study of electronic primary care data

OBJECTIVES

Antiepileptic and antiarrhythmic drugs inhibit voltage-gated sodium (Na+) channels (VGSCs), and preclinical studies show that these medications reduce tumour growth, invasion and metastasis. We investigated the association between VGSC inhibitor use and survival in patients with breast, bowel and prostate cancer.

DESIGN

Retrospective cohort study.

SETTING

Individual electronic primary healthcare records extracted from the Clinical Practice Research Datalink.

PARTICIPANTS

Records for 132 996 patients with a diagnosis of breast, bowel or prostate cancer.

OUTCOME MEASURES

Adjusted Cox proportional hazards regression was used to analyse cancer-specific survival associated with exposure to VGSC inhibitors. Exposure to non-VGSC-inhibiting antiepileptic medication and other non-VGSC blockers were also considered. Drug exposure was treated as a time-varying covariate to account for immortal time bias.

RESULTS

During 1 002 225 person-years of follow-up, there were 42 037 cancer-specific deaths. 53 724 (40.4%) patients with cancer had at least one prescription for a VGSC inhibitor of interest. Increased risk of cancer-specific mortality was associated with exposure to this group of drugs (HR 1.59, 95% CI 1.56 to 1.63, p<0.001). This applied to VGSC-inhibiting tricyclic antidepressants (HR 1.61, 95% CI 1.50 to 1.65, p<0.001), local anaesthetics (HR 1.49, 95% CI 1.43 to 1.55, p<0.001) and anticonvulsants (HR 1.40, 95% CI 1.34 to 1.48, p<0.001) and persisted in sensitivity analyses. In contrast, exposure to VGSC-inhibiting class 1c and 1d antiarrhythmics was associated with significantly improved cancer-specific survival (HR 0.75, 95% CI 0.64 to 0.88, p<0.001 and HR 0.54, 95% CI 0.33 to 0.88, p=0.01, respectively).

CONCLUSIONS

Association between VGSC inhibitor use and mortality in patients with cancer varies according to indication. Exposure to VGSC-inhibiting antiarrhythmics, but not anticonvulsants, supports findings from preclinical data, with improved survival. However, additional confounding factors may underlie these associations, highlighting the need for further study.

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.

Neonatal NaV 1.5: Pharmacological distinctiveness of a cancer-related voltage-gated sodium channel splice variant

BACKGROUND AND PURPOSE

Voltage-gated sodium (Na_V ) channels are expressed de novo in carcinomas where their activity promotes invasiveness. Breast and colon cancer cells express the neonatal splice variant of Na_V 1.5 (nNa_V 1.5) which has several amino acid substitutions in the domain I voltage-sensor compared to its adult counterpart (aNa_V 1.5). This study aimed to determine whether nNa_V 1.5 could be distinguished pharmacologically from aNa_V 1.5.

EXPERIMENTAL APPROACH

Cells expressing either nNa_V 1.5 or aNa_V 1.5 were exposed to small-molecule inhibitors, an antibody or natural toxins, and changes in electrophysiological parameters were measured. Stable expression in EBNA cells and transient expression in Xenopus laevis oocytes were used. Currents were recorded by whole-cell patch clamp and two-electrode voltage-clamp, respectively.

KEY RESULTS

Several clinically-used blockers of Na_v channels (lidocaine, procaine, phenytoin, mexiletine, ranolazine and riluzole) could not distinguish between nNa_V 1.5 or aNa_V 1.5. On the other hand, two tarantula toxins (HaTx and ProTx-II) and a polyclonal antibody (NESOpAb) preferentially inhibited currents elicited by either nNa_V 1.5 or aNa_V 1.5 by binding to the spliced region of the channel. Furthermore, the amino acid residue at position 211 (aspartate in aNa_V 1.5/lysine in nNa_V 1.5), i.e. the charge reversal in the spliced region of the channel, played a key role in the selectivity especially in the antibody binding.

CONCLUSION AND IMPLICATIONS

We conclude that the cancer-related nNa_V 1.5 channel can be distinguished pharmacologically from its nearest neighbour, aNa_V 1.5. Thus, it may be possible to design small molecules as anti-metastatic drugs for non-toxic therapy of nNa_V 1.5-expressing carcinomas.

Pharmacological and nutritional targeting of voltage-gated sodium channels in the treatment of cancers

Voltage-gated sodium (NaV) channels, initially characterized in excitable cells, have been shown to be aberrantly expressed in non-excitable cancer tissues and cells from epithelial origins such as in breast, lung, prostate, colon, and cervix, whereas they are not expressed in cognate non-cancer tissues. Their activity was demonstrated to promote aggressive and invasive potencies of cancer cells, both in vitro and in vivo, whereas their deregulated expression in cancer tissues has been associated with metastatic progression and cancer-related death. This review proposes NaV channels as pharmacological targets for anticancer treatments providing opportunities for repurposing existing NaV-inhibitors or developing new pharmacological and nutritional interventions.

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.

Towards an Integral Therapeutic Protocol for Breast Cancer Based upon the New H+-Centered Anticancer Paradigm of the Late Post-Warburg Era

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H+) dynamics of cancer, allows for the understanding and integration of the many dualisms, confusions, and paradoxes of the disease. The new H+-related, wide-ranging model can embrace, from a unique perspective, the many aspects of the disease and, at the same time, therapeutically interfere with most, if not all, of the hallmarks of cancer known to date. The pH-related armamentarium available for the treatment of BC reviewed here may be beneficial for all types and stages of the disease. In this vein, we have attempted a megasynthesis of traditional and new knowledge in the different areas of breast cancer research and treatment based upon the wide-ranging approach afforded by the hydrogen ion dynamics of cancer. The concerted utilization of the pH-related drugs that are available nowadays for the treatment of breast cancer is advanced.

Predicting cardiac electrical response to sodium-channel blockade and Brugada syndrome using polygenic risk scores

Aims

Sodium-channel blockers (SCBs) are associated with arrhythmia, but variability of cardiac electrical response remains unexplained. We sought to identify predictors of ajmaline-induced PR and QRS changes and Type I Brugada syndrome (BrS) electrocardiogram (ECG).

Methods and results

In 1368 patients that underwent ajmaline infusion for suspected BrS, we performed measurements of 26 721 ECGs, dose–response mixed modelling and genotyping. We calculated polygenic risk scores (PRS) for PR interval (PRS_PR), QRS duration (PRS_QRS), and Brugada syndrome (PRS_BrS) derived from published genome-wide association studies and used regression analysis to identify predictors of ajmaline dose related PR change (slope) and QRS slope. We derived and validated using bootstrapping a predictive model for ajmaline-induced Type I BrS ECG. Higher PRS_PR, baseline PR, and female sex are associated with more pronounced PR slope, while PRS_QRS and age are positively associated with QRS slope (P < 0.01 for all). PRS_BrS, baseline QRS duration, presence of Type II or III BrS ECG at baseline, and family history of BrS are independently associated with the occurrence of a Type I BrS ECG, with good predictive accuracy (optimism-corrected C-statistic 0.74).

Conclusion

We show for the first time that genetic factors underlie the variability of cardiac electrical response to SCB. PRS_BrS, family history, and a baseline ECG can predict the development of a diagnostic drug-induced Type I BrS ECG with clinically relevant accuracy. These findings could lead to the use of PRS in the diagnosis of BrS and, if confirmed in population studies, to identify patients at risk for toxicity when given SCB.

Targeting Ion Channels for Cancer Treatment: Current Progress and Future Challenges

Ion channels are key regulators of cancer cell pathophysiology. They contribute to a variety of processes such as maintenance of cellular osmolarity and membrane potential, motility (via interactions with the cytoskeleton), invasion, signal transduction, transcriptional activity and cell cycle progression, leading to tumour progression and metastasis. Ion channels thus represent promising targets for cancer therapy. Ion channels are attractive targets because many of them are expressed at the plasma membrane and a broad range of existing inhibitors are already in clinical use for other indications. However, many of the ion channels identified in cancer cells are also active in healthy normal cells, so there is a risk that certain blockers may have off-target effects on normal physiological function. This review describes recent research advances into ion channel inhibitors as anticancer therapeutics. A growing body of evidence suggests that a range of existing and novel Na⁺, K⁺, Ca²⁺ and Cl^- channel inhibitors may be effective for suppressing cancer cell proliferation, migration and invasion, as well as enhancing apoptosis, leading to suppression of tumour growth and metastasis, either alone or in combination with standard-of-care therapies. The majority of evidence to date is based on preclinical in vitro and in vivo studies, although there are several examples of ion channel-targeting strategies now reaching early phase clinical trials. Given the strong links between ion channel function and regulation of tumour growth, metastasis and chemotherapy resistance, it is likely that further work in this area will facilitate the development of new therapeutic approaches which will reach the clinic in the future.

The Functional Role of Voltage-Gated Sodium Channel Nav1.5 in Metastatic Breast Cancer

Voltage-gated sodium channels (VGSCs), which are abnormally expressed in various types of cancers such as breast cancer, prostate cancer, lung cancer, and cervical cancer, are involved in the metastatic process of invasion and migration. Nav1.5 is a pore-forming α subunit of VGSC encoded by SCN5A. Various studies have demonstrated that Nav1.5, often as its neonatal splice form, is highly expressed in metastatic breast cancer cells. Abnormal activation and expression of Nav1.5 trigger a variety of cellular mechanisms, including changing H+ efflux, promoting epithelial-to-mesenchymal transition (EMT) and the expression of cysteine cathepsin, to potentiate the metastasis and invasiveness of breast cancer cells in vitro and in vivo. Here, we systematically review the latest available data on the pro-metastatic effect of Nav1.5 and its underlying mechanisms in breast cancer. We summarize the factors affecting Nav1.5 expression in breast cancer cells, and discuss the potential of Nav1.5 blockers serving as candidates for breast cancer treatment.

Ion Channels in Lung Cancer

Ion channels are a major class of membrane proteins that play central roles in signaling within and among cells, as well as in the coupling of extracellular events with cellular responses. Dysregulated ion channel activity plays a causative role in many diseases including cancer. Here, we will review their role in lung cancer. Lung cancer is one of the most frequently diagnosed cancers, and it causes the highest number of deaths of all cancer types. The overall 5-year survival rate of lung cancer patients is only 19% and decreases to 5% when patients are diagnosed with stage IV. Thus, new therapeutical strategies are urgently needed. The important contribution of ion channels to the progression of various types of cancer has been firmly established so that ion channel-based therapeutic concepts are currently developed. Thus far, the knowledge on ion channel function in lung cancer is still relatively limited. However, the published studies clearly show the impact of ion channel inhibitors on a number of cellular mechanisms underlying lung cancer cell aggressiveness such as proliferation, migration, invasion, cell cycle progression, or adhesion. Additionally, in vivo experiments reveal that ion channel inhibitors diminish tumor growth in mice. Furthermore, some studies give evidence that ion channel inhibitors can have an influence on the resistance or sensitivity of lung cancer cells to common chemotherapeutics such as paclitaxel or cisplatin.

Sodium homeostasis in the tumour microenvironment

The concentration of sodium ions (Na+) is raised in solid tumours and can be measured at the cellular, tissue and patient levels. At the cellular level, the Na+ gradient across the membrane powers the transport of H+ ions and essential nutrients for normal activity. The maintenance of the Na+ gradient requires a large proportion of the cell's ATP. Na+ is a major contributor to the osmolarity of the tumour microenvironment, which affects cell volume and metabolism as well as immune function. Here, we review evidence indicating that Na+ handling is altered in tumours, explore our current understanding of the mechanisms that may underlie these alterations and consider the potential consequences for cancer progression. Dysregulated Na+ balance in tumours may open opportunities for new imaging biomarkers and re-purposing of drugs for treatment.

In Vivo Evidence for Voltage-Gated Sodium Channel Expression in Carcinomas and Potentiation of Metastasis

A wide body of evidence suggests that voltage-gated sodium channels (VGSCs) are expressed de novo in several human carcinomas where channel activity promotes a variety of cellular behaviours integral to the metastatic cascade. These include directional motility (including galvanotaxis), pH balance, extracellular proteolysis, and invasion. Contrary to the substantial in vitro data, however, evidence for VGSC involvement in the cancer process in vivo is limited. Here, we critically assess, for the first time, the available in vivo evidence, hierarchically from mRNA level to emerging clinical aspects, including protein-level studies, electrolyte content, animal tests, and clinical imaging. The evidence strongly suggests that different VGSC subtypes (mainly Nav1.5 and Nav1.7) are expressed de novo in human carcinoma tissues and generally parallel the situation in vitro. Consistent with this, tissue electrolyte (sodium) levels, quantified by clinical imaging, are significantly higher in cancer vs. matched non-cancer tissues. These are early events in the acquisition of metastatic potential by the cancer cells. Taken together, the multi-faceted evidence suggests that the VGSC expression has clinical (diagnostic and therapeutic) potential as a prognostic marker, as well as an anti-metastatic target. The distinct advantages offered by the VGSC include especially (1) its embryonic nature, demonstrated most clearly for the predominant neonatal Nav1.5 expression in breast and colon cancer, and (2) the specifically druggable persistent current that VGSCs develop under hypoxic conditions, as in growing tumours, which promotes invasiveness and metastasis.

Antiarrhythmic drug usage and prostate cancer: a population-based cohort study

Even though the relationship between antiarrhythmic drug usage and subsequent prostate cancer (PCa) risk has recently been highlighted, relevant findings in the previous literature are still inconsistent. In addition, very few studies have attempted to investigate the association between sodium channel blockers or potassium channel blockers for arrhythmia and the subsequent PCa risk. Therefore, this cohort study aimed to find the relationship between antiarrhythmic drug usage and the subsequent PCa risk using a population-based dataset. The data used in this study were derived from the Longitudinal Health Insurance Database 2005, Taiwan, China. We respectively identified 9988 sodium channel blocker users, 3663 potassium channel blocker users, 65 966 beta-blocker users, 23 366 calcium channel blockers users, and 7031 digoxin users as the study cohorts. The matched comparison cohorts (one comparison subject for each antiarrhythmic drug user) were selected from the same dataset. Each patient was tracked for a 5-year period to define those who were subsequently diagnosed with PCa. After adjusting for sociodemographic characteristics, comorbidities, and age, Cox proportional hazard regressions found that the hazard ratio (HR) of subsequent PCa for sodium channel blocker users was 1.12 (95% confidence interval [CI]: 0.84–1.50), for potassium channel blocker users was 0.89 (95% CI: 0.59–1.34), for beta-blocker users was 1.08 (95% CI: 0.96–1.22), for calcium channel blocker users was 1.14 (95% CI: 0.95–1.36), and for digoxin users was 0.89 (95% CI: 0.67–1.18), compared to their matched nonusers. We concluded that there were no statistical associations between different types of antiarrhythmic drug usage and subsequent PCa risk.

Emerging roles for multifunctional ion channel auxiliary subunits in cancer

Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.

Immuno-Oncology: Emerging Targets and Combination Therapies

Host immunity recognizes and eliminates most early tumor cells, yet immunological checkpoints, exemplified by CTLA-4, PD-1, and PD-L1, pose a significant obstacle to effective antitumor immune responses. T-lymphocyte co-inhibitory pathways influence intensity, inflammation and duration of antitumor immunity. However, tumors and their immunosuppressive microenvironments exploit them to evade immune destruction. Recent PD-1 checkpoint inhibitors yielded unprecedented efficacies and durable responses across advanced-stage melanoma, showcasing potential to replace conventional radiotherapy regimens. Neverthless, many clinical problems remain in terms of efficacy, patient-to-patient variability, and undesirable outcomes and side effects. In this review, we evaluate recent advances in the immuno-oncology field and discuss ways forward. First, we give an overview of current immunotherapy modalities, involving mainy single agents, including inhibitor monoclonal antibodies (mAbs) targeting T-cell checkpoints of PD-1 and CTLA-4. However, neoantigen recognition alone cannot eliminate tumors effectively in vivo given their inherent complex micro-environment, heterogeneous nature and stemness. Then, based mainly upon CTLA-4 and PD-1 checkpoint inhibitors as a "backbone," we cover a range of emerging ("second-generation") therapies incorporating other immunotherapies or non-immune based strategies in synergistic combination. These include targeted therapies such as tyrosine kinase inhibitors, co-stimulatory mAbs, bifunctional agents, epigenetic modulators (such as inhibitors of histone deacetylases or DNA methyltransferase), vaccines, adoptive-T-cell therapy, nanoparticles, oncolytic viruses, and even synthetic "gene circuits." A number of novel immunotherapy co-targets in pre-clinical development are also introduced. The latter include metabolic components, exosomes and ion channels. We discuss in some detail of the personalization of immunotherapy essential for ultimate maximization of clinical outcomes. Finally, we outline possible future technical and conceptual developments including realistic in vitro and in vivo models and inputs from physics, engineering, and artificial intelligence. We conclude that the breadth and quality of immunotherapeutic approaches and the types of cancers that can be treated will increase significantly in the foreseeable future.

Triple negative breast cancer: Emerging therapeutic modalities and novel combination therapies

Triple negative breast cancer (TNBC) is a complex and aggressive subtype of breast cancer which lacks oestrogen receptors, progesterone receptors and HER2 amplification, thereby making it difficult to target therapeutically. In addition, TNBC has the highest rates of metastatic disease and the poorest overall survival of all breast cancer subtypes. Resultantly, development of targeted therapies for TNBC is urgently needed. Recent efforts aimed at molecular characterisation of TNBCs have revealed various emerging therapeutic targets including PARP1, receptor and non-receptor tyrosine kinases, immune-checkpoints, androgen receptor and epigenetic proteins. Key successes include that of the PARP inhibitor, olaparib, which prolonged progression-free survival in a trial of BRCA-mutated breast cancer and for which clinical approval (in this setting) appears imminent. Nevertheless, the heterogeneity of TNBC has limited the clinical benefits of many trialled therapies in 'unselected' patients. Further, drug resistance develops following use of many targeted monotherapies due to upregulation of compensatory signalling pathways. In this review, we evaluate the current status of investigational targeted treatments and present evidence for the role of novel biomarkers and combination therapies in increasing response rates and circumventing drug-induced resistance. Additionally, we discuss promising novel targets in metastatic TNBC identified through preclinical and/or epidemiological studies.

Perioperative Anesthesia Care and Tumor Progression

This narrative review discusses the most recent up-to-date findings focused on the currently available "best clinical practice" regarding perioperative anesthesia care bundle factors and their effect on tumor progression. The main objective is to critically appraise the current literature on local anesthetics, regional outcome studies, opioids, and nonsteroidal anti-inflammatory drugs (NSAIDs) and their ability to decrease recurrence in patients undergoing cancer surgery. A brief discussion of additional topical perioperative factors relevant to the anesthesiologist including volatile and intravenous anesthetics, perioperative stress and anxiety, nutrition, and immune stimulation is included. The results of several recently published systematic reviews looking at the association between cancer recurrences and regional anesthesia have yielded inconclusive data and provide insufficient evidence regarding a definitive benefit of regional anesthesia. Basic science data suggests an anti tumor effect induced by local anesthetics. New refined animal models show that opioids can safely be used for perioperative pain management. Preliminary evidence suggests that NSAIDs should be an essential part of multimodal analgesia. Volatile anesthetics have been shown to increase tumor formation, whereas preclinical and emerging clinical data from propofol indicate tumor protective qualities. The perioperative period in the cancer patient represents a unique environment where surgically mediated stress response leads to immune suppression. Regional anesthesia techniques when indicated in combination with multimodal analgesia that include NSAIDs, opioids, and local anesthetics to prevent the pathophysiologic effects of pain and neuroendocrine stress response should be viewed as an essential part of balanced anesthesia.

Ion Channels in Brain Metastasis

Breast cancer, lung cancer and melanoma exhibit a high metastatic tropism to the brain. Development of brain metastases severely worsens the prognosis of cancer patients and constrains curative treatment options. Metastasizing to the brain by cancer cells can be dissected in consecutive processes including epithelial-mesenchymal transition, evasion from the primary tumor, intravasation and circulation in the blood, extravasation across the blood-brain barrier, formation of metastatic niches, and colonization in the brain. Ion channels have been demonstrated to be aberrantly expressed in tumor cells where they regulate neoplastic transformation, malignant progression or therapy resistance. Moreover, many ion channel modulators are FDA-approved drugs and in clinical use proposing ion channels as druggable targets for future anti-cancer therapy. The present review article aims to summarize the current knowledge on the function of ion channels in the different processes of brain metastasis. The data suggest that certain channel types involving voltage-gated sodium channels, ATP-release channels, ionotropic neurotransmitter receptors and gap junction-generating connexins interfere with distinct processes of brain metastazation.

Sodium channel-inhibiting drugs and cancer survival: protocol for a cohort study using the CPRD primary care database

INTRODUCTION

Voltage-gated sodium channel (VGSC)-inhibiting drugs are commonly used to treat epilepsy and cardiac arrhythmia. VGSCs are also widely expressed in various cancers, including those of the breast, bowel and prostate. A number of VGSC-inhibiting drugs have been shown to inhibit cancer cell proliferation, invasion, tumour growth and metastasis in preclinical models, suggesting that VGSCs may be novel molecular targets for cancer treatment. Surprisingly, we previously found that prior exposure to VGSC-inhibiting drugs may be associated with reduced overall survival in patients with cancer, but we were unable to control for the cause of death or indication for prescription. The purpose of the present study is to interrogate a different database to further investigate the relationship between VGSC-inhibiting drugs and cancer-specific survival.

METHODS AND ANALYSIS

A cohort study using primary care data from the Clinical Practice Research Datalink database will include patients with diagnosis of breast, bowel and prostate cancer (13 000). The primary outcome will be cancer-specific survival from the date of cancer diagnosis. Cox proportional hazards regression will be used to compare survival of patients taking VGSC-inhibiting drugs (including antiepileptic drugs and class I antiarrhythmic agents) with patients with cancer not taking these drugs, adjusting for cancer type, age and sex. Drug exposure will be treated as a time-varying covariate to account for potential immortal time bias. Various sensitivity and secondary analyses will be performed.

ETHICS AND DISSEMINATION

The project has been reviewed and approved by the University of York Ethical Review Process. Results will be presented at an international conference and published in open access peer-reviewed journals according to the STROBE and RECORD guidelines.

Sodium Channels in Pain and Cancer: New Therapeutic Opportunities

Voltage-gated sodium channels (VGSCs) underpin electrical activity in the nervous system through action potential propagation. First predicted by the modeling studies of Hodgkin and Huxley, they were subsequently identified at the molecular level by groups led by Catterall and Numa. VGSC dysfunction has long been linked to neuronal and cardiac disorders with some nonselective sodium channel blockers in current use in the clinic. The lack of selectivity means that side effect issues are a major impediment to the use of broad spectrum sodium channel blockers. Nine different sodium channels are known to exist, and selective blockers are now being developed. The potential utility of these drugs to target diseases ranging from migraine, multiple sclerosis, muscle, and immune system disorders, to cancer and pain is being explored. Four channels are potential targets for pain disorders. This conclusion comes from mouse knockout studies and human mutations that prove the involvement of Nav1.3, Nav1.7, Nav1.8, and Nav1.9 in the development and maintenance of acute and chronic pain. In this chapter, we present a short overview of the possible role of Nav1.3, Nav1.7, Nav1.8, and Nav1.9 in human pain and the emerging and unexpected role of sodium channels in cancer pathogenesis.