Epidermal growth factor upregulates motility of Mat-LyLu rat prostate cancer cells partially via voltage-gated Na+ channel activity

Therapeutic targeting of voltage-gated sodium channel NaV1.7 for cancer metastasis

This review focuses on the expression and function of voltage-gated sodium channel subtype NaV1.7 in various cancers and explores its impact on the metastasis driving cell functions such as proliferation, migration, and invasiveness. An overview of its structural characteristics, drug binding sites, inhibitors and their likely mechanisms of action are presented. Despite the lack of clarity on the precise mechanism by which NaV1.7 contributes to cancer progression and metastasis; many studies have suggested a connection between NaV1.7 and proteins involved in multiple signaling pathways such as PKA and EGF/EGFR-ERK1/2. Moreover, the functional activity of NaV1.7 appears to elevate the expression levels of MACC1 and NHE-1, which are controlled by p38 MAPK activity, HGF/c-MET signaling and c-Jun activity. This cascade potentially enhances the secretion of extracellular matrix proteases, such as MMPs which play critical roles in cell migration and invasion activities. Furthermore, the NaV1.7 activity may indirectly upregulate Rho GTPases Rac activity, which is critical for cytoskeleton reorganization, cell adhesion, and actin polymerization. The relationship between NaV1.7 and cancer progression has prompted researchers to investigate the therapeutic potential of targeting NaV1.7 using inhibitors. The positive outcome of such studies resulted in the discovery of several inhibitors with the ability to reduce cancer cell migration, invasion, and tumor growth underscoring the significance of NaV1.7 as a promising pharmacological target for attenuating cancer cell proliferation and metastasis. The research findings summarized in this review suggest that the regulation of NaV1.7 expression and function by small molecules and/or by genetic engineering is a viable approach to discover novel therapeutics for the prevention and treatment of metastasis of cancers with elevated NaV1.7 expression.

Bioelectric pharmacology of cancer: A systematic review of ion channel drugs affecting the cancer phenotype

Cancer is a pernicious and pressing medical problem; moreover, it is a failure of multicellular morphogenesis that sheds much light on evolutionary developmental biology. Numerous classes of pharmacological agents have been considered as cancer therapeutics and evaluated as potential carcinogenic agents; however, these are spread throughout the primary literature. Here, we briefly review recent work on ion channel drugs as promising anti-cancer treatments and present a systematic review of the known cancer-relevant effects of 109 drugs targeting ion channels. The roles of ion channels in cancer are consistent with the importance of bioelectrical parameters in cell regulation and with the functions of bioelectric signaling in morphogenetic signals that act as cancer suppressors. We find that compounds that are well-known for having targets in the nervous system, such as voltage-gated ion channels, ligand-gated ion channels, proton pumps, and gap junctions are especially relevant to cancer. Our review suggests further opportunities for the repurposing of numerous promising candidates in the field of cancer electroceuticals.

Effect of Voltage-Gated Sodium Channel Inhibitors on the Metastatic Behavior of Prostate Cancer Cells: A Meta-Analysis

<b>Background and Objective:</b> Functional Voltage-Gated Sodium Channels (VGSCs) are expressed in metastatic prostate cancer (PCa) cells. A number of <i>in vitro</i> studies have evaluated the effect of functional VGSC expression on the metastatic cell behavior of PCa cells. This study aimed to evaluate the effect of VGSC inhibition on metastatic cell behavior in PCa cells by meta-analysis. <b>Materials and Methods:</b> Meta-analysis was performed on data taken from 13 publications that examined the effect of VGSC inhibitors on the metastatic cell behavior of metastatic PCa cells expressing functional VGSCs. The measure of effect was calculated according to the random effects model using mean differences and presented with a forest plot graph. Heterogeneity was checked using the Cochran's Q Test (Chi-square statistic) and the I² test statistic. In order to evaluate the objectivity, the funnels-plot graph was used. <b>Results:</b> The g value showing the effect size was calculated as 4.49 (95% CI = 5.35-3.62) in the experiments where Tetrodotoxin (TTX) was used, which has a very high specificity for VGSCs but is not licensed for clinical use. In experiments using licensed inhibitors Lamotrigine, Oxcarbazepine, Phenytoin, Ranolazine, Riluzole and Lidocaine, the g value was 1.37 (95 % CI = 2.02-0.71). Suppression of metastatic cell behavior in both subgroups is statistically significant (p<0.00001). <b>Conclusion:</b> Meta-analysis confirmed that VGSCs are an enhancing factor in the metastasis of PCa cells. The VGSCs appear to be an important target in the diagnosis and development of new treatment options in PCa.

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.

Neonatal Nav1.5 Protein Expression in Human Colorectal Cancer: Immunohistochemical Characterization and Clinical Evaluation

Voltage-gated Na+ channels (VGSCs) are expressed widely in human carcinomas and play a significant role in promoting cellular invasiveness and metastasis. However, human tissue-based studies and clinical characterization are lacking. In several carcinomas, including colorectal cancer (CRCa), the predominant VGSC is the neonatal splice variant of Nav1.5 (nNav1.5). The present study was designed to determine the expression patterns and clinical relevance of nNav1.5 protein in human CRCa tissues from patients with available clinicopathological history. The immunohistochemistry was made possible by the use of a polyclonal antibody (NESOpAb) specific for nNav1.5. The analysis showed that, compared with normal mucosa, nNav1.5 expression occurred in CRCa samples (i) at levels that were significantly higher and (ii) with a pattern that was more delineated (i.e., apical/basal or mixed). A surprisingly high level of nNav1.5 protein expression also occurred in adenomas, but this was mainly intracellular and diffuse. nNav1.5 showed a statistically significant association with TNM stage, highest expression being associated with TNM IV and metastatic status. Interestingly, nNav1.5 expression co-occurred with other biomarkers associated with metastasis, including hERG1, KCa3.1, VEGF-A, Glut1, and EGFR. Finally, univariate analysis showed that nNav1.5 expression had an impact on progression-free survival. We conclude (i) that nNav1.5 could represent a novel clinical biomarker ('companion diagnostic') useful to better stratify CRCa patients and (ii) that since nNav1.5 expression is functional, it could form the basis of anti-metastatic therapies including in combination with standard treatments.

Bioelectrical approaches to cancer as a problem of the scaling of the cellular self

One lens with which to understand the complex phenomenon of cancer is that of developmental biology. Cancer is the inevitable consequence of a breakdown of the communication that enables individual cells to join into computational networks that work towards large-scale, morphogenetic goals instead of more primitive, unicellular objectives. This perspective suggests that cancer may be a physiological disorder, not necessarily due to problems with the genetically-specified protein hardware. One aspect of morphogenetic coordination is bioelectric signaling, and indeed an abnormal bioelectric signature non-invasively reveals the site of incipient tumors in amphibian models. Functionally, a disruption of resting potential states triggers metastatic melanoma phenotypes in embryos with no genetic defects or carcinogen exposure. Conversely, optogenetic or molecular-biological modulation of bioelectric states can override powerful oncogenic mutations and prevent or normalize tumors. The bioelectrically-mediated information flows that harness cells toward body-level anatomical outcomes represent a very attractive and tractable endogenous control system, which is being targeted by emerging approaches to cancer.

Brain-to-brain communication: the possible role of brain electromagnetic fields (As a Potential Hypothesis)

Up now, the communication between brains of different humans or animals has been confirmed and confined by the sensory medium and motor facilities of body. Recently, direct brain-to-brain communication (DBBC) outside the conventional five senses has been verified between animals and humans. Nevertheless, no empirical studies or serious discussion have been performed to elucidate the mechanism behind this process. The validation of DBBC has been documented via recording similar pattern of action potentials occurring in the brain cortex of two animals. With regard to action potentials in brain neurons, the magnetic field resulting from the action potentials created in neurons is one of the tools where the brain of one animal can affect the brain of another. It has been shown that different animals, even humans, have the power to understand the magnetic field. Cryptochrome, which exists in the retina and in different regions of the brain, has been confirmed to be able to perceive magnetic fields and convert magnetic fields to action potentials. Recently, iron particles (Fe₃O₄) believed to be functioning as magnets have been found in various parts of the brain, and are postulated as magnetic field receptors. Newly developed supersensitive magnetic sensors made of iron magnets that can sense the brain's magnetic field have suggested the idea that these Fe₃O₄ particles or magnets may be capable of perceiving the brain's extremely weak magnetic field. The present study suggests that it is possible the extremely week magnetic field in one animal's brain to transmit vital and accurate information to another animal's brain.

Riluzole: Anti-invasive effects on rat prostate cancer cells under normoxic and hypoxic conditions

Anti-invasive effects of riluzole and ranolazine, a neuro-protectant and an anti-anginal drug, respectively, on Mat-LyLu rat prostate cancer (PCa) cells were tested in vitro (a) at non-toxic doses and (b) under both normoxic and hypoxic conditions, the latter common to growing tumours. Tetrodotoxin (TTX) was used as a positive control. Hypoxia had no effect on cell viability but reduced growth at 48 hours. Riluzole (5 μmol/L) or ranolazine (20 μmol/L) had no effect on cell viability or growth under normoxia or hypoxia over 24 hours. Matrigel invasion was not affected by hypoxia but inhibited by TTX, ranolazine and riluzole under a range of conditions. The expression of Nav1.7 mRNA, the prevailing, pro-invasive voltage-gated sodium channel α-subunit (VGSCα), was up-regulated by hypoxia. Riluzole had no effect on Nav1.7 mRNA expression in normoxia but significantly reduced it in hypoxia. VGSCα protein expression in plasma membrane was reduced in hypoxia; riluzole increased it but only under hypoxia. It was concluded (a) that riluzole and ranolazine have anti-invasive effects on rat PCa cells and (b) that Nav1.7 mRNA and protein expression can be modulated by riluzole under hypoxia. Overall, therefore, riluzole and ranolazine may ultimately be "repurposed" as anti-metastatic drugs against PCa.

Bioelectric Control of Metastasis in Solid Tumors

As the leading cause of death in cancer, there is an urgent need to develop treatments to target the dissemination of primary tumor cells to secondary organs, known as metastasis. Bioelectric signaling has emerged in the last century as an important controller of cell growth, and with the development of current molecular tools we are now beginning to identify its role in driving cell migration and metastasis in a variety of cancer types. This review summarizes the currently available research for bioelectric signaling in solid tumor metastasis. We review the steps of metastasis and discuss how these can be controlled by bioelectric cues at the level of a cell, a population of cells, and the tissue. The role of ion channel, pump, and exchanger activity and ion flux is discussed, along with the importance of the membrane potential and the relationship between ion flux and membrane potential. We also provide an overview of the evidence for control of metastasis by external electric fields (EFs) and draw from examples in embryogenesis and regeneration to discuss the implications for endogenous EFs. By increasing our understanding of the dynamic properties of bioelectric signaling, we can develop new strategies that target metastasis to be translated into the clinic.

The Emerging Role of Voltage-Gated Sodium Channels in Tumor Biology

Voltage-gated sodium channels (VGSCs) are transmembrane proteins which function as gates that control the flux of ions across the cell membrane. They are key ion channels for action potentials in excitable tissues and have important physiological functions. Abnormal function of VGSCs will lead to dysfunction of the body and trigger a variety of diseases. Various studies have demonstrated the participation of VGSCs in the progression of different tumors, such as prostate cancer, cervical cancer, breast cancer, and others, linking VGSC to the invasive capacity of tumor cells. However, it is still unclear whether the VGSC regulate the malignant biological behavior of tumors. Therefore, this paper systematically addresses the latest research progress on VGSCs subunits and tumors and the underlying mechanisms, and it summarizes the potential of VGSCs subunits to serve as potential targets for tumor diagnosis and treatment.

Dual roles of voltage-gated sodium channels in development and cancer

Voltage-gated Na(+) channels (VGSCs) are heteromeric protein complexes containing pore-forming α subunits together with non-pore-forming β subunits. There are nine α subunits, Nav1.1-Nav1.9, and four β subunits, β1-β4. The β subunits are multifunctional, modulating channel activity, cell surface expression, and are members of the immunoglobulin superfamily of cell adhesion molecules. VGSCs are classically responsible for action potential initiation and conduction in electrically excitable cells, including neurons and muscle cells. In addition, through the β1 subunit, VGSCs regulate neurite outgrowth and pathfinding in the developing central nervous system. Reciprocal signalling through Nav1.6 and β1 collectively regulates Na(+) current, electrical excitability and neurite outgrowth in cerebellar granule neurons. Thus, α and β subunits may have diverse interacting roles dependent on cell/tissue type. VGSCs are also expressed in non-excitable cells, including cells derived from a number of types of cancer. In cancer cells, VGSC α and β subunits regulate cellular morphology, migration, invasion and metastasis. VGSC expression associates with poor prognosis in several studies. It is hypothesised that VGSCs are up-regulated in metastatic tumours, favouring an invasive phenotype. Thus, VGSCs may have utility as prognostic markers, and/or as novel therapeutic targets for reducing/preventing metastatic disease burden. VGSCs appear to regulate a number of key cellular processes, both during normal postnatal development of the CNS and during cancer metastasis, by a combination of conducting (i.e. via Na(+) current) and non-conducting mechanisms.

Nav1.5 regulates breast tumor growth and metastatic dissemination in vivo

Voltage-gated Na+ channels (VGSCs) mediate action potential firing and regulate adhesion and migration in excitable cells. VGSCs are also expressed in cancer cells. In metastatic breast cancer (BCa) cells, the Nav1.5 α subunit potentiates migration and invasion. In addition, the VGSC-inhibiting antiepileptic drug phenytoin inhibits tumor growth and metastasis. However, the functional activity of Nav1.5 and its specific contribution to tumor progression in vivo has not been delineated. Here, we found that Nav1.5 is up-regulated at the protein level in BCa compared with matched normal breast tissue. Na+ current, reversibly blocked by tetrodotoxin, was retained in cancer cells in tumor tissue slices, thus directly confirming functional VGSC activity in vivo. Stable down-regulation of Nav1.5 expression significantly reduced tumor growth, local invasion into surrounding tissue, and metastasis to liver, lungs and spleen in an orthotopic BCa model. Nav1.5 down-regulation had no effect on cell proliferation or angiogenesis within the in tumors, but increased apoptosis. In vitro, Nav1.5 down-regulation altered cell morphology and reduced CD44 expression, suggesting that VGSC activity may regulate cellular invasion via the CD44-src-cortactin signaling axis. We conclude that Nav1.5 is functionally active in cancer cells in breast tumors, enhancing growth and metastatic dissemination. These findings support the notion that compounds targeting Nav1.5 may be useful for reducing metastasis.

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

Metastasis is the leading cause of cancer-related deaths. Voltage-gated sodium channels (VGSCs) regulate invasion and metastasis. Several VGSC-inhibiting drugs reduce metastasis in murine cancer models. We aimed to test the hypothesis that patients taking VGSC-inhibiting drugs who developed cancer live longer than those not taking these drugs. A cohort study was performed on primary care data from the QResearch database, including patients with breast, bowel or prostate cancer. Cox proportional hazards regression was used to compare the survival from cancer diagnosis of patients taking VGSC-inhibiting drugs with those not exposed to these drugs. Median time to death was 9.7 years in the exposed group and 18.4 years in the unexposed group, and exposure to these medications significantly increased mortality. Thus, exposure to VGSC-inhibiting drugs associates with reduced survival in breast, bowel and prostate cancer patients. This finding is not consistent with the preclinical data. Despite the strengths of this study including the large sample size, the study is limited by missing information on potentially important confounders such as cancer stage, co-morbidities and cause of death. Further research, which is able to account for these confounding issues, is needed to investigate the relationship between VGSC-inhibiting drugs and cancer survival.

Blockade of voltage-gated sodium channels inhibits invasion of endocrine-resistant breast cancer cells

Voltage-gated Na⁺ channels (VGSCs) are membrane proteins which are normally expressed in excitable cells but have also been detected in cancer cells, where they are thought to be involved in malignancy progression. In this study we examined the ion current and expression profile of VGSC (Na_v1.5) in estrogen receptor (ER)-positive (MCF-7) and silenced (pII) breast cancer cells and its possible influence on their proliferation, motility and invasion. VGSC currents were analysed by whole cell patch clamp recording. Na_v1.5 expression and localization, in response to EGF stimulation, was examined by western blotting and immunofluorescence respectively. Cell invasion (under-agarose and Matrigel assays), motility (wound healing assay) and proliferation (MTT assay) were assessed in pII cells in response to VGSC blockers, phenytoin (PHT) and tetrodotoxin (TTX), or by siRNA knockdown of Na_v1.5. The effect of PHT and TTX on modulating EGF-induced phosphorylation of Akt and ERK1/2 was determined by western blotting. Total matrix metalloproteinase (MMP) was determined using a fluorometric-based activity assay. The level of various human proteases was detected by using proteome profiler array kit. VGSC currents were detected in pII cells, but were absent in MCF-7. Na_v1.5 showed cytoplasmic and perinuclear expression in both MCF-7 and pII cells, with enhanced expression upon EGF stimulation. Treatment of pII cells with PHT, TTX or siRNA significantly reduced invasion towards serum components and EGF, in part through reduction of P-ERK1/2 and proteases such as cathepsin E, kallikrein-10 and MMP-7, as well as total MMP activity. At high concentrations, PHT inhibited motility while TTX reduced cell proliferation. Pharmacological or genetic blockade of Na_v1.5 may serve as a potential anti-metastatic therapy for breast cancer.

cAMP/PKA Pathways and S56 Phosphorylation Are Involved in AA/PGE2-Induced Increases in rNaV1.4 Current

Arachidonic acid (AA) and its metabolites are important second messengers for ion channel modulation. The effects of extracellular application of AA and its non-metabolized analogue on muscle rNa_V1.4 Na⁺ current has been studied, but little is known about the effects of intracellular application of AA on this channel isoform. Here, we report that intracellular application of AA significantly augmented the rNa_V1.4 current peak without modulating the steady-state activation and inactivation properties of the rNa_V1.4 channel. These results differed from the effects of extracellular application of AA on rNa_V1.4 current. The effects of intracellular AA were mimicked by prostaglandin E₂ but not eicosatetraynoic acid (ETYA), the non-metabolized analogue of AA, and were eliminated by treatment with cyclooxygenase inhibitors, flufenamic acid, or indomethacin. AA/PGE₂-induced activation of rNa_V1.4 channels was mimicked by a cAMP analogue (db-cAMP) and eliminated by a PKA inhibitor, PKAi. Furthermore, inhibition of EP2 and EP4 (PGE₂ receptors) with AH6809 and AH23848 reduced the intracellular AA/PGE₂-induced increase of rNa_V1.4 current. Two mutated channels, rNa_V1.4S56A and rNa_V1.4T21A, were designed to investigate the role of predicted phosphorylation sites in the AA/PGE₂–mediated regulation of rNa_V1.4 currents. In rNa_V1.4S56A, the effects of intracellular db-cAMP, AA, and PGE₂ were significantly reduced. The results of the present study suggest that intracellular AA augments rNa_V1.4 current by PGE₂/EP receptor-mediated activation of the cAMP/PKA pathway, and that the S56 residue on the channel protein is important for this process.

Cancer surgery: how may anesthesia influence outcome?

OBJECTIVE

To review the published literature regarding the effects of anesthesia on cancer surgery to prevent tumor cell proliferation/migration or induce apoptosis.

BACKGROUND

Surgery is the main treatment for potentially curable solid tumors, but most cancer-related deaths in patients who have received previous surgical treatment are caused by metastatic disease. There is increasing evidence that anesthetic technique has the potential to affect long-term outcome after cancer surgery.

METHODS

This work reviews the English published literature that was obtained by performing a search of the PubMed database up to January 2014. We selected articles that provided evidence or reviewed the possible actions of anesthetics on cancer cells or the influence of anesthesia in recurrence/outcome.

RESULTS

Inhaled anesthetics induce immunosuppression and activate inflammatory cascade activation, whereas propofol has a protective action. Opioids might promote cancer recurrence and metastasis. In vitro and in vivo studies have demonstrated that local anesthetics inhibit proliferation and migration of cancer cells and induce apoptosis.

CONCLUSIONS

Anesthesiologists should follow current best clinical practice and include all strategies that effectively decrease pain and attenuate stress. Regional anesthesia and multimodal analgesia, adding anti-inflammatory drugs, play an unquestionable role in the control of perioperative pain and may improve recurrence-free survival.

Novel 1-(2-aryl-2-adamantyl)piperazine derivatives with antiproliferative activity

Novel 1-(2-aryl-2-adamantyl)piperazine derivatives have been synthesized and evaluated in vitro for their antitumor properties against HeLa cervical carcinoma, MDA MB 231 breast cancer, MIA PaCa2 pancreatic cancer, and NCI H1975 non-small cell lung cancer. The parent piperazine 6 was found to exhibit a reasonable activity toward the HeLa and MDA MB 231 tumor cell lines (IC50= 9.2 and 8.4 μΜ, respectively). Concurrent benzene ring C4-fluorination and piperidine acetylation of the piperazino NH of compound 6 resulted in the most active compound 13 of the series in both of the above cell lines (IC50=8.4 and 6.8 μΜ, respectively). Noticeably, compounds 6 and 13 exhibited a significantly low cytotoxicity level over the normal human cells HUVEC (Human Umbilical Vein Endothelial Cells) and NHDF (Normal Human Dermal Fibroblasts).

Exposure to sodium channel-inhibiting drugs and cancer survival: protocol for a cohort study using the QResearch primary care database

INTRODUCTION

Metastasis from solid tumours is associated with significant morbidity and mortality, and is the leading cause of cancer-related deaths. Voltage-gated sodium channels (VGSCs) are drug targets for the treatment of epilepsy. VGSCs are also present in cancer cells, where they regulate metastatic cell behaviours, including cellular movement and invasion. Treating cancer cells with the VGSC-inhibiting anticonvulsant phenytoin reduces cellular invasion and migration. Together, these suggest that VGSCs may be useful targets for inhibiting metastasis. The purpose of this study is to test the hypothesis that use of VGSC-inhibiting drugs will reduce metastasis, and therefore increase survival time in patients with cancer.

METHODS AND ANALYSIS

A cohort study based on primary care data from the QResearch database will include patients with one of the three common tumours: breast, bowel and prostate. The primary outcome will be overall survival from the date of cancer diagnosis. Cox proportional hazards regression will be used to compare the survival of patients with cancer taking VGSC-inhibiting drugs (including anticonvulsants and class I antiarrhythmic agents) with patients with cancer not exposed to these drugs, adjusting for age and sex. Exposure to VGSC-inhibiting drugs will be defined as having at least one prescription for these drugs prior to cancer diagnosis. High and low exposure groups will be identified based on the length of use. A number of sensitivity and secondary analyses will be conducted.

ETHICS AND DISSEMINATION

The protocol has been independently peer-reviewed and approved by the QResearch Scientific Board. The project has also been approved by the University of York Ethical Review Process. The results will be presented at international conferences and published in an open access peer-reviewed journal, in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria.

Alteration of bioelectrically-controlled processes in the embryo: a teratogenic mechanism for anticonvulsants

Maternal use of anticonvulsants during the first trimester of pregnancy has been associated with an elevated risk of major congenital malformations in the offspring. Whether the increased risk is caused by the specific pharmacological mechanisms of certain anticonvulsants, the underlying epilepsy, or common genetic or environmental risk factors shared by epilepsy and malformations has been controversial. We hypothesize that anticonvulsant therapies during pregnancy that attain more successful inhibition of neurotransmission might lead to both better seizure control in the mother and stronger alteration of bioelectrically-controlled processes in the embryo that result in structural malformations. We propose that development of pharmaceuticals that do not alter cell resting transmembrane voltage levels could result in safer drugs.

Melatonin protects rat cerebellar granule cells against electromagnetic field-induced increases in Na(+) currents through intracellular Ca(2+) release

Although melatonin (MT) has been reported to protect cells against oxidative damage induced by electromagnetic radiation, few reports have addressed whether there are other protective mechanisms. Here, we investigated the effects of MT on extremely low-frequency electromagnetic field (ELF-EMF)-induced Nav activity in rat cerebellar granule cells (GCs). Exposing cerebellar GCs to ELF-EMF for 60 min. significantly increased the Nav current (INa ) densities by 62.5%. MT (5 μM) inhibited the ELF-EMF-induced INa increase. This inhibitory effect of MT is mimicked by an MT2 receptor agonist and was eliminated by an MT2 receptor antagonist. The Nav channel steady-state activation curve was significantly shifted towards hyperpolarization by ELF-EMF stimulation but remained unchanged by MT in cerebellar GC that were either exposed or not exposed to ELF-EMF. ELF-EMF exposure significantly increased the intracellular levels of phosphorylated PKA in cerebellar GCs, and both MT and IIK-7 did not reduce the ELF-EMF-induced increase in phosphorylated PKA. The inhibitory effects of MT on ELF-EMF-induced Nav activity was greatly reduced by the calmodulin inhibitor KN93. Calcium imaging showed that MT did not increase the basal intracellular Ca(2+) level, but it significantly elevated the intracellular Ca(2+) level evoked by the high K(+) stimulation in cerebellar GC that were either exposed or not exposed to ELF-EMF. In the presence of ruthenium red, a ryanodine-sensitive receptor blocker, the MT-induced increase in intracellular calcium levels was reduced. Our data show for the first time that MT protects against neuronal INa that result from ELF-EMF exposure through Ca(2+) influx-induced Ca(2+) release.

Regulation of voltage-gated sodium channel expression in cancer: hormones, growth factors and auto-regulation

Although ion channels are increasingly being discovered in cancer cells in vitro and in vivo, and shown to contribute to different aspects and stages of the cancer process, much less is known about the mechanisms controlling their expression. Here, we focus on voltage-gated Na⁺ channels (VGSCs) which are upregulated in many types of carcinomas where their activity potentiates cell behaviours integral to the metastatic cascade. Regulation of VGSCs occurs at a hierarchy of levels from transcription to post-translation. Importantly, mainstream cancer mechanisms, especially hormones and growth factors, play a significant role in the regulation. On the whole, in major hormone-sensitive cancers, such as breast and prostate cancer, there is a negative association between genomic steroid hormone sensitivity and functional VGSC expression. Activity-dependent regulation by positive feedback has been demonstrated in strongly metastatic cells whereby the VGSC is self-sustaining, with its activity promoting further functional channel expression. Such auto-regulation is unlike normal cells in which activity-dependent regulation occurs mostly via negative feedback. Throughout, we highlight the possible clinical implications of functional VGSC expression and regulation in cancer.

Exposure to extremely low-frequency electromagnetic fields modulates Na+ currents in rat cerebellar granule cells through increase of AA/PGE2 and EP receptor-mediated cAMP/PKA pathway

Although the modulation of Ca²⁺ channel activity by extremely low-frequency electromagnetic fields (ELF-EMF) has been studied previously, few reports have addressed the effects of such fields on the activity of voltage-activated Na⁺ channels (Na_v). Here, we investigated the effects of ELF-EMF on Na_v activity in rat cerebellar granule cells (GCs). Our results reveal that exposing cerebellar GCs to ELF-EMF for 10–60 min significantly increased Na_v currents (I_Na) by 30–125% in a time- and intensity-dependent manner. The Na_v channel steady-state activation curve, but not the steady-state inactivation curve, was significantly shifted (by 5.2 mV) towards hyperpolarization by ELF-EMF stimulation. This phenomenon is similar to the effect of intracellular application of arachidonic acid (AA) and prostaglandin E₂ (PGE₂) on I_Na in cerebellar GCs. Increases in intracellular AA, PGE₂ and phosphorylated PKA levels in cerebellar GCs were observed following ELF-EMF exposure. Western blottings indicated that the Na_V 1.2 protein on the cerebellar GCs membrane was increased, the total expression levels of Na_V 1.2 protein were not affected after exposure to ELF-EMF. Cyclooxygenase inhibitors and PGE₂ receptor (EP) antagonists were able to eliminate this ELF-EMF-induced increase in phosphorylated PKA and I_Na. In addition, ELF-EMF exposure significantly enhanced the activity of PLA₂ in cerebellar GCs but did not affect COX-1 or COX-2 activity. Together, these data demonstrate for the first time that neuronal I_Na is significantly increased by ELF-EMF exposure via a cPLA2 AA PGE₂ EP receptors PKA signaling pathway.

Endogenous Voltage Potentials and the Microenvironment: Bioelectric Signals that Reveal, Induce and Normalize Cancer

Cancer may be a disease of geometry: a misregulation of the field of information that orchestrates individual cells' activities towards normal anatomy. Recent work identified molecular mechanisms underlying a novel system of developmental control: bioelectric gradients. Endogenous spatio-temporal differences in resting potential of non-neural cells provide instructive cues for cell regulation and complex patterning during embryogenesis and regeneration. It is now appreciated that these cues are an important layer of the dysregulation of cell: cell interactions that leads to cancer. Abnormal depolarization of resting potential (Vmem) is a convenient marker for neoplasia and activates a metastatic phenotype in genetically-normal cells in vivo. Moreover, oncogene expression depolarizes cells that form tumor-like structures, but is unable to form tumors if this depolarization is artificially prevented by misexpression of hyperpolarizing ion channels. Vmem triggers metastatic behaviors at considerable distance, mediated by transcriptional and epigenetic effects of electrically-modulated flows of serotonin and butyrate. While in vivo data on voltages in carcinogenesis comes mainly from the amphibian model, unbiased genetic screens and network profiling in rodents and human tissues reveal several ion channel proteins as bona fide oncogene and promising targets for cancer drug development. However, we propose that a focus on specific channel genes is just the tip of the iceberg. Bioelectric state is determined by post-translational gating of ion channels, not only from genetically-specified complements of ion translocators. A better model is a statistical dynamics view of spatial Vmem gradients. Cancer may not originate at the single cell level, since gap junctional coupling results in multi-cellular physiological networks with multiple stable attractors in bioelectrical state space. New medical applications await a detailed understanding of the mechanisms by which organ target morphology stored in real-time patterns of ion flows is perceived or mis-perceived by cells. Mastery of somatic voltage gradients will lead to cancer normalization or rebooting strategies, such as those that occur in regenerating and embryonic organs, resulting in transformative advances in basic biology and oncology.

Functional expression of the voltage-gated sodium channel, Nav1.7, underlies epidermal growth factor-mediated invasion in human [R1.S1] non-small cell lung cancer cells

Various ion channels are expressed in human cancers where they are intimately involved in proliferation, angiogenesis, invasion and metastasis. Expression of functional voltage-gated sodium channels (Nav) is implicated in the metastatic potential of breast, prostate, lung and colon cancer cells. However, the cellular mechanisms that regulate Nav expression in cancer remain largely unknown. Growth factors are attractive candidates; they not only play crucial roles in cancer progression but are also key regulators of ion channel expression and activity in non-cancerous cells. Here, we examine the role of epidermal growth factor receptor (EGFR) signalling and Nav in non-small cell lung carcinoma (NSCLC) cell lines. We show unequivocally, that functional expression of Nav1.7 promotes invasion in H460 NSCLC cells. Inhibition of Nav1.7 activity (tetrodotoxin), or, expression (small interfering RNA), reduces H460 cell invasion by up to 50%. Crucially, non-invasive wild type A549 cells lack functional Nav whereas exogenous over-expression of Nav1.7 is sufficient to promote TTX-sensitive invasion of these cells. EGF/EGFR signalling enhances proliferation, migration and invasion of H460 cells but we find that EGFR-mediated up-regulation of Nav1.7 specifically, is necessary for invasive behaviour in these cells. Examination of Nav1.7 expression at the mRNA, protein and functional levels further reveals that EGF/EGFR signalling via the ERK1/2 pathway controls transcriptional regulation of channel expression to promote cellular invasion. Immunohistochemistry of patient biopsies confirms the clinical relevance of Nav1.7 expression in NSCLC. Thus, Nav1.7 has significant potential as a novel target for therapeutic intervention and/or as a diagnostic/prognostic marker in NSCLC.

Voltage-gated sodium channels and metastatic disease

Voltage-gated Na (+) channels (VGSCs) are macromolecular protein complexes containing a pore-forming α subunit and smaller non-pore-forming β subunits. VGSCs are expressed in metastatic cells from a number of cancers. In these cells, Na (+) current carried by α subunits enhances migration, invasion and metastasis in vivo. In contrast, the β subunits mediate cellular adhesion and process extension. The prevailing hypothesis is that VGSCs are upregulated in cancer, in general favoring an invasive/metastatic phenotype, although the mechanisms are still not fully clear. Expression of the Nav 1.5 α subunit associates with poor prognosis in clinical breast cancer specimens, suggesting that VGSCs may have utility as prognostic markers for cancer progression. Furthermore, repurposing existing VGSC-blocking therapeutic drugs may provide a new strategy to improve outcomes in patients suffering from metastatic disease, which is the major cause of cancer-related deaths, and for which there is currently no cure.

Synthesis, σ₁, σ₂-receptors binding affinity and antiproliferative action of new C1-substituted adamantanes

The synthesis of N-{4-[a-(1-adamantyl)benzyl]phenyl}piperazines 2a-e is described. The in vitro antiproliferative activity of most compounds against main cancer cell lines is significant. The σ(1), σ(2)-receptors and sodium channels binding affinity of compounds 2 were investigated. One of the most active analogs, 2a, had an interesting in vivo anticancer profile against the BxPC-3 and Mia-Paca-2 pancreas cancer cell lines with caspase-3 activation, which was associated with an anagelsic activity against the neuropathic pain.

Arachidonic acid modulates Na+ currents by non-metabolic and metabolic pathways in rat cerebellar granule cells

AA (arachidonic acid), which possesses both neurotoxic and neurotrophic activities, has been implicated as a messenger in both physiological and pathophysiological processes. In the present study, we investigated the effects of both extracellular and intracellular application of AA on the activity of Na(V) (voltage-gated Na(+) channels) in rat cerebellar GCs (granule cells). The extracellular application of AA inhibited the resultant I(Na) (Na(V) current), wherein the current-voltage curve shifted to a negative voltage direction. Because this effect could be reproduced by treating the GCs with ETYA (eicosa-5,8,11,14-tetraynoic acid) or a membrane-impermeable analogue of AA, AA-CoA (arachidonoyl coenzyme A), we inferred that AA itself exerted the observed modulatory effects on I(Na). In contrast, intracellular AA significantly augmented the elicited I(Na) peak when the same protocol that was used for extracellular AA was followed. The observed I(Na) increase that was induced by intracellular AA was mimicked by the AA cyclo-oxygenase metabolite PGE(2) (prostaglandin E(2)), but not by ETYA. Furthermore, cyclo-oxygenase inhibitors decreased I(Na) and quenched AA-induced channel activation, indicating that the effect of intracellular AA on Na(V) was possibly mediated through AA metabolites. In addition, the PGE2-induced activation of I(Na) was mimicked by cAMP and quenched by a PKA (protein kinase A) inhibitor, a G(s) inhibitor and EP (E-series of prostaglandin) receptor antagonists. The results of the present study suggest that extracellular AA modulates Na(V) channel activity in rat cerebellar GCs without metabolic conversion, whereas intracellular AA augments the I(Na) by PGE(2)-mediated activation of cAMP/PKA pathways. These observations may explain the dual character of AA in neuronal pathogenesis.

Sodium channel activity modulates multiple functions in microglia

Microglia provide surveillance in the central nervous system and become activated following tissue insult. Detailed mechanisms by which microglia detect and respond to their environment are not fully understood, but it is known that microglia express a number of surface receptors and ion channels, including voltage-gated sodium channels, that participate in transduction of external stimuli to intra-cellular responses. To determine whether activated microglia are affected by the activity of sodium channels, we examined the expression of sodium channel isoforms in cultured microglia and the action of sodium channel blockade on multiple functions of activated microglia. Rat microglia in vitro express tetrodotoxin (TTX)-sensitive sodium channels Nav1.1 and Nav1.6 and the TTX-resistant channel Nav1.5, but not detectable levels of Nav1.2, Nav1.3, Nav1.7, Nav1.8, and Nav1.9. Sodium channel blockade with phenytoin (40 microM) and TTX (0.3 microM) significantly reduced by 50-60% the phagocytic activity of microglia activated with lipopolysaccharide (LPS); blockade with 10 microM TTX did not further reduce phagocytic activity. Phenytoin attenuated by approximately 50% the release of IL-1 alpha, IL-1 beta, and TNF-alpha from LPS-stimulated microglia, but had minimal effects on the release of IL-2, IL-4, IL-6, IL-10, MCP-1, and TGF-alpha. TTX (0.3 microM) reduced, but to a smaller extent, the release of IL-1 alpha, IL-1 beta, and TNF-alpha from activated microglia. Phenytoin and TTX also significantly decreased by approximately 50% adenosine triphosphate-induced migration by microglia; studies with microglia cultured from med mice (which lack Nav1.6) indicate that Nav1.6 plays a role in microglial migration. The results demonstrate that the activity of sodium channels contributes to effector roles of activated microglia.

A novel adhesion molecule in human breast cancer cells: voltage-gated Na+ channel beta1 subunit

Voltage-gated Na(+) channels (VGSCs), predominantly the 'neonatal' splice form of Na(v)1.5 (nNa(v)1.5), are upregulated in metastatic breast cancer (BCa) and potentiate metastatic cell behaviours. VGSCs comprise one pore-forming alpha subunit and one or more beta subunits. The latter modulate VGSC expression and gating, and can function as cell adhesion molecules of the immunoglobulin superfamily. The aims of this study were (1) to determine which beta subunits were expressed in weakly metastatic MCF-7 and strongly metastatic MDA-MB-231 human BCa cells, and (2) to investigate the possible role of beta subunits in adhesion and migration. In both cell lines, the beta subunit mRNA expression profile was SCN1B (encoding beta1)>>SCN4B (encoding beta4)>SCN2B (encoding beta2); SCN3B (encoding beta3) was not detected. MCF-7 cells had much higher levels of all beta subunit mRNAs than MDA-MB-231 cells, and beta1 mRNA was the most abundant. Similarly, beta1 protein was strongly expressed in MCF-7 and barely detectable in MDA-MB-231 cells. In MCF-7 cells transfected with siRNA targeting beta1, adhesion was reduced by 35%, while migration was increased by 121%. The increase in migration was reversed by tetrodotoxin (TTX). In addition, levels of nNa(v)1.5 mRNA and protein were increased following beta1 down-regulation. Stable expression of beta1 in MDA-MB-231 cells increased functional VGSC activity, process length and adhesion, and reduced lateral motility and proliferation. We conclude that beta1 is a novel cell adhesion molecule in BCa cells and can control VGSC (nNa(v)1.5) expression and, concomitantly, cellular migration.

Modulation of muscle rNaV1.4 Na+ channel isoform by arachidonic acid and its non-metabolized analog

Arachidonic acid (AA) and its metabolic products are important second messengers which exert many biological actions, including modulation of various ion channels. However, the blockage of muscle Na(+) channel isoforms by AA has not been examined in detail. Here, we investigated the modulating effects of AA on muscle rNa(V)1.4 isoforms expressed in human embryonic kidney 293 cells. The results revealed that AA has both activation and inhibitory effects on rNa(V)1.4 currents depending on the depolarizing potential: AA increased the rNa(V)1.4 current evoked by a depolarization of -30 or -40 mV, but significantly decreased the rNa(V)1.4 current evoked by a depolarization of membrane potential over -10 mV. At concentrations of 1-500 microM, the inhibitory effect on the rNa(V)1.4 current induced by AA was dose-dependent and reversible. In addition to modulating the amplitude of the rNa(V)1.4 current, AA significantly modulated the steady-state activation and inactivation properties of rNa(V)1.4 channels. Furthermore, treatment with AA resulted in a fairly slow recovery of the rNa(V)1.4 channel from inactivation; however, the inhibitory effect of AA was not changed by repetitive pulses or by changing frequency. The effect of AA on rNa(V)1.4 currents was completely mimicked by ETYA, the non-metabolized analog of AA. Our data demonstrated that AA, but not the metabolic products of AA, can voltage-dependent modulate rNa(V)1.4 currents.

An emerging role for voltage-gated Na+ channels in cellular migration: regulation of central nervous system development and potentiation of invasive cancers

Voltage-gated Na(+) channels (VGSCs) exist as macromolecular complexes containing a pore-forming alpha subunit and one or more beta subunits. The VGSC alpha subunit gene family consists of 10 members, which have distinct tissue-specific and developmental expression profiles. So far, four beta subunits (beta1-beta4) and one splice variant of beta1 (beta1A, also called beta1B) have been identified. VGSC beta subunits are multifunctional, serving as modulators of channel activity, regulators of channel cell surface expression, and as members of the immunoglobulin superfamily, cell adhesion molecules (CAMs). beta subunits are substrates of beta-amyloid precursor protein-cleaving enzyme (BACE1) and gamma-secretase, yielding intracellular domains (ICDs) that may further modulate cellular activity via transcription. Recent evidence shows that beta1 regulates migration and pathfinding in the developing postnatal CNS in vivo. The alpha and beta subunits, together with other components of the VGSC signaling complex, may have dynamic interactive roles depending on cell/tissue type, developmental stage, and pathophysiology. In addition to excitable cells like nerve and muscle, VGSC alpha and beta subunits are functionally expressed in cells that are traditionally considered nonexcitable, including glia, vascular endothelial cells, and cancer cells. In particular, the alpha subunits are up-regulated in line with metastatic potential and are proposed to enhance cellular migration and invasion. In contrast to the alpha subunits, beta1 is more highly expressed in weakly metastatic cancer cells, and evidence suggests that its expression enhances cellular adhesion. Thus, novel roles are emerging for VGSC alpha and beta subunits in regulating migration during normal postnatal development of the CNS as well as during cancer metastasis.

Potassium Channels Keep Mobile Cells on the Go

Cell motility is a prerequisite for the creation of new life, and it is required for maintaining the integrity of an organism. Under pathological conditions, “too much” motility may cause premature death. Studies over the past few years have revealed that ion channels are essential for cell motility. This review highlights the importance of K+ channels in regulating cell motility.

PLC-dependent intracellular Ca2+ release was associated with C6-ceramide-induced inhibition of Na+ current in rat granule cells

In this report, the effects of C(6)-ceramide on the voltage-gated inward Na(+) currents (I(Na)), two types of main K(+) current [outward rectifier delayed K(+) current (I(K)) and outward transient K(+) current (I(A))], and cell death in cultured rat cerebellar granule cells were investigated. At concentrations of 0.01-100 microM, ceramide produced a dose-dependent and reversible inhibition of I(Na) without alteration of the steady-state activation and inactivation properties. Treatment with C(2)-ceramide caused a similar inhibitory effect on I(Na). However, dihydro-C(6)-ceramide failed to modulate I(Na). The effect of C(6)-ceramide on I(Na) was abolished by intracellular infusion of the Ca(2+)-chelating agent, 1,2-bis (2-aminophenoxy) ethane-N, N, N9, N9-tetraacetic acid, but was mimicked by application of caffeine. Blocking the release of Ca(2+) from the sarcoplasmic reticulum with ryanodine receptor blocker induced a gradual increase in I(Na) amplitude and eliminated the effect of ceramide on I(Na). In contrast, the blocker of the inositol 1,4,5-trisphosphate-sensitive Ca(2+) receptor did not affect the action of C(6)-ceramide. Intracellular application of GTPgammaS also induced a gradual decrease in I(Na) amplitude, while GDPbetaS eliminated the effect of C(6)-ceramide on I(Na). Furthermore, the C(6)-ceramide effect on I(Na) was abolished after application of the phospholipase C (PLC) blockers and was greatly reduced by the calmodulin inhibitors. Fluorescence staining showed that C(6)-ceramide decreased cell viability and blocking I(Na) by tetrodotoxin did not mimic the effect of C(6)-ceramide, and inhibiting intracellular Ca(2+) release by dantrolene could not decrease the C(6)-ceramide-induced cell death. We therefore suggest that increased PLC-dependent Ca(2+) release through the ryanodine-sensitive Ca(2+) receptor may be responsible for the C(6)-ceramide-induced inhibition of I(Na), which does not seem to be associated with C(6)-ceramide-induced granule neuron death.

Epidermal growth factor potentiates in vitro metastatic behaviour of human prostate cancer PC-3M cells: involvement of voltage-gated sodium channel

Background

Although a high level of functional voltage-gated sodium channel (VGSC) expression has been found in strongly metastatic human and rat prostate cancer (PCa) cells, the mechanism(s) responsible for the upregulation is unknown. The concentration of epidermal growth factor (EGF), a modulator of ion channels, in the body is highest in prostatic fluid. Thus, EGF could be involved in the VGSC upregulation in PCa. The effects of EGF on VGSC expression in the highly metastatic human PCa PC-3M cell line, which was shown previously to express both functional VGSCs and EGF receptors, were investigated. A quantitative approach, from gene level to cell behaviour, was used. mRNA levels were determined by real-time PCR. Protein expression was studied by Western blots and immunocytochemistry and digital image analysis. Functional assays involved measurements of transverse migration, endocytic membrane activity and Matrigel invasion.

Results

Exogenous EGF enhanced the cells' in vitro metastatic behaviours (migration, endocytosis and invasion). Endogenous EGF had a similar involvement. EGF increased VGSC Nav1.7 (predominant isoform in PCa) mRNA and protein expressions. Co-application of the highly specific VGSC blocker tetrodotoxin (TTX) suppressed the effect of EGF on all three metastatic cell behaviours studied.

Conclusion

1) EGF has a major involvement in the upregulation of functional VGSC expression in human PCa PC-3M cells. (2) VGSC activity has a significant intermediary role in potentiating effect of EGF in human PCa.