Potassium channel activation inhibits proliferation of breast cancer cells by activating a senescence program

Novel insights into voltage-gated ion channels: Translational breakthroughs in medical oncology

Preclinical evidence suggests that voltage gradients can act as a kind of top-down master regulator during embryogenesis and orchestrate downstream molecular-genetic pathways during organ regeneration or repair. Moreover, electrical stimulation shifts response to injury toward regeneration instead of healing or scarring. Cancer and embryogenesis not only share common phenotypical features but also commonly upregulated molecular pathways. Voltage-gated ion channel activity is directly or indirectly linked to the pathogenesis of cancer hallmarks, while experimental and clinical studies suggest that their modulation, e.g., by anesthetic agents, may exert antitumor effects. A large recent clinical trial served as a proof-of-principle for the benefit of preoperative use of topical sodium channel blockade as a potential anticancer strategy against early human breast cancers. Regardless of whether ion channel aberrations are primary or secondary cancer drivers, understanding the functional consequences of these events may guide us toward the development of novel therapeutic approaches.

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.

Targeting the hERG1 and β1 integrin complex for cancer treatment

INTRODUCTION

Despite great advances, novel therapeutic targets and strategies are still needed, in particular for some carcinomas in the metastatic stage (breast cancer, colorectal cancer, pancreatic ductal adenocarcinoma and the clear cell renal carcinoma). Ion channels may be considered good cancer biomarkers and targets for antineoplastic therapy. These concepts are particularly relevant considering the hERG1 potassium channel as a novel target for antineoplastic therapy.

AREAS COVERED

A great deal of evidence demonstrates that hERG1 is aberrantly expressed in human cancers, in particular in aggressive carcinomas. A relevant cornerstone was the discovery that, in cancer cells, the channel is present in a very peculiar conformation, strictly bound to the β1 subunit of integrin receptors. The hERG1/β1 integrin complex does not occur in the heart. Starting from this evidence, we developed a novel single chain bispecific antibody (scDb-hERG1-β1), which specifically targets the hERG1/β1 integrin complex and exerts antineoplastic effects in preclinical experiments.

EXPERT OPINION

Since hERG1 blockade cannot be pursued for antineoplastic therapy due to the severe cardiac toxic effects (ventricular arrhythmias) that many hERG1 blockers exert, different strategies must be identified to specifically target hERG1 in cancer. The targeting of the hERG1/β1 integrin complex through the bispecific antibody scDb-hERG1-β1 can overcome such hindrances.

Kv 11.1 Expression Is Associated With Malignancy of Canine Mammary Gland Tumors

BACKGROUND/AIM

The expression level of the voltage-dependent potassium channel Kv 11.1 was shown to be associated with the clinicopathological features, aggressiveness, and prognosis of human breast cancer. Canine mammary gland tumor (cMGT) is the most common tumor type in intact female dogs; however, the significance of Kv 11.1 in cMGT is unknown. The aim of this study was to identify Kv 11.1 expression in 57 benign and malignant cMGT tissues from dogs and to investigate the correlation of Kv 11.1 expression with the clinicopathological parameters and prognosis of cMGT.

MATERIALS AND METHODS

A total of 57 samples were collected from cMGTs surgically resected at the Veterinary Medical Teaching Hospital, Seoul National University and subjected to immunohistochemistry assay using rabbit anti-Kv 11.1 polyclonal antibody. Immunohistochemical staining results were evaluated as the sum of intensity and percentage scores. The correlation between immunohistochemistry scores and clinicopathological parameters was investigated.

RESULTS

Immunohistochemical analysis revealed that Kv 11.1 immunoreactivity was higher in benign cMGTs than in malignant cMGTs. Kv 11.1 expression was significantly associated with tumor malignancy (p<0.001), tumor size (p<0.001), histological grade (p<0.05), and age at the time of mastectomy (p<0.05).

CONCLUSION

This study presents the first evidence of Kv 11.1 expression in cMGTs and indicates an inverse correlation between Kv 11.1 expression and tumor malignancy. Kv 11.1 expression can be used as a prognostic biomarker and a tool for the management of cMGTs.

Inter-organ communication during tissue regeneration

Tissue regeneration is not simply a local repair event occurring in isolation from the distant, uninjured parts of the body. Rather, evidence indicates that regeneration is a whole-animal process involving coordinated interactions between different organ systems. Here, we review recent studies that reveal how remote uninjured tissues and organ systems respond to and engage in regeneration. We also discuss the need for toolkits and technological advancements to uncover and dissect organ communication during regeneration.

Fluorescent membrane potential assay for drug screening on Kv10.1 channel: identification of BL-1249 as a channel activator

Resting membrane potential is a bioelectric property of all cells. Multiple players govern this property, the ion channels being the most important. Ion channel dysfunction can affect cells' resting membrane potential and could be associated with numerous diseases. Therefore, the drug discovery focus on ion channels has increased yearly. In addition to patch-clamp, cell-based fluorescent assays have shown a rapid and reliable method for searching new ion channel modulators. Here, we used a cell-based membrane potential assay to search for new blockers of the Kv10.1, a potassium channel strongly associated with cancer progression and a promising target in anticancer therapy. We found that fluoxetine and miconazole can inhibit the Kv10.1 channel in the micromolar range. In contrast, BL-1249 potentiates Kv10.1 currents in a dose-dependent manner, becoming the first molecule described as an activator of the channel. These results demonstrate that cell-based membrane potential assay can accelerate the discovery of new Kv10.1 modulators.

Pathophysiological role of ion channels and transporters in HER2-positive breast cancer

The incidence of breast cancer (BC) has been increasing each year, and BC is now the most common malignant tumor in women. Among the numerous BC subtypes, HER2-positive BC can be treated with a variety of strategies based on targeting HER2. Although there has been great progress in the treatment of HER2-positive BC, recurrence, metastasis and drug resistance remain considerable challenges. The dysfunction of ion channels and transporters can affect the development and progression of HER2-positive BC, so these entities are expected to be new therapeutic targets. This review summarizes various ion channels and transporters associated with HER2-positive BC and suggests potential targets for the development of new and effective therapies.

Ion Channels and Pumps in Autophagy: A Reciprocal Relationship

Autophagy, the process of cellular self-degradation, is intrinsically tied to the degradative function of the lysosome. Several diseases have been linked to lysosomal degradative defects, including rare lysosomal storage disorders and neurodegenerative diseases. Ion channels and pumps play a major regulatory role in autophagy. Importantly, calcium signaling produced by TRPML1 (transient receptor potential cation channel, mucolipin subfamily) has been shown to regulate autophagic progression through biogenesis of autophagic-lysosomal organelles, activation of mTORC1 (mechanistic target of rapamycin complex 1) and degradation of autophagic cargo. ER calcium channels such as IP₃Rs supply calcium for the lysosome, and lysosomal function is severely disrupted in the absence of lysosomal calcium replenishment by the ER. TRPML1 function is also regulated by LC3 (microtubule-associated protein light chain 3) and mTORC1, two critical components of the autophagic network. Here we provide an overview of the current knowledge about ion channels and pumps-including lysosomal V-ATPase (vacuolar proton-ATPase), which is required for acidification and hence proper enzymatic activity of lysosomal hydrolases-in the regulation of autophagy, and discuss how functional impairment of some of these leads to diseases.

Molecular Activation of the Kv11.1 Channel Reprograms EMT in Colon Cancer by Inhibiting TGFβ Signaling via Activation of Calcineurin

Control of ionic gradients is critical to maintain cellular homeostasis in both physiological and pathological conditions, but the role of ion channels in cancer cells has not been studied thoroughly. In this work we demonstrated that activity of the Kv11.1 potassium channel plays a vital role in controlling the migration of colon cancer cells by reversing the epithelial-to-mesenchymal transition (EMT) into the mesenchymal-to-epithelial transition (MET). We discovered that pharmacological stimulation of the Kv11.1 channel with the activator molecule NS1643 produces a strong inhibition of colon cancer cell motility. In agreement with the reversal of EMT, NS1643 treatment leads to a depletion of mesenchymal markers such as SNAIL1, SLUG, TWIST, ZEB, N-cadherin, and c-Myc, while the epithelial marker E-cadherin was strongly upregulated. Investigating the mechanism linking Kv11.1 activity to reversal of EMT into MET revealed that stimulation of Kv11.1 produced a strong and fast inhibition of the TGFβ signaling. Application of NS1643 resulted in de-phosphorylation of the TGFβ downstream effectors R-SMADs by activation of the serine/threonine phosphatase PP2B (calcineurin). Consistent with the role of TGFβ in controlling cancer stemness, NS1643 also produced a strong inhibition of NANOG, SOX2, and OCT4 while arresting the cell cycle in G0/G1. Our data demonstrate that activation of the Kv11.1 channel reprograms EMT into MET by inhibiting TGFβ signaling, which results in inhibition of motility in colon cancer cells.

Potassium and Chloride Ion Channels in Cancer: A Novel Paradigm for Cancer Therapeutics

Cancer is a collection of diseases caused by specific changes at the genomic level that support cell proliferation indefinitely. Traditionally, ion channels are known to control a variety of cellular processes including electrical signal generation and transmission, secretion, and contraction by controlling ionic gradients. However, recent studies had brought to light important facts on ion channels in cancer biology.In this review we discuss the mechanism linking potassium or chloride ion channel activity to biochemical pathways controlling proliferation in cancer cells and the potential advantages of targeting ion channels as an anticancer therapeutic option.

Compensatory expression of NRF2-dependent antioxidant genes is required to overcome the lethal effects of Kv11.1 activation in breast cancer cells and PDOs

Potassium channels are important regulators of cellular homeostasis and targeting these proteins pharmacologically is unveiling important mechanisms in cancer cell biology. Here we demonstrate that pharmacological stimulation of the Kv11.1 potassium channel activity results in mitochondrial reactive oxygen species (ROS) production and fragmentation in breast cancer cell lines and patient-derived organoids independent of breast cancer subtype. mRNA expression profiling revealed that Kv11.1 activity significantly altered expression of genes controlling the production of ROS and endoplasmic-reticulum (ER) stress. Characterization of the transcriptional signature of breast cancer cells treated with Kv11.1 potassium channel activators strikingly revealed an adaptive response to the potentially lethal augmentation of ROS by increasing Nrf2-dependent transcription of antioxidant genes. Nrf2 in this context was shown to promote survival in breast cancer, whereas knockdown of Nrf2 lead to Kv11.1-induced cell death. In conclusion, we found that the Kv11.1 channel activity promotes oxidative stress in breast cancer cells and that suppression of the Nrf2-mediated anti-oxidant survival mechanism strongly sensitized breast cancer cells to a lethal effect of pharmacological activation of Kv11.1.

Potassium ions promote hexokinase-II dependent glycolysis

High expression levels of mitochondria-associated hexokinase-II (HKII) represent a hallmark of metabolically highly active cells such as fast proliferating cancer cells. Typically, the enzyme provides a crucial metabolic switch towards aerobic glycolysis. By imaging metabolic activities on the single-cell level with genetically encoded fluorescent biosensors, we here demonstrate that HKII activity requires intracellular K+. The K+ dependency of glycolysis in cells expressing HKII was confirmed in cell populations using extracellular flux analysis and nuclear magnetic resonance-based metabolomics. Reductions of intracellular K+ by gramicidin acutely disrupted HKII-dependent glycolysis and triggered energy stress pathways, while K+ re-addition promptly restored glycolysis-dependent adenosine-5'-triphosphate generation. Moreover, expression and activation of KV1.3, a voltage-gated K+ channel, lowered cellular K+ content and the glycolytic activity of HEK293 cells. Our findings unveil K+ as an essential cofactor of HKII and provide a mechanistic link between activities of distinct K+ channels and cell metabolism.

Bioelectric signaling: Reprogrammable circuits underlying embryogenesis, regeneration, and cancer

How are individual cell behaviors coordinated toward invariant large-scale anatomical outcomes in development and regeneration despite unpredictable perturbations? Endogenous distributions of membrane potentials, produced by ion channels and gap junctions, are present across all tissues. These bioelectrical networks process morphogenetic information that controls gene expression, enabling cell collectives to make decisions about large-scale growth and form. Recent progress in the analysis and computational modeling of developmental bioelectric circuits and channelopathies reveals how cellular collectives cooperate toward organ-level structural order. These advances suggest a roadmap for exploiting bioelectric signaling for interventions addressing developmental disorders, regenerative medicine, cancer reprogramming, and synthetic bioengineering.

Anticancer Mechanisms of Bioactive Peptides

Despite technological advancement, there is no 100% effective treatment against metastatic cancer. Increasing resistance of cancer cells towards chemotherapeutic drugs along with detrimental side effects remained a concern. Thus, the urgency in developing new anticancer agents has been raised. Anticancer peptides have been proven to display potent activity against a wide variety of cancer cells. Several mode of actions describing their cytostatic and cytotoxic effect on cancer cells have been proposed which involves cell surface binding leading to membranolysis or internalization to reach their intracellular target. Understanding the mechanism of action of these anticancer peptides is important in achieving full therapeutic success. In the present article, we discuss the anticancer action of peptides accompanied by the mechanisms underpinning their toxicity to cancer cells.

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.

Targeting senescent cells and tumor therapy (Review)

Cell senescence is caused by the activation of cell cycle inhibition pathways induced by an accumulation of cellular damage, where cells permanently leave the cell cycle. Senescent cells undergo changes in cell morphology, transcription, protein homeostasis, metabolism and other characteristic alterations. At the same time, senescent cells are able to resist apoptosis and accumulate in multiple organs and tissues in vivo. Senescent cells are capable of activating inflammatory factor secretion pathways, generating local, non-infectious inflammatory microenvironments within tissues, leading to organ degeneration and the development of aging-associated diseases. A large number of recently published studies have demonstrated that removing senescent cells from the body delays the occurrence of various aging-associated diseases. Therefore, the targeted killing of senescent cells potentially has important clinical applications in the treatment of various aging-associated diseases, aiming to improve the life span of patients. The present review summarizes recent progress that has been made in the field of senescent cell clearance and various anti-aging strategies. The history of cell senescence research is briefly reviewed, along with the association between cell senescence and tumor therapy. Furthermore, the potential of senescent cells to be used as therapeutic targets in various senescence-associated diseases is primarily discussed, and the limitations, as well as the future prospects of this line of research, are reviewed.

Pathological role of ion channels and transporters in the development and progression of triple-negative breast cancer

Breast cancer is a common malignancy in women. Among breast cancer types, triple-negative breast cancer (TNBC) tends to affect younger women, is prone to axillary lymph node, lung, and bone metastases; and has a high recurrence rate. Due to a lack of classic biomarkers, the currently available treatments are surgery and chemotherapy; no targeted standard treatment options are available. Therefore, it is urgent to find a novel and effective therapeutic target. As alteration of ion channels and transporters in normal mammary cells may affect cell growth, resulting in the development and progression of TNBC, ion channels and transporters may be promising new therapeutic targets for TNBC. This review summarizes ion channels and transporters related to TNBC and may provide new tumor biomarkers and help in the development of novel targeted therapies.

Novel Therapeutic Approaches of Ion Channels and Transporters in Cancer

The expression and function of many ion channels and transporters in cancer cells display major differences in comparison to those from healthy cells. These differences provide the cancer cells with advantages for tumor development. Accordingly, targeting ion channels and transporters have beneficial anticancer effects including inhibition of cancer cell proliferation, migration, invasion, metastasis, tumor vascularization, and chemotherapy resistance, as well as promoting apoptosis. Some of the molecular mechanisms associating ion channels and transporters with cancer include the participation of oxidative stress, immune response, metabolic pathways, drug synergism, as well as noncanonical functions of ion channels. This diversity of mechanisms offers an exciting possibility to suggest novel and more effective therapeutic approaches to fight cancer. Here, we review and discuss most of the current knowledge suggesting novel therapeutic approaches for cancer therapy targeting ion channels and transporters. The role and regulation of ion channels and transporters in cancer provide a plethora of exceptional opportunities in drug design, as well as novel and promising therapeutic approaches that may be used for the benefit of cancer patients.

Mesobuthus eupeus venom induced injury in the colorectal carcinoma cell line (HT29) through altering the mitochondria membrane stability

Objective(s):

The purpose of this study was to investigate cytotoxicity and membrane toxicity effects induced by Mesobuthus eupeus venom (MEV) on the HT-29 cell line.

Materials and Methods:

To determine the in vitro cytotoxicity via MTT assays, HT-29 (as cancer cell line) and Hek-293T (as normal cell) were treated through different concentrations of MEV, and cytotoxicity effects were then measured through assessment of mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) generation, and apoptosis induction. The colony formation assay was performed to measure the antiproliferative effect of MEV on HT-29 cells. Nuclei alterations were also observed during apoptosis following DAPI staining. Besides, atomic force microscopy (AFM) was used to detect alterations in morphology and ultrastructure of the cells at a nanoscale level.

Results:

According to MTT and clonogenic assays, MEV caused a significant decrease in cell viability and proliferation of HT-29 cells while it did not have any impact on normal cells and the IC50 value was found to be 10 µg/ml. Induction of apoptosis was also confirmed by flowcytometric analysis in HT-29 cells. Moreover, the results indicated that MEV had led to a suppression of proliferation and induction of apoptosis through increased ROS and depolarization of mitochondria. Furthermore, AFM imaging demonstrated apoptosis cell death after being treated with MEV in HT-29 cells.

Conclusion:

This study showed that MEV had an antiproliferative effect on HT-29 cells by inducing apoptosis through the mitochondria signaling pathway. These findings suggested that MEV could be used as a promising natural remedy for cancer treatment.

Repurposing Kir6/SUR2 Channel Activator Minoxidil to Arrests Growth of Gynecologic Cancers

Gynecologic cancers are among the most lethal cancers found in women, and, advanced stage cancers are still a treatment challenge. Ion channels are known to contribute to cellular homeostasis in all cells and mounting evidence indicates that ion channels could be considered potential therapeutic targets against cancer. Nevertheless, the pharmacologic effect of targeting ion channels in cancer is still understudied. We found that the expression of Kir6.2/SUR2 potassium channel is a potential favorable prognostic factor in gynecologic cancers. Also, pharmacological stimulation of the Kir6.2/SUR2 channel activity with the selective activator molecule minoxidil arrests tumor growth in a xenograft model of ovarian cancer. Investigation on the mechanism linking the Kir6.2/SUR2 to tumor growth revealed that minoxidil alters the metabolic and oxidative state of cancer cells by producing mitochondrial disruption and extensive DNA damage. Consequently, application of minoxidil results in activation of a caspase-3 independent cell death pathway. Our data show that repurposing of FDA approved K⁺ channel activators may represent a novel, safe adjuvant therapeutic approach to traditional chemotherapy for the treatment of gynecologic cancers.

4,4'-Diisothiocyanatostilbene-2,2'-disulfonate modulates voltage-gated K+ current and influences cell cycle arrest in androgen sensitive and insensitive human prostate cancer cell lines

The stilbene derivative, 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), an anion channel blocker is used in the present study to evaluate its modulatory effect on voltage-gated K⁺ current (I_K) in human prostate cancer cell lines (LNCaP and PC-3). Voltage-gated K⁺ (K_V) channels in the plasma membrane are critically involved in the proliferation of tumor cells. Therefore, K_V channels are considered as a novel potential target for cancer treatment. The results of the present study show that the external perfusion of DIDS activates I_K in a concentration-dependent manner, although the known K⁺ channel blocker TEA failed to block the DIDS activated I_K in PC-3 cells. Whereas, in LNCaP cells, the higher concentration of DIDS blocked I_K, though this effect was not completely recovered after washout. The difference in function of DIDS might be due to the expression of different Kv channel isoforms in LNCaP and PC-3 cells. Further, the anticancer studies show that treatment of DIDS significantly induced G2/M phase cell cycle arrest and induced moderate and low level of cell death in LNCaP and PC-3 cells respectively. This finding reveals that DIDS modulates I_K and exerts cell cycle arrest and cell death in LNCaP and PC-3 cells.

Robust pathway sampling in phenotype prediction. Application to triple negative breast cancer

Background

Phenotype prediction problems are usually considered ill-posed, as the amount of samples is very limited with respect to the scrutinized genetic probes. This fact complicates the sampling of the defective genetic pathways due to the high number of possible discriminatory genetic networks involved. In this research, we outline three novel sampling algorithms utilized to identify, classify and characterize the defective pathways in phenotype prediction problems, such as the Fisher’s ratio sampler, the Holdout sampler and the Random sampler, and apply each one to the analysis of genetic pathways involved in tumor behavior and outcomes of triple negative breast cancers (TNBC). Altered biological pathways are identified using the most frequently sampled genes and are compared to those obtained via Bayesian Networks (BNs).

Results

Random, Fisher’s ratio and Holdout samplers were more accurate and robust than BNs, while providing comparable insights about disease genomics.

Conclusions

The three samplers tested are good alternatives to Bayesian Networks since they are less computationally demanding algorithms. Importantly, this analysis confirms the concept of “biological invariance” since the altered pathways should be independent of the sampling methodology and the classifier used for their inference. Nevertheless, still some modifications are needed in the Bayesian networks to be able to sample correctly the uncertainty space in phenotype prediction problems, since the probabilistic parameterization of the uncertainty space is not unique and the use of the optimum network might falsify the pathways analysis.

HERG channel and cancer: A mechanistic review of carcinogenic processes and therapeutic potential

The human ether-à-go-go related gene (HERG) encodes the alpha subunit of Kv11.1, which is a voltage-gated K⁺ channel protein mainly expressed in heart and brain tissue. HERG plays critical role in cardiac repolarization, and mutations in HERG can cause long QT syndrome. More recently, evidence has emerged that HERG channels are aberrantly expressed in many kinds of cancer cells and play important roles in cancer progression. HERG could therefore be a potential biomarker for cancer and a possible molecular target for anticancer drug design. HERG affects a number of cellular processes, including cell proliferation, apoptosis, angiogenesis and migration, any of which could be affected by dysregulation of HERG. This review provides an overview of available information on HERG channel as it relates to cancer, with focus on the mechanism by which HERG influences cancer progression. Molecular docking attempts suggest two possible protein-protein interactions of HERG with the ß1-integrin receptor and the transcription factor STAT-1 as novel HERG-directed therapeutic targeting which avoids possible cardiotoxicity. The role of epigenetics in regulating HERG channel expression and activity in cancer will also be discussed. Finally, given its inherent extracellular accessibility as an ion channel, we discuss regulatory roles of this molecule in cancer physiology and therapeutic potential. Future research should be directed to explore the possibilities of therapeutic interventions targeting HERG channels while minding possible complications.

Ion Channel and Neurotransmitter Modulators as Electroceutical Approaches to the Control of Cancer

The activities of individual cells must be tightly coordinated in order to build and maintain complex 3-dimensional body structures during embryogenesis and regeneration. Thus, one way to view cancer is within systems biology as a network disorder affecting the ability of cells to properly interact with a morphodynamic field of instructive signals that keeps proliferation and migration orchestrated toward the anatomical needs of the host or-ganism. One layer of this set of instructive microenvironmental cues is bioelectrical. Voltage gradients among all somatic cells (not just excitable nerve and muscle) control cell behavior, and the ionic coupling of cells into networks via electrochemical synapses allows them to implement tissue-level patterning decisions. These gradients have been increasingly impli-cated in the induction and suppression of tumorigenesis and metastasis, in the emerging links between developmental bioelectricity to the cancer problem. Consistent with the well-known role of neurotransmitter molecules in transducing electrical activity to downstream cascades in the brain, serotonergic signaling has likewise been implicated in cancer. Here, we review these recent data and propose new approaches for manipulating bioelectric and neurotransmitter pathways in cancer biology based on a bioelectric view of cancer. To sup-port this methodology, we present new data on the effects of the SSRI Prozac and its analog (ZINC ID = ZINC06811610) on survival of both cancer (MCF7) and normal (MCF10A) breast cells exposed to these compounds. We found an IC50 concentration (25 μM for Pro-zac and 100 μM for the Prozac analog) at which these compounds inhibited tumor cell sur-vival and proliferation. Additionally, at these concentrations, we did not observe alterations in a non-tumoral cell line. This constitutes a proof-of-concept demonstration for our hy-pothesis that the use of both existing and novel drugs as electroceuticals could serve as an alternative to highly toxic chemotherapy strategies replacing or augmenting them with less toxic alternatives. We believe this new approach forms an exciting roadmap for future bio-medical advances.

Potassium channel activity controls breast cancer metastasis by affecting β-catenin signaling

Potassium ion channels are critical in the regulation of cell motility. The acquisition of cell motility is an essential parameter of cancer metastasis. However, the role of K⁺ channels in cancer metastasis has been poorly studied. High expression of the hG1 gene, which encodes for Kv11.1 channel associates with good prognosis in estrogen receptor-negative breast cancer (BC). We evaluated the efficacy of the Kv11.1 activator NS1643 in arresting metastasis in a triple negative breast cancer (TNBC) mouse model. NS1643 significantly reduces the metastatic spread of breast tumors in vivo by inhibiting cell motility, reprogramming epithelial–mesenchymal transition via attenuation of Wnt/β-catenin signaling and suppressing cancer cell stemness. Our findings provide important information regarding the clinical relevance of potassium ion channel expression in breast tumors and the mechanisms by which potassium channel activity can modulate tumor biology. Findings suggest that Kv11.1 activators may represent a novel therapeutic approach for the treatment of metastatic estrogen receptor-negative BC. Ion channels are critical factor for cell motility but little is known about their role in metastasis. Stimulation of the Kv11.1 channel suppress the metastatic phenotype in TNBC. This work could represent a paradigm-shifting approach to reducing mortality by targeting a pathway that is central to the development of metastases.

EDEn-Electroceutical Design Environment: Ion Channel Tissue Expression Database with Small Molecule Modulators

The emerging field of bioelectricity has revealed numerous new roles for ion channels beyond the nervous system, which can be exploited for applications in regenerative medicine. Developing such biomedical interventions for birth defects, cancer, traumatic injury, and bioengineering first requires knowledge of ion channel targets expressed in tissues of interest. This information can then be used to select combinations of small molecule inhibitors and/or activators that manipulate the bioelectric state. Here, we provide an overview of electroceutical design environment (EDEn), the first bioinformatic platform that facilitates the design of such therapeutic strategies. This database includes information on ion channels and ion pumps, linked to known chemical modulators and their properties. The database also provides information about the expression levels of the ion channels in over 100 tissue types. The graphical interface allows the user to readily identify chemical entities that can alter the electrical properties of target cells and tissues.

Ion Channels in Cancer: Are Cancer Hallmarks Oncochannelopathies?

Genomic instability is a primary cause and fundamental feature of human cancer. However, all cancer cell genotypes generally translate into several common pathophysiological features, often referred to as cancer hallmarks. Although nowadays the catalog of cancer hallmarks is quite broad, the most common and obvious of them are 1) uncontrolled proliferation, 2) resistance to programmed cell death (apoptosis), 3) tissue invasion and metastasis, and 4) sustained angiogenesis. Among the genes affected by cancer, those encoding ion channels are present. Membrane proteins responsible for signaling within cell and among cells, for coupling of extracellular events with intracellular responses, and for maintaining intracellular ionic homeostasis ion channels contribute to various extents to pathophysiological features of each cancer hallmark. Moreover, tight association of these hallmarks with ion channel dysfunction gives a good reason to classify them as special type of channelopathies, namely oncochannelopathies. Although the relation of cancer hallmarks to ion channel dysfunction differs from classical definition of channelopathies, as disease states causally linked with inherited mutations of ion channel genes that alter channel's biophysical properties, in a broader context of the disease state, to which pathogenesis ion channels essentially contribute, such classification seems absolutely appropriate. In this review the authors provide arguments to substantiate such point of view.

hERG1 channel expression associates with molecular subtypes and prognosis in breast cancer

Background

Breast cancer (BC) is the most frequent malignancy among females worldwide. Despite several efforts and improvements in early diagnosis and treatment, there are still tumors characterized by an aggressive behavior due to unfavorable biology, thus quite difficult to treat. In this view, searching for novel potential biomarkers is mandatory. Among them, in the recent years data have been gathered addressing ion channel as important players in oncology.

Methods

A retrospective pilot study was performed on 40 BC samples by means of immunohistochemistry in order to evaluate hERG1 potassium channels expression in BC.

Results

We provide evidence that hERG1 is expressed in all the BC samples analyzed. hERG1 expression was significantly associated with molecular subtype with the highest expression in Luminal A and the lowest in basal-like tumors (p = 0.001), tumor grading (the highest hERG1 expression in well-moderate differentiated tumors, p = 0.020), estrogen receptors (high hERG1 expression in ER-positive samples, p = 0.008) and Ki67 proliferative index (high hERG1 scoring in samples with low proliferative index, p = 0.038). Also, a p value close to significance was noticed for the association between hERG1 and HER2 expression (p = 0.079). At the survival analysis, patients with high hERG1 expression turned out to have a longer progression-free survival, although statistical significance was not reached (p = 0.195). The same trend was observed analyzing local relapse free-survival (LRFS) and metastases-free survival (MFS): patients with higher hERG1 scoring had longer LRFS and MFS (p = 0.124 and p = 0.071, respectively).

Conclusions

The results of this pilot study provide the first evidence that the hERG1 protein is expressed in primary BC, and its expression associates with molecular subtype. hERG1 apparently behaves as a protective factor, since it contributes to identify a subset of patients with better outcome. Overall, these data suggest that hERG1 might be an additional tool for the management of BC, nevertheless further investigations are warranted to better clarify hERG1 role and clinical usefulness in BC.

hERG1/Kv11.1 activation stimulates transcription of p21waf/cip in breast cancer cells via a calcineurin-dependent mechanism

The function of Kv11.1 is emerging in breast cancer biology, as a growing body of evidence indicates that the hERG1/Kv11.1 potassium channel is aberrantly expressed in several cancer types including breast cancers.

The biological effects of Kv11.1 channel blockers and their associated side effects are very well known but the potential use of Kv11.1 activators as an anticancer strategy are still unexplored. In our previous work, we have established that stimulation of the Kv11.1 potassium channel activates a senescent-like program that is characterized by a significant increase in tumor suppressor protein levels, such as p21^waf/cip and p16^INK4A. In this study we investigated the mechanism linking Kv11.1 stimulation to augmentation of p21^waf/cip protein level. We have demonstrated that the Kv11.1 channel activator NS1643 activates a calcineurin-dependent transcription of p21^waf/cip and that this event is fundamental for the inhibitory effect of NS1643 on cell proliferation. Our results reveal a novel mechanism by which stimulation of Kv11.1 channel leads to transcription of a potent tumor suppressor and suggest a potential therapeutic use for Kv11.1 channel activators.

Activation of hERG3 channel stimulates autophagy and promotes cellular senescence in melanoma

Ion channels play a major factor in maintaining cellular homeostasis but very little is known about the role of these proteins in cancer biology. In this work we have discovered that, the Kv11.3 (hERG3) a plasma-membrane potassium channel plays a critical role in the regulation of autophagy in a cancer cell model. We have found that pharmacologic stimulation of the Kv11.3 channel with a small molecule activator, NS1643 induced autophagy via activation of an AMPK-dependent signaling pathway in melanoma cell line. In addition, we have found that NS1643 produced a strong inhibition of cell proliferation by activating a cellular senescence program. Furthermore, inhibition of autophagy via siRNA targeting AMPK or treatment with hydroxychloroquine an autophagy inhibitor activates apoptosis in NS1643-treated cells. Thus, we propose that, Kv11.3 is a novel mediator of autophagy, autophagy can be a survival mechanism contributing to cellular senescence, and that use of a combinatorial pharmacologic approach of Kv11.3 activator with inhibitors of autophagy represents a novel therapeutic approach against melanoma.

Preclinical study of a Kv11.1 potassium channel activator as antineoplastic approach for breast cancer

Potassium ion (K⁺) channels have been recently found to play a critical role in cancer biology. Despite that pharmacologic manipulation of ion channels is recognized as an important therapeutic approach, very little is known about the effects of targeting of K⁺ channels in cancer. In this study, we demonstrate that use of the Kv11.1 K⁺ channel activator NS1643 inhibits tumor growth in an in vivo model of breast cancer.

Tumors exposed to NS1643 had reduced levels of proliferation markers, high expression levels of senescence markers, increased production of ROS and DNA damage compared to tumors of untreated mice. Importantly, mice treated with NS1643 did not exhibit significant cardiac dysfunction. In conclusion, pharmacological stimulation of Kv11.1 activity produced arrested TNBC-derived tumor growth by generating DNA damage and senescence without significant side effects. We propose that use of Kv11.1 channels activators could be considered as a possible pharmacological strategy against breast tumors.

hERG1 potassium channel in cancer cells: a tool to reprogram immortality

It has been well established that changes in ion fluxes across cellular membranes as a function of time is fundamental in maintaining cellular homeostasis of every living cell. Consequently, dysregulation of ion channels activity is a critical event in pathological conditions of several tissues, including cancer. Nevertheless, the role of ion channels in cancer biology is still not well understood and very little is known about the possible therapeutic opportunities offered by the use of the vast collection of drugs that target ion channels. In this review, we focus on the recent advances in understanding the role of the voltage-gated hERG1 potassium channel in cancer and on the effects of pharmacologic manipulation of the hERG1 in cancer cells aiming to provide insights into the biochemical signaling and cellular processes that are altered by using these drugs.

Ion-Switchable Quantum Dot Förster Resonance Energy Transfer Rates in Ratiometric Potassium Sensors

The tools for optically imaging cellular potassium concentrations in real-time are currently limited to a small set of molecular indicator dyes. Quantum dot-based nanosensors are more photostable and tunable than organic indicators, but previous designs have fallen short in size, sensitivity, and selectivity. Here, we introduce a small, sensitive, and selective nanosensor for potassium measurements. A dynamic quencher modulates the fluorescence emitted by two different quantum dot species to produce a ratiometric signal. We characterized the potassium-modulated sensor properties and investigated the photonic interactions within the sensors. The quencher's protonation changes in response to potassium, which modulates its Förster radiative energy transfer rate and the corresponding interaction radii with each quantum dot species. The nanosensors respond to changes in potassium concentrations typical of the cellular environment and thus provide a promising tool for imaging potassium fluxes during biological events.

Stimulation of hERG1 channel activity promotes a calcium-dependent degradation of cyclin E2, but not cyclin E1, in breast cancer cells

Cyclin E2 gene amplification, but not cyclin E1, has been recently defined as marker for poor prognosis in breast cancer, and appears to play a major role in proliferation and therapeutic resistance in several breast cancer cells. Our laboratory has previously reported that stimulation of the hERG1 potassium channel with selective activators led to down-regulation of cyclin E2 in breast cancer cells. In this work, we demonstrate that stimulation of hERG1 promotes an ubiquitin-proteasome-dependent degradation of cyclin E2 in multiple breast cancer cell lines representing Luminal A, HER2+ and Trastuzumab-resistant breast cancer cells. In addition we have also reveal that hERG1 stimulation induces an increase in intracellular calcium that is required for cyclin E2 degradation. This novel function for hERG1 activity was specific for cyclin E2, as cyclins A, B, D E1 were unaltered by the treatment.

Our results reveal a novel mechanism by which hERG1 activation impacts the tumor marker cyclin E2 that is independent of cyclin E1, and suggest a potential therapeutic use for hERG1 channel activators.

hERG1 Potassium Channels: Novel Biomarkers in Human Solid Cancers

Because of their high incidence and mortality solid cancers are a major health problem worldwide. Although several new biomarkers and potential targets for therapy have been identified through biomolecular research in the last years, the effects on patients' outcome are still unsatisfactory. Increasing evidence indicates that hERG1 potassium channels are overexpressed in human primary cancers of different origin and several associations between hERG1 expression and clinicopathological features and/or outcome are emerging. Aberrant hERG1 expression may be exploited either for early diagnosis (especially in those cancers where it is expressed in the initial steps of tumor progression) or for therapy purposes. Indeed, hERG1 blockage impairs tumor cell growth both in vitro and in vivo in preclinical mouse model. hERG1-based tumor therapy in humans, however, encounters the major hindrance of the potential cardiotoxicity that many hERG1 blockers exert. In this review we focus on recent advances in translational research in some of the most frequent human solid cancers (breast, endometrium, ovary, pancreas, esophagus, stomach, and colorectum) that have been shown to express hERG1 and that are a major health problem.

Gene expression analysis of skin grafts and cultured keratinocytes using synthetic RNA normalization reveals insights into differentiation and growth control

Background

Keratinocytes (KCs) are the most frequent cells in the epidermis, and they are often isolated and cultured in vitro to study the molecular biology of the skin. Cultured primary cells and various immortalized cells have been frequently used as skin models but their comparability to intact skin has been questioned. Moreover, when analyzing KC transcriptomes, fluctuation of polyA+ RNA content during the KCs’ lifecycle has been omitted.

Results

We performed STRT RNA sequencing on 10 ng samples of total RNA from three different sample types: i) epidermal tissue (split-thickness skin grafts), ii) cultured primary KCs, and iii) HaCaT cell line. We observed significant variation in cellular polyA+ RNA content between tissue and cell culture samples of KCs. The use of synthetic RNAs and SAMstrt in normalization enabled comparison of gene expression levels in the highly heterogenous samples and facilitated discovery of differences between the tissue samples and cultured cells. The transcriptome analysis sensitively revealed genes involved in KC differentiation in skin grafts and cell cycle regulation related genes in cultured KCs and emphasized the fluctuation of transcription factors and non-coding RNAs associated to sample types.

Conclusions

The epidermal keratinocytes derived from tissue and cell culture samples showed highly different polyA+ RNA contents. The use of SAMstrt and synthetic RNA based normalization allowed the comparison between tissue and cell culture samples and thus proved to be valuable tools for RNA-seq analysis with translational approach. Transciptomics revealed clear difference both between tissue and cell culture samples and between primary KCs and immortalized HaCaT cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1671-5) contains supplementary material, which is available to authorized users.

Voltage-gated ion channels in cancer cell proliferation

Changes of the electrical charges across the surface cell membrane are absolutely necessary to maintain cellular homeostasis in physiological as well as in pathological conditions. The opening of ion channels alter the charge distribution across the surface membrane as they allow the diffusion of ions such as K+, Ca++, Cl.

Bioelectrical regulation of cell cycle and the planarian model system

Cell cycle regulation through the manipulation of endogenous membrane potentials offers tremendous opportunities to control cellular processes during tissue repair and cancer formation. However, the molecular mechanisms by which biophysical signals modulate the cell cycle remain underappreciated and poorly understood. Cells in complex organisms generate and maintain a constant voltage gradient across the plasma membrane known as the transmembrane potential. This potential, generated through the combined efforts of various ion transporters, pumps and channels, is known to drive a wide range of cellular processes such as cellular proliferation, migration and tissue regeneration while its deregulation can lead to tumorigenesis. These cellular regulatory events, coordinated by ionic flow, correspond to a new and exciting field termed molecular bioelectricity. We aim to present a brief discussion on the biophysical machinery involving membrane potential and the mechanisms mediating cell cycle progression and cancer transformation. Furthermore, we present the planarian Schmidtea mediterranea as a tractable model system for understanding principles behind molecular bioelectricity at both the cellular and organismal level. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Ion channel expression as promising cancer biomarker

Cancer is a disease with marked heterogeneity in both response to therapy and survival. Clinical and histopathological characteristics have long determined prognosis and therapy. The introduction of molecular diagnostics has heralded an explosion in new prognostic factors. Overall, histopathology, immunohistochemistry and molecular biology techniques have described important new prognostic subgroups in the different cancer categories. Ion channels and transporters (ICT) are a new class of membrane proteins which are aberrantly expressed in several types of human cancers. Besides regulating different aspect of cancer cell behavior, ICT can now represent novel cancer biomarkers. A summary of the data obtained so far and relative to breast, prostate, lung, colorectal, esophagus, pancreatic and gastric cancers are reported. Special emphasis is given to those studies aimed at relating specific ICT or a peculiar ICT profile with current diagnostic methods. Overall, we are close to exploit ICTs for diagnostic, prognostic or predictive purposes in cancer. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Targeting potassium channels in cancer

Potassium channels are pore-forming transmembrane proteins that regulate a multitude of biological processes by controlling potassium flow across cell membranes. Aberrant potassium channel functions contribute to diseases such as epilepsy, cardiac arrhythmia, and neuromuscular symptoms collectively known as channelopathies. Increasing evidence suggests that cancer constitutes another category of channelopathies associated with dysregulated channel expression. Indeed, potassium channel–modulating agents have demonstrated antitumor efficacy. Potassium channels regulate cancer cell behaviors such as proliferation and migration through both canonical ion permeation–dependent and noncanonical ion permeation–independent functions. Given their cell surface localization and well-known pharmacology, pharmacological strategies to target potassium channel could prove to be promising cancer therapeutics.

Potassium channels in pancreatic duct epithelial cells: their role, function and pathophysiological relevance

Pancreatic ductal epithelial cells play a fundamental role in HCO3 (-) secretion, a process which is essential for maintaining the integrity of the pancreas. Although several studies have implicated impaired HCO3 (-) and fluid secretion as a triggering factor in the development of pancreatitis, the mechanism and regulation of HCO3 (-) secretion is still not completely understood. To date, most studies on the ion transporters that orchestrate ductal HCO3 (-) secretion have focussed on the role of Cl(-)/HCO3 (-) exchangers and Cl(-) channels, whereas much less is known about the role of K(+) channels. However, there is growing evidence that many types of K(+) channels are present in ductal cells where they have an essential role in establishing and maintaining the electrochemical driving force for anion secretion. For this reason, strategies that increase K(+) channel function may help to restore impaired HCO3 (-) and fluid secretion, such as in pancreatitis, and therefore provide novel directions for future pancreatic therapy. In this review, our aims are to summarize the types of K(+) channels found in pancreatic ductal cells and to discuss their individual roles in ductal HCO3 (-) secretion. We will also describe how K(+) channels are involved in pathophysiological conditions and discuss how they could act as new molecular targets for the development of therapeutic approaches to treat pancreatic diseases.