Eag1 channels as potential cancer biomarkers

Development of a nomogram for predicting postoperative recurrence of cervical intraepithelial neoplasia using immunohistochemical and clinical parameters

BACKGROUND

We aimed to develop a nomogram to predict abnormal follow-up results of co-testing for cytology and human papillomavirus (HPV) in cervical intraepithelial neoplasia (CIN) patients after conization.

RESEARCH DESIGN AND METHODS

Two hundred sixty-three patients initially diagnosed as CIN2+ were recruited. Data on immunohistochemical (IHC) staining scores, along with demographic and clinical information were collected. Using least absolute shrinkage and selection operator (LASSO) regression analysis, variables were identified for inclusion. A predict model and nomogram were developed through multi-factor logistic regression. The goodness-of-fit test was applied across different cohorts to construct the calibration curve of the model, and the predictive effect was evaluated by the receiver operating characteristic curve. Decision curve analysis was performed to determine the net benefit.

RESULTS

Five predictor variables, including protein expression score, vaginal infection, HPV coinfection, and cone height were screened and plotted as a nomogram. The calibration curves showed a good fit. The area under the curve of the model was 0.835 for the training cohort and 0.728 for the internal test cohort. The decision curve analysis indicated that the nomogram provides significant net advantages for clinical use.

CONCLUSION

A practical nomogram predict model was developed to predict abnormal follow-up outcomes in CINs after conization.

Immunohistochemistry staining of Eag1 and p16/Ki-67 can help improve the management of patients with cervical intraepithelial Neoplasia after cold knife conversion

BACKGROUND

Immunohistochemistry (IHC) is widely used in the management of patients with cervical intraepithelial neoplasia (CIN) but still has many limitations in clinical practice. We analyzed the correlation of new biomarkers with the severity of CIN and follow-up outcomes in patients after conization to improve the management of patients with CIN.

METHODS

IHC staining of Eag1 and p16/Ki-67 was performed on cervical tissue sections from 234 patients with suspected CIN2/3. After a series of follow-ups, including human papillomavirus (HPV) test and thinprep cytologic test (TCT) for 1-2 years, the outcomes were collected. IHC scores of biomarkers and follow-up results were used to analyze the correlation and assess the diagnostic efficiency of biomarkers.

RESULTS

The IHC staining intensity of Eag1 and p16/Ki-67 was significantly different from that of the CIN1-3 groups (p < 0.05). Eag1 expression scores were significantly different in the distribution between the two follow-up groups (p < 0.001). ROC curves based on the correlations between the follow-up outcomes and the Eag1 scores and IS of p16/ki-67 showed that Eag1 had a greater AUC (0.767 vs. 0.666). Logistic regression analysis of the combination of biomarkers revealed a greater AUC value than any single biomarker.

CONCLUSIONS

Eag1 expression was significantly correlated with CIN grade and follow-up outcomes after conization. IHC staining of combinations of biomarkers of Eag1, p16 and Ki-67 may help us to improve the ability to identify risk groups with abnormal follow-up outcomes after treatment for CIN.

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.

Advances in the role of ion channels in leukemia

Ion channels are widely present in cell membranes, serving as crucial pathways for the movement of ions enter and exit cells. Variations in the expression of ion channels are crucial for regulating cellular functions. Among the genes associated with leukemia, certain genes encode ion channels. When these ion channels experience dysfunction or changes in expression, they can impact the physiological functions and signal transduction of hematopoietic cells, thereby regulating leukemia cell proliferation, differentiation, invasion/migration, and apoptosis. This article will provide a comprehensive review of the research progress on the expression and function of various ion channels in leukemia, thoroughly exploring their roles and mechanisms in the onset and progression of the disease, providing new insights and ideas for identifying potential biomarkers and developing new treatment methods for leukemia, thereby promoting innovations in future leukemia diagnosis and therapy.

Circ_0016347 Promotes Osteosarcoma Progression by Regulating miR-1225-3p/KCNH1 Axis

Background: Osteosarcoma (OS) is a common malignant bone cancer and usually occurs in adolescents and children. Circular RNAs (circRNAs) play essential roles in tumor development and progression. This study aimed to explore the function and molecular basis of circ_0016347 in OS progression. Materials and Methods: The levels of circ_0016347, miR-1225-3p, and ether à go-go 1 (KCNH1) were measured by quantitative real-time polymerase chain reaction or Western blot assay. Cell proliferation was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and colony formation assay. Cell migration and invasion were evaluated by transwell assay. Glucose consumption and lactate production were detected by glucose detection and lactic acid detection kits. The levels of Ki-67, matrix metalloproteinase-9 (MMP-9), and hexokinase-2 (HK2) were examined by Western blot assay. The interaction among circ_0016347, miR-1225-3p, and KCNH1 was validated by dual-luciferase reporter assay. Xenograft assay was conducted to analyze tumor growth in vivo. Results: Circ_0016347 and KCNH1 were upregulated, while miR-1225-3p was downregulated in OS tissues or cells. Circ_0016347 and KCNH1 promoted proliferation, migration, invasion, and glycolysis of OS cells. Circ_0016347 regulated OS progression by modulating KCNH1. Circ_0016347 was a sponge of miR-1225-3p, and miR-1225-3p targeted KCNH1. Circ_0016347 regulated KCNH1 expression via sponging miR-1225-3p. Moreover, silencing of circ_0016347 inhibited tumor growth in vivo. Conclusion: Circ_0016347 contributed to OS progression through the miR-1225-3p/KCNH1 axis, which might provide a promising biomarker for OS therapy.

Potassium channels as novel molecular targets in hepatocellular carcinoma (Review)

Hepatocellular carcinoma (HCC) poses a serious health burden worldwide. It is often not diagnosed until the patient is at an advanced stage of the disease, when treatment options are limited and the prognosis is poor. Therefore, novel treatment strategies are urgently required. Potassium (K+) channels have an important role in HCC, including regulating the proliferation, migration, invasion and drug resistance of HCC cells. The aim of the present review was therefore to survey the relevant publications that have investigated K+ channels not only as markers for the early diagnosis of HCC, but also as potential therapeutic targets for the treatment of HCC. Several of these channels have been indicated to be the sites of action for natural products previously known to inhibit HCC; however, more systematic studies are required to determine which K+ channels may be utilized for the clinical treatment of HCC, particularly in the advanced stages of the disease and in cases where patients are resistant to the existing drugs.

Current and novel approaches in the pharmacological treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal malignant tumours worldwide. The mortality-to-incidence ratio is up to 91.6% in many countries, representing the third leading cause of cancer-related deaths. Systemic drugs, including the multikinase inhibitors sorafenib and lenvatinib, are first-line drugs used in HCC treatment. Unfortunately, these therapies are ineffective in most cases due to late diagnosis and the development of tumour resistance. Thus, novel pharmacological alternatives are urgently needed. For instance, immune checkpoint inhibitors have provided new approaches targeting cells of the immune system. Furthermore, monoclonal antibodies against programmed cell death-1 have shown benefits in HCC patients. In addition, drug combinations, including first-line treatment and immunotherapy, as well as drug repurposing, are promising novel therapeutic alternatives. Here, we review the current and novel pharmacological approaches to fight HCC. Preclinical studies, as well as approved and ongoing clinical trials for liver cancer treatment, are discussed. The pharmacological opportunities analysed here should lead to significant improvement in HCC therapy.

The Phytochemical α-Mangostin Inhibits Cervical Cancer Cell Proliferation and Tumor Growth by Downregulating E6/E7-HPV Oncogenes and KCNH1 Gene Expression

Cervical cancer is the fourth most common cancer among women worldwide. The main factor associated with the onset and progression of this neoplasia is the human papillomavirus (HPV) infection. The HPV-oncogenes E6 and E7 are critical drivers of cellular transformation, promoting the expression of oncogenes such as KCNH1. The phytochemical α-mangostin (AM) is a potent antineoplastic and antiviral compound. However, its effects on HPV oncogenes and KCNH1 gene expression remain unknown. This study evaluated the effects of AM on cell proliferation, cell cycle distribution and gene expression, including its effects on tumor growth in xenografted mice. AM inhibited cell proliferation in a concentration-dependent manner, being the most sensitive cell lines those with the highest number of HPV16 copies. In addition, AM promoted G1-cell cycle arrest in CaSki cells, while led to cell death in SiHa and HeLa cells. Of interest was the finding of an AM-dependent decreased gene expression of E6, E7 and KCNH1 both in vitro and in vivo, as well as the modulation of cytokine expression, Ki-67, and tumor growth inhibition. On these bases, we suggest that AM represents a good option as an adjuvant for the treatment and prevention of cervical cancer.

The role of mechanosensitive ion channels in the gastrointestinal tract

Mechanosensation is essential for normal gastrointestinal (GI) function, and abnormalities in mechanosensation are associated with GI disorders. There are several mechanosensitive ion channels in the GI tract, namely transient receptor potential (TRP) channels, Piezo channels, two-pore domain potassium (K2p) channels, voltage-gated ion channels, large-conductance Ca²⁺-activated K⁺ (BKCa) channels, and the cystic fibrosis transmembrane conductance regulator (CFTR). These channels are located in many mechanosensitive intestinal cell types, namely enterochromaffin (EC) cells, interstitial cells of Cajal (ICCs), smooth muscle cells (SMCs), and intrinsic and extrinsic enteric neurons. In these cells, mechanosensitive ion channels can alter transmembrane ion currents in response to mechanical forces, through a process known as mechanoelectrical coupling. Furthermore, mechanosensitive ion channels are often associated with a variety of GI tract disorders, including irritable bowel syndrome (IBS) and GI tumors. Mechanosensitive ion channels could therefore provide a new perspective for the treatment of GI diseases. This review aims to highlight recent research advances regarding the function of mechanosensitive ion channels in the GI tract. Moreover, it outlines the potential role of mechanosensitive ion channels in related diseases, while describing the current understanding of interactions between the GI tract and mechanosensitive ion channels.

Smart nanomaterials for cancer diagnosis and treatment

Innovations in nanomedicine has guided the improved outcomes for cancer diagnosis and therapy. However, frequent use of nanomaterials remains challenging due to specific limitations like non-targeted distribution causing low signal-to-noise ratio for diagnostics, complex fabrication, reduced-biocompatibility, decreased photostability, and systemic toxicity of nanomaterials within the body. Thus, better nanomaterial-systems with controlled physicochemical and biological properties, form the need of the hour. In this context, smart nanomaterials serve as promising solution, as they can be activated under specific exogenous or endogenous stimuli such as pH, temperature, enzymes, or a particular biological molecule. The properties of smart nanomaterials make them ideal candidates for various applications like biosensors, controlled drug release, and treatment of various diseases. Recently, smart nanomaterial-based cancer theranostic approaches have been developed, and they are displaying better selectivity and sensitivity with reduced side-effects in comparison to conventional methods. In cancer therapy, the smart nanomaterials-system only activates in response to tumor microenvironment (TME) and remains in deactivated state in normal cells, which further reduces the side-effects and systemic toxicities. Thus, the present review aims to describe the stimulus-based classification of smart nanomaterials, tumor microenvironment-responsive behaviour, and their up-to-date applications in cancer theranostics. Besides, present review addresses the development of various smart nanomaterials and their advantages for diagnosing and treating cancer. Here, we also discuss about the drug targeting and sustained drug release from nanocarriers, and different types of nanomaterials which have been engineered for this intent. Additionally, the present challenges and prospects of nanomaterials in effective cancer diagnosis and therapeutics have been discussed.

Effect of imipramine on ether à-go-go potassium channel (Kv1.10) expression in DU145 prostate cancer cells

In recent studies, it has been reported that ion channels play an important role in cancer formation. Therefore, it is possible that the use of pharmacological agents targeting ion channels will allow the development of new strategies for cancer treatment. In this study, we investigate the effect of imipramine on Eag1 channel expression in DU145 prostate cancer cells. Culture cells were divided into 4 groups as the control, 10, 50 and 75 µM imipramine. Eag1 channel currents and conductivity were determined by whole-cell patch-clamp technique and gene expression by real time-polymerase chain reaction (RT-PCR). Current records were taken before (at 0th minute, as control) and 10 min after imipramine administration to the cells. It was observed that all three doses of imipramine significantly reduced Eag1 currents and conductivity compared with the control. However, the differences between dose groups were not significant. Similarly, Eag1 channel protein expression was found to be significantly reduced for all three doses of imipramine compared with the control group, but there was no significant difference in gene expression between dose groups. Obtained results suggested that imipramine has the potential to be used as a pharmacological agent targeting the Eag1 channel in the treatment of prostate cancer.

Thallium-sensitive fluorescent assay reveals loperamide as a new inhibitor of the potassium channel Kv10.1

BACKGROUND

Ion channels have been proposed as therapeutic targets for different types of malignancies. One of the most studied ion channels in cancer is the voltage-gated potassium channel ether-à-go-go 1 or Kv10.1. Various studies have shown that Kv10.1 expression induces the proliferation of several cancer cell lines and in vivo tumor models, while blocking or silencing inhibits proliferation. Kv10.1 is a promising target for drug discovery modulators that could be used in cancer treatment. This work aimed to screen for new Kv10.1 channel modulators using a thallium influx-based assay.

METHODS

Pharmacological effects of small molecules on Kv10.1 channel activity were studied using a thallium-based fluorescent assay and patch-clamp electrophysiological recordings, both performed in HEK293 stably expressing the human Kv10.1 potassium channel.

RESULTS

In thallium-sensitive fluorescent assays, we found that the small molecules loperamide and amitriptyline exert a potent inhibition on the activity of the oncogenic potassium channel Kv10.1. These results were confirmed by electrophysiological recordings, which showed that loperamide and amitriptyline decreased the amplitude of Kv10.1 currents in a dose-dependent manner. Both drugs could be promising tools for further studies.

CONCLUSIONS

Thallium-sensitive fluorescent assay represents a reliable methodological tool for the primary screening of different molecules with potential activity on Kv10.1 channels or other K⁺ channels.

Modifications of Plasma Membrane Organization in Cancer Cells for Targeted Therapy

Modifications of the composition or organization of the cancer cell membrane seem to be a promising targeted therapy. This approach can significantly enhance drug uptake or intensify the response of cancer cells to chemotherapeutics. There are several methods enabling lipid bilayer modifications, e.g., pharmacological, physical, and mechanical. It is crucial to keep in mind the significance of drug resistance phenomenon, ion channel and specific receptor impact, and lipid bilayer organization in planning the cell membrane-targeted treatment. In this review, strategies based on cell membrane modulation or reorganization are presented as an alternative tool for future therapeutic protocols.

Membrane Transporters and Channels in Melanoma

Recent research has revealed that ion channels and transporters can be important players in tumor development, progression, and therapy resistance in melanoma. For example, members of the ABC family were shown to support cancer stemness-like features in melanoma cells, while several members of the TRP channel family were reported to act as tumor suppressors.Also, many transporter proteins support tumor cell viability and thus suppress apoptosis induction by anticancer therapy. Due to the high number of ion channels and transporters and the resulting high complexity of the field, progress in understanding is often focused on single molecules and is in total rather slow. In this review, we aim at giving an overview about a broad subset of ion transporters, also illustrating some aspects of the field, which have not been addressed in detail in melanoma. In context with the other chapters in this special issue on "Transportome Malfunctions in the Cancer Spectrum," a comparison between melanoma and these tumors will be possible.

Anticancer potential of new 3-nitroaryl-6-(N-methyl)piperazin-1,2,4-triazolo[3,4-a]phthalazines targeting voltage-gated K+ channel: Copper-catalyzed one-pot synthesis from 4-chloro-1-phthalazinyl-arylhydrazones

A series of six 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines were prepared through a facile and efficient one-pot copper-catalyzed procedure from 4-chloro-1-phthalazinyl-arylhydrazones with relatively good yields (62-83%). The one-pot copper-catalytic procedure consists of two simultaneous reactions: (i) a direct intramolecular dehydrogentaive cyclization between ylidenic carbon and adjacent pyrazine nitrogen to form 1,2,4-triazolo ring and, (ii) a direct N-amination on carbon-chlorine bond. Then, an in vitro anticancer evaluation was performed for the synthesized compounds against five selected human cancer cells (A549, MCF-7, SKBr3, PC-3 and HeLa). The nitro-derivatives were significantly more active against cancer strains than against the rest of tested compounds. Specifically, compound 8d was identified as the most promising anticancer agent with significant biological responses and low relative toxicities on human dermis fibroblast. The cytotoxic effect of compound 8d was more significant on PC3, MCF-7 and SKBr3 cancer cells with low-micromolar IC₅₀ value ranging from 0.11 to 0.59 μM, superior to Adriamycin drug. Mechanistic experimental and theoretical studies demonstrated that compounds 8d act as a K⁺ channel inhibitor in cancer models. Further molecular docking studies suggest that the EGFR Tyrosine Kinase enzyme may be a potential target for the most active 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines.

Procyanidin B1, a novel and specific inhibitor of Kv10.1 channel, suppresses the evolution of hepatoma

Recently, we and other groups revealed that aberrant expression of Kv10.1 channel, a voltage-gated potassium ion channel, contributes to a variety of tumorigenesis process.Potent and selective inhibitor of Kv10.1 is urgently needed, both as pharmacological tools for studying the physiological functions of this enigmatic channel and as potential leads for development of anti-tumor drugs. In this study, Procyanidin B1, a natural compound extracted from the grape seed, was identified as a potent, specific inhibitor, which can inhibit the Kv10.1 channel in a concentration-dependent manner (IC₅₀ = 10.38 ± 0.87 μM), but has negligible effects on other potassium channels, including Kir2.1, HERG or KCNQ1. It was demonstrated that Procyanidin B1 directly binds to Kv10.1 channel and inhibits its currents, without increasing intracellular Ca²⁺. Further, three amino acids, I550, T552, and Q557 in the C-linker domain of Kv10.1 were found critical for forming the binding pocket of Procyanidin B1 with Kv10.1 channel.In addition, Procyanidin B1 inhibits migration and proliferation of liver cancer cells (HuH-7 cells, HepG2 cells) through inhibiting Kv10.1, but not in Kv10.1 negatively expressed cell lines. Next, we assayed the tumor suppressing effect of Procyanidin B1 on cell line-derived xenograft mouse model. Our data showed that 15 mg/kg Procyanidin B1 can significantly suppress the growth of the tumor (HepG2) with an inhibition rate of about 60.25%. Compared with cisplatin, Procyanidin B1 has no side effect on the normal metabolismof the mice. The present work indicated that Procyanidin B1 is a proming liver cancer anti-tumor drug, and also confirmed that Kv10.1 can serve as a potential, tumor-specific drug target.

Effect of Imipramine on radiosensitivity of Prostate Cancer: An In Vitro Study

Prostate cancer is the most common cancer and leading cause of cancer death for males. Imipramine (IMI), which is a tricyclic antidepressant, has also been shown to has antineoplastic effect. This study was performed to investigate the radiosensitizing effect of IMI on DU145 prostate cancer cell. Cells were divided into 4 groups. Cell index, apoptotic activity, cell cycle arrest, oxidative stress and EAG1 channel currents were determined in all groups. Our findings showed that combined treatment with IMI and radiotherapy (RAD) did not enhance radiosensitivity of DU145 cells but as unexpected finding, treatment of IMI alone was more effective in DU145 cells.

Potassium and Sodium Channels and the Warburg Effect: Biophysical Regulation of Cancer Metabolism

Ion channels are progressively emerging as a novel class of membrane proteins expressed in several types of human cancers and regulating the different aspects of cancer cell behavior. The metabolism of cancer cells, usually composed by a variable proportion of respiration, glycolysis, and glutaminolysis, leads to the excessive production of acidic metabolic products. The presence of these acidic metabolites inside the cells results in intracellular acidosis, and hinders survival and proliferation. For this reason, tumor cells activate mechanisms of pH control that produce a constitutive increase in intracellular pH (pHi) that is more acidic than the extracellular pH (pHe). This condition forms a perfect microenvironment for metastatic progression and may be permissive for some of the acquired characteristics of tumors. Recent analyses have revealed complex interconnections between oncogenic activation, ion channels, hypoxia signaling and metabolic pathways that are dysregulated in cancer. Here, we summarize the molecular mechanisms of the Warburg effect and hypoxia and their association. Moreover, we discuss the recent findings concerning the involvement of ion channels in various aspects of the Warburg effect and hypoxia, focusing on the role of Na+ and K+ channels in hypoxic and metabolic reprogramming in cancer.

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

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

Chloroquine inhibits tumor-related Kv10.1 channel and decreases migration of MDA-MB-231 breast cancer cells in vitro

Chloroquine (CQ) is an old antimalarial drug currently being investigated for its anti-tumor properties. As chloroquine has been shown to inhibits several potassium channels, we decided to study its effect on the tumor-related Kv10.1 channel by using patch-clamp electrophysiology and cell migration assays. We found that chloroquine inhibited Kv10.1 channels transiently expressed in HEK-293 cells in a concentration- and voltage-dependent manner acting from the cytoplasmic side of the plasma membrane. Chloroquine also inhibited the outward potassium currents from MDA-MB-231 cells, which are mainly carried through Kv10.1 channels as was confirmed using astemizole. Additionally, chloroquine decreased MDA-MB-231 cell migration in the in vitro scratch wound healing assay. In conclusion, our data suggest that chloroquine decreases MDA-MB-231 cell migration by inhibiting Kv10.1 channels. The inhibition of Kv10.1 channels could represent another mechanism of the antitumoral action of chloroquine, besides autophagy inhibition and tumor vessel normalization.

Ion channels as therapeutic antibody targets

It is now well established that antibodies have numerous potential benefits when developed as therapeutics. Here, we evaluate the technical challenges of raising antibodies to membrane-spanning proteins together with enabling technologies that may facilitate the discovery of antibody therapeutics to ion channels. Additionally, we discuss the potential targeting opportunities in the anti-ion channel antibody landscape, along with a number of case studies where functional antibodies that target ion channels have been reported. Antibodies currently in development and progressing towards the clinic are highlighted.

The combination astemizole-gefitinib as a potential therapy for human lung cancer

Lung cancer is a major cause of cancer mortality. Thus, novel therapies are urgently needed. Repositioning of old drugs is gaining great interest in cancer treatment. Astemizole is an antihistamine proposed to be repositioned for cancer therapy. This drug targets several molecules involved in cancer including histamine receptors, ABC transporters and the potassium channels Eag1 and HERG. Astemizole inhibits the proliferation of different cancer cells including those from cervix, breast, leukemia and liver. Gefitinib is widely used to treat lung cancer; however, no response or drug resistance occurs in many cases. Here, we studied the combined effect of astemizole and gefitinib on the proliferation, survival, apoptosis and gene and protein expression of Eag1 channels in the human lung cancer cell lines A549 and NCI-H1975. Cell proliferation and survival were studied by the MTT method and the colony formation assay, respectively; apoptosis was investigated by flow cytometry. Gene expression was assessed by real-time polymerase chain reaction (RT-PCR), and protein expression was studied by Western blot analysis and immunocytochemistry. We obtained the inhibitory concentrations 20 and 50 (IC₂₀ and IC₅₀, respectively) values for each drug from the cell proliferation experiments. Drug combination at their IC₂₀ had a superior effect by reducing cell proliferation and survival in up to 80% and 100%, respectively. The drugs alone did not affect apoptosis of H1975 cells, but the drug combination at their IC₂₀ increased apoptosis roughly four times in comparison to the effect of the drugs alone. Eag1 mRNA levels and protein expression were decreased by the drug combination in A549 cells, and astemizole induced subcellular localization changes of the channel protein in these cells. Our in vitro studies strongly suggest that the combination astemizole–gefitinib may be a novel and promising therapy for lung cancer patients.

Zinc transporters and dysregulated channels in cancers

As a nutritionally essential metal ion, zinc (Zn) not only constitutes a structural element for more than 3000 proteins but also plays important regulatory functions in cellular signal transduction. Zn homeostasis is tightly controlled by regulating the flux of Zn across cell membranes through specific transporters, i.e. ZnT and ZIP family proteins. Zn deficiency and malfunction of Zn transporters have been associated with many chronic diseases including cancer. However, the mechanisms underlying Zn regulatory functions in cellular signaling and their impact on the pathogenesis and progression of cancers remain largely unknown. In addition to these acknowledged multifunctions, Zn modulates a wide range of ion channels that in turn may also play an important role in cancer biology. The goal of this review is to propose how zinc deficiency, through modified Zn homeostasis, transporter activity and the putative regulatory function of Zn can influence ion channel activity, and thereby contribute to carcinogenesis and tumorigenesis. This review intends to stimulate interest in, and support for research into the understanding of Zn-modulated channels in cancers, and to search for novel biomarkers facilitating effective clinical stratification of high risk cancer patients as well as improved prevention and therapy in this emerging field.

Eag1 channels as potential early-stage biomarkers of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide. HCC is usually asymptomatic at potential curative stages, and it has very poor prognosis if detected later. Thus, the identification of early biomarkers and novel therapies is essential to improve HCC patient survival. Ion channels have been proposed as potential tumor markers and therapeutic targets for several cancers including HCC. Especially, the ether à-go-go-1 (Eag1) voltage-gated potassium channel has been suggested as an early marker for HCC. Eag1 is overexpressed during HCC development from the cirrhotic and the preneoplastic lesions preceding HCC in a rat model. The channel is also overexpressed in human HCC. Astemizole has gained great interest as a potential anticancer drug because it targets several proteins involved in cancer including Eag1. Actually, in vivo studies have shown that astemizole may have clinical utility for HCC prevention and treatment. Here, we will review first some general aspects of HCC including the current biomarkers and therapies, and then we will focus on Eag1 channels as promising tools in the early diagnosis of HCC.

Guiding TRAIL to cancer cells through Kv10.1 potassium channel overcomes resistance to doxorubicin

Resisting cell death is one of the hallmarks of cancer, and represents a common problem resulting in ineffective cancer therapy. To overcome resistance to apoptosis, we designed an antibody-based therapy strategy using Kv10.1 as a target. Kv10.1 is a voltage-gated potassium channel, which has been identified as a tumor marker several years ago. The agent consists of a Kv10.1-specific single-chain antibody fused to the soluble tumor necrosis factor-related apoptosis-inducing ligand (scFv62-TRAIL). We combined scFv62-TRAIL with different chemotherapeutic drugs, all of which failed to induce apoptosis when used alone. In the combination, we could overcome the resistance and selectively induce apoptosis. Among the drugs, doxorubicin showed the most promising effect. Additionally, we observed improved efficacy by pre-treating the cells with doxorubicin before scFv62-TRAIL application. Expression analysis of the TRAIL death receptors suggests a doxorubicin-induced increase in the abundance of receptors as the mechanism for sensitization. Furthermore, we confirmed the anti-tumor effect and efficacy of our combination strategy in vivo in SCID mice bearing subcutaneous tumors. In conclusion, we propose a novel strategy to overcome resistance to chemotherapy in cancer cells. Doxorubicin and scFv62-TRAIL reciprocally sensitize the cells to each other, specifically in Kv10.1-positive tumor cells.

Differential regulation of human Eag1 channel expression by serum and epidermal growth factor in lung and breast cancer cells

Oncogenic ether à-go-go-1 (Eag1) potassium channels are overexpressed in most primary human solid tumors. Low oxygen and nutrient/growth factor concentrations play critical roles in tumorigenesis. However, the mechanisms by which tumor cells survive and proliferate under growth factor-depleted conditions remain elusive. Here, we investigated whether serum-deprived conditions and epidermal growth factor (EGF) regulate Eag1 expression in human lung and breast cancer cells. The human cancer cell lines A549 and MCF-7 (from the lungs and breast, respectively) were obtained from the American Type Culture Collection and cultured following the manufacturer’s recommendations. Eag1 gene and protein expression were studied by real-time PCR and immunocytochemistry, respectively. Cell proliferation was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and ERK1/2 phosphorylation was investigated by Western blot. Serum-deprived conditions increased Eag1 mRNA and protein expression in both cell lines. This Eag1 upregulation was prevented by EGF and the ERK1/2 inhibitor U0126 in only lung cancer cells; vascular endothelial growth factor did not prevent Eag1 upregulation. Our results suggest that Eag1 may act as a survival and mitogenic factor under low-serum and nutrient conditions and may be a clinical target during the early stages of tumor development.

Differential Expression of Ion Channels and Transporters During Hepatocellular Carcinoma Development

BACKGROUND

Ion channels and transporters are potential markers and therapeutic targets for several cancers. However, their expression during hepatocellular carcinoma (HCC) development remains unclear.

AIM

To investigate the mRNA expression of Na(+), K(+) and Ca(2+) channels and ABC transporters during rat HCC development, as well as Abcc3 protein in human liver biopsies.

METHODS

Wistar rats were treated with diethylnitrosamine (DEN) and developed both cirrhosis (12 weeks of treatment) and either pre-neoplastic lesions (16 weeks of treatment) or multinodular HCC (16 weeks of treatment plus 2 weeks DEN-free). The mRNA expression of 12 ion channels and two ABC transporters was studied using real-time RT-PCR. Tumor-containing or tumor-free liver sections were isolated by laser-capture microdissection. Abcc3 protein expression was studied by immunohistochemistry in healthy, cirrhotic and HCC human biopsies.

RESULTS

We observed expression changes in seven genes. Kcna3, Kcnn4, Kcnrg and Kcnj11 potassium channel mRNA expression reached peak values at the end of DEN treatment, while Scn2a1 sodium channel, Trpc6 calcium channel and Abcc3 transporter mRNA expression reached their highest levels in the presence of HCC (18 weeks). Whereas Kcnn4 and Scn2a1 channel expression was similar in non-tumor and tumor tissue, the Abcc3 transporter and Kcna3 potassium channels were preferentially overexpressed in the tumor sections. We observed differential Abcc3 protein subcellular localization and expression in human samples.

CONCLUSIONS

The ion channel/transporter expression profile observed suggests that these genes are potential early markers or therapeutic targets of HCC. The differential localization of Abcc3 may be useful in the diagnosis of cirrhosis and HCC.

Astemizole-based anticancer therapy for hepatocellular carcinoma (HCC), and Eag1 channels as potential early-stage markers of HCC

Hepatocellular carcinoma (HCC) has very poor prognosis. Astemizole has gained great interest as a potential anticancer drug because it targets several proteins involved in cancer including the Eag1 (ether à-go-go-1) potassium channel that is overexpressed in human HCC. Eag1 channels are regulated by cancer etiological factors and have been proposed as early tumor markers. Here, we found that HepG2 and HuH-7 HCC cells displayed Eag1 messenger RNA (mRNA) and protein expression, determined by real-time RT-PCR and immunochemistry, respectively. Astemizole inhibited human HCC cell proliferation (assessed by metabolic activity assay) and induced apoptosis (studied with flow cytometry) in both cell lines. The subcellular Eag1 protein localization was modified by astemizole in the HepG2 cells. The treatment with astemizole prevented diethylnitrosamine (DEN)-induced rat HCC development in vivo (followed by studying γ-glutamyl transpeptidase (GGT) activity). The Eag1 mRNA and protein levels were increased in most DEN-treated groups but decreased after astemizole treatment. GGT activity was decreased by astemizole. The Eag1 protein was detected in cirrhotic and dysplastic rat livers. Astemizole might have clinical utility for HCC prevention and treatment, and Eag1 channels may be potential early HCC biomarkers. These data provide significant basis to include astemizole in HCC clinical trials.

L-Type Ca(2+) Channels and SK Channels in Mouse Embryonic Stem Cells and Their Contribution to Cell Proliferation

Mouse embryonic stem cells (mESCs) are capable of both self-renewal and multilineage differentiation; thus, they can be expanded in vivo or in vitro and differentiated to produce different cell types. Despite their biological and medical interest, many physiological properties of undifferentiated mESCs, such as ion channel function, are not fully understood. Ion channels are thought to be involved in cell proliferation and differentiation. The aim of this study was to characterize functional ion channels in cultured undifferentiated mESCs and their role in cell proliferation. L-type voltage-activated Ca(2+) channels sensitive to nifedipine and small-conductance Ca(2+)-activated K(+) (SK) channels sensitive to apamin were identified. Ca(2+)-activated K(+) currents were blocked by millimolar concentrations of tetraethylammonium. The effects of Ca(2+) channel and Ca(2+)-activated K(+) channel blockers on the proliferation of undifferentiated mESCs were investigated by bromodeoxyuridine (BrdU) incorporation. Dihydropyridine derivatives, such as nifedipine, inhibited cell growth and BrdU incorporation into the cells, whereas apamin, which selectively blocks SK channels, had no effect on cell growth. These results demonstrate that functional voltage-operated Ca(2+) channels and Ca(2+)-activated K(+) channels are present in undifferentiated mESCs. Moreover, voltage-gated L-type Ca(2+) channels, but not SK channels, might be necessary for proliferation of undifferentiated mESCs.

A sustained increase in the intracellular Ca²⁺ concentration induces proteolytic cleavage of EAG2 channel

Voltage-gated EAG2 channel is abundant in the brain and enhances cancer cell growth by controlling cell volume. The channel contains a cyclic nucleotide-binding homology (CNBH) domain and multiple calmodulin-binding motifs. Here we show that a raised intracellular Ca(2+) concentration causes proteolytic digestion of heterologously expressed and native EAG2 channels. A treatment of EAG2-expressing cells with the Ca(2+) ionophore A23187 for 1h reduces the full-length protein by ∼80% with a concomitant appearance of 30-35-kDa peptides. Similarly, a treatment with the Ca(2+)-ATPase inhibitor thapsigargin for 3h removes 30-35-kDa peptides from ∼1/3 of the channel protein. Moreover, an incubation of the isolated rat brain membrane with CaCl2 leads to the generation of fragments with similar sizes. This Ca(2+)-induced digestion is not seen with EAG1. Mutations in a C-terminal calmodulin-binding motif alter the degrees and positions of the cleavage. Truncated channels that mimic the digested proteins exhibit a reduced current density and altered channel gating. In particular, these shorter channels lack a rapid activation typical in EAG channels with more than 20-mV positive shifts in voltage dependence of activation. The truncation also eliminates the ability of EAG2 channel to reduce cell volume. These results suggest that a sustained increase in the intracellular Ca(2+) concentration leads to proteolytic cleavage at the C-terminal cytosolic region following the CNBH domain by altering its interaction with calmodulin. The observed Ca(2+)-induced proteolytic cleavage of EAG2 channel may act as an adaptive response under physiological and/or pathological conditions.

Oxidative modulation of voltage-gated potassium channels

SIGNIFICANCE

Voltage-gated K+ channels are a large family of K+-selective ion channel protein complexes that open on membrane depolarization. These K+ channels are expressed in diverse tissues and their function is vital for numerous physiological processes, in particular of neurons and muscle cells. Potentially reversible oxidative regulation of voltage-gated K+ channels by reactive species such as reactive oxygen species (ROS) represents a contributing mechanism of normal cellular plasticity and may play important roles in diverse pathologies including neurodegenerative diseases.

RECENT ADVANCES

Studies using various protocols of oxidative modification, site-directed mutagenesis, and structural and kinetic modeling provide a broader phenomenology and emerging mechanistic insights.

CRITICAL ISSUES

Physicochemical mechanisms of the functional consequences of oxidative modifications of voltage-gated K+ channels are only beginning to be revealed. In vivo documentation of oxidative modifications of specific amino-acid residues of various voltage-gated K+ channel proteins, including the target specificity issue, is largely absent.

FUTURE DIRECTIONS

High-resolution chemical and proteomic analysis of ion channel proteins with respect to oxidative modification combined with ongoing studies on channel structure and function will provide a better understanding of how the function of voltage-gated K+ channels is tuned by ROS and the corresponding reducing enzymes to meet cellular needs.

Potassium channel ether à go-go1 is aberrantly expressed in human liposarcoma and promotes tumorigenesis

The ether à go-go1 (Eag1) channel is overexpressed in a variety of cancers. However, the expression and function of Eag1 in liposarcoma are poorly understood. In the present study, the mRNA expression of Eag1 in different adipose tissue samples was examined by real-time PCR. Then, the protein expression of Eag1 in 131 different adipose tissues from 109 patients was detected by immunohistochemistry. Next, the associations between Eag1 expression and clinicopathological features of liposarcoma were analyzed. In addition, the effects of Eag1 on liposarcoma cell proliferation and cycle were evaluated by CCK-8, colony formation, xenograft mouse model, and flow cytometry, respectively. Finally, the activation of p38 mitogen-activated protein kinase (MAPK) was detected by Western blot analysis to explain the detailed mechanisms of oncogenic potential of Eag1 in liposarcoma. It was found that Eag1 was aberrantly expressed in over 67% liposarcomas, with a higher frequency than in lipoma, hyperplasia, inflammation, and normal adipose tissues. However, Eag1 expression was not correlated with clinicopathological features of liposarcoma. Eag1 inhibitor imipramine or Eag1-shRNA significantly suppressed the proliferation of liposarcoma cells in vitro and in vivo, accompanying with accumulation of cells in the G1 phase. These results suggest that Eag1 plays an important role in regulating the proliferation and cell cycle of liposarcoma cells and might be a potential therapeutic target for liposarcoma.

Antiproliferative and Proapoptotic Effects of Astemizole on Cervical Cancer Cells

Objective

Cervical cancer is a major cause of mortality among women in developing countries. Thus, it is necessary to offer novel therapies to treat this malignancy. Astemizole has been suggested as a novel and interesting anticancer agent because it targets several proteins involved in cancer including Eag1 (ether à-go-go-1) potassium channels. Eag1 has been proposed as a tumor marker for different types of cancer. Actually, we previously suggested Eag1 channels as cervical cancer and dysplasia markers. Besides, Eag1 has been proposed as a therapeutic target for different malignancies. However, the effect of astemizole in cervical cancer cells is unknown. Therefore, we investigated the effect of astemizole on the proliferation and apoptosis of cervical cancer cells.

Methods

Five cervical cancer cell lines (HeLa, SiHa, CaSki, INBL, and C-33A) were cultured according to manufacturer’s instructions. Eag1 protein expression was studied by immunocytochemistry. Cell proliferation was assayed with the MTT method, and apoptosis was investigated by flow cytometry.

Results

Eag1 protein expression was observed in different cell lines. Astemizole decreased cell proliferation in up to 40% and increased apoptosis severalfold in all the cell lines studied.

Conclusions

Our results suggest astemizole as a potential therapy for cervical cancer.

Retrotransposon hypomethylation in melanoma and expression of a placenta-specific gene

In the human placenta, DNA hypomethylation permits the expression of retrotransposon-derived genes that are normally silenced by methylation in somatic tissues. We previously identified hypomethylation of a retrotransposon-derived transcript of the voltage-gated potassium channel gene KCNH5 that is expressed only in human placenta. However, an RNA sequence from this placental-specific transcript has been reported in melanoma. This study examined the promoter methylation and expression of the retrotransposon-derived KCNH5 transcript in 25 melanoma cell lines to determine whether the acquisition of 'placental' epigenetic marks is a feature of melanoma. Methylation and gene expression analysis revealed hypomethylation of this retrotransposon in melanoma cell lines, particularly in those samples that express the placental KCNH5 transcript. Therefore we propose that hypomethylation of the placental-specific KCNH5 promoter is frequently associated with KCNH5 expression in melanoma cells. Our findings show that melanoma can develop hypomethylation of a retrotransposon-derived gene; a characteristic notably shared with the normal placenta.

KCNH1 potassium channels are expressed in cervical cytologies from pregnant patients and are regulated by progesterone

Potassium voltage-gated channel, subfamily H (eag-related), member 1 (KCNH1) potassium channels are potential tumour markers and cancer therapeutic targets and are up-regulated by oestrogens and human papilloma virus (HPV) oncogenes. However, the role of KCNH1 in normal tissues is poorly understood, and its expression in pregnancy is unknown. We wondered whether KCNH1 channels are expressed in cervical cells from pregnant patients and whether progesterone (P4) regulates KCNH1. The association with HPV was also investigated. KCNH1 protein expression was studied by immunocytochemistry in liquid-based cervical cytologies; 93 samples were obtained from pregnant patients at different trimesters, and 15 samples were obtained from non-pregnant women (controls). The presence ofHPVwas studied by PCR with direct sequencing and nested multiplex PCR. HeLa cervical cancer cells were transfected with human progesterone receptor-B (PR-B) and treated with P4.KCNH1mRNA expression in these cultures was studied by real-time PCR. KCNH1 protein was detected in 100% of the pregnancy samples and in 26% of the controls. We found 18 pregnant patients infected with HPV and detected 14 types ofHPV. There was no association between the percentage of cells expressing KCNH1 and either the presence or type of HPV. P4induced KCNH1 mRNA and protein expression in cells transfected with human PR-B. No regulation of KCNH1 by P4was observed in non-transfected cells. We show for the first time the expression of an ion channel during human pregnancy at different trimesters and KCNH1 regulation by P4in human cells. These data raise a new research field for KCNH1 channels in human tissues.

Altered expression of two-pore domain potassium (K2P) channels in cancer

Potassium channels have become a focus in cancer biology as they play roles in cell behaviours associated with cancer progression, including proliferation, migration and apoptosis. Two-pore domain (K_2P) potassium channels are background channels which enable the leak of potassium ions from cells. As these channels are open at rest they have a profound effect on cellular membrane potential and subsequently the electrical activity and behaviour of cells in which they are expressed. The K_2P family of channels has 15 mammalian members and already 4 members of this family (K_2P2.1, K_2P3.1, K_2P9.1, K_2P5.1) have been implicated in cancer. Here we examine the expression of all 15 members of the K_2P family of channels in a range of cancer types. This was achieved using the online cancer microarray database, Oncomine (www.oncomine.org). Each gene was examined across 20 cancer types, comparing mRNA expression in cancer to normal tissue. This analysis revealed all but 3 K_2P family members (K_2P4.1, K_2P16.1, K_2P18.1) show altered expression in cancer. Overexpression of K_2P channels was observed in a range of cancers including breast, leukaemia and lung while more cancers (brain, colorectal, gastrointestinal, kidney, lung, melanoma, oesophageal) showed underexpression of one or more channels. K_2P1.1, K_2P3.1, K_2P12.1, were overexpressed in a range of cancers. While K_2P1.1, K_2P3.1, K_2P5.1, K_2P6.1, K_2P7.1 and K_2P10.1 showed significant underexpression across the cancer types examined. This analysis supports the view that specific K_2P channels may play a role in cancer biology. Their altered expression together with their ability to impact the function of other ion channels and their sensitivity to environmental stimuli (pO2, pH, glucose, stretch) makes understanding the role these channels play in cancer of key importance.

Membrane potential and cancer progression

Membrane potential (V_m), the voltage across the plasma membrane, arises because of the presence of different ion channels/transporters with specific ion selectivity and permeability. V_m is a key biophysical signal in non-excitable cells, modulating important cellular activities, such as proliferation and differentiation. Therefore, the multiplicities of various ion channels/transporters expressed on different cells are finely tuned in order to regulate the V_m. It is well-established that cancer cells possess distinct bioelectrical properties. Notably, electrophysiological analyses in many cancer cell types have revealed a depolarized V_m that favors cell proliferation. Ion channels/transporters control cell volume and migration, and emerging data also suggest that the level of V_m has functional roles in cancer cell migration. In addition, hyperpolarization is necessary for stem cell differentiation. For example, both osteogenesis and adipogenesis are hindered in human mesenchymal stem cells (hMSCs) under depolarizing conditions. Therefore, in the context of cancer, membrane depolarization might be important for the emergence and maintenance of cancer stem cells (CSCs), giving rise to sustained tumor growth. This review aims to provide a broad understanding of the V_m as a bioelectrical signal in cancer cells by examining several key types of ion channels that contribute to its regulation. The mechanisms by which V_m regulates cancer cell proliferation, migration, and differentiation will be discussed. In the long term, V_m might be a valuable clinical marker for tumor detection with prognostic value, and could even be artificially modified in order to inhibit tumor growth and metastasis.

Cell proliferation, potassium channels, polyamines and their interactions: a mini review

Polyamines, which are obligatory molecules involved in cell cycling and proliferation, are subject to a change in their free intracellular concentrations during the cell cycle. Potassium (K(+)) channels are also considered, but less well recognized, to be necessary for cell proliferation by either hyperpolarizing or depolarizing cells during the cell cycle. A block of polyamine synthesis as well as block or knockout of K(+) channels can halt cell proliferation. K(+) channels like BK (maxi calcium (Ca(2+))-activated K(+)), Kir (inward rectifier), M-type K(+)-and TASK (two-pore domain K(+)) channels or the delayed rectifier K(+) channels are modulated in their electrical properties by polyamines. Polyamines are most effective in blocking these channels when applied to the intracellular face of these channels except for TASK channels where they act only from the extracellular side. Quinidine, a general K(+) channel blocker, was found to reduce putrescine concentrations, to block the ornithine decarboxylase and halt cell proliferation. From these results, the question arises if there is an interaction between polyamines, K(+) channels and proliferation. It might be speculated that a decrease of intracellular polyamines allows more K(+) channels to be active, thus inducing hyperpolarization, while an increase of the polyamine concentration may block K(+) channel activity leading to depolarization of the membrane potential. On the other hand, a block or a deletion of K(+) channels may cause a decrease of the polyamine concentration in cells. More research is needed to test these hypotheses.

Behavioural and functional characterization of Kv10.1 (Eag1) knockout mice

K_v10.1 (Eag1), member of the K_v10 family of voltage-gated potassium channels, is preferentially expressed in adult brain. The aim of the present study was to unravel the functional role of K_v10.1 in the brain by generating knockout mice, where the voltage sensor and pore region of K_v10.1 were removed to render non-functional proteins through deletion of exon 7 of the KCNH1 gene using the ‘3 Lox P strategy’. K_v10.1-deficient mice show no obvious alterations during embryogenesis and develop normally to adulthood; cortex, hippocampus and cerebellum appear anatomically normal. Other tests, including general health screen, sensorimotor functioning and gating, anxiety, social behaviour, learning and memory did not show any functional aberrations in K_v10.1 null mice. K_v10.1 null mice display mild hyperactivity and longer-lasting haloperidol-induced catalepsy, but there was no difference between genotypes in amphetamine sensitization and withdrawal, reactivity to apomorphine and haloperidol in the prepulse inhibition tests or to antidepressants in the haloperidol-induced catalepsy. Furthermore, electrical properties of K_v10.1 in cerebellar Purkinje cells did not show any difference between genotypes. Bearing in mind that K_v10.1 is overexpressed in over 70% of all human tumours and that its inhibition leads to a reduced tumour cell proliferation, the fact that deletion of K_v10.1 does not show a marked phenotype is a prerequisite for utilizing K_v10.1 blocking and/or reduction techniques, such as siRNA, to treat cancer.