A monoclonal antibody against KCNK9 K(+) channel extracellular domain inhibits tumour growth and metastasis

The TWIK-related acid sensitive potassium 3 (TASK-3) channel contributes to the different effects of anesthetics on the growth and metastasis of ovarian cancer cells

Different anesthetics exert different effects on the long-term outcomes of various cancers. The TWIK-related acid sensitive potassium 3 (TASK-3) channel is an important target of anesthetics and is upregulated in various cancers. However, the role and underlying mechanism of TASK-3 channel in the effects of anesthetics on ovarian cancer remain unknown. Here, we tested whether the TASK-3 channel contributes to the effects of anesthetics on ovarian cancers. We found that the TASK-3 channel was overexpressed in human ovarian cancer and ovarian cancer cell lines. Clinically relevant concentrations of lidocaine, as a TASK-3 channel inhibitor, exert inhibitory effects on tumor growth and metastasis of ovarian cancer cells in vitro and in vivo, whereas the TASK-3 channel potent activator sevoflurane had protumor effects and propofol had no significant effects on tumor growth and metastasis of ovarian cancer. Knockdown of the TASK-3 channel by TASK-3 shRNA attenuated the effects of lidocaine and sevoflurane. Moreover, mitochondrial TASK-3 channel contributes to the effects of lidocaine and sevoflurane on the mitochondrial functions of ovarian cancer. Taken together, the TASK-3 channel, especially the mitochondrial TASK-3 (MitoTASK-3) channel, is a molecular substrate for the effects of lidocaine and sevoflurane on the tumor growth and metastasis of ovarian cancer.

TASK-3, two-pore potassium channels, contribute to circadian rhythms in the electrical properties of the suprachiasmatic nucleus and play a role in driving stable behavioural photic entrainment

Stable and entrainable physiological circadian rhythms are crucial for overall health and well-being. The suprachiasmatic nucleus (SCN), the primary circadian pacemaker in mammals, consists of diverse neuron types that collectively generate a circadian profile of electrical activity. However, the mechanisms underlying the regulation of endogenous neuronal excitability in the SCN remain unclear. Two-pore domain potassium channels (K2P), including TASK-3, are known to play a significant role in maintaining SCN diurnal homeostasis by inhibiting neuronal activity at night. In this study, we investigated the role of TASK-3 in SCN circadian neuronal regulation and behavioural photoentrainment using a TASK-3 global knockout mouse model. Our findings demonstrate the importance of TASK-3 in maintaining SCN hyperpolarization during the night and establishing SCN sensitivity to glutamate. Specifically, we observed that TASK-3 knockout mice lacked diurnal variation in resting membrane potential and exhibited altered glutamate sensitivity both in vivo and in vitro. Interestingly, despite these changes, the mice lacking TASK-3 were still able to maintain relatively normal circadian behaviour.

Differential RNA Expression Between Metastatic and Primary Neuroblastoma Cells

INTRODUCTION

Neuroblastoma (NB) is the most common extra-cranial malignancy in children. Poor survival in high-risk NB is attributed to recurrent metastatic disease. To better study metastatic disease, we used a novel mouse model to investigate differential gene expression between primary tumor cells and metastatic cells. We hypothesized that metastatic NB cells have a different gene expression profile from primary tumor cells and cultured cells.

METHODS

Using three human NB cell lines (NGP, CHLA255, and SH-SY5Y), orthotopic xenografts were established in immunodeficient nod/scid gamma mice via subcapsular renal injection. Mice were sacrificed and NB cells were isolated from the primary tumor and from sites of metastasis (bone marrow, liver). RNA sequencing, gene set analysis, and pathway analysis were performed to identify differentially expressed genes and molecular pathways in the metastatic cells compared to primary tumor cells.

RESULTS

There were 266 differentially expressed genes in metastatic tumor cells (bone marrow and liver combined) compared to primary tumor cells. The top upregulated gene was KCNK1 and the top downregulated genes were PDE7B and NEBL. Top upregulated pathways in the metastatic cells were involved in ion transport, cell signaling, and cell proliferation. Top downregulated pathways were involved in DNA synthesis, transcription, and cellular metabolism.

CONCLUSIONS

In metastatic NB cells, our study identified the upregulation of biologic processes involved in cell cycle regulation, cell proliferation, migration, and invasion. Ongoing studies aim to validate downstream translation of these genomic alterations, as well as target these pathways to more effectively suppress and inhibit recurrent metastatic disease in NB.

Former smoking associated with epigenetic modifications in human granulosa cells among women undergoing assisted reproduction

Smoking exposure during adulthood can disrupt oocyte development in women, contributing to infertility and possibly adverse birth outcomes. Some of these effects may be reflected in epigenome profiles in granulosa cells (GCs) in human follicular fluid. We compared the epigenetic modifications throughout the genome in GCs from women who were former (N = 15) versus never smokers (N = 44) undergoing assisted reproductive technologies (ART). This study included 59 women undergoing ART. Smoking history including time since quitting was determined by questionnaire. GCs were collected during oocyte retrieval and DNA methylation (DNAm) levels were profiled using the Infinium MethylationEPIC BeadChip. We performed an epigenome-wide association study with robust linear models, regressing DNAm level at individual loci on smoking status, adjusting for age, ovarian stimulation protocol, and three surrogate variables. We performed differentially methylated regions (DMRs) analysis and over-representation analysis of the identified CpGs and corresponding gene set. 81 CpGs were differentially methylated among former smokers compared to never smokers (FDR < 0.05). We identified 2 significant DMRs (KCNQ1 and RHBDD2). The former smoking-associated genes were enriched in oxytocin signaling, adrenergic signaling in cardiomyocytes, platelet activation, axon guidance, and chemokine signaling pathway. These epigenetic variations have been associated with inflammatory responses, reproductive outcomes, cancer development, neurodevelopmental disorder, and cardiometabolic health. Secondarily, we examined the relationships between time since quitting and DNAm at significant CpGs. We observed three CpGs in negative associations with the length of quitting smoking (p < 0.05), which were cg04254052 (KCNIP1), cg22875371 (OGDHL), and cg27289628 (LOC148145), while one in positive association, which was cg13487862 (PLXNB1). As a pilot study, we demonstrated epigenetic modifications associated with former smoking in GCs. The study is informative to potential biological pathways underlying the documented association between smoking and female infertility and biomarker discovery for smoking-associated reproductive outcomes.

Hydroquinidine Demonstrates Remarkable Antineoplastic Effects on Non-small Cell Lung Cancer Cells

BACKGROUND

Despite recent progress in drug development, lung cancer remains a complex disease that poses a major public health issue worldwide, and new therapeutic strategies are urgently needed because of the failure of standard treatments. Ion channels play a critical role in various cellular processes that regulate cell proliferation, differentiation, and cell death.

OBJECTIVES

The potential of ion channel modulators as tumor growth suppressors has been highlighted in recent studies. Therefore, we hypothesized that hydroquinidine (HQ), a previously understudied potassium channel modulator, might have anticarcinogenic activity against A549 cells.

METHODS

The anticancer potential of HQ was investigated using various wellestablished in vitro assays.

RESULTS

HQ significantly decreased colony formation and tumorigenicity and exhibited a significant anti-migratory effect in A549 cells. Our results demonstrated that HQ significantly inhibited the growth of cancer cells by decreasing the proliferation rate while increasing cell death. The altered gene expression profile in response to treatment with HQ was consistent with the observed cellular effects. Incubation of cells with HQ resulted in the downregulation of genes involved in cell division and survival, while genes promoting cell cycle arrest and apoptosis were upregulated.

CONCLUSION

Our findings suggest that HQ has the potential to limit lung cancer growth as a novel potent anticarcinogenic agent. However, more investigations are needed to gain further insight into the mechanism of action of HQ and to evaluate its efficacy in invivo models.

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

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

Potassium channels, tumorigenesis and targeted drugs

Potassium channels play an important role in human physiological function. Recently, various molecular mechanisms have implicated abnormal functioning of potassium channels in the proliferation, migration, invasion, apoptosis, and cancer stem cell phenotype formation. Potassium channels also mediate the association of tumor cells with the tumor microenvironment. Meanwhile, potassium channels are important targets for cancer chemotherapy. A variety of drugs exert anti-cancer effects by modulating potassium channels in tumor cells. Therefore, there is a need to understand how potassium channels participate in tumor development and progression, which could reveal new, novel targets for cancer diagnosis and treatment. This review summarizes the roles of voltage-gated potassium channels, calcium-activated potassium channels, inwardly rectifying potassium channels, and two-pore domain potassium channels in tumorigenesis and the underlying mechanism of potassium channel-targeted drugs. Therefore, the study lays the foundation for rational and effective drug design and individualized clinical therapeutics.

Potassium channels: Novel targets for tumor diagnosis and chemoresistance

In recent years, the role of potassium channels in tumors has been intensively studied. Potassium channel proteins are widely involved in various physiological and pathological processes of cells. The expression and dysfunction of potassium channels are closely related to tumor progression. Potassium channel blockers or activators present antitumor effects by directly inhibiting tumor growth or enhancing the potency of classical antitumor agents in combination therapy. This article reviews the mechanisms by which potassium channels contribute to tumor development in various tumors in recent years, introduces the potential of potassium channels as diagnostic targets and therapeutic means for tumors, and provides further ideas for the proper individualized treatment of tumors.

Conformational plasticity of NaK2K and TREK2 potassium channel selectivity filters

The K+ channel selectivity filter (SF) is defined by TxGYG amino acid sequences that generate four identical K+ binding sites (S1-S4). Only two sites (S3, S4) are present in the non-selective bacterial NaK channel, but a four-site K+-selective SF is obtained by mutating the wild-type TVGDGN SF sequence to a canonical K+ channel TVGYGD sequence (NaK2K mutant). Using single molecule FRET (smFRET), we show that the SF of NaK2K, but not of non-selective NaK, is ion-dependent, with the constricted SF configuration stabilized in high K+ conditions. Patch-clamp electrophysiology and non-canonical fluorescent amino acid incorporation show that NaK2K selectivity is reduced by crosslinking to limit SF conformational movement. Finally, the eukaryotic K+ channel TREK2 SF exhibits essentially identical smFRET-reported ion-dependent conformations as in prokaryotic K+ channels. Our results establish the generality of K+-induced SF conformational stability across the K+ channel superfamily, and introduce an approach to study manipulation of channel selectivity.

Identification of KCNK1 as a potential prognostic biomarker and therapeutic target of breast cancer

BACKGROUND

Breast cancer is the most common malignant cancer and is the second most common cause of cancer-related deaths among females worldwide. Thus, it warrants the urgent development of new therapeutic targets and strategies. Potassium channels are aberrantly expressed in various tumors and are related to tumor progression. However, studies on potassium channels in breast cancer remain limited.

METHOD

First, The Cancer Genome Atlas (TCGA) and Gene Set Enrichment Analysis (GSEA) were used to screen the differentially expressed potassium channels in breast cancer. Several other databases were utilized for further data analysis and visualization, including Gene Expression Profiling Interactive Analysis 2 (GEPIA2), Human Protein Atlas (HPA), GeneMANIA, Tumor Immune Estimation Resource 2 (TIMER2), Catalog of Somatic Mutations in Cancer (COSMIC), cBioPortal, and UCSC Xena tool. Besides, cell proliferation was detected by cell counting kit-8 (CCK8) and 5-Ethynyl-20-deoxyuridine (EdU), and cell migration was detected by wound healing and Transwell assays after knocking down KCNK1. Furthermore, the effect of KCNK1 knockdown on the sensitivity of breast cancer cells to paclitaxel was also evaluated.

RESULT

KCNK1 was overexpressed in breast cancer. Higher KCNK1 expression predicted an unfavorable prognosis. Moreover, the abnormal expression of KCNK1 was attributed to promoter hypomethylation of KCNK1 in breast cancer. Besides, cell proliferation and migration were significantly inhibited post-KCNK1 silencing, while KCNK1 knockdown significantly increased breast cancer cell sensitivity to paclitaxel.

CONCLUSION

Taken together, our findings demonstrated that KCNK1 is a potential prognostic biomarker and therapeutic target of breast cancer. Thus, targeting KCNK1 might help synergize with paclitaxel function in breast cancer treatment.

KCNK9 mediates the inhibitory effects of genistein on hepatic metastasis from colon cancer

OBJECTIVE

The tyrosine-protein kinase inhibitor, genistein, can inhibit cell malignant transformation and has an antitumor effect on various types of cancer. It has been shown that both genistein and KNCK9 can inhibit colon cancer. This research aimed to investigate the suppressive effects of genistein on colon cancer cells and the association between the application of genistein and KCNK9 expression level.

METHODS

The Cancer Genome Atlas (TCGA) database was used to study the correlation between the KCNK9 expression level and the prognosis of colon cancer patients. HT29 and SW480 colon cancer cell lines were cultured to examine the inhibitory effects of KCNK9 and genistein on colon cancer in vitro, and a mouse model of colon cancer with liver metastasis was established to verify the inhibitory effect of genistein in vivo.

RESULTS

KCNK9 was overexpressed in colon cancer cells and was associated with a shorter Overall Survival (OS), a shorter Disease-Specific Survival (DFS), and a shorter Progression-Free Interval (PFI) of colon cancer patients. In vitro experiments showed that downregulation of KCNK9 or genistein application could suppress cell proliferation, migration, and invasion abilities, induce cell cycle quiescence, promote cell apoptosis, and reduce epithelial-mesenchymal transition of the colon cancer cell line. In vivo experiments revealed that silencing of KCNK9 or application of genistein could inhibit hepatic metastasis from colon cancer. Additionally, genistein could inhibit KCNK9 expression, thereby attenuating Wnt/β-catenin signaling pathway.

CONCLUSION

Genistein inhibited the occurrence and progression of colon cancer through Wnt/β-catenin signaling pathway that could be mediated by KCNK9.

Advances in the Understanding of Two-Pore Domain TASK Potassium Channels and Their Potential as Therapeutic Targets

TWIK-related acid-sensitive K⁺ (TASK) channels, including TASK-1, TASK-3, and TASK-5, are important members of the two-pore domain potassium (K_2P) channel family. TASK-5 is not functionally expressed in the recombinant system. TASK channels are very sensitive to changes in extracellular pH and are active during all membrane potential periods. They are similar to other K_2P channels in that they can create and use background-leaked potassium currents to stabilize resting membrane conductance and repolarize the action potential of excitable cells. TASK channels are expressed in both the nervous system and peripheral tissues, including excitable and non-excitable cells, and are widely engaged in pathophysiological phenomena, such as respiratory stimulation, pulmonary hypertension, arrhythmia, aldosterone secretion, cancers, anesthesia, neurological disorders, glucose homeostasis, and visual sensitivity. Therefore, they are important targets for innovative drug development. In this review, we emphasized the recent advances in our understanding of the biophysical properties, gating profiles, and biological roles of TASK channels. Given the different localization ranges and biologically relevant functions of TASK-1 and TASK-3 channels, the development of compounds that selectively target TASK-1 and TASK-3 channels is also summarized based on data reported in the literature.

Potassium Channels as a Target for Cancer Therapy: Current Perspectives

Potassium (K⁺) channels are highly regulated membrane proteins that control the potassium ion flux and respond to different cellular stimuli. These ion channels are grouped into three major families, Kv (voltage-gated K⁺ channel), Kir (inwardly rectifying K⁺ channel) and K2P (two-pore K⁺ channels), according to the structure, to mediate the K⁺ currents. In cancer, alterations in K⁺ channel function can promote the acquisition of the so-called hallmarks of cancer – cell proliferation, resistance to apoptosis, metabolic changes, angiogenesis, and migratory capabilities – emerging as targets for the development of new therapeutic drugs. In this review, we focus our attention on the different K⁺ channels associated with the most relevant and prevalent cancer types. We summarize our knowledge about the potassium channels structure and function, their cancer dysregulated expression and discuss the K⁺ channels modulator and the strategies for designing new drugs.

Epigenomic Analysis Reveals the KCNK9 Potassium Channel as a Potential Therapeutic Target for Adenomyosis

Adenomyosis is linked to dysmenorrhea and infertility. The pathogenesis of adenomyosis remains unclear, and little is known of the genetic and epigenetic changes in the eutopic endometrium in adenomyosis, which may predispose patients to the invasion and migration of endometrial tissues into the myometrium. Transcriptome studies have identified genes related to various cell behaviors but no targets for therapeutic intervention. The epigenetics of the eutopic endometrium in adenomyosis have rarely been investigated. Endometrial tissue was obtained from premenopausal women with (n = 32) or without adenomyosis (n = 17) who underwent hysterectomy aged 34–57 years at a tertiary hospital. The methylome and transcriptome were assessed by using a Methylation 450 K BeadChip array and Affymetrix expression microarray. Protein expression was examined by immunohistochemistry. Differential methylation analysis revealed 53 lowly methylated genes and 176 highly methylated genes with consistent gene expression in adenomyosis, including three genes encoding potassium ion channels. High expression of KCNK9 in the eutopic and ectopic endometria in patients with adenomyosis but not in normal controls was observed. Hormone-free, antibody-based KCNK9 targeting is a potential therapeutic strategy for adenomyosis-related dysmenorrhea, menorrhagia, and infertility.

Integrative Analysis of KCNK Genes and Establishment of a Specific Prognostic Signature for Breast Cancer

Two-pore domains potassium channel subunits, encoded by KCNK genes, play vital roles in breast cancer progression. However, the characteristics of most KCNK genes in breast cancer has yet to be clarified. In this study, we comprehensively analyzed the expression, alteration, prognosis, and biological functions of various KCNKs in breast cancer. The expression of KCNK1/4/6/9/10/13 were significantly upregulated, while KCNK2/3/5/7/17 were downregulated in breast cancer tissues compared to normal mammary tissues. Increased expression of KCNK1/3/4/9 was correlated with poor overall survival, while high expression of KCNK2/7/17 predicted better overall survival in breast cancer. Eight KCNK genes were altered in breast cancer patients with a genomic mutation rate ranged from 1.9% to 21%. KCNK1 and KCNK9 were the two most common mutations in breast cancer, occurred in 21% and 18% patients, respectively. Alteration of KCNK genes was associated with the worse clinical characteristics and higher TMB, MSI, and hypoxia score. Using machine learning method, a specific prognostic signature with seven KCNK genes was established, which manifested accuracy in predicting the prognosis of breast cancer in both training and validation cohorts. A nomogram with great predictive performance was afterwards constructed through incorporating KCNK-based risk score with clinical features. Furthermore, KCNKs were correlated with the activation of several tumor microenvironment cells, including T cells, mast cells, macrophages, and platelets. Presentation of antigen, stimulation of G protein signaling and toll-like receptor cascaded were regulated by KCNKs family. Taken together, KCNKs may regulate breast cancer progression via modulating immune response which can serve as ideal prognostic biomarkers for breast cancer patients. Our study provides novel insight for future studies evaluating their usefulness as therapeutic targets.

Expression of Proton-Sensitive GPR31, GPR151, TASK1 and TASK3 in Common Skin Tumors

TWIK-related acid-sensitive potassium channels TASK1 and TASK3, as well as the G-protein-coupled receptors GPR31 and GPR151, are proton-sensitive membrane proteins. They can be activated or inhibited by low extracellular pH (pHe), which is a hallmark of the tumor microenvironment in solid tumors. However, the role of these channels in the development of skin tumors is still unclear. In this study, we investigated the expression profiles of TASK1, TASK3, GPR31 and GPR151 in squamous cell carcinomas (SCCs), basal cell carcinomas (BCCs), nevus cell nevi (NCN), and malignant melanomas (MMs). We performed immunohistochemistry using paraffin-embedded tissue samples from patients and found that most skin tumors express TASK1/3 and GPR31/151. The results show that BCCs are often negative for GPR31/151 as well as for TASK1/3, while nearly all SCCs express these markers. MMs and NCN show similar expression patterns. However, some tumors show a decreasing TASK1/3 expression in deeper dermal tumor tissue, while GPCRs were expressed more evenly. The lower frequency of GPR31/151 and TSAK1/3 expression in BCCs when compared to SCCs is a novel histological feature distinguishing these two entities. Moreover, BCCs also show lower expression of GPR31/151 and TASK1/3 as compared to NCN and MMs.

Epigenetic Dysregulation of KCNK9 Imprinting and Triple-Negative Breast Cancer

Genomic imprinting is an inherited form of parent-of-origin specific epigenetic gene regulation that is dysregulated by poor prenatal nutrition and environmental toxins. KCNK9 encodes for TASK3, a pH-regulated potassium channel membrane protein that is overexpressed in 40% of breast cancer. However, KCNK9 gene amplification accounts for increased expression in <10% of these breast cancers. Here, we showed that KCNK9 is imprinted in breast tissue and identified a differentially methylated region (DMR) controlling its imprint status. Hypomethylation at the DMR, coupled with biallelic expression of KCNK9, occurred in 63% of triple-negative breast cancers (TNBC). The association between hypomethylation and TNBC status was highly significant in African-Americans (p = 0.006), but not in Caucasians (p = 0.70). KCNK9 hypomethylation was also found in non-cancerous tissue from 77% of women at high-risk of developing breast cancer. Functional studies demonstrated that the KCNK9 gene product, TASK3, regulates mitochondrial membrane potential and apoptosis-sensitivity. In TNBC cells and non-cancerous mammary epithelial cells from high-risk women, hypomethylation of the KCNK9 DMR predicts for increased TASK3 expression and mitochondrial membrane potential (p < 0.001). This is the first identification of the KCNK9 DMR in mammary epithelial cells and demonstration that its hypomethylation in breast cancer is associated with increases in both mitochondrial membrane potential and apoptosis resistance. The high frequency of hypomethylation of the KCNK9 DMR in TNBC and non-cancerous breast tissue from high-risk women provides evidence that hypomethylation of the KNCK9 DMR/TASK3 overexpression may serve as a marker of risk and a target for prevention of TNBC, particularly in African American women.

Targeting ion channels for the treatment of lung cancer

Lung cancer is caused by several environmental and genetic variables and is globally associated with elevated morbidity and mortality. Among these variables, membrane-bound ion channels have a key role in regulating multiple signaling pathways in tumor cells and dysregulation of ion channel expression and function is closely related to proliferation, migration, and metastasis of lung cancer. This work reviews and summarizes current knowledge about the role of ion channels in lung cancer, focusing on the changes in the expression and function of various ion channels in lung cancer and how these changes affect lung cancer cell biology both in vitro and in vivo as evidenced by both genetic and pharmacological studies. It can help understand the molecular mechanisms of various ion channels influencing the initiation and progression of lung cancer and shed new insights into their roles in the development and treatment of this deadly disease.

Pharmacological Approaches to Studying Potassium Channels

In this review, we consider the pharmacology of potassium channels from the perspective of these channels as therapeutic targets. Firstly, we describe the three main families of potassium channels in humans and disease states where they are implicated. Secondly, we describe the existing therapeutic agents which act on potassium channels and outline why these channels represent an under-exploited therapeutic target with potential for future drug development. Thirdly, we consider the evidence desired in order to embark on a drug discovery programme targeting a particular potassium channel. We have chosen two "case studies": activators of the two-pore domain potassium (K_2P) channel TREK-2 (K_2P10.1), for the treatment of pain and inhibitors of the voltage-gated potassium channel K_V1.3, for use in autoimmune diseases such as multiple sclerosis. We describe the evidence base to suggest why these are viable therapeutic targets. Finally, we detail the main technical approaches available to characterise the pharmacology of potassium channels and identify novel regulatory compounds. We draw particular attention to the Comprehensive in vitro Proarrhythmia Assay initiative (CiPA, https://cipaproject.org ) project for cardiac safety, as an example of what might be both desirable and possible in the future, for ion channel regulator discovery projects.

Potassium Channel Protein KCNK6 Promotes Breast Cancer Cell Proliferation, Invasion, and Migration

Breast cancer is the most common malignant tumor in women, and its incidence is increasing each year. To effectively treat breast cancer, it is important to identify genes involved in its occurrence and development and to exploit them as potential drug therapy targets. Here, we found that potassium channel subfamily K member 6 (KCNK6) is significantly overexpressed in breast cancer, however, its function in tumors has not been reported. We further verified that KCNK6 expression is upregulated in breast cancer biopsies. Moreover, overexpressed KCNK6 was found to enhance the proliferation, invasion, and migration ability of breast cancer cells. These effects may occur by weakening cell adhesion and reducing cell hardness, thus affecting the malignant phenotype of breast cancer cells. Our study confirmed, for the first time, that increased KCNK6 expression in breast cancer cells may promote their proliferation, invasion, and migration. Moreover, considering that ion channels serve as therapeutic targets for many small molecular drugs in clinical treatment, targeting KCNK6 may represent a novel strategy for breast cancer therapies. Hence, the results of this study provide a theoretical basis for KCNK6 to become a potential molecular target for breast cancer treatment in the future.

Therapeutic Antibodies Targeting Potassium Ion Channels

Monoclonal antibodies combine specificity and high affinity binding with excellent pharmacokinetic properties and are rapidly being developed for a wide range of drug targets including clinically important potassium ion channels. Nonetheless, while therapeutic antibodies come with great promise, K⁺ channels represent particularly difficult targets for biologics development for a variety of reasons that include their dynamic structures and relatively small extracellular loops, their high degree of sequence conservation (leading to immune tolerance), and their generally low-level expression in vivo. The process is made all the more difficult when large numbers of antibody candidates must be screened for a given target, or when lead candidates fail to cross-react with orthologous channels in animal disease models due to their highly selective binding properties. While the number of antibodies targeting potassium channels in preclinical or clinical development is still modest, significant advances in the areas of protein expression and antibody screening are converging to open the field to an avalanche of new drugs. Here, the opportunities and constraints associated with the discovery of antibodies against K⁺ channels are discussed, with an emphasis on novel technologies that are opening the field to exciting new possibilities for biologics development.

Synthesis and cellular effects of a mitochondria-targeted inhibitor of the two-pore potassium channel TASK-3

The two-pore potassium channel TASK-3 has been shown to localize to both the plasma membrane and the mitochondrial inner membrane. TASK-3 is highly expressed in melanoma and breast cancer cells and has been proposed to promote tumor formation. Here we investigated whether pharmacological modulation of TASK-3, and specifically of mitochondrial TASK-3 (mitoTASK-3), had any effect on cancer cell survival and mitochondrial physiology. A novel, mitochondriotropic version of the specific TASK-3 inhibitor IN-THPP has been synthesized by addition of a positively charged triphenylphosphonium moiety. While IN-THPP was unable to induce apoptosis, mitoIN-THPP decreased survival of breast cancer cells and efficiently killed melanoma lines, which we show to express mitoTASK-3. Cell death was accompanied by mitochondrial membrane depolarization and fragmentation of the mitochondrial network, suggesting a role of the channel in the maintenance of the correct function of this organelle. In accordance, cells treated with mitoIN-THPP became rapidly depleted of mitochondrial ATP which resulted in activation of the AMP-dependent kinase AMPK. Importantly, cell survival was not affected in mouse embryonic fibroblasts and the effect of mitoIN-THPP was less pronounced in human melanoma cells stably knocked down for TASK-3 expression, indicating a certain degree of selectivity of the drug both for pathological cells and for the channel. In addition, mitoIN-THPP inhibited cancer cell migration to a higher extent than IN-THPP in two melanoma cell lines. In summary, our results point to the importance of mitoTASK-3 for melanoma cell survival and migration.

CG4928 Is Vital for Renal Function in Fruit Flies and Membrane Potential in Cells: A First In-Depth Characterization of the Putative Solute Carrier UNC93A

The number of transporter proteins that are not fully characterized is immense. Here, we used Drosophila melanogaster and human cell lines to perform a first in-depth characterization of CG4928, an ortholog to the human UNC93A, of which little is known. Solute carriers regulate and maintain biochemical pathways important for the body, and malfunctioning transport is associated with multiple diseases. Based on phylogenetic analysis, CG4928 is closely related to human UNC93A and has a secondary and a tertiary protein structure and folding similar to major facilitator superfamily transporters. Ubiquitous knockdown of CG4928 causes flies to have a reduced secretion rate from the Malpighian tubules; altering potassium content in the body and in the Malpighian tubules, homologous to the renal system; and results in the development of edema. The edema could be rescued by using amiloride, a common diuretic, and by maintaining the flies on ion-free diets. CG4928-overexpressing cells did not facilitate the transport of sugars and amino acids; however, proximity ligation assay revealed that CG4928 co-localized with TASK¹ channels. Overexpression of CG4928 resulted in induced apoptosis and cytotoxicity, which could be restored when cells were kept in high-sodium media. Furthermore, the basal membrane potential was observed to be disrupted. Taken together, the results indicate that CG4928 is of importance for generating the cellular membrane potential by an unknown manner. However, we speculate that it most likely acts as a regulator or transporter of potassium flows over the membrane.

Hereditary gingival fibromatosis associated with the missense mutation of the KCNK4 gene

Hereditary gingival fibromatosis (HGF) is a rare oral condition that may appear as an isolated entity or as part of a genetic disease or syndrome. Molecular and biochemical mechanisms that trigger this pathologic process are not completely understood. In this article, we present a rare case of hereditary gingival fibromatosis in conjunction with a syndromic phenotype, associated with a rare missense mutation of the KCNK4 gene. This mutation induces a change in the structure of the TRAAK channel belonging to the 2-pore potassium channels. The gain of function promoted by the mutation could represent the pathogenetic basis of gingival fibromatosis.

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.

Two-Pore Domain Potassium Channels as Drug Targets: Anesthesia and Beyond

Two-pore domain potassium (K2P) channels stabilize the resting membrane potential of both excitable and nonexcitable cells and, as such, are important regulators of cell activity. There are many conditions where pharmacological regulation of K2P channel activity would be of therapeutic benefit, including, but not limited to, atrial fibrillation, respiratory depression, pulmonary hypertension, neuropathic pain, migraine, depression, and some forms of cancer. Up until now, few if any selective pharmacological regulators of K2P channels have been available. However, recent publications of solved structures with small-molecule activators and inhibitors bound to TREK-1, TREK-2, and TASK-1 K2P channels have given insight into the pharmacophore requirements for compound binding to these sites. Together with the increasing availability of a number of novel, active, small-molecule compounds from K2P channel screening programs, these advances have opened up the possibility of rational activator and inhibitor design to selectively target K2P channels.

The correlation and role analysis of KCNK2/4/5/15 in Human Papillary Thyroid Carcinoma microenvironment

Background: KCNKs, potassium two pore domain channel family K members, can maintain the resting potential, regulate the amplitude and duration of the plateau of the action potential, and change the membrane potential and membrane excitability. Evidence from many studies indicates that KCNKs is abnormally expressed in many solid tumors and plays a regulatory role in the development and malignant progression of cancer. However, the expression pattern and prognostic value of KCNK factors in papillary thyroid carcinoma have not been reported.

Methods: In this study, we used the data from databases such as ONCOMINE, GEPIA, Kaplan-Meier Plotter, and cBioPortal to perform bioinformatics analysis of KCNK factors in patients with thyroid cancer.

Results: We found that the mRNA expression of KCNK1, KCNK5, KCNK6, KCNK7, and KCNK15 were significantly higher in thyroid cancer tissues than that in normal tissues, while KCNK2, KCNK4, KCNK9, KCNK16 and KCNK17 mRNA levels were decreased compared to normal tissues. And the expression levels of KCNK1/2/4/5/6/7/15 were correlated with the tumor stage. Survival analysis using the Kaplan-Meier Plotter database revealed that KCNK2/3/4/5/12/15 were associated with overall survival (OS) in patients with thyroid cancer.

Conclusion: Finally, the results of ROC curves, immunohistochemical staining, immune cell infiltration and kinase / miRNA / transcription factor regulation showed that KCNK2, KCNK4, KCNK5 and KCNK15 levels could be used as biomarkers for PTC diagnosis. This study implied that KCNK2, KCNK4, KCNK5 and KCNK15 are potential targets of precision therapy for patients with thyroid cancer and these genes are new biomarkers for the therapeutic target for thyroid cancer.

Withaferin A suppresses breast cancer cell proliferation by inhibition of the two-pore domain potassium (K2P9) channel TASK-3

Withaferin A (WFA), a C₅,C₆-epoxy steroidal lactone isolated from the medicinal plant Withania somnifera (L.) Dunal, inhibits growth of tumor cells in different cancer types. However, the mechanisms underlying the effect of WFA on tumor cells are not fully understood. In the present study, we evaluated the blockade of TASK-3 channels by WFA in TASK-3-expressing HEK-293 cells. Explore if the WFA-mediated TASK-3 blockade can be used as a pharmacological tool to decrease the cell viability in cancer cells. A combination of functional experiments (patch-clamp, gene downregulation, overexpression and pharmacological inhibition) and molecular docking analysis were used to get insights into the mechanism by which the inhibition of TASK-3 by WFA affects the growth and viability of cancer cells. Withaferin A was found to inhibit the activity of TASK-3 channels. The inhibitory effect of Withaferin A on TASK-3 potassium currents was dose-dependent and independent of voltage. Molecular modeling studies identified putative WFA-binding sites in TASK-3 channel involved the channel blockade. In agreements with the molecular modeling predictions, mutation of residues F125 to A (F125A), L197 to V (L197 V) and the double mutant F125A-L197 V markedly decreased the WFA-induced inhibition of TASK-3. Finally, the cytotoxic effect of WFA was tested in MDA-MB-231 human breast cancer cells transfected with TASK-3 or shRNA that decreases TASK-3 expression. Together, our results show that the cytotoxic effect of WFA on fully transformed MDA-MB-231 cells depends on the expression of TASK-3. Herein, we also provide insights into the mechanism of TASK-3 inhibition by WFA.

Contributions of natural products to ion channel pharmacology

Covering: Up to 2020Ion channels are a vast super-family of membrane proteins that play critical physiological roles in excitable and non-excitable cells. Their biomedical importance makes them valuable and attractive drug targets for neurological, cardiovascular, gastrointestinal and metabolic diseases, and for cancer therapy and immune modulation. Current therapeutics target only a minor subset of ion channels, leaving a large unexploited space within the ion channel field. Natural products harnessed from the almost unlimited and diverse universe of compounds within the bioenvironment have been used to modulate channels for decades. In this review we highlight the impact made by natural products on ion channel pharmacology, specifically on K⁺, Na_V and Ca_V channels, and use case studies to describe the development of ion channel-modulating drugs from natural sources for the treatment of pain, heart disease and autoimmune diseases.

Inhibition of RELM-β prevents hypoxia-induced overproliferation of human pulmonary artery smooth muscle cells by reversing PLC-mediated KCNK3 decline

AIMS

Although resistin-like molecule β (RELM-β) is involved in the pathological processes of various lung diseases, such as pulmonary inflammation, asthma and fibrosis, its potential roles in hypoxic pulmonary arterial hypertension (PAH) remain largely unknown. The study aims to investigate whether RELM-β contributes to hypoxia-induced excessive proliferation of human pulmonary artery smooth muscle cells (PASMCs) and to explore the potential mechanisms of this process.

MAIN METHODS

Human PASMCs were exposed to normoxia or hypoxia (1% O₂) for 24 h. siRNA targeting RELM-β was transfected into cells. Protein levels of KCNK3, RELM-β, pSTAT3 and STAT3 were determined by immunoblotting. The translocation of NFATc2 and expression of KCNK3 were visualized by immunofluorescence. 5-ethynyl-2'-deoxyuridine assays and cell counting kit-8 assays were performed to assess the proliferation of PASMCs.

KEY FINDINGS

(1) Chronic hypoxia significantly decreased KCNK3 protein levels while upregulating RELM-β protein levels in human PASMCs, which was accompanied by excessive proliferation of cells. (2) RELM-β could promote human PASMCs proliferation and activate the STAT3/NFAT axis by downregulating KCNK3 protein under normoxia. (3) Inhibition of RELM-β expression effectively prevented KCNK3-mediated cell proliferation under hypoxia. (4) Phospholipase C (PLC) inhibitor U-73122 could not only prevent the hypoxia/RELM-β-induced decrease in KCNK3 protein, but also inhibit the enhanced cell viability caused by hypoxia/RELM-β. (5) Both hypoxia and RELM-β could downregulate membrane KCNK3 protein levels by enhancing endocytosis.

SIGNIFICANCE

RELM-β activation is responsible for hypoxia-induced excessive proliferation of human PASMCs. Interfering with RELM-β may alleviate the progression of hypoxic PAH by upregulating PLC-dependent KCNK3 expression.

Production of TRPV2-targeting functional antibody ameliorating dilated cardiomyopathy and muscular dystrophy in animal models

Abnormal Ca²⁺ handling is essential in the pathophysiology of degenerative muscle disorders, such as dilated cardiomyopathy (DCM) and muscular dystrophy (MD). Transient receptor potential cation channel, subfamily V, member 2 (TRPV2) is a candidate for Ca²⁺ entry and a potential therapeutic target for degenerative muscle disorders, there are few specific inhibitors for TRPV2. In this study, we produced a monoclonal antibody (designated mAb88-2) and two polyclonal antibodies (pAb591 and pAb592) that selectively recognize TRPV2 from the outside of cells and interact with the turret region of the pore-forming outer gate. These antibodies inhibited Ca²⁺ influx via TRPV2 in cultured cells and substantially reduced TRPV2 in the plasma membrane via cellular internalization. We evaluated the therapeutic efficacy of the functional antibody in δ-sarcoglycan-deficient hamster (J2N-k) models of DCM and MD and in the 4C30 DCM model of murine heart failure. The intraperitoneal administration of the functional antibody (0.5 mg/kg) for 2 weeks (once a week) prevented the progression of cardiac dysfunction, as evaluated by echocardiography and histological staining, and improved the abnormal Ca²⁺ handling (high diastolic Ca²⁺ level and small Ca²⁺ transient peak) in cardiomyocytes isolated from J2N-k hamsters and prevented skeletal muscle damage. Further, the antibody effectively prevented heart failure in the 4C30 mouse model with end-stage DCM. Interestingly, endogenous TRPV2 that accumulated in the cardiac and skeletal muscle sarcolemma disappeared upon antibody administration. Thus, the newly produced antibodies are capable of ameliorating DCM and MD by promoting the cellular internalization of TRPV2; antibodies specific to human TRPV2 may substantially improve the treatment of patients with degenerative muscle diseases.

Ion Channels in Lung Cancer

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

TASK-3 Gene Knockdown Dampens Invasion and Migration and Promotes Apoptosis in KATO III and MKN-45 Human Gastric Adenocarcinoma Cell Lines

Incidence and mortality of gastric cancer is increasing worldwide, in part, because of the lack of new therapeutic targets to treat this disease. Different types of ion channels participate in the hallmarks of cancer. In this context, ion channels are known to exert control over the cell cycle, mechanisms that support survival, angiogenesis, migration, and cell invasion. In particular, TASK-3 (KCNK9), a member of the K2P potassium channel family, has attracted much interest because of its oncogenic properties. However, despite multiple lines of evidence linking TASK-3 to tumorigenesis in various types of cancer, its relationship with gastric cancer has not been fully examined. Therefore, we set out to assess the effect of TASK-3 gene knockdown on KATO III and MKN-45 human gastric adenocarcinoma cell lines by using a short hairpin RNA (shRNA)-mediated knockdown. Our results demonstrate that knocking down TASK-3 reduces cell proliferation and viability because of an increase in apoptosis without an apparent effect on cell cycle checkpoints. In addition, cell migration and invasion are reduced after knocking down TASK-3 in these cell lines. The present study highlights TASK-3 as a key protein involved in migration and cell survival in gastric cancer and corroborates its potential as a therapeutic target for gastric cancer treatment.

Antibodies Targeting KV Potassium Channels: A Promising Treatment for Cancer

Voltage-gated potassium channels are transmembrane proteins that allow flow of potassium across the membrane to regulate ion homeostasis, cell proliferation, migration, cell volume, and specific processes such as muscular contraction. Aberrant function or expression of potassium channels can underlie pathologies ranging from heart arrhythmia to cancer; the expression of potassium channels is altered in many types of cancer and that alteration correlates with malignancy and poor prognosis. Targeting potassium channels therefore constitutes a promising approach for cancer therapy. In this review, we discuss strategies to target a particular family of potassium channels, the voltage-gated potassium channels (K_V) where a reasonable structural understanding is available. We also discuss the possible obstacles and advantages of such a strategy.

Metabolic flexibility in melanoma: A potential therapeutic target

Cutaneous melanoma (CM) represents one of the most metastasizing and drug resistant solid tumors. CM is characterized by a remarkable metabolic plasticity and an important connection between oncogenic activation and energetic metabolism. In fact, melanoma cells can use both cytosolic and mitochondrial compartments to produce adenosine triphosphate (ATP) during cancer progression. However, the CM energetic demand mainly depends on glycolysis, whose upregulation is strictly linked to constitutive activation of BRAF/MAPK pathway affected by BRAF^V600E kinase mutant. Furthermore, the impressive metabolic plasticity of melanoma allows the development of resistance mechanisms to BRAF/MEK inhibitors (BRAFi/MEKi) and the adaptation to microenvironmental changes. The metabolic interaction between melanoma cells and tumor microenvironment affects the immune response and CM growth. In this review article, we describe the regulation of melanoma metabolic alterations and the metabolic interactions between cancer cells and microenvironment that influence melanoma progression and immune response. Finally, we summarize the hallmarks of melanoma therapies and we report BRAF/MEK pathway targeted therapy and mechanisms of metabolic resistance.

TASK Channels Pharmacology: New Challenges in Drug Design

Rational drug design targeting ion channels is an exciting and always evolving research field. New medicinal chemistry strategies are being implemented to explore the wild chemical space and unravel the molecular basis of the ion channels modulators binding mechanisms. TASK channels belong to the two-pore domain potassium channel family and are modulated by extracellular acidosis. They are extensively distributed along the cardiovascular and central nervous systems, and their expression is up- and downregulated in different cancer types, which makes them an attractive therapeutic target. However, TASK channels remain unexplored, and drugs designed to target these channels are poorly selective. Here, we review TASK channels properties and their known blockers and activators, considering the new challenges in ion channels drug design and focusing on the implementation of computational methodologies in the drug discovery process.

Case report: mutation analysis of primary pulmonary lymphoepithelioma-like carcinoma via whole-exome sequencing

Background

Primary pulmonary lymphoepithelioma-like carcinoma (LELC) is a rare tumor subtype accounting for around 0.9% of lung cancers. At present, research on LELC mainly focuses on pathological diagnosis, while the molecular mutation landscape is still unclear.

Case presentation

A 72-year-old female presented a productive cough for three weeks followed by severe symptoms for another week. Respiratory sounds were weak and coarser in the right lung field. F-FDG PET-CTA showed a hypermetabolic mass in the upper lobe of the right lung as well as the enlargement of right hilar and subcarinal lymph nodes. Hematoxylin-eosin staining and immunohistochemistry staining of the biopsy established the diagnosis of primary pulmonary LELC. After thoracoscopic-assisted radical resection of right lung cancer and middle lobe of right lung, the patient’s vital signs were stable without apparent productive cough, chest pain, chest tightness and other subjective discomforts. Furtherwhole exome sequencing of the patient’s tumor tissue and leukocytes (served as a germline mutation control) revealed 613 somatic gene mutations, and of which mutations in PRIM2, KCNB1, CDH1, and ATRX were most likely related to the LELC pathogenesis. The recurrence of gene mutations from various cancers database and a tumor mutation burden (TMB) of 18.7 mutations/mb were revealed as well.

Conclusion

Our findings have illustrated the genomic profile of a primary pulmonary LELC case and provided a positive biomarker that immune checkpoint blockade is potentially effective for this patient in further treatment.

Therapeutic Monoclonal Antibodies to Complex Membrane Protein Targets: Antigen Generation and Antibody Discovery Strategies

Cell surface membrane proteins comprise a wide array of structurally and functionally diverse proteins involved in a variety of important physiological and homeostatic processes. Complex integral membrane proteins, which are embedded in the lipid bilayer by multiple transmembrane-spanning helices, are represented by families of proteins that are important target classes for drug discovery. Such protein families include G-protein-coupled receptors, ion channels and transporters. Although these targets have typically been the domain of small-molecule drugs, the exquisite specificity of monoclonal antibodies offers a significant opportunity to selectively modulate these target proteins. Nevertheless, the isolation of antibodies with desired pharmacological functions has proved difficult because of technical challenges in preparing membrane protein antigens for antibody drug discovery. In this review, we describe recent progress in defining strategies for the generation of membrane protein antigens. We also describe antibody-isolation strategies that identify antibodies that bind the membrane protein and modulate protein function.

Antibodies and venom peptides: new modalities for ion channels

Ion channels play fundamental roles in both excitable and non-excitable tissues and therefore constitute attractive drug targets for myriad neurological, cardiovascular and metabolic diseases as well as for cancer and immunomodulation. However, achieving selectivity for specific ion channel subtypes with small-molecule drugs has been challenging, and there currently is a growing trend to target ion channels with biologics. One approach is to improve the pharmacokinetics of existing or novel venom-derived peptides. In parallel, after initial studies with polyclonal antibodies demonstrated the technical feasibility of inhibiting channel function with antibodies, multiple preclinical programmes are now using the full spectrum of available technologies to generate conventional monoclonal and engineered antibodies or nanobodies against extracellular loops of ion channels. After a summary of the current state of ion channel drug discovery, this Review discusses recent developments using the purinergic receptor channel P2X purinoceptor 7 (P2X7), the voltage-gated potassium channel KV1.3 and the voltage-gated sodium channel NaV1.7 as examples of targeting ion channels with biologics.

Integration of whole-genome sequencing and functional screening identifies a prognostic signature for lung metastasis in triple-negative breast cancer

Lung metastasis is one of the leading causes of death for triple-negative breast cancer (TNBC). We sought to characterize the genetic alterations underlying TNBC lung metastases by integrating whole-genome sequencing and functional screening. Furthermore, we aimed to develop a metastasis-related gene signature for TNBC patients to improve risk stratification. In this prospective observational study, we first conducted whole-genome sequencing of paired primary tumor and lung metastasis from one TNBC patient to identify potential genetic driver alterations. An in vivo gain-of-function screening using an amplified open reading frame library was then employed to screen candidate genes promoting lung metastasis. Finally, we applied Cox proportional hazard regression modeling to develop a prognostic gene signature from 14 candidate genes in TNBC. Compared to the primary tumor, copy number amplifications of chromosomes 3q and 8q were identified in the lung metastasis. We discovered an enrichment of 14 genes from chromosomes 3q and 8q in mouse lung metastases model. We further developed and validated a four-gene signature (ENY2, KCNK9, TNFRSF11B and KCNMB2) that predicts recurrence-free survival and lung metastasis in TNBC. Our data also demonstrated that upregulated expression of ENY2 could promote invasion and lung metastasis of TNBC cells both in vitro and in vivo. In conclusion, our study reveals functional genes with copy number amplifications among chromosome 3q and 8q in lung metastasis of TNBC. And we develop a functional gene signature that can effectively stratify patients into low- and high-risk subgroups of recurrence, helping frame personalized treatments for TNBC.

Pore-forming spider venom peptides show cytotoxicity to hyperpolarized cancer cells expressing K+ channels: A lentiviral vector approach

Recent studies demonstrated the upregulation of K⁺ channels in cancer cells. We have previously found that a pore-forming peptide LaFr26, purified from the venom of the Lachesana sp spider, was selectively incorporated into K⁺ channel expressing hyperpolarized cells. Therefore, it is expected that this peptide would have selective cytotoxicity to hyperpolarized cancer cells. Here we have tested whether LaFr26 and its related peptide, oxyopinin-2b, are selectively cytotoxic to K⁺ channel expressing cancer cells. These peptides were cytotoxic to the cells, of which resting membrane potential was hyperpolarized. The vulnerabilities of K⁺ channel-expressing cell lines correlated with their resting membrane potential. They were cytotoxic to lung cancer cell lines LX22 and BEN, which endogenously expressed K⁺ current. Contrastingly, these peptides were ineffective to glioblastoma cell lines, U87 and T98G, of which membrane potentials were depolarized. Peptides have a drawback, i.e. poor drug-delivery, that hinders their potential use as medicine. To overcome this drawback, we prepared lentiviral vectors that can express these pore-forming peptides and tested the cytotoxicity to K⁺ channel expressing cells. The transduction with these lentiviral vectors showed autotoxic activity to the channel expressing cells. Our study provides the basis for a new oncolytic viral therapy.

Identifying Disease-Gene Associations With Graph-Regularized Manifold Learning

Complex diseases are known to be associated with disease genes. Uncovering disease-gene associations is critical for diagnosis, treatment, and prevention of diseases. Computational algorithms which effectively predict candidate disease-gene associations prior to experimental proof can greatly reduce the associated cost and time. Most existing methods are disease-specific which can only predict genes associated with a specific disease at a time. Similarities among diseases are not used during the prediction. Meanwhile, most methods predict new disease genes based on known associations, making them unable to predict disease genes for diseases without known associated genes.In this study, a manifold learning-based method is proposed for predicting disease-gene associations by assuming that the geodesic distance between any disease and its associated genes should be shorter than that of other non-associated disease-gene pairs. The model maps the diseases and genes into a lower dimensional manifold based on the known disease-gene associations, disease similarity and gene similarity to predict new associations in terms of the geodesic distance between disease-gene pairs. In the 3-fold cross-validation experiments, our method achieves scores of 0.882 and 0.854 in terms of the area under of the receiver operating characteristic (ROC) curve (AUC) for diseases with more than one known associated genes and diseases with only one known associated gene, respectively. Further de novo studies on Lung Cancer and Bladder Cancer also show that our model is capable of identifying new disease-gene associations.

Development of a Novel Cell-Based Assay System for High-Throughput Screening of Compounds Acting on Background Two-Pore Domain K+ Channels

Two-pore domain K⁺ (K_2P) channels are thought to be druggable targets. However, only a few agents specific for K_2P channels have been identified, presumably due to the lack of an efficient screening system. To develop a new high-throughput screening (HTS) system targeting these channels, we have established a HEK293-based "test cell" expressing a mutated Na⁺ channel (Nav1.5) with markedly slowed inactivation, as well as a K⁺ channel (Kir2.1) that sets the membrane potential quite negative, close to K⁺ equilibrium potential. We found in this system that Kir2.1 block by 100 μM Ba²⁺ application consistently elicited a large depolarization like a long-lasting action potential. This maneuver resulted in cell death, presumably due to the sustained Na⁺ influx. When either the TWIK-related acid-sensitive K⁺ (TASK)-1 or TASK-3 channel was expressed in the test cells, Ba²⁺-induced cell death was markedly weakened. Stronger activation of TASK-1 by extracellular acidification further decreased the cell death. In contrast, the presence of K_2P channel blockers enhanced cell death. IC₅₀ values for TASK-1 and/or TASK-3 blockers acquired by measurements of relative cell viability were comparable to those obtained using patch-clamp recordings. Both blockers and openers of K_2P channels can be accurately assessed with high efficiency and throughput by this novel HTS system.

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.

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.

A Revised View on the Role of Surface AMPAR Mobility in Tuning Synaptic Transmission: Limitations, Tools, and Alternative Views

Calcium dynamics in presynaptic terminals regulate the response dynamics of most central excitatory synapses. However, this dogma has been challenged by the hypothesis that mobility of the postsynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid subtype glutamate receptors (AMPAR) plays a role in tuning fast excitatory synaptic transmission. In this review, we reevaluate the factors regulating postsynaptic AMPAR mobility, reassess the modeling parameters, analyze the experimental tools, and end by providing alternative ideas stemming from recent results. In particular, newer methods of labeling AMPARs with small fluorophores in live neurons, combined with super-resolution microscopy and sub-second dynamics, lends support to the idea that AMPARs are primarily within the synapse, are greatly constrained, and have much slower mobility than previously thought. We discuss new experiments which may be necessary to readdress the role of postsynaptic AMPAR mobility in tuning fast excitatory synaptic transmission.

TASK-3 Downregulation Triggers Cellular Senescence and Growth Inhibition in Breast Cancer Cell Lines

TASK-3 potassium channels are believed to promote proliferation and survival of cancer cells, in part, by augmenting their resistance to both hypoxia and serum deprivation. While overexpression of TASK-3 is frequently observed in cancers, the understanding of its role and regulation during tumorigenesis remains incomplete. Here, we evaluated the effect of reducing the expression of TASK-3 in MDA-MB-231 and MCF-10F human mammary epithelial cell lines through small hairpin RNA (shRNA)-mediated knockdown. Our results show that knocking down TASK-3 in fully transformed MDA-MB-231 cells reduces proliferation, which was accompanied by an induction of cellular senescence and cell cycle arrest, with an upregulation of cyclin-dependent kinase (CDK) inhibitors p21 and p27. In non-tumorigenic MCF-10F cells, however, TASK-3 downregulation did not lead to senescence induction, although cell proliferation was impaired and an upregulation of CDK inhibitors was also evident. Our observations implicate TASK-3 as a critical factor in cell cycle progression and corroborate its potential as a therapeutic target in breast cancer treatment.

TRPM5 mediates acidic extracellular pH signaling and TRPM5 inhibition reduces spontaneous metastasis in mouse B16-BL6 melanoma cells

Extracellular acidity is a hallmark of solid tumors and is associated with metastasis in the tumor microenvironment. Acidic extracellular pH (pH e ) has been found to increase intracellular Ca2+ and matrix metalloproteinase-9 (MMP-9) expression by activating NF-κB in the mouse B16 melanoma model. The present study assessed whether TRPM5, an intracellular Ca2+-dependent monovalent cation channel, is associated with acidic pH e signaling and induction of MMP-9 expression in this mouse melanoma model. Treatment of B16 cells with Trpm5 siRNA reduced acidic pH e -induced MMP-9 expression. Enforced expression of Trpm5 increased the rate of acidic pH e -induced MMP-9 expression, as well as increasing experimental lung metastasis. This genetic manipulation did not alter the pH e critical for MMP-9 induction but simply amplified the percentage of inducible MMP-9 at each pH e . Treatment of tumor bearing mice with triphenylphosphine oxide (TPPO), an inhibitor of TRPM5, significantly reduced spontaneous lung metastasis. In silico analysis of clinical samples showed that high TRPM5 mRNA expression correlated with poor overall survival rate in patients with melanoma and gastric cancer but not in patients with cancers of the ovary, lung, breast, and rectum. These results showed that TRPM5 amplifies acidic pH e signaling and may be a promising target for preventing metastasis of some types of tumor.