Targeting ion transport in cancer

TRP Channels in Cancer: Signaling Mechanisms and Translational Approaches

Ion channels play a crucial role in a wide range of biological processes, including cell cycle regulation and cancer progression. In particular, the transient receptor potential (TRP) family of channels has emerged as a promising therapeutic target due to its involvement in several stages of cancer development and dissemination. TRP channels are expressed in a large variety of cells and tissues, and by increasing cation intracellular concentration, they monitor mechanical, thermal, and chemical stimuli under physiological and pathological conditions. Some members of the TRP superfamily, namely vanilloid (TRPV), canonical (TRPC), melastatin (TRPM), and ankyrin (TRPA), have been investigated in different types of cancer, including breast, prostate, lung, and colorectal cancer. TRP channels are involved in processes such as cell proliferation, migration, invasion, angiogenesis, and drug resistance, all related to cancer progression. Some TRP channels have been mechanistically associated with the signaling of cancer pain. Understanding the cellular and molecular mechanisms by which TRP channels influence cancer provides new opportunities for the development of targeted therapeutic strategies. Selective inhibitors of TRP channels are under initial scrutiny in experimental animals as potential anti-cancer agents. In-depth knowledge of these channels and their regulatory mechanisms may lead to new therapeutic strategies for cancer treatment, providing new perspectives for the development of effective targeted therapies.

Gene expression profiling after exposure to a chemical carcinogen, Pentabrominated Diphenyl Ether, at different life stages

Exposure to environmental hazards occurs at different stages of our lifetime-infant, child, adult. This study integrates recently published toxicogenomics data to examine how exposure to a known rat chemical carcinogen (pentabrominated diphenyl ether (PBDE)) upregulated liver transcriptomic changes at different life cycle stages (PND 4, PND 22, adult). We found that at all three life cycle stages PBDE exposure induced hepatocellular transcriptomic changes in disease pathways including cancer, metabolic, membrane function, and Nrf2 antioxidant pathways, pathways all characteristics of chemical carcinogens. In addition, in the adult rat after a 5-day exposure to the chemical carcinogen, there was upregulation of members of the Ras oncogenic pathway, a specific pathway found to be activated in the PBDE-induced tumors in rats in a previous hazard identification cancer study. The findings of liver transcript changes characteristic of carcinogenic activity after early life exposures and after short-term adult exposures provides data to support the use of transcriptomic data to predict the apical cancer endpoints in model studies. Using data from gene expression profiling studies after neonatal, young, or adult short-term chemical exposure helps to meet the 21st century toxicology goal of developing study designs to reduce, refine, and replace the use of traditional 2-year rodent cancer studies to provide hazard identification information. The studies reported here find that key transcripts associated with carcinogenesis were elevated in neonate (PND 4), young (PND 22) and adult animals after short-term exposure to PBDE, a known experimental chemical carcinogen in model systems.

miRCoop: Identifying Cooperating miRNAs via Kernel Based Interaction Tests

Although miRNAs can cause widespread changes in expression programs, single miRNAs typically induce mild repression on their targets. Cooperativity among miRNAs is reported as one strategy to overcome this constraint. Expanding the catalog of synergistic miRNAs is critical for understanding gene regulation and for developing miRNA-based therapeutics. In this study, we develop miRCoop to identify synergistic miRNA pairs that have weak or no repression on the target mRNA individually, but when act together, induce strong repression. miRCoop uses kernel-based statistical interaction tests, together with miRNA and mRNA target information. We apply our approach to patient data of two different cancer types. In kidney cancer, we identify 66 putative triplets. For 64 of these triplets, there is at least one common transcription factor that potentially regulates all participating RNAs of the triplet, supporting a functional association among them. Furthermore, we find that identified triplets are enriched for certain biological processes that are relevant to kidney cancer. Some of the synergistic miRNAs are very closely encoded in the genome, hinting a functional association among them. In applying the method on tumor data with the primary liver site, we find 3105 potential triplet interactions. We believe miRCoop can aid our understanding of the complex regulatory interactions in different health and disease states of the cell and can help in designing miRNA-based therapies. Matlab code for the methodology is provided in https://github.com/guldenolgun/miRCoop.

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.

OEsophageal Ion Transport Mechanisms and Significance Under Pathological Conditions

Ion transporters play an important role in several physiological functions, such as cell volume regulation, pH homeostasis and secretion. In the oesophagus, ion transport proteins are part of the epithelial resistance, a mechanism which protects the oesophagus against reflux-induced damage. A change in the function or expression of ion transporters has significance in the development or neoplastic progression of Barrett’s oesophagus (BO). In this review, we discuss the physiological and pathophysiological roles of ion transporters in the oesophagus, highlighting transport proteins which serve as therapeutic targets or prognostic markers in eosinophilic oesophagitis, BO and esophageal cancer. We believe that this review highlights important relationships which might contribute to a better understanding of the pathomechanisms of esophageal diseases.

New Perspectives in the Treatment of Tumor Cells by Electromagnetic Radiation at Resonance Frequencies in Cellular Membrane Channels

Background:

The use of electromagnetic fields has been considered as adjuvant therapy for the treatment of cancer given that some clinical trials have shown that the irradiation of cancer cells with electromagnetic fields can slow down the disease progression.

Aims:

We hypothesize that this effect could be amplified by irradiating tumor cells with electromagnetic fields having frequencies close to the natural resonant frequencies of membrane channels in tumor cells, in order to obtain a significant change of the ion flux across tumor cell membrane channels, inducing the largest harmful alteration in their cellular function.

Methods:

Neuronal-like cells were used as a cell model and exposed for 6 h to electromagnetic fields at different frequencies (0, 50 Hz, 900 MHz) at the same intensity of 2 mT. The exposure system was represented by two Helmholtz coils driven by a power amplifier in current mode and an arbitrary function generator. FTIR spectroscopy was used to evaluate the results of the exposure.

Results:

The results of this study showed that the Amide I vibration band increased in intensity with the increase of the frequency, leading us to assume that the displacement of the cell channels α-helices depends on the frequency of the applied electromagnetic fields.

Conclusion:

This preliminary result leads us to plan future research aimed at searching for the natural frequencies of membrane channels in tumor cells using resonant electromagnetic fields in order to damage the cellular functions of tumor cells. Clinical trials are needed to confirm such a hypothesis derived from this physical study.

Overexpression of Transcobalamin 1 is an Independent Negative Prognosticator in Rectal Cancers Receiving Concurrent Chemoradiotherapy

Objective: Neoadjuvant concurrent chemoradiotherapy (CCRT) is an increasingly common therapeutic strategy for locally advanced rectal cancer, but stratification of risk and final outcomes remain a major challenge. Transcobalamin 1 (TCN1), a vitamin B12 (cobalamin)-binding protein, regulates cobalamin homeostasis. High expression of TCN1 have been reported in neoplasms such as breast cancer and hepatocellular carcinoma. However, little is known about the relevance of TCN1 to rectal cancer receiving CCRT. This study examined the predictive and prognostic impact of TCN1 expression in patients with rectal cancer following neoadjuvant CCRT. Methods: Through data mining from a published transcriptome of rectal cancers (GSE35452), we identified upregulation of TCN1 gene as the most significantly predicted poor response to CCRT among ion transport-related genes (GO:0006811). We evaluated TCN1 immunohistochemistry and performed an H-score analysis on endoscopic biopsy specimens from 172 rectal cancer patients receiving neoadjuvant CCRT followed by curative surgery. Expression levels of TCN1 were further correlated with clinicopathologic features, therapeutic response, tumor regression grade (TRG) and survivals including metastasis-free survival (MeFS), disease-specific survival (DSS) and recurrent-free survival (LRFS). Results: TCN1 overexpression was significantly related to advanced post-treatment tumor (T3, T4; p<0.001) and nodal status (N1, N2; p<0.001), vascular invasion (p=0.003) and inferior tumor regression grade (p < 0.001). In survival analyses, TCN1 overexpression was significantly associated with shorter DSS (p<0.0001), MeFS (p=0.0002) and LRFS (p=0.0001). Furthermore, it remained an independent prognosticator of worse DSS (p=0.002, hazard ratio=3.344), MeFS (p=0.021, hazard ratio=3.015) and LRFS (p=0.037, hazard ratio=3.037) in the multivariate comparison. Conclusion: Overexpression of TCN1 is associated with poor therapeutic response and adverse outcomes in rectal cancer patients receiving CCRT, justifying the potential prognostic value of TCN1 in rectal cancer receiving CCRT.

Cellular acidification as a new approach to cancer treatment and to the understanding and therapeutics of neurodegenerative diseases

During the last few years, the understanding of the dysregulated hydrogen ion dynamics and reversed proton gradient of cancer cells has resulted in a new and integral pH-centric paradigm in oncology, a translational model embracing from cancer etiopathogenesis to treatment. The abnormalities of intracellular alkalinization along with extracellular acidification of all types of solid tumors and leukemic cells have never been described in any other disease and now appear to be a specific hallmark of malignancy. As a consequence of this intracellular acid-base homeostatic failure, the attempt to induce cellular acidification using proton transport inhibitors and other intracellular acidifiers of different origins is becoming a new therapeutic concept and selective target of cancer treatment, both as a metabolic mediator of apoptosis and in the overcoming of multiple drug resistance (MDR). Importantly, there is increasing data showing that different ion channels contribute to mediate significant aspects of cancer pH regulation and etiopathogenesis. Finally, we discuss the extension of this new pH-centric oncological paradigm into the opposite metabolic and homeostatic acid-base situation found in human neurodegenerative diseases (HNDDs), which opens novel concepts in the prevention and treatment of HNDDs through the utilization of a cohort of neural and non-neural derived hormones and human growth factors.

Triple-edged therapy targeting intracellular alkalosis and extracellular acidosis in cancer

Extracellular acidity and intracellular alkalinity are two of the characteristics hallmarks of malignant cells and their environment. This involves an inversion of the extracellular/intracellular pH gradient when compared with normal cells and it gives malignant cells proliferative and invasive advantages. Thus, the reversal of the pH gradient is a legitimate objective in the treatment of cancer and may be accomplished with drugs already used for other purposes and/or with specific new drugs that are currently being studied. The aim of this review is to describe a triple approach for reversing this gradient inversion using the concerted utilization of proton extrusion inhibitors, mitochondrial poisons and lysosomal poisons that should act synergistically through different mechanisms. The scheme presented here is compatible with almost all the chemotherapeutic protocols currently being used.

Cancer: fundamentals behind pH targeting and the double-edged approach

The highly regulated pH of cells and the less-regulated pH of the surrounding extracellular matrix (ECM) is the result of a delicate balance between metabolic processes and proton production, proton transportation, chemical buffering, and vascular removal of waste products. Malignant cells show a pronounced increase in metabolic processes where the 10- to 15-fold rise in glucose consumption is only the tip of the iceberg. Aerobic glycolysis (Warburg effect) is one of the hallmarks of cancer metabolism that implies excessive production of protons, which if stayed inside the cells would result in fatal intracellular acidosis (maintaining a strict acid-base balance is essential for the survival of eukaryotic cells). Malignant cells solve this problem by increasing mechanisms of proton transportation which expel the excess acidity. This allows cancer cells to keep a normal intracellular pH, or even overshooting this mechanism permits a slightly alkaline intracellular tendency. The proton excess expelled from malignant cells accumulates in the ECM, where chronic hypoxia and relative lack of enough blood vessels impede adequate proton clearance, thus creating an acidic microenvironment. This microenvironment is quite heterogeneous due to the tumor's metabolic heterogeneity and variable degrees of hypoxia inside the tumor mass. The acidic environment (plus other necessary cellular modifications) stimulates migration and invasion and finally intravasation of malignant cells which eventually may result in metastasis. Targeting tumor pH may go in two directions: 1) increasing extracellular pH which should result in less migration, invasion, and metastasis; and 2) decreasing intracellular pH which may result in acidic stress and apoptosis. Both objectives seem achievable at the present state of the art with repurposed drugs. This hypothesis analyzes the altered pH of tumors and its implications for progression and metastasis and also possible repurposed drug combinations targeting this vulnerable side of cancer development. It also analyzes the double-edged approach, which consists in pharmacologically increasing intracellular proton production and simultaneously decreasing proton extrusion creating intracellular acidity, acid stress, and eventual apoptosis.

Involvement of ion channels and transporters in carcinoma angiogenesis and metastasis

Angiogenesis is a finely tuned process, which is the result of the equilibrium between pro- and antiangiogenic factors. In solid tumor angiogenesis, the balance is highly in favor of the production of new, but poorly functional blood vessels, initially intended to provide growing tumors with nutrients and oxygen. Among the numerous proteins involved in tumor development, several types of ion channels are overexpressed in tumor cells, as well as in stromal and endothelial cells. Ion channels thus actively participate in the different hallmarks of cancer, especially in tumor angiogenesis and metastasis. Indeed, from their strategic localization in the plasma membrane, ion channels are key operators of cell signaling, as they sense and respond to environmental changes. This review aims to decipher how ion channels of different families are intricately involved in the fundamental angiogenesis and metastasis hallmarks, which lead from a nascent tumor to systemic dissemination. An overview of the possible use of ion channels as therapeutic targets will also be given, showing that ion channel inhibitors or specific antibodies may provide effective tools, in the near future, in the treatment of carcinomas.

Carbonic anhydrase IX inhibition is an effective strategy for osteosarcoma treatment

OBJECTIVE

Hypoxia-inducible factor 1, a regulator of CA IX activity, is often overexpressed in human osteosarcoma (OS) but not in normal tissues, and its expression levels correlate with prognosis. In this study, we investigated the therapeutic potential of newly synthesized CA IX sulfonamide inhibitors in OS.

METHODS

CA IX expression was evaluated in OS cell lines and bone marrow stromal cells (BMSC). After treatment with CA IX inhibitors, cell proliferation, apoptosis, cell cycle, extracellular and cytosolic pH changes were evaluated both in vitro and in mouse OS xenografts.

RESULTS

CA IX expression levels were significantly higher in OS than in BMSC. Accordingly, CA IX inhibitor 3 induced remarkable cytotoxicity on OS cells without affecting BMSC proliferation. This activity was increased under hypoxia, and was mediated by cell cycle arrest and by the modulation of cytosolic and extracellular pH. In vivo, CA IX inhibitor 3 reduced tumor growth by inducing significant necrosis.

CONCLUSIONS

Our results provide a strong rationale for the clinical use of the newly synthesized CA IX inhibitor 3 in human OS.

Does aberrant membrane transport contribute to poor outcome in adult acute myeloid leukemia?

Acute myeloid leukemia in adults is a highly heterogeneous disease. Gene expression profiling performed using unsupervised algorithms can be used to distinguish specific groups of patients within a large patient cohort. The identified gene expression signatures can offer insights into underlying physiological mechanisms of disease pathogenesis. Here, the analysis of several related gene expression clusters associated with poor outcome, worst overall survival and highest rates of resistant disease and obtained from the patients at the time of diagnosis or from previously untreated individuals is presented. Surprisingly, these gene clusters appear to be enriched for genes corresponding to proteins involved in transport across membranes (transporters, carriers and channels). Several ideas describing the possible relationship of membrane transport activity and leukemic cell biology, including the "Warburg effect," the specific role of chloride ion transport, direct "import" of metabolic energy through uptake of creatine phosphate, and modification of the bone marrow niche microenvironment are discussed.

EpilepsyGene: a genetic resource for genes and mutations related to epilepsy

Epilepsy is one of the most prevalent chronic neurological disorders, afflicting about 3.5–6.5 per 1000 children and 10.8 per 1000 elderly people. With intensive effort made during the last two decades, numerous genes and mutations have been published to be associated with the disease. An organized resource integrating and annotating the ever-increasing genetic data will be imperative to acquire a global view of the cutting-edge in epilepsy research. Herein, we developed EpilepsyGene (http://61.152.91.49/EpilepsyGene). It contains cumulative to date 499 genes and 3931 variants associated with 331 clinical phenotypes collected from 818 publications. Furthermore, in-depth data mining was performed to gain insights into the understanding of the data, including functional annotation, gene prioritization, functional analysis of prioritized genes and overlap analysis focusing on the comorbidity. An intuitive web interface to search and browse the diversified genetic data was also developed to facilitate access to the data of interest. In general, EpilepsyGene is designed to be a central genetic database to provide the research community substantial convenience to uncover the genetic basis of epilepsy.

Ion channels in cancer: future perspectives and clinical potential

Ion transport across the cell membrane mediated by channels and carriers participate in the regulation of tumour cell survival, death and motility. Moreover, the altered regulation of channels and carriers is part of neoplastic transformation. Experimental modification of channel and transporter activity impacts tumour cell survival, proliferation, malignant progression, invasive behaviour or therapy resistance of tumour cells. A wide variety of distinct Ca(2+) permeable channels, K(+) channels, Na(+) channels and anion channels have been implicated in tumour growth and metastasis. Further experimental information is, however, needed to define the specific role of individual channel isoforms critically important for malignancy. Compelling experimental evidence supports the assumption that the pharmacological inhibition of ion channels or their regulators may be attractive targets to counteract tumour growth, prevent metastasis and overcome therapy resistance of tumour cells. This short review discusses the role of Ca(2+) permeable channels, K(+) channels, Na(+) channels and anion channels in tumour growth and metastasis and the therapeutic potential of respective inhibitors.