An inhibitor of K+ channels modulates human endometrial tumor-initiating cells

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

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

Potassium Channels in Cancer

Neoplastic transformation is reportedly associated with alterations of the potassium transport across plasma and intracellular membranes. These alterations have been identified as crucial elements of the tumourigenic reprogramming of cells. Potassium channels may contribute to cancer initiation, malignant progression and therapy resistance of tumour cells. The book chapter focusses on (oncogenic) potassium channels frequently upregulated in different tumour entities, upstream and downstream signalling of these channels, their contribution to the maintenance of cancer stemness and the formation of an immunosuppressive tumour microenvironment. In addition, their role in adaptation to tumour hypoxia, metabolic reprogramming, as well as tumour spreading and metastasis is discussed. Finally, we discuss how (oncogenic) potassium channels may confer treatment resistance of tumours against radiation and chemotherapy and thus might be harnessed for new therapy strategies, for instance, by repurposing approved drugs known to target potassium channels.

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

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

Intermediate-Conductance-Ca2-Activated K Channel IKCa1 Is Upregulated and Promotes Cell Proliferation in Cervical Cancer

BACKGROUND Accumulating data point to intermediate-conductance calcium-activated potassium channel (IKCa1) as a key player in controlling cell cycle progression and proliferation of human cancer cells. However, the role that IKCa1 plays in the growth of human cervical cancer cells is largely unexplored. MATERIAL AND METHODS In this study, Western blot analysis, immunohistochemical staining, and RT-PCR were first used for IKCa1protein and gene expression assays in cervical cancer tissues and HeLa cells. Then, IKCa1 channel blocker and siRNA were employed to inhibit the functionality of IKCa1 and downregulate gene expression in HeLa cells, respectively. After these treatments, we examined the level of cell proliferation by MTT method and measured IKCa1 currents by conventional whole-cell patch clamp technique. Cell apoptosis was assessed using the Annexin V-FITC/Propidium Iodide (PI) double-staining apoptosis detection kit. RESULTS We demonstrated that IKCa1 mRNA and protein are preferentially expressed in cervical cancer tissues and HeLa cells. We also showed that the IKCa1 channel blocker, clotrimazole, and IKCa1 channel siRNA can be used to suppress cervical cancer cell proliferation and decrease IKCa1 channel current. IKCa1 downregulation by specific siRNAs induced a significant increase in the proportion of apoptotic cells in HeLa cells. CONCLUSIONS IKCa1 is overexpressed in cervical cancer tissues, and IKCa1 upregulation in cervical cancer cell linea enhances cell proliferation, partly by reducing the proportion of apoptotic cells.

Tumor microenvironment promotes dicarboxylic acid carrier-mediated transport of succinate to fuel prostate cancer mitochondria

Prostate cancer cells reprogram their metabolism, so that they support their elevated oxidative phosphorylation and promote a cancer friendly microenvironment. This work aimed to explore the mechanisms that cancer cells employ for fueling themselves with energy rich metabolites available in interstitial fluids. The mitochondria oxidative phosphorylation in metastatic prostate cancer DU145 cells and normal prostate epithelial PrEC cells were studied by high-resolution respirometry. An important finding was that prostate cancer cells at acidic pH 6.8 are capable of consuming exogenous succinate, while physiological pH 7.4 was not favorable for this process. Using specific inhibitors, it was demonstrated that succinate is transported in cancer cells by the mechanism of plasma membrane Na(+)-dependent dycarboxylic acid transporter NaDC3 (SLC13A3 gene). Although the level of expression of SLC13A3 was not significantly altered when maintaining cells in the medium with lower pH, the respirometric activity of cells under acidic condition was elevated in the presence of succinate. In contrast, normal prostate cells while expressing NaDC3 mRNA do not produce NaDC3 protein. The mechanism of succinate influx via NaDC3 in metastatic prostate cancer cells could yield a novel target for anti-cancer therapy and has the potential to be used for imaging-based diagnostics to detect non-glycolytic tumors.

BKCa channel inhibitor modulates the tumorigenic ability of hormone-independent breast cancer cells via the Wnt pathway

In breast cancers, the large conductance Ca2+ and voltage sensitive K+ (BKCa) channels have been hypothesized to function as oncoproteins, yet it remains unclear how inhibition of channel activity impacts oncogenesis. We demonstrated herein that iberiotoxin (IbTX), an inhibitor of BKCa channels, differentially modulated the in vitro tumorigenic activities of hormone-independent breast cancer cells. Specifically, in HER-2/neu-overexpressing UACC893 cells and triple‑negative MDA-MB-231 cells, IbTX selectively attenuated anchorage-independent growth with concomitant downregulation of β-catenin as well as total and phosphorylated Akt and HER-2/neu. By contrast, HER-2/neu-overexpressing SK-BR-3 cells were insensitive to IbTX. Molecular analyses showed an absence of β-catenin and a dose-dependent upregulation of total and phosphorylated Akt and HER-2/neu in these cells. Taken together, these studies identify β-catenin as a putative modulator of the inhibitory actions of IbTX in sensitive breast cancer cells.

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

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