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

Plant-Derived Anti-Cancer Therapeutics and Biopharmaceuticals

In spite of significant advancements in diagnosis and treatment, cancer remains one of the major threats to human health due to its ability to cause disease with high morbidity and mortality. A multifactorial and multitargeted approach is required towards intervention of the multitude of signaling pathways associated with carcinogenesis inclusive of angiogenesis and metastasis. In this context, plants provide an immense source of phytotherapeutics that show great promise as anticancer drugs. There is increasing epidemiological data indicating that diets rich in vegetables and fruits could decrease the risks of certain cancers. Several studies have proved that natural plant polyphenols, such as flavonoids, lignans, phenolic acids, alkaloids, phenylpropanoids, isoprenoids, terpenes, and stilbenes, could be used in anticancer prophylaxis and therapeutics by recruitment of mechanisms inclusive of antioxidant and anti-inflammatory activities and modulation of several molecular events associated with carcinogenesis. The current review discusses the anticancer activities of principal phytochemicals with focus on signaling circuits towards targeted cancer prophylaxis and therapy. Also addressed are plant-derived anti-cancer vaccines, nanoparticles, monoclonal antibodies, and immunotherapies. This review article brings to light the importance of plants and plant-based platforms as invaluable, low-cost sources of anti-cancer molecules of particular applicability in resource-poor developing countries.

In silico screening and identifying phytoconstituents of Withania somnifera as potent inhibitors of BRCA1 mutants: A therapeutic against breast cancer

Breast CAncer gene 1 (BRCA1) is an anti-oncogene that helps the cell repair damaged DNA and preserve genetic material. BRCA1 also acts as a cell growth suppressor and produces tumor suppressor gene (TSG) proteins, i.e., BRCA1 protein. Remarkably, BRCA1 mutations account for 90 % of hereditary breast cancer and a majority of hereditary ovarian cancer. Hence, we have considered three mutants of BRCA1 (R1699W, R1699Q, T1700A) in this study and adopted an in-silico approach to find the best possible phytochemical to inhibit these mutated proteins, enabling early breast cancer diagnosis. Perceiving the importance, many natural molecules from ancient medicinal plants are considered for molecular docking. Our findings suggest that though many molecules bind actively with the receptor's active site, the top three phytoconstituents (27-Deoxy-14-hydroxywithaferin A, Withacoagulin, Somniferanolide) of Withania somnifera, commonly known as Ashwagandha, have high binding affinities and suitable pharmacokinetic properties, making these natural compounds potential drug candidates. Further, molecular dynamics (MD) simulation and the binding free energy calculation show stability and thermodynamically favourable. We can, therefore, draw the conclusion that these lead compounds act as potential inhibitors against BRCA1. However, wet lab experiments and clinical trials are recommended to ascertain its efficacy, hence the development of novel BRCA1 inhibitors.

Intermediate Filaments in Breast Cancer Progression, and Potential Biomarker for Cancer Therapy: A Narrative Review

Intermediate filaments are one of the three components of the cytoskeletons, along with actin and microtubules. The intermediate filaments consist of extensive variations of structurally related proteins with specific expression patterns in cell types. The expression pattern alteration of intermediate filaments is frequently correlated with cancer progression, specifically with the epithelial-to-mesenchymal transition process closely related to increasing cellular migration and invasion. This review will discuss the involvement of cytoplasmic intermediate filaments, specifically vimentin, nestin, and cytokeratin (CK5/CK6, CK7, CK8/CK18, CK17, CK19, CK20, CSK1), in breast cancer progression and as prognostic or diagnostic biomarkers. The potential for drug development targeting intermediate filaments in cancer will be reviewed.

An update on existing therapeutic options and status of novel anti-metastatic agents in breast cancer: Elucidating the molecular mechanisms underlying the pleiotropic action of Withania somnifera (Indian ginseng) in breast cancer attenuation

Major significant advancements in pharmacology and drug technology have been made to heighten the impact of cancer therapies, improving the life expectancy of subjects diagnosed with malignancy. Statistically, 99% of breast cancers occur in women while 0.5-1% occur in men, the female gender being the strongest breast cancer risk factor. Despite several breakthroughs, breast cancer continues to have a worldwide impact and is one of the leading causes of mortality. Additionally, resistance to therapy is a crucial factor enabling cancer cell persistence and resurgence. As a result, the search and discovery of novel modulatory agents and effective therapies capable of controlling tumor progression and cancer cell proliferation is critical. Withania somnifera (L.) Dunal (WS), commonly known as Indian ginseng, has long been used traditionally for the treatment of several ailments in the Indian context. Recently, WS and its phytoconstituents have shown promising anti-breast cancer properties and, as such, can be employed as prophylactic as well as therapeutic adjuncts to the main line of breast cancer treatment. The present review is an attempt to explore and provide experimental evidences in support of the prophylactic and therapeutic potential of WS in breast cancer, along with a deeper insight into the multiple molecular mechanisms and novel targets through which it acts against breast and other hormonally-induced cancers viz. ovarian, uterine and cervical. This exploration might prove crucial in providing better understanding of breast cancer progression and metastasis and its use as an adjunct in improving disease prognosis and therapeutic outcome.

Withanolides: Promising candidates for cancer therapy

Natural products have played a significant role throughout history in the prevention and treatment of numerous diseases, particularly cancers. As a natural product primarily derived from various medicinal plants in the Withania genus, withanolides have been shown in several studies to exhibit potential activities in cancer treatment. Consequently, understanding the molecular mechanism of withanolides could herald the discovery of new anticancer agents. Withanolides have been studied widely, especially in the last 20 years, and attracted the attention of numerous researchers. Currently, over 1200 withanolides have been classified, with approximately a quarter of them having been reported in the literature to be able to modulate the survival and death of cancer cells through multiple avenues. To what extent, though, has the anticancer effects of these compounds been studied? How far are they from being developed into clinical drugs? What are their potential, characteristic features, and challenges? In this review, we elaborate on the current knowledge of natural compounds belonging to this class and provide an overview of their natural sources, anticancer activity, mechanism of action, molecular targets, and implications for anticancer drug research. In addition, direct targets and clinical research to guide the design and implementation of future preclinical and clinical studies to accelerate the application of withanolides have been highlighted.

The Therapeutic Effects of Withaferin A against Cancer: Overview and Updates

Cancer is a rapidly rising health problem among the global population, and this burden causes a significant challenge for public health. Current chemotherapeutic agents have different limitations, including drug resistance and severe side effects, and it demands a robust approach to accessing promising anti-cancer therapeutics. The natural compounds have been extensively studied to identify improved therapeutic agents for cancer therapy. Withaferin A (WA) is a steroidal lactone found in Withania somnifera and possesses anti-inflammatory, antioxidant, anti-angiogenesis, and anticancer properties. Multiple studies have shown that WA treatment attenuated various cancer hallmarks by inducing apoptosis and reducing angiogenesis and metastasis with reduced side effects. WA is a promising agent for the treatment of various cancer, and it targets various signaling pathways. With recent updates, the current review highlights the therapeutic implications of WA and its molecular targets in different cancer.

Targeting Cell Signaling Pathways in Lung Cancer by Bioactive Phytocompounds

Lung cancer is a heterogeneous group of malignancies with high incidence worldwide. It is the most frequently occurring cancer in men and the second most common in women. Due to its frequent diagnosis and variable response to treatment, lung cancer was reported as the top cause of cancer-related deaths worldwide in 2020. Many aberrant signaling cascades are implicated in the pathogenesis of lung cancer, including those involved in apoptosis (B cell lymphoma protein, Bcl-2-associated X protein, first apoptosis signal ligand), growth inhibition (tumor suppressor protein or gene and serine/threonine kinase 11), and growth promotion (epidermal growth factor receptor/proto-oncogenes/phosphatidylinositol-3 kinase). Accordingly, these pathways and their signaling molecules have become promising targets for chemopreventive and chemotherapeutic agents. Recent research provides compelling evidence for the use of plant-based compounds, known collectively as phytochemicals, as anticancer agents. This review discusses major contributing signaling pathways involved in the pathophysiology of lung cancer, as well as currently available treatments and prospective drug candidates. The anticancer potential of naturally occurring bioactive compounds in the context of lung cancer is also discussed, with critical analysis of their mechanistic actions presented by preclinical and clinical studies.

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.

The Role οf Ion Channels in the Development and Progression of Prostate Cancer

Ion channels have major regulatory functions in living cells. Apart from their role in ion transport, they are responsible for cellular electrogenesis and excitability, and may also regulate tissue homeostasis. Although cancer is not officially classified as a channelopathy, it has been increasingly recognized that ion channel aberrations play an important role in virtually all cancer types. Ion channels can exert pro-tumorigenic activities due to genetic or epigenetic alterations, or as a response to molecular signals, such as growth factors, hormones, etc. Increasing evidence suggests that ion channels and pumps play a critical role in the regulation of prostate cancer cell proliferation, apoptosis evasion, migration, epithelial-to-mesenchymal transition, and angiogenesis. There is also evidence suggesting that ion channels might play a role in treatment failure in patients with prostate cancer. Hence, they represent promising targets for diagnosis, staging, and treatment, and their effects may be of particular significance for specific patient populations, including those undergoing anesthesia and surgery. In this article, the role of major types of ion channels involved in the development and progression of prostate cancer are reviewed. Identifying the underlying molecular mechanisms of the pro-tumorigenic effects of ion channels may potentially inform the development of novel therapeutic strategies to counter this malignancy.

The use of African medicinal plants in cancer management

Cancer is the third leading cause of premature death in sub-Saharan Africa. Cervical cancer has the highest number of incidences in sub-Saharan Africa due to high HIV prevalence (70% of global cases) in African countries which is linked to increasing the risk of developing cervical cancer, and the continuous high risk of being infected with Human papillomavirus In 2020, the risk of dying from cancer amongst women was higher in Eastern Africa (11%) than it was in Northern America (7.4%). Plants continue to provide unlimited pharmacological bioactive compounds that are used to manage various illnesses, including cancer. By reviewing the literature, we provide an inventory of African plants with reported anticancer activity and evidence supporting their use in cancer management. In this review, we report 23 plants that have been used for cancer management in Africa, where the anticancer extracts are usually prepared from barks, fruits, leaves, roots, and stems of these plants. Extensive information is reported about the bioactive compounds present in these plants as well as their potential activities against various forms of cancer. However, information on the anticancer properties of other African medicinal plants is insufficient. Therefore, there is a need to isolate and evaluate the anticancer potential of bioactive compounds from other African medicinal plants. Further studies on these plants will allow the elucidation of their anticancer mechanisms of action and allow the identification of phytochemicals that are responsible for their anticancer properties. Overall, this review provides consolidated and extensive information not only on diverse medicinal plants of Africa but on the different types of cancer that these plants are used to manage and the diverse mechanisms and pathways that are involved during cancer alleviation.

Withaferin A: A Pleiotropic Anticancer Agent from the Indian Medicinal Plant Withania somnifera (L.) Dunal

Cancer represents the second most deadly disease and one of the most important public health concerns worldwide. Surgery, chemotherapy, radiation therapy, and immune therapy are the major types of treatment strategies that have been implemented in cancer treatment. Unfortunately, these treatment options suffer from major limitations, such as drug-resistance and adverse effects, which may eventually result in disease recurrence. Many phytochemicals have been investigated for their antitumor efficacy in preclinical models and clinical studies to discover newer therapeutic agents with fewer adverse effects. Withaferin A, a natural bioactive molecule isolated from the Indian medicinal plant Withania somnifera (L.) Dunal, has been reported to impart anticancer activities against various cancer cell lines and preclinical cancer models by modulating the expression and activity of different oncogenic proteins. In this article, we have comprehensively discussed the biosynthesis of withaferin A as well as its antineoplastic activities and mode-of-action in in vitro and in vivo settings. We have also reviewed the effect of withaferin A on the expression of miRNAs, its combinational effect with other cytotoxic agents, withaferin A-based formulations, safety and toxicity profiles, and its clinical potential.

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.

A Direct Interaction between Cyclodextrins and TASK Channels Decreases the Leak Current in Cerebellar Granule Neurons

Simple Summary

Cyclodextrins are cyclic oligosaccharides used to deplete cholesterol from cellular membranes. The effects of methyl-β-cyclodextrin (MβCD) on cellular functions originate principally from reductions in cholesterol levels. In this study, using immunocytochemistry, heterologous expression of K2P channels, and cholesterol-depleting maneuvers, we provide evidence of expression in cultured rat cerebellar granule neurons (CGNs) of TWIK-1 (K2P1), TASK-1 (K2P3), TASK-3 (K2P9), and TRESK (K2P18) channels and their association with lipid rafts using the specific lipids raft markers. In addition, we show a direct blocking with MβCD of TASK-1 and TASK-3 channels as well as for the covalently concatenated heterodimer TASK-1/TASK-3.

Abstract

Two pore domain potassium channels (K2P) are strongly expressed in the nervous system (CNS), where they play a central role in excitability. These channels give rise to background K⁺ currents, also known as IK_SO (standing-outward potassium current). We detected the expression in primary cultured cerebellar granule neurons (CGNs) of TWIK-1 (K2P1), TASK-1 (K2P3), TASK-3 (K2P9), and TRESK (K2P18) channels by immunocytochemistry and their association with lipid rafts using the specific lipids raft markers flotillin-2 and caveolin-1. At the functional level, methyl-β-cyclodextrin (MβCD, 5 mM) reduced IK_SO currents by ~40% in CGN cells. To dissect out this effect, we heterologously expressed the human TWIK-1, TASK-1, TASK-3, and TRESK channels in HEK-293 cells. MβCD directly blocked TASK-1 and TASK-3 channels and the covalently concatenated heterodimer TASK-1/TASK-3 currents. Conversely, MβCD did not affect TWIK-1- and TRESK-mediated K+ currents. On the other hand, the cholesterol-depleting agent filipin III did not affect TASK-1/TASK-3 channels. Together, the results suggest that neuronal background K⁺ channels are associated to lipid raft environments whilst the functional activity is independent of the cholesterol membrane organization.

Role of Plant-Derived Active Constituents in Cancer Treatment and Their Mechanisms of Action

Despite significant technological advancements in conventional therapies, cancer remains one of the main causes of death worldwide. Although substantial progress has been made in the control and treatment of cancer, several limitations still exist, and there is scope for further advancements. Several adverse effects are associated with modern chemotherapy that hinder cancer treatment and lead to other critical disorders. Since ancient times, plant-based medicines have been employed in clinical practice and have yielded good results with few side effects. The modern research system and advanced screening techniques for plants’ bioactive constituents have enabled phytochemical discovery for the prevention and treatment of challenging diseases such as cancer. Phytochemicals such as vincristine, vinblastine, paclitaxel, curcumin, colchicine, and lycopene have shown promising anticancer effects. Discovery of more plant-derived bioactive compounds should be encouraged via the exploitation of advanced and innovative research techniques, to prevent and treat advanced-stage cancers without causing significant adverse effects. This review highlights numerous plant-derived bioactive molecules that have shown potential as anticancer agents and their probable mechanisms of action and provides an overview of in vitro, in vivo and clinical trial studies on anticancer phytochemicals.

Withania somnifera (L.) Dunal: Phytochemistry, structure-activity relationship, and anticancer potential

BACKGROUND

Ayurveda is a highly recognized, well-documented, and well-accepted traditional medicine system. This system utilizes many natural products in various forms for therapeutic purposes. Thousands of plants mentioned in the Ayurvedic system are useful in disease mitigation and health preservation. One potential plant of the Ayurvedic system is "Ashwagandha" [Withania somnifera (L.) Dunal], commonly regarded as Indian Ginseng. It possesses various therapeutic activities, such as neuroprotective, hypoglycemic, hepatoprotective, antiarthritic, and anticancer effects.

PURPOSE

Here we present a comprehensive insight on the anticancer effects of W. somnifera and mechanistic attributes of its bioactive phytocompounds. This review also provides updated information on the clinical studies pertaining to cancer, safety evaluation and opportunities for chemical modifications of withanolides, a group of specialized phytochemicals of W. somnifera.

METHODS

The present study was performed in accordance with the guidelines of the Preferred Reporting Items for Systemic Reviews and Meta-Analysis. Various scientific databases, such as PubMed, Science Direct, Scopus, Google Scholar, were explored for related studies published up to May 2021.

RESULTS

An updated review on the anticancer potential and mechanisms of action of the major bioactive components of W. somnifera, including withanolides, withaferin A and withanone, is presented. Comprehensive information on clinical attributes of W. somnifera and its active components are presented with the structure-activity relationship (SAR) and toxicity evaluation.

CONCLUSION

The outcome of the work clearly indicates that W. somnifera has a significant potential for cancer therapy. The SAR revealed that various withanolides in general and withaferin A in particular have binding energies against various proteins and tremendous potential to serve as the lead for new chemical entities. Nevertheless, additional studies, particularly well-designed clinical trials are required before therapeutic application of withanolides for cancer treatment.

Significance of a PTEN Mutational Status-Associated Gene Signature in the Progression and Prognosis of Endometrial Carcinoma

BACKGROUND

PTEN mutations have been reported to be involved in the development and prognosis of endometrial carcinoma (EC). However, a prognostic gene signature associated with PTEN mutational status has not yet been developed. In this study, we generated a PTEN mutation-associated prognostic gene signature for EC.

METHODS

We obtained the single-nucleotide variation and transcriptomic profiling data from The Cancer Genome Atlas database as training data and implemented the least absolute shrinkage and selection operator (LASSO) Cox regression algorithm to establish a PTEN mutation-associated prognostic gene signature. The overall survival rates of the high-risk and low-risk groups were determined with the Kaplan-Meier (K-M) method, and the accuracy of risk score prediction was tested by using the receiver operating characteristic (ROC) curve.

RESULTS

The K-M curves revealed that the EC patients with PTEN mutations augured favorable survival outcomes. Differential expression analysis between the EC patients with PTEN mutation and wild-type PTEN identified 224 differentially expressed genes (DEGs). Eighty-four DEGs that manifested prognostic value were fitted into the LASSO-Cox analysis, and a PTEN gene signature with seven mutation-associated prognostic genes that showed robust prognostic ability was constructed; this signature was then successfully validated in the other two datasets from the cBioPortal database as well as with 60 clinical specimens. Furthermore, the PTEN mutation-associated prognostic gene signature proved to be an independent prognostic predictor of EC. Remarkably, the EC patients in the high-risk group were characterized by higher tumor stages and grades as well as lower tumor mutation burden with respect to EC, with a poor survival outcome. Collectively, the PTEN mutation-associated prognostic gene signature that we developed could now be used as a favorable prognostic biomarker for EC.

CONCLUSION

In summary, we developed and validated a prognostic predictor for EC associated with PTEN mutational status that may be used as a favorable prognostic biomarker and therapeutic target for EC.

Alternative Targets for Modulators of Mitochondrial Potassium Channels

Mitochondrial potassium channels control potassium influx into the mitochondrial matrix and thus regulate mitochondrial membrane potential, volume, respiration, and synthesis of reactive oxygen species (ROS). It has been found that pharmacological activation of mitochondrial potassium channels during ischemia/reperfusion (I/R) injury activates cytoprotective mechanisms resulting in increased cell survival. In cancer cells, the inhibition of these channels leads to increased cell death. Therefore, mitochondrial potassium channels are intriguing targets for the development of new pharmacological strategies. In most cases, however, the substances that modulate the mitochondrial potassium channels have a few alternative targets in the cell. This may result in unexpected or unwanted effects induced by these compounds. In our review, we briefly present the various classes of mitochondrial potassium (mitoK) channels and describe the chemical compounds that modulate their activity. We also describe examples of the multidirectional activity of the activators and inhibitors of mitochondrial potassium channels.

Strategies for the treatment of breast cancer: from classical drugs to mathematical models

Breast cancer is one of the most common cancers and generally affects women. It is a heterogeneous disease that presents different entities, different biological characteristics, and differentiated clinical behaviors. With this in mind, this literature review had as its main objective to analyze the path taken from the simple use of classical drugs to the application of mathematical models, which through the many ongoing studies, have been considered as one of the reliable strategies, explaining the reasons why chemotherapy is not always successful. Besides, the most commonly mentioned strategies are immunotherapy, which includes techniques and therapies such as the use of antibodies, cytokines, antitumor vaccines, oncolytic and genomic viruses, among others, and nanoparticles, including metallic, magnetic, polymeric, liposome, dendrimer, micelle, and others, as well as drug reuse, which is a process by which new therapeutic indications are found for existing and approved drugs. The most commonly used pharmacological categories are cardiac, antiparasitic, anthelmintic, antiviral, antibiotic, and others. For the efficient development of reused drugs, there must be a process of exchange of purposes, methods, and information already available, and for their better understanding, computational mathematical models are then used, of which the methods of blind search or screening, based on the target, knowledge, signature, pathway or network and the mechanism to which it is directed, stand out. To conclude it should be noted that these different strategies can be applied alone or in combination with each other always to improve breast cancer treatment.

5-(Indol-2-yl)pyrazolo[3,4-b]pyridines as a New Family of TASK-3 Channel Blockers: A Pharmacophore-Based Regioselective Synthesis

TASK channels belong to the two-pore-domain potassium (K_2P) channels subfamily. These channels modulate cellular excitability, input resistance, and response to synaptic stimulation. TASK-channel inhibition led to membrane depolarization. TASK-3 is expressed in different cancer cell types and neurons. Thus, the discovery of novel TASK-3 inhibitors makes these bioactive compounds very appealing to explore new cancer and neurological therapies. TASK-3 channel blockers are very limited to date, and only a few heterofused compounds have been reported in the literature. In this article, we combined a pharmacophore hypothesis with molecular docking to address for the first time the rational design, synthesis, and evaluation of 5-(indol-2-yl)pyrazolo[3,4-b]pyridines as a novel family of human TASK-3 channel blockers. Representative compounds of the synthesized library were assessed against TASK-3 using Fluorometric imaging plate reader-Membrane Potential assay (FMP). Inhibitory properties were validated using two-electrode voltage-clamp (TEVC) methods. We identified one active hit compound (MM-3b) with our systematic pipeline, exhibiting an IC₅₀ ≈ 30 μM. Molecular docking models suggest that compound MM-3b binds to TASK-3 at the bottom of the selectivity filter in the central cavity, similar to other described TASK-3 blockers such as A1899 and PK-THPP. Our in silico and experimental studies provide a new tool to predict and design novel TASK-3 channel blockers.

Mitochondrial K+ channels and their implications for disease mechanisms

The field of mitochondrial ion channels underwent a rapid development during the last decade, thanks to the molecular identification of some of the nuclear-encoded organelle channels and to advances in strategies allowing specific pharmacological targeting of these proteins. Thereby, genetic tools and specific drugs aided definition of the relevance of several mitochondrial channels both in physiological as well as pathological conditions. Unfortunately, in the case of mitochondrial K⁺ channels, efforts of genetic manipulation provided only limited results, due to their dual localization to mitochondria and to plasma membrane in most cases. Although the impact of mitochondrial K⁺ channels on human diseases is still far from being genuinely understood, pre-clinical data strongly argue for their substantial role in the context of several pathologies, including cardiovascular and neurodegenerative diseases as well as cancer. Importantly, these channels are druggable targets, and their in-depth investigation could thus pave the way to the development of innovative small molecules with huge therapeutic potential. In the present review we summarize the available experimental evidence that mechanistically link mitochondrial potassium channels to the above pathologies and underline the possibility of exploiting them for therapy.

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.