KCa1.1 K+ Channel Inhibition Overcomes Resistance to Antiandrogens and Doxorubicin in a Human Prostate Cancer LNCaP Spheroid Model

Development and therapeutic implications of small molecular inhibitors that target calcium-related channels in tumor treatment

Calcium ion dysregulation exerts profound effects on various physiological activities such as tumor proliferation, migration, and drug resistance. Calcium-related channels play a regulatory role in maintaining calcium ion homeostasis, with most channels being highly expressed in tumor cells. Additionally, these channels serve as potential drug targets for the development of antitumor medications. In this review, we first discuss the current research status of these pathways, examining how they modulate various tumor functions such as epithelial-mesenchymal transition (EMT), metabolism, and drug resistance. Simultaneously, we summarize the recent progress in the study of novel small-molecule drugs over the past 5 years and their current status.

Transcriptional Up-Regulation of FBXW7 by KCa1.1 K+ Channel Inhibition through the Nrf2 Signaling Pathway in Human Prostate Cancer LNCaP Cell Spheroid Model

The tumor suppressor gene F-box and WD repeat domain-containing (FBXW) 7 reduces cancer stemness properties by promoting the protein degradation of pluripotent stem cell markers. We recently demonstrated the transcriptional repression of FBXW7 by the three-dimensional (3D) spheroid formation of several cancer cells. In the present study, we found that the transcriptional activity of FBXW7 was promoted by the inhibition of the Ca2+-activated K+ channel, KCa1.1, in a 3D spheroid model of human prostate cancer LNCaP cells through the Akt-Nrf2 signaling pathway. The transcriptional activity of FBXW7 was reduced by the siRNA-mediated inhibition of the CCAAT-enhancer-binding protein C/EBP δ (CEBPD) after the transfection of miR223 mimics in the LNCaP spheroid model, suggesting the transcriptional regulation of FBXW7 through the Akt-Nrf2-CEBPD-miR223 transcriptional axis in the LNCaP spheroid model. Furthermore, the KCa1.1 inhibition-induced activation of FBXW7 reduced (1) KCa1.1 activity and protein levels in the plasma membrane and (2) the protein level of the cancer stem cell (CSC) markers, c-Myc, which is a molecule degraded by FBXW7, in the LNCaP spheroid model, indicating that KCa1.1 inhibition-induced FBXW7 activation suppressed CSC conversion in KCa1.1-positive cancer cells.

Tumor promoting effect of spheroids in an orthotopic prostate cancer mouse model

In this study, we aimed to establish a technique for intraprostatic implantation of prostate cancer (PCa) spheroids and to identify the impact of three-dimensional organization of PCa cells on tumor progression and metastasis in a representative in vivo model. 40,000 LNCaP cells were implanted into the prostate of immunodeficient SCID mice either as single cells (n = 8) or as preformed 3D spheroids (n = 8). For a follow up of 20 weeks, tumor growth was monitored by serum PSA and high-resolution 3D ultrasonography. Eventually, animals were sacrificed and autopsied. The organ dissects were analyzed for the presence of metastases by histology (H&E) and immunohistochemistry (AMACR, AR, Ki-67, CK5, CK8, E-Cadherin, Vimentin). Solid intraprostatic tumors developed in 50% of mice after spheroid implantation and in 50% of mice after implantation of a single cells. Primary tumors of LNCaP spheroids evolved earlier, exhibiting a shorter tumor doubling time whilst developing larger tumor volumes, which was reflected by a higher immunohistochemical expression of Ki-67 and AR, too. Spheroid tumors established lung and lymph node metastases in 75% of mice, in contrast to 50% of mice after single cell implantation. Our technique enables a variety of studies regarding the influence of the tumor microenvironment on PCa progression.

Anti-proliferative, Pro-apoptotic, and Chemosensitizing Potential of 3-Acetyl-11-keto-β-boswellic Acid (AKBA) Against Prostate Cancer Cells

Prostate cancer incidences are rising worldwide at an alarming rate. Drug resistance and relapse are two major challenges in the treatment of prostate cancer. Therefore, new multimodal, safe, and effective therapeutic agents are urgently required which could effectively mitigate the menace of tumor recurrence and chemo-resistance. Plant-derived products are increasingly being utilized due to their antioxidant, antibacterial, and anti-tumor potential. In the current study, 3-acetyl-11-keto-β-boswellic acid, a triterpenoid isolated from plant Boswellia, was utilized to ascertain its chemotherapeutic potential against human prostate cancer cells. Various in vitro assays including cell viability, nuclear staining, mitochondria potential, reactive oxygen species (ROS) generation, and quantification of apoptosis, were performed for the evaluation of the cytotoxic potential of AKBA. We observed that AKBA (10-50 µM) dose-dependently suppressed cell proliferation and caused programmed cell death in PC3 cells via both intrinsic and extrinsic pathway. Intriguingly, AKBA was also found to chemosensitize PC3 cells in synergistic combination with doxorubicin. To the best of our knowledge, this is the first study to document the synergistic chemosensitizing impact of AKBA when combined with doxorubicin in prostate cancer cells.This showcases the potential of AKBA in combinatorial therapy or adjuvant therapy for the management of prostate cancer. In sum, our results suggested that AKBA is a promising drug-like molecule against prostate cancer. Our investigation introduces a novel perspective, elucidating a previously unexplored dimension, and uncovering a compelling chemosensitizing phenomenon along with a strong synergistic effect arising from the concurrent application of these two agents.

Advances in ion channel high throughput screening: where are we in 2023?

INTRODUCTION

Automated Patch Clamp (APC) technology has become an integral element in ion channel research, drug discovery and development pipelines to overcome the use of the highly time-consuming manual patch clamp (MPC) procedures. This automated technology offers increased throughput and promises a new model in obtaining ion channel recordings, which has significant relevance to the development of novel therapies and safety profiling of candidate therapeutic compounds.

AREAS COVERED

This article reviews the recent innovations in APC technology, including platforms, and highlights how they have facilitated usage in both industry and academia. The review also provides an overview of the ion channel research endeavors and how APC platforms have contributed to the understanding of ion channel research, pharmacological tools and therapeutics. Furthermore, the authors provide their opinion on the challenges and goals for APC technology going forward to accelerate academic research and drug discovery across a host of therapeutic areas.

EXPERT OPINION

It is clear that APC technology has progressed drug discovery programs, specifically in the field of neuroscience and cardiovascular research. The challenge for the future is to keep pace with fundamental research and improve translation of the large datasets obtained.

Down-Regulation of CYP3A4 by the KCa1.1 Inhibition Is Responsible for Overcoming Resistance to Doxorubicin in Cancer Spheroid Models

The large-conductance Ca2+-activated K+ channel, KCa1.1, plays a pivotal role in cancer progression, metastasis, and the acquisition of chemoresistance. Previous studies indicated that the pharmacological inhibition of KCa1.1 overcame resistance to doxorubicin (DOX) by down-regulating multidrug resistance-associated proteins in the three-dimensional spheroid models of human prostate cancer LNCaP, osteosarcoma MG-63, and chondrosarcoma SW-1353 cells. Investigations have recently focused on the critical roles of intratumoral, drug-metabolizing cytochrome P450 enzymes (CYPs) in chemoresistance. In the present study, we examined the involvement of CYPs in the acquisition of DOX resistance and its overcoming by inhibiting KCa1.1 in cancer spheroid models. Among the CYP isoforms involved in DOX metabolism, CYP3A4 was up-regulated by spheroid formation and significantly suppressed by the inhibition of KCa1.1 through the transcriptional repression of CCAAT/enhancer-binding protein, CEBPB, which is a downstream transcription factor of the Nrf2 signaling pathway. DOX resistance was overcome by the siRNA-mediated inhibition of CYP3A4 and treatment with the potent CYP3A4 inhibitor, ketoconazole, in cancer spheroid models. The phosphorylation levels of Akt were significantly reduced by inhibiting KCa1.1 in cancer spheroid models, and KCa1.1-induced down-regulation of CYP3A4 was reversed by the treatment with Akt and Nrf2 activators. Collectively, the present results indicate that the up-regulation of CYP3A4 is responsible for the acquisition of DOX resistance in cancer spheroid models, and the inhibition of KCa1.1 overcame DOX resistance by repressing CYP3A4 transcription mainly through the Akt-Nrf2-CEBPB axis.

SKCa- and Kv1-type potassium channels and cancer: Promising therapeutic targets?

Ion channels are transmembrane structures that allow the passage of ions across cell membranes such as the plasma membrane or the membranes of various organelles like the nucleus, endoplasmic reticulum, Golgi apparatus or mitochondria. Aberrant expression of various ion channels has been demonstrated in several tumor cells, leading to the promotion of key functions in tumor development, such as cell proliferation, resistance to apoptosis, angiogenesis, invasion and metastasis. The link between ion channels and these key biological functions that promote tumor development has led to the classification of cancers as oncochannelopathies. Among all ion channels, the most varied and numerous, forming the largest family, are the potassium channels, with over 70 genes encoding them in humans. In this context, this review will provide a non-exhaustive overview of the role of plasma membrane potassium channels in cancer, describing 1) the nomenclature and structure of potassium channels, 2) the role of these channels in the control of biological functions that promotes tumor development such as proliferation, migration and cell death, and 3) the role of two particular classes of potassium channels, the SKCa- and Kv1- type potassium channels in cancer progression.

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.

Let’s Go 3D! New Generation of Models for Evaluating Drug Response and Resistance in Prostate Cancer

Prostate cancer (PC) is the third most frequently diagnosed cancer worldwide and the second most frequent in men. Several risk factors can contribute to the development of PC, and those include age, family history, and specific genetic mutations. So far, drug testing in PC, as well as in cancer research in general, has been performed on 2D cell cultures. This is mainly because of the vast benefits these models provide, including simplicity and cost effectiveness. However, it is now known that these models are exposed to much higher stiffness; lose physiological extracellular matrix on artificial plastic surfaces; and show changes in differentiation, polarization, and cell–cell communication. This leads to the loss of crucial cellular signaling pathways and changes in cell responses to stimuli when compared to in vivo conditions. Here, we emphasize the importance of a diverse collection of 3D PC models and their benefits over 2D models in drug discovery and screening from the studies done so far, outlining their benefits and limitations. We highlight the differences between the diverse types of 3D models, with the focus on tumor–stroma interactions, cell populations, and extracellular matrix composition, and we summarize various standard and novel therapies tested on 3D models of PC for the purpose of raising awareness of the possibilities for a personalized approach in PC therapy.

The modulation of ion channels in cancer chemo-resistance

Ion channels modulate the flow of ions into and out of a cell or intracellular organelle, leading to generation of electrical or chemical signals and regulating ion homeostasis. The abundance of ion channels in the plasma and intracellular membranes are subject to physiological and pathological regulations. Abnormal and dysregulated expressions of many ion channels are found to be linked to cancer and cancer chemo-resistance. Here, we will summarize ion channels distribution in multiple tumors. And the involvement of ion channels in cancer chemo-resistance will be highlighted.

Single ion channel recording in 3D culture of stem cells using patch-clamp technique

Tri-dimensional (3D) cell aggregates or spheroids are considered to be closer to physiological conditions than traditional 2D cell culture. Mesenchymal stem cells (MSCs) assembling in spheroids have increased the survival of transplanted cells. The organization of stem cells in 3D culture affects cell microenvironment and their mechanical properties. The regulation of the biological processes that maintain crucial physiological reactions of MSCs is closely related to the functioning of ion channels. The pattern of expression, role and regulatory mechanisms of ion channels could be significantly different in 3D compared to 2D culture, and, thus, needed to be properly analyzed on the level of ionic currents. Electrophysiological data on the features of ion channels functioning in 3D cell culture models are currently very limited in the literature. This gap of knowledge may be associated with technical difficulties that exist when researchers try to apply the standard patch clamp method for the registration of ion channels in cells aggregated in spheroids. In this regard, our study focuses on solving emerging technical difficulties and presents an example of their successful solution. Here, we developed a specific approach and have recorded the activity of mechanosensitive stretch-activated ion channels (SACs) in endometrial MSCs (eMSCs) assembled in spheroids. Moreover, we observed functional interplay of SACs with potassium channels of big conductance (BK) in the plasma membrane of eMSC spheroids consistently to revealed earlier in routine 2D cultured cells. Additionally, we observed a significant decrease in the frequency of SACs activation in spheroids that may indicate the differences in the level of functional expression of channels in 3D culture comparing to 2D culture of eMSCs.