Glioblastoma cancer stem cell lines express functional acid sensing ion channels ASIC1a and ASIC3

Doxorubicin-loaded liposome-like particles embedded in chitosan/hyaluronic acid-based hydrogels as a controlled drug release model for local treatment of glioblastoma

Glioblastoma (GBM) resection and medication treatment are limited, and local drug therapies are required. This study aims to create a hybrid system comprising liposome-like particles (LLP-DOX) encapsulated in chitosan/hyaluronic acid/polyethyleneimine (CHI/HA/PEI) hydrogels, enabling controlled local delivery of doxorubicin (DOX) into the resection cavity for treating GBM. CHI/HA/PEI hydrogels were characterized morphologically, physically, chemically, mechanically, and thermally. Findings revealed a high network and compact micro-network structure, along with enhanced physical and thermal stability compared to CHI/HA hydrogels. Simultaneously, drug release from CHI/HA/PEI/LLP-DOX hydrogels was assessed, revealing continuous and controlled release up to the 148th hour, with no significant burst release. Cell studies showed that CHI/HA/PEI hydrogels are biocompatible with low genotoxicity. Additionally, LLP-DOX-loaded CHI/HA/PEI hydrogels significantly decreased cell viability and gene expression levels compared to LLP-DOX alone. It was also observed that the viability of GBM spheroids decreased over time when interacting with CHI/HA/PEI/LLP-DOX hydrogels, accompanied by a reduction in total surface area and an increase in apoptotic tendencies. In this study, we hypothesized that creating a hybrid drug delivery system by encapsulating DOX-loaded LLPs within a CHI/HA/PEI hydrogel matrix could achieve sustained drug release, improve anticancer efficacy via localized treatment, and effectively mitigate GBM progression for 3D microtissues.

Modulating voltage-gated sodium channels to enhance differentiation and sensitize glioblastoma cells to chemotherapy

BACKGROUND

Glioblastoma (GBM) stands as the most prevalent and aggressive form of adult gliomas. Despite the implementation of intensive therapeutic approaches involving surgery, radiation, and chemotherapy, Glioblastoma Stem Cells contribute to tumor recurrence and poor prognosis. The induction of Glioblastoma Stem Cells differentiation by manipulating the transcriptional machinery has emerged as a promising strategy for GBM treatment. Here, we explored an innovative approach by investigating the role of the depolarized resting membrane potential (RMP) observed in patient-derived GBM sphereforming cell (GSCs), which allows them to maintain a stemness profile when they reside in the G0 phase of the cell cycle.

METHODS

We conducted molecular biology and electrophysiological experiments, both in vitro and in vivo, to examine the functional expression of the voltage-gated sodium channel (Nav) in GSCs, particularly focusing on its cell cycle-dependent functional expression. Nav activity was pharmacologically manipulated, and its effects on GSCs behavior were assessed by live imaging cell cycle analysis, self-renewal assays, and chemosensitivity assays. Mechanistic insights into the role of Nav in regulating GBM stemness were investigated through pathway analysis in vitro and through tumor proliferation assay in vivo.

RESULTS

We demonstrated that Nav is functionally expressed by GSCs mainly during the G0 phase of the cell cycle, suggesting its pivotal role in modulating the RMP. The pharmacological blockade of Nav made GBM cells more susceptible to temozolomide (TMZ), a standard drug for this type of tumor, by inducing cell cycle re-entry from G0 phase to G1/S transition. Additionally, inhibition of Nav substantially influenced the self-renewal and multipotency features of GSCs, concomitantly enhancing their degree of differentiation. Finally, our data suggested that Nav positively regulates GBM stemness by depolarizing the RMP and suppressing the ERK signaling pathway. Of note, in vivo proliferation assessment confirmed the increased susceptibility to TMZ following pharmacological blockade of Nav.

CONCLUSIONS

This insight positions Nav as a promising prognostic biomarker and therapeutic target for GBM patients, particularly in conjunction with temozolomide treatment.

Acid-sensing ion channel 3 is a new potential therapeutic target for the control of glioblastoma cancer stem cells growth

Glioblastoma (GBM) is the most common malignant primary brain cancer that, despite recent advances in the understanding of its pathogenesis, remains incurable. GBM contains a subpopulation of cells with stem cell-like properties called cancer stem cells (CSCs). Several studies have demonstrated that CSCs are resistant to conventional chemotherapy and radiation thus representing important targets for novel anti-cancer therapies. Proton sensing receptors expressed by CSCs could represent important factors involved in the adaptation of tumours to the extracellular environment. Accordingly, the expression of acid-sensing ion channels (ASICs), proton-gated sodium channels mainly expressed in the neurons of peripheral (PNS) and central nervous system (CNS), has been demonstrated in several tumours and linked to an increase in cell migration and proliferation. In this paper we report that the ASIC3 isoform, usually absent in the CNS and present in the PNS, is enriched in human GBM CSCs while poorly expressed in the healthy human brain. We propose here a novel therapeutic strategy based on the pharmacological activation of ASIC3, which induces a significant GBM CSCs damage while being non-toxic for neurons. This approach might offer a promising and appealing new translational pathway for the treatment of glioblastoma.

TFCP2 as a therapeutic nexus: unveiling molecular signatures in cancer

Tumor suppressor genes and proto-oncogenes comprise most of the complex genomic landscape associated with cancer, with a minimal number of genes exhibiting dual-context-dependent functions. The transcription factor cellular promoter 2 (TFCP2), a pivotal transcription factor encoded by the alpha globin transcription factor CP2 gene, is a constituent of the TFCP2/grainyhead family of transcription factors. While grainyhead members have been extensively studied for their crucial roles in developmental processes, embryogenesis, and multiple cancers, the TFCP2 subfamily has been relatively less explored. The molecular mechanisms underlying TFCP2's involvement in carcinogenesis are still unclear even though it is a desirable target for cancer treatment and a therapeutic marker. This comprehensive literature review summarizes the molecular functions of TFCP2, emphasizing its involvement in cancer pathophysiology, particularly in the epithelial-mesenchymal transition and metastasis. It highlights TFCP2's critical function as a regulatory target and explores its potential as a prognostic marker for survival and inflammation in carcinomas. Its ambiguous association with carcinomas underlines the urgent need for an in-depth understanding to facilitate the development of more efficacious targeted therapeutic modality and diagnostic tools. This study aims to elucidate the multifaceted effects of TFCP2 regulation, through a comprehensive integration of the existing knowledge in cancer therapeutics. Furthermore, the clinical relevance and the inherent challenges encountered in investigating its intricate role in cancer pathogenesis have been discussed in this review.

ASIC3-activated key enzymes of de novo lipid synthesis supports lactate-driven EMT and the metastasis of colorectal cancer cells

Acidic microenvironments is a cancer progression driver, unclear core mechanism hinders the discovery of new diagnostic or therapeutic targets. ASIC3 is an extracellular proton sensor and acid-sensitive, but its role in acidic tumor microenvironment of colorectal cancer is not reported. Functional analysis data show that colorectal cancer cells respond to specific concentration of lactate to accelerate invasion and metastasis, and ASIC3 is the main actor in this process. Mechanism reveal de novo lipid synthesis is a regulatory process of ASIC3, down-regulated ASIC3 increases and interacts with ACC1 and SCD1, which are key enzymes in de novo lipid synthesis pathway, this interaction results in increased unsaturated fatty acids, which in turn induce EMT to promote metastasis, and overexpression of ASIC3 reduces acidic TME-enhanced colorectal cancer metastasis. Clinical samples of colorectal cancer also exhibit decreased ASIC3 expression, and low ASIC3 expression is associated with metastasis and stage of colorectal cancer. This study is the first to identify the role of the ASIC3-ACC1/SCD1 axis in acid-enhanced colorectal cancer metastasis. The expression pattern of ASIC3 in colorectal cancer differs significantly from that in other types of cancers, ASIC3 may serve as a novel and reliable marker for acidic microenvironmental in colorectal cancer, and potentially a therapeutic target.

Acid-sensing ion channels and downstream signalling in cancer cells: is there a mechanistic link?

It is increasingly appreciated that the acidic microenvironment of a tumour contributes to its evolution and clinical outcomes. However, our understanding of the mechanisms by which tumour cells detect acidosis and the signalling cascades that it induces is still limited. Acid-sensing ion channels (ASICs) are sensitive receptors for protons; therefore, they are also candidates for proton sensors in tumour cells. Although in non-transformed tissue, their expression is mainly restricted to neurons, an increasing number of studies have reported ectopic expression of ASICs not only in brain cancer but also in different carcinomas, such as breast and pancreatic cancer. However, because ASICs are best known as desensitizing ionotropic receptors that mediate rapid but transient signalling, how they trigger intracellular signalling cascades is not well understood. In this review, we introduce the acidic microenvironment of tumours and the functional properties of ASICs, point out some conceptual problems, summarize reported roles of ASICs in different cancers, and highlight open questions on the mechanisms of their action in cancer cells. Finally, we propose guidelines to keep ASIC research in cancer on solid ground.

Analysis of the Expression of LSF Transcription Factor in the Regulation of Transcription and TSG101 during the Neoplastic Transformation of Endometrial Cells

Previous research indicates that carcinogenesis involves disrupting the functions of numerous genes, including factors involved in the regulation of transcription and cell proliferation. For these reasons, in endometrial carcinogenesis, we decided to investigate the expression of TSG101 (a suppressor of tumor transformation) and LSF (a transcription factor involved in numerous cellular processes, such as cell cycle regulation, cell growth, development, and apoptosis). LSF may be involved in the regulation of TSG101 expression. The research material consisted of endometrial cancer samples from 60 patients. The control group consisted of normal endometrium samples donated by 60 women undergoing surgery for benign diseases of the female reproductive organs. The samples were subjected to immunohistochemical staining with antibodies specific to TSG101 and LSF. Specific antibodies were used to identify TSG101 and LSF in the examined histopathological preparations. An approximately 14-fold lower risk of endometrial cancer development was observed in patients with TSG expression in more than 75% of the assessed cells (4% vs. 36%; OR = 0.07; p = 0.0182). There was a four-fold lower risk of endometrial cancer development in patients with LSF expression in more than 50% of the assessed cells (32% vs. 64%; OR = 0.26; p = 0.0262). A more than three-fold lower risk of endometrial cancer development was observed in patients with LSF expression in more than 75% of the assessed cells (24% vs. 52%; OR = 0.29; p = 0.0454). Endometrial cancer was diagnosed in those with a lower level of TSG101 expression than in those with a cancer-free endometrium. Decreased expression of TSG101 may be a marker of endometrial cancer, and increased expression of LSF when diagnosed with endometrial cancer may indicate greater advancement of the disease. These markers might be used as diagnostic and prognostic markers-however, there is a lack of a correlation between them.

Functional characterization of acid-sensing ion channels in the cerebellum-originating medulloblastoma cell line DAOY and in cerebellar granule neurons

Acid-sensing ion channels (ASICs) are Na+ channels that are almost ubiquitously expressed in neurons of the brain. Functional ASIC1a is also expressed in glioblastoma stem cells, where it might sense the acidic tumor microenvironment. Prolonged acidosis induces cell death in neurons and reduces tumor sphere formation in glioblastoma via activation of ASIC1a. It is currently unknown whether ASICs are expressed and involved in acid-induced cell death in other types of brain tumors. In this study, we investigated ASICs in medulloblastoma, using two established cell lines, DAOY and UW228, as in vitro models. In addition, we characterized ASICs in the most numerous neuron of the brain, the cerebellar granule cell, which shares the progenitor cell with some forms of medulloblastoma. We report compelling evidence using RT-qPCR, western blot and whole-cell patch clamp that DAOY and cerebellar granule cells, but not UW228 cells, functionally express homomeric ASIC1a. Additionally, Ca2+-imaging revealed that extracellular acidification elevated intracellular Ca2+-levels in DAOY cells independently of ASICs. Finally, we show that overexpression of RIPK3, a key component of the necroptosis pathway, renders DAOY cells susceptible to acid-induced cell death via activation of ASIC1a. Our data support the idea that ASIC1a is an important acid sensor in brain tumors and that its activation has potential to induce cell death in tumor cells.

Construction of a prediction model for prognosis of bladder cancer based on the expression of ion channel-related genes

OBJECTIVES

To construct a prediction model for the prognosis of bladder cancer patients based on the expression of ion channel-related genes (ICRGs).

METHODS

ICRGs were obtained from the existing researches. The clinical information and the expression of ICRGs mRNA in breast cancer patients were obtained from the Cancer Genome Atlas database. Cox regression analysis, minimum absolute shrinkage and selection operator regression analysis were used to screen breast cancer prognosis related genes, which were verified by immunohistochemistry and qRT-PCR. The risk scoring equation for predicting the prognosis of patients with bladder cancer was constructed, and the patients were divided into high-risk group and low-risk group according to the median risk score. Immune cell infiltration was compared between the two groups. Kaplan-Meier survival curve and receiver operating characteristic (ROC) curve were used to evaluate the accuracy and clinical application value of the risk scoring equation. The factors related to the prognosis of bladder cancer patients were analyzed by univariate and multivariate Cox regression, and a nomogram for predicting the prognosis of bladder cancer patients was constructed.

RESULTS

By comparing the expression levels of ICRGs in bladder cancer tissues and normal bladder tissues, 73 differentially expressed ICRGs were dentified, of which 11 were related to the prognosis of bladder cancer patients. Kaplan-Meier survival curve suggested that the risk score based on these 11 genes was negatively correlated with the prognosis of patients. The area under the ROC curve of the risk score for predicting the prognosis of patients at 1, 3 and 5 year was 0.634, 0.665 and 0.712, respectively. Stratified analysis showed that the ICRGs-based risk score performed well in predicting the prognosis of patients with American Joint Committee on Cancer (AJCC) stage Ⅲ-Ⅳ bladder cancer (P<0.05), while it had a poor value in predicting the prognosis of patients with AJCC stage Ⅰ-Ⅱ (P>0.05). There were significant differences in the infiltration of plasma cells, activated natural killer cells, resting mast cells and M2 macrophages between the high-risk group and the low-risk group. Cox regression analysis showed that risk score, smoking, age and AJCC stage were independently associated with the prognosis of patients with bladder cancer (P<0.05). The nomogram constructed by combining risk score and clinical parameters has high accuracy in predicting the 1, 3 and 5 year overall survival rate of bladder cancer patients.

CONCLUSIONS

The study shows the potential value of ICRGs in the prognostic risk assessment of bladder cancer patients. The constructed prognostic nomogram based on ICRGs risk score has high accuracy in predicting the prognosis of bladder cancer patients.

Ion Channels in Gliomas-From Molecular Basis to Treatment

Ion channels provide the basis for the nervous system's intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.

Modulators of ASIC1a and its potential as a therapeutic target for age-related diseases

Age-related diseases have become more common with the advancing age of the worldwide population. Such diseases involve multiple organs, with tissue degeneration and cellular apoptosis. To date, there is a general lack of effective drugs for treatment of most age-related diseases and there is therefore an urgent need to identify novel drug targets for improved treatment. Acid-sensing ion channel 1a (ASIC1a) is a degenerin/epithelial sodium channel family member, which is activated in an acidic environment to regulate pathophysiological processes such as acidosis, inflammation, hypoxia, and ischemia. A large body of evidence suggests that ASIC1a plays an important role in the development of age-related diseases (e.g., stroke, rheumatoid arthritis, Huntington's disease, and Parkinson's disease.). Herein we present: 1) a review of ASIC1a channel properties, distribution, and physiological function; 2) a summary of the pharmacological properties of ASIC1a; 3) and a consideration of ASIC1a as a potential therapeutic target for treatment of age-related disease.

Aggressive migration in acidic pH of a glioblastoma cancer stem cell line in vitro is independent of ASIC and KCa3.1 ion channels, but involves phosphoinositide 3-kinase

The microenvironment of proliferative and aggressive tumours, such as the brain tumour glioblastoma multiforme (GBM), is often acidic, hypoxic, and nutrient deficient. Acid-sensing ion channels (ASICs) are proton-sensitive Na⁺ channels that have been proposed to play a role in pH sensing and in modulation of cancer cell migration. We previously reported that primary glioblastoma stem cells (GSCs), which grow as multicellular tumour spheroids, express functional ASIC1a and ASIC3, whereas ASIC2a is downregulated in GSCs. Using a 2.5D migration assay, here we report that acidic pH dramatically increased migration of GSCs of the pro-neural subtype. Pharmacological blockade as well as CRISPR-Cas9-mediated gene knock-out of ASIC1a or stable overexpression of ASIC2a, however, revealed that neither ASIC1a nor ASIC3, nor downregulation of ASIC2a, mediated the aggressive migration at acidic pH. Therefore, we tested the role of two other proteins previously implicated in cancer cell migration: the Ca²⁺-activated K⁺ channel KCa3.1 (KCNN4) and phosphoinositide 3-kinase (PI3K). While pharmacological blockade of K_Ca3.1 did also not affect migration, blockade of PI3K decreased migration at acidic pH to control levels. In summary, our study reveals a strongly enhanced migration of GSCs at acidic pH in vitro and identifies PI3K as an important mediator of this effect.

Acidosis induces RIPK1-dependent death of glioblastoma stem cells via acid-sensing ion channel 1a

Eliciting regulated cell death, like necroptosis, is a potential cancer treatment. However, pathways eliciting necroptosis are poorly understood. It has been reported that prolonged activation of acid-sensing ion channel 1a (ASIC1a) induces necroptosis in mouse neurons. Glioblastoma stem cells (GSCs) also express functional ASIC1a, but whether prolonged activation of ASIC1a induces necroptosis in GSCs is unknown. Here we used a tumorsphere formation assay to show that slight acidosis (pH 6.6) induces necrotic cell death in a manner that was sensitive to the necroptosis inhibitor Nec-1 and to the ASIC1a antagonist PcTx1. In addition, genetic knockout of ASIC1a rendered GSCs resistant to acid-induced reduction in tumorsphere formation, while the ASIC1 agonist MitTx1 reduced tumorsphere formation also at neutral pH. Finally, a 20 amino acid fragment of the ASIC1 C-terminus, thought to interact with the necroptosis kinase RIPK1, was sufficient to reduce the formation of tumorspheres. Meanwhile, the genetic knockout of MLKL, the executive protein in the necroptosis cascade, did not prevent a reduction in tumor sphere formation, suggesting that ASIC1a induced an alternative cell death pathway. These findings demonstrate that ASIC1a is a death receptor on GSCs that induces cell death during prolonged acidosis. We propose that this pathway shapes the evolution of a tumor in its acidic microenvironment and that pharmacological activation of ASIC1a might be a potential new strategy in tumor therapy.

Meta-analysis on reporting practices as a source of heterogeneity in in vitro cancer research

Objectives

Heterogeneity of results of exact same research experiments oppose a significant socioeconomic burden. Insufficient methodological reporting is likely to be one of the contributors to results heterogeneity; however, little knowledge on reporting habits of in vitro cancer research and their effects on results reproducibility is available. Exemplified by a commonly performed in vitro assay, we aim to fill this knowledge gap and to derive recommendations necessary for reproducible, robust and translational preclinical science.

Methods

Here, we use systematic review to describe reporting practices in in vitro glioblastoma research using the Uppsala-87 Malignant Glioma (U-87 MG) cell line and perform multilevel random-effects meta-analysis followed by meta-regression to explore sources of heterogeneity within that literature, and any associations between reporting characteristics and reported findings. Literature that includes experiments measuring the effect of temozolomide on the viability of U-87 MG cells is searched on three databases (Embase, PubMed and Web of Science).

Results

In 137 identified articles, the methodological reporting is incomplete, for example, medium glucose level and cell density are reported in only 21.2% and 16.8% of the articles. After adjustments for different drug concentrations and treatment durations, the results heterogeneity across the studies (I2=68.5%) is concerningly large. Differences in culture medium glucose level are a driver of this heterogeneity. However, infrequent reporting of most experimental parameters limits the analysis of reproducibility moderating parameters.

Conclusions

Our results further support the ongoing efforts of establishing consensus reporting practices to elevate durability of results. By doing so, this work can raise awareness of how stricter reporting may help to improve the frequency of successful translation of preclinical results into human application. The authors received no specific funding for this work. A preregistered protocol is available at the Open Science Framework (https://osf.io/9k3dq).

Recent Advances in Acid-sensitive Ion Channels in Central Nervous System Diseases

Acid-sensitive ion channels (ASICs) are cationic channels activated by extracellular protons and widely distributed in the nervous system of mammals. It belongs to the ENaC/DEG family and has four coding genes: ASIC1, ASIC2, ASIC3, and ASIC4, which encode eight subunit proteins: ASIC1a, ASIC1b, ASIC1b2, ASIC2a, ASIC2b, ASIC3, ASIC4, and ASIC5. Different subtypes of ASICs have different distributions in the central nervous system, and they play an important role in various physiological and pathological processes of the central nervous system, including synaptic plasticity, anxiety disorders, fear conditioning, depression-related behavior, epilepsy, Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, malignant Glioma, pain, and others. This paper reviewed the recent studies of ASICs on the central nervous system to improve the understanding of ASICs' physiological functions and pathological effects. This article also provides a reference for studying the molecular mechanisms and therapeutic measures of nervous system-related diseases.

ASIC1a promotes the proliferation of synovial fibroblasts via the ERK/MAPK pathway

Synovial hyperplasia, a profound alteration in the structure of synovial tissue, is the basis for cumulative joint destruction in rheumatoid arthritis (RA). It is generally accepted that controlling synovial hyperplasia can delay the progression of RA. As one of the most intensively studied isoforms of acid-sensing ion channels (ASICs), ASIC1a contributes to various physiopathologic conditions, including RA, due to its unique property of being permeable to Ca2+. However, the role and the regulatory mechanisms of ASIC1a in synovial hyperplasia are poorly understood. Here, rats induced with adjuvant arthritis (AA) and human primary synovial fibroblasts were used in vivo and in vitro to investigate the role of ASIC1a in the proliferation of RA synovial fibroblasts (RASFs). The results show that the expression of ASIC1a was significantly increased in synovial tissues and RASFs obtained from patients with RA as well as in the synovium of rats with AA. Moreover, extracellular acidification improved the ability of RASFs colony formation and increased the expression of proliferation cell nuclear antigen (PCNA) and Ki67, which was abrogated by the specific ASIC1a inhibitor psalmotoxin-1 (PcTX-1) or ASIC1a-short hairpin RNA (ASIC1a-shRNA), suggesting that extracellular acidification promotes the proliferation of RASFs by activating ASIC1a. In addition, the activation of c-Raf and extracellular signal-regulated protein kinases (ERKs) signaling was blocked with PcTX-1 or ASIC1a-shRNA and the proliferation of RASFs was further inhibited by the ERK inhibitor (U0126), indicating that ERK/MAPK signaling contributes to the proliferation process of RASFs promoted by the activation of ASIC1a. These findings gave us an insight into the role of ASIC1a in the proliferation of RASFs, which may provide solid foundation for ASIC1a as a potential target in the treatment of RA.

Regulation of gliomagenesis and stemness through acid sensor ASIC1a

Glioblastoma multiforme (GBM) is the most prevalent and aggressive type of adult gliomas. Despite intensive therapy including surgery, radiation, and chemotherapy, invariable tumor recurrence occurs, which suggests that glioblastoma stem cells (GSCs) render these tumors persistent. Recently, the induction of GSC differentiation has emerged as an alternative method to treat GBM, and most of the current studies aim to convert GSCs to neurons by a combination of transcriptional factors. As the tumor microenvironment is typically acidic due to increased glycolysis and consequently leads to an increased production of lactic acid in tumor cells, in the present study, the role of acid‑sensing ion channel 1a (ASIC1a), an acid sensor, was explored as a tumor suppressor in gliomagenesis and stemness. The bioinformatics data from The Cancer Genome Atlas revealed that ASIC1 expression levels in GBM tumor tissues were lower than those in normal brain, and glioma patients with high ASIC1 expression had longer survival than those with low ASIC1 expression. Our immunohistochemistry data from tissue microarray revealed that ASIC1a expression was negatively associated with glioma grading. Functional studies revealed that the downregulation of ASIC1a promoted glioma cell proliferation and invasion, while upregulation of ASIC1a inhibited their proliferation and invasion. Furthermore, ASIC1a suppressed growth and proliferation of glioma cells through G1/S arrest and apoptosis induction. Mechanistically, ASIC1a negatively modulated glioma stemness via inhibition of the Notch signaling pathway and GSC markers CD133 and aldehyde dehydrogenase 1. ASIC1a is a tumor suppressor in gliomagenesis and stemness and may serve as a promising prognostic biomarker and target for GBM patients.

Acid-Sensing Ion Channels: Expression and Function in Resident and Infiltrating Immune Cells in the Central Nervous System

Peripheral and central immune cells are critical for fighting disease, but they can also play a pivotal role in the onset and/or progression of a variety of neurological conditions that affect the central nervous system (CNS). Tissue acidosis is often present in CNS pathologies such as multiple sclerosis, epileptic seizures, and depression, and local pH is also reduced during periods of ischemia following stroke, traumatic brain injury, and spinal cord injury. These pathological increases in extracellular acidity can activate a class of proton-gated channels known as acid-sensing ion channels (ASICs). ASICs have been primarily studied due to their ubiquitous expression throughout the nervous system, but it is less well recognized that they are also found in various types of immune cells. In this review, we explore what is currently known about the expression of ASICs in both peripheral and CNS-resident immune cells, and how channel activation during pathological tissue acidosis may lead to altered immune cell function that in turn modulates inflammatory pathology in the CNS. We identify gaps in the literature where ASICs and immune cell function has not been characterized, such as neurotrauma. Knowledge of the contribution of ASICs to immune cell function in neuropathology will be critical for determining whether the therapeutic benefits of ASIC inhibition might be due in part to an effect on immune cells.

Alteration and dysfunction of ion channels/transporters in a hypoxic microenvironment results in the development and progression of gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignant cancers in the world and has only few treatment options and, concomitantly, a poor prognosis. It is generally accepted now that the tumor microenvironment, particularly that under hypoxia, plays an important role in cancer development. Hypoxia can regulate the energy metabolism and malignancy of tumor cells by inducing or altering various important factors, such as oxidative stress, reactive oxygen species (ROS), hypoxia-inducible factors (HIFs), autophagy and acidosis. In addition, altered expression and/or dysfunction of ion channels/transporters (ICTs) have been encountered in a variety of human tumors, including GC, and to play an important role in the processes of tumor cell proliferation, migration, invasion and apoptosis. Increasing evidence indicates that ICTs are at least partly involved in interactions between cancer cells and their hypoxic microenvironment. Here, we provide an overview of the different ICTs that regulate or are regulated by hypoxia in GC.

CONCLUSIONS AND PERSPECTIVES

Hypoxia is one of the major obstacles to cancer therapy. Regulating cellular responses and factors under hypoxia can inhibit GC. Similarly, altering the expression or activity of ICTs, such as the application of ion channel inhibitors, can slow down the growth and/or migration of GC cells. Since targeting the hypoxic microenvironment and/or ICTs may be a promising strategy for the treatment of GC, more attention should be paid to the interplay between ICTs and the development and progression of GC in such a microenvironment.

Extracellular Acidification Induces Lysosomal Dysregulation

Many invasive cancers emerge through a years-long process of somatic evolution, characterized by an accumulation of heritable genetic and epigenetic changes and the emergence of increasingly aggressive clonal populations. In solid tumors, such as breast ductal carcinoma, the extracellular environment for cells within the nascent tumor is harsh and imposes different types of stress on cells, such as hypoxia, nutrient deprivation, and cytokine inflammation. Acidosis is a constant stressor of most cancer cells due to its production through fermentation of glucose to lactic acid in hypoxic or normoxic regions (Warburg effect). Over a short period of time, acid stress can have a profound effect on the function of lysosomes within the cells exposed to this environment, and after long term exposure, lysosomal function of the cancer cells can become completely dysregulated. Whether this dysregulation is due to an epigenetic change or evolutionary selection has yet to be determined, but understanding the mechanisms behind this dysregulation could identify therapeutic opportunities.

Large Acid-Evoked Currents, Mediated by ASIC1a, Accompany Differentiation in Human Dopaminergic Neurons

Acid-sensing ion channels (ASICs) are proton-gated Na⁺ channels. They contribute to synaptic transmission, neuronal differentiation and neurodegeneration. ASICs have been mainly characterized in neurons from mice or rats and our knowledge of their properties in human neurons is scarce. Here, we functionally characterized ASICs in differentiating LUHMES cells, a human mesencephalic cell line with characteristics of dopaminergic neurons. We find that LUHMES cells express functional ASICs, predominantly homomeric ASIC1a. Expression starts early during differentiation with a striking surge in current amplitude at days 4-6 of differentiation, a time point where-based on published data-LUHMES cells start expressing synaptic markers. Peak ASIC expression therefore coincides with a critical period of LUHMES cell differentiation. It was associated with increased excitability, but not paralleled by an increase in ASIC1 mRNA or protein. In differentiating as well as in terminally differentiated LUHMES cells, ASIC activation by slight acidification elicited large currents, action potentials and a rise in cytosolic Ca²⁺. Applying the ASIC pore blocker diminazene during differentiation reduced the length of neurites, consistent with the hypothesis that ASICs play a critical role in LUHMES cell differentiation. In summary, our study establishes LUHMES cells as a valuable model to study the role of ASICs for neuronal differentiation and potentially also cell death in a human cell line.

Ion Channels and Their Role in the Pathophysiology of Gliomas

Malignant gliomas are the most common primary central nervous system tumors and their prognosis is very poor. In recent years, ion channels have been demonstrated to play important roles in tumor pathophysiology such as regulation of gene expression, cell migration, and cell proliferation. In this review, we summarize the current knowledge on the role of ion channels on the development and progression of gliomas. Cell volume changes through the regulation of ion flux, accompanied by water flux, are essential for migration and invasion. Signaling pathways affected by ion channel activity play roles in cell survival and cell proliferation. Moreover, ion channels are involved in glioma-related seizures, sensitivity to chemotherapy, and tumor metabolism. Ion channels are potential targets for the treatment of these lethal tumors. Despite our increased understanding of the contributions of ion channels to glioma biology, this field remains poorly studied. This review summarizes the current literature on this important topic.

Histidine Residues Are Responsible for Bidirectional Effects of Zinc on Acid-Sensing Ion Channel 1a/3 Heteromeric Channels

Acid-sensing ion channel (ASIC) subunits 1a and 3 are highly expressed in central and peripheral sensory neurons, respectively. Endogenous biomolecule zinc plays a critical role in physiological and pathophysiological conditions. Here, we found that currents recorded from heterologously expressed ASIC1a/3 channels using the whole-cell patch-clamp technique were regulated by zinc with dual effects. Co-application of zinc dose-dependently potentiated both peak amplitude and the sustained component of heteromeric ASIC1a/3 currents; pretreatment with zinc between 3 to 100 µM exerted the same potentiation as co-application. However, pretreatment with zinc induced a significant inhibition of heteromeric ASIC1a/3 channels when zinc concentrations were over 250 µM. The potentiation of heteromeric ASIC1a/3 channels by zinc was pH dependent, as zinc shifted the pH dependence of ASIC1a/3 currents from a pH₅₀ of 6.54 to 6.77; whereas the inhibition of ASIC1a/3 currents by zinc was also pH dependent. Furthermore, we systematically mutated histidine residues in the extracellular domain of ASIC1a or ASIC3 and found that histidine residues 72 and 73 in both ASIC1a and ASIC3, and histidine residue 83 in the ASIC3 were responsible for bidirectional effects on heteromeric ASIC1a/3 channels by zinc. These findings suggest that histidine residues in the extracellular domain of heteromeric ASIC1a/3 channels are critical for zinc-mediated effects.

Voltage-gated ion channels mediate the electrotaxis of glioblastoma cells in a hybrid PMMA/PDMS microdevice

Transformed astrocytes in the most aggressive form cause glioblastoma, the most common cancer in the central nervous system with high mortality. The physiological electric field by neuronal local field potentials and tissue polarity may guide the infiltration of glioblastoma cells through the electrotaxis process. However, microenvironments with multiplex gradients are difficult to create. In this work, we have developed a hybrid microfluidic platform to study glioblastoma electrotaxis in controlled microenvironments with high throughput quantitative analysis by machine learning-powered single cell tracking software. By equalizing the hydrostatic pressure difference between inlets and outlets of the microchannel, uniform single cells can be seeded reliably inside the microdevice. The electrotaxis of two glioblastoma models, T98G and U-251MG, requires an optimal laminin-containing extracellular matrix and exhibits opposite directional and electro-alignment tendencies. Calcium signaling is a key contributor in glioblastoma pathophysiology but its role in glioblastoma electrotaxis is still an open question. Anodal T98G electrotaxis and cathodal U-251MG electrotaxis require the presence of extracellular calcium cations. U-251MG electrotaxis is dependent on the P/Q-type voltage-gated calcium channel (VGCC) and T98G is dependent on the R-type VGCC. U-251MG electrotaxis and T98G electrotaxis are also mediated by A-type (rapidly inactivating) voltage-gated potassium channels and acid-sensing sodium channels. The involvement of multiple ion channels suggests that the glioblastoma electrotaxis is complex and patient-specific ion channel expression can be critical to develop personalized therapeutics to fight against cancer metastasis. The hybrid microfluidic design and machine learning-powered single cell analysis provide a simple and flexible platform for quantitative investigation of complicated biological systems.

Mambalgin-2 Induces Cell Cycle Arrest and Apoptosis in Glioma Cells via Interaction with ASIC1a

Gliomas are fast growing and highly invasive brain tumors, characterized by tumor microenvironment acidification that drives glioma cell growth and migration. Channels containing Acid-sensing Ion Channel 1a subunit (ASIC1a) mediate amiloride-sensitive cation influx in late stage glioma cells, but not in normal astrocytes. Thus, selective targeting of ASIC1a can be a perspective strategy for glioma treatment. Here, ASIC1a expression in U251 MG and A172 glioma cells, but not in normal astrocytes, was demonstrated. Recombinant analog of mambalgin-2 from black mamba Dendroaspis polylepis inhibited amiloride-sensitive currents at ASIC1a both in Xenopus laevis oocytes and in U251 MG cells, while its mutants with impaired activity towards this channel did not. Mambalgin-2 inhibited U251 MG and A172 glioma cells growth with EC50 in the nanomolar range without affecting the proliferation of normal astrocytes. Notably, mambalgin-2 mutants did not affect glioma cell proliferation, pointing on ASIC1a as the main molecular target of mambalgin-2 in U251 MG and A172 cells. Mambalgin-2 induced a cell cycle arrest, inhibited Cyclin D1 and cyclin-dependent kinases (CDK) phosphorylation and caused apoptosis in U251 MG and A172 cells. Moreover, mambalgin-2 inhibited the growth of low-passage primary cells from a patient with glioblastoma. Altogether, our data point to mambalgin-2 as a useful hit for the development of new drugs for glioma treatment.

An eight-mRNA signature outperforms the lncRNA-based signature in predicting prognosis of patients with glioblastoma

BACKGROUND

The prognosis of the glioblastoma (GBM) is dismal. This study aims to select an optimal RNA signature for prognostic prediction of GBM patients.

METHODS

For the training set, the long non-coding RNA (lncRNA) and mRNA expression profiles of 151 patients were downloaded from the TCGA. Differentially expressed mRNAs (DEGs) and lncRNAs (DE-lncRNAs) were identified between good prognosis and bad prognosis patients. Optimal prognostic mRNAs and lncRNAs were selected respectively, by using univariate Cox proportional-hazards (PH) regression model and LASSO Cox-PH model. Subsequently, four prognostic scoring models were built based on expression levels or expression status of the selected prognostic lncRNAs or mRNAs, separately. Each prognostic model was applied to the training set and an independent validation set. Function analysis was used to uncover the biological roles of these prognostic DEGs between different risk groups classified by the mRNA-based signature.

RESULTS

We obtained 261 DEGs and 33 DE-lncRNAs between good prognosis and bad prognosis patients. A panel of eight mRNAs and a combination of ten lncRNAs were determined as predictive RNAs by LASSO Cox-PH model. Among the four prognostic scoring models using the eight-mRNA signature or the ten-lncRNA signature, the one based on the expression levels of the eight mRNAs showed the greatest predictive power. The DEGs between different risk groups using the eight prognostic mRNAs were functionally involved in calcium signaling pathway, neuroactive ligand-receptor interaction pathway, and Wnt signaling pathway.

CONCLUSION

The eight-mRNA signature has greater prognostic value than the ten-lncRNA-based signature for GBM patients based on bioinformatics analysis.

Proton-sensing G protein-coupled receptors: detectors of tumor acidosis and candidate drug targets

Cells in tumor microenvironments (TMEs) use several mechanisms to sense their low pH (<7.0), including via proton-sensing G protein-coupled receptors (psGPCRs): GPR4, GPR65/TDAG8, GPR68/OGR1 and GPR132/G2A. Numerous cancers have increased expression of psGPCRs. The psGPCRs may contribute to features of the malignant phenotype via actions on specific cell-types in the TME and thereby promote tumor survival and growth. Here, we review data regarding psGPCR expression in tumors and cancer cells, impact of psGPCRs on survival in solid tumors and a bioinformatics approach to infer psGPCR expression in cell types in the TME. New tools are needed to help define contributions of psGPCRs in tumor biology and to identify potentially novel therapeutic agents for a variety of cancers.

The Acidic Tumor Microenvironment as a Driver of Cancer

Acidic metabolic waste products accumulate in the tumor microenvironment because of high metabolic activity and insufficient perfusion. In tumors, the acidity of the interstitial space and the relatively well-maintained intracellular pH influence cancer and stromal cell function, their mutual interplay, and their interactions with the extracellular matrix. Tumor pH is spatially and temporally heterogeneous, and the fitness advantage of cancer cells adapted to extracellular acidity is likely particularly evident when they encounter less acidic tumor regions, for instance, during invasion. Through complex effects on genetic stability, epigenetics, cellular metabolism, proliferation, and survival, the compartmentalized pH microenvironment favors cancer development. Cellular selection exacerbates the malignant phenotype, which is further enhanced by acid-induced cell motility, extracellular matrix degradation, attenuated immune responses, and modified cellular and intercellular signaling. In this review, we discuss how the acidity of the tumor microenvironment influences each stage in cancer development, from dysplasia to full-blown metastatic disease.

PI3-kinase/Akt pathway-regulated membrane transportation of acid-sensing ion channel 1a/Calcium ion influx/endoplasmic reticulum stress activation on PDGF-induced HSC Activation

Acid-sensing ion channel 1a (ASIC1a) allows Na⁺ and Ca²⁺ flow into cells. It is expressed during inflammation, in tumour and ischaemic tissue, in the central nervous system and non-neuronal injury environments. Endoplasmic reticulum stress (ERS) is caused by the accumulation of misfolded proteins that interferes with intracellular calcium homoeostasis. Our recent reports showed ASIC1a and ERS are involved in liver fibrosis progression, particularly in hepatic stellate cell (HSC) activation. In this study, we investigated the roles of ASIC1a and ERS in activated HSC. We found that ASIC1a and ERS-related proteins were up-regulated in carbon tetrachloride (CCl₄ )-induced fibrotic mouse liver tissues, and in patient liver tissues with hepatocellular carcinoma with severe liver fibrosis. The results show silencing ASIC1a reduced the expression of ERS-related biomarkers GRP78, Caspase12 and IREI-XBP1. And, ERS inhibition by 4-PBA down-regulated the high expression of ASIC1a induced by PDGF, suggesting an interactive relationship. In PDGF-induced HSCs, ASIC1a was activated and migrated to the cell membrane, leading to extracellular calcium influx and ERS, which was mediated by PI3K/AKT pathway. Our work shows PDGF-activated ASIC1a via the PI3K/AKT pathway, induced ERS and promoted liver fibrosis progression.

The Conorfamide RPRFa Stabilizes the Open Conformation of Acid-Sensing Ion Channel 3 via the Nonproton Ligand-Sensing Domain

Acid-sensing ion channel 3 (ASIC3) is a proton-gated Na+ channel with important roles in pain. ASIC3 quickly desensitizes in less than a second, limiting its capacity to sense sustained acidosis during pain. RFamide neuropeptides are modulators of ASIC3 that slow its desensitization and induce a variable sustained current. The molecular mechanism of slowed desensitization and the RFamide binding site on ASIC3 are unknown. RPRFamide, a RFamide from the venom of a cone snail, has a comparatively high affinity for ASIC3 and strongly slows its desensitization. Here we show that covalent binding of a UV-sensitive RPRFamide variant to ASIC3 prevents desensitization, suggesting that RPRFamide has to unbind from ASIC3 before it can desensitize. Moreover, we show by in silico docking to a homology model of ASIC3 that a cavity in the lower palm domain, which is also known as the nonproton ligand-sensing domain, is a potential binding site of RPRFamide. Finally, using extensive mutagenesis of residues lining the nonproton ligand-sensing domain, we confirm that this domain is essential for RPRFamide modulation of ASIC3. As comparative analysis of ASIC crystal structures in the open and in the desensitized conformation suggests that the lower palm domain contracts during desensitization, our results collectively suggest that RPRFamide, and probably also other RFamide neuropeptides, bind to the nonproton ligand-sensing domain to stabilize the open conformation of ASIC3.

Novel insights into ion channels in cancer stem cells (Review)

Cancer stem cells (CSCs) are immortal cells in tumor tissues that have been proposed as the driving force of tumorigenesis and tumor invasion. Previously, ion channels were revealed to contribute to cancer cell proliferation, migration and apoptosis. Recent studies have demonstrated that ion channels are present in various CSCs; however, the functions of ion channels and their mechanisms in CSCs remain unknown. The present review aimed to focus on the roles of ion channels in the regulation of CSC behavior and the CSC-like properties of cancer cells. Evaluation of the relationship between ion channels and CSCs is critically important for understanding malignancy.

Novel amidrazone derivatives: Design, synthesis and activity evaluation

A series of new 6-styryl-naphthalene-2-amidrazone derivatives were synthesized and evaluated as potential ASIC1a inhibitors. Among them, compound 5e showed the most activity to inhibit [Ca²⁺]_i. elevation in acid-induced articular chondrocytes. Together with the important role of ASIC1a in the pathogenesis of tissue acidification diseases including rheumatoid arthritis, these results might provide a meaningful hint or inspiration in developing drugs targeting at tissue acidification diseases.

Therapeutic Monoclonal Antibodies Delivery for the Glioblastoma Treatment

Glioblastoma multiforme (GBM) is the most common and challenging primary malignant brain tumor, being the median overall survival between 10 and 14 months due to its invasive characteristics. GBM treatment is mainly based on the maximal surgical resection and radiotherapy associated to chemotherapy. Monoclonal antibodies (mAbs) have been used in chemotherapy protocols for GBM treatment in order to improve immunotherapy and antiangiogenic processes. High specificity and affinity of mAbs for biological targets make them highly used for brain tumor therapy. Specifically, antiangiogenic mAbs have been wisely indicated in chemotherapy protocols because GBM is the most vascularized tumors in humans with high expression of cytokines. However, mAb-based therapy is not that effective due to the aggressive spread of the tumor associated to the difficulty in the access of mAb into the brain (due to the blood-brain barrier). For that reason, nanobiotechnology has played an important role in the treatment of several tumors, mainly in the tumors of difficult access, such as GBM. In this chapter will be discussed strategies related with nanobiotechnology applied to the mAb delivery and how these therapeutics can improve the GBM treatment and life quality of the patient.

TFCP2/TFCP2L1/UBP1 transcription factors in cancer

The TFCP2/Grainyhead family of transcription factors is divided into two distinct subfamilies, one of which includes the Grainyhead-like 1-3 (GRHL1-3) proteins and the other consists of TFCP2 (synonyms: CP2, LSF, LBP-1c), TFCP2L1 (synonyms: CRTR-1, LBP-9) and UBP1 (synonyms: LBP-1a, NF2d9). Transcription factors from the TFCP2/TFCP2L1/UBP1 subfamily are involved in various aspects of cancer development. TFCP2 is a pro-oncogenic factor in hepatocellular carcinoma, pancreatic cancer and breast cancer, may be important in cervical carcinogenesis and in colorectal cancer. TFCP2 can also act as a tumor suppressor, for example, it inhibits melanoma growth. Furthermore, TFCP2 is involved in epithelial-mesenchymal transition and enhances angiogenesis. TFCP2L1 maintains pluripotency and self-renewal of embryonic stem cells and was implicated in a wide variety of cancers, including clear cell renal cell carcinoma, breast cancer and thyroid cancer. Here we present a systematic review of current knowledge of this protein subfamily in the context of cancer. We also discuss potential challenges in investigating this family of transcription factors. These challenges include redundancies between these factors as well as their interactions with each other and their ability to modulate each other's activity.