Suppression of CLC-3 chloride channel reduces the aggressiveness of glioma through inhibiting nuclear factor-κB pathway

Diagnostic and Therapeutic Approaches for Glioblastoma and Neuroblastoma Cancers Using Chlorotoxin Nanoparticles

Glioblastoma multiforme (GB) and high-risk neuroblastoma (NB) are known to have poor therapeutic outcomes. As for most cancers, chemotherapy and radiotherapy are the current mainstay treatments for GB and NB. However, the known limitations of systemic toxicity, drug resistance, poor targeted delivery, and inability to access the blood-brain barrier (BBB), make these treatments less satisfactory. Other treatment options have been investigated in many studies in the literature, especially nutraceutical and naturopathic products, most of which have also been reported to be poorly effective against these cancer types. This necessitates the development of treatment strategies with the potential to cross the BBB and specifically target cancer cells. Compounds that target the endopeptidase, matrix metalloproteinase 2 (MMP-2), have been reported to offer therapeutic insights for GB and NB since MMP-2 is known to be over-expressed in these cancers and plays significant roles in such physiological processes as angiogenesis, metastasis, and cellular invasion. Chlorotoxin (CTX) is a promising 36-amino acid peptide isolated from the venom of the deathstalker scorpion, Leiurus quinquestriatus, demonstrating high selectivity and binding affinity to a broad-spectrum of cancers, especially GB and NB through specific molecular targets, including MMP-2. The favorable characteristics of nanoparticles (NPs) such as their small sizes, large surface area for active targeting, BBB permeability, etc. make CTX-functionalized NPs (CTX-NPs) promising diagnostic and therapeutic applications for addressing the many challenges associated with these cancers. CTX-NPs may function by improving diffusion through the BBB, enabling increased localization of chemotherapeutic and genotherapeutic drugs to diseased cells specifically, enhancing imaging modalities such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), optical imaging techniques, image-guided surgery, as well as improving the sensitization of radio-resistant cells to radiotherapy treatment. This review discusses the characteristics of GB and NB cancers, related treatment challenges as well as the potential of CTX and its functionalized NP formulations as targeting systems for diagnostic, therapeutic, and theranostic purposes. It also provides insights into the potential mechanisms through which CTX crosses the BBB to bind cancer cells and provides suggestions for the development and application of novel CTX-based formulations for the diagnosis and treatment of GB and NB in the future.

Circular RNA XRCC5 aggravates glioma progression by activating CLC3/SGK1 axis via recruiting IGF2BP2

BACKGROUND

Increasing evidences have reported the critical roles of circular RNA (circRNA) in gliomas. Whereas, the role of circXRCC5 in glioma and its underlying molecular mechanism has not been reported.

METHODS

The RNA transcripts and protein levels were detected using qRT-PCR, immunohistochemistry (IHC) and in situ hybridization (ISH) assays. Cell proliferation was characterized by CCK-8 and clone formation assays. The formation of NLRP3-inflammasomes was identified using immunofluorescence (IF) and Western blot assays. The cytokines were determined using immunosorbent assay (ELISA) and Western blot assays. The molecular interactions were validated using RIP and pull-down assays.

RESULTS

circXRCC5 was over-expressed in glioma and positively related to the shorter survival rate, advanced TNM stage and larger tumor volume. circXRCC5 knockdown inhibited cell proliferation and NLRP3-mediated inflammasome activation of glioma cells. Subsequently, we found that circXRCC5 maintained mRNA stability of CLC3 by binding to IGF2BP2. Furthermore, CLC3 accelerated SGK1 expression via PI3K/PDK1/AKT pathway. The rescue experiments showed that both overexpression of CLC3 or SGK1 dramatically alleviated circXRCC5 knockdown-induced inhibition of cell proliferation and NLRP3-mediated inflammasome activation of glioma cells. In vivo, our study proved that circXRCC5 accelerated glioma growth by regulating CLC3/SGK1 axis.

CONCLUSION

Our data concluded that circXRCC5 formed a complex with IGF2BP2 to regulate inflammasome activation and tumor growth via CLC3/SGK1 axis.

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.

Ion channels as a therapeutic target for renal fibrosis

Renal ion channel transport and electrolyte disturbances play an important role in the process of functional impairment and fibrosis in the kidney. It is well known that there are limited effective drugs for the treatment of renal fibrosis, and since a large number of ion channels are involved in the renal fibrosis process, understanding the mechanisms of ion channel transport and the complex network of signaling cascades between them is essential to identify potential therapeutic approaches to slow down renal fibrosis. This review summarizes the current work of ion channels in renal fibrosis. We pay close attention to the effect of cystic fibrosis transmembrane conductance regulator (CFTR), transmembrane Member 16A (TMEM16A) and other Cl− channel mediated signaling pathways and ion concentrations on fibrosis, as well as the various complex mechanisms for the action of Ca2+ handling channels including Ca2+-release-activated Ca2+ channel (CRAC), purinergic receptor, and transient receptor potential (TRP) channels. Furthermore, we also focus on the contribution of Na+ transport such as epithelial sodium channel (ENaC), Na+, K+-ATPase, Na+-H+ exchangers, and K+ channels like Ca2+-activated K+ channels, voltage-dependent K+ channel, ATP-sensitive K+ channels on renal fibrosis. Proposed potential therapeutic approaches through further dissection of these mechanisms may provide new therapeutic opportunities to reduce the burden of chronic kidney disease.

Bioactive peptides from venoms against glioma progression

Venoms are complex mixtures of different molecules and ions. Among them, bioactive peptides have been found to affect cancer hallmarks, such as cell proliferation, cell invasion, cell migration, and can also modulate the immune response of normal and cancer-bearing organisms. In this article, we review the mechanisms of action on these cancer cell features, focusing on bioactive peptides being developed as potential therapeutics for one of the most aggressive and deadly brain tumors, glioblastoma (GB). Novel therapeutic approaches applying bioactive peptides may contribute to multiple targeting of GB and particularly of GB stem cells. Bioactive peptides selectively target cancer cells without harming normal cells. Various molecular targets related to the effects of bioactive peptides on GB have been proposed, including ion channels, integrins, membrane phospholipids and even immunomodulatory treatment of GB. In addition to therapy, some bioactive peptides, such as disintegrins, can also be used for diagnostics or are used as labels for cytotoxic drugs to specifically target cancer cells. Given the limitations described in the last section, successful application in cancer therapy is rather low, as only 3.4% of such peptides have been included in clinical trials and have passed successfully phases I to III. Combined approaches of added bioactive peptides to standard cancer therapies need to be explored using advanced GB in vitro models such as organoids. On the other hand, new methods are also being developed to improve translation from research to practice and provide new hope for GB patients and their families.

Targeted delivery of irinotecan and SLP2 shRNA with GRP-conjugated magnetic graphene oxide for glioblastoma treatment

Magnetic nanoparticles (MNPs) are useful for magnetic targeted drug delivery while ligand-mediated active targeting is another common delivery strategy for cancer therapy. In this work, we intend to prepare magnetic graphene oxide (mGO) by chemical co-precipitation of MNPs on the GO surface, followed by conjugation of the gastrin releasing peptide (GRP) as a targeting ligand, for dual targeted drug/gene delivery in invasive brain glioma treatment. mGO was grafted with chitosan, complexed with shRNA plasmid DNA for stomatin-like protein 2 (SLP2) gene silencing, modified with urocanic acid for plasmid DNA endosomal escape, PEGylated for GRP conjugation, and loaded with the chemotherapeutic drug irinotecan (CPT-11) by π-π interaction for pH-responsive drug release (mGOCUG/CPT-11/shRNA). In addition to the in depth characterization of the physico-chemical and biological properties during each preparation step, we also study the loading/pH-responsive release behavior of CPT-11 and the shRNA plasmid loading/cell transfection efficiency. The targeting and antitumor efficacies of the nanocomposite were studied with U87 human glioblastoma cells in vitro. An in vivo study revealed that intravenous administration followed by magnetic guidance results in the efficient targeted delivery of mGOCUG/CPT-11/shRNA to orthotopic brain tumors in nude mice, and it exhibits excellent antitumor efficacy with a reduced tumor growth rate and prolonged animal survival time. Our work thus highlights a multifunctional mGO-based drug/gene delivery platform for effective combination cancer therapy in glioblastoma treatment.

Chloride Channel and Inflammation-Mediated Pathogenesis of Osteoarthritis

Articular cartilage allows the human body to buffer and absorb stress during normal exercise. It is mainly composed of cartilage cells and the extracellular matrix and is surrounded by the extracellular microenvironment formed by synovial fluid and various factors in it. Studies have shown that chondrocytes are the metabolic center of articular cartilage. Under physiological conditions, the extracellular matrix is in a dynamic balance of anabolism and catabolism, and various factors and physical and chemical conditions in the extracellular microenvironment are also in a steady state. This homeostasis depends on the normal function of proteins represented by various ion channels on chondrocytes. In mammalian chondrocyte species, ion channels are mainly divided into two categories: cation channels and anion channels. Anion channels such as chloride channels have become hot research topics in recent years. These channels play an extremely important role in various physiological processes. Recently, a growing body of evidence has shown that many pathological processes, abnormal concentration of mechanical stress and chloride channel dysfunction in articular cartilage lead to microenvironment disorders, matrix and bone metabolism imbalances, which cause partial aseptic inflammation. These pathological processes initiate extracellular matrix degradation, abnormal chondrocyte death, hyperplasia of inflammatory synovium and bony. Osteoarthritis (OA) is a common clinical disease in orthopedics. Its typical manifestations are joint inflammation and pain caused by articular cartilage degeneration, but its pathogenesis has not been fully elucidated. Focusing on the physiological functions and pathological changes of chloride channels and pathophysiology of aseptic inflammation furthers the understanding of OA pathogenesis and provides possible targets for subsequent medication development.

ClC-c regulates the proliferation of intestinal stem cells via the EGFR signalling pathway in Drosophila

Objectives

Adult stem cells uphold a delicate balance between quiescent and active states, which is crucial for tissue homeostasis. Whereas many signalling pathways that regulate epithelial stem cells have been reported, many regulators remain unidentified.

Materials and Methods

Flies were used to generate tissue‐specific gene knockdown and gene knockout. qRT‐PCR was used to assess the relative mRNA levels. Immunofluorescence was used to determine protein localization and expression patterns. Clonal analyses were used to observe the phenotype. RNA‐seq was used to screen downstream mechanisms.

Results

Here, we report a member of the chloride channel family, ClC‐c, which is specifically expressed in Drosophila intestinal stem/progenitor cells and regulates intestinal stem cell (ISC) proliferation under physiological conditions and upon tissue damage. Mechanistically, we found that the ISC loss induced by the depletion of ClC‐c in intestinal stem/progenitor cells is due to inhibition of the EGFR signalling pathway.

Conclusion

Our findings reveal an ISC‐specific function of ClC‐c in regulating stem cell maintenance and proliferation, thereby providing new insights into the functional links among the chloride channel family, ISC proliferation and tissue homeostasis.

Anticancer Mechanisms of Bioactive Peptides

Despite technological advancement, there is no 100% effective treatment against metastatic cancer. Increasing resistance of cancer cells towards chemotherapeutic drugs along with detrimental side effects remained a concern. Thus, the urgency in developing new anticancer agents has been raised. Anticancer peptides have been proven to display potent activity against a wide variety of cancer cells. Several mode of actions describing their cytostatic and cytotoxic effect on cancer cells have been proposed which involves cell surface binding leading to membranolysis or internalization to reach their intracellular target. Understanding the mechanism of action of these anticancer peptides is important in achieving full therapeutic success. In the present article, we discuss the anticancer action of peptides accompanied by the mechanisms underpinning their toxicity to cancer cells.

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.

Injectable Thermo-Sensitive Chitosan Hydrogel Containing CPT-11-Loaded EGFR-Targeted Graphene Oxide and SLP2 shRNA for Localized Drug/Gene Delivery in Glioblastoma Therapy

In this study, we aimed to develop a multifunctional drug/gene delivery system for the treatment of glioblastoma multiforme by combining the ligand-mediated active targeting and the pH-triggered drug release features of graphene oxide (GO). Toward this end, we load irinotecan (CPT-11) to cetuximab (CET)-conjugated GO (GO-CET/CPT11) for pH-responsive drug release after endocytosis by epidermal growth factor receptor (EGFR) over-expressed U87 human glioblastoma cells. The ultimate injectable drug/gene delivery system was designed by co-entrapping stomatin-like protein 2 (SLP2) short hairpin RNA (shRNA) and GO-CET/CPT11 in thermosensitive chitosan-g-poly(N-isopropylacrylamide) (CPN) polymer solution, which offers a hydrogel depot for localized, sustained delivery of the therapeutics after the in situ formation of CPN@GO-CET/CPT11@shRNA hydrogel. An optimal drug formulation was achieved by considering both the loading efficiency and loading content of CPT-11 on GO-CET. A sustained and controlled release behavior was found for CPT-11 and shRNA from CPN hydrogel. Confocal microscopy analysis confirmed the intracellular trafficking for the targeted delivery of CPT-11 through interactions of CET with EGFR on the U87 cell surface. The efficient transfection of U87 using SLP2 shRNA was achieved using CPN as a delivery milieu, possibly by the formation of shRNA/CPN polyplex after hydrogel degradation. In vitro cell culture experiments confirmed cell apoptosis induced by CPT-11 released from acid organelles in the cytoplasm by flow cytometry, as well as reduced SLP2 protein expression and inhibited cell migration due to gene silencing. Finally, in vivo therapeutic efficacy was demonstrated using the xenograft of U87 tumor-bearing nude mice through non-invasive intratumoral delivery of CPN@GO-CET/CPT11@shRNA by injection. Overall, we have demonstrated the novelty of this thermosensitive hydrogel to be an excellent depot for the co-delivery of anticancer drugs and siRNA. The in situ forming hydrogel will not only provide extended drug release but also combine the advantages offered by the chitosan-based copolymer structure for siRNA delivery to broaden treatment modalities in cancer therapy.

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Gene Suppression of the Chloride Channel 2 Suppressed TGF-β1-Induced Proliferation, Collagen Synthesis, and Collagen Gel Contraction Mediated by Conjunctival Fibroblasts

BACKGROUND

Excessive scarring of filtering blebs is the main cause of surgical failure in glaucoma. Previous studies have highlighted the role of chloride channels (ClCs) in scar formation, whereas the role of ClCs in scarring of filtering blebs has not been studied.

OBJECTIVES

The objective of this study was to investigate the effects of the chloride channel 2 (ClC-2) on scar formation of filtering blebs after glaucoma filtering surgery.

METHODS

ClC-2 siRNA-transfected human conjunctival fibroblasts (HConFs) were cultured in type 1 collagen gels in the presence of transforming growth factor (TGF)-β1. Collagen gel contraction was evaluated based on the gel area. 3D-cultured HConFs were treated with the ClC blocker NPPB in the presence of TGF-β1, and cell proliferation collagen synthesis and contractility were measured. The expression levels of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in HConFs were assessed by Western blotting and qPCR.

RESULTS

TGF-β1 induced cell proliferation, cell cycle progression, collagen synthesis, and collagen gel contraction in HConFs. TGF-β1 increased MMP-2 and MMP-9 levels but inhibited the expression of TIMPs. NPPB and ClC-2 siRNA transfection inhibited TGF-β2-induced cell proliferation, cell cycle progression, collagen synthesis, and collagen gel contraction, mediated by HConFs. TGF-β2-induced increases in MMP-2 and MMP-9 were also inhibited by NPPB and ClC-2 siRNA transfection, but TIMP expression was increased by NPPB and ClC-2 siRNA transfection.

CONCLUSIONS

These findings demonstrate that ClC-2 ClCs modulate TGF-β1-induced cell proliferation, collagen synthesis, and collagen gel contraction of HConFs by attenuating MMP-2 and MMP-9 production and by stimulating TIMP1 production. NPPB may therefore prove to be of clinical value for the inhibition of scar formation of filtering blebs.

Various Nucleolar Stress Inducers Result in Highly Distinct Changes in Water, Dry Mass and Elemental Content in Cancerous Cell Compartments: Investigation Using a Nano-Analytical Approach

Rationale: Numerous chemotherapeutic drugs that affect ribosome biogenesis in the nucleolus induce nucleolar stress. Improving our understanding of the effects of these drugs will require uncovering and comparing their impact on several biophysical parameters of the major cell compartments. Here, we quantified the water content and dry mass of cancerous cells treated with CX-5461, DRB or DAM to calculate macromolecular crowding and the volume occupied by free water, as well as elemental content. Methods: HeLa-H2B-GFP cells were treated with CX-5461, DRB or DAM. Water content and dry mass were measured in numerous regions of interest of ultrathin cryo-sections by quantitative scanning transmission electron microscope dark-field imaging and the elements quantified by energy dispersive X-ray spectrometry. The data were used to calculate macromolecular crowding and the volume occupied by free water in all cell compartments of control and treated cells. Hydrophobic and unfolded proteins were revealed by 8-Anilinonaphtalene-1-sulfonic acid (ANS) staining and imaging by two-photon microscopy. Immunolabeling of UBF, pNBS1 and pNF-κB was carried out and the images acquired with a confocal microscope for 3D imaging to address whether the localization of these proteins changes in treated cells. Results: Treatment with CX-5461, DRB or DAM induced completely different changes in macromolecular crowding and elemental content. Macromolecular crowding and elemental content were much higher in CX-5461-treated, moderately higher in DRB-treated, and much lower in DAM-treated cells than control cells. None of the drugs alone induced nucleolar ANS staining but it was induced by heat-shock of control cells and cells previously treated with DAM. UBF and pNBS1 were systematically co-localized in the nucleolus of CX-5461- and DAM-treated cells. pNF-κB only localized to the nucleolar caps of pre-apoptotic DAM-treated cells. Conclusion: We directly quantified water and ion content in cell compartments using cryo-correlative electron microscopy. We show that different chemotherapeutic nucleolar stress inducers result in distinctive, thus far-unrecognized changes in macromolecular crowding and elemental content which are known to modify cell metabolism. Moreover we were able to correlate these changes to the sensitivity of treated cells to heat-shock and the behavior of nucleolar pNBS1 and pNF-κB.

Chloride channel 3 (CIC-3) predicts the tumor size in hepatocarcinoma

Chloride channel 3 (CIC-3) has been suggested to be implicated in the carcinogenesis though; it still remains ill understood in hepatocarcinoma, especially in terms of clinicopathological meaning of its expression. Given this, herein, to understand the clinicopathological significance of CIC-3 expression in hepatocarcinoma, Immunohistochemistry was performed to examine the level of CIC-3, followed by statistical analysis of the correlation between expression versus clinicopathological variables, including gender, age, TNM classifications, tumor size, lymph node metastasis and overall prognosis. It was shown that positive staining of CIC-3 can be present in both hepatocarcinoma and its paired normal controls; and that CIC-3 was significantly over-expressed in hepatcarcioma on the whole relative to paired normal controls. Moreover, up-regulation of CIC-3 markedly correlated with tumor size and overall prognosis, suggesting that CIC-3 expression could predict both tumor size and overall prognosis in hepatocarcinoma.

Dexamethasone in Glioblastoma Multiforme Therapy: Mechanisms and Controversies

Glioblastoma multiforme (GBM) is the most common and malignant of the glial tumors. The world-wide estimates of new cases and deaths annually are remarkable, making GBM a crucial public health issue. Despite the combination of radical surgery, radio and chemotherapy prognosis is extremely poor (median survival is approximately 1 year). Thus, current therapeutic interventions are highly unsatisfactory. For many years, GBM-induced brain oedema and inflammation have been widely treated with dexamethasone (DEX), a synthetic glucocorticoid (GC). A number of studies have reported that DEX also inhibits GBM cell proliferation and migration. Nevertheless, recent controversial results provided by different laboratories have challenged the widely accepted dogma concerning DEX therapy for GBM. Here, we have reviewed the main clinical features and genetic and epigenetic abnormalities underlying GBM. Finally, we analyzed current notions and concerns related to DEX effects on cerebral oedema, cancer cell proliferation and migration and clinical outcome.

Chloride channel-3 is required for efficient tumour cell migration and invasion in human cervical squamous cell carcinoma

OBJECTIVE

Chloride channel-3 (ClC-3) plays significant roles in various physiological and physiopathological activities, including cell migration and invasion ability. The purpose of this study was to evaluate whether ClC-3 influences the migration and invasion of cervical squamous cell carcinoma cells and its possible mechanisms.

METHODS

Paraffin-embedded cervical tissues, including normal cervical tissues, cervical squamous cell carcinoma (SCC) and homologous paracancerous tissues, were collected. The cervical squamous cell carcinoma and matched paracarcinoma fresh tissues specimens were collected from 49 patients with SCC, and the normal cervical tissues were collected from 45 non-cervical squamous cell carcinoma patients. The human cervical squamous carcinoma cell line SiHa was cultured. ClC-3 expression was assessed by real-time RT-PCR, immunohistochemistry and Western blot, and the expression of phospho-PI3K/Akt/mTOR and matrix metalloproteinase-9 (MMP-9) was detected by Western blot. Small interfering RNA (siRNA) technology was used to knockdown ClC-3 expression. SiHa cell migration and invasion ability were measured using Transwell assays with or without Matrigel-coated membranes.

RESULTS

ClC-3 mRNA and protein expression in SCC tissues from cervical squamous cell carcinoma patients was significantly upregulated, and no significant difference was noted between the matched paracarcinoma fresh tissue from the same patients and non-cervical cancer patients. SiHa cell migration and invasion and phospho-PI3K/Akt/mTOR and MMP-9 expression were attenuated by knocking down ClC-3 expression using ClC-3 siRNA.

CONCLUSIONS

ClC-3 participates in the processes of SCC cell migration and invasion and regulates MMP-9 expression via the PI3K/Akt/mTOR signaling pathway.

Overexpression of chloride channel-3 (ClC-3) is associated with human cervical carcinoma development and prognosis

Background

Cervical carcinoma is a major gynecological cancer and causes cancer-related deaths in worldwide, the latent pathogenesis and progress of cervical cancer is still under research. ClC-3 may be an important promoter for aggressive metastasis of malignant tumors. In this research, we explore the ClC-3 expression in cervical carcinoma and its underlying clinical significance, trying to illuminate ClC-3 probable function in the neoplasm malignant behavior, development and prognosis.

Methods

Paraffin-embedded cervical (n = 168) and lymph node (n = 100) tissue specimens were analysed by immunohistochemistry. Fresh human cervical tissue specimens (n = 165) and four human cervical cell lines were tested for ClC-3 mRNA and protein expression levels by quantitative real-time PCR and western blotting. The relationship between the expression levels of ClC-3, the pathological characteristics of the carcinoma, and the clinical prognosis were statistically analysed.

Results

In normal and precancerous (LSIL, HSIL) cervical tissues as well as cervical carcinoma tissues, both ClC-3 mRNA and protein expression levels increased significantly (p < 0.05). The expression level of ClC-3 was closely-related to the histological differentiation (p = 0.029), tumour staging (p = 0.016), tumour size (p = 0.039), vascular invasion (p = 0.045), interstitial infiltration depth (p = 0.012), lymphatic metastasis (p = 0.036), and HPV infection (p = 0.022). In an in vitro experiment, ClC-3 mRNA and protein were found to be overexpressed both in the HeLa and SiHa cell lines, but low expression levels were detected in the C-33A and H8 cell lines (p < 0.05). Furthermore, the high expression levels of ClC-3 was significantly correlated to poor survival in cervical carcinoma patients (Log-rank test, p = 0.046).

Conclusions

These data suggest that overexpression of ClC-3 is closely associated with human cervical carcinoma progression and poor prognosis; this suggests that ClC-3 may function as a patent tumour biomarker and a latent therapeutic target for cervical carcinoma patients.

Chloride channel-3 mediates multidrug resistance of cancer by upregulating P-glycoprotein expression

Chloride channel-3 (ClC-3), a member of the ClC family of voltage-gated Cl^- channels, is involved in the resistance of tumor cells to chemotherapeutic drugs. Here, we report a new mechanism for ClC-3 in mediating multidrug resistance (MDR). ClC-3 was highly expressed in the P-glycoprotein (P-gp)-dependent human lung adenocarcinoma cell line (A549)/paclitaxel (PTX) and the human breast carcinoma cell line (MCF-7)/doxorubicin (DOX) resistant cells. Changes in the ClC-3 expression resulted in the development of drug resistance in formerly drug-sensitive A549 or MCF-7 cells, and drug sensitivity in formerly drug-resistant A549/Taxol and MCF-7/DOX cells. Double transgenic MMTV-PyMT/CLCN3 mice with spontaneous mammary cancer and ClC-3 overexpression demonstrated drug resistance to PTX and DOX. ClC-3 expression upregulated the expression of MDR1 messenger RNA and P-gp by activating the nuclear factor-κB (NF-κB)-signaling pathway. These data suggest that ClC-3 expression in cancer cells induces MDR by upregulating NF-κB-signaling-dependent P-gp expression involving another new mechanism for ClC-3 in the development of drug resistance of cancers.

CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease

CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.

Molecular Determinants of Malignant Brain Cancers: From Intracellular Alterations to Invasion Mediated by Extracellular Vesicles

Malignant glioma cells invade the surrounding brain parenchyma, by migrating along the blood vessels, thus promoting cancer growth. The biological bases of these activities are grounded in profound alterations of the metabolism and the structural organization of the cells, which consequently acquire the ability to modify the surrounding microenvironment, by altering the extracellular matrix and affecting the properties of the other cells present in the brain, such as normal glial-, endothelial- and immune-cells. Most of the effects on the surrounding environment are probably exerted through the release of a variety of extracellular vesicles (EVs), which contain many different classes of molecules, from genetic material to defined species of lipids and enzymes. EV-associated molecules can be either released into the extracellular matrix (ECM) and/or transferred to neighboring cells: as a consequence, both deep modifications of the recipient cell phenotype and digestion of ECM components are obtained, thus causing cancer propagation, as well as a general brain dysfunction. In this review, we first analyze the main intracellular and extracellular transformations required for glioma cell invasion into the brain parenchyma; then we discuss how these events may be attributed, at least in part, to EVs that, like the pawns of a dramatic chess game with cancer, open the way to the tumor cells themselves.