LRRC8A Expression Influences Growth of Esophageal Squamous Cell Carcinoma

Ferula sesquiterpenes, ferutinin, galbanic acid and karatavic acid, suppress thymocyte volume regulation and proliferation by blocking the volume-sensitive anion channel

BACKGROUND

T cell development and maturation requires efficient cell volume regulation (CVR) system. Although the molecular basis of CVR is being rapidly elucidated, pharmacology of its key components remains poorly developed. Biopharmaceuticals specifically targeting CVR and its central player, the volume-sensitive outwardly rectifying anion channel (VSOR/VRAC), are necessary to uncover relationships between the channel, CVR and cell proliferation and survival.

METHODS

The effects of three Ferula sesquiterpenes, ferutinin, galbanic acid and karatavic acid on the regulatory volume decrease (RVD) of freshly isolated thymocytes by light transmittance, on proliferation of primary cultured thymocytes by cell counting and on the VSOR/VRAC by patch-clamp were evaluated.

RESULTS

Ferutinin, galbanic acid and karatavic acid exerted a profound inhibitory effect on RVD of thymocytes, leading to proliferation arrest. All three sesquiterpenes blocked VSOR/VRAC in a voltage-independent "cork-in-bottle" manner with half-maximal efficiencies comparable to those for RVD. Hill coefficients of 2.0-3.3 imply that positively cooperated binding of 2-3 molecules of the Ferula sesquiterpenes to VSOR/VRAC is required to suppress cell proliferation via inhibition of CVR. The Ferula sesquiterpenes were not apoptogenic, but induced necrotic cell death, which was pronounced for ferutinin and less manifested for galbanic and karatavic acids. VSOR/VRAC and RVD inhibition did not correlate with necrotic cell death induction.

CONCLUSION

The VSOR/VRAC channel blockage by Ferula sesquiterpenes was found to impair the CVR machinery of thymocytes, resulting in suppression of cell proliferation. The necrotic cell death is not a direct consequence of VSOR/VRAC and RVD inhibition, likely involving other cellular pathways.

LRRC8A-containing anion channels promote glioblastoma proliferation via a WNK1/mTORC2-dependent mechanism

Leucine-rich repeat-containing protein 8A (LRRC8A) is the essential subunit of ubiquitous volume-regulated anion channels (VRACs). LRCC8A is overexpressed in several cancers and promotes negative survival outcomes via a poorly defined mechanism. Here, we explored the role of LRRC8A and VRACs in the progression of glioblastoma (GBM), the most common and deadly primary brain tumor. We found that, as compared to healthy controls, LRRC8A mRNA was strongly upregulated in surgical GBM specimens, patient-derived GBM cell lines, and GBM datasets from The Cancer Genome Atlas (TCGA). Our in-silico analysis indicated that patients belonging to the lowest LRRC8A expression quartile demonstrated a trend for extended life expectancy. In patient-derived GBM cultures, siRNA-driven LRRC8A knockdown reduced cell proliferation and additionally decreased intracellular chloride levels and inhibited activity of mTOR complex 2. The antiproliferative effect of LRRC8A downregulation was recapitulated with a pharmacological inhibitor of VRAC. Our ensuing biochemical and molecular biology analyses established that the LRRC8A-containing VRACs facilitate GBM proliferation via a new mechanism involving non-enzymatic actions of the chloride-sensitive protein kinase WNK1. Accordingly, the chloride-bound WNK1 stimulates mTORC2 and the mTORC2-dependent protein kinases AKT and SGK, which promote proliferation. These findings establish the new mTORC2-centric axis for VRAC dependent regulation of cellular functions and uncover potential targets for GBM intervention.

Functions and clinical significance of KCNB1 in esophageal squamous cell carcinoma

BACKGROUND

Voltage-gated potassium channel subfamily B member 1 (KCNB1) encodes the α-subunit of the Kv2.1 channel and mediates transmembrane potassium transport. The functions and mechanisms underlying KCNB1 activation have been examined in various cancer types; however, its role in esophageal squamous cell carcinoma (ESCC) remains unclear. Therefore, the present study investigated the involvement of KCNB1 in tumor progression and the clinicopathological significance of its expression in ESCC.

METHODS

Knockdown experiments using KCNB1 small interfering RNA were performed on the human ESCC cell lines, KYSE70 and TE5, and changes in cell proliferation, the cell cycle, apoptosis, migration, and invasion were assessed. Gene expression profiles were examined using a microarray analysis. An immunohistochemical (IHC) analysis was performed on 129 primary tumor samples from ESCC patients who underwent curative esophagectomy.

RESULTS

Cell proliferation, G2-M phase progression, migration, and invasion were inhibited, and apoptosis was induced in KCNB1-depleted cells. Microarray results showed that KCNB1 gene expression affected Ephrin receptor signaling by suppressing EPHB1, EPHB2, and ERK1/2 gene expression. IHC results revealed a relationship between high KCNB1 expression and a poor prognosis. High KCNB1 expression was extracted as an independent prognostic factor in a multivariate analysis of 5-year relapse-free survival in ESCC patients (p = 0.0197).

CONCLUSIONS

Cell proliferation is controlled by KCNB1 through its regulation of ERK1/2 gene expression via ephrin receptor signaling. A relationship was observed between KCNB1 and the prognosis of ESCC patients, indicating its potential as a biomarker for cancer progression and in targeted therapy for ESCC.

Interactomic exploration of LRRC8A in volume-regulated anion channels

Ion channels are critical in enabling ion movement into and within cells and are important targets for pharmacological interventions in different human diseases. In addition to their ion transport abilities, ion channels interact with signalling and scaffolding proteins, which affects their function, cellular positioning, and links to intracellular signalling pathways. The study of "channelosomes" within cells has the potential to uncover their involvement in human diseases, although this field of research is still emerging. LRRC8A is the gene that encodes a crucial protein involved in the formation of volume-regulated anion channels (VRACs). Some studies suggest that LRRC8A could be a valuable prognostic tool in different types of cancer, serving as a biomarker for predicting patients' outcomes. LRRC8A expression levels might be linked to tumour progression, metastasis, and treatment response, although its implications in different cancer types can be varied. Here, publicly accessible databases of cancer patients were systematically analysed to determine if a correlation between VRAC channel expression and survival rate exists across distinct cancer types. Moreover, we re-evaluated the impact of LRRC8A on cellular proliferation and migration in colon cancer via HCT116 LRRC8A-KO cells, which is a current topic of debate in the literature. In addition, to investigate the role of LRRC8A in cellular signalling, we conducted biotin proximity-dependent identification (BioID) analysis, revealing a correlation between VRAC channels and cell-cell junctions, mechanisms that govern cellular calcium homeostasis, kinases, and GTPase signalling. Overall, this dataset improves our understanding of LRRC8A/VRAC and explores new research avenues while identifying promising therapeutic targets and promoting inventive methods for disease treatment.

LRRC8A as a central mediator promotes colon cancer metastasis by regulating PIP5K1B/PIP2 pathway

Colorectal cancer (CRC) has been the third most common malignancy and the second cause of cancer-related mortality. As the core of volume-sensitive chloride currents, leucine-rich repeat-containing 8A (LRRC8A) contributes to tumor progression but is not consistent, especially for whom the roles in colon carcinoma metastasis were not fully elucidated. Herein, LRRC8A proteins were found highly expressed in hematogenous metastasis from human colorectal cancer samples. The oxaliplatin-resistant HCT116 cells highly expressed LRRC8A, which was related to impaired proliferation and enhanced migration. The over-expressed LRRC8A slowed proliferation and increased migration ex vivo and in vivo. The elevated LRRC8A upregulated the focal adhesion, MAPK, AMPK, and chemokine signaling pathways via phosphorylation and dephosphorylation. Inhibition of LRRC8A impeded the TNF-α signaling cascade and TNF-α-induced migration. LRRC8A binding to PIP5K1B regulated the PIP2 formation, providing a platform for LRRC8A to mediate cell signaling transduction. Importantly, LRRC8A self-regulated its transcription via NF-κB1 and NF-κB2 pathways and the upregulation of NIK/NF-κB2/LRRC8A transcriptional axis was unfavorable for colon cancer patients. Collectively, our findings reveal that LRRC8A is a central mediator in mediating multiple signaling pathways to promote metastasis and targeting LRRC8A proteins could become a potential clinical biomarker-driven treatment strategy for colon cancer patients.

Physiological Functions of the Volume-Regulated Anion Channel VRAC/LRRC8 and the Proton-Activated Chloride Channel ASOR/TMEM206

Volume-regulated anion channels (VRACs) and the acid-sensitive outwardly rectifying anion channel (ASOR) mediate flux of chloride and small organic anions. Although known for a long time, they were only recently identified at the molecular level. VRACs are heteromers consisting of LRRC8 proteins A to E. Combining the essential LRRC8A with different LRRC8 paralogues changes key properties of VRAC such as conductance or substrate selectivity, which is how VRACs are involved in multiple physiological functions including regulatory volume decrease, cell proliferation and migration, cell death, purinergic signalling, fat and glucose metabolism, insulin signalling, and spermiogenesis. VRACs are also involved in pathological conditions, such as the neurotoxic release of glutamate and aspartate. Certain VRACs are also permeable to larger, organic anions, including antibiotics and anti-cancer drugs, making them an interesting therapeutic target. ASOR, also named proton-activated chloride channel (PAC), is formed by TMEM206 homotrimers on the plasma membrane and on endosomal compartments where it mediates chloride flux in response to extracytosolic acidification and plays a role in the shrinking and maturation of macropinosomes. ASOR has been shown to underlie neuronal swelling which causes cell death after stroke as well as promoting the metastasis of certain cancers, making them intriguing therapeutic targets as well.

LRRC8A promotes Glaesserella parasuis cytolethal distending toxin-induced p53-dependent apoptosis in NPTr cells

Glaesserella parasuis is an early colonizer of the swine upper respiratory tract and can break through the respiratory barrier for further invasion. However, the mechanisms underlying G. parasuis increases epithelial barrier permeability remain unclear. This study demonstrates that G. parasuis cytolethal distending toxin (CDT) induces p53-dependent apoptosis in new-born piglet tracheal (NPTr) cells. Moreover, we report for the first time that leucine-rich repeat-containing protein 8A (LRRC8A), an essential subunit of the volume-regulated anion channel (VRAC), involves in apoptosis of NPTr cells mediated by G. parasuis CDT. Pharmacological inhibition of VRAC with either PPQ-102 or NS3728 largely attenuated CDT-induced apoptosis in NPTr cells. Additionally, experiments with cells knocked down for LRRC8A using small interfering ribonucleic acid (siRNA) or knocked out LRRC8A using CRISPR/Cas9 technology showed a significant reduction in CDT-induced apoptosis. Conversely, re-expression of Sus scrofa LRRC8A in LRRC8A-/- NPTr cells efficiently complemented the CDT-induced apoptosis. In summary, these findings suggest that LRRC8A is pivotal for G. parasuis CDT-induced apoptosis, providing novel insights into the mechanism of apoptosis caused by CDT.

Validation of Epigenetic Markers for the Prediction of Response to Topical Corticosteroid Treatment in Eosinophilic Esophagitis

INTRODUCTION

We previously identified 18 CpG methylation biomarkers associated with treatment response to topical corticosteroids (tCS) in eosinophilic esophagitis (EoE). In this study, in an independent cohort, we assessed the validity of these CpG sites as treatment response biomarkers.

METHODS

DNA was extracted from prospectively biobanked esophageal biopsies from patients with newly diagnosed EoE enrolled in a randomized trial of 2 tCS formulations. Histologic response was defined as <15 eosinophils per high-power field. Pretreatment DNA methylation was assayed on the Illumina Human MethylationEPIC BeadChip. Logistic regression and area under the receiver operating characteristic curve analyses, adjusting for chip, position on the chip, age, sex, and baseline eosinophil count, were computed to test for an association between DNA methylation and treatment response at the 18 previously identified CpG sites.

RESULTS

We analyzed 88 patients (58 histologic responders, 30 nonresponders), with a mean age of 38 ± 16 years, 64% male, 97% White race. Of the 18 CpG sites, 13 met quality control criteria, and 3 were associated with responder status ( P < 0.012), including sites within UNC5B (cg26152017), ITGA6 (cg01044293), and LRRC8A (cg13962589). All 3 showed evidence of reduced methylation in treatment responders, consistent with the original discovery associations. The predictive probability for nonresponse with all 3 CpG sites was strong (area under the receiver operating characteristic curve = 0.79).

DISCUSSION

We validated epigenetic biomarkers (CpG methylation sites) for the prediction of tCS response in patients with EoE in an independent population. While not all previously identified markers replicated, 3 demonstrated a relatively high predictive probability for response to treatment and hold promise for guiding tCS treatment in EoE.

Trends in volume-regulated anion channel (VRAC) research: visualization and bibliometric analysis from 2014 to 2022

Objective: In this study, we utilized bibliometric methods to assess the worldwide scientific output and identify hotspots related to the research on the volume-regulated anion channel (VRAC) from 2014 to 2022. Methods: From Web of Science, we obtained studies related to VRAC published from 2014 to 2022. To analyzed the data, we utilized VOSviewer, a tool for visualizing network, to create networks based on the collaboration between countries, institutions, and authors. Additionally, we performed an analysis of journal co-citation, document citation, and co-occurrence of keywords. Furthermore, we employed CiteSpace (6.1. R6 Advanced) to analyzed keywords and co-cited references with the strongest burst. Results: The final analysis included a total of 278 related articles and reviews, covering the period from 2014 to 2022. The United States emerged as the leading country contributing to this field, while the University of Copenhagen stood out as the most prominent institution. The author with most publications and most citations was Thomas J. Jentsch. Among the cited references, the article by Voss et al. published in Science (2014) gained significant attention for its identification of LRRC8 heteromers as a crucial component of the volume-regulated anion channel VRAC. Pflügers Archiv European Journal of Physiology and Journal of Physiology-London were the leading journals in terms of the quantity of associated articles and citations. Through the analysis of keyword co-occurrence, it was discovered that VRAC is involved in various physiological processes including cell growth, migration, apoptosis, swelling, and myogenesis, as well as anion and organic osmolyte transport including chloride, taurine, glutamate and ATP. VRAC is also associated with related ion channels such as TMEM16A, TMEM16F, pannexin, and CFTR, and associated with various diseases including epilepsy, leukodystrophy, atherosclerosis, hypertension, cerebral edema, stroke, and different types of cancer including gastric cancer, glioblastoma and hepatocellular carcinoma. Furthermore, VRAC is involved in anti-tumor drug resistance by regulating the uptake of platinum-based drugs and temozolomide. Additionally, VRAC has been studied in the context of pharmacology involving DCPIB and flavonoids. Conclusion: The aim of this bibliometric analysis is to provide an overall perspective for research on VRAC. VRAC has become a topic of increasing interest, and our analysis shows that it continues to be a prominent area. This study offers insights into the investigation of VRAC channel and may guide researchers in identifying new directions for future research.

LRRC8A Is a Promising Prognostic Biomarker and Therapeutic Target for Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is a highly malignant tumor of the digestive system with increasing morbidity and mortality. The lack of sensitive and reliable biomarkers is one of the main reasons for the poor prognosis. Volume-regulated anion channels (VRAC), which are ubiquitously expressed in the vertebrate cell membrane, are composed of leucine-rich repeat-containing 8A (LRRC8A) and four other homologous family members (LRRC8B-E). VRAC heterogeneous complex is implicated in each of the six "hallmarks of cancer" and represents a novel therapeutic target for cancer. In this study, LRRC8A was speculated to be a promising prognostic biomarker and therapeutic target for PAAD based on a series of bioinformatics analyses. Additional cell experiments and immunohistochemical assays demonstrated that LRRC8A can affect the prognosis of PAAD and is correlated to cell proliferation, cell migration, drug resistance, and immune infiltration. Functional analysis indicated that LRRC8A influences the progression and prognosis of patients with PAAD by the regulation of CD8⁺ T cells immune infiltration. Taken together, these results can help in the design of new therapeutic drugs for patients with PAAD.

Functions and Clinical Significance of CACNA2D1 in Gastric Cancer

BACKGROUND

Voltage-gated calcium channels form as a complex of several subunits, among which the function of CACNA2D1, one of the genes encoding the α2δ subunit, remains unclear. The aim of our study was to investigate the role of CACNA2D1 and evaluate the efficacy of amlodipine, a blocker of CACNA2D1, in the treatment of gastric cancer (GC).

METHODS

Knockdown experiments were performed on the human GC cell lines MKN7 and HGC27 using CACNA2D1 small interfering RNA (siRNA), and changes in cell proliferation, the cell cycle, apoptosis, migration, and invasion were assessed. The gene expression profiles of cells were examined using a microarray analysis. An immunohistochemical (IHC) analysis was conducted on samples obtained from 196 GC patients who underwent curative gastrectomy. In addition, the antitumor effects of amlodipine were investigated using a xenograft model.

RESULTS

Cell proliferation, migration, and invasion were suppressed in CACNA2D1-depleted cells, and apoptosis was induced. The results of the microarray analysis showed that the apoptosis signaling pathway was enhanced via p53, BAX, and caspase 3 in CACNA2D1-depleted cells. A multivariate analysis identified high CACNA2D1 expression levels, confirmed by IHC, as an independent poor prognostic factor in GC patients. Moreover, subcutaneous tumor volumes were significantly smaller in a xenograft nude mouse model treated with a combination of amlodipine and cisplatin than in a model treated with cisplatin alone.

CONCLUSIONS

The present study indicates that CACNA2D1 regulates the apoptosis signaling pathway and may have potential as a biomarker for cancer growth and as a therapeutic target for GC.

LRRC8A influences the growth of gastric cancer cells via the p53 signaling pathway

BACKGROUND

Leucin-rich repeat containing protein A (LRRC8A), a component of the volume-regulated anion channel (VRAC), is activated by cell swelling and mediates regulatory volume decrease. We previously reported the expression of and important roles for several ion transporters in various gastrointestinal cancers, which have potential as novel targets for cancer treatment; however, the significance of LRRC8A in gastric cancer (GC) remains unclear.

MATERIALS AND METHODS

Knockdown experiments were performed by transfecting human GC cell lines with LRRC8A siRNA. Gene expression was then assessed using microarray analysis. Samples from 132 patients with GC were subjected to immunohistochemistry (IHC) for LRRC8A, and its relationships with clinicopathological factors and prognosis were examined.

RESULTS

The knockdown of LRRC8A suppressed the proliferation and movement of cells and enhanced apoptosis. The results of the microarray analysis showed the up- or down-regulated expression of genes related to the p53 signaling pathway (JNK, p53, p21, Bcl-2, and FAS) in LRRC8A-knockdown cells. IHC revealed a correlation between the expression of LRRC8A and the pT status (p = 0.015), and multivariate analysis identified the strong expression of LRRC8A as an independent prognostic factor for 5-year survival in GC patients (p = 0.0231).

CONCLUSIONS

The present results indicate that LRRC8A functions as a mediator of and/or biomarker for GC.

Roles of Ion and Water Channels in the Cell Death and Survival of Upper Gastrointestinal Tract Cancers

Ion and water channels were recently shown to be involved in cancer cell functions, and various transporter types have been detected in upper gastrointestinal tract (UGI) cancers. Current information on the expression and roles of these channels and transporters in the death and survival of UGI cancer cells was reviewed herein, and the potential of their regulation for cancer management was investigated. Esophageal cancer (EC) and gastric cancer (GC) cells and tissues express many different types of ion channels, including voltage-gated K⁺, Cl^-, and Ca²⁺, and transient receptor potential (TRP) channels, which regulate the progression of cancer. Aquaporin (AQP) 1, 3, and 5 are water channels that contribute to the progression of esophageal squamous cell carcinoma (ESCC) and GC. Intracellular pH regulators, including the anion exchanger (AE), sodium hydrogen exchanger (NHE), and vacuolar H⁺-ATPases (V-ATPase), also play roles in the functions of UGI cancer cells. We have previously conducted gene expression profiling and revealed that the regulatory mechanisms underlying apoptosis in ESCC cells involved various types of Cl^- channels, Ca²⁺ channels, water channels, and pH regulators (Shimizu et al., 2014; Ariyoshi et al., 2017; Shiozaki et al., 2017, 2018a; Kobayashi et al., 2018; Yamazato et al., 2018; Konishi et al., 2019; Kudou et al., 2019; Katsurahara et al., 2020, 2021; Matsumoto et al., 2021; Mitsuda et al., 2021). We have also previously demonstrated the clinicopathological and prognostic significance of their expression in ESCC patients, and shown that their pharmacological blockage and gene silencing had an impact on carcinogenesis, indicating their potential as targets for the treatment of UGI cancers. A more detailed understanding of the molecular regulatory mechanisms underlying cell death and survival of UGI cancers may result in the application of cellular physiological methods as novel therapeutic approaches.

Functional Analysis and Clinical Significance of Chloride Channel 2 Expression in Esophageal Squamous Cell Carcinoma

BACKGROUND

Chloride channel 2 (CLCN2) was recently shown to affect tumor behavior. The present study examined the functions of CLCN2 in the regulation of genes that play a role in tumor progression, as well as its clinicopathological significance in esophageal squamous cell carcinoma (ESCC).

METHODS

Knockdown experiments were conducted using CLCN2-small-interfering RNA, and changes in proliferation, survival, and cellular movement in human ESCC cell lines were investigated. A microarray analysis of gene expression profiles in CLCN2-depleted ESCC cells was conducted. Fifty-four primary ESCC samples were examined by immunohistochemistry (IHC).

RESULTS

The strong expression of CLCN2 was detected in TE5 and KYSE70 cells. Downregulated expression of CLCN2 enhanced proliferation and decreased apoptosis, whereas its upregulation inhibited proliferation and increased apoptosis. The effects of lubiprostone, a CLCN2 activator, were also investigated. In lubiprostone-treated cells, proliferation was inhibited and apoptosis was increased. The microarray analysis demonstrated that interferon (IFN) signaling-related genes were downregulated in CLCN2-depleted cells. IHC showed the presence of CLCN2 in the cytoplasm and cell membranes of ESCC cells. The prognostic analysis revealed a relationship between weak CLCN2 expression and shorter overall survival.

CONCLUSIONS

The present results indicate that tumor progression is regulated by CLCN2 through its effects on IFN signaling. Furthermore, weak CLCN2 expression was associated with poorer outcomes in ESCC patients. The present study will contribute to a clearer understanding of the role of CLCN2 as a mediator of ESCC, as well as its use as a biomarker for this cancer.

Lytic and sublytic effects of gossypol on red blood cells and thymocytes

Gossypol is a natural polyphenol presently considered as a promising biological phytochemical with a range of activities including anticancer. We examined volume regulation-dependent effects of gossypol using erythrocytes and thymic lymphocytes. Gossypol effectively lysed human red blood cells (RBC) with a half-maximal concentration of 67.4 ± 1.6 μmol/L and in a non-colloid osmotic manner. Sublytic gossypol doses of 1-10 μmol/L significantly protected RBC from osmotic hemolysis, but potentiated their sensitivity to the colloid-osmotic lysis induced by a pore-former nystatin. When added to the thymocytes suspension, gossypol caused a strong depression of the ability of cells to restore their volume under hypoosmotic stress with a half-maximal activity at 2.1 ± 0.3 μmol/L. Gossypol suppressed regulatory volume decrease under experimental conditions, when cationic permeability was controlled by gramicidin D, and volume recovery depended mainly on anionic conductance, suggesting that the polyphenol inhibits the swelling-induced anion permeability. In direct patch-clamp experiments, gossypol inhibited the volume-sensitive outwardly rectifying (VSOR) chloride channel in thymocytes and in human HCT116 and HeLa cells, possibly by a mechanism when gossypol molecule with a radius close to the size of channel pore plugs into the narrowest portion of the native VSOR chloride channel. Micromolar gossypol suppressed proliferation of thymocytes, HCT116 and HeLa cells. VSOR blockage may represent new mechanism of anticancer activity of gossypol in addition to its action as a BH3-mimetic.

Volume-regulated chloride channel regulates cell proliferation and is involved in the possible interaction between TMEM16A and LRRC8A in human metastatic oral squamous cell carcinoma cells

OBJECTIVES

Volume-regulated anion channels (VRACs), expressed in various cells, play an important role in cell volume regulation. Despite being physiologically defined almost half a century ago, only the molecular candidates of VRAC, TMEM16A, LRRC8A, and bestrophin-1 (BEST1), are known. Here, we aimed to explore the functional significance of VRAC in, HST-1, an oral squamous cell carcinoma (OSCC) cell line.

METHODS

Cell proliferation assays, RT-PCR, Western blot, and flow cytometry were used to estimate changes in gene expression and cell proliferation. Ion channel activity was recorded using the patch-clamp technique. Specific genes were knocked-down by siRNA assays.

RESULTS

VRAC, identified as a hypotonicity-induced current, was highly functional and associated with the proliferation of HST-1 cells but not of HaCaT (a normal keratinocyte) cells. The pharmacological profile of VRAC in HST-1 was similar to that reported previously. DCPIB, a specific VRAC inhibitor, completely inhibited VRAC and proliferation of HST-1 cells, eventually leading to apoptosis. VRAC in HST-1 was attenuated by the knockdown of TMEM16A and LRRC8A, while knockdown of BEST1 affected cell proliferation. In situ proximity ligation assay showed that TMEM16A and LRRC8A co-localized under isotonic conditions (300 mOsM) but were separated under hypotonic conditions (250 mOsM) on the plasma membrane.

CONCLUSIONS

We have found that VRAC acts to regulate the proliferation of human metastatic OSCC cells and the composition of VRAC may involve in the interactions between TMEM16A and LRRC8A in HST-1 cells.

Expression of LRRC8A is elevated in the cytoplasm of osteosarcoma tissues: An immunohistochemical study with tissue microarrays

The purpose of the present study was to investigate the expression profile of leucine-rich repeat-containing protein 8A (LRRC8A) in osteosarcoma and normal cortical bone, as well as its association with sex, age and tumor malignancy. Immunohistochemical staining of osteosarcoma tissue microarrays (TMAs) was performed to determine the protein expression of LRRC8A and compare them among different subgroups. The expression of LRRC8A in the nuclei and cytoplasm of U2OS tumor cells and MC3T3-E1 osteoblast-like cells was determined using reverse transcription-quantitative PCR. Of all samples of the TMA for patients with osteosarcoma that were tested, 94% featured high cytoplasmic expression of LRRC8A, while in all normal bone tissue control groups, the gene was mainly expressed in the nucleus. In MC3T3-E1 osteoblasts, the expression of LRRC8A at the RNA level was mainly in the cytoplasm. The difference in expression of LRRC8A between microarrays and osteoblasts was statistically significant. In U2OS osteosarcoma cells, LRRC8A mRNA was concentrated in the nuclei and cytoplasm. In osteosarcoma, the expression level of LRRC8A was not significantly associated with sex or age. In conclusion, LRRC8A was highly expressed in the cytoplasm of osteosarcoma cells and the degree of expression may be associated with the degree of tumor malignancy.