Loss of breast epithelial marker hCLCA2 promotes epithelial-to-mesenchymal transition and indicates higher risk of metastasis

Bestrophin-4 relays HES4 and interacts with TWIST1 to suppress epithelial-to-mesenchymal transition in colorectal cancer cells

Bestrophin isoform 4 (BEST4) is a newly identified subtype of the calcium-activated chloride channel family. Analysis of colonic epithelial cell diversity by single-cell RNA-sequencing has revealed the existence of a cluster of BEST4+ mature colonocytes in humans. However, if the role of BEST4 is involved in regulating tumour progression remains largely unknown. In this study, we demonstrate that BEST4 overexpression attenuates cell proliferation, colony formation, and mobility in colorectal cancer (CRC) in vitro, and impedes the tumour growth and the liver metastasis in vivo. BEST4 is co-expressed with hairy/enhancer of split 4 (HES4) in the nucleus of cells, and HES4 signals BEST4 by interacting with the upstream region of the BEST4 promoter. BEST4 is epistatic to HES4 and downregulates TWIST1, thereby inhibiting epithelial-to-mesenchymal transition (EMT) in CRC. Conversely, knockout of BEST4 using CRISPR/Cas9 in CRC cells revitalises tumour growth and induces EMT. Furthermore, the low level of the BEST4 mRNA is correlated with advanced and the worse prognosis, suggesting its potential role involving CRC progression.

Transport of CLCA2 to the nucleus by extracellular vesicles controls keratinocyte survival and migration

Chloride channel accessory 2 (CLCA2) is a transmembrane protein, which promotes adhesion of keratinocytes and their survival in response to hyperosmotic stress. Here we show that CLCA2 is transported to the nucleus of keratinocytes via extracellular vesicles. The nuclear localization is functionally relevant, since wild-type CLCA2, but not a mutant lacking the nuclear localization signal, suppressed migration of keratinocytes and protected them from hyperosmotic stress-induced cell death. In the nucleus, CLCA2 bound to and activated β-catenin, resulting in enhanced expression of Wnt target genes. Mass-spectrometry-based interaction screening and functional rescue studies identified RNA binding protein 3 as a key effector of nuclear CLCA2. This is of likely relevance in vivo because both proteins co-localize in the human epidermis. Together, these results identify an unexpected nuclear function of CLCA2 in keratinocytes under homeostatic and stress conditions and suggest a role of extracellular vesicles and their nuclear transport in the control of key cellular activities.

Self-Cleavage of Human Chloride Channel Accessory 2 Causes a Conformational Shift That Depends on Membrane Anchorage and Is Required for Its Regulation of Store-Operated Calcium Entry

Human CLCA2 regulates store-operated calcium entry (SOCE) by interacting with Orai1 and STIM1. It is expressed as a 943aa type I transmembrane protein that is cleaved at amino acid 708 to produce a diffusible 100 kDa product. The N-terminal ectodomain contains a hydrolase-like subdomain with a conserved HEXXH zinc-binding motif that is proposed to cleave the precursor autoproteolytically. Here, we tested this hypothesis and its link to SOCE. We first studied the conditions for autocleavage in isolated membranes and then in a purified protein system. Cleavage was zinc-dependent and abolished by mutation of the E in the HEXXH motif to Q, E165Q. Cleavage efficiency increased with CLCA2 concentration, implying that it occurs in trans. Accordingly, the E165Q mutant was cleaved by co-transfected wildtype CLCA2. Moreover, CLCA2 precursors with different epitope tags co-immunoprecipitated. In a membrane-free system utilizing immunopurified protease and target, no cleavage occurred unless the target was first denatured, implying that membranes provide essential structural or conformational cues. Unexpectedly, cleavage caused a conformational shift: an N-terminal antibody that immunoprecipitated the precursor failed to precipitate the N-terminal product unless the product was first denatured with an ionic detergent. The E165Q mutation abolished the stimulation of SOCE caused by wildtype CLCA2, establishing that the metalloprotease activity is required for this regulatory function.

Integrating TCGA and single-cell sequencing data for colorectal cancer: a 10-gene prognostic risk assessment model

Colorectal cancer represents a significant health threat, yet a standardized method for early clinical assessment and prognosis remains elusive. This study sought to address this gap by using the Seurat package to analyze a single-cell sequencing dataset (GSE178318) of colorectal cancer, thereby identifying distinctive marker genes characterizing various cell subpopulations. Through CIBERSORT analysis of colorectal cancer data within The Cancer Genome Atlas (TCGA) database, significant differences existed in both cell subpopulations and prognostic values. Employing WGCNA, we pinpointed modules exhibiting strong correlations with these subpopulations, subsequently utilizing the survival package coxph to isolate genes within these modules. Further stratification of TCGA dataset based on these selected genes brought to light notable variations between subtypes. The prognostic relevance of these differentially expressed genes was rigorously assessed through survival analysis, with LASSO regression employed for modeling prognostic factors. Our resulting model, anchored by a 10-gene signature originating from these differentially expressed genes and LASSO regression, proved adept at accurately predicting clinical prognoses, even when tested against external datasets. Specifically, natural killer cells from the C7 subpopulation were found to bear significant associations with colorectal cancer survival and prognosis, as observed within the TCGA database. These findings underscore the promise of an integrated 10-gene signature prognostic risk assessment model, harmonizing single-cell sequencing insights with TCGA data, for effectively estimating the risk associated with colorectal cancer.

FRA-1 as a Regulator of EMT and Metastasis in Breast Cancer

Among FOS-related components of the dimeric AP-1 transcription factor, the oncoprotein FRA-1 (encoded by FOSL1) is a key regulator of invasion and metastasis. The well-established FRA-1 pro-invasive activity in breast cancer, in which FOSL1 is overexpressed in the TNBC (Triple Negative Breast Cancer)/basal subtypes, correlates with the FRA-1-dependent transcriptional regulation of EMT (Epithelial-to-Mesenchymal Transition). After summarizing the major findings on FRA-1 in breast cancer invasiveness, we discuss the FRA-1 mechanistic links with EMT and cancer cell stemness, mediated by transcriptional and posttranscriptional interactions between FOSL1/FRA-1 and EMT-regulating transcription factors, miRNAs, RNA binding proteins and cytokines, along with other target genes involved in EMT. In addition to the FRA-1/AP-1 effects on the architecture of target promoters, we discuss the diagnostic and prognostic significance of the EMT-related FRA-1 transcriptome, along with therapeutic implications. Finally, we consider several novel perspectives regarding the less explored roles of FRA-1 in the tumor microenvironment and in control of the recently characterized hybrid EMT correlated with cancer cell plasticity, stemness, and metastatic potential. We will also examine the application of emerging technologies, such as single-cell analyses, along with animal models of TNBC and tumor-derived CTCs and PDXs (Circulating Tumor Cells and Patient-Derived Xenografts) for studying the FRA-1-mediated mechanisms in in vivo systems of EMT and metastasis.

A Monoclonal Human Alveolar Epithelial Cell Line ("Arlo") with Pronounced Barrier Function for Studying Drug Permeability and Viral Infections

In the development of orally inhaled drug products preclinical animal models regularly fail to predict pharmacological as well as toxicological responses in humans. Models based on human cells and tissues are potential alternatives to animal experimentation allowing for the isolation of essential processes of human biology and making them accessible in vitro. Here, the generation of a novel monoclonal cell line "Arlo," derived from the polyclonal human alveolar epithelium lentivirus immortalized cell line hAELVi via single-cell printing, and its characterization as a model for the human alveolar epithelium as well as a building block for future complex in vitro models is described. "Arlo" is systematically compared in vitro to primary human alveolar epithelial cells (hAEpCs) as well as to the polyclonal hAELVi cell line. "Arlo" cells show enhanced barrier properties with high transepithelial electrical resistance (TEER) of ≈3000 Ω cm2 and a potential difference (PD) of ≈30 mV under air-liquid interface (ALI) conditions, that can be modulated. The cells grow in a polarized monolayer and express genes relevant to barrier integrity as well as homeostasis as is observed in hAEpCs. Successful productive infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a proof-of-principle study offers an additional, attractive application of "Arlo" beyond biopharmaceutical experimentation.

Genomic, biochemical and expressional properties reveal strong conservation of the CLCA2 gene in birds and mammals

Recent studies have revealed the dynamic and complex evolution of CLCA1 gene homologues in and between mammals and birds with a particularly high diversity in mammals. In contrast, CLCA2 has only been found as a single copy gene in mammals, to date. Furthermore, CLCA2 has only been investigated in few mammalian species but not in birds. Here, we established core genomic, protein biochemical and expressional properties of CLCA2 in several bird species and compared them with mammalian CLCA2. Chicken, turkey, quail and ostrich CLCA2 were compared to their mammalian orthologues using in silico, biochemical and expressional analyses. CLCA2 was found highly conserved not only at the level of genomic and exon architecture but also in terms of the canonical CLCA2 protein domain organization. The putatively prototypical galline CLCA2 (gCLCA2) was cloned and immunoblotting as well as immunofluorescence analyses of heterologously expressed gCLCA2 revealed protein cleavage, glycosylation patterns and anchoring in the plasma membrane similar to those of most mammalian CLCA2 orthologues. Immunohistochemistry found highly conserved CLCA2 expression in epidermal keratinocytes in all birds and mammals investigated. Our results suggest a highly conserved and likely evolutionarily indispensable role of CLCA2 in keratinocyte function. Its high degree of conservation on the genomic, biochemical and expressional levels stands in contrast to the dynamic structural complexities and proposed functional diversifications between mammalian and avian CLCA1 homologues, insinuating a significant degree of negative selection of CLCA2 orthologues among birds and mammals. Finally, and again in contrast to CLCA1, the high conservation of CLCA2 makes it a strong candidate for studying basic properties of the functionally still widely unresolved CLCA gene family.

Evolutionarily conserved properties of CLCA proteins 1, 3 and 4, as revealed by phylogenetic and biochemical studies in avian homologues

Species-specific diversities are particular features of mammalian chloride channel regulator, calcium activated (CLCA) genes. In contrast to four complex gene clusters in mammals, only two CLCA genes appear to exist in chickens. CLCA2 is conserved in both, while only the galline CLCA1 (gCLCA1) displays close genetic distance to mammalian clusters 1, 3 and 4. In this study, sequence analyses and biochemical characterizations revealed that gCLCA1 as a putative avian prototype shares common protein domains and processing features with all mammalian CLCA homologues. It has a transmembrane (TM) domain in the carboxy terminal region and its mRNA and protein were detected in the alimentary canal, where the protein was localized in the apical membrane of enterocytes, similar to CLCA4. Both mammals and birds seem to have at least one TM domain containing CLCA protein with complex glycosylation in the apical membrane of enterocytes. However, some characteristic features of mammalian CLCA1 and 3 including entire protein secretion and expression in cell types other than enterocytes seem to be dispensable for chicken. Phylogenetic analyses including twelve bird species revealed that avian CLCA1 and mammalian CLCA3 form clades separate from a major branch containing mammalian CLCA1 and 4. Overall, our data suggest that gCLCA1 and mammalian CLCA clusters 1, 3 and 4 stem from a common ancestor which underwent complex gene diversification in mammals but not in birds.

<em>miR-19a</em> targeting <em>CLCA4</em> to regulate the proliferation, migration, and invasion of colorectal cancer cells

The role of miR-19a in colorectal cancer (CRC), a devastating disease with high mortality and morbidity, remains controversial. In the present study, we show that the level of miR-19a is significantly higher in clinical CRC tissue samples than in paracancerous tissue samples, and significantly higher in CRC cells lines HT29, SW480, and CaCO2 than in the normal human colon mucosal epithelial cell line NCM460. miR-19a mimics and inhibitors were synthesized and validated. Overexpression of miR-19a mimics significantly promoted, while miR-19a inhibitors inhibited, the proliferation, survival, migration, and invasion of SW480 and CaCO2 CRC cells. Furthermore, mRNA and protein levels of chloride channel accessory 4 (CLCA4) were lower in CRC cells and tissues. Bioinformatics and a luciferase reporter assay confirmed that CLCA4 was a miR-19a target. Further, miR-19a inhibition increased CLCA4 expression. The inhibitory effect of miR-19a on cell growth, survival, migration, and invasion was reversed by knockdown of CLCA4 expression. The data demonstrated that the miR-19a/CLCA4 axis modulates phospho-activation of the PI3K/AKT pathway in CRC cells. In conclusion, our results revealed that miR-19a overexpression decreases CLCA4 levels to promote CRC oncogenesis, suggesting that miR-19a inhibitors have potential applications for future therapeutic of CRC.

Epigenetic Repression of Chloride Channel Accessory 2 Transcription in Cardiac Fibroblast: Implication in Cardiac Fibrosis

Cardiac fibrosis is a key pathophysiological process that contributes to heart failure. Cardiac resident fibroblasts, exposed to various stimuli, are able to trans-differentiate into myofibroblasts and mediate the pro-fibrogenic response in the heart. The present study aims to investigate the mechanism whereby transcription of chloride channel accessory 2 (Clca2) is regulated in cardiac fibroblast and its potential implication in fibroblast-myofibroblast transition (FMyT). We report that Clca2 expression was down-regulated in activated cardiac fibroblasts (myofibroblasts) compared to quiescent cardiac fibroblasts in two different animal models of cardiac fibrosis. Clca2 expression was also down-regulated by TGF-β, a potent inducer of FMyT. TGF-β repressed Clca2 expression at the transcriptional level likely via the E-box element between -516 and -224 of the Clca2 promoter. Further analysis revealed that Twist1 bound directly to the E-box element whereas Twist1 depletion abrogated TGF-β induced Clca2 trans-repression. Twist1-mediated Clca2 repression was accompanied by erasure of histone H3/H4 acetylation from the Clca2 promoter. Mechanistically Twist1 interacted with HDAC1 and recruited HDAC1 to the Clca2 promoter to repress Clca2 transcription. Finally, it was observed that Clca2 over-expression attenuated whereas Clca2 knockdown enhanced FMyT. In conclusion, our data demonstrate that a Twist1-HDAC1 complex represses Clca2 transcription in cardiac fibroblasts, which may contribute to FMyT and cardiac fibrosis.

Upregulation of TTYH3 promotes epithelial-to-mesenchymal transition through Wnt/β-catenin signaling and inhibits apoptosis in cholangiocarcinoma

PURPOSE

Cholangiocarcinoma (CCA) is a highly invasive malignant tumor originating from the bile duct epithelium. Tweety homolog 3 (TTYH3) is a member of the family of calcium-activated chloride channels, which have several biological functions. Here, we aimed to investigate the expression and biological function of TTYH3 in CCA.

METHODS

The mRNA and protein expression levels of TTYH3 were investigated in primary human CCA tissues and normal tissues. The DNA methylation levels of three CpG sites in the TTYH3 promoter region were evaluated using pyrosequencing. The effect of TTYH3 expression on proliferation, apoptosis, migration and invasion were assessed in HUCCT1 and QBC939 cells. Xenograft models were developed to substantiate its role in the development of CCA. Western blot analysis was used to investigate the mechanistic role of TTYH3 in regulating CCA progression.

RESULTS

We found that TTYH3 was highly expressed both at the mRNA and protein levels in CCA (p = 0.0001) and that the expression levels were significantly related to a poor overall survival of the patients (p = 0.0019). The DNA methylation levels of three CpG sites in the TTYH3 promoter region were significantly lower in CCA tissues compared to normal tissues (p < 0.05). In vitro studies indicated that TTYH3 can promote the proliferation, migration and invasion of the CCA cells. TTYH3 overexpression significantly promoted tumor progression and cellular proliferation in vivo as indicated by Ki-67 expression. In addition, we found that exogenous TTYH3 overexpression induced epithelial-mesenchymal transition (EMT) in CCA as indicated by expression changes in E-cadherin, N-cadherin and vimentin. The EMT process was found to occur through the Wnt/β-catenin signaling pathway, with simultaneous changes in P-GSK3β and β-catenin levels.

CONCLUSIONS

Our data indicate that DNA hypomethylation-induced overexpression of TTYH3 regulates CCA development and metastasis through the Wnt/β-catenin pathway.

Decreased expression of CLCA2 and the correlating with immune infiltrates in patients with cervical squamous cell carcinoma: A bioinformatics analysis

OBJECTIVE

Calcium-activated chloride channel 2 (CLCA2) is closely related to the invasion, metastasis, and prognosis of some common malignant tumors. The present study aimed to evaluate the role of CLCA2 in cervical squamous cell carcinoma (CESC) using bioinformatics analysis.

MATERIALS AND METHODS

The mRNA sequencing data and the corresponding clinical data were obtained from Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA) database respectively. Then univariate analysis of variance was used to analyze the differential mRNA expression of CLCA2 between normal, cervical Intraepithelial neoplasia (CIN), and CESC tissues and clinicopathological characteristics. The Gene Expression Profiling Interactive Analysis (GEPIA) was used to assess the association between CLCA2 and Disease-Free Survival (DFS), overall survival (OS). The Gene Set Enrichment Analysis (GSEA) was used to explore the associated signaling pathways. The Tumor Immune Estimation Resource (TIMER) was used to predict the potential biological roles of CLCA2 in tumor-immune of CESC.

RESULTS

CLCA2 expression was significantly decreased in CESC tissues compared with normal and CIN tissues (P < 0.05). Meanwhile, obese patients had lower levels of CLCA2 expression than normal-weight CESC patients (P < 0.05). However, there was no significant difference in the expression level of CLCA2 in patients with different T stage, lymph node status, metastasis, and FIGO stage in CC(P > 0.05). The survival analysis indicated that for DFS, CESC with high CLCA2 expression was associated with better prognoses compared with those with low expression levels (P < 0.05). But for the OS, there was no difference. GSEA revealed that 4 pathways exhibited significant differential enrichment in the CLCA2 high-expression phenotype, including the P53 signaling pathway, the ERBB signaling pathway, the NOTCH signaling pathway, and the ubiquitin-mediated proteolysis. The TIMER reveals the expression of CLCA2 showed a significant inverse association with the number of B cells, Macrophage cells, and Dendritic Cell infiltration.

CONCLUSION

The present study indicates that CLCA2 expression may be a potential prognostic marker for patients with CESC.

The epithelial sodium channel has a role in breast cancer cell proliferation

PURPOSE

Breast cancer is the most common cancer affecting women worldwide with half a million associated deaths annually. Despite a huge global effort, the pathways of breast cancer progression are not fully elucidated. Ion channels have recently emerged as novel regulators of cancer cell proliferation and metastasis. The epithelial sodium channel, ENaC, made up of α, β and γ subunits is well known for its role in Na⁺ reabsorption in epithelia, but a number of novel roles for ENaC have been described, including potential roles in cancer. A role for ENaC in breast cancer, however, has yet to be described. Therefore, the effects of ENaC level and activity on breast cancer proliferation were investigated.

METHODS

Through the publicly available SCAN-B dataset associations between αENaC mRNA expression and breast cancer subtypes, proliferation markers and epithelial-mesenchymal transition markers (EMT) were assessed. αENaC expression, through overexpression or siRNA-mediated knockdown, and activity, through the ENaC-specific inhibitor amiloride, were altered in MCF7, T47D, BT549, and MDAMB231 breast cancer cells. MTT and EdU cell proliferation assays were used to determine the effect of these manipulations on breast cancer cell proliferation.

RESULTS

High αENaC mRNA expression was associated with less aggressive and less proliferative breast cancer subtypes and with reduced expression of proliferation markers. Decreased αENaC expression or activity, in the mesenchymal breast cancer cell lines BT549 and MDAMB231, increased breast cancer cell proliferation. Conversely, increased αENaC expression decreased breast cancer cell proliferation.

CONCLUSION

αENaC expression is associated with a poor prognosis in breast cancer and is a novel regulator of breast cancer cell proliferation. Taken together, these results identify ENaC as a potential future therapeutic target.

The calcium-activated chloride channel-associated protein rCLCA2 is expressed throughout rat epidermis, facilitates apoptosis and is downmodulated by UVB

The rodent chloride channel regulatory proteins mCLCA2 and its porcine and human homologues pCLCA2 and hCLCA2 are expressed in keratinocytes but their localization and significance in the epidermis have remained elusive. hCLCA2 regulates cancer cell migration, invasion and apoptosis, and its loss predicts poor prognosis in many tumors. Here, we studied the influences of epidermal maturation and UV-irradiation (UVR) on rCLCA2 (previous rCLCA5) expression in cultured rat epidermal keratinocytes (REK) and correlated the results with mCLCA2 expression in mouse skin in vivo. Furthermore, we explored the influence of rCLCA2 silencing on UVR-induced apoptosis. rClca2 mRNA was strongly expressed in REK cells, and its level in organotypic cultures remained unchanged during the epidermal maturation process from a single cell layer to fully differentiated, stratified cultures. Immunostaining confirmed its uniform localization throughout the epidermal layers in REK cultures and in rat skin. A single dose of UVR modestly downregulated rClca2 expression in organotypic REK cultures. The immunohistochemical staining showed that CLCA2 localized in basal and spinous layers also in mouse skin, and repeated UVR induced its partial loss. Interestingly, silencing of rCLCA2 reduced the number of apoptotic cells induced by UVR, suggesting that by facilitating apoptosis, CLCA2 may protect keratinocytes against the risk of malignancy posed by UVB-induced corrupt DNA.

Downregulation of CLCA4 expression is associated with the development and progression of colorectal cancer

The molecular mechanisms involved in the development and progression of colorectal cancer (CRC) are not completely understood. The present study aimed to identify potential novel genes involved in the development and progression of CRC. Database analysis revealed that the mRNA level of the chloride channel accessory 4 (CLCA4) was frequently lower in primary tumor tissues compared with that in corresponding non-cancerous colon tissues, and was even lower in liver metastases than in primary tumors. Further analyses through The Human Protein Atlas (THPA) website and immunohistochemistry (IHC)-based tissue microarray (TMA) confirmed that CLCA4 mRNA and protein expression were downregulated in CRC tissues. Furthermore, IHC-based TMA analysis revealed a gradual decrease in CLCA4 protein expression among colorectal normal, adenoma and carcinoma tissues. Survival analysis revealed that the decrease in CLCA4 mRNA expression was associated with the overall survival rate of patients with different types of tumor, including CRC, breast cancer, head and neck cancer and stomach cancer. Overall, downregulated CLCA4 expression may influence the development and progression of CRC.

The nuclear oncoprotein Fra-1: a transcription factor knocking on therapeutic applications' door

Among the FOS-related members of the AP-1 dimeric complex, the transcription factor Fra-1, encoded by FOSL1, is crucially involved in human tumor progression and metastasis, thus representing a promising therapeutic target. Here we review the state of the art and discuss the emerging topics and perspectives on FOSL1 and its gene product. First, we summarize the present knowledge on the FOSL1 transcriptional and epigenetic controls, driving Fra-1 accumulation in a variety of human solid tumors. We also present a model on the regulatory interactions between Fra-1, p53, and miRNAs. Then, we outline the multiple roles of Fra-1 posttranslational modifications and transactivation mechanisms of select Fra-1 target genes. In addition to summarizing the Fra-1-dependent gene networks controlling proliferation, survival, and epithelial-mesenchymal transitions (EMT) in multiple cancer cell types, we highlight the roles played by Fra-1 in nonneoplastic cell populations recruited to the tumor microenvironment, and in mouse models of tumorigenesis. Next, we review the prognostic power of the Fra-1-associated gene signatures, and envisage potential strategies aimed at Fra-1 therapeutic inhibition. Finally, we discuss several recent reports showing the emerging roles of Fra-1 in the mechanisms of both resistance and addiction to targeted therapies.

CLCA2 expression is associated with survival among African American women with triple negative breast cancer

PURPOSE

Black/African American (AA) women are twice as likely to be diagnosed with triple negative breast cancer (TNBC) compared to whites, an aggressive breast cancer subtype associated with poor prognosis. There are no routinely used targeted clinical therapies for TNBC; thus there is a clear need to identify prognostic markers and potential therapeutic targets.

METHODS

We evaluated expression of 27,016 genes in 155 treatment-naïve TN tumors from AA women in Detroit. Associations with survival were evaluated using Cox proportional hazards models adjusting for stage and age at diagnosis, and p-values were corrected using a false discovery rate. Our validation sample consisted of 494 TN tumors using four publically available data sets. Meta-analyses were performed using summary statistics from the four validation results.

RESULTS

In the Detroit AA cohort, CLCA2 [Hazard ratio (HR) = 1.56, 95% confidence interval (CI) 1.31-1.86, nominal p = 5.1x10-7, FDR p = 0.014], SPIC [HR = 1.47, 95%CI 1.26-1.73, nominal p = 1.8x10-6, FDR p = 0.022], and MIR4311 [HR = 1.57, 95% CI 1.31-1.92, nominal p = 2.5x10-5, FDR p = 0.022] expression were associated with overall survival. Further adjustment for treatment and breast cancer specific survival analysis did not substantially alter effect estimates. CLCA2 was also associated with increased risk of death in the validation cohorts [HR = 1.14, 95% CI 1.05-1.24, p = 0.038, p-heterogeneity = 0.88].

CONCLUSIONS

We identified CLCA2 as a potential prognostic marker for TNBC in AA women.

CLCA4 inhibits cell proliferation and invasion of hepatocellular carcinoma by suppressing epithelial-mesenchymal transition via PI3K/AKT signaling

Calcium activated Chloride Channel A4 (CLCA4), as a tumor suppressor, was reported to contribute to the progression of several malignant tumors, yet little is known about the significance of CLCA4 in invasion and prognosis of hepatocellular carcinoma (HCC). CLCA4 expression was negatively correlated with tumor size, vascular invasion and TNM stage. Kaplan-Meier analysis showed that CLCA4 was an independent predictor for overall survival (OS) and time to recurrence (TTR). In addition, CLCA4 status could act as prognostic predictor in different risk of subgroups. Moreover, combination of CLCA4 and serum AFP could be a potential predictor for survival in HCC patients. Furthermore, CLCA4 may inhibit cell migration and invasion by suppressing epithelial-mesenchymal transition (EMT) via PI3K/ATK signaling. Knockdown of CLCA4 significantly increased the migration and invasion of HCC cells and changed the expression pattern of EMT markers and PI3K/AKT phosphorylation. An opposite expression pattern of EMT markers and PI3K/AKT phosphorylation was observed in CLCA4-transfected cells. Additionally, immunohistochemistry and RT-PCR results further confirmed this correlation. Taken together, CLCA4 contributes to migration and invasion by suppressing EMT via PI3K/ATK signaling and predicts favourable prognosis of HCC. CLCA4/AFP expression may help to distinguish different risks of HCC patients after hepatectomy.

Humidity-regulated CLCA2 protects the epidermis from hyperosmotic stress

Low environmental humidity aggravates symptoms of the inflammatory skin disease atopic dermatitis (AD). Using mice that develop AD-like signs, we show that an increase in environmental humidity rescues their cutaneous inflammation and associated epidermal abnormalities. Quantitative proteomics analysis of epidermal lysates of mice kept at low or high humidity identified humidity-regulated proteins, including chloride channel accessory 3A2 (CLCA3A2), a protein with previously unknown function in the skin. The epidermis of patients with AD, organotypic skin cultures under dry conditions, and cultured keratinocytes exposed to hyperosmotic stress showed up-regulation of the nonorthologous human homolog CLCA2. Hyperosmolarity-induced CLCA2 expression occurred via p38/c-Jun N-terminal kinase-activating transcription factor 2 signaling. CLCA2 knockdown promoted keratinocyte apoptosis induced by hyperosmotic stress through impairment of cell-cell adhesion. These findings provide a mechanistic explanation for the beneficial effect of high environmental humidity for AD patients and identify CLCA3A2/CLCA2 up-regulation as a mechanism to protect keratinocytes from damage induced by low humidity.

Prediction of regulatory targets of alternative isoforms of the epidermal growth factor receptor in a glioblastoma cell line

Background

The epidermal growth factor receptor (EGFR) is a major regulator of proliferation in tumor cells. Elevated expression levels of EGFR are associated with prognosis and clinical outcomes of patients in a variety of tumor types. There are at least four splice variants of the mRNA encoding four protein isoforms of EGFR in humans, named I through IV. EGFR isoform I is the full-length protein, whereas isoforms II-IV are shorter protein isoforms. Nevertheless, all EGFR isoforms bind the epidermal growth factor (EGF). Although EGFR is an essential target of long-established and successful tumor therapeutics, the exact function and biomarker potential of alternative EGFR isoforms II-IV are unclear, motivating more in-depth analyses. Hence, we analyzed transcriptome data from glioblastoma cell line SF767 to predict target genes regulated by EGFR isoforms II-IV, but not by EGFR isoform I nor other receptors such as HER2, HER3, or HER4.

Results

We analyzed the differential expression of potential target genes in a glioblastoma cell line in two nested RNAi experimental conditions and one negative control, contrasting expression with EGF stimulation against expression without EGF stimulation. In one RNAi experiment, we selectively knocked down EGFR splice variant I, while in the other we knocked down all four EGFR splice variants, so the associated effects of EGFR II-IV knock-down can only be inferred indirectly. For this type of nested experimental design, we developed a two-step bioinformatics approach based on the Bayesian Information Criterion for predicting putative target genes of EGFR isoforms II-IV. Finally, we experimentally validated a set of six putative target genes, and we found that qPCR validations confirmed the predictions in all cases.

Conclusions

By performing RNAi experiments for three poorly investigated EGFR isoforms, we were able to successfully predict 1140 putative target genes specifically regulated by EGFR isoforms II-IV using the developed Bayesian Gene Selection Criterion (BGSC) approach. This approach is easily utilizable for the analysis of data of other nested experimental designs, and we provide an implementation in R that is easily adaptable to similar data or experimental designs together with all raw datasets used in this study in the BGSC repository, https://github.com/GrosseLab/BGSC.

Electronic supplementary material

The online version of this article (10.1186/s12859-019-2944-9) contains supplementary material, which is available to authorized users.

Keratin 14-high subpopulation mediates lung cancer metastasis potentially through Gkn1 upregulation

Metastasis is the leading cause of lung cancer-related death. Elucidating the metastasis process can provide new avenues to inhibit this malignant behavior of cancer cells. Here we found that human lung cancers with high Keratin 14 (K14) expression were associated with nodal metastasis and poor survival. Using the Kras^G12D/Trp53^L/L lung cancer mouse model, we confirmed that K14-high cancer cells harbored increased metastatic potential. Mechanistic investigation revealed that Gastrokine 1 (Gkn1) expression positively correlated with K14 level, cancer metastasis, and poor patient survival. Importantly, ectopic expression of Gkn1 enhanced the metastatic capability of K14-low cells in vitro and in vivo, whereas knockdown of Gkn1 did the opposite, indicating the importance of Gkn1 in mediating the metastasis of K14-high cells. Further study demonstrated that Gkn1 expression conferred K14-high cells resistance to anoikis, which is critical for cancer metastasis. Collectively, our findings demonstrate that K14-high cells contribute to lung cancer metastasis potentially through inhibition of anoikis via upregulation of Gkn1.

Calcium-Activated Chloride Channel A4 (CLCA4) Plays Inhibitory Roles in Invasion and Migration Through Suppressing Epithelial-Mesenchymal Transition via PI3K/AKT Signaling in Colorectal Cancer

Background

Calcium-activated chloride channel A4 (CLCA4) is known as a tumor suppressor which contributes to the progression of a number of types of malignant tumors. However, little is known about the functional roles of CLCA4 in colorectal cancer (CRC).

Material/Methods

In this study, the expression patterns and dysregulation of mRNAs in CRC tissues were profiled by analyzing GSE21510 datasets from Gene Expression Omnibus database which contains 104 primary hepatocellular carcinoma tissues and 24 normal liver tissues, and by performing Kaplan-Meier analysis of TCGA data. Additionally, immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) were performed using clinical tissues collected at our institute. In order to explore the functional role of CLCA4, gain-of-function cell models were constructed in SW620 and LoVo cells. Wound healing assay and Transwell assay were carried out to access the cell migration and invasion ability.

Results

It was found that CLCA4 was an independent predictor for overall survival and lymph node metastasis. Additionally, immunohistochemistry and qRT-PCR results of the clinical tissues collected as part of our study further confirmed this correlation. In vitro experiments demonstrated that over-expression of CLCA4 could inhibit cell migration and invasion by suppressing epithelial-mesenchymal transition (EMT) via PI3K/ATK signaling and change the expression patterns of EMT markers in CLCA4-gain-of-function cell models.

Conclusions

CLCA4 inhibits migration and invasion by suppressing EMT via PI3K/ATK signaling and predicts favorable prognosis of CRC which may help to distinguish potential risk of lymph node metastasis in CRC.

Silencing growth hormone receptor inhibits estrogen receptor negative breast cancer through ATP-binding cassette sub-family G member 2

Growth hormone receptor (GHR) plays a vital role in breast cancer chemoresistance and metastasis but the mechanism is not fully understood. We determined if GHR could be a potential therapeutic target for estrogen receptor negative (ER-ve) breast cancer, which are highly chemoresistant and metastatic. GHR was stably knocked down in ER-ve breast cancer cells and its effect on cell proliferation, metastatic behavior, and chemosensitivity to docetaxel (DT) was assessed. Microarray analysis was performed to identify potential GHR downstream targets involved in chemoresistance. GHR and ATP-binding cassette sub-family G member 2 (ABCG2) overexpression and knockdown studies were performed to investigate the mechanism of GHR-induced chemoresistance. Patient-derived xenografts was used to study the effect of GHR and ABCG2. Immunohistochemical data was used to determine the correlation between GHR, pAKT, pmTOR, and ABCG2 expressions. GHR silencing drastically reduced the chemoresistant and metastatic behavior of ER-ve breast cancer cells and also inhibited AKT/mTOR pathway. In contrast, activation, or overexpression of GHR increased chemoresistance and metastasis by increasing the expression and promoter activity, of ABCG2. Inhibition of JAK2/STAT5 signaling repressed GHR-induced ABCG2 promoter activity and expression. Further, ABCG2 knockdown significantly increased the chemosensitivity. Finally, patient-derived xenograft studies revealed the role of GHR in chemoresistance. Overall, these findings demonstrate that targeting GHR could be a novel therapeutic approach to overcome chemoresistance and associated metastasis in aggressive ER-ve breast cancers.

Ion channels as therapeutic antibody targets

It is now well established that antibodies have numerous potential benefits when developed as therapeutics. Here, we evaluate the technical challenges of raising antibodies to membrane-spanning proteins together with enabling technologies that may facilitate the discovery of antibody therapeutics to ion channels. Additionally, we discuss the potential targeting opportunities in the anti-ion channel antibody landscape, along with a number of case studies where functional antibodies that target ion channels have been reported. Antibodies currently in development and progressing towards the clinic are highlighted.

Do Different Stemness Markers Identify Different Pools of Cancer Stem Cells in Malignancies: A Study on ER+ and ER-Breast Cancer Cell Lines

In view of popularity of cancer stem cell (CSC) model all events in evolution of cancer are being explained in that context. Breast cancer is first solid tumor in which CSCs were identified. We aimed to compare stemness profile of two major subtypes [Estrogen receptor positive (ER⁺) and negative (ER^-)] breast cancer using different sets of markers. Expression of CD44/CD24, CK/Vimentin, E-Cadherin/Fibronectin and percentage of side population (SP) was studied in ER⁺ (T47D) and ER^- (MDA-MB-231) cell lines by flow cytometry. Breast CSCs (BCSCs) were sorted using CD44⁺/CD24^-/low expression and SP analysis and cultured. BCSCs were then compared with Non-CSCs (NCSCs) for response to drugs (Paclitaxel and Cisplatin), Ki67 and ER expression. Results showed higher expression of stemness markers (CD44⁺/CD24^-/low, CK⁺/Vimentin⁺ and E-Cadherin^-/Fibrinectin^F+) in MDA-MB-231 cells. Percentage SP representing BCSCs was found to be significantly more in later (3.20 ± 0.002 cf. T47D 1.25% ± 0.0007). BCSCs were found to be more resistant to drugs as compared to NCSCs in both cell lines. ER expression was weak in BCSCs sorted from T47D as compared to NCSCs. Ki67 was expressed in both BCSCs and NCSCs. Differences in expression of stemness markers help to explain aggressive behavior, higher recurrence rate and metastatic potential of MDA-MB-231 cells. However, no correlation amongst different markers used suggests that they may be identifying varied populations of cells in tumor hierarchy. A weak ER expression in BCSCs may be strategy used by BCSCs to escape effect of hormone therapy in ER⁺ breast cancers.

CLCA2 is a positive regulator of store-operated calcium entry and TMEM16A

The Chloride Channel Accessory (CLCA) protein family was first characterized as regulators of calcium-activated chloride channel (CaCC) currents (ICaCC), but the mechanism has not been fully established. We hypothesized that CLCAs might regulate ICaCC by modulating intracellular calcium levels. In cells stably expressing human CLCA2 or vector, we found by calcium imaging that CLCA2 moderately enhanced intracellular-store release but dramatically increased store-operated entry of calcium upon cytosolic depletion. Moreover, another family member, CLCA1, produced similar effects on intracellular calcium mobilization. Co-immunoprecipitation revealed that CLCA2 interacted with the plasma membrane store-operated calcium channel ORAI-1 and the ER calcium sensor STIM-1. The effect of CLCA2 on ICaCC was tested in HEK293 stably expressing calcium-activated chloride channel TMEM16A. Co-expression of CLCA2 nearly doubled ICaCC in response to a calcium ionophore. These results unveil a new mechanism by which CLCA family members activate ICaCC and suggest a broader role in calcium-dependent processes.

Along with its favorable prognostic role, CLCA2 inhibits growth and metastasis of nasopharyngeal carcinoma cells via inhibition of FAK/ERK signaling

Background

CLCA2 was reported as a tumor suppressor and disregulated in breast cancer. However, its function in tumor growth and metastasis in NPC has rarely been reported. In this study, we investigated the functional and molecular mechanisms by which CLCA2 influences NPC.

Methods

CLCA2 expression in human NPC cell lines and tissues was examined via real-time PCR (RT-PCR), Western blot and IHC. The biological roles of CLCA2 in proliferative, migration and invasion of NPC cell lines was evaluated in 5-8F, S18, S26 and SUNE-1 cells. Cell viability, migration and invasion were assessed in vitro by MTS, colony formation and transwell assay, respectively. CLCA2 in growth and metastasis of NPC were evaluated in vivo through NPC xenograft tumor growth, lung metastatic mice model and popliteal lymph node (LN) metastasis model.

Results

Overexpression of CLCA2 significantly decreased proliferation, migration and invasion of NPC cells. In contrast, knockdown of CLCA2 elicited the opposite effects. CLCA2 overexpression suppressed xenograft tumor growth and lung, popliteal lymph node (LN) metastasis in vivo. CLCA2 inhibited tumor metastasis through suppressing epithelial-Mesenchymal transition (EMT) and in-activating FAK/ERK1/2 signaling pathway in NPC cells. Immunohistochemical staining of 143 NPC samples revealed that CLCA2 expression was an independent, favorable prognostic factor for overall survival and distant metastasis-free survival of patients. In addition, inhibition of FAK and ERK1/2 reversed CLCA2 silencing-induced tumor cell migration. Furthermore, inhibitors against chloride channels suppressed NPC cellular migration which could have been enhanced by the presence of CLCA2.

Conclusion

CLCA2 suppress NPC proliferation, migration, invasion and epithelial-mesenchymal transition through inhibiting FAK/ERK signaling.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0692-8) contains supplementary material, which is available to authorized users.

Proteomic analyses identify prognostic biomarkers for pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy. Here we show that shotgun and targeted protein sequencing can be used to identify potential prognostic biomarkers in formalin-fixed paraffin-embedded specimens from 9 patients with PDAC with "short" survival (<12 months) and 10 patients with "long" survival (>45 months) undergoing surgical resection. A total of 24 and 147 proteins were significantly upregulated [fold change ≥2 or ≤0.5 and P<0.05; or different detection frequencies (≥5 samples)] in patients with "short" survival (including GLUT1) and "long" survival (including C9orf64, FAM96A, CDH1 and CDH17), respectively. STRING analysis of these proteins indicated a tight protein-protein interaction network centered on TP53. Ingenuity pathway analysis linked proteins representing "activated stroma factors" and "basal tumor factors" to poor prognosis of PDAC. It also highlighted TCF1 and CTNNB1 as possible upstream regulators. Further parallel reaction monitoring verified that seven proteins were upregulated in patients with "short" survival (MMP9, CLIC3, MMP8, PRTN3, P4HA2, THBS1 and FN1), while 18 proteins were upregulated in patients with "long" survival, including EPCAM, LGALS4, VIL1, CLCA1 and TPPP3. Thus, we verified 25 protein biomarker candidates for PDAC prognosis at the tissue level. Furthermore, an activated stroma status and protein-protein interactions with TP53 might be linked to poor prognosis of PDAC.

CLCA4 inhibits bladder cancer cell proliferation, migration, and invasion by suppressing the PI3K/AKT pathway

Calcium activated chloride channel A4 (CLCA4), a tumor suppressor, was shown to contribute to the progression of several human cancers, while its role in bladder carcinoma remains unclear. In this study, we showed CLCA4 expression was down-regulated in bladder carcinoma tissues and cells compared to adjacent non-tumor tissues and normal urothelial cells. Low CLCA4 expression was correlated with larger tumor size, advanced tumor stage, and poor prognosis in bladder carcinoma patients. Overexpression of CLCA4 profoundly attenuated the proliferation, growth, migratory and invasive capabilities of bladder cancer cells, whereas CLCA4 knockdown had the opposite effect. Mechanistically, CLCA4 is involved in PI3K/AKT signaling and its downstream molecules can promote bladder cancer cell proliferation. Additionally, CLCA4 could mediate the migration and invasion of bladder cancer cells by regulating epithelial-mesenchymal transition and PI3K/Akt activation. This study suggests that CLCA4 may represent a promising prognostic biomarker for bladder cancer and provides a possible mechanism for bladder cancer growth and invasion.

CLCA1 suppresses colorectal cancer aggressiveness via inhibition of the Wnt/beta-catenin signaling pathway

Background

Chloride channel accessory 1 (CLCA1) belongs to the calcium-sensitive chloride conductance protein family, which is mainly expressed in the colon, small intestine and appendix. This study was conducted to investigate the functions and mechanisms of CLCA1 in colorectal cancer (CRC).

Methods

The CLCA1 protein expression level in CRC patients was evaluated by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and western blotting analysis. Using CRISPR/Cas9 technology, CLCA1-upregulated (CLCA1-ACT) and CLCA1-knockout cells (CLCA1-KO), as well as their respective negative controls (CLCA1-ACT-NC and CLCA1-KO-NC), were constructed from the SW620 cell line. Cell growth and metastatic ability were assessed both in vitro and in vivo. The association of CLCA1 with epithelial-mesenchymal transition (EMT) and other signaling pathways was determined by western blotting assays.

Results

The expression level of CLCA1 in CRC tissues was significantly decreased compared with that in adjacent normal tissue (P< 0.05). Meanwhile, the serum concentration of CLCA1 in CRC patients was also significantly lower when compared with that of healthy controls (1.48 ± 1.06 ng/mL vs 1.06 ± 0.73 ng/mL, P = 0.0018). In addition, CLCA1 serum concentration and mRNA expression level in CRC tissues were inversely correlated with CRC metastasis and tumor stage. Upregulated CLCA1 suppressed CRC growth and metastasis in vitro and in vivo, whereas inhibition of CLCA1 led to the opposite results. Increased expression levels of CLCA1 could repress Wnt signaling and the EMT process in CRC cells.

Conclusions

Our findings suggest that increased expression levels of CLCA1 can suppress CRC aggressiveness. CLCA1 functions as a tumor suppressor possibly via inhibition of the Wnt/beta-catenin signaling pathway and the EMT process.

Electronic supplementary material

The online version of this article (dio: 10.1186/s12964-017-0192-z) contains supplementary material, which is available to authorized users.

The fibroblast surface markers FAP, anti-fibroblast, and FSP are expressed by cells of epithelial origin and may be altered during epithelial-to-mesenchymal transition

The identification of fibroblasts and cancer-associated fibroblasts from human cancer tissue using surface markers is difficult, especially because the markers used currently are usually not expressed solely by fibroblasts, and the identification of fibroblast-specific surface molecules is still under investigation. It was aimed to compare three commercially available antibodies in the detection of different surface epitopes of fibroblasts (anti-fibroblast, fibroblast activation protein α, and fibroblast surface protein). The specificity of their expression, employing fibroblast cell lines and tumor-derived fibroblasts from breast and prostate tissues was investigated. Both the established fibroblast cell line HFF-1 and ex vivo primary fibroblasts isolated from breast and prostate cancer tissues expressed the tested surface markers to different degrees. Surprisingly, those markers were expressed also by permanent cell lines of epithelial origin, both benign and cancer-derived (breast-cell lines MCF 10A, HMLE and prostate-cell lines BPH-1, DU 145, and PC-3). The expression of fibroblast activation protein α increased on the surface of previously described models of epithelial cells undergoing epithelial-to-mesenchymal transition in response to treatment with TGF-β1. To prove the co-expression of the fibroblast markers on cells of epithelial origin, we used freshly dissociated human prostate and breast cancer tissues. The results confirmed the co-expression of anti-fibroblast and fibroblast surface protein on CD31/CD45-negative/EpCAM-positive epithelial cells. In summary, our data support the findings that the tested fibroblast markers are not fibroblast specific and may be expressed also by cells of epithelial origin (e.g., cells undergoing EMT). Therefore, the expression of these markers should be interpreted with caution, and the combination of several epitopes for both positive (anti-fibroblast or fibroblast activation protein α) and negative (EpCAM) identification of fibroblasts from breast and prostate tumor tissues is advised. © 2017 International Society for Advancement of Cytometry.

Enhanced Isolation and Release of Circulating Tumor Cells Using Nanoparticle Binding and Ligand Exchange in a Microfluidic Chip

The detection of rare circulating tumor cells (CTCs) in the blood of cancer patients has the potential to be a powerful and noninvasive method for examining metastasis, evaluating prognosis, assessing tumor sensitivity to drugs, and monitoring therapeutic outcomes. In this study, we have developed an efficient strategy to isolate CTCs from the blood of breast cancer patients using a microfluidic immune-affinity approach. Additionally, to gain further access to these rare cells for downstream characterization, our strategy allows for easy detachment of the captured CTCs from the substrate without compromising cell viability or the ability to employ next generation RNA sequencing for the identification of specific breast cancer genes. To achieve this, a chemical ligand-exchange reaction was engineered to release cells attached to a gold nanoparticle coating bound to the surface of a herringbone microfluidic chip (NP-^HBCTC-Chip). Compared to the use of the unmodified ^HBCTC-Chip, our approach provides several advantages, including enhanced capture efficiency and recovery of isolated CTCs.

Epigenetic regulation of ZEB1-RAB25/ESRP1 axis plays a critical role in phenylbutyrate treatment-resistant breast cancer

Phenylbutyrate (PB) is a histone deacetylase antagonist that also exhibits antitumor activity. In this study, we used 7 breast cancer cell lines to identify biomarker candidates that predict PB sensitivity in breast cancer.

Comprehensive gene expression profiles were compared using microarrays, and the importance of the identified genes to PB sensitivity was confirmed in gene transfection experiments. CRL and MDAMB453 cells were identified as PB-sensitive, while MDAMB231 cells were PB-resistant.RAB25 and ESRP1 were identified as key regulators of PB sensitivity, while ANKD1, ETS1, PTRF, IFI16 and KIAA1199 acted as PB resistance-related genes. Expression of these genes was dramatically altered by DNA demethylation treatments. RAB25 expression inhibited IFI16 and PTRF, while ESRP1 expression suppressed ANKRD1, ETS1, and KIAA1199. Both RAB25 and ESRP1 were suppressed by ZEB1, which was in turn regulated via epigenetic mechanisms. Thus, PB sensitivity is influenced by epigenetic expression alteration of ZEB1. The genes associated with PB sensitivity are downstream targets of ZEB1. Epigenetic regulation of ZEB1 may prove valuable as a critical biomarker for predicting resistance to breast cancer therapies.

Plasma membrane ion channels and epithelial to mesenchymal transition in cancer cells

A variety of studies have suggested that epithelial to mesenchymal transition (EMT) may be important in the progression of cancer in patients through metastasis and/or therapeutic resistance. A number of pathways have been investigated in EMT in cancer cells. Recently, changes in plasma membrane ion channel expression as a consequence of EMT have been reported. Other studies have identified specific ion channels able to regulate aspects of EMT induction. The utility of plasma membrane ion channels as targets for pharmacological modulation make them attractive for therapeutic approaches to target EMT. In this review, we provide an overview of some of the key plasma membrane ion channel types and highlight some of the studies that are beginning to define changes in plasma membrane ion channels as a consequence of EMT and also their possible roles in EMT induction.

Stat3 modulates chloride channel accessory protein expression in normal and neoplastic mammary tissue

Mammary gland regression at the cessation of lactation (involution) is an exquisitely orchestrated process of cell death and tissue remodelling in which Stat3 signalling has an essential role. The involution microenvironment of the mammary gland is considered to be pro-tumourigenic and a proportion of cases of pregnancy-associated breast cancer are suggested to originate in tandem with involution. However, the apparent paradox that STAT3 is required for cell death in normal mammary gland, but is associated with breast cancer cell survival, has not been resolved. Herein, we investigate Stat3-mediated regulation of expression of members of the calcium-activated chloride channel regulator (CLCA) family of proteins during involution and mammary carcinogenesis. Using the conditionally immortal mammary epithelial cell line KIM-2, together with mice exhibiting mammary epithelial cell-specific deletion of Stat3 during lactation, we demonstrate that expression of mCLCA1 and mCLCA2 is elevated in concert with activation of Stat3. By contrast, murine CLCA5 (mCLCA5), the murine orthologue of human CLCA2, is significantly upregulated at 24, 72 and 96 h of involution in Stat3 knockout mice, suggesting a reciprocal regulation of these proteins by Stat3 in vivo. Interestingly, orthotopic tumours arising from transplantation of 4T1 murine mammary tumour cells exhibit both phosphorylated Stat3 and mCLCA5 expression. However, we demonstrate that expression is highly compartmentalized to distinct subpopulations of cells, and that Stat3 retains a suppressive effect on mCLCA5 expression in 4T1 tumour cells. These findings enhance our understanding of the regulation of CLCA channel expression both in vitro and in vivo, and in particular, demonstrate that expression of mCLCA1 and mCLCA2 during involution is profoundly dependent upon Stat3, whereas the relationship between mCLCA5 and Stat3 activity is reciprocal and restricted to different subpopulations of cells.

Ion Channels in Brain Metastasis

Breast cancer, lung cancer and melanoma exhibit a high metastatic tropism to the brain. Development of brain metastases severely worsens the prognosis of cancer patients and constrains curative treatment options. Metastasizing to the brain by cancer cells can be dissected in consecutive processes including epithelial-mesenchymal transition, evasion from the primary tumor, intravasation and circulation in the blood, extravasation across the blood-brain barrier, formation of metastatic niches, and colonization in the brain. Ion channels have been demonstrated to be aberrantly expressed in tumor cells where they regulate neoplastic transformation, malignant progression or therapy resistance. Moreover, many ion channel modulators are FDA-approved drugs and in clinical use proposing ion channels as druggable targets for future anti-cancer therapy. The present review article aims to summarize the current knowledge on the function of ion channels in the different processes of brain metastasis. The data suggest that certain channel types involving voltage-gated sodium channels, ATP-release channels, ionotropic neurotransmitter receptors and gap junction-generating connexins interfere with distinct processes of brain metastazation.

Tet-On lentiviral transductants lose inducibility when silenced for extended intervals in mammary epithelial cells

Silencing of virally transduced genes by promoter methylation and histone deacetylation has been a chronic problem both experimentally and therapeutically. We observed frequent silencing of the tetracycline-inducible Tet-On promoter borne by the Tripz lentivirus in mammary epithelial cell lines. We found that silencing could be prevented by continuous induction, but uninduced Tet-On gradually became uninducible, suggesting promoter modification. Accordingly, silencing was reversible by a common inhibitor of histone deacetylases, sodium butyrate. The effect was cell-line dependent, as HEK293 cells exhibited only moderate silencing that could be partly reversed by extended induction. These results indicate the need to test individual cell lines prior to using this system for studies that require induction after long periods of repression such as in animal models or RNA interference screens.

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Loss of inducibility of Tet-On transgenes in cancer cell lines is reported.

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Expression can be restored by an HDAC inhibitor.

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Expression can be maintained by continuous induction.

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Loss of expression is cell-line dependent.

CLCA2 Interactor EVA1 Is Required for Mammary Epithelial Cell Differentiation

CLCA2 is a p53-, p63-inducible transmembrane protein that is frequently downregulated in breast cancer. It is induced during differentiation of human mammary epithelial cells, and its knockdown causes epithelial-to-mesenchymal transition (EMT). To determine how CLCA2 promotes epithelial differentiation, we searched for interactors using membrane dihybrid screening. We discovered a strong interaction with the cell junctional protein EVA1 (Epithelial V-like Antigen 1) and confirmed it by co-immunoprecipitation. Like CLCA2, EVA1 is a type I transmembrane protein that is regulated by p53 and p63. It is thought to mediate homophilic cell-cell adhesion in diverse epithelial tissues. We found that EVA1 is frequently downregulated in breast tumors and breast cancer cell lines, especially those of mesenchymal phenotype. Moreover, knockdown of EVA1 in immortalized human mammary epithelial cells (HMEC) caused EMT, implying that EVA1 is essential for epithelial differentiation. Both EVA1 and CLCA2 co-localized with E-cadherin at cell-cell junctions. The interacting domains were delimited by deletion analysis, revealing the site of interaction to be the transmembrane segment (TMS). The primary sequence of the CLCA2 TMS was found to be conserved in CLCA2 orthologs throughout mammals, suggesting that its interaction with EVA1 co-evolved with the mammary gland. A screen for other junctional interactors revealed that CLCA2 was involved in two different complexes, one with EVA1 and ZO-1, the other with beta catenin. Overexpression of CLCA2 caused downregulation of beta catenin and beta catenin-activated genes. Thus, CLCA2 links a junctional adhesion molecule to cytosolic signaling proteins that modulate proliferation and differentiation. These results may explain how attenuation of CLCA2 causes EMT and why CLCA2 and EVA1 are frequently downregulated in metastatic breast cancer cell lines.

Microelectrode bioimpedance analysis distinguishes basal and claudin-low subtypes of triple negative breast cancer cells

Triple negative breast cancer (TNBC) is highly aggressive and has a poor prognosis when compared to other molecular subtypes. In particular, the claudin-low subtype of TNBC exhibits tumor-initiating/cancer stem cell like properties. Here, we seek to find new biomarkers to discriminate different forms of TNBC by characterizing their bioimpedance. A customized bioimpedance sensor with four identical branched microelectrodes with branch widths adjusted to accommodate spreading of individual cells was fabricated on silicon and pyrex/glass substrates. Cell analyses were performed on the silicon devices which showed somewhat improved inter-electrode and intra-device reliability. We performed detailed analysis of the bioimpedance spectra of four TNBC cell lines, comparing the peak magnitude, peak frequency and peak phase angle between claudin-low TNBC subtype represented by MDA-MB-231 and Hs578T with that of two basal cells types, the TNBC MDA-MB-468, and an immortalized non-malignant basal breast cell line, MCF-10A. The claudin-low TNBC cell lines showed significantly higher peak frequencies and peak phase angles than the properties might be useful in distinguishing the clinically significant claudin-low subtype of TNBC.

Homeostatic Signaling by Cell-Cell Junctions and Its Dysregulation during Cancer Progression

The transition of sessile epithelial cells to a migratory, mesenchymal phenotype is essential for metazoan development and tissue repair, but this program is exploited by tumor cells in order to escape the confines of the primary organ site, evade immunosurveillance, and resist chemo-radiation. In addition, epithelial-to-mesenchymal transition (EMT) confers stem-like properties that increase efficiency of colonization of distant organs. This review evaluates the role of cell–cell junctions in suppressing EMT and maintaining a quiescent epithelium. We discuss the conflicting data on junctional signaling in cancer and recent developments that resolve some of these conflicts. We focus on evidence from breast cancer, but include other organ sites where appropriate. Current and potential strategies for inhibition of EMT are discussed.

Involvement of ion channels and transporters in carcinoma angiogenesis and metastasis

Angiogenesis is a finely tuned process, which is the result of the equilibrium between pro- and antiangiogenic factors. In solid tumor angiogenesis, the balance is highly in favor of the production of new, but poorly functional blood vessels, initially intended to provide growing tumors with nutrients and oxygen. Among the numerous proteins involved in tumor development, several types of ion channels are overexpressed in tumor cells, as well as in stromal and endothelial cells. Ion channels thus actively participate in the different hallmarks of cancer, especially in tumor angiogenesis and metastasis. Indeed, from their strategic localization in the plasma membrane, ion channels are key operators of cell signaling, as they sense and respond to environmental changes. This review aims to decipher how ion channels of different families are intricately involved in the fundamental angiogenesis and metastasis hallmarks, which lead from a nascent tumor to systemic dissemination. An overview of the possible use of ion channels as therapeutic targets will also be given, showing that ion channel inhibitors or specific antibodies may provide effective tools, in the near future, in the treatment of carcinomas.

Naturally Occurring Deletion Mutants of the Pig-Specific, Intestinal Crypt Epithelial Cell Protein CLCA4b without Apparent Phenotype

The human CLCA4 (chloride channel regulator, calcium-activated) modulates the intestinal phenotype of cystic fibrosis (CF) patients via an as yet unknown pathway. With the generation of new porcine CF models, species-specific differences between human modifiers of CF and their porcine orthologs are considered critical for the translation of experimental data. Specifically, the porcine ortholog to the human CF modulator gene CLCA4 has recently been shown to be duplicated into two separate genes, CLCA4a and CLCA4b. Here, we characterize the duplication product, CLCA4b, in terms of its genomic structure, tissue and cellular expression patterns as well as its in vitro electrophysiological properties. The CLCA4b gene is a pig-specific duplication product of the CLCA4 ancestor and its protein is exclusively expressed in small and large intestinal crypt epithelial cells, a niche specifically occupied by no other porcine CLCA family member. Surprisingly, a unique deleterious mutation of the CLCA4b gene is spread among modern and ancient breeds in the pig population, but this mutation did not result in an apparent phenotype in homozygously affected animals. Electrophysiologically, neither the products of the wild type nor of the mutated CLCA4b genes were able to evoke a calcium-activated anion conductance, a consensus feature of other CLCA proteins. The apparently pig-specific duplication of the CLCA4 gene with unique expression of the CLCA4b protein variant in intestinal crypt epithelial cells where the porcine CFTR is also present raises the question of whether it may modulate the porcine CF phenotype. Moreover, the naturally occurring null variant of CLCA4b will be valuable for the understanding of CLCA protein function and their relevance in modulating the CF phenotype.

AF1q is a novel TCF7 co-factor which activates CD44 and promotes breast cancer metastasis

AF1q is an MLL fusion partner that was identified from acute myeloid leukemia (AML) patients with t (1; 11) (q21; q23) chromosomal abnormality. The function of AF1q is not yet fully known, however, elevated AF1q expression is associated with poor clinical outcomes in various malignancies. Here, we show that AF1q specifically binds to T-cell-factor-7 (TCF7) in the Wnt signaling pathway and results in transcriptional activation of CD44 as well as multiple downstream targets of the TCF7/LEF1. In addition, enhanced AF1q expression promotes breast cancer cell proliferation, migration, mammosphere formation, and chemo-resistance. In xenograft models, enforced AF1q expression in breast cancer cells also promotes liver metastasis and lung colonization. In a cohort of 63 breast cancer patients, higher percentages of AF1q-positive cancer cells in primary sites were associated with significantly poorer overall survival (OS), disease-free survival (DFS), and brain metastasis-free survival (b-MFS). Using paired primary/metastatic samples from the same patients, we demonstrate that AF1q-positive breast cancer cells become dynamically dominant in the metastatic sites compared to the primary sites. Our findings indicate that breast cancer cells with a hyperactive AF1q/TCF7/CD44 regulatory axis in the primary sites may represent "metastatic founder cells" which have invasive properties.

EMT and EGFR in CTCs cytokeratin negative non-metastatic breast cancer

Circulating tumor cells (CTCs) are frequently associated with epithelialmesenchymal transition (EMT). The objective of this study was to detect EMT phenotype through Vimentin (VIM) and Slug expression in cytokeratin (CK)-negative CTCs in non-metastatic breast cancer patients and to determine the importance of EGFR in the EMT phenomenon. In CK-negative CTCs samples, both VIM and Slug markers were co-expressed in the most of patients. Among patients EGFR+, half of them were positive for these EMT markers. Furthermore, after a systemic treatment 68% of patients switched from CK- to CK+ CTCs. In our experimental model we found that activation of EGFR signaling by its ligand on MCF-7 cells is sufficient to increase EMT phenotypes, to inhibit apoptotic events and to induce the loss of CK expression. The simultaneous detection of both EGFR and EMT markers in CTCs may improve prognostic or predictive information in patients with operable breast cancer.

The Discovery of Novel Biomarkers Improves Breast Cancer Intrinsic Subtype Prediction and Reconciles the Labels in the METABRIC Data Set

BACKGROUND

The prediction of breast cancer intrinsic subtypes has been introduced as a valuable strategy to determine patient diagnosis and prognosis, and therapy response. The PAM50 method, based on the expression levels of 50 genes, uses a single sample predictor model to assign subtype labels to samples. Intrinsic errors reported within this assay demonstrate the challenge of identifying and understanding the breast cancer groups. In this study, we aim to: a) identify novel biomarkers for subtype individuation by exploring the competence of a newly proposed method named CM1 score, and b) apply an ensemble learning, as opposed to the use of a single classifier, for sample subtype assignment. The overarching objective is to improve class prediction.

METHODS AND FINDINGS

The microarray transcriptome data sets used in this study are: the METABRIC breast cancer data recorded for over 2000 patients, and the public integrated source from ROCK database with 1570 samples. We first computed the CM1 score to identify the probes with highly discriminative patterns of expression across samples of each intrinsic subtype. We further assessed the ability of 42 selected probes on assigning correct subtype labels using 24 different classifiers from the Weka software suite. For comparison, the same method was applied on the list of 50 genes from the PAM50 method.

CONCLUSIONS

The CM1 score portrayed 30 novel biomarkers for predicting breast cancer subtypes, with the confirmation of the role of 12 well-established genes. Intrinsic subtypes assigned using the CM1 list and the ensemble of classifiers are more consistent and homogeneous than the original PAM50 labels. The new subtypes show accurate distributions of current clinical markers ER, PR and HER2, and survival curves in the METABRIC and ROCK data sets. Remarkably, the paradoxical attribution of the original labels reinforces the limitations of employing a single sample classifiers to predict breast cancer intrinsic subtypes.

Secreted CLCA1 modulates TMEM16A to activate Ca(2+)-dependent chloride currents in human cells

Calcium-activated chloride channel regulator 1 (CLCA1) activates calcium-dependent chloride currents; neither the target, nor mechanism, is known. We demonstrate that secreted CLCA1 activates calcium-dependent chloride currents in HEK293T cells in a paracrine fashion, and endogenous TMEM16A/Anoctamin1 conducts the currents. Exposure to exogenous CLCA1 increases cell surface levels of TMEM16A and cellular binding experiments indicate CLCA1 engages TMEM16A on the surface of these cells. Altogether, our data suggest that CLCA1 stabilizes TMEM16A on the cell surface, thus increasing surface expression, which results in increased calcium-dependent chloride currents. Our results identify the first Cl⁻ channel target of the CLCA family of proteins and establish CLCA1 as the first secreted direct modifier of TMEM16A activity, delineating a unique mechanism to increase currents. These results suggest cooperative roles for CLCA and TMEM16 proteins in influencing the physiology of multiple tissues, and the pathology of multiple diseases, including asthma, COPD, cystic fibrosis, and certain cancers.

DOI:http://dx.doi.org/10.7554/eLife.05875.001

Many biological processes that are important for our health involve the movement of ions into, and out of, our cells. For example, the flow of chloride ions out of cells controls the production of the sticky mucus that lines our windpipe and other airways. This mucus helps trap pollution and other foreign particles before they reach our lungs, and thus protects the lungs from harm. However in some diseases—such as cystic fibrosis and asthma—excessive amounts of thick mucus are produced; this can lead to breathing difficulties and an increased risk of infection.

Proteins belonging to the CLCA protein family were first thought to act as channels that allow chloride ions to flow through cell membranes. Later studies then revealed that these proteins are not channels; instead they trigger the movement of chloride ions across cell membranes by activating other channel proteins. However, the identity of these channel proteins was unknown, and it was unclear how CLCA proteins might activate these channels.

Sala-Rabanal, Yurtsever et al. have now shown that a member of the CLCA protein family, called CLCA1, is released from human cells and causes nearby cells to release chloride ions when the channel detects calcium ions. The movement of chloride ions triggered by CLCA1 looked very similar to the way chloride ions flow through a channel protein called TMEM16A, and so Sala-Rabanal, Yurtsever et al. asked whether these two proteins interact.

TMEM16A was discovered several years ago, but remains the only calcium-dependent chloride channel known in mammals. Sala-Rabanal, Yurtsever et al. showed that adding CLCA1 to cells caused more TMEM16A channels to appear in the cell surface membrane and thereby increased the flow of chloride ions. The CLCA protein also physically interacted with the chloride channel in the membrane to stabilize it; no other protein has been shown to regulate ion channels in this way before.

The findings of Sala-Rabanal, Yurtsever et al. provide a much clearer understanding of how the CLCA protein and the chloride channel work. Both of these proteins are known to contribute to excess mucus production in airway diseases; and both have been linked to cardiovascular diseases and certain cancers. These new findings may therefore also help researchers to target these proteins and develop treatments for these diseases.

DOI:http://dx.doi.org/10.7554/eLife.05875.002

A pseudogene-signature in glioma predicts survival

Pseudogene was recognized as a potential tumor suppressor or oncogene in varies of diseases, however its roles in glioma have not been investigated. Our study was to identify the pseudogene-signature that predicted glioma survival. Using a pseudogene-mining approach, we performed pseudogene expression profiling in 183 glioma samples from the Chinese Glioma Genome Atlas (CGGA) and set it as the training set. We found a six-pseudogene signature correlated with patients' clinical outcome via bioinformatics analyses (P ≤ 0.01), and validated it in the Repository of Molecular Brain Neoplasia Data (REMBRANDT) containing 350 cases. A formula calculating the risk score based on the six-pseudogene signature was introduced and the patients of CGGA set were classified into high-risk group and low-risk group with remarkably different survival (P < 0.001) based on their scores. The prognostic value of the signature was confirmed in the REMBRANDT set. Though the function of these pseudogenes is not clear, the identification of the prognostic pseudogenes indicated the potential roles of pseudogenes in glioma pathogenesis and they may have clinical implications in treating glioma.