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Lung cancer or pulmonary carcinoma is primarily derived from epithelial cells that are thin and line on the alveolar surfaces of the lung for gas exchange. ANO1/TMEM16A, initially identified from airway epithelial cells, is a member of Ca2+-activated Cl- channels (CaCCs) that function to regulate epithelial secretion and cell volume for maintenance of ion and tissue homeostasis. ANO1/TMEM16A has recently been shown to be highly expressed in several epithelium originated carcinomas. However, the role of ANO1 in lung cancer remains unknown. In this study, we show that inhibition of calcium-activated chloride channel ANO1/TMEM16A suppresses tumor growth and invasion in human lung cancer. ANO1 is upregulated in different human lung cancer cell lines. Knocking-down ANO1 by small hairpin RNAs inhibited proliferation, migration and invasion of GLC82 and NCI-H520 cancel cells evaluated by CCK-8, would-healing, transwell and 3D soft agar assays. ANO1 protein is overexpressed in 77.3% cases of human lung adenocarcinoma tissues detected by immunohistochemistry. Furthermore, the tumor growth in nude mice implanted with GLC82 cells was significantly suppressed by ANO1 silencing. Taken together, our findings provide evidence that ANO1 overexpression contributes to tumor growth and invasion of lung cancer; and suppressing ANO1 overexpression may have therapeutic potential in lung cancer therapy.

The TGF-β-regulated Chloride Intracellular Channel 4 (CLIC4) is an essential participant in the formation of breast cancer stroma. Here, we used data available from the TCGA and METABRIC datasets to show that CLIC4 expression was higher in breast cancers from younger women and those with early-stage metastatic disease. Elevated CLIC4 predicted poor outcome in breast cancer patients and was linked to the TGF-β pathway. However, these associations did not reveal the underlying biological contribution of CLIC4 to breast cancer progression. Constitutive ablation of host Clic4 in two murine metastatic breast cancer models nearly eliminated lung metastases without reducing primary tumor weight, while tumor cells ablated of Clic4 retained metastatic capability in wildtype hosts. Thus, CLIC4 was required for host metastatic competence. Pre- and post-metastatic proteomic analysis identified circulating pro-metastatic soluble factors that differed in tumor-bearing CLIC4-deficient and wildtype hosts. Vascular abnormalities and necrosis increased in primary tumors from CLIC4-deficient hosts. Transcriptional profiles of both primary tumors and pre-metastatic lungs of tumor-bearing CLIC4-deficient hosts were consistent with a microenvironment where inflammatory pathways were elevated. Altogether, CLIC4 expression in human breast cancers may serve as a prognostic biomarker; therapeutic targeting of CLIC4 could reduce primary tumor viability and host metastatic competence.

In myotonic dystrophy (dystrophia myotonica [DM]), an increase in the excitability of skeletal muscle leads to repetitive action potentials, stiffness, and delayed relaxation. This constellation of features, collectively known as myotonia, is associated with abnormal alternative splicing of the muscle-specific chloride channel (ClC-1) and reduced conductance of chloride ions in the sarcolemma. However, the mechanistic basis of the chloride channelopathy and its relationship to the development of myotonia are uncertain. Here we show that a morpholino antisense oligonucleotide (AON) targeting the 3' splice site of ClC-1 exon 7a reversed the defect of ClC-1 alternative splicing in 2 mouse models of DM. By repressing the inclusion of this exon, the AON restored the full-length reading frame in ClC-1 mRNA, upregulated the level of ClC-1 mRNA, increased the expression of ClC-1 protein in the surface membrane, normalized muscle ClC-1 current density and deactivation kinetics, and eliminated myotonic discharges. These observations indicate that the myotonia and chloride channelopathy observed in DM both result from abnormal alternative splicing of ClC-1 and that antisense-induced exon skipping offers a powerful method for correcting alternative splicing defects in DM.

Background Recently, many potential prognostic biomarkers for gastric cancer (GC) have been identified, but the prognosis of advanced GC patients remains poor. Chloride channels are promising cancer biomarkers, and their family member chloride channel-3 (CLC-3) is involved in multiple biological behaviors. However, whether CLC-3 is a prognostic biomarker for GC patients is rarely reported. The molecular mechanisms by which CLC-3 is regulated in GC are unclear. Methods The expression of CLC-3 and XRCC5 in human specimens was analyzed using immunohistochemistry. The primary biological functions and pathways related to CLC-3 were enriched by RNA sequencing. A 5′-biotin-labeled DNA probe with a promoter region between − 248 and + 226 was synthesized to pull down CLC-3 promoter-binding proteins. Functional studies were detected by MTS, clone formation, wound scratch, transwell, and xenograft mice model. Mechanistic studies were investigated by streptavidin-agarose-mediated DNA pull-down, mass spectrometry, ChIP, dual-luciferase reporter assay system, Co-IP, and immunofluorescence. Results The results showed that CLC-3 was overexpressed in human GC tissues and that overexpression of CLC-3 was a poor prognostic biomarker for GC patients ( P  = 0.012). Furthermore, higher expression of CLC-3 was correlated with deeper tumor invasion ( P  = 0.006) and increased lymph node metastasis ( P  = 0.016), and knockdown of CLC-3 inhibited cell proliferation and migration in vitro. In addition, X-ray repair cross-complementing 5 (XRCC5) was identified as a CLC-3 promoter-binding protein, and both CLC-3 (HR 1.671; 95% CI 1.012–2.758; P  = 0.045) and XRCC5 (HR 1.795; 95% CI 1.076–2.994; P  = 0.025) were prognostic factors of overall survival in GC patients. The in vitro and in vivo results showed that the expression and function of CLC-3 were inhibited after XRCC5 knockdown, and the inhibition effects were rescued by CLC-3 overexpression. Meanwhile, the expression and function of CLC-3 were promoted after XRCC5 overexpression, and the promotion effects were reversed by the CLC-3 knockdown. The mechanistic study revealed that knockdown of XRCC5 suppressed the binding of XRCC5 to the CLC-3 promoter and subsequent promoter activity, thus regulating CLC-3 expression at the transcriptional level by interacting with PARP1. Conclusions Our findings indicate that overexpression of CLC-3 is regulated by XRCC5 and is a poor prognostic biomarker for gastric cancer. Double targeting CLC-3 and XRCC5 may provide the promising therapeutic potential for GC treatment.

Voltage-gated CLC-1 chloride channels play a critical role in controlling the membrane excitability of skeletal muscles. Mutations in human CLC-1 channels have been linked to the hereditary muscle disorder myotonia congenita. We have previously demonstrated that disease-associated CLC-1 A531V mutant protein may fail to pass the endoplasmic reticulum quality control system and display enhanced protein degradation as well as defective membrane trafficking. Currently the molecular basis of protein degradation for CLC-1 channels is virtually unknown. Here we aim to identify the E3 ubiquitin ligase of CLC-1 channels. The protein abundance of CLC-1 was notably enhanced in the presence of MLN4924, a specific inhibitor of cullin-RING E3 ligases. Subsequent investigation with dominant-negative constructs against specific subtypes of cullin-RING E3 ligases suggested that CLC-1 seemed to serve as the substrate for cullin 4A (CUL4A) and 4B (CUL4B). Biochemical examinations further indicated that CUL4A/B, damage-specific DNA binding protein 1 (DDB1) and cereblon (CRBN) appeared to co-exist in the same protein complex with CLC-1. Moreover, suppression of CUL4A/B E3 ligase activity significantly enhanced the functional expression of the A531V mutant. Our data are consistent with the idea that the CUL4A/B-DDB1-CRBN complex catalyses the polyubiquitination and thus controls the degradation of CLC-1 channels.

Polycystic kidney diseases are characterized by the development of numerous bilateral renal cysts that continuously enlarge resulting in a decline of kidney function due to compression of intact nephrons. Cyst growth is driven by transepithelial chloride secretion which depends on both intracellular cAMP and calcium. Mechanisms that are involved in the regulation of the underlying secretory pathways remain incompletely understood. Here we show that glucose concentration has a strong impact on cyst growth of renal tubular cells within a collagen matrix as well as in embryonic kidneys deficient or competent for Pkd1 . Glucose-dependent cyst growth correlates with the transcriptional induction of the calcium-activated chloride channel anoctamin 1 (ANO1) and its increased expression in the apical membrane of cyst-forming cells. Inhibition of ANO1 with the specific inhibitor CaCCinh-AO1 significantly decreases glucose-dependent cyst growth in both models. Ussing chamber analyses revealed increased apical chloride secretion of renal tubular cells upon exposure to high glucose medium which can also be inhibited by the use of CaCCinh-AO1. These data suggest that glycemic control may help to reduce renal cyst growth in patients with polycystic kidney disease. Key message Renal cyst growth depends on glucose concentration in two in vitro cyst models. High glucose leads to upregulation of the calcium-activated chloride channel ANO1. High glucose promotes calcium-activated chloride secretion via ANO1. Glucose-dependent secretion can be inhibited by a specific inhibitor of ANO1.

Since anoctamin 1 ANO1 (TMEM16A) was found to be a molecular component of Ca(2+) -activated Cl(-) channels, its role in tumorigenesis has gained attention at a fast pace. ANO1 overexpression frequently occurs in the cancer tissues along with 11q13 chromosome amplification. Poor prognosis of many types of cancers has been closely correlated with ANO1 gene amplification and protein overexpression. ANO1 is now considered an excellent biomarker for certain cancers. Recent research suggests that it is the channel function of ANO1 that is involved in the tumorigenesis. However, how the overexpression of the functional ANO1 causes malignant transformation of tissues via signaling pathways, for example, MAPK remains to be investigated. Clarification of the reasons in future will avail to make ANO1 as a target for cancer treatment.

Myotonia congenita is a hereditary muscle disorder caused by mutations in the human voltage-gated chloride (Cl(-)) channel CLC-1. Myotonia congenita can be inherited in an autosomal recessive (Becker type) or dominant (Thomsen type) fashion. One hypothesis for myotonia congenita is that the inheritance pattern of the disease is determined by the functional consequence of the mutation on the gating of CLC-1 channels. Several disease-related mutations, however, have been shown to yield functional CLC-1 channels with no detectable gating defects. In this study, we have functionally and biochemically characterized a myotonia mutant: A531V. Despite a gating property similar to that of wild-type (WT) channels, the mutant CLC-1 channel displayed a diminished whole-cell current density and a reduction in the total protein expression level. Our biochemical analyses further demonstrated that the reduced expression of A531V can be largely attributed to an enhanced proteasomal degradation as well as a defect in protein trafficking to surface membranes. Moreover, the A531V mutant protein also appeared to be associated with excessive endosomal-lysosomal degradation. Neither the reduced protein expression nor the diminished current density was rescued by incubating A531V-expressing cells at 27°C. These results demonstrate that the molecular pathophysiology of A531V does not involve anomalous channel gating, but rather a disruption of the balance between the synthesis and degradation of the CLC-1 channel protein.

Background Gastrointestinal stromal tumors (GISTs) are characterized by mutations of KIT (v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog) or PDGFRA (platelet-derived growth factor receptor α) that may be efficiently targeted by tyrosine kinase inhibitors (TKI). Notwithstanding the early responsiveness to TKI, the majority of GISTs progress, imposing the need for alternative therapeutic strategies. DOG1 (discovered on GIST-1) shows a higher sensitivity as a diagnostic marker than KIT, however its prognostic role has been little investigated. Methods We evaluated DOG1 expression by immunohistochemistry (IHC) in 59 patients with GISTs, and correlated its levels with clinical and pathological features as well as mutational status. Kaplan-Meier analysis was also applied to assess correlations of the staining score with patient recurrence-free survival (RFS). Results DOG1 was expressed in 66 % of CD117 + GISTs and highly associated with tumor size and the rate of wild-type tumors. Kaplan-Meier survival analysis showed that a strong DOG1 expression demonstrated by IHC correlated with a worse 2-year RFS rate, suggesting its potential ability to predict GISTs with poor prognosis. Conclusions These findings suggest a prognostic role for DOG1, as well as its potential for inclusion in the criteria for risk stratification.

The murine mCLCA5 protein is a member of the chloride channel regulators, calcium-activated (CLCA) family and is suspected to play a role in airway mucus cell differentiation. Although mCLCA5 mRNA was previously found in total lung extracts, the expressing cells and functions in the naive murine respiratory tract are unknown. Therefore, mCLCA5 protein expression was identified by immunohistochemistry and confocal laser scanning microscopy using entire lung sections of naive mice. Moreover, we determined mRNA levels of functionally related genes (mClca3, mClca5, Muc5ac and Muc5b) and quantified mCLCA5-, mCLCA3- and CC10-positive cells and periodic acid-Schiff-positive mucus cells in naive, PBS-treated or Staphylococcus aureus -infected mice. We also investigated mCLCA5 protein expression in Streptococcus pneumoniae and influenza virus lung infection models. Finally, we determined species-specific differences in the expression patterns of the murine mCLCA5 and its human and porcine orthologs, hCLCA2 and pCLCA2. The mCLCA5 protein is uniquely expressed in highly select bronchial epithelial cells and submucosal glands in naive mice, consistent with anatomical locations of progenitor cell niches. Under conditions of challenge (PBS, S. aureus , S. pneumoniae , influenza virus), mRNA and protein expression strongly declined with protein recovery only in models retaining intact epithelial cells. In contrast to mice, human and porcine bronchial epithelial cells do not express their respective mCLCA5 orthologs and submucosal glands had fewer expressing cells, indicative of fundamental differences in mice versus humans and pigs.