Expression of aquaporin 5 (AQP5) promotes tumor invasion in human non small cell lung cancer

The role of Aquaporins in tumorigenesis: implications for therapeutic development

Aquaporins (AQPs) are ubiquitous channel proteins that play a critical role in the homeostasis of the cellular environment by allowing the transit of water, chemicals, and ions. They can be found in many different types of cells and organs, including the lungs, eyes, brain, glands, and blood vessels. By controlling the osmotic water flux in processes like cell growth, energy metabolism, migration, adhesion, and proliferation, AQPs are capable of exerting their regulatory influence over a wide range of cellular processes. Tumour cells of varying sources express AQPs significantly, especially in malignant tumours with a high propensity for metastasis. New insights into the roles of AQPs in cell migration and proliferation reinforce the notion that AQPs are crucial players in tumour biology. AQPs have recently been shown to be a powerful tool in the fight against pathogenic antibodies and metastatic cell migration, despite the fact that the molecular processes of aquaporins in pathology are not entirely established. In this review, we shall discuss the several ways in which AQPs are expressed in the body, the unique roles they play in tumorigenesis, and the novel therapeutic approaches that could be adopted to treat carcinoma.

Genome-wide expression profiling reveals novel biomarkers in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most aggressive and frequent malignancy detected among women worldwide. The pathophysiology of OC should, therefore be better understood to identify diagnostic, prognostic, and predictive novel biomarkers necessary for early detection, management, and prognostication. In this study, we aimed to investigate transcriptomic landscape and biomarker through RNA-seq data analysis. Further analysis by Protein Protein network identified top 10 Differentially Expressed Genes (DEGs). KEGG pathway enrichment analysis revealed the significant enrichment of DEGs in basal cell carcinoma, cell cycle and FoxO signalling pathway. The RNA-seq results of 10 DEGs were validated by QRT-PCR and TCGA database. Correlation studies were also performed between gene expression and clinical characteristics followed by survival analysis. Finally, 8 DEGs (CDKN1A, BCL6, CDC45, WNT2, TLR5, AQP5) including two novel DEGs (CSN1S1 and NKILA) were identified showing significant correlations with EOC characteristics. These may serve as interesting biomarkers and novel treatment targets and warrant further investigation into the functional outcome of EOC.

Aquaporin water channels: roles beyond renal water handling

Aquaporin (AQP) water channels are pivotal to renal water handling and therefore in the regulation of body water homeostasis. However, beyond the kidney, AQPs facilitate water reabsorption and secretion in other cells and tissues, including sweat and salivary glands and the gastrointestinal tract. A growing body of evidence has also revealed that AQPs not only facilitate the transport of water but also the transport of several small molecules and gases such as glycerol, H2O2, ions and CO2. Moreover, AQPs are increasingly understood to contribute to various cellular processes, including cellular migration, adhesion and polarity, and to act upstream of several intracellular and intercellular signalling pathways to regulate processes such as cell proliferation, apoptosis and cell invasiveness. Of note, several AQPs are highly expressed in multiple cancers, where their expression can correlate with the spread of cancerous cells to lymph nodes and alter the response of cancers to conventional chemotherapeutics. These data suggest that AQPs have diverse roles in various homeostatic and physiological systems and may be exploited for prognostics and therapeutic interventions.

The cell polarity protein Scribble is downregulated by the water channel aquaporin-5 in breast cancer cells

Breast carcinomas originate from cells in the terminal duct-lobular unit. Carcinomas are associated with increased cell proliferation and migration, altered cellular adhesion, as well as loss of epithelial polarity. In breast cancer, aberrant and high levels of aquaporin-5 (AQP5) are associated with increased metastasis, poor prognosis, and cancer recurrence. AQP5 increases the proliferation and migration of cancer cells, and ectopic expression of AQP5 in normal epithelial cells reduces cell-cell adhesion and increases cell detachment and dissemination from migrating cell sheets, the latter via AQP5-mediated activation of the Ras pathway. Here, we investigated if AQP5 also affects cellular polarity by examining the relationship between the essential polarity protein Scribble and AQP5. In tissue samples from invasive lobular and ductal carcinomas, the majority of cells with high AQP5 expression displayed low Scribble levels, indicating an inverse relationship. Probing for interactions via a Glutathione S-transferase pull-down experiment revealed that AQP5 and Scribble interacted. Moreover, overexpression of AQP5 in the breast cancer cell line MCF7 reduced both size and circularity of three-dimensional (3-D) spheroids and induced cell detachment and dissemination from migrating cell sheets. In addition, Scribble levels were reduced. An AQP5 mutant cell line, which cannot activate Ras (AQP5^S156A) signaling, displayed unchanged spheroid size and circularity and an intermediate level of Scribble, indicating that the effect of AQP5 on Scribble is, at least in part, dependent on AQP5-mediated activation of Ras. Thus, our results suggest that high AQP5 expression negatively regulates the essential polarity protein Scribble and thus, can affect cellular polarity in breast cancer.

Aquaporin-mediated dysregulation of cell migration in disease states

Dysregulated cell migration and invasion are hallmarks of many disease states. This dysregulated migratory behavior is influenced by the changes in expression of aquaporins (AQPs) that occur during pathogenesis, including conditions such as cancer, endometriosis, and arthritis. The ubiquitous function of AQPs in migration of diseased cells makes them a crucial target for potential therapeutics; this possibility has led to extensive research into the specific mechanisms underlying AQP-mediated diseased cell migration. The functions of AQPs depend on a diverse set of variables including cell type, AQP isoform, disease state, cell microenvironments, and even the subcellular localization of AQPs. To consolidate the considerable work that has been conducted across these numerous variables, here we summarize and review the last decade's research covering the role of AQPs in the migration and invasion of cells in diseased states.

Aquaporin 5 (AQP5) expression in breast cancer and its clinicopathological characteristics

The role of aquaporin water channels (AQPs) has become an area of great interest in human carcinogenesis. In this report, we have demonstrated the expression of AQP5 in breast cancer by analyzing 591 tissue samples with 7-year follow-ups. By immunochemistry analysis, AQP5 overexpression was observed in 36% (212/591 cases). Then, we have focused on the clinicopathologic variables among cancer tissue samples with strong AQP5 expression (3+ expression, 60/591 cases). The strong AQP5 expression was positively correlated with tumor grade in BCs (p<0.001) and was more frequent in ER/PR-negative BCs than positive ones (14.9% vs. 3.3% and 13.1% vs. 4.8%, respectively, both p<0.001), while Her2/neu-positive status was positively correlated with strong expression of AQP5 (p = 0.005). Of note, breast cancer patients with positive AQP expression (212/591 cases) showed a less favorable breast cancer specific survival rate over 7 years of follow and we further conclude that AQP5 expression is an independent molecular marker associated with worse clinical outcomes. By fluorescence in situ hybridization (FISH), we have identified evidence of gene amplification in 3 of 30 readable breast cancer and further conclude that, in breast cancer, at least some part of AQP5 overexpression is associated with an aberration in the genome level.

Aquaporins in Cancer Biology

Aquaporins (AQPs) are a family of transmembrane water channel proteins, which were initially characterized as a novel protein family that plays a vital role in transcellular and transepithelial water movement. AQP1, AQP2, AQP4, AQP5, and AQP8 are primarily water selective, whereas AQP3, AQP7, AQP9, and AQP10 (called “aqua-glyceroporins”) also transport glycerol and other small solutes. Recently, multiple reports have suggested that AQPs have important roles in cancer cell growth, migration, invasion, and angiogenesis, each of which is important in human carcinogenesis. Here, we review recent data concerning the involvement of AQPs in tumor growth, angiogenesis, and metastasis and explore the expression profiles from various resected cancer samples to further dissect the underlying molecular mechanisms. Moreover, we discuss the potential role of AQPs during the development of genomic instability and performed modeling to describe the integration of binding between AQPs with various SH3 domain binning adaptor molecules. Throughout review and discussion of numerous reports, we have tried to provide key evidence that AQPs play key roles in tumor biology, which may provide a unique opportunity in designing a novel class of anti-tumor agents.

Aquaporin-5 in breast cancer

The water channel aquaporin‐5 (AQP5) is essential in transepithelial water transport in secretory glands. AQP5 is ectopically overexpressed in breast cancer, where expression is associated with lymph node metastasis and poor prognosis. Besides the role in water transport, AQP5 has been found to play a role in cancer metastasis, migration, and proliferation. AQP5 has also been shown to be involved in the dysregulation of epithelial cell–cell adhesion; frequently observed in cancers. Insight into the underlying molecular mechanisms of how AQP5 contributes to cancer development and progression is essential for potentially implementing AQP5 as a prognostic biomarker and to develop targeted intervention strategies for the treatment of breast cancer patients.

The Characterization of Structure and Prediction for Aquaporin in Tumour Progression by Machine Learning

Recurrence and new cases of cancer constitute a challenging human health problem. Aquaporins (AQPs) can be expressed in many types of tumours, including the brain, breast, pancreas, colon, skin, ovaries, and lungs, and the histological grade of cancer is positively correlated with AQP expression. Therefore, the identification of aquaporins is an area to explore. Computational tools play an important role in aquaporin identification. In this research, we propose reliable, accurate and automated sequence predictor iAQPs-RF to identify AQPs. In this study, the feature extraction method was 188D (global protein sequence descriptor, GPSD). Six common classifiers, including random forest (RF), NaiveBayes (NB), support vector machine (SVM), XGBoost, logistic regression (LR) and decision tree (DT), were used for AQP classification. The classification results show that the random forest (RF) algorithm is the most suitable machine learning algorithm, and the accuracy was 97.689%. Analysis of Variance (ANOVA) was used to analyse these characteristics. Feature rank based on the ANOVA method and IFS strategy was applied to search for the optimal features. The classification results suggest that the 26th feature (neutral/hydrophobic) and 21st feature (hydrophobic) are the two most powerful and informative features that distinguish AQPs from non-AQPs. Previous studies reported that plasma membrane proteins have hydrophobic characteristics. Aquaporin subcellular localization prediction showed that all aquaporins were plasma membrane proteins with highly conserved transmembrane structures. In addition, the 3D structure of aquaporins was consistent with the localization results. Therefore, these studies confirmed that aquaporins possess hydrophobic properties. Although aquaporins are highly conserved transmembrane structures, the phylogenetic tree shows the diversity of aquaporins during evolution. The PCA showed that positive and negative samples were well separated by 54D features, indicating that the 54D feature can effectively classify aquaporins. The online prediction server is accessible at http://lab.malab.cn/∼acy/iAQP.

A Repurposed Drug Screen for Compounds Regulating Aquaporin 5 Stability in Lung Epithelial Cells

Aquaporin 5 (AQP5) is expressed in several cell types in the lung and regulates water transport, which contributes to barrier function during injury and the composition of glandular secretions. Reduced AQP5 expression is associated with barrier dysfunction during acute lung injury, and strategies to enhance its expression are associated with favorable phenotypes. Thus, pharmacologically enhancing AQP5 expression could be beneficial. Here, we optimized a high-throughput assay designed to detect AQP5 abundance using a cell line stably expressing bioluminescent-tagged AQP5. We then screened a library of 1153 compounds composed of FDA-approved drugs for their effects on AQP5 abundance. We show compounds Niclosamide, Panobinostat, and Candesartan Celexitil increased AQP5 abundance, and show that Niclosamide has favorable cellular toxicity profiles. We determine that AQP5 levels are regulated in part by ubiquitination and proteasomal degradation in lung epithelial cells, and mechanistically Niclosamide increases AQP5 levels by reducing AQP5 ubiquitination and proteasomal degradation. Functionally, Niclosamide stabilized AQP5 levels in response to hypotonic stress, a stimulus known to reduce AQP5 levels. In complementary assays, Niclosamide increased endogenous AQP5 in both A549 cells and in primary, polarized human bronchial epithelial cells compared to control-treated cells. Further, we measured rapid cell volume changes in A549 cells in response to osmotic stress, an effect controlled by aquaporin channels. Niclosamide-treated A549 cell volume changes occurred more rapidly compared to control-treated cells, suggesting that increased Niclosamide-mediated increases in AQP5 expression affects functional water transport. Taken together, we describe a strategy to identify repurposed compounds for their effect on AQP5 protein abundance. We validated the effects of Niclosamide on endogenous AQP5 levels and in regulating cell-volume changes in response to tonicity changes. Our findings highlight a unique approach to screen for drug effects on protein abundance, and our workflow can be applied broadly to study compound effects on protein abundance in lung epithelial cells.

Aquaporin 5 Facilitates Corneal Epithelial Wound Healing and Nerve Regeneration by Reactivating Akt Signaling Pathway

Aquaporins (AQPs) are normally expressed in the corneal epithelium. The aim of this study was to determine whether AQP5 played a role in corneal epithelial wound healing. AQP5 knockout (AQP5^-/-) mice were constructed using CRISPR/Cas9 technology. A corneal wound healing model was performed using epithelial debridement on corneas. The time to corneal epithelial and nerve regeneration was significantly delayed in the AQP5^-/- mice. Reduced Ki-67-positive cells and nerve growth factor (NGF) expression were confirmed in the AQP5^-/- mice during healing. The epithelial and nerve regeneration rates were significantly promoted in the AQP5^-/- mice by treatment with NGF, which was accompanied by recovered levels of phosphorylated Akt. NGF treatment also improved the recovery of corneal nerve fiber density and sensitivity in the AQP5^-/- mice. However, the promotion of NGF induced corneal epithelial and nerve regeneration rates, and Akt reactivation was reversed by Akt inhibitor. The significant impairment of corneal wound healing in the AQP5^-/- mice resulted from distinct defects in corneal epithelial cell proliferation and nerve regeneration. The results provided evidence for the involvement of aquaporin in cell proliferation and suggested that AQP5 induction could be a potential therapy for accelerating the resurfacing of corneal defects.

Continuous Long-Term Exposure to Low Concentrations of MWCNTs Induces an Epithelial-Mesenchymal Transition in BEAS-2B Cells

In the field of nanotechnology, the use of multi-walled carbon nanotubes (MWCNTs) is growing. Pulmonary exposure during their production, use, and handling is raising concerns about their potential adverse health effects. The purpose of this study is to assess how the physical characteristics of MWCNTs, such as diameter and/or length, can play a role in cellular toxicity. Our experimental design is based on the treatment of human bronchial epithelial cells (BEAS-2B) for six weeks with low concentrations (0.125-1 µg/cm2) of MWCNTs having opposite characteristics: NM-403 and Mitsui-7. Following treatment with both MWCNTs, we observed an increase in mitotic abnormalities and micronucleus-positive cells. The cytotoxic effect was delayed in cells treated with NM-403 compared to Mitsui-7. After 4-6 weeks of treatment, a clear cellular morphological change from epithelial to fibroblast-like phenotype was noted, together with a change in the cell population composition. BEAS-2B cells underwent a conversion from the epithelial to mesenchymal state as we observed a decrease in the epithelial marker E-cadherin and an increased expression of mesenchymal markers N-cadherin, Vimentin, and Fibronectin. After four weeks of recovery, we showed that the induced epithelial-mesenchymal transition is reversible, and that the degree of reversibility depends on the MWCNT.

AQP3 Increases Intercellular Cohesion in NSCLC A549 Cell Spheroids through Exploratory Cell Protrusions

Tumor cell aggregation is critical for cell survival following the loss of extracellular matrix attachment and dissemination. However, the underlying mechanotransduction of clustering solitary tumor cells is poorly understood, especially in non-small cell lung cancers (NSCLC). Here, we examined whether cell surface protrusions played an important role in facilitating the physical contact between floating cells detached from a substrate. We employed poly-2-hydroxyethyl methacrylate-based 3D culture methods to mimic in vivo tumor cell cluster formation. The suprastructural analysis of human NSCLC A549 cell spheroids showed that finger-like protrusions clung together via the actin cytoskeleton. Time-lapse holotomography demonstrated that the finger-like protrusions of free-floating cells in 3D culture displayed exploratory coalescence. Global gene expression analysis demonstrated that the genes in the organic hydroxyl transport were particularly enriched in the A549 cell spheroids. Particularly, the knockdown of the water channel aquaporin 3 gene (AQP3) impaired multicellular aggregate formation in 3D culture through the rearrangement of the actomyosin cytoskeleton. Moreover, the cells with reduced levels of AQP3 decreased their transmigration. Overall, these data indicate that cell detachment-upregulated AQP3 contributes to cell surface protrusions through actomyosin cytoskeleton remodeling, causing the aggressive aggregation of free-floating cells dependent on the property of the substratum and collective metastasis.

Aquaporin water channels as regulators of cell-cell adhesion proteins

Aquaporin (AQP) water channels facilitate passive transport of water across cellular membranes following an osmotic gradient. AQPs are expressed in a multitude of epithelia, endothelia, and other cell types where they play important roles in physiology, especially in the regulation of body water homeostasis, skin hydration, and fat metabolism. AQP dysregulation is associated with many pathophysiological conditions, including nephrogenic diabetes insipidus, chronic kidney disease, and congestive heart failure. Moreover, AQPs have emerged as major players in a multitude of cancers where high expression correlates with metastasis and poor prognosis. Besides water transport, AQPs have been shown to be involved in cellular signaling, cell migration, cell proliferation, and regulation of junctional proteins involved in cell-cell adhesion; all cellular processes which are dysregulated in cancer. This review focuses on AQPs as regulators of junctional proteins involved in cell-cell adhesion.

Deciphering the structure, function, expression and regulation of aquaporin-5 in cancer evolution

In recent years, the morbidity rate resulting from numerous types of malignant tumor has increased annually, and the treatment of tumors has been attracting an increasing amount of attention. A number of recent studies have revealed that the water channel protein aquaporin-5 (AQP5) has become a major player in multiple types of cancer. AQP5 is abnormally expressed in a variety of tumor tissues or cells and has multiple effects on certain biological functions of tumors, such as regulating the proliferation, apoptosis and migration of tumor cells. It has been suggested that AQP5 may play an important role in the process of tumor development, opening up a new field of tumor research. The present review highlighted the structure of AQP5 and its role in tumor progression. Furthermore, the expression of AQP5 in different malignant neoplasms was summarized. In addition, the influence of not only drugs, but also different compounds on AQP5 were summarized. In conclusion, according to the findings in the present review, AQP5 has potential as a novel therapeutic target in human cancer, and other AQPs should be similarly investigated.

Aquaporins and diseases pathogenesis: From trivial to undeniable involvements, a disease-based point of view

Aquaporins (AQPs), as transmembrane proteins, were primarily identified as water channels with the ability of regulating the transmission of water, glycerol, urea, and other small-sized molecules. The classic view of AQPs involvement in therapeutic plan restricted them and their regulators into managing only a narrow spectrum of the diseases such as diabetes insipidus and the syndrome of inappropriate ADH secretion. However, further investigations performed, especially in the third millennium, has found that their cooperation in water transmission control can be manipulated to handle other burden-imposing diseases such as cirrhosis, heart failure, Meniere's disease, cancer, bullous pemphigoid, eczema, and Sjögren's syndrome.

Aquaporin-5 regulation of cell-cell adhesion proteins: an elusive "tail" story

Aquaporins (AQPs) are water channels that facilitate transport of water across cellular membranes. AQPs are overexpressed in several cancers. Especially in breast cancer, AQP5 overexpression correlates with spread to lymph nodes and poor prognosis. Previously, we showed that AQP5 expression reduced cell-cell adhesion by reducing levels of adherens and tight-junction proteins (e.g., ZO-1, plakoglobin, and β-catenin) at the actual junctions. Here, we show that, when targeted to the plasma membrane, the AQP5 COOH-terminal tail domain regulated junctional proteins and, moreover, that AQP5 interacted with ZO-1, plakoglobin, β-catenin, and desmoglein-2, which were all reduced at junctions upon AQP5 overexpression. Thus, our data suggest that AQP5 mediates the effect on cell-cell adhesion via interactions with junctional proteins independently of AQP5-mediated water transport. AQP5 overexpression in cancers may thus contribute to carcinogenesis and cancer spread by two independent mechanisms: reduced cell-cell adhesion, a characteristic of epithelial-mesenchymal transition, and increased cell migration capacity via water transport.

Aquaporins in lung health and disease: Emerging roles, regulation, and clinical implications

Aquaporins (AQPs) aka water channels are a family of conserved transmembrane proteins (~30 kDa monomers) expressed in various organ systems. Of the 13 AQPs (AQP0 through AQP12) in the human body, four (AQPs 1, 3, 4, and 5) are expressed in the respiratory system. These channels are conventionally known for mediating transcellular fluid movements. Certain AQPs (aquaglyceroporins) have the capability to transport glycerol and potentially other solutes. There is an emerging body of literature unveiling the non-conventional roles of AQPs such as in cell proliferation and migration, gas permeation, signal potentiation, etc. Initial gene knock-out studies established a physiological role for lung AQPs, particularly AQP5, in maintaining homeostasis, by mediating fluid secretion from submucosal glands onto the airway surface liquid (ASL) lining. Subsequent studies have highlighted the functional significance of AQPs, particularly AQP1 and AQP5 in lung pathophysiology and diseases, including but not limited to chronic and acute lung injury, chronic obstructive pulmonary disease (COPD), other inflammatory lung conditions, and lung cancer. AQP1 has been suggested as a potential prognostic marker for malignant mesothelioma. Recent efforts are directed toward exploiting AQPs as targets for diagnosis, prevention, intervention, and/or treatment of various lung conditions. Emerging information on regulatory pathways and directed mechanistic research are posited to unravel novel strategies for these clinical implications. Future considerations should focus on development of AQP inhibitors, blockers, and modulators for therapeutic needs, and better understanding the role of lung-specific AQPs in inter-individual susceptibility to chronic lung diseases such as COPD and cancer.

Differential expression and inhibitory effects of aquaporins on the development of adenomyosis

Aquaporin 2 (AQP2), AQP5 and AQP8 participate in adenomyosis (AM). Ηowever, the roles of these three molecules in AM have not been fully elucidated. In the present study, Institute of Cancer Research female mice were used to establish a model of AM. Subsequently, the endometrial tissues of the mice were observed by hematoxylin-eosin staining, and AM severity, uterus diameter, uterus index, ovary index and numbers of nodules on the uterine surface were evaluated and counted. In addition, eutopic and ectopic endometrial stromal cells (ESCs) were isolated from eutopic and ectopic endometrial samples derived from patients with AM and were then identified by immunofluorescence. The viability, and migratory and invasive ability of ESCs transfected with small interfering RNA targeting AQP5 (siAQP5) were determined by Cell Counting Κit-8, scratch wound-healing and Transwell assays, respectively. Reverse transcription-quantitative polymerase chain reaction was performed to determine the mRNA expression levels of AQP5, epithelial-mesenchymal transition (EMT)-related genes (E-and N-cadherin), matrix metalloproteinase (MMP)-2 and −9. Protein expression levels of AQP2, AQP5, AQP8, E-, N-cadherin, MMP-2 and −9 were detected by western blotting. AM severity and uterus index were higher, and there were a greater number of nodules on the uterine surface in the AM group compared with the sham group. AQP2, AQP5 and AQP8 proteins were highly expressed in eutopic and ectopic endometrium of the AM group, and AQP5 was more highly expressed than AQP2 or AQP8. In addition, the data showed that Vimentin was positively expressed in ESCs, and that siAQP5 suppressed the mRNA expression levels of AQP5, cell viability, migration, invasion, EMT and MMP-2 and −9 expression in ESCs. In conclusion, AQP2, AQP5 and AQP8 were highly expressed in eutopic and ectopic endometrium. Notably, AQP5 silencing may suppress AM by inhibiting viability, migration, invasion, EMT, and MMP-2 and −9 expression in ESCs.

Combined Systematic Review and Transcriptomic Analyses of Mammalian Aquaporin Classes 1 to 10 as Biomarkers and Prognostic Indicators in Diverse Cancers

Aquaporin (AQP) channels enable regulated transport of water and solutes essential for fluid homeostasis, but they are gaining attention as targets for anticancer therapies. Patterns of AQP expression and survival rates for patients were evaluated by systematic review (PubMed and Embase) and transcriptomic analyses of RNAseq data (Human Protein Atlas database). Meta-analyses confirmed predominantly negative associations between AQP protein and RNA expression levels and patient survival times, most notably for AQP1 in lung, breast and prostate cancers; AQP3 in esophageal, liver and breast cancers; and AQP9 in liver cancer. Patterns of AQP expression were clustered for groups of cancers and associated with risk of death. A quantitative transcriptomic analysis of AQP1-10 in human cancer biopsies similarly showed that increased transcript levels of AQPs 1, 3, 5 and 9 were most frequently associated with poor survival. Unexpectedly, increased AQP7 and AQP8 levels were associated with better survival times in glioma, ovarian and endometrial cancers, and increased AQP11 with better survival in colorectal and breast cancers. Although molecular mechanisms of aquaporins in pathology or protection remain to be fully defined, results here support the hypothesis that overexpression of selected classes of AQPs differentially augments cancer progression. Beyond fluid homeostasis, potential roles for AQPs in cancers (suggested from an expanding appreciation of their functions in normal tissues) include cell motility, membrane process extension, transport of signaling molecules, control of proliferation and apoptosis, increased mechanical compliance, and gas exchange. AQP expression also has been linked to differences in sensitivity to chemotherapy treatments, suggesting possible roles as biomarkers for personalized treatments. Development of AQP pharmacological modulators, administered in cancer-specific combinations, might inspire new interventions for controlling malignant carcinomas.

Dynamics of Salivary Gland AQP5 under Normal and Pathologic Conditions

AQP5 plays an important role in the salivary gland function. The mRNA and protein for aquaporin 5 (AQP5) are expressed in the acini from embryonic days E13-16 and E17-18, respectively and for entire postnatal days. Ligation-reopening of main excretory duct induces changes in the AQP5 level which would give an insight for mechanism of regeneration/self-duplication of acinar cells. The AQP5 level in the submandibular gland (SMG) decreases by chorda tympani denervation (CTD) via activation autophagosome, suggesting that its level in the SMG under normal condition is maintained by parasympathetic nerve. Isoproterenol (IPR), a β-adrenergic agonist, raised the levels of membrane AQP5 protein and its mRNA in the parotid gland (PG), suggesting coupling of the AQP5 dynamic and amylase secretion-restoration cycle. In the PG, lipopolysaccharide (LPS) is shown to activate mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signalings and potentially downregulate AQP5 expression via cross coupling of activator protein-1 (AP-1) and NF-κB. In most species, Ser-156 and Thr-259 of AQP5 are experimentally phosphorylated, which is enhanced by cAMP analogues and forskolin. cAMP-dependent phosphorylation of AQP5 does not seem to be markedly involved in regulation of its intracellular trafficking but seems to play a role in its constitutive expression and lateral diffusion in the cell membrane. Additionally, Ser-156 phosphorylation may be important for cancer development.

AQP5 enriches for stem cells and cancer origins in the distal stomach

LGR5 marks resident adult epithelial stem cells at the gland base in the mouse pyloric stomach¹, but the identity of the equivalent human stem cell population remains unknown owing to a lack of surface markers that facilitate its prospective isolation and validation. In mouse models of intestinal cancer, LGR5⁺ intestinal stem cells are major sources of cancer following hyperactivation of the WNT pathway². However, the contribution of pyloric LGR5⁺ stem cells to gastric cancer following dysregulation of the WNT pathway-a frequent event in gastric cancer in humans³-is unknown. Here we use comparative profiling of LGR5⁺ stem cell populations along the mouse gastrointestinal tract to identify, and then functionally validate, the membrane protein AQP5 as a marker that enriches for mouse and human adult pyloric stem cells. We show that stem cells within the AQP5⁺ compartment are a source of WNT-driven, invasive gastric cancer in vivo, using newly generated Aqp5-creERT2 mouse models. Additionally, tumour-resident AQP5⁺ cells can selectively initiate organoid growth in vitro, which indicates that this population contains potential cancer stem cells. In humans, AQP5 is frequently expressed in primary intestinal and diffuse subtypes of gastric cancer (and in metastases of these subtypes), and often displays altered cellular localization compared with healthy tissue. These newly identified markers and mouse models will be an invaluable resource for deciphering the early formation of gastric cancer, and for isolating and characterizing human-stomach stem cells as a prerequisite for harnessing the regenerative-medicine potential of these cells in the clinic.

Aquaporin 5 promotes tumor migration and angiogenesis in non-small cell lung cancer cell line H1299

Non-small cell lung cancer (NSCLC) constitutes the majority of all lung-cancer cases. Aquaporin 5 (AQP5) may be involved in NSCLC by promoting lung-cancer initiation and progression. The present study aimed to determine the role of AQP5 in migration and angiogenesis using NSCLC cells and HUVECs. AQPs 1, 3, 4, 5, 8 and 9 were screened in the NSCLC cell line H1299, and the present results showed that AQP5 mRNA was upregulated compared with the other AQP genes. At the protein level, AQP5 was significantly increased in H1299 cells compared with 16HBE cells. AQP5 knockdown in H1299 cells significantly decreased cell migration compared with untransfected cells, as demonstrated by both Transwell and wound closure assays. The present study further investigated H1299 ability to promote HUVEC vascularisation. The supernatants of both transfected and untransfected H1299 cells were used as conditioned medium for HUVECs, and tube formation was measured. The supernatant of AQP5-downregulated cells exhibited significantly low tube formation potential compared with untransfected cells. Similarly, vascular endothelial growth factor was significantly increased in control cells (si-NC) compared with cells transfected with small interfering RNA targeting AQP5. The present study found that AQP5 downregulation significantly decreased the phosphorylation level of epidermal growth factor receptor and the activity of the ERK1/2 pathway. In summary, the present study suggested that AQP5 influenced migration and angiogenesis in NSCLCs in vitro and may potentially exhibit similar in vivo effects.

Function of ion transporters in maintaining acid-base homeostasis of the mammary gland and the pathophysiological role in breast cancer

The incidence of breast cancer is increasing year by year, and the pathogenesis is still unclear. Studies have shown that the high metabolism of solid tumors leads to an increase in hypoxia, glycolysis, production of lactic acid and carbonic acid, and extracellular acidification; a harsh microenvironment; and ultimately to tumor cell death. Approximately 50% of locally advanced breast cancers exhibit hypoxia and/or local hypoxia, and acid-base regulatory proteins play an important role in regulating milk secretion and maintaining mammary gland physiological function. Therefore, ion transporters have gradually become a hot topic in mammary gland and breast cancer research. This review focuses on the research progress of ion transporters in mammary glands and breast cancer. We hope to provide new targets for the treatment and prognosis of breast cancer.

Quantitative screening of the effects of hyper-osmotic stress on cancer cells cultured in 2- or 3-dimensional settings

The maintenance of precise cell volume is critical for cell survival. Changes in extracellular osmolarity affect cell volume and may impact various cellular processes such as mitosis, mitochondrial functions, DNA repair as well as cell migration and proliferation. Much of what we know about the mechanisms of cell osmoregulation comes from in vitro two-dimensional (2D) assays that are less physiologically relevant than three-dimensional (3D) in vitro or in vivo settings. Here, we developed a microfluidic model to study the impact of hyper-osmotic stress on the migration, proliferation and ion channel/transporter expression changes of three metastatic cell lines (MDA-MB-231, A549, T24) in 2D versus 3D environments. We observed a global decrease in cell migration and proliferation upon hyper-osmotic stress treatment, with similar responses between 2D and 3D conditions. Specific ion channels/aquaporins are over-expressed in metastatic cells and play a central role during osmo-regulation. Therefore, the effects of hyper-osmotic stress on two transporters, aquaporin 5 (AQP5) and the transient receptor potential cation channel (TRPV4), was investigated. While hyper-osmotic stress had no major impact on the transporters of cells cultured in 2D, cells embedded in collagen gel (3D) decreased their AQP5 expression and exhibited a reduction in intra-cellular translocation of TRPV4. Furthermore, cell dispersion from T24 aggregates embedded in 3D collagen gel decreased with higher levels of hyper-osmotic stress. In conclusion, this study provides evidence on the impact of hyper-osmotic stress on various aspects of metastatic cell progression and highlights the importance of having a 3D cell culture platform in investigating molecular players involved in cancer cell migration.

Distinct signatures of lung cancer types: aberrant mucin O-glycosylation and compromised immune response

BACKGROUND

Genomic initiatives such as The Cancer Genome Atlas (TCGA) contain data from -omics profiling of thousands of tumor samples, which may be used to decipher cancer signaling, and related alterations. Managing and analyzing data from large-scale projects, such as TCGA, is a demanding task. It is difficult to dissect the high complexity hidden in genomic data and to account for inter-tumor heterogeneity adequately.

METHODS

In this study, we used a robust statistical framework along with the integration of diverse bioinformatic tools to analyze next-generation sequencing data from more than 1000 patients from two different lung cancer subtypes, i.e., the lung adenocarcinoma (LUAD) and the squamous cell carcinoma (LUSC).

RESULTS

We used the gene expression data to identify co-expression modules and differentially expressed genes to discriminate between LUAD and LUSC. We identified a group of genes which could act as specific oncogenes or tumor suppressor genes in one of the two lung cancer types, along with two dual role genes. Our results have been validated against other transcriptomics data of lung cancer patients.

CONCLUSIONS

Our integrative approach allowed us to identify two key features: a substantial up-regulation of genes involved in O-glycosylation of mucins in LUAD, and a compromised immune response in LUSC. The immune-profile associated with LUSC might be linked to the activation of three oncogenic pathways, which promote the evasion of the antitumor immune response. Collectively, our results provide new future directions for the design of target therapies in lung cancer.

Aquaporins 1, 3 and 5 in Different Tumors, their Expression, Prognosis Value and Role as New Therapeutic Targets

All different types of metabolism of tumors are dependent on the flow of water molecules through the biological membrane, where fluid transfer interceded by aquaporins (AQPs) are the basis means for water entrance into the cells or outside them. Aquaporins play other roles including cellular migration, cellular expansion and cellular adhesion facilitation. Therefore, regulators of AQPs may be useful anticancer agents. Medline, Scopus, Embase, and Web of Sciences were searched. From among the papers found, 106 were related to the subject. All of the examined cancers in relation to AQP1 included adenoid cystic carcinoma, bladder, breast, cervical, colon, colorectal, hepatocellular, lung, ovarian, plural mesothelioma, prostate, renal cell carcinoma and squamous cell carcinoma. All of the studied cancers in relation with AQP3 included gastric, breast, prostate, lung, pancreas, skin, bladder, squamous cell carcinoma, cervical, adenoid cystic carcinoma, colon, colorectal, ovarian, and hepatocellular cancers and with regard to AQP5 were lung, squamous cell carcinoma, ovarian, adenoid cystic carcinoma, breast, colon, colorectal, hepatic, pancreas, gallbladder, prostate, and gastric cancers. Over or under-expression of AQP1, 3 and is exist in the mentioned cancers across different studies. Over-expression of AQP1, AQP3 and AQP5 is clearly associated with carcinogenesis, metastasis, reduced survival rate, lymph node metastasis, poorer prognosis, and cellular migration. Also, cancer treatments in relation to these markers suggest AQP reduction during the treatment.

MicroRNA-325-3p inhibits cell proliferation and induces apoptosis in hepatitis B virus-related hepatocellular carcinoma by down-regulation of aquaporin 5

BACKGROUND

Hepatitis B virus (HBV) infection is acknowledged as the main cause of hepatocellular carcinoma (HCC). Moreover, previous studies have revealed that microRNAs (miRNAs) widely participate in regulation of various cellular processes, such as viral replication. Hence, the purpose of this study was to investigate the roles of aquaporin 5 (AQP5) and miR-325-3p in the proliferation and apoptosis of HBV-related HCC cells.

METHODS

AQP5 and miR-325-3p expression in both normal and HBV-HCC tissues or cells (both Huh7-1.3 and HepG2.2.15) was detected using qRT-PCR. AQP5 expression was knocked down in HBV-related Huh7-1.3 and HepG2.2.15 cells using small interfering RNA (siRNA) technology. Down-regulation was confirmed using real-time PCR and Western blot analysis. Effects of AQP5 down-regulation on the proliferation and apoptosis were assessed. Dual luciferase reporter gene assay, Western blot and qRT-PCR were employed to evaluate the effect of miR-325-3p on the luciferase activity and expression of AQP5. Moreover, miR-325-3p mimic-induced changes in cellular proliferation and apoptosis were detected through CCK-8 assay, BrdU assay, flow cytometry analysis and ELISA.

RESULTS

In this study, the expression of AQP5 was up-regulated in human HBV-HCC tissue, Huh7-1.3 and HepG2.2.15 cells. Knockdown of AQP5 significantly inhibited the proliferation and promoted apoptosis of HBV-HCC cells. Next, miR-325-3p was obviously down-regulated in HBV-HCC. In concordance with this, MiR-325-3p directly targeted AQP5, and reduced both mRNA and protein levels of AQP5, which promoted cell proliferation and suppressed cell apoptosis in HCC cells. Overexpression of miR-325-3p dramatically inhibited cell proliferation and induced cell apoptosis.

CONCLUSIONS

Our findings clearly demonstrated that introduction of miR-325-3p inhibited proliferation and induced apoptosis of Huh7-1.3 and HepG2.2.15 cells by directly decreasing AQP5 expression, and that silencing AQP5 expression was essential for the pro-apoptotic effect of miR-325-3p overexpression on Huh7-1.3 and HepG2.2.15 cells. It is beneficial to gain insight into the mechanism of HBV infection and pathophysiology of HBV-related HCC.

Aquaporin 5 expression correlates with tumor multiplicity and vascular invasion in hepatocellular carcinoma

Aquaporins (AQPs) are a family of water channel transmembrane proteins that play a key role in transcellular water movement and transport. Recent studies have reported that AQPs are involved in cancer biology and can be a novel biomarker for predicting prognosis. The aim of this study was to identify clinical significance and prognostic impact of AQP5 in surgically resected hepatocellular carcinomas (HCCs). We analyzed the association between the expression of AQP5, Ki-67, and E-cadherin. Immunohistochemical stains for AQP5, KI-67, and E-cadherin were performed on 72 surgically resected HCCs. As a result, 46 patients (63.9%) showed AQP5 expression, 46 patients (63.9%) revealed high expression of Ki-67, and E-cadherin loss was identified in 8 patients (11.1%). No significant relationship among the three markers was found (all P > 0.05). AQP5 expression was associated with tumor multiplicity (P = 0.039), microvascular invasion (P = 0.040), and major vessel invasion (P = 0.044). High expression of Ki-67 was related to high serum AFP level (P = 0.006), tumor grade (P = 0.002), and microvascular invasion (P = 0.040). AQP5 expression tended to be associated with worse overall survival (OS) (P = 0.093) in the univariate analysis, but no significance was found in the multivariate survival analysis. High expression of Ki-67 was associated with shorter recurrence-free survival (RFS) in both univariate (P = 0.012) and multivariate analysis (P = 0.020). In conclusion, AQP5 might be a prognostic marker in HCC based on its association with tumor multiplicity, microvascular invasion, and major vessel invasion; and Ki-67 is an independent prognostic factor in HCC.

MicroRNA-488 inhibits proliferation, invasion and EMT in osteosarcoma cell lines by targeting aquaporin 3

It has been reported that aquaporin 3 (AQP3) expression is associated with the progression of numerous types of cancer and microRNA (miRNA/miR) processing. However, the effects and precise mechanisms of AQP3 in osteosarcoma (OS) have not been fully elucidated. The present study aimed to investigate the interaction between AQP3 and miR-488 in OS. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay was performed to detect the levels of AQP3 and miR-488 in OS tissues and cell lines, respectively. Cell proliferation, invasion and epithelial-mesenchymal transition (EMT) were detected to analyze the biological functions of miR-488 and AQP3 in OS cells. Furthermore, mRNA and protein levels of AQP3 was measured by RT-qPCR and western blot analysis. Furthermore, AQP3 was validated as an miR-488 target using luciferase assays in OS cells. The present study revealed that the miR-488 level was significantly downregulated in OS tissues and cell lines, and that the expression of AQP3 was markedly increased. Notable, the low miR-488 expression level was associated with upregulated AQP3 expression in OS tissues. Furthermore, introduction of miR-488 markedly suppressed the proliferation, invasion and EMT of OS cells. However, miR-488-knockdown increased the proliferation, invasion and EMT of OS cells. The present study demonstrated that miR-488 could directly target AQP3 using bioinformatics analysis and luciferase reporter assays. In addition, AQP3-silencing had similar effects to miR-488 overexpression on OS cells. Overexpression of AQP3 in OS cells partially reversed the inhibitory effects of miR-488 mimic. miR-488 inhibited the proliferation, invasion and EMT of OS cells by directly downregulating AQP3 expression, and miR-488 targeting AQP3 was responsible for inhibition of the proliferation, invasion and EMT of OS cells.

Ectopic expression of aquaporin-5 in noncancerous epithelial MDCK cells changes cellular morphology and actin fiber formation without inducing epithelial-to-mesenchymal transition

Aquaporin-5 (AQP5) is a plasma membrane water channel mainly expressed in secretory glands. Increased expression of AQP5 is observed in multiple cancers, including breast cancer, where high expression correlates with the degree of metastasis and poor prognosis. Moreover, studies in cancer cells have suggested that AQP5 activates Ras signaling, drives morphological changes, and in particular increased invasiveness. To design intervention strategies, it is of utmost importance to characterize and dissect the cell biological changes induced by altered AQP5 expression. To isolate the effect of AQP5 overexpression from the cancer background, AQP5 was overexpressed in normal epithelial MDCK cells which have no endogenous AQP5 expression. AQP5 overexpression promoted actin stress fiber formation and lamellipodia dynamics. Moreover, AQP5 decreased cell circularity. Phosphorylation of AQP5 on serine 156 in the second intracellular loop has been shown to activate the Ras pathway. When serine 156 was mutated to alanine to mimic the nonphosphorylated state, the decrease in cell circularity was reversed, indicating that the AQP5-Ras axis is involved in the effect on cell shape. Interestingly, the cellular changes mediated by AQP5 were not associated with induction of epithelial-to-mesenchymal transition. Thus, AQP5 may contribute to cancer by altering cellular morphology and actin organization, which increase the metastatic potential.

Differential Expression of Aquaporins in Experimental Models of Acute Lung Injury

AIM

The mammalian lung expresses at least three aquaporin (AQP) water channels whose precise role in lung injury or inflammation is still controversial.

MATERIALS AND METHODS

Three murine models of lung inflammation and corresponding controls were used to evaluate the expression of Aqp1, Aqp4, Aqp5 and Aqp9: lipopolysaccharide (LPS)-induced lung injury; HCl-induced lung injury; and ventilation-induced lung injury (VILI).

RESULTS

All models yielded increased lung vascular permeability, and inflammatory cell infiltration in the broncho-alveolar lavage fluid; VILI additionally produced altered lung mechanics. Lung expression of Aqp4 decreased in the models that targeted primarily the alveolar epithelium, i.e. acid aspiration and mechanical ventilation, while Aqp5 expression decreased in the model that appeared to target both the capillary endothelium and alveolar epithelium, i.e. LPS.

CONCLUSION

Participation of aquaporins in the acute inflammatory process depends on localization and the type of lung injury.

Mechanisms of Aquaporin-Facilitated Cancer Invasion and Metastasis

Cancer is a leading cause of death worldwide, and its incidence is rising with numbers expected to increase 70% in the next two decades. The fact that current mainline treatments for cancer patients are accompanied by debilitating side effects prompts a growing demand for new therapies that not only inhibit growth and proliferation of cancer cells, but also control invasion and metastasis. One class of targets gaining international attention is the aquaporins, a family of membrane-spanning water channels with diverse physiological functions and extensive tissue-specific distributions in humans. Aquaporins−1,−2,−3,−4,−5,−8, and−9 have been linked to roles in cancer invasion, and metastasis, but their mechanisms of action remain to be fully defined. Aquaporins are implicated in the metastatic cascade in processes of angiogenesis, cellular dissociation, migration, and invasion. Cancer invasion and metastasis are proposed to be potentiated by aquaporins in boosting tumor angiogenesis, enhancing cell volume regulation, regulating cell-cell and cell-matrix adhesions, interacting with actin cytoskeleton, regulating proteases and extracellular-matrix degrading molecules, contributing to the regulation of epithelial-mesenchymal transitions, and interacting with signaling pathways enabling motility and invasion. Pharmacological modulators of aquaporin channels are being identified and tested for therapeutic potential, including compounds derived from loop diuretics, metal-containing organic compounds, plant natural products, and other small molecules. Further studies on aquaporin-dependent functions in cancer metastasis are needed to define the differential contributions of different classes of aquaporin channels to regulation of fluid balance, cell volume, small solute transport, signal transduction, their possible relevance as rate limiting steps, and potential values as therapeutic targets for invasion and metastasis.

Aquaporin 5 promotes corneal wound healing

Aquaporins (AQPs), ordinarily regarded as water channels, have recently been shown to participate in other cellular functions such as cell-to-cell adhesion, cell migration, cell proliferation etc. The current investigation was undertaken to find out whether AQP5 water channel plays a role in corneal epithelial wound healing. Expression of AQP5 in mouse cornea and transfected Madin-Darby canine kidney (MDCK) cells was detected using immunofluorescence or EGFP tag. Cell migration and proliferation, the two major events in wound healing, were studied in vitro using cell culture scratch-wound healing model and cell proliferation assay, in vivo by conducting wound healing experiments on corneas of wild-type and AQP5 knockout mouse model and ex vivo on corneal epithelial cells isolated from wild type and AQP5 knockout mice. MDCK cells stably expressing AQP5 showed significantly higher levels of cell migration and proliferation compared to control cells. Likewise, corneal epithelial cells of wild type mouse with innate AQP5 exhibited faster wound healing than those of AQP5 knockout in vivo and under ex vivo culture conditions. In vitro, in vivo and ex vivo studies showed that presence of AQP5 improved cell migration, proliferation and wound healing. The data collected suggest that AQP5 plays a significant role in corneal epithelial wound healing.

Anti-cancer effect of Aquaporin 5 silencing in colorectal cancer cells in association with inhibition of Wnt/β-catenin pathway

Aquaporin 5 (AQP5) is a water channel protein that is over-expressed in many tumors. Elevated expression of AQP5 is associated with poor prognosis of colorectal cancer. Yet, whether AQP5 plays a role in epithelial-mesenchymal transition (EMT) of colorectal cancer has not been reported until now. Here we aim to investigate the function of AQP5 in the EMT process of colorectal cancer. We transfected HCT116 and SW480 cells with AQP5-specific shRNA and verified the knockdown efficiency through western blotting and real-time PCR. Afterwards, scratch wound healing assay, invasion assay, gelatin zymography, immunofluorescence staining and immunoblotting were performed to assess the effect of AQP5 silencing in these two cells. The ability of migration and invasion of colorectal cancer cells was significantly impaired after AQP5 silencing. Correspondingly, the activity and expression of Matrix Metallopeptidase (MMP)-2 and MMP-9 were reduced. Moreover, the expression levels of EMT-related factors were altered: E-cadherin, Tissue Inhibitor Of Metalloproteinases (TIMP)-1 and TIMP-2 were upregulated, whereas Vimentin, N-cadherin, Plasminogen Activator, Urokinase (uPA) and Snail were downregulated following knockdown of AQP5 in colorectal cancer cells. Furthermore, the expression of Wnt1 and β-catenin was markedly decreased after AQP5 knockdown. Interestingly, the alteration of EMT-related factors mediated by AQP5 knockdown could be reversed by upregulation of β-catenin. Taken together, silencing of AQP5 restrained the migration and invasion of colorectal cancer cells, and regulated the expression of EMT-related molecules in them by inhibiting Wnt/β-catenin pathway.

Silencing of aquaporin 5 inhibits the growth of A549 lung cancer cells in vitro and in vivo

The water channel protein aquaporin 5 (AQP5) is highly expressed in numerous tumors. However, its expression pattern and functions in lung cancer in humans remain unknown. In the present study, the role of AQP5 in the development of lung malignancies was examined. A short hairpin RNA construct targeting AQP5 mRNA was transfected into A549 cells to generate a lung cancer cell line in which AQP5 expression was stably silenced. In vitro and in vivo experiments were then performed to establish the effects of AQP5 on A549 cell apoptosis, proliferation and cell cycle progression. The results demonstrated that AQP5 silencing significantly inhibited the proliferation and promoted the apoptosis of A549 lung cancer cells in vitro and in vivo. In addition, it resulted in decreased activation of the extracellular signal-regulated kinase 1/2 signaling pathway in A549 cells, and reduced levels of the downstream proteins c‑Fos and phosphorylated cAMP response element-binding protein. Furthermore, inhibition of AQP5 expression effectively reduced the tumorigenicity of A549 cells in vivo. In conclusion, silencing of AQP5 suppressed the growth of A549 cells in vitro and in vivo, suggesting that it may serve as a therapeutic target in lung cancer.

Impact of AQP-5 on the growth of colorectal cancer cells and the underlying mechanism

Aquaporin 5 (AQP-5) is highly expressed in colorectal cancer tissue and associated with colorectal cancer development and prognosis. Here, we explored the effects of AQP-5 on colorectal cancer cell proliferation and apoptosis and the underlying mechanism by inhibiting endogenous AQP-5 expression in the human colorectal cancer cell lines COLO 205 and SW480. These cells were transfected with an AQP-5-siRNA, and transfection efficiency and its effects on AQP-5 expression were assessed by immunofluorescence and PCR, respectively. Then, cell proliferation was assessed via the MTT assay, apoptosis was assessed by Annexin V-FITC/PI and TUNEL assays, and expression changes in Bax and Bcl-2 were assessed by RT-PCR and western blotting. Transfection with AQP-5-siRNA reduced AQP-5 expression by up to 62%. The MTT assay showed that cell proliferation was significantly inhibited by AQP-5-siRNA transfection compared to that in NS-siRNA-transfected cells (P < 0.05). Flow cytometry analysis revealed that the percentage of apoptotic AQP-5-siRNA-transfected cells was significantly higher than that of NS-siRNA-transfected cells (P < 0.05). Real-time quantitative RT-PCR and western blotting showed that AQP-5-siRNA significantly increased the Bax/Bcl-2 mRNA and protein ratios compared with those following NS-siRNA transfection. Thus, AQP5-siRNA promotes apoptosis of colorectal cancer cells, which may be associated with Bax/Bcl expression.

[Role of aquaporin-5 in regulating colorectal cancer cell growth in vitro]

OBJECTIVE

To study the role of aquaporin 5(AQP5) in regulating the cell proliferation and apoptosis of human colorectal cancer cells and explore the possible mechanism.

METHODS

A small interfering RNA (siRNA) targeting AQP5 was used to suppress endogenous AQP5 expression in the human colorectal cancer cell lines COLO 205 and SW480, and the transfection efficiency of AQP5 siRNA was determined using immunofluorescence assay and PCR. The changes in the proliferation of the transfected cells was evaluated with MTT assay, and the cell apoptosis was analyzed using Annexin V-FITC/PI and TUNEL assays; the changes of Bax and Bcl2 expressions in the cells were determined using RTPCR and Western blotting.

RESULTS

Transfection with AQP-5-siRNA resulted in a significant reduction (up to 90%) of AQP-5 expression in COLO 205 and SW480 cells. MTT assay showed that AQP-5-siRNA transfection significantly inhibited the cell proliferation compared NS siRNA transfection (P<0.05). Flow cytometric analysis revealed significantly increased apoptotic rate of cells following AQP-5-siRNA transfection compared with NS?siRNA transfection(P<0.05). Real-time quantitative RT-PCR and Western blotting demonstrated that AQP-5-siRNA transfection significantly increased Bax and Bcl-2 expressions at both mRNA and protein levels in the cells.

CONCLUSION

AQP5-siRNA can promote apoptosis of colorectal cancer cells in vitro possibly in relation to its effects on Bax and Bcl expressions.

Immunohistochemical evalulation of activated Ras and Rac1 as potential downstream effectors of aquaporin-5 in breast cancer in vivo

Aberrant levels of aquaporin-5 (AQP5) expression have been observed in several types of cancer, including breast cancer, where AQP5 overexpression is associated with metastasis and poor prognosis. In cultured cancer cells, AQP5 facilitates cell migration and activates Ras signaling. Both increased cell migration and Ras activation are associated with cancer metastasis, but so far it is unknown if AQP5 also affects these processes in vivo. Therefore, we investigated if high AQP5 expression in breast cancer tissue correlated with increased activation of Ras and of Rac1, which is a GTPase also involved in cell migration. This was accomplished by immunohistochemical analysis of invasive ductal carcinoma of breast tissue sections from human patients, followed by qualitative and quantitative correlation analysis between AQP5 and activated Ras and Rac1. Immunohistochemistry revealed that activation of Ras and Rac1 was positively correlated. There was, however, no correlation between high AQP5 expression and activation of Ras, whereas a nonsignificant, but positive, tendency between the levels of AQP5 and activated Rac1 levels was observed. In summary, this is the first report that correlates AQP5 expression levels to downstream signaling partners in breast cancer tissue sections. The results suggest Rac1 as a potential downstream signaling partner of AQP5 in vivo.

Identification of novel gene expression signature in lung adenocarcinoma by using next-generation sequencing data and bioinformatics analysis

Lung adenocarcinoma is one of the leading causes of cancer-related death worldwide. We showed transcriptomic profiles in three pairs of tumors and adjacent non-tumor lung tissues using next-generation sequencing (NGS) to screen protein-coding RNAs and microRNAs. Combined with meta-analysis from the Oncomine and Gene Expression Omnibus (GEO) databases, we identified a representative genetic expression signature in lung adenocarcinoma. There were 9 upregulated genes, and 8 downregulated genes in lung adenocarcinoma. The analysis of the effects from each gene expression on survival outcome indicated that 6 genes (AGR2, SPDEF, CDKN2A, CLDN3, SFN, and PHLDA2) play oncogenic roles, and 7 genes (PDK4, FMO2, CPED1, GNG11, IL33, BTNL9, and FABP4) act as tumor suppressors in lung adenocarcinoma. In addition, we also identified putative genetic interactions, in which there were 5 upregulated microRNAs with specific targets - hsa-miR-183-5p-BTNL9, hsa-miR-33b-5p-CPED1, hsa-miR-429-CPED1, hsa-miR-182-5p-FMO2, and hsa-miR-130b-5p-IL33. These 5 microRNAs have been shown to be associated with tumorigenesis in lung cancer. Our findings suggest that these genetic interactions play important roles in the progression of lung adenocarcinoma. We propose that this molecular change of genetic expression may represent a novel signature in lung adenocarcinoma, which may be developed for diagnostic and therapeutic strategies in the future.

Aquaporins in Respiratory System

Aquaporins (AQPs ) are water channel proteins supposed to facilitating fluid transport in alveolar space, airway humidification, pleural fluid absorption, and submucosal gland secretion . In this chapter, we mainly focus on the expression of 4 AQPs in the lungs which include AQP1, AQP2 , AQP4 and AQP5 in normal and disease status, and the experience of AQPs function from various model and transgenic mice were summarized in detail to improve our understanding of the role of AQPs in fluid balance of respiratory system. It has been suggested that AQPs play important roles in various physiology and pathophysiology conditions of different lung diseases. There still remains unclear the exact role of AQPs in lung diseases, and thus continuous efforts on elucidating the roles of AQPs in lung physiological and pathophysilogical processes are warranted.

AQP5 promotes hepatocellular carcinoma metastasis via NF-κB-regulated epithelial-mesenchymal transition

Aquaporin 5 (AQP5), a transmembrane protein, is known for its involvement in the progress of many diseases such as chronic kidney disease and systemic disease. Recently, AQP5 has been reported to play an important role in cancer progression. However, little is known about its precise functions in hepatocellular carcinoma (HCC). This study aimed to investigate the specific role of AQP5 in HCC. The results showed that AQP5 was highly expressed in HCC cell lines and its down-regulation inhibited HCC cell invasion and tumor metastasis in vitro and in vivo. In addition, down-regulation of AQP5 suppressed the epithelial-mesenchymal transition (EMT) process in HCC cells by modulating EMT-related molecules such as E-cadherin, α-catenin, N-cadherin and Vimentin. Further studies on corresponding mechanisms indicated that AQP5 down-regulation inhibited HCC metastasis and EMT partly via inactivation of the NF-κB signaling pathway. Taken together, these findings suggest that AQP5 may be a potential therapeutic target for HCC.

Differential expression of aquaporin-3 and aquaporin-5 in pancreatic ductal adenocarcinoma

BACKGROUND AND OBJECTIVES

Aquaporin-5 (AQP5) and -3 (AQP3) are protein channels that showed to be up-regulated in a variety of tumors. Our goal was to investigate the expression pattern of AQP5 and AQP3 in pancreatic ductal adenocarcinomas (PDA) and correlate with cell proliferation, tumor stage and progression, and clinical significance.

METHODS

35 PDA samples in different stages of differentiation and locations were analyzed by immunohistochemistry for expression of AQP5, AQP3 and several markers of cell proliferation and tumorigenesis.

RESULTS

In PDA samples AQP5 was overexpressed in the apical membrane of intercalated and intralobular ductal cells while AQP3 was expressed at the plasma membrane of ductal cells. AQP5 was also found in infiltrative cancer cells in duodenum. Simultaneous overexpression of EGFR, Ki-67, and CK7, with decreased E-cad and increased Vim that characterize epithelial mesenchymal transition, tumor formation and invasion, strongly suggest AQP3 and AQP5 involvement in cell proliferation and transformation. AQP3 overexpression is reinforced in late and more aggressive PDA stages whereas AQP5 is related with tumor differentiation, suggesting it may represent a novel marker for PDA aggressiveness and intestinal infiltration.

CONCLUSIONS

These findings suggest AQP3 and AQP5 involvement in PDA development and the usefulness of AQP5 in early PDA diagnosis.

Cancer cell motility: lessons from migration in confined spaces

Time-lapse, deep-tissue imaging made possible by advances in intravital microscopy has demonstrated the importance of tumour cell migration through confining tracks in vivo. These tracks may either be endogenous features of tissues or be created by tumour or tumour-associated cells. Importantly, migration mechanisms through confining microenvironments are not predicted by 2D migration assays. Engineered in vitro models have been used to delineate the mechanisms of cell motility through confining spaces encountered in vivo. Understanding cancer cell locomotion through physiologically relevant confining tracks could be useful in developing therapeutic strategies to combat metastasis.

Rat Aquaporin-5 Is pH-Gated Induced by Phosphorylation and Is Implicated in Oxidative Stress

Aquaporin-5 (AQP5) is a membrane water channel widely distributed in human tissues that was found up-regulated in different tumors and considered implicated in carcinogenesis in different organs and systems. Despite its wide distribution pattern and physiological importance, AQP5 short-term regulation was not reported and mechanisms underlying its involvement in cancer are not well defined. In this work, we expressed rat AQP5 in yeast and investigated mechanisms of gating, as well as AQP5’s ability to facilitate H₂O₂ plasma membrane diffusion. We found that AQP5 can be gated by extracellular pH in a phosphorylation-dependent manner, with higher activity at physiological pH 7.4. Moreover, similar to other mammalian AQPs, AQP5 is able to increase extracellular H₂O₂ influx and to affect oxidative cell response with dual effects: whereas in acute oxidative stress conditions AQP5 induces an initial higher sensitivity, in chronic stress AQP5 expressing cells show improved cell survival and resistance. Our findings support the involvement of AQP5 in oxidative stress and suggest AQP5 modulation by phosphorylation as a novel tool for therapeutics.

The role of aquaporin-5 in cancer cell migration: A potential active participant

Emerging data identifies the water channel aquaporin-5 as a major player in multiple cancers. Over-expression of aquaporin-5 has been associated with increased metastasis and poor prognosis, suggesting that aquaporin-5 may enhance cancer cell migration. This review aims to highlight the current knowledge and hypothesis regarding downstream signaling partners of aquaporin-5 in relation to cancer cell migration. The molecular mechanisms that link aquaporin-5 to cell migration are not completely understood. Aquaporin-5 may promote cell movement by increasing water uptake into the front of the cell allowing local swelling. Aquaporin-5 may also activate extracellular-regulated kinases, increasing proliferation and potentially stimulating the migration machinery. Thus, further studies are warranted to identify the underlying mechanisms and signaling pathways. This will reveal whether aquaporin-5 and downstream effectors could be targets for developing new cancer therapeutics.