Prognostic value of combined aquaporin 3 and aquaporin 5 overexpression in hepatocellular carcinoma. Biomed Res Int. 2013;2013:206525. [PMID: 24224160 PMCID: PMC3810059 DOI: 10.1155/2013/206525]

Uncovering the role of aquaporin and chromobox family members as potential biomarkers in head and neck squamous cell carcinoma via integrative multiomics and in silico approach

Head and neck squamous cell carcinoma (HNSC) is a diverse group of tumors arising from oral cavity, oropharynx, larynx, and hypopharynx squamous epithelium, posing significant morbidity. Aquaporins (AQPs) are membrane proteins forming water channels, some associated with carcinomas. Chromobox (CBX) family is known to modulate physiological and oncological processes. In our study, we analyzed AQPs and CBXs having significant expression followed by their prognostic and mutational assessment. Next, we performed enrichment and tumor infiltration analysis followed by HPA validation. Lastly, we established a 3-node miRNA-TF-mRNA regulatory network and performed protein-protein docking of the highest-degree subnetwork motif between TF and mRNA. Significant upregulation of CBX3/2 and downregulation of AQP3/5/7 correlated with poor overall survival (OS) in HNSC patients. The most significant pathway, GO-BP, GO-MF, and GO-CC terms associated with AQP3 and CBX3 were passive transport by aquaporins, response to vitamin, glycerol channel activity, and condensed chromosome, centromeric region. AQP3 negatively correlated withCD 4 + T cells, positively withCD 8 + T cells and B cells, and negatively with tumor purity, whereas CBX3 positively correlated withCD 4 + T cells, negatively withCD 8 + T cells and B cells, and positively with tumor purity. Three-node miRNA-TF-mRNA regulatory network revealed a highest-degree subnetwork motif comprising one TF (SMAD3), one miRNA (miR-423-5p), and one mRNA (AQP3). Protein-protein interaction studies suggested a direct interaction between AQP3 and Smad3 proteins. We concluded that AQP3 and CBX3 hold potential as treatment strategies and individual prognostic biomarkers, while further protein-protein interaction studies of AQP3 could offer insights into its interactions with Smad3 proteins.

Pathophysiological role of ion channels and transporters in hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) has continued to increase annually worldwide, and HCC has become a common cause of cancer-related death. Despite great progress in understanding the molecular mechanisms underlying HCC development, the treatment of HCC remains a considerable challenge. Thus, the survival and prognosis of HCC patients remain extremely poor. In recent years, the role of ion channels in the pathogenesis of diseases has become a hot topic. In normal liver tissue, ion channels and transporters maintain water and electrolyte balance and acid‒base homeostasis. However, dysfunction of these ion channels and transporters can lead to the development and progression of HCC, and thus these ion channels and transporters are expected to become new therapeutic targets. In this review, ion channels and transporters associated with HCC are reviewed, and potential targets for new and effective therapies are proposed.

Exploring non-coding RNA mechanisms in hepatocellular carcinoma: implications for therapy and prognosis

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths in the world. The development and progression of HCC are closely correlated with the abnormal regulation of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Important biological pathways in cancer biology, such as cell proliferation, death, and metastasis, are impacted by these ncRNAs, which modulate gene expression. The abnormal expression of non-coding RNAs in HCC raises the possibility that they could be applied as new biomarkers for diagnosis, prognosis, and treatment targets. Furthermore, by controlling the expression of cancer-related genes, miRNAs can function as either tumor suppressors or oncogenes. On the other hand, lncRNAs play a role in the advancement of cancer by interacting with other molecules within the cell, which, in turn, affects processes such as chromatin remodeling, transcription, and post-transcriptional processes. The importance of ncRNA-driven regulatory systems in HCC is being highlighted by current research, which sheds light on tumor behavior and therapy response. This research highlights the great potential of ncRNAs to improve patient outcomes in this difficult disease landscape by augmenting the present methods of HCC care through the use of precision medicine approaches.

Identification of ferroptosis-related molecular subtypes and a methylation-related ferroptosis gene prognostic signature in cervical squamous cell carcinoma

PURPOSE

We aimed to investigate the molecular characteristics of cervical squamous cell carcinoma (CESC) by analyzing ferroptosis-related gene (FRG) expression data to predict prognosis.

METHODS

Gene expression and clinicopathological data of patients with CESC were collected from the Cancer Genome Atlas and the Genotype-Tissue Expression databases. Using Cox regression analysis, we identified 21 FRGs associated with prognosis. Cluster analysis categorized patients into subgroups based on these genes and compared their clinicopathological, biological, and immune infiltration features. FRG methylation levels were examined, and a risk model based on such FRG methylation levels was constructed using LASSO and Cox regression analyses. The model's predictive capacity was validated, and the relationships between the risk score and immune infiltration, tumor microenvironment, and drug sensitivity were explored. FRG methylation in CESC tissues was validated by immunohistochemistry.

RESULTS

We identified 21 FRGs associated with CESC prognosis. Patients were stratified into two subtypes based on these genes, they showed differences in prognosis, immune cell types, and immune checkpoint expression. A three-gene risk score (including AQP3, MGST1, and TFRC) was generated, and the low-risk group showed better overall survival. The high-risk and low-risk groups differed in terms of immune infiltration, gene mutations, and drug sensitivity. Experimental validation confirmed the upregulation of AQP3 and TFRC, whereas MGST1 expression was not significantly altered in CESC tissues compared with that in normal cervical tissues.

CONCLUSION

This study highlights the potential role of FRG methylation in predicting CESC prognosis and provides a personalized assessment of immune responses in patients with CESC.

Relevant Membrane Transport Proteins as Possible Gatekeepers for Effective Pharmacological Ascorbate Treatment in Cancer

Despite the increasing number of newly diagnosed malignancies worldwide, therapeutic options for some tumor diseases are unfortunately still limited. Interestingly, preclinical but also some clinical data suggest that the administration of pharmacological ascorbate seems to respond well, especially in some aggressively growing tumor entities. The membrane transport and channel proteins are highly relevant for the use of pharmacological ascorbate in cancer therapy and are involved in the transfer of active substances such as ascorbate, hydrogen peroxide, and iron that predominantly must enter malignant cells to induce antiproliferative effects and especially ferroptosis. In this review, the relevant conveying proteins from cellular surfaces are presented as an integral part of the efficacy of pharmacological ascorbate, considering the already known genetic and functional features in tumor tissues. Accordingly, candidates for diagnostic markers and therapeutic targets are mentioned.

Aquaporins and Ion Channels as Dual Targets in the Design of Novel Glioblastoma Therapeutics to Limit Invasiveness

Current therapies for Glioblastoma multiforme (GBM) focus on eradicating primary tumors using radiotherapy, chemotherapy and surgical resection, but have limited success in controlling the invasive spread of glioma cells into a healthy brain, the major factor driving short survival times for patients post-diagnosis. Transcriptomic analyses of GBM biopsies reveal clusters of membrane signaling proteins that in combination serve as robust prognostic indicators, including aquaporins and ion channels, which are upregulated in GBM and implicated in enhanced glioblastoma motility. Accumulating evidence supports our proposal that the concurrent pharmacological targeting of selected subclasses of aquaporins and ion channels could impede glioblastoma invasiveness by impairing key cellular motility pathways. Optimal sets of channels to be selected as targets for combined therapies could be tailored to the GBM cancer subtype, taking advantage of differences in patterns of expression between channels that are characteristic of GBM subtypes, as well as distinguishing them from non-cancerous brain cells such as neurons and glia. Focusing agents on a unique channel fingerprint in GBM would further allow combined agents to be administered at near threshold doses, potentially reducing off-target toxicity. Adjunct therapies which confine GBM tumors to their primary sites during clinical treatments would offer profound advantages for treatment efficacy.

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.

Aquaporins as Prognostic Biomarker in Prostate Cancer

Prostate cancer is a complex heterogeneous disease that affects millions of males worldwide. Despite rapid advances in molecular biology and innovation in technology, few biomarkers have been forthcoming in prostate cancer. The currently available biomarkers for the prognosis of prostate cancer are inadequate and face challenges, thus having limited clinical utility. To date, there are a number of prognostic and predictive biomarkers identified for prostate cancer but lack specificity and sensitivity to guide clinical decision making. There is still tremendous scope for specific biomarkers to understand the natural history and complex biology of this heterogeneous disease, and to identify early treatment responses. Accumulative studies indicate that aquaporins (AQPs) a family of membrane water channels may serve as a prognostic biomarker for prostate cancer in monitoring disease advancement. In the present review, we discuss the existing prostate cancer biomarkers, their limitations, and aquaporins as a prospective biomarker of prognostic significance in prostate cancer.

Molecular mechanism of aquaporin 3 (AQP3) regulating by LMP2A and its crosstalk with 4E-BP1 via ERK signaling pathway in EBV-associated gastric cancer

Aquaporin 3(AQP3) is involved in epithelial-mesenchymal transformation of tumor cells and is closely related to the occurrence and development of tumors. However, the regulatory mechanism and function of AQP3 in EBV-associated gastric cancer (EBVaGC) are still poorly understood. This study aims to explore the regulatory effect of EBV on AQP3 and the cross talk of AQP3 with EIF4E-binding proteins 1(4E-BP1) in EBVaGC. The effect of LMP2A on the expression of AQP3 and 4E-BP1 was analyzed using real-time PCR and western blotting. The biological functions of AQP3 and 4E-BP1 in gastric cancer cells were detected by cell biological experiments. In addition, we examined the role of mTOR and ERK signaling pathways in the LMP2A/AQP3/4E-BP1 regulatory axis. We found that LMP2A could down-regulate AQP3 expression by inhibiting the activation of mTOR signaling pathway, and further promote autophagy and migration of gastric cancer cells. AQP3 up-regulated the expression of 4E-BP1 and its phosphorylated protein by activating ERK signaling pathway, thus promoting the autophagy and proliferation of gastric cancer cells. In conclusion, EBV-encoded LMP2A inhibits AQP3 expression, and further participates in cell proliferation, migration and autophagy through the mTOR/AQP3/ERK/4E-BP1 axis.

Critical Role of Aquaporins in Cancer: Focus on Hematological Malignancies

Simple Summary

Aquaporins are proteins able to regulate the transfer of water and other small substances such as ions, glycerol, urea, and hydrogen peroxide across cellular membranes. AQPs provide for a huge variety of physiological phenomena; their alteration provokes several types of pathologies including cancer and hematological malignancies. Our review presents data revealing the possibility of employing aquaporins as biomarkers in patients with hematological malignancies and evaluates the possibility that interfering with the expression of aquaporins could represent an effective treatment for hematological malignancies.

Abstract

Aquaporins are transmembrane molecules regulating the transfer of water and other compounds such as ions, glycerol, urea, and hydrogen peroxide. Their alteration has been reported in several conditions such as cancer. Tumor progression might be enhanced by aquaporins in modifying tumor angiogenesis, cell volume adaptation, proteases activity, cell–matrix adhesions, actin cytoskeleton, epithelial–mesenchymal transitions, and acting on several signaling pathways facilitating cancer progression. Close connections have also been identified between the aquaporins and hematological malignancies. However, it is difficult to identify a unique action exerted by aquaporins in different hemopathies, and each aquaporin has specific effects that vary according to the class of aquaporin examined and to the different neoplastic cells. However, the expression of aquaporins is altered in cell cultures and in patients with acute and chronic myeloid leukemia, in lymphoproliferative diseases and in multiple myeloma, and the different expression of aquaporins seems to be able to influence the efficacy of treatment and could have a prognostic significance, as greater expression of aquaporins is correlated to improved overall survival in leukemia patients. Finally, we assessed the possibility that modifying the aquaporin expression using aquaporin-targeting regulators, specific monoclonal antibodies, and even aquaporin gene transfer could represent an effective therapy of hematological malignancies.

Clinical value and molecular mechanism of AQGPs in different tumors

Aquaglyceroporins (AQGPs), including AQP3, AQP7, AQP9, and AQP10, are transmembrane channels that allow small solutes across biological membranes, such as water, glycerol, H₂O₂, and so on. Increasing evidence suggests that they play critical roles in cancer. Overexpression or knockdown of AQGPs can promote or inhibit cancer cell proliferation, migration, invasion, apoptosis, epithelial-mesenchymal transition and metastasis, and the expression levels of AQGPs are closely linked to the prognosis of cancer patients. Here, we provide a comprehensive and detailed review to discuss the expression patterns of AQGPs in different cancers as well as the relationship between the expression patterns and prognosis. Then, we elaborate the relevance between AQGPs and malignant behaviors in cancer as well as the latent upstream regulators and downstream targets or signaling pathways of AQGPs. Finally, we summarize the potential clinical value in cancer treatment. This review will provide us with new ideas and thoughts for subsequent cancer therapy specifically targeting AQGPs.

Comprehensive Analysis of Aquaporin Superfamily in Lung Adenocarcinoma

Background: Lung adenocarcinoma (LUAD) is the most predomintnt lung cancer subtype with increasing morbidity and mortality. Previous studies have shown that aquaporin (AQP) family genes were correlated with tumor progression and metastasis in several kinds of malignancies. However, their biological behaviors and prognostic values in LUAD have not been comprehensively elucidated.

Methods: RNA sequencing and real-time reverse transcription PCR (RT-PCR) were used to assess AQP1/3/4/5 gene expressions in LUAD patients using GEPIA and UALCAN databases. And then Kaplan–Meier analysis, cBioPortal, Metascape, GeneMANIA, TISIDB, and TIMER were utilized to determine the prognostic value, mutation frequency, and immune cell infiltration of AQP family members in LUAD.

Results: We found that AQP3 expression was significantly elevated and AQP1 expression was markedly reduced in LUAD patients, whereas the expression levels of AQP4 and AQP5 exhibited no significant changes. The Kaplan–Meier survival analysis indicated that the higher expressions of AQP1/4/5 were related to longer overall survival (OS). Of interest, AQP3 was significantly correlated with the clinical tumor stage and lower AQP3 expression showed favorable prognosis in stage I LUAD patients, which indicated that AQP3 may be a potential prognostic biomarker for patients. Through functional enrichment analysis, the functions of these four AQPs genes were mainly involved in the passive transport by aquaporins, water homeostasis, and protein tetramerization. Moreover, AQP1/3/4/5 expression was strongly associated with tumor-infiltrating lymphocytes (TILs) in LUAD.

Conclusion: AQP3 can be used as a prognosis and survival biomarker for stage I LUAD. These findings may provide novel insights into developing molecular targeted therapies in LUAD.

Aquaporins in insulin resistance and diabetes: More than channels!

Aquaporins (AQPs) are part of the family of the integral membrane proteins. Their function is dedicated to the transport of water, glycerol, ammonia, urea, H2O2, and other small molecules across the biological membranes. Although for many years they were scarcely considered, AQPs have a relevant role in the development of many diseases. Recent discoveries suggest, that AQPs may play an important role in the process of fat accumulation and regulation of oxidative stress, two crucial aspects of insulin resistance and type-2 diabetes (T2D). Insulin resistance (IR) and T2D are multi-faceted systemic diseases with multiple connections to obesity and other comorbidities such as hypertension, dyslipidemia and metabolic syndrome. Both IR and T2D transcends different tissues and organs, creating the maze of mutual relationships between adipose fat depots, skeletal muscle, liver and other insulin-sensitive organs. AQPs with their heterogenous properties, distinctive tissue distribution and documented involvement in both the lipid metabolism and regulation of the oxidative stress appear to be feasible candidates in the search for the explanation to this third-millennium plague. A lot of research has been assigned to adipose tissue AQP7 and liver tissue AQP9, clarifying their relationship and coordinated work in the induction of hepatic insulin resistance. Novel research points also to other aquaporins, such as AQP11 which may be associated with the induction of insulin resistance and T2D through its involvement in hydrogen peroxide transport. In this review we collected recent discoveries in the field of AQP's involvement in the insulin resistance and T2D. Novel paths which connect AQPs with metabolic disorders can give new fuel to the research on obesity, insulin resistance and T2D - one of the most worrying problems of the modern society.

Initial assessment of suitability of MCF-7 and HepG2 cancer cell lines for AQP3 research in cancer biology

Cancer cell lines are widely used as in vitro models to elucidate biological processes in cancer, and as a tool to evaluate anticancer agents. In fact, the use of an appropriate cancer cell line in cancer research is crucial for investigating new, potential factors involved in carcinogenesis. One of them is aquaporin-3 (AQP3), which is a small, hydrophobic, integral membrane protein with a predominant role in water and glycerol transport. Recently, altered expression of AQP3 has been reported in many types of cancer. Increasing evidence strongly suggests that AQP3 plays a key role in cancer cell proliferation, migration and invasion. In this study, we performed an insightful characteristic of AQP3 location and its protein expression in MCF-7 human breast adenocarcinoma and HepG2 hepatocellular carcinoma cell lines in the context of cancer biology using immunocytochemistry, immunofluorescence and Western blot analyses. AQP3 was found to be located in the cell membrane and cytoplasm of MCF-7 cells, and in the cytoplasm and nuclear membrane of HepG2 cells. Immunoblotting of proteins derived from both cell lines revealed a clear band with a molecular weight of approx. 30 kDa representing an unglycosylated form of AQP3. However, the expression of this protein was higher in MCF-7 than in HepG2. Concluding, our results clearly indicated variability in both the expression levels and subcellular location of the AQP3 protein in MCF-7 and HepG2 cell lines. This leads to the possibility that the expression patterns and subcellular location of AQP3 in the tested cancer cell lines are tissue-of-origin specific, and may be related to the aggressiveness of cancer cells and their mobility.

Human Aquaporins: Functional Diversity and Potential Roles in Infectious and Non-infectious Diseases

Aquaporins (AQPs) are integral membrane proteins and found in all living organisms from bacteria to human. AQPs mainly involved in the transmembrane diffusion of water as well as various small solutes in a bidirectional manner are widely distributed in various human tissues. Human contains 13 AQPs (AQP0-AQP12) which are divided into three sub-classes namely orthodox aquaporin (AQP0, 1, 2, 4, 5, 6, and 8), aquaglyceroporin (AQP3, 7, 9, and 10) and super or unorthodox aquaporin (AQP11 and 12) based on their pore selectivity. Human AQPs are functionally diverse, which are involved in wide variety of non-infectious diseases including cancer, renal dysfunction, neurological disorder, epilepsy, skin disease, metabolic syndrome, and even cardiac diseases. However, the association of AQPs with infectious diseases has not been fully evaluated. Several studies have unveiled that AQPs can be regulated by microbial and parasitic infections that suggest their involvement in microbial pathogenesis, inflammation-associated responses and AQP-mediated cell water homeostasis. This review mainly aims to shed light on the involvement of AQPs in infectious and non-infectious diseases and potential AQPs-target modulators. Furthermore, AQP structures, tissue-specific distributions and their physiological relevance, functional diversity and regulations have been discussed. Altogether, this review would be useful for further investigation of AQPs as a potential therapeutic target for treatment of infectious as well as non-infectious diseases.

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.

Dexmedetomidine Attenuates Lung Injury in Toxic Shock Rats by Inhibiting Inflammation and Autophagy

OBJECTIVE

To explore the mechanisms whereby dexmedetomidine reversed lung injury in rats with toxic shock via inhibiting inflammation and autophagy.

METHODS

Thirty-six specific pathogen-free male Sprague Dawley rats with were screened and randomly divided into three groups. Toxic shock was induced by intestinal leakage. The control group received no cecal ligation and the treatment group received dexmedetomidine hydrochloride. Lung tissue morphology was studied by hematoxylin-eosin staining. The expression levels of inflammatory cytokines including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR). The expression levels of beclin l and LC3 were measured, and the expression levels of apoptosis gene Bax and Bcl-2 were determined. The autophagosomes in lung cells were observed by transmission electron microscopy. Extracellular signal-regulated kinase (ERK) 1/2 expression was determined by Western blotting assays.

RESULTS

The results showed that the W/D, total protein and myeloperoxidase (MPO) index in the toxic shock group were 5.45 ± 0.35, 3.21 ± 0.47 and 4.53 ± 0.36, respectively. The W/D (4.02 ± 0.67), total protein (2.01 ± 0.35) and MPO index (2.31 ± 0.59) were significantly lower in the dexmedetomidine group (p <0.05). Similarly, compared with the toxic shock group, the expression of p-ERK1/2 protein in the dexmedetomidine treatment group was significantly decreased (p <0.05). The expression levels of autophagy proteins beclin1 and LC3 in the dexmedetomidine treatment group were not significantly different from those of the control group (p >0.05). Transmission electron microscopy showed that the number of autophagic bodies in lung cells decreased. After induction with dexmedetomidine hydrochloride, the proapoptotic gene Bax was significantly downregulated in the cells. Bax expression levels in each group were 0.36 ± 0.12, 0.67 ± 0.06, and 0.32 ± 0.12, respectively. Compared with the control group, Bax expression in lung tissue significantly increased in the toxic shock group (p <0.05).

CONCLUSION

Dexmedetomidine attenuates lung injury in toxic shock rats by inhibiting inflammation and autophagy.

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.

Aquaporins in health and disease

Aquaporins (AQPs) are transmembrane channel proteins that mainly facilitate the water translocation through the plasma cell membrane. For several years these proteins have been extensively examined for their biologic role in health and their potential implication in different diseases. Technological improvements associated with the methods employed to evaluate the functions of the AQPs have provided us with significant new knowledge. In this chapter, we will examine the role of AQPs in health and disease based on the latest currently available evidence.

Hypoxia-Induced Aquaporin-3 Changes Hepatocellular Carcinoma Cell Sensitivity to Sorafenib by Activating the PI3K/Akt Signaling Pathway

Purpose

Hypoxia-induced changes are primarily activated in patients with hepatocellular carcinoma (HCC) and long-term sorafenib exposure, thereby reducing the sensitivity to the drug. Aquaporin-3 (AQP3), a member of the aquaporin family, is a hypoxia-induced substance that affects the chemosensitivity of non-hepatocellular tumors. However, its expression and role in the sensitivity of hypoxic HCC cells to sorafenib-induced apoptosis remain unclear. The purpose of this study was to detect changes in AQP3 expression in hypoxic HCC cells and to determine whether these changes alter the sensitivity of these cells to sorafenib.

Materials and Methods

Huh7 and HepG2 hypoxic cell models were established and AQP3 expression was detected using quantitative real-time polymerase chain reaction (qPCR) and Western blotting. Furthermore, the role of AQP3 in cell sensitivity to sorafenib was evaluated via flow cytometry, Western blotting, and a CCK-8 assay.

Results

The results of qPCR and Western blotting showed that AQP3 was overexpressed in the Huh7 and HepG2 hypoxic cell models. Furthermore, AQP3 protein levels were positively correlated with hypoxia-inducible factor-1α (HIF-1α) levels. Compared with cells transfected with lentivirus-GFP (Lv-GFP), hypoxic cells transfected with lentivirus-AQP3 (Lv-AQP3) were less sensitive to sorafenib-induced apoptosis. However, the sensitivity to the drug increased in cells transfected with lentivirus-AQP3RNAi (Lv-AQP3RNAi). Akt and Erk phosphorylation was enhanced in Lv-AQP3-transfected cells. Compared with UO126 (a Mek1/2 inhibitor), LY294002 (a PI3K inhibitor) attenuated the AQP3-induced insensitivity to sorafenib observed in hypoxic cells transfected with Lv-AQP3. Combined with LY294002-treated cells, hypoxic cells transfected with Lv-AQP3RNAi were more sensitive to sorafenib.

Conclusion

The study results show that AQP3 is a potential therapeutic target for improving the sensitivity of hypoxic HCC cells to sorafenib.

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.

Aquaporin expression in breast cancer and their involvement in bleb formation, cell motility and invasion in endocrine resistant variant cells

Estrogen receptor (ER)‑silenced breast cancer cell lines exhibit endocrine resistance and morphological changes from an epithelial to a mesenchymal phenotype. These cells also display increased motility and invasive properties that are further accentuated by exposure to an alkaline pH, exhibiting dynamic plasma membrane blebbing and cytoplasmic streaming. These latter morphological changes are hypothesized to involve substantial water movement across the plasma membrane, contributing to bleb formation; this may involve aquaporin channel proteins (AQPs). AQP 1, 3, 4 and 5 expression/localization was examined via reverse transcription‑quantitative PCR, western blotting and confocal microscopy in endocrine‑sensitive (YS1.2) and ‑resistant (pII and MDA‑MB‑231) breast cancer cells, as well as normal breast epithelial cells (MCF10A). The effects of osmotic changes on bleb formation were examined via live cell imaging. AQP3 protein expression was knocked down by small interfering RNA (siRNA) transfection, and the effect of its reduced expression on bleb formation, cell motility and invasion were determined via immunofluorescence, scratch and Cultrex assays, respectively. Expression of the four AQPs varied across the different cell lines, and exhibited nuclear, cytoplasmic and membranous localization. Osmotic changes affected the formation of blebs. In pII cells exposed to alkaline pH, AQP3 was observed to be redistributed from the nucleus into the newly formed blebs. siRNA‑mediated knockdown of AQP3 in pII cells significantly reduced cellular blebbing induced by alkaline pH, as well as motility and invasion. These data suggested that AQP3, and potentially other aquaporins, may participate in the processes leading to blebbing of endocrine‑resistant cells which is proposed to be a mechanism that drives tumor metastasis.

The regulatory roles of aquaporins in the digestive system

Aquaporins (AQPs) are highly conserved small transmembrane proteins, which are responsible for the water transport across the cell membrane. AQPs are abundantly expressed in numerous types of cells such as epithelial and endothelial cells. The expression of AQP-1, -3, -4, -5, -8 and -9 were found in the digestive system, where these six AQP isoforms serve essential roles including mediating the transmembrane water transport and regulating the secretion of gastrointestinal (GI) fluids, consequently facilitating the digestion and absorption of GI contents. In addition, the expression levels of AQPs are controlled by various factors, and AQPs can stimulate numerous signaling pathways; however, aberrant expression of AQPs in the GI tracts are associated with the initiation and development of numerous diseases. Thus, this review provides an overview of the expression and functions of AQPs in the digestive system.

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.

Aquaporin 3 maintains the stemness of CD133+ hepatocellular carcinoma cells by activating STAT3

An increasing interest in liver cancer stemness arises owing to its aggressive behavior and poor prognosis. CD133, a widely known liver cancer stem cell marker, plays critical roles in the maintenance of liver cancer stemness. Thus, exploring the regulatory mechanism of CD133 expression is significant. In the present study, we proved the carcinogenesis roles of aquaporin 3 (AQP3) in hepatocellular carcinoma (HCC) and demonstrated that AQP3 promotes the stem cell-like properties of hepatoma cells by regulating CD133 expression. In addition, AQP3 promoted the stimulation and nuclear translocation of signal transducer and activator of transcription 3 (STAT3) with a subsequent increase in the level of CD133 promoter-acetylated histone H3. This phenomenon accelerated CD133 transcription. Next, whether AQP3 acted as an oncogenic gene in HCC and maintained the stemness of CD133+ hepatoma cells were elucidated; also, a novel mechanism underlying the AQP3/STAT3/CD133 pathway in HCC was deduced.

LMP2A induces DNA methylation and expression repression of AQP3 in EBV-associated gastric carcinoma

Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) is a unique type of gastric carcinomas that promoter hypermethylation of tumor-related genes is extremely frequent to be found. Aquaporin 3 (AQP3) is a small membrane transport protein that plays a crucial role in cancer progression and metastasis. However, there is no experimental study on the expression of AQP3 in EBVaGC and the regulation mechanism of EBV on AQP3. In this study, the loss of AQP3 was contributed by the hypermethylation status of AQP3 promoter in EBVaGC which was caused by elevated expression of DNMT3a. In addition, stable and transient transfection system in SGC7901 showed that viral latent membrane protein 2A (LMP2A) activated phosphorylated ERK and up-regulated DNMT3a. Taken together, LMP2A induced the phosphorylation of ERK, which activated DNMT3a transcription and caused AQP3 expression loss through CpG island methylation of AQP3 promoter in EBVaGC.

Peroxiporins in Cancer

The transport of H₂O₂ across membranes by specific aquaporins (AQPs) has been considered the last milestone in the timeline of hydrogen peroxide discoveries in biochemistry. According to its concentration and localization, H₂O₂ can be dangerous or acts as a signaling molecule in various cellular processes as either a paracrine (intercellular) and/or an autocrine (intracellular) signal. In this review, we investigate and critically examine the available information on AQP isoforms able to facilitate H₂O₂ across biological membranes (“peroxiporins”), focusing in particular on their role in cancer. Moreover, the ability of natural compounds to modulate expression and/or activity of peroxiporins is schematically reported and discussed.

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.

Circular RNAs: Characteristics, Function and Clinical Significance in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC patients are commonly diagnosed at an advanced stage, for which highly effective therapies are limited. Moreover, the five-year survival rate of HCC patients remains poor due to high frequency of tumor metastasis and recurrence. These challenges give rise to the emergent need to discover promising biomarkers for HCC diagnosis and identify novel targets for HCC therapy. Circular RNAs (circRNAs), a class of long-overlook non-coding RNA, have been revealed as multi-functional RNAs in recent years. Growing evidence indicates that circRNA expression alterations have a broad impact in biological characteristics of HCC. Most of these circRNAs regulate HCC progression by acting as miRNA sponges, suggesting that circRNAs may function as promising diagnostic biomarkers and ideal therapeutic targets for HCC. In this review, we summarize the current progress in studying the functional role of circRNAs in HCC pathogenesis and present their potential values as diagnostic biomarkers and therapeutic targets. In-depth investigations on the function and mechanism of circRNAs in HCC will enrich our knowledge of HCC pathogenesis and contribute to the development of effective diagnostic biomarkers and therapeutic targets for HCC.

Different Prognostic Implications of Aquaporin-1 and Aquaporin-5 Expression among Different Histological Types of Ovarian Carcinoma

The aquaporins (AQPs) are a family of transmembrane water channel proteins that are distributed in various human tissues. Recent studies have suggested that AQP expression correlates with various aspects of cancer biology that determine the aggressiveness of different cancers. Ovarian carcinoma is one of the most lethal gynecological cancers. Some studies have suggested that AQPs are expressed in ovarian carcinoma, and are associated with cancer cell growth and migration. In this study, we immunohistochemically evaluated the expression of AQP1, 3, 5, and 9 in a total of 300 ovarian carcinomas using tissue microarrays. In our analyses of correlations between aquaporin expression and overall survival, high AQP5 expression was significantly associated with poorer prognosis (P = 0.029). For AQP1, the low expression group trended towards poorer prognosis than the high expression group, but the difference was not statistically significant. When ovarian carcinomas were divided by histological types, high AQP5 expression correlated with poorer prognosis in serous carcinoma (P = 0.015), and low AQP1 expression correlated with poorer prognosis in clear cell carcinomas (P = 0.0055). By contrast, high AQP1 expression correlated with poorer prognosis in mucinous carcinoma (P = 0.0001) and endometrioid carcinoma (P = 0.021). Our studies suggest that AQPs can be useful prognostic markers in ovarian carcinoma, but their correlation with prognosis depends on the histological type of ovarian carcinoma.

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.

Expression of AQP3 and AQP5 as a prognostic marker in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a common type of breast malignancy with high a propensity for metastasis and locoregional recurrence. The aim of the present study was to investigate the expression of aquaporin (AQP) 3 and AQP5, analyze their association with clinicopathological parameters and explore their clinical significance in tissue samples from patients with TNBC. Immunohistochemistry was performed to detect the expression patterns of AQP3 and AQP5 in 96 patients with TNBC who underwent surgery between 2007 and 2012. AQP3 and AQP5 were expressed primarily in the membrane and cytoplasm of tumor cells within TNBC tissues. AQP3 and AQP5 expression was notably stronger in carcinoma tissue compared with adjacent normal tissue. Overexpression of AQP3 and AQP5 was significantly associated with tumor size, lymph node status and local relapse/distant metastasis. In addition, aberrant overexpression of AQP5 was observed more frequently in TNBC tissues with higher Ki-67 expression than in those with lower Ki-67 expression. In univariate analysis, patients with TNBC with high AQP3 and AQP5 expression demonstrated poorer 5-year disease-free survival and overall survival compared with patients with low AQP3 and AQP5 expression. In multivariate analysis, the combined expression of AQP3 and AQP5 was an independent prognostic marker in patients with TNBC. The results of the present study suggest that the overexpression of AQP3 and AQP5 may serve as a novel therapeutic marker in patients with TNBC.

Prognostic values of aquaporins mRNA expression in human ovarian cancer

Aquaporins (AQPs), a family of transmembrane channel, are composed of 13 identified members (AQP0–12). Accumulating evidences reported that AQPs were correlated with various biological roles and represented a prognostic predictor in various cancer types. However, the prognostic value of AQPs expression in ovarian cancer remains unclear. Using ‘Kaplan–Meier plotter’ (KM plotter) online database, we explored the predictive prognostic value of individual AQPs members’ mRNA expression to overall survival (OS) in different clinical data, such as histology, pathological grades, clinical stages, TP53 status, and applied chemotherapy in ovarian cancer patients. Our results revealed that higher AQP0, AQP1, and AQP4 mRNA expression were correlated with poor OS, whereas higher AQP3, AQP5, AQP6, AQP8, AQP10, and AQP11 showed better OS in ovarian cancer patients. Moreover, AQP4 and AQP8 showed poor OS in TP53-mutated ovarian cancer patients and AQP1 presented unfavorable OS in both TP53 mutated and wild ovarian cancer patients. Additionally, AQP3, AQP6, and AQP11 mRNA expression were correlated with better OS, whereas AQP0 and AQP1 showed poor OS in all ovarian cancer patients treated with Platin, Taxol, and Taxol + Platin chemotherapy. AQP5, AQP8, and AQP10 were associated with improved OS, however, AQP4 predicted unfavorable OS in all patients treated with Platin chemotherapy. Our results suggest that individual AQPs, except AQP2 and AQP9, are associated with unique prognostic significance and may thus act as new predictive prognostic indicators and potential drug therapeutic target in ovarian cancer.

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.

AQP8 inhibits colorectal cancer growth and metastasis by down-regulating PI3K/AKT signaling and PCDH7 expression

Colorectal cancer (CRC) is one of the most common malignant cancers and the leading cause of cancer-related deaths in worldwide. Although the monoclonal antibody therapy is prescribed for CRC, the metastasis resistant to therapy is the major cause of death of patients with CRC, which indicating the urgent demands for new therapeutic targets discovery. Aquaporin 8 (AQP8) has been identified alter expressed in several cancers including breast cancer, lung cancer and prostatic carcinoma. Our study demonstrated the functional significance of AQP8 in CRC cells growth and metastasis. Over-expression of AQP8 remarkably decreased growth, aggressiveness and colony formation in the CRC SW480 and HT-29 cells. Mechanistically, AQP8 over-expression inhibited tumorigenic phenotype by inactivating PI3K/AKT signaling and inhibiting PCDH7 expression. Furthermore, in vivo studies using nude mice xenograft and metastasis model identified the pivotal role of AQP8 in CRC cells growth and metastasis. Taken together, the present study verifies the vital role of the endogenous AQP8 in colorectal cancer progression.

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.

Aquaporin-3 in Cancer

Increasing evidence suggests that the water/glycerol channel aquaporin-3 (AQP3) plays a pivotal role in cancer metastasis. AQP3 knockout mice were resistant to skin tumor formation and overexpression correlated with metastasis and poor prognosis in patients with breast or gastric cancer. In cultured cancer cells, increased AQP3 expression stimulated several intracellular signaling pathways and resulted in increased cell proliferation, migration, and invasion as well as aggravation of epithelial-to-mesenchymal transition. Besides AQP facilitated water transport at the leading edge of migrating cells, AQP3 signaling mechanisms are beginning to be unraveled. Here, we give a thorough review of current knowledge regarding AQP3 expression in cancer and how AQP3 contributes to cancer progression via signaling that modulates cellular mechanisms. This review article will expand our understanding of the known pathophysiological findings regarding AQP3 in cancer.

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.

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.

Heat shock exerts anticancer effects on liver cancer via autophagic degradation of aquaporin 5

Previous studies described that the expression of aquaporin 5 (AQP5) was altered in tumors of various organs. AQP5 is attracting attention as a new cancer therapeutic target. In the present study, heat shock-induced changes in AQP5 expression were evaluated by immunofluorescent staining (IF) and western blotting (WB) of liver cancer cells. AQP5 knockdown experiments or a heat shock treatment were conducted, and their effects on cell volume, proliferation, cell cycle, the activity of apoptosis and migration/invasion were compared. Cycloheximide (CHX) chase experiments and double IF of AQP5 and light chain 3B (LC3B) were performed to investigate the mechanisms underlying changes in AQP5 expression. The results showed that IF and WB revealed decrease in AQP5 expression on cellular membranes and in the cytoplasm of heated cells. AQP5 knockdown and heat shock similarly decreased cell volume, suppressed migration/invasion and proliferation, and induced early apoptosis and partial G0/G1 arrest. CHX chase experiments revealed that heat shock accelerated the degradation of AQP5, which was rescued under CHX and the autophagy inhibitor, bafilomycin A1 (BafA1). Double IF showed the co-localization of AQP5 and LC3B on BafA1-treated heated cells. In conclusion, we demonstrated that heat shock decreased AQP5 on cellular membranes and in the cytoplasm by activating autophagic degradation, and heat shock and AQP5 knockdown exerted similar anticancer effects, suggesting that heat shock exerts anticancer effects via the autophagic degradation of AQP5.

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.

Inhibition of AQP1 Hampers Osteosarcoma and Hepatocellular Carcinoma Progression Mediated by Bone Marrow-Derived Mesenchymal Stem Cells

The complex cross-talk between tumor cells and their surrounding stromal environment plays a key role in the pathogenesis of cancer. Among several cell types that constitute the tumor stroma, bone marrow-derived mesenchymal stem cells (BM-MSCs) selectively migrate toward the tumor microenvironment and contribute to the active formation of tumor-associated stroma. Therefore, here we elucidate the involvement of BM-MSCs to promote osteosarcoma (OS) and hepatocellular carcinoma (HCC) cells migration and invasion and deepening the role of specific pathways. We analyzed the function of aquaporin 1 (AQP1), a water channel known to promote metastasis and neoangiogenes. AQP1 protein levels were analyzed in OS (U2OS) and HCC (SNU-398) cells exposed to conditioned medium from BM-MSCs. Tumor cell migration and invasion in response to BM-MSC conditioned medium were evaluated through a wound healing assay and Boyden chamber, respectively. The results showed that the AQP1 level was increased in both tumor cell lines after treatment with BM-MSC conditioned medium. Moreover, BM-MSCs-mediated tumor cell migration and invasion were hampered after treatment with AQP1 inhibitor. These data suggest that the recruitment of human BM-MSCs into the tumor microenvironment might cause OS and HCC cell migration and invasion through involvement of AQP1.

Urine AQP5 is a potential novel biomarker of diabetic nephropathy

AIMS

To investigate if urinary AQP5 serves as a new potential biomarker of diabetic nephropathy.

METHODS

Using an AQP5-specific enzyme-linked immunosorbent assay, we measured serum and urine AQP5 first in a cohort consisting of normal controls (n=26) and patients with diabetes mellitus (n=25) or diabetic nephropathy (n=33) and then in a validation cohort possessing normal controls (n=10), patients with diabetes mellitus (n=10) or diabetic nephropathy (n=14), and patients with chronic kidney disease of unknown etiology (n=10). We used various statistical methods including Pearson's correlation coefficient, ANOVA with Holm-Sidak test, Receiver Operator Curve, and multiple logistic regression to analyze the data.

RESULTS

Urine AQP5/creatinine 1) is significantly higher in diabetic nephropathy than in other two groups, and in diabetic nephropathy stage V than in stage III; 2) correlates with serum creatinine, urine albumin, and multiple other known risk factors of the disease; and 3) improves the clinical models in distinguishing diabetic nephropathy from normal controls and diabetic mellitus.

CONCLUSION

Our data suggest that urine AQP5/creatinine may possess diagnostic and prognostic values as a biomarker of diabetic nephropathy.

Expression and clinical significance of aquaglyceroporins in human hepatocellular carcinoma

Aquaglyceroporins (AQPs) are a subset of the aquaporin family, and are permeable to water and glycerol. The aim of the present study was to determine the expression and clinical significance of three AQPs, AQP3, 7 and 9 in hepatocellular carcinoma (HCC). Fresh HCC and adjacent non‑tumorous liver tissues were collected from 68 patients diagnosed with HCC. The expression levels of AQP3, 7 and 9 were detected by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemical analysis. The association between the expression of AQPs and clinicopathological parameters of HCC were investigated. Compared with non‑tumorous liver tissue, HCC tissues exhibited a significant (P<0.05) increase in the expression of AQP3 and a concomitant reduction in the expression levels of AQP7 and AQP9, at both the mRNA and protein levels. Immunohistochemistry revealed that AQP9 was dominantly localized on the plasma membrane of hepatocytes, while AQP3 and AQP7 exhibited a predominantly cytoplasmic and nuclear distribution. High expression of AQP3 was significantly (P<0.05) associated with low expression levels of AQP7 and AQP9. High expression of AQP3 was correlated with tumor grade (P=0.017), tumor stage (P=0.010) and lymphatic metastasis (P=0.031). Low expression of AQP7 was correlated with tumor grade (P=0.043). AQP3 was upregulated, and AQP7 and AQP9 were downregulated in HCC. A high expression of AQP3 and low expression of AQP7 was significantly associated with the aggressive features of HCC.

Aquaporin 3 is regulated by estrogen in the chicken oviduct and is involved in progression of epithelial cell-derived ovarian carcinomas

Aquaporins (AQPs) are membrane proteins that passively deliver water across the plasma membrane to play an important role in maintaining cell shape. Members of the AQP family are distributed in most of the tissues in the human body and perform a variety of functions based on the water homeostasis suitable for each organ. However, there is little known about the expression and regulation of AQP family members in chickens. Therefore, we determined the expression of AQPs in various tissues of chickens. Among 13 isotypes, AQP3 was highly expressed in the chicken oviduct. Expression of AQP3 messenger RNA (mRNA) increased in the magnum (P < 0.001) and isthmus (P < 0.001) of chick oviducts treated with diethylstilbestrol. Consistent with these results, the localization of AQP3 was detected in the glandular and luminal epithelia of the magnum and isthmus of oviducts of diethylstilbestrol-treated chicks. In addition, the pattern of expression of AQP3 changed in an estrogen-dependent manner during the molting period. During the regenerative period of the oviduct after molting, expression of AQP3 mRNA increased coordinately with increasing concentrations of estradiol (P < 0.001), whereas expression of AQP3 mRNA decreased as concentrations of estradiol in plasma decreased in response to induced molting (P < 0.001). Also, expression of the AQP3 increased (P < 0.001) in cancerous ovaries of laying hens. In conclusion, AQP3 does not simply function to transport water into and out of cells but also appears to be closely involved in development of the chicken oviduct, which is regulated by estrogens. Furthermore, our results suggest AQP3 as a new diagnostic for early detection and treatment of epithelial cell-derived ovarian carcinomas.