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

The water channels aquaporin-1 and aquaporin-3 interact with and affect the cell polarity protein Scribble in 3D in vitro models of breast cancer

Cellular changes in carcinomas include alterations in cell proliferation, cell migration, cell-cell adhesion, and cellular polarity. In vitro studies have revealed that the water channels, aquaporin-1 (AQP1) and AQP3, can influence cell migration and cell-cell adhesion. Of note, we previously showed that AQP1 overexpression reduced levels of cell-cell adhesion proteins, whereas AQP3 increased levels when overexpressed in normal epithelial cells. Expression of AQP1 and AQP3 in breast carcinoma is associated with lymph node metastasis, recurrence, and poor survival of patients with breast cancer. In this study, we investigated if AQP1 and AQP3 affected cell polarity in breast cancer by studying the relationship between the major polarity protein Scribble and AQP1 and AQP3. In breast cancer tissue samples, the protein expression of AQP1, AQP3, and Scribble did not show an obvious correlation. However, in a GST pull-down assay, AQP1 and AQP3 interacted with Scribble. AQP1 overexpression reduced the size of 3D spheroids as well as reduced Scribble levels at cell-cell contacts, whereas AQP3 overexpression showed no significant change in spheroid size compared with control, AQP3 overexpression also reduced Scribble levels at cell-cell contacts. Of note, AQP1 overexpression increased cell migration and induced cell detachment and dissemination from migrating breast cancer cell sheets, whereas AQP3 overexpression did not. Thus, AQP1 and AQP3 differentially affect 3D-grown breast cancer spheroids, and especially AQP1 may contribute to cancer development and spread via negatively affecting cellular junctions and cell polarity proteins as well as increasing cell migration and cell detachment.NEW & NOTEWORTHY Overexpression of the water channels aquaporin-1 and aquaporin-3 reduced levels of the key polarity protein Scribble at cell-cell junctions, suggesting potential implications in breast cancer progression and metastasis.

Expression patterns of aquaporins 1, 3, 5 in canine mammary gland carcinomas

Aquaporins (AQPs) are water channel proteins, and the expression of AQPs in carcinoma cells has received much attention over the last 15 years. In the veterinary field, however, little is known about the expression of AQPs. In the present study using immunohistochemistry, we examined the expression of AQP1, AQP3, and AQP5 in canine mammary gland carcinomas. The 27 samples comprised 10 grade I, 12 grade II, and 5 grade III samples (See Materials and Methods section for grade classification method). AQP1 was expressed in only 2 of the grade III carcinomas, and the expression was limited to spindle-shaped cells in the solid structure and on the outside of the solid mass. AQP3-positive cells were observed in 20 of 22 grade I and II samples. On the other hand, among grade III carcinomas, AQP3 was expressed only in spindle-shaped cells in 1 sample. AQP5 was expressed in all grade I and II carcinomas but not in the grade III tumors. In addition, enhanced expression of basolateral AQP3 and apical AQP5 was observed in lobular hyperplastic cells. These results suggest that the expression patterns of AQP3 and AQP5 can be of help for judging the grading of canine mammary tumors and that AQP1 is likely to be involved in metastasis. Moreover, AQP3 and AQP5 might be relevant to lactation in female dogs.

Potential Galactagogue Effect of Tri-Than-Thip Remedy on Milk Synthesis in Lactating Rats: Impact on Milk Production-Related Parameters

Herbal galactagogues have been widely used as a treatment for postpartum hypogalactia due to the potential side effects associated with pharmacological therapy. Tri-Than-Thip (Tri-TT) is a Thai herbal medicine remedy that contains three main components: Cassia fistula, Pithecellobium dulce, and Ficus benjamina. These components are believed to have properties that contribute to milk production. However, despite the traditional use of Tri-TT, there is a lack of academic evidence supporting its efficacy in enhancing milk production. Therefore, the purpose of this study was to investigate the effect of Tri-TT on milk production and determine if it has a galactagogue effect. The weight suckle weight model was used to determine total milk production in lactating rats, while histological analysis was performed to assess the alveolar diameter of the mammary gland. The findings of this study revealed a significant increase in total milk production among lactating rats treated with 500 mg/kg of Tri-TT, compared to the control group. Furthermore, both the Tri-TT and Domperidone-treated groups exhibited a larger alveolar diameter of the mammary gland in comparison to the control group. In summary, these findings provide supportive evidence for the galactagogue activity of Tri-TT. The observed enhancement in milk production may be associated with Tri-TT could potentially be attributed to its ability to widen the alveolar diameter of the mammary gland, thereby facilitating increased milk volume.

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.

Aquaporins: New players in breast cancer progression and treatment response

Aquaporins (AQPs) are a family of small transmembrane proteins that selectively transport water and other small molecules and ions following an osmotic gradient across cell plasma membranes. This enables them to regulate numerous functions including water homeostasis, fat metabolism, proliferation, migration, and adhesion. Previous structural and functional studies highlight a strong biological relationship between AQP protein expression, localization, and key biological functions in normal and cancer tissues, where aberrant AQP expression correlates with tumorigenesis and metastasis. In this review, we discuss the roles of AQP1, AQP3, AQP4, AQP5, and AQP7 in breast cancer progression and metastasis, including the role of AQPs in the tumor microenvironment, to highlight potential contributions of stromal-derived to epithelial-derived AQPs to breast cancer. Emerging evidence identifies AQPs as predictors of response to cancer therapy and as targets for increasing their sensitivity to treatment. However, these studies have not evaluated the requirements for protein structure on AQP function within the context of breast cancer. We also examine how AQPs contribute to a patient's response to cancer treatment, existing AQP inhibitors and how AQPs could serve as novel predictive biomarkers of therapy response in breast cancer. Future studies also should evaluate AQP redundancy and compensation as mechanisms used to overcome aberrant AQP function. This review highlights the need for additional research into how AQPs contribute molecularly to therapeutic resistance and by altering the tumor microenvironment.

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.

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.

Comparisons of Forecasting for Survival Outcome for Head and Neck Squamous Cell Carcinoma by using Machine Learning Models based on Multi-omics

Background: Machine learning methods showed excellent predictive ability in a wide range of fields. For the survival of head and neck squamous cell carcinoma (HNSC), its multi-omics influence is crucial. This study attempts to establish a variety of machine learning multi-omics models to predict the survival of HNSC and find the most suitable machine learning prediction method. Methods: The HNSC clinical data and multi-omics data were downloaded from the TCGA database. The important variables were screened by the LASSO algorithm. We used a total of 12 supervised machine learning models to predict the outcome of HNSC survival and compared the results. In vitro qPCR was performed to verify core genes predicted by the random forest algorithm. Results: For omics of HNSC, the results of the twelve models showed that the performance of multi-omics was better than each single-omic alone. Results were presented, which showed that the Bayesian network(BN) model (area under the curve [AUC] 0.8250, F1 score=0.7917) and random forest(RF) model (area under the curve [AUC] 0.8002,F1 score=0.7839) played good prediction performance in HNSC multi-omics data. The results of in vitro qPCR were consistent with the RF algorithm. Conclusion: Machine learning methods could better forecast the survival outcome of HNSC. Meanwhile, this study found that the BN model and the RF model were the most superior. Moreover, the forecast result of multi-omics was better than single-omic alone in HNSC.

Circular RNA Circ-STIL Contributes to Cell Growth and Metastasis in Hepatocellular Carcinoma via Regulating miR-345-5p/AQP3 Axis

BACKGROUND

Circular RNAs (circRNAs) are implicated in the pathogenesis and development of hepatocellular carcinoma (HCC). However, the function and latent mechanism of circ-STIL in HCC have not been elucidated.

AIMS

This study was designed to explore the precise role and underlying molecular mechanism of circ-STIL in HCC advancement.

METHODS

The expression levels of circ-STIL, SCL/TAL1 interrupting locus (STIL), miR-345-5p and aquaporin-3 (AQP3) were measured by quantitative real-time polymerase chain reaction or western blot. Cell proliferation was assessed by 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay. Cell apoptosis was analyzed by flow cytometry. Transwell assay was conducted to analyze cell migratory and invasive capacities. The interactions among circ-STIL, miR-345-5p and AQP3 were confirmed by dual-luciferase reporter and RNA immunoprecipitation assays. Xenograft tumor model was established to analyze the role of circ-STIL in HCC in vivo.

RESULTS

Circ-STIL was upregulated in HCC tissues and cells. Circ-STIL knockdown inhibited HCC cell progression by reducing cell proliferation, migration and invasion and promoting cell apoptosis. MiR-345-5p was a direct target of circ-STIL, and AQP3 was targeted by miR-345-5p in HCC. Circ-STIL knockdown or miR-345-5p overexpression impeded cell malignant behaviors in HCC cells, and the effects could be reversed by miR-345-5p silence or AQP3 enhancement, respectively. Meanwhile, circ-STIL regulated AQP3 expression by sponging miR-345-5p. Besides, circ-STIL downregulation retarded HCC tumor growth in vivo.

CONCLUSION

Circ-STIL knockdown suppressed HCC development by regulating miR-345-5p/AQP3 pathway, which might provide a promising target for HCC therapy.

Cellular Distribution of Brain Aquaporins and Their Contribution to Cerebrospinal Fluid Homeostasis and Hydrocephalus

Brain aquaporins facilitate the movement of water between the four water compartments: blood, cerebrospinal fluid, interstitial fluid, and intracellular fluid. This work analyzes the expression of the four most abundant aquaporins (AQPs) (AQP1, AQP4, AQP9, and AQP11) in the brains of mice and discuss their contribution to hydrocephalus. We analyzed available data from single-cell RNA sequencing of the central nervous system of mice to describe the expression of aquaporins and compare their distribution with that based on qPCR, western blot, and immunohistochemistry assays. Expression of AQP1 in the apical cell membrane of choroid plexus epithelial cells and of AQP4 in ependymal cells, glia limitans, and astrocyte processes in the pericapillary end foot is consistent with the involvement of both proteins in cerebrospinal fluid homeostasis. The expression of both aquaporins compensates for experimentally induced hydrocephalus in the animals. Recent data demonstrate that hypoxia in aged animals alters AQP4 expression in the choroidal plexus and cortex, increasing the ventricle size and intraventricular pressure. Cerebral distensibility is reduced in parallel with a reduction in cerebrospinal fluid drainage and cognitive deterioration. We propose that aged mice chronically exposed to hypoxia represent an excellent experimental model for studying the pathophysiological characteristics of idiopathic normal pressure hydrocephalus and roles for AQPs in such disease.

Expression and Significance of AQP3 in Cutaneous Lesions

Aquaporin 3 (AQP3) is the membrane channel of water and involved in fluid homeostasis. The aim of this study was to reveal the expression and significance of AQP3 in cutaneous lesions. We analyzed AQP3 mRNA levels using RT-PCR in 311 cutaneous lesions and confirmed AQP3 expression in these lesions by immunohistochemistry. AQP3 mRNA was detected in normal epidermis, seborrheic keratosis, solar keratosis, Bowen's disease, squamous cell carcinoma, eccrine poroma, apocrine carcinoma, and sebaceoma; however, AQP3 mRNA was absent in basal cell carcinoma, nevocellular nevus, or malignant melanoma. By immunohistochemistry, diffuse AQP3 expression was seen in all keratotic lesions including seborrheic keratosis, verruca vulgaris, molluscum contagiosum, solar keratosis, Bowen's disease, and squamous cell carcinoma. Diffuse AQP3 expression was also present in all extramammary Paget's disease. No AQP3 staining was obtained in basal cell carcinoma. Positive AQP3 staining was seen in sweat gland tumors including hidradenoma, eccrine poroma, and apocrine carcinoma. Among sebaceous tumors, AQP3 expressed diffusely in all sebaceous hyperplasia and sebaceous adenoma, but not in sebaceous carcinomas. Only focal AQP3 staining was seen in nevocellular nevus and no AQP3 staining in melanoma. Our findings indicate the function of AQP3 maintained in most skin tumors. AQP3 may be used for differential diagnosis in skin tumors.

Are There Limits in Explainability of Prognostic Biomarkers? Scrutinizing Biological Utility of Established Signatures

Prognostic biomarkers can have an important role in the clinical practice because they allow stratification of patients in terms of predicting the outcome of a disorder. Obstacles for developing such markers include lack of robustness when using different data sets and limited concordance among similar signatures. In this paper, we highlight a new problem that relates to the biological meaning of already established prognostic gene expression signatures. Specifically, it is commonly assumed that prognostic markers provide sensible biological information and molecular explanations about the underlying disorder. However, recent studies on prognostic biomarkers investigating 80 established signatures of breast and prostate cancer demonstrated that this is not the case. We will show that this surprising result is related to the distinction between causal models and predictive models and the obfuscating usage of these models in the biomedical literature. Furthermore, we suggest a falsification procedure for studies aiming to establish a prognostic signature to safeguard against false expectations with respect to biological utility.

Inhibition of aquaporins as a potential adjunct to breast cancer cryotherapy

Cryoablation is an emerging type of treatment for cancer. The sensitization of tumors using cryosensitizing agents prior to treatment enhances ablation efficiency and may improve clinical outcomes. Water efflux, which is regulated by aquaporin channels, contributes to cancer cell damage achieved through cryoablation. An increase in aquaporin (AQP) 3 is cryoprotective, whereas its inhibition augments cryodamage. The present study aimed to investigate aquaporin (AQP1, AQP3 and AQP5) gene expression and cellular localization in response to cryoinjury. Cultured breast cancer cells (MDA-MB-231 and MCF-7) were exposed to freezing to induce cryoinjury. RNA and protein extracts were then analyzed using reverse transcription-quantitative PCR and western blotting, respectively. Localization of aquaporins was studied using immunocytochemistry. Additionally, cells were transfected with small interfering RNA to silence aquaporin gene expression and cell viability was assessed using the Sulforhodamine B assay. Cryoinjury did not influence gene expression of AQPs, except for a 4-fold increase of AQP1 expression in MDA-MD-231 cells. There were no clear differences in AQP protein expression for either cell lines upon exposure to frozen and non-frozen temperatures, with the exception of fainter AQP5 bands for non-frozen MCF-7 cells. The exposure of cancer cells to freezing temperatures altered the localization of AQP1 and AQP3 proteins in both MCF-7 and MDA-MD-231 cells. The silencing of AQP1, AQP3 and AQP5 exacerbated MDA-MD-231 cell damage associated with freezing compared with control siRNA. This was also observed with AQP3 and AQP5 silencing in MCF-7 cells. Inhibition of aquaporins may potentially enhance cryoinjury. This cryosensitizing process may be used as an adjunct to breast cancer cryotherapy, especially in the border area targeted by cryoablation where freezing temperatures are not cold enough to induce cellular damage.

AQP3 and AQP5-Potential Regulators of Redox Status in Breast Cancer

Breast cancer is still one of the leading causes of mortality in the female population. Despite the campaigns for early detection, the improvement in procedures and treatment, drastic improvement in survival rate is omitted. Discovery of aquaporins, at first described as cellular plumbing system, opened new insights in processes which contribute to cancer cell motility and proliferation. As we discover new pathways activated by aquaporins, the more we realize the complexity of biological processes and the necessity to fully understand the pathways affected by specific aquaporin in order to gain the desired outcome-remission of the disease. Among the 13 human aquaporins, AQP3 and AQP5 were shown to be significantly upregulated in breast cancer indicating their role in the development of this malignancy. Therefore, these two aquaporins will be discussed for their involvement in breast cancer development, regulation of oxidative stress and redox signalling pathways leading to possibly targeting them for new therapies.

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.

Transcriptome Analysis of MDA-MB-231 Cells Treated with Fumosorinone Isolated from Insect Pathogenic Fungi

BACKGROUND

In our previous study, we have isolated a new compound, named Fumosorinone (FU) from insect pathogenic fungi, and was found to inhibit proliferation, migration, and invasion of breast cancer MDA-MB-231 cells.

OBJECTIVE

The aim of this study was to identify the underlying molecular mechanisms for FU effects on MDAMB- 231 cells.

METHODS

After MDA-MB-231 cells were treated with FU for 48h, RNA sequencing was used to identify the effect of FU on the transcriptome of MDA-MB-231 cells. The validation of the relative expression of the selective genes was done using quantitative real-time PCR (qRT-PCR).

RESULTS

The transcriptome results showed that 2733 genes were differentially expressed between the untreated and the FU-treated cells, including 1614 up-regulated and 1119 down-regulated genes. The multiple genes are associated with cancer cell growth, migration, and invasion. Functional analysis identified multitude of pathways related to cancer, such as cell cycle, ECM-receptor interaction, p53 signaling pathway. We selected 4 upregulated and 9 downregulated genes, which are associated with breast cancer to verify their expression using qRT-PCR. The validation showed that HSD3B1, ALOX5, AQP5, COL1A2, CCNB1, CCND1, VCAM-1, PTPN1 and PTPN11 were significantly downregulated while DUSP1, DUSP5, GADD45A, EGR1 were upregulated in FU-treated MDA-MB-231cells.

CONCLUSION

These aberrantly expressed genes and pathways may play pivotal roles in the anti-cancer activity of FU, and maybe potential targets of FU treatments for TNBC. Further investigations are required to evaluate the FU mechanisms of anti-cancer action in vivo.

Targeting Aquaporins in Novel Therapies for Male and Female Breast and Reproductive Cancers

Aquaporins are membrane channels in the broad family of major intrinsic proteins (MIPs), with 13 classes showing tissue-specific distributions in humans. As key physiological modulators of water and solute homeostasis, mutations, and dysfunctions involving aquaporins have been associated with pathologies in all major organs. Increases in aquaporin expression are associated with greater severity of many cancers, particularly in augmenting motility and invasiveness for example in colon cancers and glioblastoma. However, potential roles of altered aquaporin (AQP) function in reproductive cancers have been understudied to date. Published work reviewed here shows distinct classes aquaporin have differential roles in mediating cancer metastasis, angiogenesis, and resistance to apoptosis. Known mechanisms of action of AQPs in other tissues are proving relevant to understanding reproductive cancers. Emerging patterns show AQPs 1, 3, and 5 in particular are highly expressed in breast, endometrial, and ovarian cancers, consistent with their gene regulation by estrogen response elements, and AQPs 3 and 9 in particular are linked with prostate cancer. Continuing work is defining avenues for pharmacological targeting of aquaporins as potential therapies to reduce female and male reproductive cancer cell growth and invasiveness.

Quantitative study of unsaturated transport of glycerol through aquaglyceroporin that has high affinity for glycerol

The structures of several aquaglyceroporins have been resolved to atomic resolution showing two or more glycerols bound inside a channel and confirming a glycerol-facilitator's affinity for its substrate glycerol. However, the kinetics data of glycerol transport experiments all point to unsaturated transport that is characteristic of low substrate affinity in terms of the Michaelis-Menten kinetics. In this article, we present an in silico-in vitro research focused on AQP3, one of the human aquaglyceroporins that is natively expressed in the abundantly available erythrocytes. We conducted 2.1 μs in silico simulations of AQP3 embedded in a model erythrocyte membrane with intracellular-extracellular asymmetries in leaflet lipid compositions and compartment salt ions. From the equilibrium molecular dynamics (MD) simulations, we elucidated the mechanism of glycerol transport at high substrate concentrations. From the steered MD simulations, we computed the Gibbs free-energy profile throughout the AQP3 channel. From the free-energy profile, we quantified the kinetics of glycerol transport that is unsaturated due to glycerol-glycerol interactions mediated by AQP3 resulting in the concerted movement of two glycerol molecules for the transport of one glycerol molecule across the cell membrane. We conducted in vitro experiments on glycerol uptake into human erythrocytes for a wide range of substrate concentrations and various temperatures. The experimental data quantitatively validated our theoretical-computational conclusions on the unsaturated glycerol transport through AQP3 that has high affinity for glycerol.

Pathological role of ion channels and transporters in the development and progression of triple-negative breast cancer

Breast cancer is a common malignancy in women. Among breast cancer types, triple-negative breast cancer (TNBC) tends to affect younger women, is prone to axillary lymph node, lung, and bone metastases; and has a high recurrence rate. Due to a lack of classic biomarkers, the currently available treatments are surgery and chemotherapy; no targeted standard treatment options are available. Therefore, it is urgent to find a novel and effective therapeutic target. As alteration of ion channels and transporters in normal mammary cells may affect cell growth, resulting in the development and progression of TNBC, ion channels and transporters may be promising new therapeutic targets for TNBC. This review summarizes ion channels and transporters related to TNBC and may provide new tumor biomarkers and help in the development of novel targeted therapies.

MiR-185-3p mimic promotes the chemosensitivity of CRC cells via AQP5

BACKGROUND

Studies showed that microRNAs (miRNAs) are important regulators in drug resistance. The current study investigated the role of miR-185-3p and its predicted target gene AQP5 in 5-FU-insensitive colorectal cancer (CRC) cells.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) and Spearman's correlation analysis were conducted to determine the correlation of expression levels of miR-185-3p and AQP5 from CRC tissues. HCT-116 and HCT-8 cells were treated by gradient concentration of 5-FU to construct 5-FU-resistant CRC model. The inhibition and viability of 5-FU-resistant cells were detected by MTT assay, and cell migration and invasion ability were determined by wound healing and transwell assay. The expressions of miR-185-3p and AQP5 were measured by qRT-PCR. StarBase and dual-luciferase reporter assay were used to predict and confirm the interaction between miR-185-3p and AQP5. Further experiments were performed to explore the function of miR-185-3p in 5-FU-resistant cells through regulating aquaporin-5 (AQP5). The levels of EMT-associated markers and AQP5 were determined by conducting Western Blot and qRT-PCR.

RESULTS

We found that 5-FU-resistant CRC cells showed a lower inhibition rate, and higher migration and invasion abilities. MiR-185-3p was low-expressed in CRC tissues and 5-FU-resistance cells, and it targeted and regulated the expression of AQP5, which was found up-regulated in CRC and 5-FU-resistance CRC cells (r = -0.29, P < .05). Furthermore, miR-185-3p mimic enhanced the chemo-sensitivity of 5-FU-resistant cells, while overexpressed AQP5 reversed such an effect produced by miR-185-3p mimic.

CONCLUSION

MiR-185-3p mimic enhances the chemosensitivity of CRC cells via AQP5. Our research provides a potential therapeutic target for 5-FU-resistant CRC cells.

In silico simulations of erythrocyte aquaporins with quantitative in vitro validation

Modelling water and membrane lipids is an essential element in the computational research of biophysical/biochemical processes such as water transport across the cell membrane. In this study, we examined the accuracies of two popular water models, TIP3P and TIP4P, in the molecular dynamics simulations of erythrocyte aquaporins (AQP1 and AQP3). We modelled the erythrocyte membrane as an asymmetric lipid bilayer with appropriate lipid compositions of its inner and outer leaflet, in comparison with a symmetric lipid bilayer of a single lipid type. We computed the AQP1/3 permeabilities with the transition state theory with full correction for recrossing events. We also conducted cell swelling assays for water transport across the erythrocyte membrane. The experimental results agree with the TIP3P water–erythrocyte membrane model, in confirmation of the expected accuracy of the erythrocyte membrane model, the TIP3P water model, and the CHARMM parameters for water–protein interactions.

Quantitatively predictive study of aquaporins in model erythrocyte membrane validated with cellular experiments.

AQP3 Facilitates Proliferation and Adipogenic Differentiation of Porcine Intramuscular Adipocytes

The meat quality of animal products is closely related to the intramuscular fat content. Aquaglyceroporin (AQP) defines a class of water/glycerol channels that primarily facilitate the passive transport of glycerol and water across biological membranes. In this study, the AQP3 protein of the AQP family was mainly studied in the adipogenic function of intramuscular adipocytes in pigs. Here, we found that AQP3 was increased at both mRNA and protein levels upon adipogenic stimuli in porcine intramuscular adipocytes in vitro. Western blot results showed knockdown of AQP3 by siRNA significantly suppressed the expression of adipogenic genes (PPARγ, aP2, etc.), repressed Akt phosphorylation, as well as reducing lipid accumulation. Furthermore, deletion of AQP3 by siRNA significantly downregulated expression of cell cycle genes (cyclin D, E), and decreased the number of EdU-positive cells as well as cell viability. Collectively, our data indicate that AQP3 is of great importance in both adipogenic differentiation and proliferation in intramuscular adipocytes, providing a potential target for modulating fat infiltration in skeletal muscles.

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.

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.

Single-channel permeability and glycerol affinity of human aquaglyceroporin AQP3

For its fundamental relevance, transport of water and glycerol across the erythrocyte membrane has long been investigated before and after the discovery of aquaporins (AQPs), the membrane proteins responsible for water and glycerol transport. AQP1 is abundantly expressed in the human erythrocyte for maintaining its hydrohomeostasis where AQP3 is also expressed (at a level ~30-folds lower than AQP1) facilitating glycerol transport. This research is focused on two of the remaining questions: How permeable is AQP3 to water? What is the glycerol-AQP3 affinity under near-physiological conditions? Through atomistic modelling and large-scale simulations, we found that AQP3 is two to three times more permeable to water than AQP1 and that the glycerol-AQP3 affinity is approximately 500/M. Using these computed values along with the data from the latest literature on AQP1 and on erythrocyte proteomics, we estimated the water and glycerol transport rates across the membrane of an entire erythrocyte. We used these rates to predict the time courses of erythrocyte swelling-shrinking in response to inward and outward osmotic gradients. Experimentally, we monitored the time course of human erythrocytes when subject to an osmotic or glycerol gradient with light scattering in a stopped-flow spectrometer. We observed close agreement between the experimentally measured and the computationally predicted time courses of erythrocytes, which corroborated our computational conclusions on the AQP3 water-permeability and the glycerol-AQP3 affinity.

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.

Water transport proteins-aquaporins (AQPs) in cancer biology

As highly conserved ubiquitous proteins, aquaporins (AQPs) play an imperative role in the development and progression of cancer. By trafficking water and other small molecules, AQPs play a vital role in preserving the cellular environment. Due to their critical role in cell stability and integrity, it would make sense that AQPs are involved in cancer progression. When AQPs alter the cellular environment, there may be several downstream effects such as alterations in cellular osmolality, volume, ionic composition, and signaling pathways. Changes in the intracellular levels of certain molecules serving as second messengers are synchronized by AQPs. Thus AQPs regulate numerous downstream effector signaling molecules that promote cancer development and progression. In numerous cancer types, AQP expression has shown a correlation with tumor stage and prognosis. Furthermore, AQPs assist in angiogenic and oxidative stress related damaging processes critical for cancer progression. This indicates that AQP proteins may be a viable therapeutic target or biomarker of cancer prognosis.