Aquaporin 3 Expression Loss in Urothelial Carcinoma: Association with Tumor Invasion Depth, but not with Grading?

Effect of Arsenate and p-Phenylenediamine on the Expression of Aquaporins in Cultured Human Urothelial Cells

BACKGROUND

Exposure to arsenic (As) or p‑phenylenediamine (PPD) can lead to dysfunction, or even cancer, in various types of organs, including the urinary bladder, yet the underlying mechanisms remain unclear. Aquaporins (AQPs) are widely expressed small water channel proteins that provide the major route for the transport of water and other small molecules across plasma membranes in diverse cell types. Altered expression of AQPs has been associated with pathologies in all major organs, including the urinary bladder.

OBJECTIVE

The present in vitro study was performed as a first step towards exploring the possible involvement of AQPs in As- and PPD‑induced bladder diseases.

METHODS

An immortalized normal human urothelial cell line was employed. Cells were exposed to different concentrations of sodium arsenate (0‑20 μM) or PPD (0‑200 μM) for 48 h. Cell viability was subsequently assessed. The mRNA and protein expression levels of AQPs (specifically, AQP3, 4, 7, 9, and 11) were analyzed using reverse transcription‑quantitative polymerase chain reaction and Western blot analyses, respectively.

RESULTS

The viability of the cells was decreased in a concentration-dependent manner upon exposure to arsenate. The mRNA and protein expression levels of AQP3, 4, 7, and 9 were substantially reduced, whereas the expression of AQP11 was largely unchanged. As for the experiments with PPD, treatment with increasing concentrations of PPD induced a gradual decrease in cell viability. The mRNA and protein expression levels of AQP3, 4, and 11 were generally unaltered; however, a marked reduction in the expression levels of AQP7 was observed, contrasting with a gradual concentration-dependent decrease in the expression of AQP9.

CONCLUSION

The importance of the differential expression profiles of the AQPs induced by arsenate and PPD requires further investigation; nevertheless, the findings of the present study suggest that AQPs have a role in As‑ and PPD‑induced bladder diseases.

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.

Prognostic Role of mRNA-Expression of Aquaporins (AQP) 3, 4, 7 and 9 in Stage pT1 Non-Muscle-Invasive Bladder Cancer

BACKGROUND

AQP proteins show a variety of functions in human cell metabolism. The role of different AQP subtypes in tumor metabolism and prognosis are subject of ongoing research.

OBJECTIVE

To investigate the mRNA expression of Aquaporin (AQP) 3, 4, 7 and 9 in pT1 non-muscle-invasive bladder cancer (NMIBC) and its prognostic value in therapeutic decision making.

METHODS

Formalin-fixed-paraffin-embedded (FFPE) tissues from transurethral resection of the bladder (TURB) from 112 patients with initial diagnosis of stage pT1 NMIBC were analyzed retrospectively together with clinical data and therapeutic approaches. mRNA expression of AQP3, 4, 7 and 9 was measured and quantified using RT-qPCR.

RESULTS

Of the 112 patients (83.9%male, median age 72 years), 40 had a recurrence (35.7%), 16 a progression (14.3%) and 14 patients (12.5%) died tumor-related. mRNA expression for AQP3 was detected in 99.1%, AQP4 in 46.4%, AQP7 in 86.6%and AQP9 in 97.3%. Spearman analysis revealed statistically significant correlations between AQP3, AQP7 and AQP9 mRNA expression with adverse clinical and histopathological parameters (WHO1973 grade 3, concomitant Cis or multifocality). High AQP9 mRNA expression was associated with worse PFS in the total cohort (p = 0.034) and in Grade 3 tumors (p = 0.003) in Kaplan-Meier analysis. In patients with bladder sparing approach, high AQP3 mRNA expression was significantly associated with worse CSS in patients receiving BCG therapy (p = 0.029).

CONCLUSIONS

mRNA expression of AQP3, 7 and 9 correlates with adverse clinical and pathological parameters. AQP3 and 9 may help to identify a subgroup of highest risk patients who may be considered for early cystectomy.

Assessing the Expression of Aquaporin 3 Antigen-Recognition Sites in Oral Squamous Cell Carcinoma

Aquaporin 3 (AQP3) serves as a water and glycerol transporter facilitating epithelial cell hydration. Recently, the involvement of AQP3 in cancers has been reported. However, the immunohistochemical expression of AQP3 in carcinomas remains controversial. We hypothesized that differences in aquaporin 3 antigen recognition (AQP3 AR) may influence their expressions. Thus, our study aimed to assess the immunostaining patterns of 3 AQP3 AR sites in oral squamous cell carcinoma (OSCC) and to compare the adjacent areas of high-grade epithelial dysplasia (HG-ED) and normal oral mucosa (NOM). The study group included formalin-fixed OSCC samples (n=51) with adjacent regions of HG-ED (n=12) and NOM (n=51). The tissues were stained with anti-AQP3 antibodies (AR sites at amino acid (AA) 250-C terminus, AA180-228, and N terminus AA1-80) by immunohistochemistry. Our results showed that strong membranous immunostaining was observed for AQP3 AR sites at the AA250-C terminus and AA180-228 in all the samples for NOM and weak AQP3 immunostaining for both the AR sites in all the 12 samples for HG-ED. The invasive front of OSCC samples showed that AQP3 AR at the AA250-C terminus decreased in 42/51 samples (82.4%) and AA180-228 in 47/51 samples (92.2%). Conversely, in the AQP3 AR site at N terminus AA1-80, all samples of the NOM showed negative or slightly positive staining in the cytoplasm of the lower layers. AQP3 expression was increased in 12/12 cases (100%) and 46/51 cases (90.2%) in the HG-ED and invasive front of OSCC, respectively. AQP3 may be used as a biomarker for detecting malignant transformations. AQP3 AR site differences influence their immunohistochemical expression in OSCC.

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.

Aquaporin 1, 3, and 5 Patterns in Salivary Gland Mucoepidermoid Carcinoma: Expression in Surgical Specimens and an In Vitro Pilot Study

Salivary gland aquaporins (AQPs) are essential for the control of saliva production and maintenance of glandular structure. However, little is known of their role in salivary gland neoplasia. Salivary gland tumors comprise a heterogeneous group of lesions, featuring variable histological characteristics and diverse clinical behaviors. Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. The aim of this study was to evaluate the expression of AQP1, AQP3, and AQP5 in 24 MEC samples by immunohistochemistry. AQP1 expression was observed in vascular endothelium throughout the tumor stroma. AQP3 was expressed in epidermoid and mucosal cells and AQP5 was expressed in mucosal cells of MEC. These proteins were expressed in the human MEC cell line UH-HMC-3A. Cellular ultrastructural aspects were analyzed by electron microscopy to certificate the tumor cell phenotype. In summary, our results show that, despite the fact that these molecules are important for salivary gland physiology, they may not play a distinct role in tumorigenesis in MEC. Additionally, the in vitro model may offer new possibilities to further investigate mechanisms of these molecules in tumor biology and their real significance in prognosis and possible target therapies.