FXYD5 (dysadherin) may mediate metastatic progression through regulation of the β-Na+-K+-ATPase subunit in the 4T1 mouse breast cancer model

Characterization of macrophages in head and neck squamous cell carcinoma and development of MRG-based risk signature

Macrophages are immune cells in the TME that can not only inhibit angiogenesis, extracellular matrix remodeling, cancer cell proliferation, and metastasis but also mediate the phagocytosis and killing of cancer cells after activation, making them key targets in anti-tumor immunotherapy. However, there is little research on macrophages and their relation to disease prognosis in HNSCC. Initially, we collected scRNA-seq, bulk RNA-seq, and clinical data. Subsequently, we identified macrophages and distinguished MRGs. Using the K-means algorithm, we performed consensus unsupervised clustering. Next, we used ssGSEA analysis to assess immune cell infiltration in MRG clusters. A risk model was established using multivariate Cox analysis. Then, Kaplan-Meier, ROC curves, univariate and multivariate COX analyses, and C-index was used to validate the predictive power of the signature. The TIDE method was applied to assess the response to immunotherapy in patients diagnosed with HNSCC. In addition, drug susceptibility predictions were made for the GDSC database using the calcPhenotype function. We found that 8 MRGs had prognostic potential. Patients in the MRG group A had a higher probability of survival, and MRG clusters A and B had different characteristics. Cluster A had a higher degree of expression and infiltration in MRG, indicating a closer relationship with MRG. The accuracy of the signature was validated using univariate and multivariate Cox analysis, C-index, and nomogram. Immune landscape analysis found that various immune functions were highly expressed in the low-risk group, indicating an improved response to immunotherapy. Finally, drugs with high sensitivity to HNSCC (such as 5-Fluorouracil, Temozolomide, Carmustine, and EPZ5676) were explored and analyze the malignant characteristics of HNSCC. We constructed a prognostic model using multivariate Cox analysis, consisting of 8 MRGs (TGM2, STC1, SH2D3C, PIK3R3, MAP3K8, ITGA5, ARHGAP4, and AQP1). Patients in the low-risk group may have a higher response to immunotherapy. The more prominent drugs for drug selection are 5-fluorouracil, temozolomide and so on. Malignant features associated with HNSCC include angiogenesis, EMT, and the cell cycle. This study has opened up new prospects for the prognosis, prediction, and clinical treatment strategy of HNSCC.

miR-1180 Targets FXYD5 to Regulate Pancreatic Cancer Cells Migration and Invasion

Pancreatic cancer is a fatal malignancy typically diagnosed in older males and has an aggressive progression. The function of the miR-1180/FXYD5 axis in pancreatic cancer malignant behaviors was investigated. 20 pairs of pancreatic cancer and adjacent normal tissue samples were harvested from pancreatic cancer patients, and qRT-PCR, IHC, and western blot assays were performed, respectively, to detect the mRNA expression and protein levels of miR-1180 or FXYD5. Transwell and scratch assays were conducted to detect the migratory and invasive ability of pancreatic cancer cells; a Dual-luciferase reporter assay was employed to validate miR-1180 targeting FXYD5. miR-1180 targeting FXYD5 to regulate the migratory and invasive ability of pancreatic cancer cells was validated in mouse xenograft tumor models. FXYD5 expression was increased in pancreatic cancer tissue samples than in adjacent normal tissue samples (P < 0.01), and FXYD5 expression exhibited a positive correlation with the migratory and invasive ability of pancreatic cancer cells. miR-1180 targeted FXYD5 and negatively regulated FXYD5. Restoring miR-1180 expression could inhibit the migratory and invasive ability of pancreatic cancer cells (P < 0.01), and this effect could potentially be alleviated by FXYD5 overexpression. The miR-1180/FXYD5 axis positively regulated E-cadherin and negatively regulated MMP2 and MMP9 expression levels. In vivo findings demonstrated that miR-1180 overexpression inhibited tumor growth and lung metastasis (P < 0.05), while FXYD5 overexpression promoted tumor growth and lung metastasis (P < 0.05). In conclusion, the miR-1180 /FXYD5 axis could be involved in pancreatic cancer metastasis through the regulation of EMT and extracellular matrix degradation.

Displacement of Native FXYD Protein From Na+/K+-ATPase With Novel FXYD Peptide Derivatives: Effects on Doxorubicin Cytotoxicity

The seven mammalian FXYD proteins associate closely with α/β heterodimers of Na⁺/K⁺-ATPase. Most of them protect the β1 subunit against glutathionylation, an oxidative modification that destabilizes the heterodimer and inhibits Na⁺/K⁺-ATPase activity. A specific cysteine (Cys) residue of FXYD proteins is critical for such protection. One of the FXYD proteins, FXYD3, confers treatment resistance when overexpressed in cancer cells. We developed two FXYD3 peptide derivatives. FXYD3-pep CKCK retained the Cys residue that can undergo glutathionylation and that is critical for protecting the β1 subunit against glutathionylation. FXYD3-pep SKSK had all Cys residues mutated to Serine (Ser). The chemotherapeutic doxorubicin induces oxidative stress, and suppression of FXYD3 with siRNA in pancreatic- and breast cancer cells that strongly express FXYD3 increased doxorubicin-induced cytotoxicity. Exposing cells to FXYD3-pep SKSK decreased co-immunoprecipitation of FXYD3 with the α1 Na⁺/K⁺-ATPase subunit. FXYD3-pep SKSK reproduced the increase in doxorubicin-induced cytotoxicity seen after FXYD3 siRNA transfection in pancreatic- and breast cancer cells that overexpressed FXYD3, while FXYD3-pep CKCK boosted the native protein’s protection against doxorubicin. Neither peptide affected doxorubicin’s cytotoxicity on cells with no or low FXYD3 expression. Fluorescently labeled FXYD3-pep SKSK was detected in a perinuclear distribution in the cells overexpressing FXYD3, and plasmalemmal Na⁺/K⁺-ATPase turnover could not be implicated in the increased sensitivity to doxorubicin that FXYD3-pep SKSK caused. FXYD peptide derivatives allow rapid elimination or amplification of native FXYD protein function. Here, their effects implicate the Cys residue that is critical for countering β1 subunit glutathionylation in the augmentation of cytotoxicity with siRNA-induced downregulation of FXYD3.

Na/K-ATPase: Their role in cell adhesion and migration in cancer

Na/K-ATPase (NKA) is a p-type transmembrane enzyme formed by three different subunits (α, β, and γ gamma). Primarily responsible for transporting sodium and potassium through the cell membrane, it also plays a critical role in intracellular signaling. The activation of diverse intracellular pathways may trigger cell death, survival, or even cell proliferation. Changes in the NKA functions or expression in isoforms subunits impact pathological conditions, such as cancer. The NKA function affects cell adhesion, motility, and migration, which are different in the physiological and pathological states. All enzyme subunits take part in the cell adhesion process, with the β subunit being the most studied. Thus, herein we aim to highlight NKA' central role in cell adhesion, motility, and migration in cancer cells.

FXYD proteins and sodium pump regulatory mechanisms

The sodium/potassium-ATPase (NKA) is the enzyme that establishes gradients of sodium and potassium across the plasma membrane. NKA activity is tightly regulated for different physiological contexts through interactions with single-span transmembrane peptides, the FXYD proteins. This diverse family of regulators has in common a domain containing a Phe-X-Tyr-Asp (FXYD) motif, two conserved glycines, and one serine residue. In humans, there are seven tissue-specific FXYD proteins that differentially modulate NKA kinetics as appropriate for each system, providing dynamic responsiveness to changing physiological conditions. Our understanding of how FXYD proteins contribute to homeostasis has benefitted from recent advances described in this review: biochemical and biophysical studies have provided insight into regulatory mechanisms, genetic models have uncovered remarkable complexity of FXYD function in integrated physiological systems, new posttranslational modifications have been identified, high-resolution structural studies have revealed new details of the regulatory interaction with NKA, and new clinical correlations have been uncovered. In this review, we address the structural determinants of diverse FXYD functions and the special roles of FXYDs in various physiological systems. We also discuss the possible roles of FXYDs in protein trafficking and regulation of non-NKA targets.

Low expression of FXYD5 reverses the cisplatin resistance of epithelial ovarian cancer cells

OBJECTIVE

To investigate the effect of the downregulation of FXYD domain-containing ion transport regulator 5 (FXYD5) on the cisplatin resistance (CisR) of epithelial ovarian cancer (EOC) cells.

METHODS

A2780-CisR and SKOV3-CisR cells were obtained through repeated administrations of different cisplatin concentrations, and the half-maximal inhibition concentration (IC50) was calculated by MTT assays. After transfection with FXYD5 siRNA-1 and FXYD5 siRNA-2, the IC50 values of the A2780-CisR and SKOV3-CisR cells were also detected by the MTT method. Cell proliferation, migration, invasion and apoptosis were evaluated through 5-ethynyl-2'-deoxyuridine (EdU) DNA synthesis, wound healing, Transwell invasion and Annexin-V-FITC/PI dual-staining assays, respectively. qRT-PCR and Western blotting were conducted to detect mRNA and protein expression.

RESULTS

Compared with the sensitive parental cells, the A2780-CisR and SKOV3-CisR cells had increased IC50 and FXYD5 expression. FXYD5 siRNA reduced the IC50 value of cisplatin in the A2780-CisR and SKOV3-CisR cells and decreased the expression of ABCG2 (BCRP) and ABCB1 (MDR1). In addition, FXYD5 inhibition reduced the invasion and migration of the A2780-CisR and SKOV3-CisR cells, with upregulation of E-cadherin and downregulation of Snail and Vimentin. Both FXYD5 siRNA-1 and FXYD5 siRNA-2 inhibited the proliferation and promoted the apoptosis of the A2780-CisR and SKOV3-CisR cells with reduced Ki-67 and increased caspase-3.

CONCLUSION

FXYD5 downregulation may reduce the invasion, migration and EMT formation of EOC cells to increase their sensitivity to cisplatin chemotherapy by inhibiting cell proliferation and promoting cell apoptosis.

FXYD6 overexpression in HBV-related hepatocellular carcinoma with cirrhosis

Objective

The aim of this study was to investigate the expression of FXYD domain-containing ion transport regulator 6 (FXYD6) mRNA and protein in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) tissues with cirrhosis, the corresponding paracancerous tissues and the normal liver tissues, and to explore the clinical significance of FXYD6 expression in HBV-related HCC with cirrhosis.

Methods

The FXYD6 mRNA and protein were examined by semi-quantitative reverse transcription polymerase chain reaction and immunohistochemistry, respectively.

Results

The FXYD6 mRNA in HBV-related HCC tissues was significantly higher than that in the cirrhosis tissues or that in the normal liver tissues. The positive expression rate of FXYD6 protein was statistically higher in HBV-related HCC tissues than that in HBV-related cirrhosis or that in normal liver tissues. There was no significant correlation between the expression of FXYD6 protein and gender, age, histological differentiation, tumor diameter, tumor number, integrity of tumor capsule or not and alpha fetoprotein (AFP) concentration in serum, but the protein expression was associated with microvascular invasion, pathological stage, and early recurrence after operation within 1 year.

Conclusion

FXYD6 might be involved in hepatocyte carcinogenesis and tumor progression in HBV-related HCC with cirrhosis and indicated a poor prognosis.

A FXYD5/TGF‑β/SMAD positive feedback loop drives epithelial‑to‑mesenchymal transition and promotes tumor growth and metastasis in ovarian cancer

Epithelial ovarian cancer is aggressive and lacks effective prognostic indicators or therapeutic targets. In the present study, using immunohistochemistry and bioinformatics analysis on ovarian cancer tissue data from The Obstetrics and Gynecology Hospital of Fudan University and The Cancer Genome Atlas database, it was identified that FXYD domain‑containing ion transport regulator 5 (FXYD5) expression was upregulated in the SKOV3‑IP cell line compared with its parental cell line, SKOV3, and in ovarian cancer tissues compared with in normal tissues. In addition, FXYD5 upregulation was predictive of poor patient survival. Furthermore, through various in vitro (Transwell assay, clonogenic assay and western blot analysis) and in vivo (nude mouse model) experiments, it was demonstrated that FXYD5 promoted the metastasis of ovarian cancer cells. Mechanistically, RNA sequencing, western blot analysis, a luciferase reporter assay and chromatin immunoprecipitation were performed to reveal that FXYD5 dispersed the SMAD7‑SMAD specific E3 ubiquitin protein ligase 2‑TGF‑β receptor 1 (TβR1) complex, deubiquitinated and stabilized TβR1, and subsequently enhanced transforming growth factor‑β (TGF‑β) signaling and sustained TGF‑β‑driven epithelial‑mesenchymal transition (EMT). The TGF‑β‑activated SMAD3/SMAD4 complex was in turn directly recruited to the FXYD5 promoter region, interacted with specific SMAD‑binding elements, and then promoted FXYD5 transcription. In brief, FXYD5 positively regulated TGF‑β/SMADs signaling activities, which in turn induced FXYD5 expression, creating a positive feedback loop to drive EMT in the process of ovarian cancer progression. Collectively, the findings of the present study suggested a mechanism through which FXYD5 serves a critical role in the constitutive activation of the TGF‑β/SMADs signaling pathways in ovarian cancer, and provided a promising therapeutic target for human ovarian cancer.

A Model for the Homotypic Interaction between Na+,K+-ATPase β1 Subunits Reveals the Role of Extracellular Residues 221-229 in Its Ig-Like Domain

The Na⁺, K⁺-ATPase transports Na⁺ and K⁺ across the membrane of all animal cells. In addition to its ion transporting function, the Na⁺, K⁺-ATPase acts as a homotypic epithelial cell adhesion molecule via its β₁ subunit. The extracellular region of the Na⁺, K⁺-ATPase β₁ subunit includes a single globular immunoglobulin-like domain. We performed Molecular Dynamics simulations of the ectodomain of the β₁ subunit and a refined protein-protein docking prediction. Our results show that the β₁ subunit Ig-like domain maintains an independent structure and dimerizes in an antiparallel fashion. Analysis of the putative interface identified segment Lys221-Tyr229. We generated triple mutations on YFP-β₁ subunit fusion proteins to assess the contribution of these residues. CHO fibroblasts transfected with mutant β₁ subunits showed a significantly decreased cell-cell adhesion. Association of β₁ subunits in vitro was also reduced, as determined by pull-down assays. Altogether, we conclude that two Na⁺, K⁺-ATPase molecules recognize each other by a large interface spanning residues 221–229 and 198–207 on their β₁ subunits.

FXYD5 (Dysadherin) upregulation predicts shorter survival and reveals platinum resistance in high-grade serous ovarian cancer patients

BACKGROUND

High-grade serous ovarian carcinoma (HGSOC) is generally associated with a very dismal prognosis. Nevertheless, patients with similar clinicopathological characteristics can have markedly different clinical outcomes. Our aim was the identification of novel molecular determinants influencing survival.

METHODS

Gene expression profiles of extreme HGSOC survivors (training set) were obtained by microarray. Differentially expressed genes (DEGs) and enriched signalling pathways were determined. A prognostic signature was generated and validated on curatedOvarianData database through a meta-analysis approach. The best prognostic biomarker from the signature was confirmed by RT-qPCR and by immunohistochemistry on an independent validation set. Cox regression model was chosen for survival analysis.

RESULTS

Eighty DEGs and the extracellular matrix-receptor (ECM-receptor) interaction pathway were associated to extreme survival. A 10-gene prognostic signature able to correctly classify patients with 98% of accuracy was identified. By an 'in-silico' meta-analysis, overexpression of FXYD domain-containing ion transport regulator 5 (FXYD5), also known as dysadherin, was confirmed in HGSOC short-term survivors compared to long-term ones. Its prognostic and predictive power was then successfully validated, both at mRNA and protein level, first on training than on validation sample set.

CONCLUSION

We demonstrated the possible involvement of FXYD5 and ECM-receptor interaction signal pathway in HCSOC survival and prognosis.