Transcription alterations of members of the ubiquitin-proteasome network in prostate carcinoma

Investigation of the Proteasome 26S Subunit, ATPase Family Genes as Potential Prognostic Biomarkers and Therapeutic Targets for Hepatocellular Carcinoma

Background

Several studies suggest that Proteasome 26S Subunit, ATPase (PSMC) family genes are of great importance in tumor progression and spreading, but the study for systematic evaluation of the function of PSMC genes in hepatocellular carcinoma (HCC) is currently lacking.

Methods

The functions of PSMC genes in HCC were analyzed using multiple online databases, including the TCGA database, GEO database, HPA database, cBioPortal database, DAVID, and KEGG pathway. Experiments were later conducted to verify PSMC expression.

Results

High levels of PSMC gene expression were detected in HCC tissues and PSMCs exhibited potentially powerful abilities in diagnosing HCC patients. All PSMC proteins are expressed to varying degrees in HCC tissues and high expression of the PSMC genes lead to poor prognosis in patients with HCC. Moreover, DNA methylation involves the regulation of the expression of PSMC2 and PSMC5 in HCC, and the levels of methylation of PSMC2 or PSMC5 correlate positively with patient overall survival in HCC patients. The copy number alteration and mutation of PSMC genes were observed and related to the expression of PSMCs in HCC. Functional enrichment analysis showed that many highly co-expressed genes of PSMCs had a potential role in tumor progression and metastasis, which merited further in-depth study. Functional network analysis also suggests that the primary biological function of PSMC genes is the regulation of protein homeostasis and energy metabolism in HCC. Moreover, the expression levels of PSMCs are related to immune cell infiltrates and immunomodulatory factors in HCC.

Conclusion

Our study indicates that PSMC genes are the potential target for precision immunotherapy and novel prognostic biomarkers for HCC.

Quercetin-induced degradation of RhoC suppresses hepatocellular carcinoma invasion and metastasis

BACKGROUND

Tumor metastasis and recurrence are major causes of mortality in patients with hepatocellular carcinoma (HCC) that is still lack of effective therapeutic targets and drugs. Previous reports implied that ras homolog family member C (RhoC) plays a toxic role on metastasis and proliferation of cancer.

METHODS

In this research, the correlation between RhoC and metastasis ability was confirmed by in vitro experiments and TCGA database. We explored whether quercetin could inhibit cell migration or invasion by transwell assay. Real-time PCR, overexpression and ubiquitination assay, etc. were applied in mechanism study. Primary HCC cells and animal models including patient-derived xenografts (PDXs) were employed to evaluate the anti-metastasis effects of quercetin.

RESULTS

Clinical relevance and in vitro experiments further confirmed the level of RhoC was positively correlated with invasion and metastasis ability of HCC. Then we uncovered that quercetin could attenuate invasion and metastasis of HCC by downregulating RhoC's level in vitro, in vivo and PDXs. Furthermore, mechanistic investigations displayed quercetin hindered the E3 ligase expression of SMAD specific E3 ubiquitin protein ligase 2 (SMURF2) leading to enhancement of RhoC's ubiquitination and proteasomal degradation.

CONCLUSIONS

Our research has revealed the novel mechanisms quercetin regulates degradation of RhoC level by targeting SMURF2 and identified quercetin may be a potential compound for HCC therapy.

A novel APA-based prognostic signature may predict the prognosis of lung adenocarcinoma in an East Asian population

The role of alternative polyadenylation (APA) in tumor development is becoming increasingly evident, but the impact of APA events on the prognosis of LUAD patients is unclear. Therefore, in the present study, we aimed to analyze specific APA events in LUAD to identify novel prognostic biomarkers for LUAD. We first identified prognostic candidate genes for LUAD associated with APA events and validated them in both the East Asian and the USA cohorts, finding that five genes (DCUN1D5, PSMC4, TFAM, THRA, and TMEM100) were of prognostic significance in both populations. Based on this, an APA-based prognostic signature was constructed for the East Asian population. The predictive accuracy of the prognostic signature was further evaluated by the time-dependent ROC, with 1-, 2-, and 3-year AUCs of 0.86, 0.81, and 0.71, respectively. This study may provide new markers for individualized diagnosis and prognostic assessment of LUAD and potential targets for precision treatment.

NEDD4L in human tumors: regulatory mechanisms and dual effects on anti-tumor and pro-tumor

Tumorigenesis and tumor development are closely related to the abnormal regulation of ubiquitination. Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L), an E3 ubiquitin ligase critical to the ubiquitination process, plays key roles in the regulation of cancer stem cells, as well as tumor cell functions, including cell proliferation, apoptosis, cell cycle regulation, migration, invasion, epithelial-mesenchymal transition (EMT), and tumor drug resistance, by controlling subsequent protein degradation through ubiquitination. NEDD4L primarily functions as a tumor suppressor in several tumors but also plays an oncogenic role in certain tumors. In this review, we comprehensively summarize the relevant signaling pathways of NEDD4L in tumors, the regulatory mechanisms of its upstream regulatory molecules and downstream substrates, and the resulting functional alterations. Overall, therapeutic strategies targeting NEDD4L to treat cancer may be feasible.

PSMC4 promotes prostate carcinoma progression by regulating the CBX3-EGFR-PI3K-AKT-mTOR pathway

Proteasome 26S subunit ATPase 4 (PSMC4) could regulate cancer progression. However, the function of PSMC4 in prostate carcinoma (PCa) progression requires further clarification. In the study, PSMC4 and chromobox 3 (CBX3) levels were verified by TCGA data and tissue microarrays. Cell counting kit-8, cell apoptosis, cell cycle, wound healing, transwell and xenograft tumour model assays were performed to verify biological functions of PSMC4 in PCa. RNA-seq, PCR, western blotting and co-IP assays were performed to verify the mechanism of PSMC4. Results showed that PSMC4 level was significantly increased in PCa tissues, and patients with PCa with a high PSMC4 level exhibited shorter overall survival. PSMC4 knockdown markedly inhibited cell proliferation, cell cycle and migration in vitro and in vivo, and significantly promoted cell apoptosis. Then further study revealed that CBX3 was a downstream target of PSMC4. PSMC4 knockdown markedly reduced CBX3 level, and inhibited PI3K-AKT-mTOR signalling. CBX3 overexpression markedly promoted epidermal growth factor receptor (EGFR) level. Finally, PSMC4 overexpression showed reverse effect in DU145 cells, and the effects of PSMC4 overexpression on cell proliferation, migration and clonal formation were rescued by the CBX3 knockdown, and regulated EGFR-PI3K-AKT-mTOR signalling. In conclusion, PSMC4 could regulate the PCa progression by mediating the CBX3-EGFR-PI3K-AKT-mTOR pathway. These findings provided a new target for PCa treatment.

The prognostic value of 19S ATPase proteasome subunits in acute myeloid leukemia and other forms of cancer

Introduction

The ubiquitin-proteasome system (UPS) is an intracellular organelle responsible for targeted protein degradation, which represents a standard therapeutic target for many different human malignancies. Bortezomib, a reversible inhibitor of chymotrypsin-like proteasome activity, was first approved by the FDA in 2003 to treat multiple myeloma and is now used to treat a number of different cancers, including relapsed mantle cell lymphoma, diffuse large B-cell lymphoma, colorectal cancer, and thyroid carcinoma. Despite the success, bortezomib and other proteasome inhibitors are subject to severe side effects, and ultimately, drug resistance. We recently reported an oncogenic role for non-ATPase members of the 19S proteasome in chronic myeloid leukemia (CML), acute myeloid leukemia (AML), and several different solid tumors. In the present study, we hypothesized that ATPase members of the 19S proteasome would also serve as biomarkers and putative therapeutic targets in AML and multiple other cancers.

Methods

We used data from The Cancer Genome Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC) available at UALCAN and/or GEPIA2 to assess the expression and prognostic value of proteasome 26S subunit, ATPases 1-6 (PSMC1-6) of the 19S proteasome in cancer. UALCAN was also used to associate PSMC1-6 mRNA expression with distinct clinicopathological features. Finally, cBioPortal was employed to assess genomic alterations of PSMC genes across different cancer types.

Results

The mRNA and protein expression of PSMC1-6 of the 19S proteasome were elevated in several cancers compared with normal controls, which often correlated with worse overall survival. In contrast, AML patients demonstrated reduced expression of these proteasome subunits compared with normal mononuclear cells. However, AML patients with high expression of PSMC2-5 had worse outcomes.

Discussion

Altogether, our data suggest that components of the 19S proteasome could serve as prognostic biomarkers and novel therapeutic targets in AML and several other human malignancies.

The role of NEDD4 related HECT-type E3 ubiquitin ligases in defective autophagy in cancer cells: molecular mechanisms and therapeutic perspectives

The homologous to the E6-AP carboxyl terminus (HECT)-type E3 ubiquitin ligases are the selective executers in the protein ubiquitination, playing a vital role in modulation of the protein function and stability. Evidence shows the regulatory role of HECT-type E3 ligases in various steps of the autophagic process. Autophagy is an intracellular digestive and recycling process that controls the cellular hemostasis. Defective autophagy is involved in tumorigenesis and has been detected in various types of cancer cells. A growing body of findings indicates that HECT-type E3 ligases, in particular members of the neural precursor cell expressed developmentally downregulated protein 4 (NEDD4) including NEDD4-1, NEDD4-L, SMURFs, WWPs, and ITCH, play critical roles in dysregulation or dysfunction of autophagy in cancer cells. The present review focuses on NEDD4 E3 ligases involved in defective autophagy in cancer cells and discusses their autophagic function in different cancer cells as well as substrates and the signaling pathways in which they participate, conferring a basis for the cancer treatment through the modulating of these E3 ligases.

NEDD4L represses prostate cancer cell proliferation via modulating PHF8 through the ubiquitin-proteasome pathway

PURPOSE

Prostate cancer (PC) is a heterogeneous malignancy that greatly threatens man's health. E3 ubiquitin-protein ligase neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) imparts an regulatory role in various malignancies. This study focused on the modulatory mechanism of NEDD4L in proliferation of prostate cancer cells (PCCs) via regulating histone demethylase plant homeodomain finger protein 8 (PHF8/KDM7B) through the ubiquitin-proteasome system.

METHODS

The expression levels of NEDD4L, PHF8, H3 lysine 9 dimethylation (H3K9me2) and activating transcription factor 2 (ATF2) in PC tissues and cell lines were detected via real-time quantitative polymerase chain reaction and Western blotting. After transfection of pcDNA3.1-NEDD4L, pcDNA3.1-PHF8, and pcDNA3.1-ATF2 into PCCs, cell proliferation was assessed via the cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Interaction between NEDD4L and PHF8 was identified via the protein immunoprecipitation. The ubiquitination level of PHF8 was determined via the ubiquitination detection. The enrichments of H3K9me2 and PHF8 in the ATF2 promotor region were detected via the chromatin-immunoprecipitation assay.

RESULTS

PHF8 and ATF2 were highly expressed while NEDD4L was poorly expressed in PC tissues and cells. NEDD4L overexpression reduced proliferation of PCCs. NEDD4Linduced degradation of PHF8 via ubiquitination. PHF8 limited the enrichment of H3K9me2 in the ATF2 promotor region and enhanced ATF2 transcription. Upregulation of PHF8 or ATF2 abolished the inhibitory role of NEDD4L in proliferation of PCCs.

CONCLUSION

NEDD4L facilitated degradation of PHF8 to limit ATF2 transcription, thereby suppressing proliferation of PCCs.

Exploiting the Endogenous Ubiquitin Proteasome System in Targeted Cancer Treatment

To overcome the lack of specificity of cancer therapeutics and thus create a more potent and effective treatment, we developed a novel chimeric protein, IL2-Smurf2. Here, we describe the production of this chimeric IL2-Smurf2 protein and its variants, with inactive or over-active killing components. Using Western blots, we demonstrated the chimeric protein's ability to specifically enter target cells alone. After entering the cells, the protein showed biological activity, causing cell death that was not seen with an inactive variant, and that was shown to be apoptotic. The chimeric protein also proved to be active as an E3 ligase, as demonstrated by testing total ubiquitination levels along with targeted ubiquitination for degradation. Finally, we tested IL2-Smurf2 and its variants in an in vivo mouse model of leukemia and demonstrated its potential as a drug for the targeted treatment of cancer cells. In the course of this work, we established for the first time the feasibility of the use of Smurf2 as a killing component in chimeric targeting proteins. Utilizing the IL2 cytokine to target cells overexpressing IL-2R and Smurf2 to cause protein degradation, we were able to produce a chimeric protein with dual functionality which causes targeted cell death.

The E3 Ligases in Cervical Cancer and Endometrial Cancer

Endometrial (EC) and cervical (CC) cancers are the most prevalent malignancies of the female reproductive system. There is a global trend towards increasing incidence and mortality, with a decreasing age trend. E3 ligases label substrates with ubiquitin to regulate their activity and stability and are involved in various cellular functions. Studies have confirmed abnormal expression or mutations of E3 ligases in EC and CC, indicating their vital roles in the occurrence and progression of EC and CC. This paper provides an overview of the E3 ligases implicated in EC and CC and discusses their underlying mechanism. In addition, this review provides research advances in the target of ubiquitination processes in EC and CC.

Unraveling the Potential Role of NEDD4-like E3 Ligases in Cancer

Cancer is a deadly disease worldwide, with an anticipated 19.3 million new cases and 10.0 million deaths occurring in 2020 according to GLOBOCAN 2020. It is well established that carcinogenesis and cancer development are strongly linked to genetic changes and post-translational modifications (PTMs). An important PTM process, ubiquitination, regulates every aspect of cellular activity, and the crucial enzymes in the ubiquitination process are E3 ubiquitin ligases (E3s) that affect substrate specificity and must therefore be carefully regulated. A surfeit of studies suggests that, among the E3 ubiquitin ligases, neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4)/NEDD4-like E3 ligases show key functions in cellular processes by controlling subsequent protein degradation and substrate ubiquitination. In addition, it was demonstrated that NEDD4 mainly acts as an oncogene in various cancers, but also plays a tumor-suppressive role in some cancers. In this review, to comprehend the proper function of NEDD4 in cancer development, we summarize its function, both its tumor-suppressive and oncogenic role, in multiple types of malignancies. Moreover, we briefly explain the role of NEDD4 in carcinogenesis and progression, including cell survival, cell proliferation, autophagy, cell migration, invasion, metastasis, epithelial-mesenchymal transition (EMT), chemoresistance, and multiple signaling pathways. In addition, we briefly explain the significance of NEDD4 as a possible target for cancer treatment. Therefore, we conclude that targeting NEDD4 as a therapeutic method for treating human tumors could be a practical possibility.

Identifying Potential Mitochondrial Proteome Signatures Associated with the Pathogenesis of Pulmonary Arterial Hypertension in the Rat Model

Pulmonary arterial hypertension (PAH) is a severe and progressive disease that affects the heart and lungs and a global health concern that impacts individuals and society. Studies have reported that some proteins related to mitochondrial metabolic functions could play an essential role in the pathogenesis of PAH, and their specific expression and biological function are still unclear. We successfully constructed a monocrotaline- (MCT-) induced PAH rat model in the present research. Then, the label-free quantification proteomic technique was used to determine mitochondrial proteins between the PAH group (n = 6) and the normal group (n = 6). Besides, we identified 1346 mitochondrial differentially expressed proteins (DEPs) between these two groups. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the mainly mitochondrial DEPs' biological functions and the signal pathways. Based on the protein-protein interaction (PPI) network construction and functional enrichment, we screened 19 upregulated mitochondrial genes (Psmd1, Psmc4, Psmd13, Psmc2, etc.) and 123 downregulated mitochondrial genes (Uqcrfs1, Uqcrc1, Atp5c1, Atp5a1, Uqcrc2, etc.) in rats with PAH. Furthermore, in an independent cohort dataset and experiments with rat lung tissue using qPCR, validation results consistently showed that 6 upregulated mitochondrial genes (Psmd2, Psmc4, Psmc3, Psmc5, Psmd13, and Psmc2) and 3 downregulated mitochondrial genes (Lipe, Cat, and Prkce) were significantly differentially expressed in the lung tissue of PAH rats. Using the RNAInter database, we predict potential miRNA target hub mitochondrial genes at the transcriptome level. We also identified bortezomib and carfilzomib as the potential drugs for treatment in PAH. Finally, this study provides us with a new perspective on critical biomarkers and treatment strategies in PAH.

Comprehensive Analysis of the Glycolysis-Related Gene Prognostic Signature and Immune Infiltration in Endometrial Cancer

Glucose metabolic reprogramming and immune imbalance play important roles in the progression of cancers. The purpose of this study is to develop a glycolysis-related prognostic signature for endometrial cancer (EC) and analyze its relationship with immune function. The mRNA expression profiling of the glycolysis-related genes and clinical data of EC patients were downloaded from The Cancer Genome Atlas (TCGA). We identified a glycolysis-related gene prognostic signature for predicting the prognosis of EC by using The Least Absolute Shrinkage and Selection Operator (LASSO) regression and found the patients in the high-risk group had worse survival prognosis. Multivariate Cox regression analysis showed that the gene signature was an independent prognostic factor for EC. The ROC curve confirmed the accuracy of the prognostic signature (AUC = 0.730). Then, we constructed a nomogram to predict the 1–5 years survival rate of EC patients. The association between the gene signature and immune function was analyzed based on the “ESTIMATE” and “CIBERSORT” algorithm, which showed the immune and ESTIMATE scores of patients in the high-risk group were lower, while the low immune and ESTIMATE scores were associated with a worse prognosis of patients. The imbalance of immune cells was also found in the high-risk group. Further, the protein of CDK1, a gene in the signature, was found to be closely related to prognosis of EC and inhibition of CDK1 could inhibit migration and promote apoptosis of EC cells. This study reveals a link between glycolysis-related gene signature and immunity, and provides personalized therapeutic targets for EC.

Insights Into the Biological Role of NEDD4L E3 Ubiquitin Ligase in Human Cancers

Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is an E3 ubiquitin ligase that has been reported to participate in multiple cellular procedures by regulating of substrate ubiquitination and subsequent protein degradation. A great amount of evidence has demonstrated that NEDD4L mainly functions as a tumor suppressor in most cancer types, while it also acts as an oncogene in a few cancers. In this review, we summarize the potential role of NEDD4L in carcinogenesis and the related underlying molecular mechanism to improve our understanding of its functions in the tumorigenesis of human malignancies. Developing clinical drugs targeting NEDD4L could be a potential therapeutic strategy for cancer therapy in the future.

Novel Insight Into the Association Between Obesity and Hepatocellular Carcinoma Occurrence and Recurrence: High-Throughput Microarray Data Set Analysis of Differentially Expressed Genes

PURPOSE

This study aims to identify potential biomarkers of hepatocellular carcinoma (HCC) occurrence/recurrence and obesity, along with the molecular mechanisms that involve these biomarkers.

METHODS

Three microarray data sets, namely GSE18897, GSE25097, and GSE36376 (genetic suppressor elements associated with obesity, tumor, and recurrence, respectively), were downloaded from Gene Expression Omnibus database to be investigated for their expression as differentially expressed genes (DEGs) in HCC and obesity. The functional and pathway enrichment analysis of these DEGs were identified by the Database for Annotation Visualization and Integrated Discovery. The protein-protein interaction network analysis was performed with STRING online tool and Cytoscape software.

RESULTS

One hundred sixty common DEGs were screened. We found that these genes were associated with certain pathways such as metabolic pathways, terpenoid backbone biosynthesis, and adipocytokine signaling pathway. The involvements of 10 genes, including RPS16, RPS7, CCT3, HNRNPA2B1, EIF4G1, PSMC4, NHP2, EGR1, FDPS, and MCM4, were identified in the subnetwork. HNRNPA2B1 and RPS7 in the GSE18897 data set, RPS16, RPS7, CCT3, HNRNPA2B1, PSMC4, NHP2, FDPS, and MCM4 in the GSE25097 data set, and RPS16, RPS7, CCT3, HNRNPA2B1, EIF4G1, PSMC4, NHP2, FDPS, and MCM4 in the GSE36376 data set exhibited positive fold changes.

CONCLUSION

These DEGs and pathways could be of diagnostic value as potential biomarkers involved in the pathogenesis of HCC, pertaining to both obesity and HCC occurrence/recurrence.

Prognoses and genomic analyses of proteasome 26S subunit, ATPase (PSMC) family genes in clinical breast cancer

Breast cancer is a complex disease, and several processes are involved in its development. Therefore, potential therapeutic targets need to be discovered for these patients. Proteasome 26S subunit, ATPase gene (PSMC) family members are well reported to be involved in protein degradation. However, their roles in breast cancer are still unknown and need to be comprehensively researched. Leveraging publicly available databases, such as cBioPortal and Oncomine, for high-throughput transcriptomic profiling to provide evidence-based targets for breast cancer is a rapid and robust approach. By integrating the aforementioned databases with the Kaplan–Meier plotter database, we investigated potential roles of six PSMC family members in breast cancer at the messenger RNA level and their correlations with patient survival. The present findings showed significantly higher expression profiles of PSMC2, PSMC3, PSMC4, PSMC5, and PSMC6 in breast cancer compared to normal breast tissues. Besides, positive correlations were also revealed between PSMC family genes and ubiquinone metabolism, cell cycle, and cytoskeletal remodeling. Meanwhile, we discovered that high levels of PSMC1, PSMC3, PSMC4, PSMC5, and PSMC6 transcripts were positively correlated with poor survival, which likely shows their importance in breast cancer development. Collectively, PSMC family members have the potential to be novel and essential prognostic biomarkers for breast cancer development.

Identification of an immune gene signature for predicting the prognosis of patients with uterine corpus endometrial carcinoma

Background

Uterine corpus endometrial carcinoma (UCEC) is a frequent gynecological malignancy with a poor prognosis particularly at an advanced stage. Herein, this study aims to construct prognostic markers of UCEC based on immune-related genes to predict the prognosis of UCEC.

Methods

We analyzed expression data of 575 UCEC patients from The Cancer Genome Atlas database and immune genes from the ImmPort database, which were used for generation and validation of the signature. We constructed a transcription factor regulatory network based on Cistrome databases, and also performed functional enrichment and pathway analyses for the differentially expressed immune genes. Moreover, the prognostic value of 410 immune genes was determined using the Cox regression analysis. We then constructed and verified a prognostic signature. Finally, we performed immune infiltration analysis using TIMER-generating immune cell content.

Results

The immune cell microenvironment as well as the PI3K-Akt, and MARK signaling pathways were involved in UCEC development. The established prognostic signature revealed a ten-gene prognostic signature, comprising of PDIA3, LTA, PSMC4, TNF, SBDS, HDGF, HTR3E, NR3C1, PGR, and CBLC. This signature showed a strong prognostic ability in both the training and testing sets and thus can be used as an independent tool to predict the prognosis of UCEC. In addition, levels of B cells and neutrophils were significantly correlated with the patient’s risk score, while the expression of ten genes was associated with immune cell infiltrates.

Conclusions

In summary, the ten-gene prognostic signature may guide the selection of the immunotherapy for UCEC.

A novel risk score system of immune genes associated with prognosis in endometrial cancer

Background

Endometrial cancer was the commonest gynecological malignancy in developed countries. Despite striking advances in multimodality management, however, for patients in advanced stage, targeted therapy still remained a challenge. Our study aimed to investigate new biomarkers for endometrial cancer and establish a novel risk score system of immune genes in endometrial cancer.

Methods

The clinicopathological characteristics and gene expression data were downloaded from The Cancer Genome Atlas (TCGA) database. Differentially expressed genes (DEGs) of immune genes between tumors and normal tissues were identified. Protein–protein interaction (PPI) network of immune genes and transcriptional factors was integrated and visualized in Cytoscape. Univariate and multivariate analysis were employed for key genes to establish a new risk score system. Receiver operating characteristic (ROC) curve and survival analysis were performed to investigate the prognostic value of the model. Association between clinical characteristics and the model was analyzed by logistic regression. For validation, we identified 34 patients with endometrial cancer from Fudan University Shanghai Cancer Center (FUSCC). We detected 14-genes mRNA expression and calculated the risk scores of each patients and we performed survival analysis between the high-risk group and the low-risk group.

Results

23 normal tissues and 552 tumor tissues were obtained from TCGA database. 410 immune-related DEGs was identified by difference analysis and correlation analysis. KEGG and GO analysis revealed these DEGs were enriched in cell adhesion, chemotaxis, MAPK pathways and PI3K-Akt signaling pathway, which might regulate tumor progression and migration. All genes were screened for risk model construction and 14 hub immune-related genes (HTR3E, CBLC, TNF, PSMC4, TRAV30, PDIA3, FGF8, PDGFRA, ESRRA, SBDS, CRHR1, LTA, NR2F1, TNFRSF18) were prognostic in endometrial cancer. The area under the curve (AUC) was 0.787 and the high-risk group estimated by the model possessed worse outcome (P < 0.001). Multivariate analysis suggested that the model was indeed an independent prognostic factor (high-risk vs. low-risk, HR = 1.14, P < 0.001). Meanwhile, the high-risk group was prone to have higher grade (P = 0.002) and advanced clinical stage (P = 0.018). In FUSCC validation set, the high-risk group had worse survival than the low-risk group (P < 0.001).

Conclusions

In conclusion, the novel risk model of immune genes had some merits in predicting the prognosis of endometrial cancer and had strong correlation with clinical outcomes. Furthermore, it might provide new biomarkers for targeted therapy in endometrial cancer.

The functions and regulation of Smurfs in cancers

Smad ubiquitination regulatory factor 1 (Smurf1) and Smurf2 are HECT-type E3 ubiquitin ligases, and both Smurfs were initially identified to regulate Smad protein stability in the TGF-β/BMP signaling pathway. In recent years, Smurfs have exhibited E3 ligase-dependent and -independent activities in various kinds of cells. Smurfs act as either potent tumor promoters or tumor suppressors in different tumors by regulating biological processes, including metastasis, apoptosis, cell cycle, senescence and genomic stability. The regulation of Smurfs activity and expression has therefore emerged as a hot spot in tumor biology research. Further, the Smurf1- or Smurf2-deficient mice provide more in vivo clues for the functional study of Smurfs in tumorigenesis and development. In this review, we summarize these milestone findings and, in turn, reveal new avenues for the prevention and treatment of cancer by regulating Smurfs.

Transcriptional downregulation of miR-127-3p by CTCF promotes prostate cancer bone metastasis by targeting PSMB5

Prostate cancer (PCa) is one of the most common cancers in males and particularly tends to metastasize to bone. Currently, metastatic bone disease is incurable, and new therapies need to be developed. Our study aims to determine the role of miR-127-3p in PCa metastasis to bone. The results demonstrate that miR-127-3p is markedly reduced in bone metastasis-positive PCa tissues relative to that in bone metastasis-negative PCa tissues. Furthermore, overexpressing miR-127-3p inhibits PCa cell invasion and migration in vitro by targeting the proteasome β-subunit PSMB5. Moreover, CCCTC-binding factor (CTCF) transcriptionally inhibits miR-127-3p by interacting with the miR-127-3p promoter. Collectively, this study uncovers a novel mechanism of the CTCF/miR-127-3p/PSMB5 axis in promoting PCa bone metastasis, indicating that miR-127-3p could function as a promising therapeutic target against bone metastasis.

PPARγ induces NEDD4 gene expression to promote autophagy and insulin action

The E3 ubiquitin ligase neural precursor cell-expressed developmentally down-regulated protein 4 (NEDD4) plays a crucial role in governing a number of signaling pathways, including insulin and autophagy signaling. However, the molecular mechanism by which NEDD4 gene is transcriptionally regulated has not been fully elucidated. Here, we reported that NEDD4 mRNA and protein levels were increased by peroxisome proliferator-activated receptor-γ (PPARγ) in HepG2 hepatocytes. PPARγ antagonist GW9662 abolished thiazolidinedione (TZD)-induced NEDD4 expression. ChIP and luciferase reporter assays showed that PPARγ directly bound to the potential PPAR-responsive elements (PPREs) within the promoter region of the human NEDD4 gene. In addition, TZDs increased Akt phosphorylation and glucose uptake, which were abrogated through NEDD4 depletion. Furthermore, we showed that NEDD4-mediated autophagy induction and Akt phosphorylation were suppressed by oleic acid and high glucose treatment, activation of PPARγ successfully prevented this suppression. In conclusion, these results suggest that PPARγ plays a novel role in linking glucose metabolism and protein homeostasis through NEDD4-mediated effects on the autophagy machinery.

E3 ubiquitin ligase Smurf2: a prognostic factor in microsatellite stable colorectal cancer

Purpose

Smurf2 is a member of the homologous to E6-AP carboxyl terminus family of E3 ubiquitin ligases. Changes in their expression pattern are known to contribute to tumorigenesis. Smurf2 plays a decisive role in cell differentiation, proliferation, and migration and exhibits a dual role in cancer – functioning as both oncogene and tumor suppressor. Dysregulation of Smurf2 in different cancer types has been described, besides colorectal cancer (CRC). We therefore examined the expression and oncogenic potential of Smurf2 in human CRC patients.

Materials and methods

Expression levels of Smurf2 were analyzed via qRT-PCR in CRC specimens and healthy mucosa from 98 patients who had undergone surgery due to CRC. Spatial expression of Smurf2 was additionally studied by immunohistochemistry. siRNA-mediated knockdown of Smurf2 was applied for migration and invasion assays in DLD-1 and SW-480 cells.

Results

Smurf2 was significantly overexpressed in CRC tissue compared to corresponding healthy colon mucosa. Smurf2 expression levels differed significantly between microsatellite instable (MSI) and microsatellite stable (MSS) CRC. In patients suffering from MSS CRC, high tumoral expression of Smurf2 was significantly associated with impaired overall survival. Consistently, in vitro analysis revealed that knockdown of Smurf2 reduced the invasive and migratory potential of MSS CRC cells.

Conclusion

Smurf2 expression is upregulated in CRC specimens and affects survival dependent on patients’ MSI status. Moreover, Smurf2 supports cancer cell migration and invasion, collectively suggesting an oncogenic function in CRC.

Neural precursor cell-expressed developmentally down-regulated 4-like: a new biomarker in the pathophysiology of endometrial cancer

Objectives

Endometrial cancer is the most frequent tumor of the female genital tract. Ubiquitin is a small protein (8.5 kDa) found in all eukaryotic cells, binds to substrate proteins via a three-phase enzymatic pathway referred to as ubiquitination and plays an important role in cellular stability. Neural precursor cell-expressed developmentally down-regulated 4-like (NEDD4L) functions in the last phase of this enzymatic process. In this study, we investigated NEDD4L protein expression in endometrial cancer.

Methods

The study participants were divided into patients with benign endometrial pathologies (Group 1, n = 23), patients with endometrial hyperplasia (Group 2, n = 21) and patients with endometrial cancer (Group 3, n = 20). NEDD4L expression was detected by immunohistochemical staining and H scores were calculated to standardize staining intensity. Statistical analysis was performed using SPSS 16.0.

Results

NEDD4L expression levels according to H scores were significantly lower in patients diagnosed with endometrial cancer compared with those with benign endometrial pathologies.

Conclusion

NEDD4L is involved in maintaining cell stability, and reduced NEDD4L expression as a result of gene mutation may disrupt this balance in favor of tumorigenesis.

Downregulation of Nedd4L predicts poor prognosis, promotes tumor growth and inhibits MAPK/ERK signal pathway in hepatocellular carcinoma

Accumulating evidence indicates that the neural precursor cell-expressed, developmentally downregulated 4-like (Nedd4L) related with some tumor progression pathways and was found abnormally expressed in several kinds of solid cancers. However, the role and mechanism of Nedd4L in HCC remain unknown. This study was to assess the role of Nedd4L in HCC tumorigenesis and prognosis. The real-time quantitative RT-PCR and immunohistochemistry results revealed that Nedd4L was downregulated in HCC tissues compared to corresponding peri-noncancerous tissue, and HCC patients with low expression of Nedd4L exhibited poor prognosis assessed by Kaplan-Meier and Cox regression analysis in 78 HCC patients. Furthermore, knockdown of Nedd4L could significantly promote proliferation of HCC cells by CCK-8 and colony formation assays in vitro; whereas ectopic expression of Nedd4L resulted in attenuating proliferation in vitro and tumor growth in vivc determined by nude mice xenografts model. Mechanically, Nedd4L could phosphorylate ERK1/2 and regulate genes related with apoptosis. Collectively, Nedd4L plays a tumor suppressive role in HCC, possibly through triggering MAPK/ERK-mediated apoptosis, and Nedd4L downregulation may be a potential prognostic biomarker as well as a therapeutic target for HCC.

NEDD4L Protein Catalyzes Ubiquitination of PIK3CA Protein and Regulates PI3K-AKT Signaling

Oncogenic PIK3CA (p110α), the catalytic subunit of class IA PI3K, plays a major role in PI3K-related cancer progression. The mechanisms underlying the dynamic regulation of PIK3CA protein levels remain unknown. Here we demonstrated that PIK3CA is regulated by polyubiquitination. We identified NEDD4L as the E3 ligase that catalyzes PIK3CA polyubiquitination, leading to its proteasome-dependent degradation. NEDD4L ubiquitinates both the free and regulatory subunit-bound PIK3CA but does not ubiquitinate the regulatory subunit of PI3K. Overexpression of NEDD4L accelerates the turnover rate of PIK3CA, whereas suppression of NEDD4L results in not only the accumulation of PIK3CA but also a paradoxical decrease of AKT activation. Thus, we propose that NEDD4L negatively regulates PIK3CA protein levels via ubiquitination and is required for the maintenance of PI3K-AKT signaling pathway.

Nedd4L expression is decreased in ovarian epithelial cancer tissues compared to ovarian non-cancer tissue

AIM

Recent studies have demonstrated that the neural precursor cell expressed, developmentally downregulated 4-like (Nedd4L) gene plays a role in the progression of various cancers. However, reports describing Nedd4L expression in ovarian cancer tissues are limited.

MATERIAL AND METHODS

A cohort (n = 117) of archival formalin-fixed, paraffin embedded resected normal ovarian epithelial tissues (n = 10), benign ovarian epithelial tumor tissues (n = 10), serous borderline ovarian epithelial tumor tissues (n = 14), mucous borderline ovarian epithelial tumor tissues (n = 11), and invasive ovarian epithelial cancer tissues (n = 72) were assessed for Nedd4L protein expression using immunohistochemistry.

RESULTS

Nedd4L protein expression was significantly decreased in invasive ovarian epithelial cancer tissues compared to non-cancer tissues (P < 0.05). Decreased Nedd4L protein expression correlated with clinical stage, pathological grade, lymph node metastasis and survival (P < 0.05).

CONCLUSION

Nedd4L protein expression may be an independent prognostic marker of ovarian cancer development.

NEDD4-2 (NEDD4L): the ubiquitin ligase for multiple membrane proteins

NEDD4-2 (also known as NEDD4L, neural precursor cell expressed developmentally down-regulated 4-like) is a ubiquitin protein ligase of the Nedd4 family which is known to bind and regulate a number of membrane proteins to aid in their internalization and turnover. Several of the NEDD4-2 substrates include ion channels, such as the epithelial and voltage-gated sodium channels. Given the critical function of NEDD4-2 in regulating membrane proteins, this ligase is essential for the maintenance of cellular homeostasis. In this article we review the biology and function of this important ubiquitin-protein ligase and discuss its pathophysiological significance.

Regulation of ERBB3/HER3 signaling in cancer

ERBB3/HER3 is emerging as a molecular target for various cancers. HER3 is overexpressed and activated in a number of cancer types under the conditions of acquired resistance to other HER family therapeutic interventions such as tyrosine kinase inhibitors and antibody therapies. Regulation of the HER3 expression and signaling involves numerous HER3 interacting proteins. These proteins include PI3K, Shc, and E3 ubiquitin ligases NEDD4 and Nrdp1. Furthermore, recent identification of a number of HER3 oncogenic mutations in colon and gastric cancers elucidate the role of HER3 in cancer development. Despite the strong evidence regarding the role of HER3 in cancer, the current understanding of the regulation of HER3 expression and activation requires additional research. Moreover, the lack of biomarkers for HER3-driven cancer poses a big challenge for the clinical development of HER3 targeting antibodies. Therefore, a better understanding of HER3 regulation should improve the strategies to therapeutically target HER3 for cancer therapy.

Bortezomib prevents oncogenesis and bone metastasis of prostate cancer by inhibiting WWP1, Smurf1 and Smurf2

Prostate cancer is the most common malignancy diagnosed in males, and bone metastases remain a significant source of morbidity and mortality in this population. Ubiquitin ligase E3s and proteasomes were thought to play essential roles in the development of cancers, therefore, they were proposed as therapy targets for the treatment of solid and hematological malignancies. Bortezomib, well-known as a proteasome inhibitor, has been observed with exact anticancer effect both in cell and animal models for several solid tumor types, including prostate cancer. To explore activities of the ubiquitin ligase E3s WWP1, Smurf1 and Smurf2 in oncogenesis and bone metastasis of prostate cancer, as well as in the functional mechanism of bortezomib in preventing prostate cancer, transcription and expression levels of WWP1, Smurf1 and Smurf2 genes in cell lines or tissues of benign prostate hyperplasia and human prostate cancer with and without bone metastasis were tested. Moreover, human prostate cancer PC3 cell lines were treated with bortezomib at different concentration gradients and then their proliferation at different time points, mRNA and protein levels were investigated. The results indicated that transcription and expression levels of WWP1, Smurf1 and Smurf2 genes in prostate cancer without bone metastasis were significantly higher compared to those in benign prostate hyperplasia (P<0.05), whereas significantly lower than prostate cancer metastatic to bone (P<0.05). Furthermore, bortezomib reduced the transcription and expression levels of WWP1, Smurf1 and Smurf2 genes in prostate cancer cell lines in a dose-dependent manner, thus, inhibiting the proliferation of prostate cancer cells. Elevated transcription and expression levels of ubiquitin ligase E3s WWP1, Smurf1 and Smurf2 genes may be the mechanisms of occurrence, development and metastasis of prostate cancer. In addition, bortezomib can prevent prostate cancer and its bone metastasis by downregulating WWP1, Smurf1 and Smurf2.

Downregulation of Smurf2, a tumor-suppressive ubiquitin ligase, in triple-negative breast cancers: involvement of the RB-microRNA axis

Background

The HECT family ubiquitin ligase Smurf2 regulates cell polarity, migration, division, differentiation and death, by targeting diverse substrates that are critical for receptor signaling, cytoskeleton, chromatin remodeling and transcription. Recent studies suggest that Smurf2 functions as a tumor suppressor in mice. However, no inactivating mutation of SMURF2 has been reported in human, and information about Smurf2 expression in human cancer remains limited or complicated. Here we demonstrate that Smurf2 expression is downregulated in human breast cancer tissues, especially of the triple-negative subtype, and address the mechanism of Smurf2 downregulation in triple-negative breast cancer cells.

Methods

Human breast cancer tissues (47 samples expressing estrogen receptor (ER) and 43 samples with triple-negative status) were examined by immunohistochemistry for the expression of Smurf2. Ten widely-studied human breast cancer cell lines were examined for the expression of Smurf2. Furthermore, microRNA-mediated regulation of Smurf2 was investigated in triple-negative cancer cell lines.

Results

Immunohistochemical analysis showed that benign mammary epithelial cells expressed high levels of Smurf2, so did cells in ductal carcinomas in situ. In contrast, invasive ductal carcinomas showed focal or diffuse decrease in Smurf2 expression, which was observed more frequently in triple-negative tumors than in ER-positive tumors. Consistently, human triple-negative breast cancer cell lines such as BT549, MDA-MB-436, DU-4475 and MDA-MB-468 cells showed significantly lower expression of Smurf2 protein, compared to ER + or HER2+ cell lines. Studies using quantitative PCR and specific microRNA inhibitors indicated that increased expression of miR-15a, miR-15b, miR-16 and miR-128 was involved in Smurf2 downregulation in those triple-negative cancer cell lines, which have mutations in the retinoblastoma (RB) gene. Forced expression of RB increased levels of Smurf2 protein with concomitant decreases in the expression of the microRNAs.

Conclusions

This study provides evidence of posttranscriptional downregulation of Smurf2 in triple-negative breast cancers, and demonstrates that the loss of RB function is involved in microRNA-mediated interference with Smurf2 translation. The new link from RB inactivation to Smurf2 downregulation is likely to play a role in malignant phenotypes of triple-negative breast cancer cells.

NEDD4L is downregulated in colorectal cancer and inhibits canonical WNT signaling

The NEDD4 family of E3 ubiquitin ligases includes nine members. Each is a modular protein, containing an N-terminal C2 domain for cell localization, two-to-four central WW domains for substrate recognition, and a C-terminal, catalytic HECT domain, which is responsible for catalyzing the ubiquitylation reaction. Members of this family are known to affect pathways central to the pathogenesis of colorectal cancer, including the WNT, TGFβ, EGFR, and p53 pathways. Recently, NEDD4 mRNA was reported to be overexpressed in colorectal cancer, but tumor stage was not considered in the analysis. Expression of the other family members has not been studied in colorectal cancer. Herein, we determined the expression patterns of all nine NEDD4 family members in 256 patients who presented with disease ranging from premalignant adenoma to stage IV colorectal cancer. NEDD4 mRNA was significantly increased in all stages of colorectal cancer. In contrast, NEDD4L mRNA, the closest homolog to NEDD4, was the most highly downregulated family member, and was significantly downregulated in all tumor stages. We also found NEDD4L protein was significantly decreased by western blotting in colorectal cancer samples compared to adjacent normal mucosa. In addition, NEDD4L, but not catalytically inactive NEDD4L, inhibited canonical WNT signaling at or below the level of β-catenin in vitro. These findings suggest that NEDD4L may play a tumor suppressive role in colorectal cancer, possibly through inhibition of canonical WNT signaling.

Pathobiological properties of the ubiquitin ligase Nedd4L in melanoma

A recent global gene expression profiling study unexpectedly showed that activated oncogenic NRAS may recruit neural precursor cell expressed, developmentally downregulated 4L (Nedd4L; a human homologue of Nedd4-2) in cultured melanoma cells. However, whether Nedd4L was expressed in melanoma tissues or participated in melanoma carcinogenesis remains to be clarified. Here, we investigated the expression status of Nedd4L in human melanocytes, benign nevi and melanoma tissue specimens and subsequently attempted to determine the role of Nedd4L in melanoma cell growth. Immunohistochemical staining revealed that Nedd4L was not present in any non-tumorous melanocytes or in 18 benign nevi tissues, but it was detected in 34 of 79 cutaneous melanomas and 9 of 32 nodal metastatic melanomas. Downregulation of Nedd4L significantly reduced the growth of cultured G361 melanoma cells in vitro. Moreover, exogenous Nedd4L expression significantly promoted the growth of A2058 melanoma cells in vivo in a xenograft assay. The present findings indicate that Nedd4L expression may be increased to facilitate tumour growth in many melanomas.

Identification of the NEDD4L gene as a prognostic marker by integrated microarray analysis of copy number and gene expression profiling in non-small cell lung cancer

PURPOSE

The purpose of this study was to identify prognostic genes by integrated microarray analysis between comparative genomic hybridization and gene expression with laser microdissection in non-small cell lung cancer (NSCLC).

METHODS

Integrated microarray analysis in 11 lung adenocarcinomas was performed, and several genes were identified. Among them, neural precursor cell-expressed developmentally down-regulated 4-like (NEDD4L) was chosen for further characterization. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to explore the clinicopathological significance of NEDD4L expression in 84 NSCLC patients.

RESULTS

18q was more frequently lost in advanced lung cancer. Therefore, we selected the NEDD4L gene, located on chromosome 18q, for which reduced expression was significantly correlated with copy number loss. NEDD4L mRNA expression in paired tumor/normal samples from 79 cases of lung cancer was evaluated using real-time PCR analysis. NEDD4L mRNA expression was significantly lower in tumor tissues than in normal lung tissues (p < 0.0001). Clinicopathological factors, such as excessive smoking history, histological grade (moderately and poorly), T stage (T2-4), lymph node metastasis, and pathological stage (stage II-IV), were significantly associated with low NEDD4L expression (p < 0.05). In the low expression group, prognoses were significantly poorer than in the high expression group (p < 0.05).

CONCLUSIONS

Low NEDD4L expression may be a marker of prognosis. This is the first report to describe NEDD4L expression in NSCLC. NEDD4L may be considered a key gene in the progression of NSCLC, and its expression is likely affected by genomic alterations.

Key role for ubiquitin protein modification in TGFβ signal transduction

The transforming growth factor β (TGFβ) superfamily of signal transduction molecules plays crucial roles in the regulation of cell behavior. TGFβ regulates gene transcription through Smad proteins and signals via non-Smad pathways. The TGFβ pathway is strictly regulated, and perturbations lead to tumorigenesis. Several pathway components are known to be targeted for proteasomal degradation via ubiquitination by E3 ligases. Smurfs are well known negative regulators of TGFβ, which function as E3 ligases recruited by adaptors such as I-Smads. TGFβ signaling can also be enhanced by E3 ligases, such as Arkadia, that target repressors for degradation. It is becoming clear that E3 ligases often target multiple pathways, thereby acting as mediators of signaling cross-talk. Regulation via ubiquitination involves a complex network of E3 ligases, adaptor proteins, and deubiquitinating enzymes (DUBs), the last-mentioned acting by removing ubiquitin from its targets. Interestingly, also non-degradative ubiquitin modifications are known to play important roles in TGFβ signaling. Ubiquitin modifications thus play a key role in TGFβ signal transduction, and in this review we provide an overview of known players, focusing on recent advances.

Nkx3.1 and Myc crossregulate shared target genes in mouse and human prostate tumorigenesis

Cooperativity between oncogenic mutations is recognized as a fundamental feature of malignant transformation, and it may be mediated by synergistic regulation of the expression of pro- and antitumorigenic target genes. However, the mechanisms by which oncogenes and tumor suppressors coregulate downstream targets and pathways remain largely unknown. Here, we used ChIP coupled to massively parallel sequencing (ChIP-seq) and gene expression profiling in mouse prostates to identify direct targets of the tumor suppressor Nkx3.1. Further analysis indicated that a substantial fraction of Nkx3.1 target genes are also direct targets of the oncoprotein Myc. We also showed that Nkx3.1 and Myc bound to and crossregulated shared target genes in mouse and human prostate epithelial cells and that Nkx3.1 could oppose the transcriptional activity of Myc. Furthermore, loss of Nkx3.1 cooperated with concurrent overexpression of Myc to promote prostate cancer in transgenic mice. In human prostate cancer patients, dysregulation of shared NKX3.1/MYC target genes was associated with disease relapse. Our results indicate that NKX3.1 and MYC coregulate prostate tumorigenesis by converging on, and crossregulating, a common set of target genes. We propose that coregulation of target gene expression by oncogenic/tumor suppressor transcription factors may represent a general mechanism underlying the cooperativity of oncogenic mutations during tumorigenesis.

Inflammatory macrophages induce Nrf2 transcription factor-dependent proteasome activity in colonic NCM460 cells and thereby confer anti-apoptotic protection

Adaptation of epithelial cells to persistent oxidative stress plays an important role in inflammation-associated carcinogenesis. This adaptation process involves activation of Nrf2 (nuclear factor-E2-related factor-2), which has been recently shown to contribute to carcinogenesis through the induction of proteasomal gene expression and proteasome activity. To verify this possible link between inflammation, oxidative stress, and Nrf2-dependent proteasome activation, we explored the impact of inflammatory (M1) macrophages on the human colon epithelial cell line NCM460. Transwell cocultures with macrophages differentiated from granulocyte monocyte-colony-stimulating factor-treated monocytes led to an increased activity of Nrf2 in NCM460 cells along with an elevated proteasome activity. This higher proteasome activity resulted from Nrf2-dependent induction of proteasomal gene expression, as shown for the 19 and 20 S subunit proteins S5a and α5, respectively. These effects of macrophage coculture were preceded by an increase of reactive oxygen species in cocultured NCM460 cells and could be blocked by catalase or by the reactive oxygen species scavenger Tiron, whereas transient treatment of NCM460 cells with H(2)O(2) similarly led to Nrf2-dependent proteasome activation. Through the Nrf2-dependent increase of proteasomal gene expression and proteasome activity, the sensitivity of NCM460 cells to tumor necrosis factor-related apoptosis-inducing ligand- or irinotecan-induced apoptosis declined. These findings indicate that inflammatory conditions such as the presence of M1 macrophages and the resulting oxidative stress are involved in the Nrf2-dependent gain of proteasome activity in epithelial cells, e.g. colonocytes, giving rise of greater resistance to apoptosis. This mechanism might contribute to inflammation-associated carcinogenesis, e.g. of the colon.

Decreased expression of Nedd4L correlates with poor prognosis in gastric cancer patient

The neural precursor cell expressed, developmentally down-regulated 4-like (Nedd4L) gene encodes an ubiquitin ligase that targets the epithelial sodium channel for degradation. Recent studies have demonstrated that Nedd4L plays a role in the progression of various cancers. However, the clinical implications of Nedd4L expression status in gastric cancer have remained unclear. We examined the Nedd4L expression in 82 gastric cancer patients by immunohistochemistry. The correlation between Nedd4L expression and clinicopathological factors, including prognosis, was evaluated. Cancerous Nedd4L expression was detectable in 36 of the 82 tumors (43.9%). Tumors with negative Nedd4L expression had greater extent of lymph node metastasis, lymphatic invasion, and venous invasion, and were at a worse stage than the tumors with positive Nedd4L expression. Additionally, the patients with negative Nedd4L expression had poor clinical outcomes. Furthermore, multivariate analysis indicated that Nedd4L expression was an independent prognostic factor for gastric cancer patients. Our results suggest for the first time that negative Nedd4L expression is strongly related to the invasion and metastasis of gastric cancer. Therefore, Nedd4L expression can be used as an independent prognostic marker of gastric cancer.