Deubiquitinating enzyme USP33/VDU1 is required for Slit signaling in inhibiting breast cancer cell migration

USP33 is an integrin α6 deubiquitinase and promotes esophageal squamous cell carcinoma cell migration and metastasis

PURPOSE

The deubiquitinating enzymes (DUBs) have been linked to cancer initiation and progression. Although ubiquitin-specific protease 33 (USP33) represents a significant factor in regulating various tumor cell behaviors, its specific biological functions and precise mechanisms in esophageal squamous cell carcinoma (ESCC) progression remain unclear.

METHODS

The expressions of USP33 mRNA in GEO databases, clinical ESCC samples, and USP33 protein were analyzed using bioinformatics, RT-PCR, and immunohistochemistry, respectively. Using Kaplan-Meier survival curves, the log-rank test was used to determine the cumulative survival rate. Western blotting was used to determine indicated protein expression. The cell biological functions were evaluated by cell growth assay, transwell, cell adhesion, and cell spreading assay, respectively. The interaction between USP33 and integrins was detected by immunoprecipitation, and the deubiquitination was performed by deubiquitination assay. The metastatic ability was checked by tail vein injection.

RESULTS

A significant positive correlation was found between USP33 expression and clinical TNM stage, T classification, and poor prognosis in patients with ESCC. USP33 promoted laminin-dependent adhesion, spreading, and migration of ESCC cells but not their proliferation. Mechanistically, USP33 mediates cell migration through binding, deubiquinating, and stabilizing integrin α6. USP33 knockdown could inhibit ESCC cell migration and metastasis majorly through integrin α6.

CONCLUSION

This study reveals a novel mechanism of USP33 in promoting laminin-dependent ESCC cell migration and metastasis through integrin α6, suggesting that USP33 may be a promising target for treating ESCC.

Lung-Targeted Lipid Nanoparticle-Delivered siUSP33 Attenuates SARS-CoV-2 Replication and Virulence by Promoting Envelope Degradation

As a structural protein of SARS-CoV-2, the envelope (E) protein not only plays a key role in the formation of viral particles, but also forms ion channels and has pathogenic functions, including triggering cell death and inflammatory responses. The stability of E proteins is controlled by the host ubiquitin-proteasome system. By screening human deubiquitinases, it is found that ubiquitin-specific protease 33 (USP33) can enhance the stability of E proteins depending on its deubiquitinase activity, thereby promoting viral replication. In the absence of USP33, E proteins are rapidly degraded, leading to a reduced viral load and inflammation. Using lipid nanoparticle (LNP) encapsulation of siUSP33 by adjusting the lipid components (ionizable cationic lipids), siUSP33 is successfully delivered to mouse lung tissues, rapidly reducing USP33 expression in the lungs and maintaining knockdown for at least 14 days, effectively suppressing viral replication and virulence. This method of delivery allows efficient targeting of the lungs and a response to acute infections without long-term USP33 deficiency. This research, based on the deubiquitination mechanism of USP33 on the E protein, demonstrates that LNP-mediated siRNA delivery targeting USP33 plays a role in antiviral and anti-inflammatory responses, offering a novel strategy for the prevention and treatment of SARS-CoV-2.

Emerging roles of deubiquitinating enzymes in actin cytoskeleton and tumor metastasis

BACKGROUND

Metastasis accounts for the majority of cancer-related deaths. Actin dynamics and actin-based cell migration and invasion are important factors in cancer metastasis. Metastasis is characterized by actin polymerization and depolymerization, which are precisely regulated by molecular changes involving a plethora of actin regulators, including actin-binding proteins (ABPs) and signalling pathways, that enable cancer cell dissemination from the primary tumour. Research on deubiquitinating enzymes (DUBs) has revealed their vital roles in actin dynamics and actin-based migration and invasion during cancer metastasis.

CONCLUSION

Here, we review how DUBs drive tumour metastasis by participating in actin rearrangement and actin-based migration and invasion. We summarize the well-characterized and essential actin cytoskeleton signalling molecules related to DUBs, including Rho GTPases, Src kinases, and ABPs such as cofilin and cortactin. Other DUBs that modulate actin-based migration signalling pathways are also discussed. Finally, we discuss and address therapeutic opportunities and ongoing challenges related to DUBs with respect to actin dynamics.

The mechanism of USP43 in the development of tumor: a literature review

Ubiquitination of the proteins is crucial for governing protein degradation and regulating fundamental cellular processes. Deubiquitinases (DUBs) have emerged as significant regulators of multiple pathways associated with cancer and other diseases, owing to their capacity to remove ubiquitin from target substrates and modulate signaling. Consequently, they represent potential therapeutic targets for cancer and other life-threatening conditions. USP43 belongs to the DUBs family involved in cancer development and progression. This review aims to provide a comprehensive overview of the existing scientific evidence implicating USP43 in cancer development. Additionally, it will investigate potential small-molecule inhibitors that target DUBs that may have the capability to function as anti-cancer medicines.

miR-206 alleviates LPS-induced inflammatory injury in cardiomyocytes via directly targeting USP33 to inhibit the JAK2/STAT3 signaling pathway

Previous reports have confirmed that miR-206 participates in inflammatory cardiomyopathy, but its definite mechanism remains elusive. This study aims to elucidate the potential mechanism of miR-206 in septic cardiomyopathy (SCM). The primary mouse cardiomyocytes were isolated and exposed to lipopolysaccharides (LPS) to construct a septic injury model in vitro. Then, the gene transcripts and protein levels were detected by RT-qPCR and/or Western blot assay. Cell proliferation, apoptosis, and inflammatory responses were evaluated by CCK-8/EdU, flow cytometry, and ELISA assays, respectively. Dual luciferase assay, Co-IP, and ubiquitination experiments were carried out to validate the molecular interactions among miR-206, USP33, and JAK2/STAT3 signaling. miR-206 was significantly downregulated, but USP33 was upregulated in LPS-induced cardiomyocytes. Gain-of-function of miR-206 elevated the proliferation but suppressed the inflammatory responses and apoptosis in LPS-induced cardiomyocytes. USP33, as a member of the USP protein family, was confirmed to be a direct target of miR-206 and could catalyze deubiquitination of JAK2 to activate JAK2/STAT3 signaling. Rescue experiments presented that neither upregulation of USP33 nor JAK2/STAT3 signaling activation considerably reversed the protective effects of miR-206 upregulation in LPS-induced cardiomyocytes. The above data showed that miR-206 protected cardiomyocytes from LPS-induced inflammatory injuries by targeting the USP33/JAK2/STAT3 signaling pathway, which might be a novel target for SCM treatment.

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Downregulation of USP33 inhibits Slit/Robo signaling pathway and is associated with poor patient survival of glioma

BACKGROUND

Gliomas are the most common malignant tumors in the central nervous system originating from brain glial cells. Although characterized as highly invasive and highly malignant, few molecular targeting therapies have been developed. Ubiquitin Specific Protease 33 (USP33), a gene encoding a deubiquinating enzyme important in a variety of processes, including Slit-dependent cell migration and beta-2 adrenergic receptor signaling, participates in the development of several malignant tumors, however, its role in the development of glioma has not been evaluated.

METHODS

Real-time quantitative PCR was performed to examine the expression of USP33 in glioma tissues and cell lines. Immunohistochemistry was performed to determine USP33 expressions in glioma tissue microarray. Transwell assay was performed to analyze the effect of USP33 on glioma cell line migration. The Kaplan-Meier method and log rank test were applied to evaluate the prognostic value of USP33 expression. Univariate and multivariate Cox proportional hazard regression models were used to identify the independent prognostic factors associated with overall survival (OS) or disease-free survival.

RESULTS

The present study demonstrated that USP33 expression was significantly downregulated in glioma tissues. Lower expression of USP33 was associated with a poorer patient disease-free survival and overall survival. In vitro studies revealed that overexpression of USP33 significantly inhibited the migration ability of glioma cells. Mechanistically, USP33 inhibits glioma cell migration by regulating the function of Slit/Robo signaling pathway.

CONCLUSIONS

Downregulation of USP33 is associated with poor patient survival of glioma. USP33 inhibits glioma cell migration by Slit/Robo signaling pathway. This mechanism may be applied for development of targeting therapy especially for the high-grade glioma.

USPs in Pancreatic Ductal Adenocarcinoma: A Comprehensive Bioinformatic Analysis of Expression, Prognostic Significance, and Immune Infiltration

Pancreatic ductal adenocarcinoma (PDAC), as an intractable malignancy, still causes an extremely high mortality worldwide. The ubiquitin-specific protease (USP) family constitutes the major part of deubiquitinating enzymes (DUBs) which has been reported to be involved in initiation and progression of various malignancies via the function of deubiquitination. However, the biological function and clinical values of USPs in PDAC have not been comprehensively elucidated. In this study, Gene Expression Profiling Interactive Analysis (GEPIA), Gene Expression Omnibus (GEO) datasets, UALCAN database, and the Human Protein Atlas (HPA) online tool were used to analyze the expression level and the relationship between USP expression and clinicopathological features in PDAC. Survival module of HPA and Kaplan-Meier plotter (KMP) databases was recruited to explore the prognostic value of USPs. Tumor Immune Estimation Resource (TIMER) online tool and KMP databases were utilized to elucidate tumor immune infiltration and immune-related survival of USPs. CBioPortal online tool was used to identify the gene mutation level of USPs in PDAC. Both cBioPortal and LinkedOmics were used to confirm the potential biological functions of USPs in PDAC. Our study showed that USP10, USP14, USP18, USP32, USP33, and USP39 (termed as six-USPs) expressions were significantly elevated in tumor tissues. The high expression of the four USPs (USP10, USP14, USP18, and USP39) indicated a poor prognosis. A significant relationship was indicated between the expression of six-USPs and clinicopathological features. Also, the expression of six-USPs was related to promoter methylation level. Moreover, more than 40% genetic alterations and mutations were discovered in six-USPs. Furthermore, the six-USP expression was correlated with immune infiltration and immune-related prognosis. The functional analysis found that the six-USPs were involved in various biological processes and signaling pathways, such as nucleocytoplasmic transport, choline metabolism in cancer, cell cycle, ErbB signaling pathway, RIG-I-like receptor signaling pathway, TGF-β signaling pathway, and TNF signaling pathway. In conclusion, the results showed that six-USPs are potential prognostic biomarkers and can be recruited as possible therapeutic targets of PDAC.

Emerging potential of ubiquitin-specific proteases and ubiquitin-specific proteases inhibitors in breast cancer treatment

Breast cancer is the most frequently diagnosed cancer in women, accounting for 30% of new diagnosing female cancers. Emerging evidence suggests that ubiquitin and ubiquitination played a role in a number of breast cancer etiology and progression processes. As the primary deubiquitinases in the family, ubiquitin-specific peptidases (USPs) are thought to represent potential therapeutic targets. The role of ubiquitin and ubiquitination in breast cancer, as well as the classification and involvement of USPs are discussed in this review, such as USP1, USP4, USP7, USP9X, USP14, USP18, USP20, USP22, USP25, USP37, and USP39. The reported USPs inhibitors investigated in breast cancer were also summarized, along with the signaling pathways involved in the investigation and its study phase. Despite no USP inhibitor has yet been approved for clinical use, the biological efficacy indicated their potential in breast cancer treatment. With the improvements in phenotypic discovery, we will know more about USPs and USPs inhibitors, developing more potent and selective clinical candidates for breast cancer.

Identifying Hub Genes Associated with Neoadjuvant Chemotherapy Resistance in Breast Cancer and Potential Drug Repurposing for the Development of Precision Medicine

Breast cancer is the second leading cause of morbidity and mortality in women worldwide. Despite advancements in the clinical application of neoadjuvant chemotherapy (NAC), drug resistance remains a major concern hindering treatment efficacy. Thus, identifying the key genes involved in driving NAC resistance and targeting them with known potential FDA-approved drugs could be applied to advance the precision medicine strategy. With this aim, we performed an integrative bioinformatics study to identify the key genes associated with NAC resistance in breast cancer and then performed the drug repurposing to identify the potential drugs which could use in combination with NAC to overcome drug resistance. In this study, we used publicly available RNA-seq datasets from the samples of breast cancer patients sensitive and resistant to chemotherapy and identified a total of 1446 differentially expressed genes in NAC-resistant breast cancer patients. Next, we performed gene co-expression network analysis to identify significantly co-expressed gene modules, followed by MCC (Multiple Correlation Clustering) clustering algorithms and identified 33 key hub genes associated with NAC resistance. mRNA–miRNA network analysis highlighted the potential impact of these hub genes in altering the regulatory network in NAC-resistance breast cancer cells. Further, several hub genes were found to be significantly involved in the poor overall survival of breast cancer patients. Finally, we identified FDA-approved drugs which could be useful for potential drug repurposing against those hub genes. Altogether, our findings provide new insight into the molecular mechanisms of NAC resistance and pave the way for drug repurposing techniques and personalized treatment to overcome NAC resistance in breast cancer.

Aberrant Methylation of SLIT2 Gene in Plasma Cell-Free DNA of Non-Small Cell Lung Cancer Patients

Simple Summary

Despite significant advances in the detection, prevention, and treatment of lung cancer, the prognosis of the patients is still very poor due in part to micrometastasis of cancer cells to surrounding tissues at the time of diagnosis. Therefore, identifying biomarkers for early detection of lung cancer is very important for prolonging the lifespan of patients with lung cancer. The methylation statuses of SLIT1, SLIT2, SLIT3 genes were analyzed in bronchial washing, bronchial biopsy, sputum, tumor and matched normal tissues, or plasma samples obtained from a total of 208 non-small cell lung cancer (NSCLC) patients and 121 cancer-free patients to understand the feasibility of the genes as biomarkers for early detection and survival prediction of NSCLC. The present study suggests that aberrant methylation of SLIT2 in plasma cell-free DNA might be a potential biomarker for the early detection and prognosis prediction of NSCLC patient.

Abstract

This study aimed to understand aberrant methylation of SLITs genes as a biomarker for the early detection and prognosis prediction of non-small cell lung cancer (NSCLC). Methylation levels of SLITs were determined using the Infinium HumanMethylation450 BeadChip or pyrosequencing. Five CpGs at the CpG island of SLIT1, SLIT2 or SLIT3 genes were significantly (Bonferroni corrected p < 0.05) hypermethylated in tumor tissues obtained from 42 NSCLC patients than in matched normal tissues. Methylation levels of these CpGs did not differ significantly between bronchial washings obtained from 76 NSCLC patients and 60 cancer-free patients. However, methylation levels of SLIT2 gene were significantly higher in plasma cell-free DNA of 72 NSCLC patients than in that of 61 cancer-free patients (p = 0.001, Wilcoxon rank sum test). Prediction of NSCLC using SLIT2 methylation was achieved with a sensitivity of 73.7% and a specificity of 61.9% in a plasma test dataset (N = 40). A Cox proportional hazards model showed that SLIT2 hypermethylation in plasma cell-free DNA was significantly associated with poor recurrence-free survival (hazards ratio = 2.19, 95% confidence interval = 1.21–4.36, p = 0.01). The present study suggests that aberrant methylation of SLIT2 in plasma cell-free DNA is a valuable biomarker for the early detection of NSCLC and prediction of recurrence-free survival. However, further research is needed with larger sample size to confirm results.

High salt activates p97 to reduce host antiviral immunity by restricting Viperin induction

High-salt diets have recently been implicated in hypertension, cardiovascular disease, and autoimmune disease. However, whether and how dietary salt affects host antiviral response remain elusive. Here, we report that high salt induces an instant reduction in host antiviral immunity, although this effect is compromised during a long-term high-salt diet. Further studies reveal that high salt stimulates the acetylation at Lys663 of p97, which promotes the recruitment of ubiquitinated proteins for proteasome-dependent degradation. p97-mediated degradation of the deubiquitinase USP33 results in a deficiency of Viperin protein expression during viral infection, which substantially attenuates host antiviral ability. Importantly, switching to a low-salt diet during viral infection significantly enhances Viperin expression and improves host antiviral ability. These findings uncover dietary salt-induced regulation of ubiquitinated cellular proteins and host antiviral immunity, and could offer insight into the daily consumption of salt-containing diets during virus epidemics.

Discovery of Cancer-Specific and Independent Prognostic Gene Subsets of the Slit-Robo Family Using TCGA-PANCAN Datasets

The Slit-Robo family of axon guidance molecules works in concert, playing important roles in organ development and cancer. Expressions of individual Slit-Robo genes have been used in calculating univariable hazard ratios (HR_uni) for predicting cancer prognosis in the literature. However, Slit-Robo members do not act independently; hence, hazard ratios from multivariable Cox regression (HR_multi) on the whole gene set can further lead to identification of cancer-specific, novel, and independent prognostic gene pairs or modules. Herein, we obtained mRNA expressions of the Slit-Robo family consisting of four Robos (ROBO1/2/3/4) and three Slits (SLIT1/2/3), along with four types of survival outcome across cancers found in the Cancer Genome Atlas (TCGA). We used cluster heat maps to visualize closely associated pairs/modules of prognostic genes across 33 different cancers. We found a smaller number of significant genes in HR_multi than in HR_uni, suggesting that the former analysis was less redundant. High ROBO4 expression emerged as relatively protective within the family, in both types of HR analyses. Multivariable Cox regression, on the other hand, revealed significantly more HR signatures containing Slit-Robo pairs acting in opposing directions than those containing Slit-Slit or Robo-Robo pairs for disease-specific survival. Furthermore, we discovered, through the online app SmulTCan's lasso regression, Slit-Robo gene subsets that significantly differentiated between high- versus low-risk prognosis patient groups, particularly for renal cancers and low-grade glioma. The statistical pipeline reported herein can help test independent and significant pairs/modules within a codependent gene family for cancer prognostication, and thus should also prove useful in personalized/precision medicine research.

Ubiquitin specific peptidase 33 promotes cell proliferation and reduces apoptosis through regulation of the SP1/PI3K/AKT pathway in retinoblastoma

Ubiquitin-specific protease 33 (USP33), a deubiquitinating enzyme (DUB), has been identified to serve as a tumor suppressor or an oncogene in different cancers. However, its role in retinoblastoma (RB) remains unknown. Here, we aimed to uncover USP33 expression profile and function in RB, and disclose the underlying mechanism. USP33 levels in RB tissues and cells were determined using RT-qPCR and western blotting assays. USP33 effects on cell growth, cycle, apoptosis and tumorigenesis were studied using MTT, Edu, cycle and western blotting and in vivo assays. The results showed that USP33 expression levels were elevated in RB tissues and cells as compared with normal retinal tissues and cells. Downregulation of USP33 in RB Y79 and WERI-RB1 cells leaded to significant increases in cell apoptosis, G1 phase arrest and tumorigenesis, and reductions in cell growth and G2 and S phase arrest, as well as inhibited the activation of the PI3K/AKT signaling. SP1 overexpression abolished the roles of USP33 downregulation in modulating the activation of PI3K/AKT signaling, cell growth, apoptosis, and cell cycle. This study uncovered that USP33 promoted the progression of RB through regulation of the SP1/PI3K/AKT pathway.

Circular RNA circ_0057558 Controls Prostate Cancer Cell Proliferation Through Regulating miR-206/USP33/c-Myc Axis

We previously reported the elevated expression of circ_0057558 in prostate cancer tissues and cell lines. Here, we aimed to determine the biological function of circ_0057558 in prostate cancer. In the current study, circ_0057558 knockdown in prostate cancer cells significantly repressed cell proliferation and colony formation, but promoted cell arrest and enhanced the sensitivity to docetaxel. Bioinformatics analysis prediction and RNA-pull down assay identified miR-206 as the potential binding miRNA of circ_0057558. A negative correlation was observed between the expression of miR-206 and circ_0057558 in prostate cancer tissues. miR-206 mimics rescued the function of circ_0057558 overexpression on prostate cancer cells. Further, the bioinformatics analysis and luciferase assay suggested that miR-206 may target ubiquitin-specific peptidase 33 (USP33). USP33 mRNA expression has negative correlation with miR-206 expression and positive correlation with circ_0057558 expression in prostate cancer tissues. USP33 overexpression partially blocked the effects of miR-206 mimics on prostate cell proliferation. USP33 could bind and deubiquitinate c-Myc. Increased c-Myc protein by circ_0057558 overexpression was partially reversed by miR-206 mimics. The proliferation inhibition activity of MYC inhibitor 361 (MYCi361) was more prominent in primary prostate cancer cells and patient-derived xenograft (PDX) model with higher level of circ_0057558. Collectively, circ_0057558 gives an impetus to cell proliferation and cell cycle control in prostate cancer cell lines by sponging miR-206 and positively regulating the transcription of the miR-206 target gene USP33.

The WD40-Repeat Protein WDR-20 and the Deubiquitinating Enzyme USP-46 Promote Cell Surface Levels of Glutamate Receptors

Reversible modification of AMPA receptors (AMPARs) with ubiquitin regulates receptor levels at synapses and controls synaptic strength. The conserved deubiquitinating enzyme (DUB) ubiquitin-specific protease-46 (USP-46) removes ubiquitin from AMPARs and protects them from degradation in both Caenorhabditis elegans and mammals. Although DUBs are critical for diverse physiological processes, the mechanisms that regulate DUBs, especially in the nervous system, are not well understood. We and others previously showed that the WD40-repeat proteins WDR-48 and WDR-20 bind to and stimulate the catalytic activity of USP-46. Here, we identify an activity-dependent mechanism that regulates WDR-20 expression and show that WDR-20 works together with USP-46 and WDR-48 to promote surface levels of the C. elegans AMPAR GLR-1. usp-46, wdr-48, and wdr-20 loss-of-function mutants exhibit reduced levels of GLR-1 at the neuronal surface and corresponding defects in GLR-1-mediated behavior. Increased expression of WDR-20, but not WDR-48, is sufficient to increase GLR-1 surface levels in an usp-46-dependent manner. Loss of usp-46, wdr-48, and wdr-20 function reduces the rate of local GLR-1 insertion in neurites, whereas overexpression of wdr-20 is sufficient to increase the rate of GLR-1 insertion. Genetic manipulations that chronically reduce or increase glutamate signaling result in reciprocal alterations in wdr-20 transcription and homeostatic compensatory changes in surface GLR-1 levels that are dependent on wdr-20 This study identifies wdr-20 as a novel activity-regulated gene that couples chronic changes in synaptic activity with increased local insertion and surface levels of GLR-1 via the DUB USP-46.SIGNIFICANCE STATEMENT Deubiquitinating enzymes (DUBs) are critical regulators of synapse development and function; however, the regulatory mechanisms that control their various physiological functions are not well understood. This study identifies a novel role for the DUB ubiquitin-specific protease-46 (USP-46) and its associated regulatory protein WD40-repeat protein-20 (WDR-20) in regulating local insertion of glutamate receptors into the neuronal cell surface. This work also identifies WDR-20 as an activity-regulated gene that couples chronic changes in synaptic activity with homeostatic compensatory increases in surface levels of GLR-1 via USP-46. Given that 35% of USP family DUBs associate with WDR proteins, understanding the mechanisms by which WDR proteins regulate USP-46 could have implications for a large number of DUBs in other cell types.

What deubiquitinating enzymes, oncogenes, and tumor suppressors actually do: Are current assumptions supported by patient outcomes?

Context can determine whether a given gene acts as an oncogene or a tumor suppressor. Deubiquitinating enzymes (DUBs) regulate the stability of many components of the pathways dictating cell fate so it would be expected that alterations in the levels or activity of these enzymes may have oncogenic or tumor suppressive consequences. In the current review we survey publications reporting that genes encoding DUBs are oncogenes or tumor suppressors. For many DUBs both claims have been made. For such "double agents," the effects of gain or loss of function will depend on the overall status of a complex of molecular signaling networks subject to extensive crosstalk. As the TGF-β paradox makes clear context is critical in cell fate decisions, and the disconnect between experimental findings and patient survival outcomes can in part be attributed to disparities between culture conditions and the microenvironment in vivo. Convincing claims for oncogene or tumor suppressor roles require the documentation of gene alterations in patient samples; survival curves are alone inadequate.

USP43 directly regulates ZEB1 protein, mediating proliferation and metastasis of colorectal cancer

Colorectal cancer is one of the most common malignant tumors of the digestive tract. In this study, we had examined the biological role of USP43 in colorectal cancer. USP43 protein and mRNA abundance in clinical tissues and five cell lines were analyzed with quantitative real-time PCR test (qRT-PCR) and western blot. USP43 overexpression treated DLD1 cells and USP43 knockdown treated SW480 cells were used to study cell proliferation, migration, colony formation, invasion, and the expression of epithelial-mesenchymal transformation (EMT) biomarkers. Moreover, ubiquitination related ZEB1 degradation was studied with qRT-PCR and western blot. The relationships between USP43 and ZEB1 were investigated with western blot, co-immunoprecipitation, migration, and invasion. USP43 was highly expressed in colorectal cancer tissues. USP43 overexpression and knockdown treatments could affect cell proliferation, colony formation, migration, invasion, and the expression of EMT associated biomarkers. Moreover, USP43 can regulate ZEB1 degradation through ubiquitination pathway. USP43 could promote the proliferation, migration, and invasion of colorectal cancer. Meanwhile, USP43 can deubiquitinate and stabilize the ZEB1 protein, which plays an important role in the function of colorectal cancer.

Structural insights and evaluation of the potential impact of missense variants on the interactions of SLIT2 with ROBO1/4 in cancer progression

The cognate interaction of ROBO1/4 with its ligand SLIT2 is known to be involved in lung cancer progression. However, the precise role of genetic variants, disrupting the molecular interactions is less understood. All cancer-associated missense variants of ROBO1/4 and SLIT2 from COSMIC were screened for their pathogenicity. Homology modelling was done in Modeller 9.17, followed by molecular simulation in GROMACS. Rigid docking was performed for the cognate partners in PatchDock with refinement in HADDOCK server. Post-docking alterations in conformational, stoichiometric, as well as structural parameters, were assessed. The disruptive variants were ranked using a weighted scoring scheme. In silico prioritisation of 825 variants revealed 379 to be potentially pathogenic out of which, about 12% of the variants, i.e. ROBO1 (14), ROBO4 (8), and SLIT2 (23) altered the cognate docking. Six variants of ROBO1 and 5 variants of ROBO4 were identified as "high disruptors" of interactions with SLIT2 wild type. Likewise, 17 and 13 variants of SLIT2 were found to be "high disruptors" of its interaction with ROBO1 and ROBO4, respectively. Our study is the first report on the impact of cancer-associated missense variants on ROBO1/4 and SLIT2 interactions that might be the drivers of lung cancer progression.

PRRG4 promotes breast cancer metastasis through the recruitment of NEDD4 and downregulation of Robo1

Metastasis is responsible for the death of most breast cancer patients. Robo1 has been implicated as a tumor suppressor for various cancers including breast cancer. However, it is not well understood how Robo1 expression is regulated during tumorigenesis. In this study, we uncovered that the transmembrane proline rich γ-carboxyglutamic acid protein 4 (PRRG4) promotes breast cancer metastasis by downregulating Robo1. Analysis of mRNA expression data in The Cancer Genome Atlas and immunohistochemistry assay on breast tumor samples showed that PRRG4 expression was higher in breast tumors than in normal breast tissues. Experiments with PRRG4 knockdown and overexpression revealed that PRRG4 promoted migration and invasion of breast cancer cells, and enhanced metastasis in an experimental metastasis model. Mechanistically, we found that PRRG4 via its LPSY and PPPY motifs recruited the E3 ubiquitin ligase NEDD4, which induced ubiquitination and degradation of Robo1, thus contributing to migration and invasion of breast cancer cells. In addition, PRRG4 interacted with and enhanced protein tyrosine kinase Src and FAK activation. Overall, our data support a model that PRRG4 via NEDD4 downregulates the Robo1, resulting in the activation of Src and FAK and promoting breast cancer metastasis. PRRG4 may be a novel target for treating metastatic breast cancer.

USP33 regulates c-Met expression by deubiquitinating SP1 to facilitate metastasis in hepatocellular carcinoma

AIMS

Deubiquitinase ubiquitin-specific protease 33 (USP33) is abnormally expressed in various tumors and participates in tumor progression. However, the expression and biological role of USP33 in hepatocellular carcinoma (HCC) are still unclear.

MAIN METHODS

We performed immunohistochemistry, western blotting, and qRT-PCR analysis to determine the expression of USP33 in HCC. We then analyzed the effects of USP33 expression on the prognosis of HCC. The roles of USP33 in regulating HCC cell migration and invasion were further explored in vitro. Animal studies were performed to investigate the effects of USP33 on tumor metastasis. RNA sequencing and luciferase reporter and immunofluorescence assays were used to identify the activation of the specificity protein 1 (SP1)/c-Met axis.

KEY FINDINGS

Here, for the first time, we reported an abnormal increase in the expression of USP33 in HCC tissues and that USP33 may act as a prognostic biomarker for HCC patients. We found that USP33 knockdown inhibited the invasion and metastasis in HCC cells both in vitro and in vivo, which was partly dependent on c-Met. Further investigations revealed that USP33 regulated c-Met expression by enhancing the protein stability of the transcription factor SP1 in HCC cells. Mechanistically, USP33 directly bound SP1 and decreased its ubiquitination, thereby upregulating c-Met expression.

SIGNIFICANCE

Our results reveal that USP33 acts as the deubiquitinating enzyme of SP1 and contributes to HCC invasion and metastasis through activation of the SP1/c-Met axis. These data indicate a previously unknown function of USP33, which may provide potential targets for the treatment of HCC patients.

Transcriptional characterization of conjunctival melanoma identifies the cellular tumor microenvironment and prognostic gene signatures

This study characterizes the transcriptome and the cellular tumor microenvironment (TME) of conjunctival melanoma (CM) and identifies prognostically relevant biomarkers. 12 formalin-fixed and paraffin-embedded CM were analyzed by MACE RNA sequencing, including six cases each with good or poor clinical outcome, the latter being defined by local recurrence and/or systemic metastases. Eight healthy conjunctival specimens served as controls. The TME of CM, as determined by bioinformatic cell type enrichment analysis, was characterized by the enrichment of melanocytes, pericytes and especially various immune cell types, such as plasmacytoid dendritic cells, natural killer T cells, B cells and mast cells. Differentially expressed genes between CM and control were mainly involved in inhibition of apoptosis, proteolysis and response to growth factors. POU3F3, BIRC5 and 7 were among the top expressed genes associated with inhibition of apoptosis. 20 genes, among them CENPK, INHA, USP33, CASP3, SNORA73B, AAR2, SNRNP48 and GPN1, were identified as prognostically relevant factors reaching high classification accuracy (area under the curve: 1.0). The present study provides new insights into the TME and the transcriptional profile of CM and additionally identifies new prognostic biomarkers. These results add new diagnostic tools and may lead to new options of targeted therapy for CM.

A Genetic Analysis of Tumor Progression in Drosophila Identifies the Cohesin Complex as a Suppressor of Individual and Collective Cell Invasion

Metastasis is the leading cause of death for patients with cancer. Consequently it is imperative that we improve our understanding of the molecular mechanisms that underlie progression of tumor growth toward malignancy. Advances in genome characterization technologies have been very successful in identifying commonly mutated or misregulated genes in a variety of human cancers. However, the difficulty in evaluating whether these candidates drive tumor progression remains a major challenge. Using the genetic amenability of Drosophila melanogaster we generated tumors with specific genotypes in the living animal and carried out a detailed systematic loss-of-function analysis to identify conserved genes that enhance or suppress epithelial tumor progression. This enabled the discovery of functional cooperative regulators of invasion and the establishment of a network of conserved invasion suppressors. This includes constituents of the cohesin complex, whose loss of function either promotes individual or collective cell invasion, depending on the severity of effect on cohesin complex function.

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Screen identifies genes that affect tumor behavior in a wide variety of ways

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A functionally validated network of invasion-suppressor genes was generated

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Loss of cohesin complex function can promote individual or collective cell invasion

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The fly pupal notum is an excellent in vivo system to study tumor progression

Engagement of Robo1 by Slit2 induces formation of a trimeric complex consisting of Src-Robo1-E-cadherin for E-cadherin phosphorylation and epithelial-mesenchymal transition

Loss of E-cadherin elicits epithelial-mesenchymal transition (EMT). While both the Src family of membrane-associated non-receptor tyrosine kinases (SFKs) and Slit2 binding to Roundabout 1 (Robo1) have been shown to induce E-cadherin repression and EMT, whether these two signaling pathways are mechanistically coupled remains unknown in epithelial cells. Here we found that Slit2 and Robo1 overexpression activated Src kinases for tyrosine phosphorylation, degradation of E-cadherin and induction of EMT. Specific blockade of Slit2 binding to Robo1 inactivated Src, prevented E-cadherin phosphorylation and EMT induction. Biochemically, the cytoplasmic CC3 motif of Robo1 (CC3) bound directly to the SH2 and 3 domains of c-Src and the cytoplasmic domains of E-cadherin. Slit2 induced Robo1 association with endogenous c-Src and E-cadherin, whereas ectopic expression of CC3 dissociated this protein complex in colorectal epithelial cells. These results indicate that Slit2 not only induces Robo1 binding to Src, but also recruits Src to E-cadherin for tyrosine phosphorylation of E-cadherin, leading to E-cadherin degradation and EMT induction in colorectal epithelial cells.

Deubiquitinating enzyme USP33 restrains docetaxel-induced apoptosis via stabilising the phosphatase DUSP1 in prostate cancer

The treatment of castration-resistant prostate cancer (CRPC) still faces many challenges. Docetaxel is a chemotherapeutic drug commonly used in CRPC patients. However, docetaxel-based chemotherapy usually causes docetaxel resistance, partially due to the resistance of CRPC cells to docetaxel-induced apoptosis. Here, we report that the deubiquitinating enzyme ubiquitin-specific protease 33 (USP33) inhibits docetaxel-induced apoptosis of prostate cancer cells, including androgen-independent prostate cancer cells. USP33 is overexpressed in prostate cancer cells and tissues. We found that knockdown or knockout of USP33 enhanced docetaxel-induced apoptosis of prostate cancer cells, accompanied by increased phosphorylation of the cJUN NH2-terminal kinase (JNK). After blocking docetaxel-induced JNK activation using the JNK inhibitor SP600125 or siRNA targeting JNK, the USP33 knockout-enhanced apoptosis was reversed. Furthermore, we found that USP33 could interact with the phosphatase DUSP1 to negatively regulate the activation of JNK, while USP33 knockdown promoted the proteasomal degradation of DUSP1. Mechanistically, we found that USP33 could inhibit the Lys48 (K48)-linked polyubiquitination of DUSP1. More importantly, DUSP1 overexpression could reverse the USP33 knockdown-induced JNK activation and apoptosis in docetaxel-treated prostate cancer cells. Therefore, USP33 overexpression in prostate cancer may contribute to docetaxel resistance by inhibiting the degradation of its partner DUSP1, leading to impaired JNK activation and apoptosis. Our study suggests that USP33-DUSP1-JNK may be a key signalling module mediating the docetaxel resistance of CRPC, indicating that USP33 is a potential novel therapeutic target in CRPC.

Targeting the SLIT/ROBO pathway in tumor progression: molecular mechanisms and therapeutic perspectives

The SLITs (SLIT1, SLIT2, and SLIT3) are a family of secreted proteins that mediate positional interactions between cells and their environment during development by signaling through ROBO receptors (ROBO1, ROBO2, ROBO3, and ROBO4). The SLIT/ROBO signaling pathway has been shown to participate in axonal repulsion, axon guidance, and neuronal migration in the nervous system and the formation of the vascular system. However, the role of the SLIT/ROBO pathway has not been thoroughly clarified in tumor development. The SLIT/ROBO pathway can produce both beneficial and detrimental effects in the growth of malignant cells. It has been confirmed that SLIT/ROBO play contradictory roles in tumorigenesis. Here, we discuss the tumor promotion and tumor suppression roles of the SLIT/ROBO pathway in tumor growth, angiogenesis, migration, and the tumor microenvironment. Understanding these roles will help us develop more effective cancer therapies.

Reduced USP33 expression in gastric cancer decreases inhibitory effects of Slit2-Robo1 signalling on cell migration and EMT

OBJECTIVES

Gastric cancer (GC) is one of the most common cancers in the world, causing a large number of deaths every year. The Slit-Robo signalling pathway, initially discovered for its critical role in neuronal guidance, has recently been shown to modulate tumour invasion and metastasis in several human cancers. However, the role of Slit-Robo signalling and the molecular mechanisms underlying its role in the pathogenesis of gastric cancer remains to be elucidated.

MATERIALS AND METHODS

Slit2, Robo1 and USP33 expressions were analysed in datasets obtained from the Oncomine database and measured in human gastric cancer specimens. The function of Slit2-Robo1-USP33 signalling on gastric cancer cells migration and epithelial-mesenchymal transition (EMT) was studied both in vitro and in vivo. The mechanism of the interaction between Robo1 and USP33 was explored by co-IP and ubiquitination protein analysis.

RESULTS

The mRNA and protein levels of Slit2 and Robo1 are lower in GC tissues relative to those in adjacent healthy tissues. Importantly, Slit2 inhibits GC cell migration and suppresses EMT process in a Robo-dependent manner. The inhibitory function of Slit2-Robo1 is mediated by ubiquitin-specific protease 33 (USP33) via deubiquitinating and stabilizing Robo1. USP33 expression is decreased in GC tissues, and reduced USP33 level is correlated with poor patient survival.

CONCLUSIONS

Our study reveals the inhibitory function of Slit-Robo signalling in GC and uncovers a role of USP33 in suppressing cancer cell migration and EMT by enhancing Slit2-Robo1 signalling. USP33 represents a feasible choice as a prognostic biomarker for GC.

Comparative Analysis of the Transcriptome and Proteome during Mouse Placental Development

The condition of the placenta is a determinant of the short- and long-term health of the mother and the fetus. However, critical processes occurring in early placental development, such as trophoblast invasion and establishment of placental metabolism, remain poorly understood. To gain a better understanding of the genes involved in regulating these processes, we utilized a multiomics approach, incorporating transcriptome, proteome, and phosphoproteome data generated from mouse placental tissue collected at two critical developmental time points. We found that incorporating information from both the transcriptome and proteome identifies genes associated with time point-specific biological processes, unlike using the proteome alone. We further inferred genes upregulated on the basis of the proteome data but not the transcriptome data at each time point, leading us to identify 27 genes that we predict to have a role in trophoblast migration or placental metabolism. Finally, using the phosphoproteome data set, we discovered novel phosphosites that may play crucial roles in the regulation of placental transcription factors. By generating the largest proteome and phosphoproteome data sets in the developing placenta, and integrating transcriptome analysis, we uncovered novel aspects of placental gene regulation.

A crucial role for Arf6 in the response of commissural axons to Slit

A switch in the response of commissural axons to the repellent Slit is crucial for ensuring that they cross the ventral midline only once. However, the underlying mechanisms remain to be elucidated. We have found that both endocytosis and recycling of Robo1 receptor are crucial for modulating Slit sensitivity in vertebrate commissural axons. Robo1 endocytosis and its recycling back to the cell surface maintained the stability of axonal Robo1 during Slit stimulation. We identified Arf6 guanosine triphosphatase and its activators, cytohesins, as previously unknown components in Slit-Robo1 signalling in vertebrate commissural neurons. Slit-Robo1 signalling activated Arf6. The Arf6-deficient mice exhibited marked defects in commissural axon midline crossing. Our data showed that a Robo1 endocytosis-triggered and Arf6-mediated positive-feedback strengthens the Slit response in commissural axons upon their midline crossing. Furthermore, the cytohesin-Arf6 pathways modulated this self-enhancement of the Slit response before and after midline crossing, resulting in a switch that reinforced robust regulation of axon midline crossing. Our study provides insights into endocytic trafficking-mediated mechanisms for spatiotemporally controlled axonal responses and uncovers new players in the midline switch in Slit responsiveness of commissural axons.

Ontology groups representing angiogenesis and blood vessels development are highly up-regulated during porcine oviductal epithelial cells long-term real-time proliferation – a primary cell culture approach

The morphological and biochemical modification of oviductal epithelial cells (OECs) belongs to the group of compound processes responsible for proper oocyte transport and successful fertilization. The cellular interactions between cumulus-oocyte complexes (COCs) and oviductal epithelial cells (OECs) are crucial for this unique mechanism. In the present study we have analyzed angiogenesis and blood vessel development processes at transcript levels. By employing microarrays, four ontological groups associated with these mechanisms have been described. Differentially expressed genes belonging to the “angiogenesis”, “blood circulation”, “blood vessel development” and “blood vessel morphogenesis” GO BP terms were investigated as a potential markers for the creation of new blood vessels in cells under in vitro primary culture conditions.

[USP33 suppresses lung adenocarcinoma lung cell invasion and metastasis by down-regulating SLIT2/ROBO1 signaling pathway]

OBJECTIVE

To investigate the role of USP33 as an independent prognostic marker in the regulation of SLIT2/ROBO1 signaling pathway to inhibit lung adenocarcinoma invasion and metastasis.

METHODS

The expression of USP33 in 20 lung adenocarcinoma specimens was detected by qPCR and immunohistochemistry. A549 and SPC-A-1 cells with small interfering RNA (siRNA)-mediated USP33 silencing were examined for changes in invasion and metastasis abilities using scratch assay and Matrigel assay. Western blotting was used to detect the expression of SLIT2 and ROBO1 in the cells after USP33 silencing and the expression of USP33 after interleukin-6 (IL-6) stimulation.

RESULTS

qPCR and immunohistochemistry showed that USP33 was significantly decreased in lung adenocarcinoma tissues as compared with the adjacent tissues. USP33 silencing in A549 and SPC-A-1 cells significantly promoted the cell migration, invasion and metastasis and obviously down-regulated the expressions of SLIT2 and ROBO1. IL-6 stimulation of the cells obviously enhanced the expression of USP33.

CONCLUSIONS

USP33 silencing can promote the migration, invasion and metastasis of lung adenocarcinoma cells in vitro, and the mechanism may involve IL-6 and SLIT2/ROBO1 signaling pathways.

High Expression of Ubiquitin-Specific Protease 8 (USP8) Is Associated with Poor Prognosis in Patients with Cervical Squamous Cell Carcinoma

BACKGROUND Cervical cancer is one of the most common female malignancies in the world. The ubiquitin-specific protease 8 (USP8) functions by removing ubiquitin from protein substrates, and its potential role in cancer development was recently uncovered in lung cancer. The aim of this study was to investigate the expression and function of USP8 in cervical squamous cell carcinoma (CSCC). MATERIAL AND METHODS Immunohistochemical staining and quantitative PCR were performed to explore the expression of USP8 in both CSCC tissues and adjacent normal cervical tissues. Univariate and multivariate analyses were conducted to evaluate the clinical significance of USP8 in CSCC. Proliferation, migration, and invasion abilities of 2 CSCC cell lines were assessed after overexpression or silencing USP8, respectively. RESULTS Both the RNA and protein levels of USP8 were upregulated in CSCC tissues compared to normal cervical tissues. High expression of USP8 was correlated with advanced tumor stage and high recurrence risk. Moreover, USP8 was identified as a novel independent prognostic factor for CSCC patients. Cellular studies showed that USP8 can enhance the proliferation, migration, and invasion abilities of CSCC cells, thereby promoting tumor progression. CONCLUSIONS High expression of USP8 is frequent in CSCC tissues, which promotes tumor proliferation and invasion, and is correlated with a poor overall survival. Targeting USP8 may be a novel direction for drug development for CSCC therapy.

Reduced Expression of Deubiquitinase USP33 Is Associated with Tumor Progression and Poor Prognosis of Gastric Adenocarcinoma

Background

Ubiquitin-specific peptidase 33 (USP33) is a deubiquitinase that balances the ubiquitin status of proteins. It has been reported to act as a tumor suppressor in colorectal cancer and lung cancer. However, the expression pattern and clinical significance of USP33 have not been investigated in gastric adenocarcinoma (GAC).

Material/Methods

We explored the USP33 protein and RNA levels by immunohistochemistry (IHC), Western blot analysis, and qRT-PCR. The Pearson chi-square test was performed to evaluate the statistical associations between USP33 level and patient characteristics. Additionally, the relationship between USP33 expression and patient survival was investigated. Cellular studies, including proliferation assay, migration assay, and invasion assay, were conducted to demonstrate the underlying mechanisms of USP33 in GAC progression.

Results

This study included 121 patients with GAC. USP33 showed a decreased expression in GAC tissues compared to adjacent normal gastric tissues. Low expression of USP33 was correlated with invasion depth and advanced TNM stage. According to survival analysis, upper location of tumor (P=0.003), invasion depth (P=0.048), advanced TNM stage (P=0.001), and low USP33 level (P=0.001) were all associated with poor overall survival of GAC patients. Cox analysis confirmed the independent role of USP33 in predicting patient survival. Cell experiments showed that USP33 overexpression significantly inhibited the proliferation, migration, and invasion of GAC cells.

Conclusions

USP33 was downregulated in GAC, and was an independent prognostic factor. In vitro results demonstrated the role of USP33 in suppressing tumor progression, suggesting that the developing an agonist of USP33 may be a novel direction for chemotherapy development.

MicroRNA-365 promotes lung carcinogenesis by downregulating the USP33/SLIT2/ROBO1 signalling pathway

Background

Abnormal microRNA expression is closely related to cancer occurrence and development. miR-365a-3p plays an oncogenic role in skin cancer, but its role in lung cancer remains unclear. In this study, we aimed to investigate its role and underlying molecular mechanisms in lung cancer.

Methods

Western blot and real-time quantitative PCR (qPCR) were used to detect the expression of miR-365a-3p in lung adenocarcinoma and lung cancer cell lines. The effects of miR-365a-3p on lung cancer cell proliferation, migration, and invasion were also explored in vitro. The potential miR-365a-3p that targets USP33 was determined by dual luciferase reporter assay and verified by qPCR and western blot analysis. miR-365a-3p acts as an oncogene by promoting lung carcinogenesis via the downregulation of the miR-365a/USP33/SLIT2/ROBO1 axis based on western blot analysis. Subcutaneous tumourigenesis further demonstrated that miR-365a-3p promotes tumour formation in vivo.

Results

miR-365a-3p was upregulated in lung adenocarcinoma and lung cancer cell lines. Overexpression of miR-365a-3p promoted and inhibition of miR-365a-3p suppressed the proliferation, migration, and invasion of lung cancer cells. We identified USP33 as the downstream target of miR-365a-3p and observed a negative correlation between miR-365a-3p and USP33 expression in lung adenocarcinoma patients. The miR-365/USP33/SLIT2/ROBO1 axis, a new mechanism, was reported to inhibit the invasion and metastasis of lung cancer. A nude mouse model of lung cancer further verified these findings.

Conclusions

In summary, miR-365a-3p acts as an oncogene by promoting lung carcinogenesis via the downregulation of the USP33/SLIT2/ROBO1 signalling pathway, making the miR-365/USP33/SLIT2/ROBO1 axis a new mechanism of lung cancer promotion and a novel therapeutic target for predicting prognosis and response to gene therapy.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0563-6) contains supplementary material, which is available to authorized users.

Profiling plasma extracellular vesicle by pluronic block-copolymer based enrichment method unveils features associated with breast cancer aggression, metastasis and invasion

Extracellular vesicle (EV)-based liquid biopsies have been proposed to be a readily obtainable biological substrate recently for both profiling and diagnostics purposes. Development of a fast and reliable preparation protocol to enrich such small particles could accelerate the discovery of informative, disease-related biomarkers. Though multiple EV enrichment protocols are available, in terms of efficiency, reproducibility and simplicity, precipitation-based methods are most amenable to studies with large numbers of subjects. However, the selectivity of the precipitation becomes critical. Here, we present a simple plasma EV enrichment protocol based on pluronic block copolymer. The enriched plasma EV was able to be verified by multiple platforms. Our results showed that the particles enriched from plasma by the copolymer were EV size vesicles with membrane structure; proteomic profiling showed that EV-related proteins were significantly enriched, while high-abundant plasma proteins were significantly reduced in comparison to other precipitation-based enrichment methods. Next-generation sequencing confirmed the existence of various RNA species that have been observed in EVs from previous studies. Small RNA sequencing showed enriched species compared to the corresponding plasma. Moreover, plasma EVs enriched from 20 advanced breast cancer patients and 20 age-matched non-cancer controls were profiled by semi-quantitative mass spectrometry. Protein features were further screened by EV proteomic profiles generated from four breast cancer cell lines, and then selected in cross-validation models. A total of 60 protein features that highly contributed in model prediction were identified. Interestingly, a large portion of these features were associated with breast cancer aggression, metastasis as well as invasion, consistent with the advanced clinical stage of the patients. In summary, we have developed a plasma EV enrichment method with improved precipitation selectivity and it might be suitable for larger-scale discovery studies.

Prognostic significance of USP33 in advanced colorectal cancer patients: new insights into β-arrestin-dependent ERK signaling

Patients with liver metastases of colorectal cancer (CRCLM) have a poorer prognosis compared to colorectal cancer (CRC) patients in local stage. Evaluating the recurrence and overall survival of advanced patients is critical in improving disease treatment and clinical outcome. Here we investigated the expression pattern of USP33, a deubiquitinating enzyme, in both primary CRC tissues and liver metastases tissues. Univariate and multivariate analyses identified that low expression of USP33 in CRCLM tissues indicated high recurrence risk and poor overall prognosis. Overexpression of USP33 can significantly inhibit cell proliferation, migration, and invasion. On the other hand, USP33 knock-down promoted cell proliferation and invasion under SDF-1 stimulation; whereas dynasore (an internalization inhibitor) pretreatment in USP33 silencing cells showed a distinct antipromoting effect, revealing the participation of CXCR4 internalization in regulating tumor progress. Further results verified that USP33 can deubiquitinate β-arrestin2, subsequently block the internalization of SDF-1-stimulated CXCR4, and disrupt β-arrestin-dependent ERK activation. The existence and functions of β-arrestin-dependent signaling have been previously determined in several Gs-coupled receptors, such as β2-adrenergic receptor and angiotensin receptor subtype 1a; however, little is known about this in Gi-coupled receptors. Our study not only established USP33 as a novel prognosis biomarker in advanced CRCLM patients, but also highlighted the significance of β-arrestin-dependent ERK signaling in cancer development.

SUV39H2 promotes colorectal cancer proliferation and metastasis via tri-methylation of the SLIT1 promoter

Suppressor of variegation 3-9 homolog 2 (SUV39H2) is a member of the SUV39H subfamily of lysine methyltransferases. Its role in colorectal cancer (CRC) proliferation and metastasis has remained unexplored. Here, we determined that SUV39H2 was upregulated in CRC tissues compared with that in adjacent non-neoplastic tissues. Further statistical analysis revealed that high SUV39H2 expression was strongly associated with distant metastasis (P = 0.016) and TNM stage (P = 0.038) and predicted a shorter overall survival (OS; P = 0.018) and progression-free survival (PFS; P = 0.018) time for CRC patients. Both in vitro and in vivo assays demonstrated that ectopically expressed SUV39H2 enhanced CRC proliferation and metastasis, while SUV39H2 knockdown inhibited CRC proliferation and metastasis. A molecular screen of SUV39H2 targets found that SUV39H2 negatively regulated the expression of SLIT guidance ligand 1 (SLIT1). Moreover, rescue assays suggested that SLIT1 could antagonize the function of SUV39H2 in CRC. Mechanistic studies indicated that SUV39H2 can directly bind to the SLIT1 promoter, suppressing SLIT1 transcription by catalyzing histone H3 lysine 9 (H3K9) tri-methylation. In summary, we propose that SUV39H2 can predict CRC patient prognosis and stimulate CRC malignant phenotypes via SLIT1 promoter tri-methylation.

Deubiquitinase USP33 is negatively regulated by β-TrCP through ubiquitin-dependent proteolysis

Ubiquitin-mediated proteolysis regulates cellular levels of various proteins, and therefore plays important roles in controlling cell signaling and disease progression. The Skp1-Cul1-F-box ubiquitin ligase β-TrCP is recognized as an important negative regulator for numerous key signaling proteins. Recently, the deubiquitinases (DUBs) have turned out to be essential to regulate signaling pathways related to human diseases. However, whether β-TrCP is able to regulate the deubiquitinase family members remains largely unexplored. Here, we found that β-TrCP downregulated cellular levels of endogenous USP33. We also revealed that β-TrCP interacted with USP33 independently of the classic binding motif for β-TrCP, and mediated USP33 degradation via the ubiquitin proteasome pathway. Furthermore, we found that the WD40 motif of β-TrCP and 201-400 amino acid motif of USP33 are required for the interaction between β-TrCP and USP33. Consequently, β-TrCP attenuated USP33-mediated inhibition of cell proliferation and cell invasion. Taken together, our study clarified that the E3 ligase β-TrCP regulates cellular USP33 levels by the ubiquitin-proteasomal proteolysis.

WP1130 increases cisplatin sensitivity through inhibition of usp9x in estrogen receptor-negative breast cancer cells

Approximately 30% of all breast cancers are caused by a lack of estrogen receptor (ER), which renders the cancer resistant to endocrine-based therapy. Many studies suggest that ubiquitin-specific peptidase 9, X-linked (usp9x) regulates multiple cellular behaviors, such as tumor growth, invasion, and resistance to chemotherapeutic agents. This study aimed to evaluate the anti-tumor effects of WP1130, a partially selective inhibitor of deubiquitinating enzymes, in breast cancer cells. We found that WP1130 enhanced cisplatin cytotoxicity in ER-negative tumor cells (MDA-MB-231 and MDA-MB-468), but had little effect in ER-positive Bcap-37 cells. Western blot analysis revealed that usp9x expression was dramatically lower in ER-positive cells compared to that in ER-negative cells. Furthermore, WP1130 treatment suppressed the expression of usp9x and Mcl-1 in ER-negative cells, but not in ER-positive cells. In addition, we found that knockdown of usp9x diminished the chemosensitization activity of WP1130 on breast cancer cells in the presence of cisplatin. Taken together, these results demonstrated that combined treatment with WP1130 could increase the cisplatin sensitivity in a usp9x-dependent manner in estrogen receptor-negative breast cancer cells.

The epigenetic landscape of renal cancer

The majority of kidney cancers are associated with mutations in the von Hippel-Lindau gene and a small proportion are associated with infrequent mutations in other well characterized tumour-suppressor genes. In the past 15 years, efforts to uncover other key genes involved in renal cancer have identified many genes that are dysregulated or silenced via epigenetic mechanisms, mainly through methylation of promoter CpG islands or dysregulation of specific microRNAs. In addition, the advent of next-generation sequencing has led to the identification of several novel genes that are mutated in renal cancer, such as PBRM1, BAP1 and SETD2, which are all involved in histone modification and nucleosome and chromatin remodelling. In this Review, we discuss how altered DNA methylation, microRNA dysregulation and mutations in histone-modifying enzymes disrupt cellular pathways in renal cancers.

Human placental multipotent mesenchymal stromal cells modulate placenta angiogenesis through Slit2-Robo signaling

The objective of this study was to investigate whether human placental multipotent mesenchymal stromal cell (hPMSC)-derived Slit2 and endothelial cell Roundabout (Robo) receptors are involved in placental angiogenesis. The hPMSC-conditioned medium and human umbilical vein endothelial cells were studied for Slit2 and Robo receptor expression by immunoassay and RT-PCR. The effect of the conditioned medium of hPMSCs with or without Slit2 depletion on endothelial cells was investigated by in vitro angiogenesis using growth factor-reduced Matrigel. hPMSCs express Slit2 and both Robo1 and Robo4 are present in human umbilical vein endothelial cells. Human umbilical vein endothelial cells do not express Robo2 and Robo3. The hPMSC-conditioned medium and Slit2 recombinant protein significantly inhibit the endothelial cell migration, but not by the hPMSC-conditioned medium with Slit2 depletion. The hPMSC-conditioned medium and Slit2 significantly enhance endothelial tube formation with increased cumulated tube length, polygonal network number and vessel branching point number compared to endothelial cells alone. The tube formation is inhibited by the depletion of Slit2 from the conditioned medium, or following the expression of Robo1, Robo4, and both receptor knockdown using small interfering RNA. Furthermore, co-immunoprecipitation reveals Slit2 binds to Robo1 and Robo4. Robo1 interacts and forms a heterodimeric complex with Robo4. These results suggest the implication of both Robo receptors with Slit2 signaling, which is involved in endothelial cell angiogenesis. Slit2 in the conditioned medium of hPMSCs has functional effect on endothelial cells and may play a role in placental angiogenesis.

Cell Adhesion Molecules and Ubiquitination-Functions and Significance

Cell adhesion molecules of the immunoglobulin (Ig) superfamily represent the biggest group of cell adhesion molecules. They have been analyzed since approximately 40 years ago and most of them have been shown to play a role in tumor progression and in the nervous system. All members of the Ig superfamily are intensively posttranslationally modified. However, many aspects of their cellular functions are not yet known. Since a few years ago it is known that some of the Ig superfamily members are modified by ubiquitin. Ubiquitination has classically been described as a proteasomal degradation signal but during the last years it became obvious that it can regulate many other processes including internalization of cell surface molecules and lysosomal sorting. The purpose of this review is to summarize the current knowledge about the ubiquitination of cell adhesion molecules of the Ig superfamily and to discuss its potential physiological roles in tumorigenesis and in the nervous system.

The emerging role of Slit-Robo pathway in gastric and other gastro intestinal cancers

Gastric cancer remains one of the most common cancers worldwide and one of the leading cause for cancer-related deaths. Due to the high frequency of metastasis, it is still one of the most lethal malignancies in which kinds of signaling pathways are involved in. The Roundabout (ROBO) receptors and their secreted SLIT glycoprotein ligands, which were originally identified as important axon guidance molecules, have implication in the regulation of neurons and glia, leukocytes, and endothelial cells migration. Recent researches also put high emphasis on the important roles of the Slit-Robo pathway in tumorigenesis, cancer progression and metastasis. Herein we provide a comprehensive review on the role of these molecules and their associated signaling pathway in gastric and other gastrointestinal cancers. Improved knowledge of the Slit-Robo signaling pathway in gastric carcinoma will be useful for deep understanding the mechanisms of tumor development and identifying ideal targets of anticancer therapy in gastric carcinoma.

Function of Slit/Robo signaling in breast cancer

Slit and Robo are considered tumor suppressors because they are frequently inactivated in various tumor tissue. These genes are closely correlated with CpG hypermethylation in their promoters. The Slit/Robo signaling pathway is reportedly involved in breast cancer development and metastasis. Overexpression of Slit/ Robo induces its tumor suppressive effects possibly by inactivating the β-catenin/LEF/TCF and PI3K/Akt signaling pathways or by altering β-catenin/E-cadherin-mediated cell-cell adhesion in breast cancer cells. Furthermore, loss of Slit proteins or their Robo receptors upregulates the CXCL12/CXCR4 signaling axis in human breast carcinoma. In addition, this pathway regulates the distant migration of breast cancer cells not only by mediating the phosphorylation of the downstream molecules of CXCL12/CXCR4 and srGAPs, such as PI3K/ Src, RAFTK/ Pyk2, and CDC42, but also by regulating the activities of MAP kinases. This review includes recent studies on the functions of Slit/Robo signaling in breast cancer and its molecular mechanisms.

Myo9b is a key player in SLIT/ROBO-mediated lung tumor suppression

Emerging evidence indicates that the neuronal guidance molecule SLIT plays a role in tumor suppression, as SLIT-encoding genes are inactivated in several types of cancer, including lung cancer; however, it is not clear how SLIT functions in lung cancer. Here, our data show that SLIT inhibits cancer cell migration by activating RhoA and that myosin 9b (Myo9b) is a ROBO-interacting protein that suppresses RhoA activity in lung cancer cells. Structural analyses revealed that the RhoGAP domain of Myo9b contains a unique patch that specifically recognizes RhoA. We also determined that the ROBO intracellular domain interacts with the Myo9b RhoGAP domain and inhibits its activity; therefore, SLIT-dependent activation of RhoA is mediated by ROBO inhibition of Myo9b. In a murine model, compared with control lung cancer cells, SLIT-expressing cells had a decreased capacity for tumor formation and lung metastasis. Evaluation of human lung cancer and adjacent nontumor tissues revealed that Myo9b is upregulated in the cancer tissue. Moreover, elevated Myo9b expression was associated with lung cancer progression and poor prognosis. Together, our data identify Myo9b as a key player in lung cancer and as a ROBO-interacting protein in what is, to the best of our knowledge, a newly defined SLIT/ROBO/Myo9b/RhoA signaling pathway that restricts lung cancer progression and metastasis. Additionally, our work suggests that targeting the SLIT/ROBO/Myo9b/RhoA pathway has potential as a diagnostic and therapeutic strategy for lung cancer.

ROBO3 promotes growth and metastasis of pancreatic carcinoma

Pancreatic carcinoma is a highly lethal malignancy with an extremely poor prognosis. Recent genome-wide studies have implicated axon guidance pathways, including the SLIT/ROBO pathway, in pancreatic tumor development and progression. Here we showed that ROBO3 expression is up-regulated in pancreatic cancer tissue samples and cell lines. Over-expression of ROBO3 promotes pancreatic cancer cell growth, invasion and metastasis in vitro and in mouse xenograft tumor models. We identified miR-383 as a suppressor of ROBO3, and revealed its expression to be inversely correlated with ROBO3. Over-expression of ROBO3 activates Wnt pathway components, β-catenin and GSK-3, and the expression of markers indicating an EMT. By means of immunoprecipitation, we revealed an interaction between Wnt inhibitor SFRP and ROBO3 in pancreatic cancer cell lines. Our work suggests that ROBO3 may contribute to the progression of pancreatic cancer by sequestering Wnt inhibitor SFRP, which in turn leads to increased Wnt/β-catenin pathway activity. We also confirmed that ROBO3 increases with clinical grade and miR-383 expression is inversely correlated to that of ROBO3.

Deubiquitinating enzymes in cellular signaling and disease regulation

Protein post-translational modification by ubiquitin represents a complex signaling system that regulates many cellular events including proteostasis to intercellular communications. Deubiquitinating enzymes (DUBs) that specifically disassemble Ub-chains or regulate ubiquitin homeostasis reside as a central component in ubiquitin signaling. Human genome encodes almost 100 DUBs and majority of them are not well characterized. Considerable progress has been made in the understanding of enzymatic mechanism; however, their cellular substrate specificity and regulation are largely unknown. Involvement of DUBs in disease regulation has been depicted since its discovery and several attempts have been made for evaluating DUBs as a drug target. In this review, we have updated briefly a new insight of DUBs activity, their cellular role, disease regulation, and therapeutic potential.

USP33 mediates Slit-Robo signaling in inhibiting colorectal cancer cell migration

Originally discovered in neuronal guidance, the Slit-Robo pathway is emerging as an important player in human cancers. However, its involvement and mechanism in colorectal cancer (CRC) remains to be elucidated. Here, we report that Slit2 expression is reduced in CRC tissues compared with adjacent noncancerous tissues. Extensive promoter hypermethylation of the Slit2 gene has been observed in CRC cells, which provides a mechanistic explanation for the Slit2 downregulation in CRC. Functional studies showed that Slit2 inhibits CRC cell migration in a Robo-dependent manner. Robo-interacting ubiquitin-specific protease 33 (USP33) is required for the inhibitory function of Slit2 on CRC cell migration by deubiquitinating and stabilizing Robo1. USP33 expression is downregulated in CRC samples, and reduced USP33 mRNA levels are correlated with increased tumor grade, lymph node metastasis and poor patient survival. Taken together, our data reveal USP33 as a previously unknown tumor-suppressing gene for CRC by mediating the inhibitory function of Slit-Robo signaling on CRC cell migration. Our work suggests the potential value of USP33 as an independent prognostic marker of CRC.