Net1 and Myeov: computationally identified mediators of gastric cancer

Super-enhancer mediated upregulation of MYEOV suppresses ferroptosis in lung adenocarcinoma

Super-enhancers (SEs) exerted a crucial role in regulating the transcription of oncogenes across various malignancies while the roles of SEs driven genes and the core regulatory elements remain elusive in LUAD. In this study, cancer-specific-SE-genes of lung adenocarcinoma (LUAD) were profiled through H3K27ac ChIP-seq data of cancer cell lines and normal lung tissues, which enriched in in biological processes and pathways integral to the pathophysiology of LUAD. Based on this study, LUAD cells were susceptible to SEs inhibitors, with a reduction of cell proliferation as well as an elevation of apoptosis upon JQ1 or THZ1 intervention. Moreover, the integration of SEs landscapes, CRISPRi, ChIP-PCR, Hi-C data analysis and dual-luciferase reporter assays revealed that myeloma overexpressed gene (MYEOV) was aberrantly overexpressed in LUAD via transcriptional activation by the core SE elements. Functionally, the knockdown of MYEOV undermined cell proliferation in vitro and tumor growth in vivo. In addition, the knockdown of MYEOV generated a prominent ferroptotic phenotype, characterized by elevation of intracellular ferrous iron, reactive oxygen species and lipid peroxidation, together with alteration in marker proteins (SLC7A11, GPX4, FTH1, and ACSL4). Instead, the overexpression of MYEOV accelerated cell proliferation and abrogated ferroptosis. Clinically, the overexpression of MYEOV was observed in LUAD tissues indicating a poor prognosis in patients with LUAD. Mechanistically, SMPD1-induced autophagic degradation of GPX4 assumed a crucial role in the process of ferroptosis triggered by MYEOV knockdown. Serving as an oncogene repressing ferroptosis, promoting proliferation as well as shortening survival in LUAD, SEs-mediated activation of MYEOV might distinguish as a promising therapeutic target.

NET1 is a critical regulator of spindle assembly and actin dynamics in mouse oocytes

BACKGROUND

Neuroepithelial transforming gene 1 (NET1) is a RhoA subfamily guanine nucleotide exchange factor that governs a wide array of biological processes. However, its roles in meiotic oocyte remain unclear. We herein demonstrated that the NET1-HACE1-RAC1 pathway mediates meiotic defects in the progression of oocyte maturation.

METHODS

NET1 was reduced using a specific small interfering RNA in mouse oocytes. Spindle assembly, chromosomal alignment, the actin cap, and chromosomal spreads were visualized by immunostaining and analyzed under confocal microscopy. We also applied mass spectroscopy, and western blot analysis for this investigation.

RESULTS

Our results revealed that NET1 was localized to the nucleus at the GV stage, and that after GVBD, NET1 was localized to the cytoplasm and predominantly distributed around the chromosomes, commensurate with meiotic progression. NET1 resided in the cytoplasm and significantly accumulated on the spindle at the MI and MII stages. Mouse oocytes depleted of Net1 exhibited aberrant first polar body extrusion and asymmetric division defects. We also determined that Net1 depletion resulted in reduced RAC1 protein expression in mouse oocytes, and that NET1 protected RAC1 from degradation by HACE1, and it was essential for actin dynamics and meiotic spindle formation. Importantly, exogenous RAC1 expression in Net1-depleted oocytes significantly rescued these defects.

CONCLUSIONS

Our results suggest that NET1 exhibits multiple roles in spindle stability and actin dynamics during mouse oocyte meiosis.

Identification of basement membrane-related signatures for estimating prognosis, immune infiltration landscape and drug candidates in pancreatic adenocarcinoma

Background: Pancreatic adenocarcinoma (PAAD) is a frequent digestive system cancer, which has high mortality and bad outcome. However, the role of basement membrane (BM)-related gene in assessing patient's outcome, microenvironment and treatment response remain unclear. Methods: Basement membrane (BM)-associated genes were detected by univariate and least absolute shrinkage and selection operator (LASSO) Cox regression analyses using data from the TCGA databases. A risk score system was constructed to distinguish patients in the high- and low-risk groups. Prognostic gene distribution in various immune cell forms was explored through scRNA-seq. Immune cell infiltration was assessed using CIBERSORT and ESTIMATE. The IC50 of common chemotherapeutic drugs and useful molecule compounds were evaluated. The mRNA and protein expression of important signatures were validated utilizing GEPIA and HPA databases. Results: Compared to low risk PAAD patients, PAAD patients with high risk showed a significant much worse overall survival (OS). Risk score of BM-associated genes could estimate patient outcome well, and areas under the curve (AUC) of receiver operating characteristic (ROC) survival curve were 0.76, 0.85, and 0.85 at 1-, 3-, and 5-year. Clinical impact curve (CIC) curve demonstrated the clinical importance of risk score. scRNA-seq revealed that BM-related genes were mainly distributed in malignant cells. Significant variations existed in the immune microenvironment, immune checkpoint expression and chemotherapy response between the studied groups. Furthermore, the mRNA expression levels of FAM83A, LY6D, MET, MUC16, MYEOV, and WNT7A were elevated in PAAD tissues, while the protein expression patterns of LY6D, MET, MUC16, and WNT7A were higher in tumor sample. RO-90-7501, Scriptaid, TG-101348, XMD-892, and XMD-1150 may be valuable small molecule drugs to treat PAAD. Conclusions: In conclusion, we develop a novel BM-related gene signature provide new insights and targets for the diagnosis, outcome estimation, candidate drugs and therapy management of PAAD patients.

Src stimulates Abl-dependent phosphorylation of the guanine exchange factor Net1A to promote its cytosolic localization and cell motility

The neuroepithelial cell transforming gene 1 (Net1) is a guanine nucleotide exchange factor for the small GTPase RhoA that promotes cancer cell motility and metastasis. Two isoforms of Net1 exist, Net1 and Net1A, both of which are sequestered in the nucleus in quiescent cells to prevent aberrant RhoA activation. Many cell motility stimuli drive cytosolic relocalization of Net1A, but mechanisms controlling this event are not fully understood. Here, we demonstrate that epithelial growth factor stimulates protein kinase Src- and Abl1-dependent phosphorylation of Net1A to promote its cytosolic localization. We show that Abl1 efficiently phosphorylates Net1A on Y373, and that phenylalanine substitution of Y373 prevents Net1A cytosolic localization. Furthermore, we found that Abl1-driven cytosolic localization of Net1A does not require S52, which is a phosphorylation site of a different kinase, c-Jun N-terminal kinase, that inhibits nuclear import of Net1A. However, we did find that MKK7-stimulated cytosolic localization of Net1A does require Y373. We also demonstrate that aspartate substitution at Y373 is sufficient to promote Net1A cytosolic accumulation, and expression of Net1A Y373D potentiates epithelial growth factor-stimulated RhoA activation, downstream myosin light chain 2 phosphorylation, and F-actin accumulation. Moreover, we show that expression of Net1A Y373D in breast cancer cells also significantly increases cell motility and Matrigel invasion. Finally, we show that Net1A is required for Abl1-stimulated cell motility, which is rescued by expression of Net1A Y373D, but not Net1A Y373F. Taken together, this work demonstrates a novel mechanism controlling Net1A subcellular localization to regulate RhoA-dependent cell motility and invasion.

AAV-Net1 facilitates the trans-differentiation of supporting cells into hair cells in the murine cochlea

Mechanosensitive hair cells (HCs) in the cochlear sensory epithelium are critical for sound detection and transduction. Mammalian HCs in the cochlea undergo cytogenesis during embryonic development, and irreversible damage to hair cells postnatally is a major cause of deafness. During the development of the organ of Corti, HCs and supporting cells (SCs) originate from the same precursors. In the neonatal cochlea, damage to HCs activates adjacent SCs to act as HC precursors and to differentiate into new HCs. However, the plasticity of SCs to produce new HCs is gradually lost with cochlear development. Here, we delineate an essential role for the guanine nucleotide exchange factor Net1 in SC trans-differentiation into HCs. Net1 overexpression mediated by AAV-ie in SCs promoted cochlear organoid formation and HC differentiation under two and three-dimensional culture conditions. Also, AAV-Net1 enhanced SC proliferation in Lgr5-EGFPCreERT2 mice and HC generation as indicated by lineage tracing of HCs in the cochleae of Lgr5-EGFPCreERT2/Rosa26-tdTomatoloxp/loxp mice. We further found that the up-regulation of Wnt/β-catenin and Notch signaling in AAV-Net1-transduced cochleae might be responsible for the SC proliferation and HC differentiation. Also, Net1 overexpression in SCs enhanced SC proliferation and HC regeneration and survival after HC damage by neomycin. Taken together, our study suggests that Net1 might serve as a potential target for HC regeneration and that AAV-mediated gene regulation may be a promising approach in stem cell-based therapy in hearing restoration.

Socioeconomic changes predict genome-wide DNA methylation in childhood

Childhood socioeconomic position (SEP) is a major determinant of health and well-being across the entire life course. To effectively prevent and reduce health risks related to SEP, it is critical to better understand when and under what circumstances socioeconomic adversity shapes biological processes. DNA methylation (DNAm) is one such mechanism for how early life adversity 'gets under the skin'. In this study, we evaluated the dynamic relationship between SEP and DNAm across childhood using data from 946 mother-child pairs in the Avon Longitudinal Study of Parents and Children. We assessed six SEP indicators spanning financial, occupational and residential domains during very early childhood (ages 0-2), early childhood (ages 3-5) and middle childhood (ages 6-7). Epigenome-wide DNAm was measured at 412 956 cytosine-guanines (CpGs) from peripheral blood at age 7. Using an innovative two-stage structured life-course modeling approach, we tested three life-course hypotheses for how SEP shapes DNAm profiles-accumulation, sensitive period and mobility. We showed that changes in the socioeconomic environment were associated with the greatest differences in DNAm, and that middle childhood may be a potential sensitive period when socioeconomic instability is especially important in shaping DNAm. Top SEP-related DNAm CpGs were overrepresented in genes involved in pathways important for neural development, immune function and metabolic processes. Our findings highlight the importance of socioeconomic stability during childhood and if replicated, may emphasize the need for public programs to help children and families experiencing socioeconomic instability and other forms of socioeconomic adversity.

Construction and validation of a novel prognostic model for lung squamous cell cancer based on N6-methyladenosine-related genes

Background

N6-methyladenosine (m6A) is the most prevalent modification in mRNA in biological processes and associated with various malignant tumor initiation and progression. The present study aimed to construct a prognostic risk model based on m6A-related genes (the downstream genes influenced by m6A modulators) for LUSC.

Methods

Based on TCGA, we stratified LUSC patients with and without genetic alteration of m6A modulators into altered and unaltered groups. Using univariate Cox and Lasso regression analyses, we identified prognostic m6A-related genes to construct a prognostic risk model. We then applied a multivariate Cox proportional regression model and the survival analysis to evaluate the risk model. Moreover, we performed the Receiver operating characteristic curve to assess the efficiency of the prognostic model based on TCGA and GSE43131. We analyzed the characteristics of tumor-associated immune cell infiltration in LUSC through the CIBERSORT method.

Results

Three m6A-related genes (FAM71F1, MT1E, and MYEOV) were identified as prognostic genes for LUSC. A novel prognostic risk model based on the three m6A-related genes was constructed. The multivariate Cox analysis showed that the prognostic risk model was an independent risk factor (HR = 2.44, 95% CI = 1.21~3.56, p = 0.029). Patients with a high-risk group had worse overall survival both in TCGA (p = 0.018) and GSE43131 (p = 0.00017). The 1, 2, and 3-year AUC value in TCGA was 0.662, 0.662, and 0.655, respectively; The 1, 2, and 3-year AUC value in GSE43131 was 0.724, 0.724, and 0.722, respectively. The proportion of infiltrated neutrophils in the high-risk group was higher than that in the low-risk group (p = 0.028), whereas that of resting NK cells (p = 0.002) was lower.

Conclusion

A novel prognostic risk model based on three m6A-related genes for LUSC was generated in this study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02509-1.

The MYEOV-MYC association promotes oncogenic miR-17/93-5p expression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy worldwide. As metastasis and malignant progression are primarily responsible for the poor clinical outcomes of PDAC, identifying key genes involved in these processes and the underlying molecular mechanisms of PDAC is vital. In this study, by analyzing TCGA PDAC data and matched GTEx data, we found that MYEOV expression is associated with poor survival in PDAC patients and higher in carcinoma tissues than in healthy tissues. Elevated levels of MYEOV led to enhanced cell proliferation, invasion and migration in vitro and in vivo. Transcriptome analysis results revealed that MYEOV mediates global alterations in gene expression profiles in PDAC cells. MiRNA-seq analysis showed that MYEOV regulates the expression levels of miR-17-5p and miR-93-5p, and its depletion resulted in reduced cell proliferation, invasion and migration, as observed in MYEOV-knockdown PDAC cells. These effects are likely due to the ability of MYEOV to regulate enrichment of the transcription factor MYC at the gene promoter regions of the two miRNAs. Furthermore, we identified a complex containing MYEOV and MYC in the nucleus, providing additional evidence for the association of MYEOV with MYC. Taken together, our results suggest that MYEOV promotes oncogenic miR-17/93-5p expression by associating with MYC, contributing to PDAC progression.

NET1 promotes HCC growth and metastasis in vitro and in vivo via activating the Akt signaling pathway

Neuroepithelial cell transforming gene 1 (NET1), a member of the guanine nucleotide exchange factor family, is involved in various cancers, including gastric cancer, breast cancer and glioma. However, the role of NET1 in hepatocellular carcinoma (HCC) remains largely uncovered. In this study, we found that NET1 expression was upregulated in HCC, and that upregulated NET1 expression was closely associated with poor prognosis and some clinical characteristics in HCC patients. Whilst forced expression of NET1 in HCC cells was observed to significantly promote cell growth and metastasis in vitro and in vivo; downregulation of NET1 was shown to exhibit an opposite inhibitory effect. RNA-seq analysis and gene set enrichment analysis demonstrated that knockdown of NET1 significantly suppressed the level of Akt phosphorylation level and the expression of Akt downstream genes in HCC cells. Moreover, MK2206, a potent Akt inhibitor was shown to block the NET1-induced effects in HCC. Taken together, this study demonstrated that, through the Akt signaling pathway, NET1 plays an oncogenic role in HCC progression and metastasis. Hence, NET1 may potentially be used as a potential therapeutic target and prognostic marker of HCC.

A 14-gene gemcitabine resistance gene signature is significantly associated with the prognosis of pancreatic cancer patients

To identify a gemcitabine resistance-associated gene signature for risk stratification and prognosis prediction in pancreatic cancer. Pearson correlation analysis was performed with gemcitabine half maximal inhibitory concentration (IC50) data of 17 primary pancreatic cancer lines from Genomics of Drug Sensitivity in Cancer (GDSC) and the transcriptomic data from GDSC and Broad Institute Cancer Cell Line Encyclopedia, followed by risk stratification, expression evaluation, overall survival (OS) prediction, clinical data validation and nomogram establishment. Our biomarker discovery effort identified a 14-gene signature, most of which featured differential expression. The 14-gene signature was associated with poor OS in E-MTAB-6134 (HR 2.37; 95% CI 1.75–3.2; p < 0.0001), pancreatic cancer-Canada (PACA-CA) (HR 1.76; 95% CI 1.31–2.37; p = 0.00015), and 4 other independent validation cohorts: pancreatic cancer-Australia (PACA-AU) (HR 1.9; 95% CI 1.38–2.61; p < 0.0001), The Cancer Genome Atlas (TCGA) (HR 1.73; 95% CI 1.11–2.69; p = 0.014), GSE85916 (HR 1.97; 95% CI 1.14–3.42; p = 0.014) and GSE62452 (HR 1.82; 95% CI 1.02–3.24; p = 0.039). Multivariate analysis revealed that the 14-gene risk score was an independent pancreatic cancer outcome predictor in E-MTAB-6134 (p < 0.001) and TCGA (p = 0.006). A nomogram including the 14-gene was established for eventual clinical translation. We identified a novel gemcitabine resistance gene signature for risk stratification and robust categorization of pancreatic cancer patients with poor prognosis.

Cdk1 phosphorylation negatively regulates the activity of Net1 towards RhoA during mitosis

The Neuroepithelial transforming gene 1 (Net1) is a RhoA subfamily guanine nucleotide exchange factor that is overexpressed in a number of cancers and contributes to cancer cell motility and proliferation. Net1 also plays a Rho GTPase independent role in mitotic progression, where it promotes centrosomal activation of Aurora A and Pak2, and aids in chromosome alignment during prometaphase. To understand regulatory mechanisms controlling the mitotic function of Net1, we examined whether it was phosphorylated by the mitotic kinase Cdk1. We observed that Cdk1 phosphorylated Net1 on multiple sites in its N-terminal regulatory domain and C-terminus in vitro. By raising phospho-specific antibodies to two of these sites, we also demonstrated that both endogenous and transfected Net1 were phosphorylated by Cdk1 in cells. Substitution of the major Cdk1 phosphorylation sites with aliphatic or acidic residues inhibited the interaction of Net1 with RhoA, and treatment of metaphase cells with a Cdk1 inhibitor increased Net1 activity. Cdk1 inhibition also increased Net1 localization to the plasma membrane and stimulated cortical F-actin accumulation. Moreover, Net1 overexpression caused spindle polarity defects that were reduced in frequency by acidic substitution of the major Cdk1 phosphorylation sites. These data indicate that Cdk1 phosphorylates Net1 during mitosis and suggest that this negatively regulates its ability to signal to RhoA and alter actin cytoskeletal organization.

Identification of "regulation of RhoA activity panel" as a prognostic and predictive biomarker for gastric cancer

RhoA is a member of the RHO family GTPases and is associated with essential functions in gastric cancer. In this study, we identified a gastric cancer biomarker, termed the “regulation of RhoA activity panel” (RRAP). Patients with gastric cancer from The Cancer Genome Atlas database were divided into training (N=160) and validation (N=155) cohorts. A cohort of 109 Chinese gastric cancer patients was utilized as an independent validation. Patients with mutated RRAP showed significantly better overall survival than patients with wild type RRAP. We also analyzed the association between RRAP and the migration capacity, immune-related signatures, and the tumor microenvironment. RRAP-mutant tumors had a significantly lower degree of lymph node metastasis and lower activities of migration-related pathways. These tumors also showed significantly increased immune cell infiltration and cytotoxic activity. Furthermore, two independent patient cohorts who received immune checkpoint blockade therapy were assessed for RRAP mutant status. As expected, for both immunotherapy cohorts, higher response rates to immune checkpoint blockade therapy were observed in patients with RRAP-mutant tumors than in patients with wild type RRAP tumors. Overall, this study indicates that the RRAP gene set is a potential biomarker for gastric cancer prognosis and therapeutic selection.

High expression of MYEOV reflects poor prognosis in non-small cell lung cancer

BACKGROUND

The myeloma overexpressed gene (MYEOV) plays a critical role in tumorigenesis in a variety of cancers. However, little is known of the prognosis and immune infiltration associated with MYEOV in non-small cell lung cancer (NSCLC).

METHODS

We used several databases (Oncomine, TCGA, and GEO) to analysis the expression, prognosis, and immune infiltration, associated with MYEOV in NSCLC. We also used RT-qPCR and immunohistochemistry to investigate the expression and prognosis of MYEOV in NSCLC.

RESULTS

Compared with normal tissues, high MYEOV expression in NSCLC was observed in Oncomine database, and was validated in the TCGA database. High MYEOV expression was significantly associated with different subtypes of NSCLC. Moreover, high MYEOV expression was closely related with a poorer overall survival in NSCLC in TCGA cohort, and was validated in GEO database. Simultaneously, high expression of MYEOV correlates with clinical relevance of NSCLC. Specifically, MYEOV expression was negatively correlated with infiltrating levels of tumor purity and B cells in LUAD. MYEOV expression was negatively correlated with infiltrating levels of tumor purity, and positively associated with CD8 + T cells, CD4 + T cells, dendritic cells, and neutrophils in LUSC. GSEA also revealed that high MYEOV expression were enriched in certain cancer-specific pathways. In addition, RT-qPCR and immunohistochemistry showed MYEOV expression was higher in NSCLC compared to the normal tissues. Finally, high MYEOV expression was closely related with poorer overall survival of NSCLC in an independent validation cohort.

CONCLUSION

Our analyses indicate that MYEOV can be used as a prognostic biomarker for determining prognosis and immune infiltration in NSCLC.

MYEOV increases HES1 expression and promotes pancreatic cancer progression by enhancing SOX9 transactivity

Emerging evidence indicates that myeloma overexpressed (MYEOV) is an oncogene and plays crucial roles in multiple human cancers. However, its roles in the development of pancreatic ductal adenocarcinoma (PDAC) remain elusive. Here, we provide evidence of essential roles of MYEOV in the development and progression of PDAC. In tumor specimens derived from pancreatic cancer patients, MYEOV was overexpressed and associated with poor prognosis. In addition, MYEOV expression in PDAC was upregulated through promoter hypomethylation. MYEOV depletion impaired metastatic ability and proliferation of PDAC cells both in vitro and in vivo, whereas its overexpression had the opposite effect. Mechanistic investigations revealed that MYEOV interacted with SRY-Box Transcription Factor 9 (SOX9), a well-known oncogenic transcription factor in PDAC. This interaction occurred mainly in the nuclei of PDAC cells and increased transcriptional activity of SOX9. Furthermore, MYEOV promoted the expression of Hairy and enhancer of split homolog-1 (HES1), a SOX9 target gene, by enhancing SOX9 DNA-binding ability to the HES1 enhancer without affecting the protein level and subcellular localization of SOX9. HES1 knockdown partly abrogated the oncogenic effect of MYEOV. Our findings suggest that MYEOV could be a potential prognostic biomarker and therapeutic target for PDAC.

Overexpression of MYEOV predicting poor prognosis in patients with pancreatic ductal adenocarcinoma

Myeloma Overexpressed (MYEOV) is closely related to cell growth and differentiation in many cancer types. However, the role of this protein-coding gene in pancreatic ductal adenocarcinoma (PDAC) has rarely been investigated. In this study, we demonstrated that MYEOV was higher expressed in tumor tissues compared with adjacent normal pancreas tissues (ANPTs) both in mRNA and protein levels. We also performed bioinformatic analysis and found high MYEOV expression was positively correlated with tumor differentiation (P = 0.004), lymph node metastasis (P = 0.016) and TNM stage (P = 0.001). Moreover, Kaplan-Meier and Cox proportional-hazards analyses indicated that high MYEOV expression was significantly associated with poor survival in patients with PDAC and that MYEOV was an independent prognostic factor for overall survival in patients with PDAC. Geneset Enrichment Analysis (GSEA) result showed that high expression of MYEOV facilitates glycolysis of tumor cells in PDAC and validated in cellular assays. In conclusion, our results suggest that MYEOV acts as an oncogene in PDAC and can therefore serve as a biomarker for the prognosis of patients with PDAC.

Neuroepithelial Cell Transforming Gene 1 Acts as an Oncogene and Is Mediated by miR-22 in Human Non-Small-Cell Lung Cancer

Abnormal expression of neuroepithelial cell transforming gene 1 (NET1) has been authenticated in many human cancers, including lung cancer. We have previously reported that NET1 functioned as an oncogene and promoted human non-small-cell lung cancer (NSCLC) growth and migration. However, the correlation between NET1 and its upstream miRNAs needed further illustration. Our present work demonstrated that miR-22 had a relatively low expression, and NET1 had a relatively high expression in both NSCLC samples and lung adenocarcinoma cell lines compared with corresponding normal controls. Moreover, miR-22 directly regulated NET1 and was verified to weaken cancer cell proliferation and migration, as well as enhance cell apoptosis by suppressing NET1. Furthermore, the inhibitory effect of miR-22 can be reversed via overexpressing NET1 using an ectopic expression vector in NSCLC cells. Our findings showed that miR-22/NET-1 axis may contribute to the inhibition of NSCLC growth and migration and represents a promising therapeutic target for NSCLC.

RHOA in Gastric Cancer: Functional Roles and Therapeutic Potential

The well-known signal mediator and small GTPase family member, RHOA, has now been associated with the progression of specific malignancies. In this review, we appraise the biomedical literature regarding the role of this enzyme in gastric cancer (GC) signaling, suggesting potential clinical significance. To that end, we examined RHOA activity, with regard to second-generation hallmarks of cancer, finding particular association with the hallmark "activation of invasion and metastasis." Moreover, an abundance of studies show RHOA association with Lauren classification diffuse subtype, in addition to poorly differentiated GC. With regard to therapeutic value, we found RHOA signaling to influence the activity of specific widely used chemotherapeutics, and its possible antagonism by various dietary constituents. We also review currently available targeted therapies for GC. The latter, however, showed a paucity of such agents, underscoring the urgent need for further investigation into treatments for this highly lethal malignancy.

Canine mammary tumour cells exposure to sevoflurane: effects on cell proliferation and neuroepithelial transforming gene 1 expression

OBJECTIVE

The influence of perioperative factors, such as anaesthetic and analgesic techniques, on metastatic spread following surgery for primary cancer removal is of growing interest. The present study investigated the effects of sevoflurane on canine mammary tumour cell proliferation (MTT colorimetric assay) and on the expression of neuroepithelial transforming gene 1 (NET1).

STUDY DESIGN

Prospective controlled in vitro trial.

STUDY MATERIAL

Primary (CIPp) and metastatic canine tubular adenocarcinoma (CIPm) cells.

METHODS

To perform MTT tests, cell lines were seeded at a density of 3000 cells per well and incubated with sevoflurane (1, 2.5 or 4 mM) or only with the culture medium (control). Sevoflurane was added to the cell cultures every hour to avoid changes in drug concentration. MTT assays were performed after 6 hours of exposure obtaining absolute values of absorbance. The RNA isolated from the lysates of the same cell lines underwent quantitative polymerase chain reaction to evaluate NET1 gene expression changes compared with controls. One- or two-way analysis of variance was used as appropriate (p < 0.05).

RESULTS

A significant increase in cell proliferation compared with controls was observed in CIPp treated with lower sevoflurane concentrations, whereas a significant decrease in cell proliferation was found in CIPm treated with all the sevoflurane concentrations. All CIPp treatments did not induce changes in gene expression compared with controls, whereas a significant increase in gene expression was observed in CIPm between controls and the higher sevoflurane concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Sevoflurane treatments modified the cell proliferation rate in both cell lines showing an increase or decrease when applied to CIPp or CIPm, respectively. Expression of the NET1 gene increased after treatment with sevoflurane 4 mM in metastatic cells. The role of sevoflurane on cancer recurrence should be further investigated.

MYEOV functions as an amplified competing endogenous RNA in promoting metastasis by activating TGF-β pathway in NSCLC

Non-small cell lung cancer (NSCLC) remains a major cause of death worldwide. As metastatic disease is primarily responsible for the poor clinical outcome of NSCLC, it is important to understand the process, and its underlying molecular mechanism as well, via which NSCLC cells disseminate. In this study, we identified a new competing endogenous RNA (ceRNA), namely, the MYEOV transcript, and found that it is upregulated in NSCLC and associated with a poor prognosis of the disease. We further uncovered that the MYEOV ceRNA plays a critical role in the invasion and metastasis of NSCLC cells. Intriguingly, the MYEOV ceRNA exerted its pro-metastatic function independent of its protein-coding capacity, but in a miR-30c-2-3p binding-dependent manner. Further experiments demonstrated that the MYEOV ceRNA sequestered miR-30c-2-3p from binding its targets TGFBR2 and USP15 mRNAs, which in turn leading to constitutive activation of TGF-β signaling and tumor progression in NSCLC. By identifying a new layer of regulatory modality for TGF-β signaling, our findings extend the current understanding on the molecular mechanism mediating NSCLC progression and highlight a potential role of MYEOV transcript to serve as the therapeutic target.

A structural study of the complex between neuroepithelial cell transforming gene 1 (Net1) and RhoA reveals a potential anticancer drug hot spot

The GTPase RhoA is a major player in many different regulatory pathways. RhoA catalyzes GTP hydrolysis, and its catalysis is accelerated when RhoA forms heterodimers with proteins of the guanine nucleotide exchange factor (GEF) family. Neuroepithelial cell transforming gene 1 (Net1) is a RhoA-interacting GEF implicated in cancer, but the structural features supporting the RhoA/Net1 interaction are unknown. Taking advantage of a simple production and purification process, here we solved the structure of a RhoA/Net1 heterodimer with X-ray crystallography at 2-Å resolution. Using a panel of several techniques, including molecular dynamics simulations, we characterized the RhoA/Net1 interface. Moreover, deploying an extremely simple peptide-based scanning approach, we found that short peptides (penta- to nonapeptides) derived from the protein/protein interaction region of RhoA could disrupt the RhoA/Net1 interaction and thereby diminish the rate of nucleotide exchange. The most inhibitory peptide, EVKHF, spanning residues 102-106 in the RhoA sequence, displayed an IC₅₀ of ∼100 μm without further modifications. The peptides identified here could be useful in further investigations of the RhoA/Net1 interaction region. We propose that our structural and functional insights might inform chemical approaches for transforming the pentapeptide into an optimized pseudopeptide that antagonizes Net1-mediated RhoA activation with therapeutic anticancer potential.

Decreased TSPAN1 promotes prostate cancer progression and is a marker for early biochemical recurrence after radical prostatectomy

Patients with prostate cancer (PCa) have a variable prognosis. It is challenging to recognize the progressive disease. In this study, we focused on TSPAN1, a new member of the tetraspanin family. Its expression was decreased in progressive PCa and was an independent prognosis factor of biochemical recurrence after radical prostatectomy. In vitro, knockdown and overexpression of TSPAN1 in PCa cell lines showed that TSPAN1 could inhibit cell proliferation and migration. TSPAN1 was positive related to PTEN in both clinical specimen and mouse models. The combination of these two markers could increase their prognosis value especially in low risk patients. In vitro TSPAN1 knockdown resulted in increased Akt phosphorylation and caused evident cell cycle transition from G1 to S phase. Our data suggests that TSPAN1 is a valuable marker to recognize more progressive PCa.

Suppression of TSPAN1 by RNA Interference Inhibits Proliferation and Invasion of Colon Cancer Cells in Vitro

Aims and background

To investigate effect of TSPAN1 downregulation by RNA interference (RNAi) on proliferation and invasion of human colon cancer cells in vitro.

Methods and study design

RNAi was performed using the vector (pU6H1-GFP)-based small-interfering RNA (siRNA) plasmid gene silencing system to specifically knock down TSPAN1 expression in a colon cancer cell line, HCT-8. The expression of TSPAN1 mRNA was detected by reverse-transcription polymerase chain reaction. TSPAN1 protein expression was observed using Western blots and immunofluorescent microscopy. Cell proliferation and cell cycle assay were measured using methyl thiazolyl tetrazolium (MTT) and flow cytometry, respectively. The invasive ability of HCT-8 cells was examined using a duel culture chamber separated by polycarbonate membranes coated with Matrigel (8.0-μm pore size).

Results

After transfection with the TSPAN1 siRNA plasmid, TSPAN1 mRNA and protein expression was significantly decreased. The decrease in mRNA and protein was associated with a significant decrease in TSPAN1 fluorescent staining and a decrease in cell proliferation due to cell cycle arrest in the G1/G0 phase. A significant decrease in the number of invading HCT-8 cells was associated with these changes.

Conclusion

RNAi-mediated downregulation of TSPAN1 expression significantly inhibits the proliferation and invasion of colon cancer cells in vitro. This finding suggests that TSPAN1 plays an important role in colon cancer progression, and RNAi targeting of TSPAN1 may be a potential therapeutic strategy for the treatment of colon cancer. Free full text available at www.tumorionline.it

The guanine nucleotide exchange factor Net1 facilitates the specification of dorsal cell fates in zebrafish embryos by promoting maternal β-catenin activation

Wnt/β-catenin signaling is essential for the initiation of dorsal-ventral patterning during vertebrate embryogenesis. Maternal β-catenin accumulates in dorsal marginal nuclei during cleavage stages, but its critical target genes essential for dorsalization are silent until mid-blastula transition (MBT). Here, we find that zebrafish net1, a guanine nucleotide exchange factor, is specifically expressed in dorsal marginal blastomeres after MBT, and acts as a zygotic factor to promote the specification of dorsal cell fates. Loss- and gain-of-function experiments show that the GEF activity of Net1 is required for the activation of Wnt/β-catenin signaling in zebrafish embryos and mammalian cells. Net1 dissociates and activates PAK1 dimers, and PAK1 kinase activation causes phosphorylation of S675 of β-catenin after MBT, which ultimately leads to the transcription of downstream target genes. In summary, our results reveal that Net1-regulated β-catenin activation plays a crucial role in the dorsal axis formation during zebrafish development.

Adaptive Evolution Coupled with Retrotransposon Exaptation Allowed for the Generation of a Human-Protein-Specific Coding Gene That Promotes Cancer Cell Proliferation and Metastasis in Both Haematological Malignancies and Solid Tumours: The Extraordinary Case of MYEOV Gene

The incidence of cancer in human is high as compared to chimpanzee. However previous analysis has documented that numerous human cancer-related genes are highly conserved in chimpanzee. Till date whether human genome includes species-specific cancer-related genes that could potentially contribute to a higher cancer susceptibility remains obscure. This study focuses on MYEOV, an oncogene encoding for two protein isoforms, reported as causally involved in promoting cancer cell proliferation and metastasis in both haematological malignancies and solid tumours. First we document, via stringent in silico analysis, that MYEOV arose de novo in Catarrhini. We show that MYEOV short-isoform start codon was evolutionarily acquired after Catarrhini/Platyrrhini divergence. Throughout the course of Catarrhini evolution MYEOV acquired a gradually elongated translatable open reading frame (ORF), a gradually shortened translation-regulatory upstream ORF, and alternatively spliced mRNA variants. A point mutation introduced in human allowed for the acquisition of MYEOV long-isoform start codon. Second, we demonstrate the precious impact of exonized transposable elements on the creation of MYEOV gene structure. Third, we highlight that the initial part of MYEOV long-isoform coding DNA sequence was under positive selection pressure during Catarrhini evolution. MYEOV represents a Primate Orphan Gene that acquired, via ORF expansion, a human-protein-specific coding potential.

Neuroepithelial transforming gene 1 functions as a potential prognostic marker for patients with non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common histological cancer sub‑type worldwide. Neuroepithelial transforming gene 1 (Net-1), a Ras homolog family member A-specific guanine nucleotide exchange factor, has been shown to be upregulated in several human cancer types. However, the clinical significance of Net‑1 expression in NSCLC has remained elusive. The present study assessed Net‑1 mRNA and protein levels by reverse-transcription quantitative polymerase chain reaction and western blot analysis of 64 cases of NSCLC as well as their adjacent normal tissues. Furthermore, Net‑1 protein expression in tumor tissues derived from clinically annotated NSCLC cases at stages I‑III was detected by immunohistochemical staining. The results showed that Net‑1 mRNA and protein levels in NSCLC tissues were significantly elevated compared with those in their corresponding non‑tumor tissues. In addition, Net‑1 expression was strongly associated with the patients' pathological characteristics, including clinical stage, lymph node metastasis, distant metastasis and differentiation degree (P<0.05). In conclusion, the results of the present study suggested that Net‑1 expression has a significant role in the tumorigenesis of distinct histotypes and sub‑types of NSCLC, and may therefore be utilized as a biomarker as well as an important therapeutic target in NSCLC.

Tetraspanin 1 is involved in survival, proliferation and carcinogenesis of pancreatic cancer

Pancreatic cancer (PCC) is one of the most difficult cancers to treat and the 10th leading cause of cancer-related death in worldwide. Studies have demonstrated that the tetraspanin 1 (Tspan1) is overexpressed in various cancers and may be a potential therapeutic strategy for the treatment of different cancers. However, the possible role of Tspan1 in PCC is still unknown. In the present study, our data revealed that the increased Tspan1 in PCC tissues was associated with the clinicopathological features and survival rate of PCC patient. We also investigated the effects of Tspan1 gene knockdown on the biological behavior of human PCC. The expression of Tspan1 (detected by immunohistochemistry, qRT-PCR and western blot analysis) derived from human PCC tissues and cell lines (AsPC-1 and PANC-1), were significantly elevated compared with those of the control (P<0.05). Transfection with siRNA-targeting Tspan1 significantly decreased proliferation, increased the apoptosis and reduced migration and invasion of AsPC-1 and PANC-1 cells. The present study demonstrated that Tspan1 plays an important role in PCC carcinogenic progression, including migration and invasion. The siRNA targeting of Tspan1 may be a potential therapeutic strategy for the treatment of PCC.

The RhoGEF Net1 is required for normal mammary gland development

Neuroepithelial transforming gene 1 (Net1) is a RhoA subfamily-specific guanine nucleotide exchange factor that is overexpressed in human breast cancer and is required for breast cancer cell migration and invasion. However, the role of Net1 in normal mammary gland development or function has never been assessed. To understand the role of Net1 in the mammary gland, we have created a conditional Net1 knockout mouse model. Whole-body deletion of Net1 results in delayed mammary gland development during puberty characterized by slowed of ductal extension and reduced ductal branching. Epithelial cells within the developing ducts show reduced proliferation that is accompanied by diminished estrogen receptor-α expression and activity. Net1-deficient mammary glands also exhibit reduced phosphorylation of regulatory subunits of myosin light chain and myosin light-chain phosphatase, indicating that RhoA-dependent actomyosin contraction is compromised. Net1 deficiency also leads to disorganization of myoepithelial and ductal epithelial cells and increased periductal collagen deposition. Mammary epithelial cell transplantation experiments indicate that reduced ductal branching and disorganization are cell autonomous. These data identify for the first time a role for NET1 in vivo and indicate that NET1 expression is essential for the proliferation and differentiation of mammary epithelial cells in the developing mammary gland.

Acetylation of the RhoA GEF Net1A controls its subcellular localization and activity

Net1 isoform A (Net1A) is a RhoA GEF that is required for cell motility and invasion in multiple cancers. Nuclear localization of Net1A negatively regulates its activity, and we have recently shown that Rac1 stimulates Net1A relocalization to the plasma membrane to promote RhoA activation and cytoskeletal reorganization. However, mechanisms controlling the subcellular localization of Net1A are not well understood. Here, we show that Net1A contains two nuclear localization signal (NLS) sequences within its N-terminus and that residues surrounding the second NLS sequence are acetylated. Treatment of cells with deacetylase inhibitors or expression of active Rac1 promotes Net1A acetylation. Deacetylase inhibition is sufficient for Net1A relocalization outside the nucleus, and replacement of the N-terminal acetylation sites with arginine residues prevents cytoplasmic accumulation of Net1A caused by deacetylase inhibition or EGF stimulation. By contrast, replacement of these sites with glutamine residues is sufficient for Net1A relocalization, RhoA activation and downstream signaling. Moreover, the N-terminal acetylation sites are required for rescue of F-actin accumulation and focal adhesion maturation in Net1 knockout MEFs. These data indicate that Net1A acetylation regulates its subcellular localization to impact on RhoA activity and actin cytoskeletal organization.

I'm coming to GEF you: Regulation of RhoGEFs during cell migration

Cell migration is a highly regulated multistep process that requires the coordinated regulation of cell adhesion, protrusion, and contraction. These processes require numerous protein–protein interactions and the activation of specific signaling pathways. The Rho family of GTPases plays a key role in virtually every aspect of the cell migration cycle. The activation of Rho GTPases is mediated by a large and diverse family of proteins; the guanine nucleotide exchange factors (RhoGEFs). GEFs work immediately upstream of Rho proteins to provide a direct link between Rho activation and cell–surface receptors for various cytokines, growth factors, adhesion molecules, and G protein-coupled receptors. The regulated targeting and activation of RhoGEFs is essential to coordinate the migratory process. In this review, we summarize the recent advances in our understanding of the role of RhoGEFs in the regulation of cell migration.

Controlling the switches: Rho GTPase regulation during animal cell mitosis

Animal cell division is a fundamental process that requires complex changes in cytoskeletal organization and function. Aberrant cell division often has disastrous consequences for the cell and can lead to cell senescence, neoplastic transformation or death. As important regulators of the actin cytoskeleton, Rho GTPases play major roles in regulating many aspects of mitosis and cytokinesis. These include centrosome duplication and separation, generation of cortical rigidity, microtubule-kinetochore stabilization, cleavage furrow formation, contractile ring formation and constriction, and abscission. The ability of Rho proteins to function as regulators of cell division depends on their ability to cycle between their active, GTP-bound and inactive, GDP-bound states. However, Rho proteins are inherently inefficient at fulfilling this cycle and require the actions of regulatory proteins that enhance GTP binding (RhoGEFs), stimulate GTPase activity (RhoGAPs), and sequester inactive Rho proteins in the cytosol (RhoGDIs). The roles of these regulatory proteins in controlling cell division are an area of active investigation. In this review we will delineate the current state of knowledge of how specific RhoGEFs, RhoGAPs and RhoGDIs control mitosis and cytokinesis, and highlight the mechanisms by which their functions are controlled.

Restoration of MAGI-1 expression in human papillomavirus-positive tumor cells induces cell growth arrest and apoptosis

The cancer-causing high-risk human papillomavirus (HPV) E6 oncoproteins target a number of cellular proteins that contain PDZ domains. However, the role of many of these interactions in either the HPV life cycle or in HPV-induced malignancy remains to be defined. Previous studies had shown that MAGI-1 was one of the most strongly bound PDZ domain-containing substrates of E6, and one consequence of this interaction appeared to facilitate the perturbation of tight junctions (TJs) by E6. In this study, we describe the generation of a mutation, K499E, within the MAGI-1 PDZ1 domain, which is resistant to E6 targeting. This mutant allows restoration of MAGI-1 expression in HPV-positive cells and defines additional activities of MAGI-1 that are overcome as a consequence of the association with E6. The reexpression of MAGI-1 in HPV-positive cells results in an increased recruitment of ZO-1 and PAR3 to sites of cell-cell contact, repression of cell proliferation, and induction of apoptosis. While the K499E mutation does not significantly affect these intrinsic activities of MAGI-1 in HPV-negative cells, its resistance to E6 targeting in an HPV-positive setting results in more cells expressing the mutant MAGI-1 than the wild-type MAGI-1, with a corresponding increase in TJ assembly, induction of apoptosis, and reduction in cell proliferation. These studies provide compelling evidence of a direct role for the perturbation of MAGI-1 function by E6 in the HPV life cycle and in HPV-induced malignancy.

IMPORTANCE

It is clear that the targeting of PDZ-containing substrates by E6 is important for the normal viral life cycle and for the progression to malignancy. Nevertheless, which of these PDZ domain-containing proteins is relevant for HPV pathology is still elusive. In a previous study, we provided evidence that MAGI-1 is a sensitive proteolytic substrate for both the HPV-16 and HPV-18 E6 oncoproteins; however, the biological consequences associated with loss of MAGI-1 expression in HPV-positive cervical cancer cells are still poorly understood. Using a mutant MAGI-1, resistant to E6-mediated degradation, we show that its expression in cervical cancer cells promotes membrane recruitment of the tight junction-associated proteins ZO-1 and PAR3, represses cell proliferation, and promotes apoptosis. These findings suggest that E6-mediated inhibition of MAGI-1 function contributes to HPV pathology by perturbing tight junction assembly with concomitant stimulation of proliferation and inhibition of apoptosis.

Prognostic significance of neuroepithelial transforming gene 1 in adenocarcinoma of the oesophagogastric junction

Background

Neuroepithelial transforming gene 1 (NET1) mediates tumour invasion and metastasis in a number of cancers, including gastric adenocarcinoma. It is an indicator of poor prognosis in breast cancer and glioma. This study examined NET1 expression and its prognostic significance in patients with adenocarcinoma of the oesophagogastric junction (AOG).

Methods

NET1 expression was measured by immunohistochemistry in a tissue microarray, constructed from biobanked tissue collected over a 10-year interval, and linked to a prospectively maintained clinical database.

Results

Using the Siewert classification for AOG, type I tumours expressed significantly higher levels of NET1, with lowest expression in type III and intermediate levels in type II (P = 0·001). In patients with AOG type III, NET1-positive patients were more likely to be female (P = 0·043), have advanced stage cancer (P = 0.035), had a higher number of transmural cancers (P = 0·006) and had a significantly higher median number of positive lymph nodes (P = 0·029). In this subgroup, NET1-positive patients had worse median overall (15 versus 23 months; P = 0·025) and disease-free (11 versus 36 per cent; P = 0·025) survival compared with NET1-negative patients.

Conclusion

Although existing data show differences in clinical and prognostic indices across AOG subtypes, there are no studies showing differences in tumour biology. These data suggest NET1, a known mediator of an aggressive tumour phenotype in a number of gastrointestinal cancers, is expressed differentially across AOG subtypes and may be of prognostic significance in the clinical management of this condition.

Divergent transcription: a driving force for new gene origination?

The mammalian genome is extensively transcribed, a large fraction of which is divergent transcription from promoters and enhancers that is tightly coupled with active gene transcription. Here, we propose that divergent transcription may shape the evolution of the genome by new gene origination.

Expression and function of NET-1 in human skin squamous cell carcinoma

To evaluate the clinicopathological significance of NET-1 in human skin squamous cell carcinoma (SSCC). The expression of NET-1 and Ki67 protein was detected using immunostaining from 60 SSCC cases, 50 SIN samples and ten normal skin tissues. The vectors expressing NET-1, siRNA NET-1 and shRNA NET-1 were constructed, as well as negative controls (target-off). In transfected A431 cells, the expression of NET-1 was detected by qRT-PCR, Western blot and immunofluorescence staining; the proliferation and migration of cells was evaluated by MTT, flow cytometry, wound healing and transwell chamber assays. The stable cell lines transfected with shRNANET-1 was inoculated in nude mice for in vivo study. (1) The levels of NET-1 were significantly higher in SSCC (96.67 %) and SIN III (93.75 %) than that in SIN I and II (41.18 %), (P < 0.05). NET-1 expression was significantly enhanced in spindle-cell SSCC (75 %) versus other histological types (P < 0.05). (2) The expression of NET-1 in A431 cells transfected with siRNANET-1 or shRNANET-1 was significantly decreased; the proliferation and migration of these cells were obviously inhibited as compared to controls (P < 0.05). (3) The growth of subcutaneous tumors was significantly inhibited associated with reduction in the expression of NET-1 vs. the negative control or untreated group (P < 0.05). The overexpression of NET-1 in tumor cells may be closely related to the malignant phenotype of SSCC. NET-1 RNAi used in this study can specifically and effectively downregulate NET-1 gene expression; thus SSCC proliferation, invasion and tumor growth were attenuated. NET-1 might be one of the potential targets for SSCC therapy.

Rho GTPase-independent regulation of mitotic progression by the RhoGEF Net1

Neuroepithelial transforming gene 1 (Net1) is a RhoA-subfamily-specific guanine nucleotide exchange factor that is overexpressed in multiple human cancers and is required for proliferation. Molecular mechanisms underlying its role in cell proliferation are unknown. Here we show that overexpression or knockdown of Net1 causes mitotic defects. Net1 is required for chromosome congression during metaphase and generation of stable kinetochore microtubule attachments. Accordingly, inhibition of Net1 expression results in spindle assembly checkpoint activation. The ability of Net1 to control mitosis is independent of RhoA or RhoB activation, as knockdown of either GTPase does not phenocopy effects of Net1 knockdown on nuclear morphology, and effects of Net1 knockdown are effectively rescued by expression of catalytically inactive Net1. We also observe that Net1 expression is required for centrosomal activation of p21-activated kinase and its downstream kinase Aurora A, which are critical regulators of centrosome maturation and spindle assembly. These results identify Net1 as a novel regulator of mitosis and indicate that altered expression of Net1, as occurs in human cancers, may adversely affect genomic stability.

Expression of neuroepithelial transforming gene 1 is enhanced in oesophageal cancer and mediates an invasive tumour cell phenotype

INTRODUCTION

Neuroepithelial Transforming Gene 1 (NET1) is a well characterised oncoprotein and a proven marker of an aggressive phenotype in a number of cancers, including gastric adenocarcinoma. We aimed to investigate whether NET1 plays a functional role in oesophageal cancer (OAC) and its pre-malignant phenotype Barrett's oesophagus.

METHODS

Baseline NET1 mRNA levels were determined by qPCR across a panel of six cell lines, including normal oesophageal, Barrett's and OAC derived cells. Quantification of NET1 protein in OAC cells was performed using Western blot and immunofluorescence. NET1 expression was modulated by treating with lysophosphatidic acid (LPA) and NET1-specific siRNA. The functional effects of NET1 knockdown were assessed in vitro using proliferation, migration and invasion assays.

RESULTS

NET1 expression was increased in Barrett's and in OAC-derived cells in comparison to normal oesophageal cells. The highest expression was observed in OE33 a Barrett's-related OAC cell line. NET1 protein and mRNA expression was enhanced by LPA treatment in OAC and furthermore LPA treatment caused increased proliferation, migration and invasion in a NET1-dependent manner. NET1 knockdown resulted in reduced OAC cell proliferation and invasion.

CONCLUSIONS

As found in other malignancies, NET1 expression is elevated in OAC and its pre-malignant phenotype, Barrett's oesophagus. NET1 promotes OAC cell invasion and proliferation and it mediates LPA-induced OAC cell migration.

Timing is everything: Rac1 controls Net1A localization to regulate cell adhesion

Cell adhesion to the extracellular matrix elicits a temporal reorganization of the actin cytoskeleton that is regulated first by Rac1 and later by RhoA. The signaling mechanisms controlling late stage RhoA activation are incompletely understood. Net1A is a RhoA/RhoB-specific guanine nucleotide exchange factor that is required for cancer cell motility. The ability of Net1A to stimulate RhoA activation is negatively regulated by nuclear sequestration. However, mechanisms controlling the plasma membrane localization of Net1A had not previously been reported. Recently we have shown that Rac1 activation stimulates plasma membrane relocalization and activation of Net1A. Net1A relocalization is independent of its catalytic activity and does not require its C-terminal pleckstrin homology or PDZ interacting domains. Rac1 activation during cell adhesion stimulates a transient relocalization of Net1A that is terminated by proteasomal degradation of Net1A. Importantly, plasma membrane localization of Net1A is required for efficient myosin light chain phosphorylation, focal adhesion maturation, and cell spreading. These data show for the first time a physiological mechanism controlling Net1A relocalization from the nucleus. They also demonstrate a previously unrecognized role for Net1A in controlling actomyosin contractility and focal adhesion dynamics during cell adhesion.

Regulation of focal adhesion kinase activation, breast cancer cell motility, and amoeboid invasion by the RhoA guanine nucleotide exchange factor Net1

Net1 is a RhoA guanine nucleotide exchange factor (GEF) that is overexpressed in a subset of human cancers and contributes to cancer cell motility and invasion in vitro. However, the molecular mechanism accounting for its role in cell motility and invasion has not been described. In the present work, we show that expression of both Net1 isoforms in breast cancer cells is required for efficient cell motility. Although loss of Net1 isoform expression only partially blocks RhoA activation, it inhibits lysophosphatidic acid (LPA)-stimulated migration as efficiently as knockdown of RhoA itself. However, we demonstrate that the Net1A isoform predominantly controls myosin light-chain phosphorylation and is required for trailing edge retraction during migration. Net1A interacts with focal adhesion kinase (FAK), localizes to focal adhesions, and is necessary for FAK activation and focal adhesion maturation during cell spreading. Net1A expression is also required for efficient invasion through a Matrigel matrix. Analysis of invading cells demonstrates that Net1A is required for amoeboid invasion, and loss of Net1A expression causes cells to shift to a mesenchymal phenotype characterized by high β1-integrin activity and membrane type 1 matrix metalloproteinase (MT1-MMP) expression. These results demonstrate a previously unrecognized role for the Net1A isoform in controlling FAK activation during planar cell movement and amoeboid motility during extracellular matrix (ECM) invasion.

Rac1 controls the subcellular localization of the Rho guanine nucleotide exchange factor Net1A to regulate focal adhesion formation and cell spreading

RhoA is overexpressed in human cancer and contributes to aberrant cell motility and metastatic progression; however, regulatory mechanisms controlling RhoA activity in cancer are poorly understood. Neuroepithelial transforming gene 1 (Net1) is a RhoA guanine nucleotide exchange factor that is overexpressed in human cancer. It encodes two isoforms, Net1 and Net1A, which cycle between the nucleus and plasma membrane. Net1 proteins must leave the nucleus to activate RhoA, but mechanisms controlling the extranuclear localization of Net1 isoforms have not been described. Here, we show that Rac1 activation causes relocalization of Net1 isoforms outside the nucleus and stimulates Net1A catalytic activity. These effects do not require Net1A catalytic activity, its pleckstrin homology domain, or its regulatory C terminus. We also show that Rac1 activation protects Net1A from proteasome-mediated degradation. Replating cells on collagen stimulates endogenous Rac1 to relocalize Net1A, and inhibition of proteasome activity extends the duration and magnitude of Net1A relocalization. Importantly, we demonstrate that Net1A, but not Net1, is required for cell spreading on collagen, myosin light chain phosphorylation, and focal adhesion maturation. These data identify the first physiological mechanism controlling the extranuclear localization of Net1 isoforms. They also demonstrate a previously unrecognized role for Net1A in regulating cell adhesion.

Neuroepithelial transforming gene 1 (Net1) binds to caspase activation and recruitment domain (CARD)- and membrane-associated guanylate kinase-like domain-containing (CARMA) proteins and regulates nuclear factor κB activation

The molecular complexes containing CARMA proteins have been recently identified as a key components in the signal transduction pathways that regulate activation of nuclear factor κB (NF-κB) transcription factor. Here, we used immunoprecipitation coupled with mass spectrometry to identify cellular binding partners of CARMA proteins. Our data indicate that the Rho guanine nucleotide exchange factor Net1 binds to CARMA1 and CARMA3 in resting and activated cells. Net1 expression induces NF-κB activation and cooperates with BCL10 and CARMA proteins in inducing NF-κB activity. Conversely, shRNA-mediated abrogation of Net1 results in impaired NF-κB activation following stimuli that require correct CARMA-BCL10-MALT1 complex formation and functioning. Microarray expression data are consistent with a positive role for Net1 on NF-κB activation. Thus, this study identifies Net1 as a CARMA-interacting molecule and brings important information on the molecular mechanisms that control NF-κB transcriptional activity.

A functional and transcriptomic analysis of NET1 bioactivity in gastric cancer

BACKGROUND

NET1, a RhoA guanine exchange factor, is up-regulated in gastric cancer (GC) tissue and drives the invasive phenotype of this disease. In this study, we aimed to determine the role of NET1 in GC by monitoring the proliferation, motility and invasion of GC cells in which NET1 has been stably knocked down. Additionally, we aimed to determine NET1-dependent transcriptomic events that occur in GC.

METHODS

An in vitro model of stable knockdown of NET1 was achieved in AGS human gastric adenocarcinoma cells via lentiviral mediated transduction of short-hairpin (sh) RNA targeting NET1. Knockdown was assessed using quantitative PCR. Cell proliferation was assessed using an MTS assay and cell migration was assessed using a wound healing scratch assay. Cell invasion was assessed using a transwell matrigel invasion assay. Gene expression profiles were examined using affymetrix oligonucleotide U133A expression arrays. A student's t test was used to determine changes of statistical significance.

RESULTS

GC cells were transduced with NET1 shRNA resulting in a 97% reduction in NET1 mRNA (p < 0.0001). NET1 knockdown significantly reduced the invasion and migration of GC cells by 94% (p < 0.05) and 24% (p < 0.001) respectively, while cell proliferation was not significantly altered following NET1 knockdown. Microarray analysis was performed on non-target and knockdown cell lines, treated with and without 10 μM lysophosphatidic acid (LPA) allowing us to identify NET1-dependent, LPA-dependent and NET1-mediated LPA-induced gene transcription. Differential gene expression was confirmed by quantitative PCR. Shortlisted NET1-dependent genes included STAT1, TSPAN1, TGFBi and CCL5 all of which were downregulatd upon NET1 downregulation. Shortlisted LPA-dependent genes included EGFR and PPARD where EGFR was upregulated and PPARD was downregulated upon LPA stimulation. Shortlisted NET1 and LPA dependent genes included IGFR1 and PIP5K3. These LPA induced genes were downregulated in NET1 knockdown cells.

CONCLUSIONS

NET1 plays an important role in GC cell migration and invasion, key aspects of GC progression. Furthermore, the gene expression profile further elucidates the molecular mechanisms underpinning NET1-mediated aggressive GC cell behaviour.

Prognostic significance of neuroepithelial transforming protein 1 in hepatocellular carcinoma

OBJECTIVE

Recent works have demonstrated that neuroepithelial transforming protein 1 (NET-1) gene expression is associated with proliferation, metastasis, and clinical stages of human hepatocellular carcinoma (HCC). To investigate its prognostic significance in HCC, which currently is unknown, the authors examined the correlation between NET-1 expression and prognosis in patients with HCC.

METHODS

Immunohistochemical staining was used to determine NET-1 expression level in 368 paired HCC and normal liver tissue (NLT) specimens. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognosis of HCC.

RESULTS

Among 368 specimens of HCC, the positive rate of NET-1 protein expression in HCC tissues was 86.7% (319/368), and the increased NET-1 expression was correlated significantly with high Edmondson-Steiner grade (p = .02) and TNM stage (p = .01). The expression level of NET-1 in HCC tissues was associated with intrahepatic metastasis (p = .008) and portal vein infiltration (p = .007). HCC patients with the moderate-strong NET-1 positive expression had either poorer disease-free survival or poorer overall survival than patients with negative-low positive NET-1 expression (p = .001 and .002, respectively). A multivariate Cox regression analysis revealed that NET-1 protein expression (relative risk 5.8; p = .01) was an independent prognostic factor for patients with HCC.

CONCLUSION

Taken together, our study suggests for the first time that NET-1 status may be a new predictor of survival for HCC patients and provides the rationale for developing a novel therapy of targeting NET-1 against this fatal malignancy.

Clinicopathological significance of expression of Tspan-1, Jab1 and p27 in human hepatocellular carcinoma

The aim of this study was to investigate the expression of Tspan-1, Jab1 and p27 in human hepatocellular carcinoma (HCC) and their clinicopathological significance. The expression of Tspan-1, Jab1 and p27 was detected in HCC tissues, the tissues around cancer (76 cases), and the normal tissues around the liver hemangiomas (10 cases). The overexpression of Tspan-1 and Jab1 was found in HCC tissues, positively correlated with clinical stage and negatively correlated with survival rate. The expression of p27 was found inversely linked to which of Tspan-1 and Jab1. In conclusion, the expression of Tspan-1, Jab1 and p27 is significantly associated with development of HCC. Overexpression of Tspan-1 and Jab1 suggests poor prognosis but overexpression of p27 may expect good prognosis for patients with HCC.

Estrogen regulation and physiopathologic significance of alternative promoters in breast cancer

Alternative promoters (AP) occur in >30% protein-coding genes and contribute to proteome diversity. However, large-scale analyses of AP regulation are lacking, and little is known about their potential physiopathologic significance. To better understand the transcriptomic effect of estrogens, which play a major role in breast cancer, we analyzed gene and AP regulation by estradiol in MCF7 cells using pan-genomic exon arrays. We thereby identified novel estrogen-regulated genes (ERG) and determined the regulation of AP-encoded transcripts in 150 regulated genes. In <30% cases, APs were regulated in a similar manner by estradiol, whereas in >70% cases, they were regulated differentially. The patterns of AP regulation correlated with the patterns of estrogen receptor alpha (ERalpha) and CCCTC-binding factor (CTCF) binding sites at regulated gene loci. Interestingly, among genes with differentially regulated (DR) APs, we identified cases where estradiol regulated APs in an opposite manner, sometimes without affecting global gene expression levels. This promoter switch was mediated by the DDX5/DDX17 family of ERalpha coregulators. Finally, genes with DR promoters were preferentially involved in specific processes (e.g., cell structure and motility, and cell cycle). We show, in particular, that isoforms encoded by the NET1 gene APs, which are inversely regulated by estradiol, play distinct roles in cell adhesion and cell cycle regulation and that their expression is differentially associated with prognosis in ER(+) breast cancer. Altogether, this study identifies the patterns of AP regulation in ERGs and shows the contribution of AP-encoded isoforms to the estradiol-regulated transcriptome as well as their physiopathologic significance in breast cancer.

Over-expression of neuroepithelial-transforming protein 1 confers poor prognosis of patients with gliomas

OBJECTIVE

Neuroepithelial-transforming protein 1 is a member of the guanine nucleotide exchange factor family, a group of proteins which are known to activate and thereby regulate Rho family members. Deregulation of neuroepithelial-transforming protein 1 expression has been found in certain types of human tumors. To investigate its prognostic value in human gliomas, which is currently unknown, we examined the correlation between neuroepithelial-transforming protein 1 expression and prognosis in patients with gliomas.

METHODS

Immunohistochemical staining was performed to detect neuroepithelial-transforming protein 1 expression patterns in the biopsies from 96 patients with primary gliomas. Kaplan-Meier survival and Cox's regression analyses were performed to evaluate the prognosis of patients.

RESULTS

Immunohistochemical analysis with anti-neuroepithelial-transforming protein 1 antibody revealed that neuroepithelial-transforming protein 1 was significantly associated with the Karnofsky performance scale score and World Health Organization grades of patients with gliomas. Especially, the positive expression rates of neuroepithelial-transforming protein 1 were significantly higher in patients with higher grade (P = 0.001) and lower Karnofsky's performance scale score (P = 0.005). The median survival of patients with high neuroepithelial-transforming protein 1 expression was significantly shorter than that with low expression and without expression (316, 892 and 1180 days, respectively). Cox's multifactor analysis showed that the Karnofsky performance scale (P = 0.01), World Health Organization grade (P = 0.008) and neuroepithelial-transforming protein 1 (P = 0.006) were independent prognosis factors for human glioma.

CONCLUSIONS

Taken together, our study indicates for the first time that neuroepithelial-transforming protein 1 status may be a highly sensitive marker for glioma prognosis and suggest that the expression patterns of neuroepithelial-transforming protein 1 might be a potent tool for predicting the clinical prognosis of glioma patients.

Characterization of tissue-specific mbu-3 gene expression in the mouse central nervous system

Mbu-3 is a novel mouse brain unigene that was identified by digital differential display. In this study, expression of the gene was chased through developmental stages and the protein product was identified in the brain. The cDNA sequence was 3,995-bp long and contained an ORF of 745 AA. Database searches revealed that the chicken SST273 gene containing LRR- and Ig-domain was an mbu-3 orthologue. Tissue specificity for the gene was examined in embryos and in brains at post-natal and adult stages. During the embryonic stages, mbu-3 was localized to the central nervous system in the brain and spinal cord. In the early post-natal stages, the gene was evenly expressed in the brain. However, with aging, expression was confined to specific regions, particularly the hippocampus. The protein was approximately 95 kDa as determined by Western blot analysis of brain extracts.

Characterization of mouse synaptic vesicle-2-associated protein (Msvop) specifically expressed in the mouse central nervous system

In this study, we identified and characterized a mouse brain-enriched unigene (msvop) after performing digital differential display. Msvop was the mouse ortholog of Xenopus synaptic vesicle-2-associated protein (svop), the molecular characteristics of which were unknown. The 3125-bp full-length cDNA encoded a 548-aa protein of approximately 60 kDa. A strong promoter element was found in the -200 to -100 bp region in both NG108-15 and HEK293 cells. RT-PCR and in situ hybridization analysis confirmed that msvop was strictly expressed in the mouse central nervous system. In adult brains, msvop was highly expressed in the hippocampus and cerebellum. When the gene was transfected into HEK293 cells in a GFP fusion vector, the protein was specifically localized in the cytosol. These results indicate that msvop is a central nervous system-specific gene and could be utilized for elucidating gene regulation in neuronal cells.