Neuron navigators: A novel frontier with physiological and pathological implications

Neuron navigators are microtubule plus-end tracking proteins containing basic and serine rich regions which are encoded by neuron navigator genes (NAVs). Neuron navigator proteins are essential for neurite outgrowth, neuronal migration, and overall neurodevelopment along with some other functions as well. The navigator proteins are substantially expressed in the developing brain and have been reported to be differentially expressed in various tissues at different ages. Over the years, the research has found neuron navigators to be implicated in a spectrum of pathological conditions such as developmental anomalies, neurodegenerative disorders, neuropathic pain, anxiety, cancers, and certain inflammatory conditions. The existing knowledge about neuron navigators remains sparse owing to their differential functions, undiscovered modulators, and unknown molecular mechanisms. Investigating the possible role of neuron navigators in various physiological processes and pathological conditions pose as a novel field that requires extensive research and might provide novel mechanistic insights and understanding of these aspects.

Tumour Suppressor Neuron Navigator 3 and Matrix Metalloproteinase 14 are Co-expressed in Most Melanomas but Downregulated in Thick Tumours

Melanoma is a highly metastatic tumour originating from neural crest-derived melanocytes. The aim of this study was to analyse the expression of neuron navigator 3 (NAV3) in relation to membrane type-1 matrix metalloproteinase MMP14, a major regulator of invasion, in 40 primary melanomas, 15 benign naevi and 2 melanoma cell lines. NAV3 copy number changes were found in 18/27 (67%) primary melanomas, so that deletions dominated (16/27 of samples, 59%). NAV3 protein was found to be localized at the leading edge of migrating melanoma cells in vitro. Silencing of NAV3 reduced both melanoma cell migration in 2-dimensional conditions, as well as sprouting in 3-dimensional collagen I. NAV3 protein expression correlated with MMP14 in 26/37 (70%) primary melanomas. NAV3 and MMP14 were co-expressed in all tumours with Breslow thickness < 1 mm, in 11/23 of mid-thickness tumours (1-5 mm), but in only 1/6 samples of thick (> 5 mm) melanomas. Altogether, NAV3 number changes are frequent in melanomas, and NAV3 and MMP14, while expressed in all thin melanomas, are often downregulated in thicker tumours, suggesting that the lack of both NAV3 and MMP14 favours melanoma progression.

NAV3 Is a Novel Prognostic Biomarker Affecting the Immune Status of the Tumor Microenvironment in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignant tumors in the world. Tumor microenvironment (TME) plays a crucial role in the development of CRC. With the deep understanding of TME function, growing studies have demonstrated that alteration in tumor-infiltrating immune cells (TICs) and gene expressions are associated with clinical outcomes of various tumors. In this study, we aimed to recognize critical prognostic genes involved in immune states in TME of CRC. Hence, the proportion of TICs and the number of immune and stromal components in CRC samples from TCGA datasets were calculated by the use of CIBERSORT and ESTIMATE calculation methods. Different assays were applied to collect differential expression genes (DEGs) shared by the ImmuneScore and StromalScore. DEGs were further analyzed by the use of univariate Cox regression. Our attention focused on neuron navigator 3 (NAV3) which was highly expressed in CRC specimens and associated with an advanced clinical stage and poor prognosis of CRC patients. KEGG assays revealed that NAV3 may be involved in Alzheimer disease, amyotrophic lateral sclerosis, Huntington disease, FoxO signaling pathway, and human papillomavirus infection. Correlation assays showed that macrophage M0 and B cells memory, NK cells activated, dendritic cells resting, T cells CD4 memory activated, and T cells CD8 were correlated with NAV3 expression, indicating that NAV3 may represent the immune status of TME. Finally, RT-PCR confirmed that NAV3 expression was distinctly increased in CRC cells, and its knockdown suppressed the proliferation of CRC cells. Overall, NAV3 could be used as a novel predictor for TME of CRC and might be a novel prognostic biomarker. In the future, drugs targeting NAV3 might be developed as a potential immunotherapy for CRC patients.

Benchmark of site- and structure-specific quantitative tissue N-glycoproteomics for discovery of potential N-glycoprotein markers: a case study of pancreatic cancer

Pancreatic cancer is a highly malignant tumor of the digestive tract that is difficult to diagnose and treat. It is more common in developed countries and has become one of the main causes of death in some countries and regions. Currently, pancreatic cancer generally has a poor prognosis, partly due to the lack of symptoms in the early stages of pancreatic cancer. Therefore, most cases are diagnosed at advanced stage. With the continuous in-depth research of glycoproteomics in precision medical diagnosis, there have been some reports on quantitative analysis of cancer-related cells, plasma or tissues to find specific biomarkers for targeted therapy. This research is based on the developed complete N-linked glycopeptide database search engine GPSeeker, combined with liquid-mass spectrometry and stable diethyl isotope labeling, providing a benchmark of site- and structure-specific quantitative tissue N-glycoproteomics for discovery of potential N-glycoprotein markers. With spectrum-level FDR ≤1%, 20,038 intact N-Glycopeptides corresponding to 4518 peptide backbones, 228 N-glycan monosaccharide compositions 1026 N-glycan putative structures, 4460 N-glycosites and 3437 intact N-glycoproteins were identified. With the criteria of ≥1.5-fold change and p value<0.05, 52 differentially expressed intact N-glycopeptides (DEGPs) were found in pancreatic cancer tussues relative to control, where 38 up-regulated and 14 down-regulated, respectively.

Identification of dysregulated miRNAs-genes network in ovarian cancer: An integrative approach to uncover the molecular interactions and oncomechanisms

Background

Ovarian (OV) cancer is considered as one of the most deadly malignancies in women, since it is unfortunately diagnosed in advanced stages. Nowadays, the importance of bioinformatics tools and their frequent usage in tracking dysregulated cancer‐related genes and pathways have been highlighted in researches.

Aim

The aim of this study is to investigate dysregulated miRNAs‐genes network and its function in OV tumors based on the integration of microarray data through a system biology approach.

Methods

Two microarray data (GSE119056 and GSE4122) were analyzed to explore the differentially expressed miRNAs (DEmiRs) and genes among OV tumors and normal tissues. Then, through the help of TargetScan, miRmap, and miRTarBase databases, the dysregulated miRNA‐gene network in OV tumors was constructed by Cytoscape. In the next step, co‐expression and protein‐protein interaction networks were made using GEPIA and STRING databases. Moreover, the functional analysis of the hub genes was done by DAVID, KEGG, and Enrichr databases. Eventually, the regulatory network of TF‐miRNA‐gene was constructed.

Results

The potential dysregulated miRNAs‐genes network in OV tumors has been constructed, including 109 differentially expressed genes (DEGs), 25 DEmiRs, and 213 interactions. Two down‐regulated microRNAs, miR‐660‐3p and hsa‐miR‐4510, have the most interactions with up‐expressed oncogenic DEGs. CDK1, PLK1, CCNB1, CCNA2, and EZH2 are involved in protein module, which show significant overexpression in OV tumors according to The Cancer Genome Atlas (TCGA) data. EZH2 shows amplification in OV tumors with remarkable percentage. The transcription factors TFAP2C and GATA4 have the pivotal regulatory functions in oncotranscriptomic profile of OV tumors.

Conclusion

In current study, we have collected and integrated different data to uncover the complex molecular interactions and oncomechanisms in OV tumors. The DEmiRs‐DEGs and TF‐miRNA‐gene networks reveal the potential interactions that could be a significant piece of the OV onco‐puzzle.

p73 - NAV3 axis plays a critical role in suppression of colon cancer metastasis

p73 is a member of the p53 tumor suppressor family, which transactivates p53-responsive genes and mediates DNA damage response. Recent evidences suggest that p73 exerts its tumor suppressor functions by suppressing metastasis, but the exact mechanism remains unknown. Here, we identify Navigator-3 (NAV3), a microtubule-binding protein, as a novel transcriptional target of p73, which gets upregulated by DNA damage in a p73-dependent manner and plays a vital role in p73-mediated inhibition of cancer cell invasion, migration, and metastasis. Induction of p73 in response to DNA damage leads to rapid increase in endogenous NAV3 mRNA and protein levels. Through bioinformatic analysis, we identified two p73-binding sites in NAV3 promoter. Consistent with this, p73 binding to NAV3 promoter was confirmed through luciferase, Chromatin Immunoprecipitation, and site-directed mutagenesis assays. Abrogation of NAV3 and p73 expression significantly increased the invasion and migration rate of colorectal cancer cells as confirmed by wound-healing, cell invasion, and cell migration assays. Also, knockdown of NAV3 decreased the expression of E-cadherin and increased the expression of other prominent mesenchymal markers such as N-cadherin, Snail, Vimentin, and Fibronectin. Immunohistochemistry analysis revealed the downregulation of both NAV3 and p73 expression in metastatic colon cancer tissues as compared to non-metastatic cancer tissues. Additionally, the expression pattern of NAV3 and p73 showed extensively significant correlation in both non-metastatic and metastatic human colon cancer tissue samples. Taken together, our study provide conclusive evidence that Navigator-3 is a direct transcriptional target of p73 and plays crucial role in response to genotoxic stress in p73-mediated inhibition of cancer cell invasion, migration, and metastasis.

NAV3, a Tumor Suppressor Gene, Is Decreased in Uterine Leiomyoma Tissue and Cells

NAV 3 is a tumor suppressor of unknown function in leiomyomas. The objective of this study is to assess NAV3 expression and its potential role in human uterine leiomyomas. NAV3 protein expression was examined in patient leiomyoma and patient-matched myometrial tissue samples by Western blot and immunohistochemistry. NAV3 mRNA and protein expression was assessed in leuprolide acetate- and cetrorelix-treated cell line leiomyoma samples. RNAseq analysis of placebo-treated leiomyoma compared with myometrium demonstrated the presence of transcripts encoding for several neuronal proteins. For NAV3, RNA sequence analysis demonstrated decreased expression in leiomyoma as compared with myometrium (0.86 ± 0.03 fold). Presence of NAV3 mRNA was also decreased in leiomyoma surgical samples (0.43 fold ± 0.05, p = 0.026) compared with patient-matched myometrium. Confirmatory qRT-PCR results on immortalized leiomyoma and myometrial cell lines similarly demonstrated a decrease in expression of NAV3 in leiomyomas (0.28 ± 0.02, p = 0.00075). Immunohistochemical analysis demonstrated a significant decrease in NAV 3 protein in leiomyomas (H-score 154.7 ± 6.2) as compared with myometrium (H-score; 312.5 ± 14.7, p < 0.0001). Leuprolide acetate-treated leiomyoma cells demonstrated an increase in NAV 3 mRNA expression (1.53 ± 0.13, p < 0.0001). Similarly, Western blot analysis on leuprolide-treated leiomyoma cells showed a non-significant increase in NAV 3 protein expression (1.26 ± 0.09, p = 0.063). NAV 3, a tumor suppressor in numerous cancers, is decreased in leiomyoma cells and tissue compared with myometrium, and increased by GnRH analog treatment, suggesting that NAV3 may mediate steroid hormone-independent leiomyoma regulation by GnRH analogs.

Human Papillomavirus Epitope Mimicry and Autoimmunity: The Molecular Truth of Peptide Sharing

OBJECTIVE

To define the cross-reactivity potential and the consequent autoimmunity intrinsic to viral versus human peptide sharing.

METHODS

Using human papillomavirus (HPV) infection/active immunization as a research model, the experimentally validated HPV L1 epitopes catalogued at the Immune Epitope DataBase were analyzed for peptide sharing with the human proteome.

RESULTS

The final data show that the totality of the immunoreactive HPV L1 epi-topes is mostly composed by peptides present in human proteins.

CONCLUSIONS

Immunologically, the high extent of peptide sharing between the HPV L1 epitopes and human proteins invites to revise the concept of the negative selection of self-reactive lymphocytes. Pathologically, the data highlight a cross-reactive potential for a spectrum of autoimmune diseases that includes ovarian failure, systemic lupus erythematosus (SLE), breast cancer and sudden death, among others. Therapeutically, analyzing already validated immunoreactive epitopes filters out the peptide sharing possibly exempt of self-reactivity, defines the effective potential for pathologic autoimmunity, and allows singling out peptide epitopes for safe immunotherapeutic protocols.

miR-29c regulates NAV3 protein expression in a transgenic mouse model of Alzheimer's disease

The microRNA-29 family (miRNA-29s) has three mature members, miR-29a, miR-29b and miR-29c, which have been implicated in the regulation of the pathogenesis of Alzheimer's disease (AD). The miR-29 family members exhibit differential regulation in various diseases and different subcellular distribution. In the present study, we initially investigated differential expression of miR-29c in the hippocampus and the frontal cortex of the young APPswe/PSΔE9 mouse brain, accompanied by inverse expression of neurone navigator 3 (NAV3), a regulator of axon guidance. We observed that miR-29c directly mediated downregulation of NAV3 protein expression in vitro. The mouse NAV3 mRNA has a functional miR-29c binding site in the 3' UTR, which localized in the position between 830-836 bp of 3'UTR region, slightly different from human NAV3 mRNA binding site. These observations suggest that miR-29c may be involved in neurodegenerative processes by regulating NAV3 expression in the young AD mouse.

MiR-21 promoted proliferation and migration in hepatocellular carcinoma through negative regulation of Navigator-3

MicroRNA-21 (miR-21) has been well-established and found to be over-expressed in various human cancers and has been associated with hepatocellular carcinoma (HCC) progression. However, the underlying mechanism of miR-21 involvement in the development and progression of HCC remains to be understood. In the present study, we firstly identified that the Navigator-3 (NAV-3) gene as a novel direct target of miR-21. Knock-down of NAV-3 using shRNA can rescue the effects of anti-miR-21 inhibitor in HCC cell lines, whereas re-expression of miR-21 using transfection with miR-21 mimics phenocopied the NAV-3 knock-down model. Additionally, miR-21 levels inversely correlated with NAV-3 both in HCC cells and tissues. Knock-down of NAV-3 promoted both the proliferation and migration in HCC cells. Together, our findings suggest an important role for miR-21 in the progression of HCC, which negatively regulated Navigator-3 in the migration of HCC.

Programmed cell death 6 interacting protein (PDCD6IP) and Rabenosyn-5 (ZFYVE20) are potential urinary biomarkers for upper gastrointestinal cancer

PURPOSE

Cancer of the upper digestive tract (uGI) is a major contributor to cancer-related death worldwide. Due to a rise in occurrence, together with poor survival rates and a lack of diagnostic or prognostic clinical assays, there is a clear need to establish molecular biomarkers.

EXPERIMENTAL DESIGN

Initial assessment was performed on urine samples from 60 control and 60 uGI cancer patients using MS to establish a peak pattern or fingerprint model, which was validated by a further set of 59 samples.

RESULTS

We detected 86 cluster peaks by MS above frequency and detection thresholds. Statistical testing and model building resulted in a peak profiling model of five relevant peaks with 88% overall sensitivity and 91% specificity, and overall correctness of 90%. High-resolution MS of 40 samples in the 2-10 kDa range resulted in 646 identified proteins, and pattern matching identified four of the five model peaks within significant parameters, namely programmed cell death 6 interacting protein (PDCD6IP/Alix/AIP1), Rabenosyn-5 (ZFYVE20), protein S100A8, and protein S100A9, of which the first two were validated by Western blotting.

CONCLUSIONS AND CLINICAL RELEVANCE

We demonstrate that MS analysis of human urine can identify lead biomarker candidates in uGI cancers, which makes this technique potentially useful in defining and consolidating biomarker patterns for uGI cancer screening.

Navigator-3, a modulator of cell migration, may act as a suppressor of breast cancer progression

Dissemination of primary tumor cells depends on migratory and invasive attributes. Here, we identify Navigator-3 (NAV3), a gene frequently mutated or deleted in human tumors, as a regulator of epithelial migration and invasion. Following induction by growth factors, NAV3 localizes to the plus ends of microtubules and enhances their polarized growth. Accordingly, NAV3 depletion trimmed microtubule growth, prolonged growth factor signaling, prevented apoptosis and enhanced random cell migration. Mathematical modeling suggested that NAV3-depleted cells acquire an advantage in terms of the way they explore their environment. In animal models, silencing NAV3 increased metastasis, whereas ectopic expression of the wild-type form, unlike expression of two, relatively unstable oncogenic mutants from human tumors, inhibited metastasis. Congruently, analyses of > 2,500 breast and lung cancer patients associated low NAV3 with shorter survival. We propose that NAV3 inhibits breast cancer progression by regulating microtubule dynamics, biasing directionally persistent rather than random migration, and inhibiting locomotion of initiated cells.

Potential role of a navigator gene NAV3 in colorectal cancer

Background:

The recently described navigator proteins have a multifaceted role in cytoskeletal dynamics. We report here on the relevance of one of them, navigator 3 (NAV3), in colorectal cancer (CRC).

Methods:

We analysed changes in chromosome 12 and NAV3 copy number in CRC/adenoma samples of 59 patients and in 6 CRC cell lines, using fluorescence in situ hybridisation, loss of heterozygosity, and array-CGH. NAV3 target genes were identified by siRNA depletion, expression arrays, and immunohistochemistry.

Results:

NAV3 deletion and chromosome 12 polysomy were detected in 30 and 70% of microsatellite stability (MSS) carcinomas, in 23 and 30% of adenomas and in four of six CRC cell lines. NAV3 amplification was found in 25% of MSS samples. NAV3 alterations correlated with lymph node metastasis. In normal colon cells, NAV3 silencing induced upregulation of interleukin 23 receptor (IL23R) and gonadotropin releasing hormone receptor. In MSS and microsatellite instability tumours, IL23R immunoreactivity correlated with Dukes’ staging and lymph node metastases, whereas nuclear beta-catenin correlated with lymph node metastases only.

Conclusion:

NAV3 copy number changes are frequent in CRC and in adenomas, and upregulation of IL23R, following NAV3 silencing, strongly correlates with Dukes’ staging and lymph node metastases. This suggests that NAV3 has a role in linking tissue inflammation to cancer development in the colon.