NRAGE suppresses metastasis of melanoma and pancreatic cancer in vitro and in vivo

Knockdown of neurotrophin receptor-interacting melanoma-associated antigen homolog inhibits acute myeloid leukemia cell growth via the ERK pathway

Neurotrophin receptor-interacting melanoma-associated antigen homolog (NRAGE), a type II melanoma-associated antigen, plays a critical role in cell processes that are involved in the tumorigenesis of various cancers. However, the effect of NRAGE on acute myeloid leukemia (AML) is rarely reported. The expression of NRAGE in AML tissues and the survival rates between different AML groups were obtained from the GEPIA tool. Human AML cell lines were cultured and transfected with siRNA targeting NRAGE. The ability of AML cells to proliferate and cell cycle were examined. Western blotting was performed to detect the activity of the extracellular signal-regulated kinase (ERK) signaling pathway in AML cells. NRAGE expression was enhanced in AML tissues relative to control tissues, and the high NRAGE expression in AML patients is associated with a poor prognosis. The capacity of AML cells to survive and proliferate was significantly decreased and its cell cycle was arrested at the G1 phase after NRAGE was silenced. Furthermore, silencing NRAGE induced the inactivation of the ERK signaling pathway. Furthermore, supplement of tert-Butylhydroquinone, an ERK activator, improved the reduced ability of AML cell survival and proliferation as well as cell cycle arrest induced by NRAGE knockdown. In this study, NRAGE was identified as a tumor promoter in AML, which had an effect on cell proliferation, cell survival, and cell cycle through the ERK signaling pathway in AML cells.

Transcriptomic characterization and construction of M2 macrophage-related prognostic and immunotherapeutic signature in ovarian metastasis of gastric cancer

BACKGROUND

Ovarian metastasis (OM) poses a major threat to the outcome of gastric cancer (GC) patients. Recently, immunotherapy emerged as a novel promising therapeutic strategy to treat late-stage GC, whereas its efficacy is influenced by tumor immune microenvironment (TIME). M2 macrophage, a key subset within TIME, plays dual immunosuppressive and pro-tumorigenic roles in cancer progression and is recognized as a potential therapeutic target. However, molecular mechanisms underlying OM remain elusive and the TIME-related prognostic and immunotherapeutic index for these patients is yet to establish.

METHODS

Differential expressed genes (DEGs) between paired normal mucosa, primary GC and OM of patients from Fudan University Shanghai Cancer Center (FUSCC) cohort (n = 6) were identified by transcriptome sequencing, followed by the functional annotation of enriched hallmark pathways of DEGs between them. CIBERSORT was used to profile the relative expression level of 22 immune cell subsets in normal tissues, primary and metastatic tumors, followed by weighted gene coexpression network analysis (WGCNA) uncovering immune cell-correlated gene sets. The intersected genes between DEGs and M2 macrophage-related genes were processed by least absolute shrinkage and selection operator (LASSO) regression analysis to construct a predictive signature, M2GO, which was further validated by training set and test set of The Cancer Genome Atlas-Stomach Adenocarcinoma (TCGA-STAD), GSE62254 and GSE84437 cohorts. GC patients were divided into M2GO-high and -low subgroup according to the optimal cutoff value of the M2GO score. Furthermore, the clinical, molecular and immune features between M2GO-high and -low subgroups were analyzed. Clinical cohorts of immunotherapy were used to validate the predictive value of M2GO in regard to immunotherapy effectiveness.

RESULTS

Transcriptomic sequencing and follow-up analyses of triple-matched normal tissues, primary and ovarian metastatic tumors identified distinctive sets of DEGs and enriched immune-, cancer- and metastasis-related pathways between them. Of note, M2 macrophage, a major immunosuppressive and pro-tumorigenic component within TIME, was significantly up-regulated in OMs. WGCNA and LASSO regression were applied to establish a novel OM- and M2 macrophage-related predictive signature, M2GO, based on M2 macrophage-related prognostic genes including GJA1, MAGED1 and SERPINE1. M2GO served as an independent prognostic factor of GC patients. Comprehensive molecular and immune characterization of M2GO-based subgroups uncovered their distinctive features in terms of enriched functional pathways, tumor mutation burden, key immune checkpoints, major regulators of natural immune cGAS-STING pathway, infiltrated subsets of immune cells and tumor immune exclusion/dysfunction (TIDE) score. Notably, the M2GO score was significantly lower in responsive group than non-responsive group (P < 0.05) in clinical cohort of metastatic GC patients undergoing immunotherapy.

CONCLUSION

Transcriptomic characterization of paired normal mucosae, primary and ovarian metastatic tumors revealed their unique molecular and immune features. Follow-up analyses established a novel OM- and M2 macrophage-related signature, M2GO, which served as a promising prognostic and immunotherapeutic biomarker to distinguish the clinical outcome, molecular and immune features of GC patients and predict their differential responses to immunotherapy.

Dynamic expression of Mage-D1 in rat dental germs and potential role in mineralization of ectomesenchymal stem cells

Mage-D1 (MAGE family member D1) is involved in a variety of cell biological effects. Recent studies have shown that Mage-D1 is closely related to tooth development, but its specific regulatory mechanism is unclear. The purpose of this study was to investigate the expression pattern of Mage-D1 in rat dental germ development and its differential mineralization ability to ectomesenchymal stem cells (EMSCs), and to explore its potential mechanism. Results showed that the expression of Mage-D1 during rat dental germ development was temporally and spatially specific. Mage-D1 promotes the proliferation ability of EMSCs but inhibits their migration ability. Under induction by mineralized culture medium, Mage-D1 promotes osteogenesis and tooth-forming ability. Furthermore, the expression pattern of Mage-D1 at E19.5 d rat dental germ is similar to p75 neurotrophin receptor (p75NTR), distal-less homeobox 1 (Dlx1) and msh homeobox 1 (Msx1). In addition, Mage-D1 is binding to p75NTR, Dlx1, and Msx1 in vitro. These findings indicate that Mage-D1 is play an important regulatory role in normal mineralization of teeth. p75NTR, Dlx1, and Msx1 seem to be closely related to the underlying mechanism of Mage-D1 action.

Knockdown of NRAGE Impairs Homologous Recombination Repair and Sensitizes Hepatoblastoma Cells to Ionizing Radiation

Background: NRAGE (neurotrophin receptor-interacting melanoma antigen-encoding gene homolog) has a complex role and regulates cell growth in different tumor cells. Although NRAGE was been discovered for more than 10 years ago, the function of NRAGE in hepatoblastoma (HB) cells is currently unknown. Materials and Methods: The expression of NRAGE was detected by reverse transcription-quantitative polymerase chain reaction assay or western blotting assay. Cellular apoptosis was analyzed to estimate the effect of NRAGE under radiation. The ability of clonogenic capacity was evaluated to confirm the influence of proliferation for NRAGE by radiation. The immunofluorescence assay was used to further study the expression of NRAGE under radiation. A nude mouse tumor xenograft model was constructed to confirm the effect of NRAGE deficiency under radiation conditions in vivo. Results: The authors determined that deletion of NRAGE significantly inhibited HB cell proliferation in vitro and in vivo, and NRAGE knockdown apparently sensitized HB cells to ionizing radiation (IR). Further mechanistic studies revealed that NRAGE plays a critical role in homologous recombination by inhibiting the expression of RNF8 (ring finger protein 8) and BARD1 (BRCA1 associated RING domain 1) and the recruitment of RAD51. Conclusions: The authors demonstrated that downregulation of NRAGE sensitizes HB cell lines to IR in vitro and in vivo. It provides a promising therapeutic strategy for HB patients by specifically targeting NRAGE.

Knockdown of NRAGE induces odontogenic differentiation by activating NF-κB signaling in mouse odontoblast-like cells

PURPOSE

Neurotrophin receptor-interacting MAGE homologue (Nrage) plays an important role in bone development and the metabolism of normal skeletal structures. Our previous study showed that Nrage inhibited the odontogenic differentiation of mouse dental pulp cells. However, the potential roles and mechanism of Nrage in regulating odontogenic differentiation are unknown. The aim of this study was to investigate the molecular mechanism of Nrage in odontogenic differentiation of mouse odontoblast-like cells.

MATERIALS AND METHODS

Endogenous expression of Nrage was stably downregulated by lentivirus-mediated shRNA. Mineralized nodules formation was detected by alizarin red S staining. Dmp-1, Dspp, and ALP mRNA and protein levels were detected by qRT-PCR and western blotting, respectively. In addition, ALPase activity was detected. Confocal microscopy and co-immunoprecipitation (co-IP) were used to analyze the interactions between NRAGE and NF-κB signaling molecules. An IKK inhibitor was also used in the study.

RESULTS

NRAGE expression in odontoblasts was downregulated during mouse first maxillary molar development. Moreover, NRAGE expression was downregulated during odontogenic differentiation of odontoblast-like cells. NRAGE knockdown significantly upregulated DMP1 and DSP expression, increased ALPase activity, and promoted mineralized nodule formation. In addition, NRAGE knockdown increased the translocation of NF-κB1 to the nucleus and phosphorylation levels of p65. Co-IP results showed that NRAGE bound to IKKβ. Most importantly, the promoting effect of Nrage knockdown on odontoblastic differentiation was reduced after treatment with an IKK inhibitor.

CONCLUSIONS

Our data confirmed that NRAGE is an important regulator of odontogenic differentiation of odontoblasts by inhibiting the NF-κB signaling pathway through binding to IKKβ.

ABBREVIATIONS

Nrage: neurotrophin receptor-interacting MAGE homologue; DSP: dentin sialophospho protein; DMP-1: dentin matrix protein-1; BMP: bone morphogenetic protein; Wnt: wingless; NF-κB: nuclear factor of activated B cells; DAPI: 4',6-diamidino-2-phenylindole; KO: knockout; DPCs: dental pulp cells; AA: ascorbic acid; β-Gly: β-glycerophosphate; Dex: dexamethasone; co-IP: co-immunoprecipitation; IκB: inhibitor of NF-κB; IKK: IκB kinase.

NRAGE is a potential diagnostic biomarker of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers and a leading cause of cancer-related deaths worldwide. Early diagnosis of HCC remains a great challenge in clinic. Novel and effective biomarkers are in urgent need in early diagnosis of HCC.Serum levels of neurotrophin-receptor-interacting melanoma antigen-encoding gene homolog (NRAGE) were measured for 107 patients with HCC, 98 patients with benign liver diseases, and 89 healthy controls using quantitative real-time polymerase chain reaction. Receiver operating characteristic curve was applied to evaluate the diagnostic capacity of serum NRAGE in HCC.NRAGE expression was significantly higher in patients with HCC than in controls (all, P < .05). Moreover, its expression was tightly correlated with TNM stage (P = .004). NRAGE could distinguish patients with HCC from healthy controls with the area under the curve (AUC) of 0.874, yielding a sensitivity of 81.3% and a specificity of 78.7%. Additionally, in differentiation between benign liver diseases and HCC, the AUC value of NRAGE was 0.726, with a sensitivity of 63.6% and a specificity of 73.5%. Meanwhile, alpha-fetoprotein also could distinguish patients with HCC from benign liver disease cases, with an AUC of 0.677, a sensitivity of 64.4%, and a specificity of 60.2%.NRAGE could be a potential biomarker for HCC early diagnosis.

NRAGE confers poor prognosis and promotes proliferation, invasion, and chemoresistance in gastric cancer

Neurotrophin receptor-interacting melanoma antigen-encoding protein (NRAGE) is a type II melanoma-associated antigen that plays an essential role in various processes, including cell differentiation and apoptosis. NRAGE has been shown to act as a cancer-related protein, with complex and apparently contradictory functions in a variety of cancers. In the current study, we examined the expression of NRAGE protein in 169 gastric cancer samples. NRAGE upregulation was correlated with advanced TNM stage, local invasion, and poor survival. Importantly, NRAGE could serve as an independent prognostic factor in patients with gastric cancer. We also examined the expression of NRAGE protein in GES-1 normal gastric epithelial cells and in six gastric cancer cell lines. Inhibition of NRAGE expression by transfection with small interfering RNA reduced the proliferation and invasion of MGC-803 and HGC-27 cells, as demonstrated by CCK-8 and Matrigel invasion assays. NRAGE depletion also sensitized HGC-27 and MGC-803 cells to cisplatin, as shown by CCK-8 and Annexin V/propidium iodide analyses. Western blot analysis also showed that NRAGE depletion negatively regulated Bcl-2 and p-ERK and upregulated ZO-1 and p27 expression levels. In conclusion, our results suggest that NRAGE acts as a tumor promoter in gastric cancer by facilitating cancer invasion and chemoresistance, possibly through regulation of p-ERK and Bcl-2.

Gene expression network regulated by DNA methylation and microRNA during microcystin-leucine arginine induced malignant transformation in human hepatocyte L02 cells

Microcystin (MC) is a cyclic heptapeptide compound which could lead to the development of hepatocellular carcinoma. However, the underlying epigenetic regulation mechanism is largely unknown. In this study, microcystin-LR (L: lysine, R: arginine, MC-LR) was used to induce the malignant transformation of human hepatocyte L02 cell line. The profile of gene expression, microRNA (miRNA) and DNA methylation were detected through high-throughput sequencing. Compared with control group, the expression of 826 genes and 187 miRNAs changed significantly in MC-LR treated group. DNA methylation sequencing analysis showed that 2592 CpG sites differentially methylated in promoter or the coding DNA sequence (CDS) of genes, while DNA methyltransferase 3 alpha (DNMT3a) and DNA methyltransferase 3 beta (DNMT3b) were dramatically up-regulated. Functional analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that significantly changed mRNAs and microRNAs were mainly involved in the formation of cancer, proliferation, invasion, migration and metabolism. MiRNA-mRNA network and mRNA-mRNA network analysis showed that hsa-miR-320a, hsa-miR-331-3p, hsa-miR-26a-5p, hsa-miR-196a-5p, hsa-miR-221-3p, coiled-coil domain containing 180 (CCDC180), melanoma antigen gene family member D1 (MAGED1), membrane spanning 4-domains A7 (MS4A7), hephaestin like 1 (HEPHL1), BH3 (Bcl-2 homology 3)-like motif containing, cell death inducer (BLID), matrix metallopeptidase 13 (MMP13), guanylate binding protein 5 (GBP5), adipogenesis regulatory factor (ADIRF), formin homology 2 domain containing 1 (FHDC1), protein kinase CAMP-dependent type II regulatory subunit beta (PRKAR2B), nodium leak channel, non-selective (NALCN), myosin light chain kinase 3 (MYLK3), epidermal growth factor receptor (EGFR) and zinc finger protein 704 (ZNF704) were key miRNAs and genes in the malignant transformation induced by MC-LR in L02 cells. Moreover, we found that expression of MYLK3, EGFR and ZNF704 were regulated by DNA methylation and miRNAs, and these genes affected the cell cycle and cell division. Our study suggested that characteristic gene alterations regulated by DNA methylation and miRNA could play an important role in environmental MC-LR induced hepatic carcinogenesis.

Molecular mechanisms of peritoneal dissemination in gastric cancer

Peritoneal dissemination represents a devastating form of gastric cancer (GC) progression with a dismal prognosis. There is no effective therapy for this condition. The 5-year survival rate of patients with peritoneal dissemination is 2%, even including patients with only microscopic free cancer cells without macroscopic peritoneal nodules. The mechanism of peritoneal dissemination of GC involves several steps: detachment of cancer cells from the primary tumor, survival in the free abdominal cavity, attachment to the distant peritoneum, invasion into the subperitoneal space and proliferation with angiogenesis. These steps are not mutually exclusive, and combinations of different molecular mechanisms can occur in each process of peritoneal dissemination. A comprehensive understanding of the molecular events involved in peritoneal dissemination is important and should be systematically pursued. It is crucial to identify novel strategies for the prevention of this condition and for identification of markers of prognosis and the development of molecular-targeted therapies. In this review, we provide an overview of recently published articles addressing the molecular mechanisms of peritoneal dissemination of GC to provide an update on what is currently known in this field and to propose novel promising candidates for use in diagnosis and as therapeutic targets.

Neurotrophin Receptor-Interacting Melanoma Antigen-Encoding Gene Homolog is Associated with Malignant Phenotype of Gastric Cancer

BACKGROUND

Identification of novel molecules implicated in the malignancy of gastric cancer (GC) is key to the development of personalized treatments and the improvement of patient outcome. Neurotrophin receptor-interacting melanoma antigen-encoding protein (NRAGE) regulates apoptosis and metastasis via interactions with various genes. This study aimed to evaluate the function and clinical significance of NRAGE in GC.

METHODS

The expression of NRAGE and its putative interacting genes apoptosis antagonizing transcription factor (AATF), p75 neurotrophin receptor (p75NTR), and proliferating cell nuclear antigen (PCNA) were determined in GC cell lines using reverse transcription-polymerase chain reaction (RT-PCR). The effect of NRAGE knockdown by small interfering RNA (siRNA) on GC cell behavior also was evaluated. In addition, NRAGE expression was determined in 179 pairs of resected gastric tissues.

RESULTS

Expression of NRAGE mRNA positively correlated with that of AATF, and NRAGE knockdown significantly decreased the proliferation, migration, and invasion of GC cells. The mean level of NRAGE mRNA expression was significantly higher in GC tissues than in corresponding adjacent normal tissues. The expression patterns of NRAGE mRNA and protein were closely correlated. A stepwise elevation in NRAGE mRNA expression in GC tissues was observed with increasing Union for International Cancer Control (UICC) stage. High NRAGE expression in GCs was associated with shortened recurrence-free survival and identified as an independent prognostic factor (hazard ratio, 1.83; 95 % CI, 1.12-3.02, p = 0.017).

CONCLUSIONS

The results indicate that NRAGE represents a putative oncogene associated with a malignant phenotype of GC. In GC, NRAGE may serve as a predictive biomarker and a target of molecular therapy.

Complex roles of NRAGE on tumor

NRAGE, also known as Dlxin-1or MAGE-D1, is a member of type II melanoma-associated antigen (MAGE) and plays an essential role in life activities, including differentiation, apoptosis, and cell cycle. Studies increasingly found that NRAGE is closely related to the tumor events, such as tumor occurrence, invasion, and metastasis. However, complex and contradictory functions of NRAGE in different circumstances are observed, suggesting that NRAGE is unique from other MAGE gene family members. This review summarizes recent findings concerning the structure and biological functions of NRAGE, which may provide a basis for a more comprehensive understanding of and further research on NRAGE.

Effects of neurotrophin receptor-mediated MAGE homology on proliferation and odontoblastic differentiation of mouse dental pulp cells

OBJECTIVES

This study aimed to investigate effects of neurotrophin receptor-mediated melanoma antigen-encoding gene homology (NRAGE) on proliferation and odontoblastic differentiation of mouse dental pulp cells (mDPCs).

MATERIALS AND METHODS

Mouse dental pulp cells were infected with recombinant lentivirus to stably knockdown expression of NRAGE, and biological effects of NRAGE on the cells were detected. Proliferation and odontoblastic differentiation of mDPCs were observed. Simultaneously, mRNA and protein levels of NRAGE and nuclear factor-κB (NF-κB) protein expression were detected. Immunofluorescence assay was used to detect expression and location of NRAGE and NF-κB.

RESULTS

NRAGE mRNA and protein levels reduced significantly after mDPC odontoblastic induction. Knockdown of NRAGE inhibited the proliferation of mDPCs. However, knockdown of NRAGE enhanced their odontoblastic differentiation with up-regulated ALPase activity. It also promoted mineral nodule formation as well as mRNA and protein expressions of ALP, DSPP and DMP1. Protein levels of NF-κB/p50 significantly increased, whereas NF-κB/p105 protein expression decreased in the mDPC/shNRG group. Immunofluorescence revealed that relocation of NF-κB was similar to that of NRAGE during odontoblastic induction, in which NF-κB translocated from the cytoplasm to the nucleus.

CONCLUSION

NRAGE is a potent regulator of proliferation and odontoblastic differentiation of mDPCs, which might be via the NF-κB signalling pathway.

Spiclomazine induces apoptosis associated with the suppression of cell viability, migration and invasion in pancreatic carcinoma cells

The effective treatment for pancreatic carcinoma remains critically needed. Herein, this current study showed that spiclomazine treatment caused a reduction in viability in pancreatic carcinoma cell lines CFPAC-1 and MIA PaCa-2 in vitro. It was notable in this regard that, compared with pancreatic carcinoma cells, normal human embryonic kidney (HEK-293) and liver (HL-7702) cells were more resistant to the antigrowth effect of spiclomazine. Biochemically, spiclomazine treatment regulated the expression of protein levels in the apoptosis related pathways. Consistent with this effect, spiclomazine reduced the mitochondria membrane potential, elevated reactive oxygen species, and activated caspase-3/9. In addition, a key finding from this study was that spiclomazine suppressed migration and invasion of cancer cells through down-regulation of MMP-2/9. Collectively, the proposed studies did shed light on the antiproliferation effect of spiclomazine on pancreatic carcinoma cell lines, and further clarified the mechanisms that spiclomazine induced apoptosis associated with the suppression of migration and invasion.

Ror2-Src signaling in metastasis of mouse melanoma cells is inhibited by NRAGE

The receptor tyrosine kinase (RTK) Ror2 plays important roles in developmental morphogenesis and mediates the filopodia formation in Wnt5a-induced cell migration. However, the function of Ror2 in noncanonical Wnt signaling resulting in cancer metastasis is largely unknown. Here, we show that Ror2 expression is higher in the highly metastatic murine B16-BL6 melanoma cells than in the low metastatic variant B16 cells. Overexpression of Ror2 increases the metastasis ability of B16 cells, and knockdown of Ror2 reduces the migration ability of B16-BL6 cells. Furthermore, the inhibition of Src kinase activity is critical for the Ror2-mediated cell migration upon Wnt5a treatment. The C-terminus of Ror2, which is deleted in brachydactyly type B (BDB), is essential for the mutual interaction with the SH1 domain of Src. Intriguingly, the Neurotrophin receptor-interacting MAGE homologue (NRAGE), which, as we previously reported, can remodel the cellular skeleton and inhibit cell-cell adhesion and metastasis of melanoma and pancreatic cancer, sharply blocks the interaction between Src and Ror2 and inhibits Ror2-mediated B16 cell migration by decreasing the activity of Src and focal adhesion kinase (FAK). Our data show that Ror2 is a potential factor in the tumorigenesis and metastasis in a Src-dependent manner that is negatively regulated by NRAGE.

Toward an integrative analysis of the tumor microenvironment in ovarian epithelial carcinoma

Ovarian epithelial carcinomas are heterogeneous malignancies exhibiting great diversity in histological phenotypes as well as genetic and epigenetic aberrations. A general early event in tumorigenesis is regional dissemination into the peritoneal cavity. Initial spread to the peritoneum is made possible by cooperative signaling between a wide array of molecules constituting the tissue microenvironment in the coelomic epithelium. Changes in the activity of key microenvironmental components not constitutively expressed in normal tissue, including several disclosed adhesion molecules, growth factors, proteases, and G-protein coupled receptors (GPCRs), coordinate the transition. Remodeling of the extracellular matrix (ECM) and subsequent cell surface interactions enable transformation by promoting chromosomal instability (CIN) and stimulating several common signal transduction cascades to prepare the tissue for harboring and facilitating growth, angiogenesis and metastasis of the developing tumor.

A small peptide modeled after the NRAGE repeat domain inhibits XIAP-TAB1-TAK1 signaling for NF-κB activation and apoptosis in P19 cells

In normal growth and development, apoptosis is necessary to shape the central nervous system and to eliminate excess neurons which are not required for innervation. In some diseases, however, apoptosis can be either overactive as in some neurodegenerative disorders or severely attenuated as in the spread of certain cancers. Bone morphogenetic proteins (BMPs) transmit signals for regulating cell growth, differentiation, and apoptosis. Responding to BMP receptors stimulated from BMP ligands, neurotrophin receptor-mediated MAGE homolog (NRAGE) binds and functions with the XIAP-TAK1-TAB1 complex to activate p38^MAPK and induces apoptosis in cortical neural progenitors. NRAGE contains a unique repeat domain that is only found in human, mouse, and rat homologs that we theorize is pivotal in its BMP MAPK role. Previously, we showed that deletion of the repeat domain inhibits apoptosis, p38^MAPK phosphorylation, and caspase-3 cleavage in P19 neural progenitor cells. We also showed that the XIAP-TAB1-TAK1 complex is dependent on NRAGE for IKK-α/β phosphorylation and NF-κB activation. XIAP is a major inhibitor of caspases, the main executioners of apoptosis. Although it has been shown previously that NRAGE binds to the RING domain of XIAP, it has not been determined which NRAGE domain binds to XIAP. Here, we used fluorescence resonance energy transfer (FRET) to determine that there is a strong likelihood of a direct interaction between NRAGE and XIAP occurring at NRAGE's unique repeat domain which we also attribute to be the domain responsible for downstream signaling of NF-κB and activating IKK subunits. From these results, we designed a small peptide modeled after the NRAGE repeat domain which we have determined inhibits NF-κB activation and apoptosis in P19 cells. These intriguing results illustrate that the paradigm of the NRAGE repeat domain may hold promising therapeutic strategies in developing pharmaceutical solutions for combating harmful diseases involving excessive downstream BMP signaling, including apoptosis.

A pathway for the control of anoikis sensitivity by E-cadherin and epithelial-to-mesenchymal transition

Detachment of epithelial cells from matrix or attachment to an inappropriate matrix engages an apoptotic response known as anoikis, which prevents metastasis. Cellular sensitivity to anoikis is compromised during the oncogenic epithelial-to-mesenchymal transition (EMT), through unknown mechanisms. We report here a pathway through which EMT confers anoikis resistance. NRAGE (neurotrophin receptor-interacting melanoma antigen) interacted with a component of the E-cadherin complex, ankyrin-G, maintaining NRAGE in the cytoplasm. Oncogenic EMT downregulated ankyrin-G, enhancing the nuclear localization of NRAGE. The oncogenic transcriptional repressor protein TBX2 interacted with NRAGE, repressing the tumor suppressor gene p14ARF. P14ARF sensitized cells to anoikis; conversely, the TBX2/NRAGE complex protected cells against anoikis by downregulating this gene. This represents a novel pathway for the regulation of anoikis by EMT and E-cadherin.

NRAGE is a negative regulator of nerve growth factor-stimulated neurite outgrowth in PC12 cells mediated through TrkA-ERK signaling

NRAGE, also denominated as MAGE-D1 or Dlxin-1, is firstly identified as a molecule interacting with NGF low affinity receptor p75NTR. It facilitates cell cycle arrest and NGF-dependent neuronal apoptosis. Here we report that NRAGE is downregulated while p75NTR is upregulated during the process of NGF-induced neuronal differentiation of PC12 cells. Knockdown of NRAGE by RNA interference accelerates NGF-mediated neurite outgrowth. In addition, in the NRAGE-suppressed cells, NGF-induced ERK activation is increased and this activation is MEK-dependent. Conversely, NRAGE overexpression significantly represses NGF-induced ERK activation. Further studies revealed that NRAGE downregulates TrkA expression through a post-transcriptional manner and thereby blocks NGF-induced TrkA phosphrylation at tyrosine-490. Altogether, these data indicate for the first time that NRAGE is an endogenous inhibitor for NGF-induced neuronal differentiation of PC12 cells by regulating TrkA-ERK signaling.

Dlxin-1, a MAGE family protein, induces accelerated neurite outgrowth and cell survival by enhanced and early activation of MEK and Akt signalling pathways in PC12 cells

Dlxin-1 (also known as NRAGE or MAGED1) is a member of Type II melanoma-associated antigen (MAGE) family of proteins characterized by presence of a unique region of about 200 amino acids known as the MAGE homology domain (MHD). Dlxin-1 is associated with a large number of diverse cellular functions ranging from transcriptional regulation, cell cycle progression and differentiation to developmental apoptosis. While there are numerous studies reporting the role of NRAGE in facilitating cell death by interaction with p75NTR, we found varied effects of Dlxin-1 over-expression on PC12 cells grown in presence of NGF. These include induction of increased cell survival in presence of NGF and accelerated neuronal differentiation. We here categorically demonstrate that the effects on neuritogenesis are promoted through interactions of Dlxin-1 with the neurotrophin receptor TrkA. Further, using pharmacological inhibitors to specific pathways, we delineate the effects on enhanced neuritogenesis to the early and sustained activation of MEK pathway whereas the effects on cell survival to the early activation of Akt pathway. Next, we demonstrate a physical interaction of necdin with Dlxin-1 in PC12 cells. Our results establish that Dlxin-1 is an enhancer of neuronal differentiation and suggests that its possible interaction with NGF and necdin is critical in mediating pathways involved in neuronal survival and differentiation. Further in-depth analyses of the activation of various signalling pathways mediated through interaction with Dlxin-1 may provide valuable insight on the mechanisms that govern decisions regarding neuronal survival, growth, differentiation or apoptosis.

Mapping of NRAGE domains reveals clues to cell viability in BMP signaling

Bone morphogenetic signaling (BMP) is a key pathway during neurogenesis and depends on many downstream intermediators to carry out its signaling. One such signaling pathway utilizes neurotrophin receptor-interacting MAGE protein (NRAGE), a member of the melanoma-associated antigen (MAGE) family, to upregulate p38 mitogen activated protein kinase (p38(MAPK)) in response to cellular stress and activate caspases which are critical in leading cells to death. NRAGE consists of two conserved MAGE homology domains separated by a unique hexapeptide repeat domain. Although we have previously implicated NRAGE in inducing apoptosis in neural progenitors and P19 cells, a model system for neural progenitors, its domains have yet to be explored in determining which one may be responsible for setting up the signaling for apoptosis. Here, we overexpressed a series of deletion mutations in P19 cells to show that only those with at least half of the repeat domain, activated p38(MAPK) and underwent apoptosis offering intriguing incite into NRAGE's contribution in BMP apoptotic signaling.

Identification of liver metastasis-related genes in a novel human pancreatic carcinoma cell model by microarray analysis

Pancreatic cancer with liver metastases has a poor prognosis and the molecular mechanisms remain unclear. In this study, SW1990HM, a highly metastatic human pancreatic carcinoma line was subcloned from SW1990 by intrasplenic injection. In vivo and in vitro tumorigenicity, metastatic potential, in vitro invasion, cell growth curves, plate efficiency and S-phase cell numbers were higher in SW1990HM cells. Gene expression profiles of SW1990HM and SW1990 cells showed 40 metastasis-related genes expressed with a 3-fold difference. Thirteen of these 32.5% (13/40) were adhesion and extracellular-matrix related and twelve 30% (12/40) were cell growth and proliferation related, such as MMP10, MMP9, MMP7, CDH1, MGAT5, CTNNA1, IGF1, IL8RB, ITGA7, MDM2, MET, SSTR2 and VEGF, which were related to the onset and progression of tumor metastasis. Thus, SW1990HM is an attractive model to study metastasis and identify potential therapeutic targets.

Dynamic changes in messenger RNA profiles of bovine endometrium during the oestrous cycle

During the oestrous cycle, the bovine endometrium exhibits characteristic morphological and functional changes, which are mainly induced by progesterone (P(4)), oestrogens and oxytocin. We studied the response of the endometrium to this changing hormonal environment at the transcriptome level using a custom-made cDNA microarray. Endometrium samples were recovered from Simmental heifers on days 0 (oestrus), 3.5 (metoestrus), 12 (dioestrus) and 18. The latter group was divided into animals with high (late dioestrus) and low P(4) levels (preoestrus). Significance analysis of microarrays revealed 269 genes exhibiting significant changes in their transcript levels during the oestrous cycle in distinct temporal patterns. Two major types of expression profiles were observed, which showed the highest mRNA levels during the oestrus phase or the highest levels during the luteal phase respectively. A minor group of genes exhibited the highest mRNA levels on day 3.5. Gene ontology (GO) analyses revealed GO categories related to extracellular matrix remodelling, transport, and cell growth and morphogenesis enriched at oestrus, whereas immune response and particular metabolic pathways were overrepresented at dioestrus. Generation of gene interaction networks uncovered the genes possibly involved in endometrial remodelling (e.g. collagen genes, TNC, SPARC, MMP2, MEP1B, TIMP1, TIMP2, HTRA1), regulation of angiogenesis (e.g. ANGPTL2, TEK, NPY, AGT, EPAS1, KLF5 ), regulation of invasive growth (e.g. PCSK5, tight junction proteins, GRP, LGALS1, ANXA2, NOV, PLAT, MET, TDGF1, CST6, ITGB4), cell adhesion (e.g. MUC16, LGALS3BP) and embryo feeding (e.g. SLC1A1, SLC11A2, SLC16A1, SEPP1, ENPP1). Localisation of mRNA expression in the endometrium was analysed for CLDN4, CLDN10, TJP1, PCSK5, MAGED1, and LGALS1.