NDRG1 Expression Research Articles

NDRG3 is an androgen regulated and prostate enriched gene that promotes in vitro and in vivo prostate cancer cell growth

NDRG3 belongs to the N-myc down-regulated gene (NDRG) family that contains 4 paralogs: NDRG1, -2, -3 and -4. The function of NDRG3 and its relationship to cancer has not been studied. We herein report our examination of the expression and biological roles of NDRG3 in prostate cancers. We showed that NDRG3 expression is enriched in testis and prostate using gene expression data derived from massively parallel signature sequencing from 33 different human organs. We further showed that NDRG3 is expressed in both epithelial prostate cancer cells and prostatic stromal cells at both mRNA and proteins levels. We demonstrated that NDRG1 is significantly up-regulated by androgen in LNCaP cells. Over-expression of NDRG3 in stably transfected PC-3 cells increased their growth rates and migration capabilities when compared to parental or mock empty vector transfected PC-3 cells. In addition, we found that overexpresson of NDRG3 promoted the growth of xenograft tumors in nude mice. Finally, we found that NDRG3 expression was detected in 58.6% (41/70) of prostate cancer specimens compared to 13.2% (5/38) of benign prostatic hyperplasia specimens by immunohistochemistry. We showed by microarray and by RT-PCR that NDRG3 overexpression up-regulates the expression of many angiogenic chemokines including CXCL1 (chemokine ligand 1), CXCL3 (chemokine ligand 3) and CXCL5 (chemokine ligand 5), which may increase angiogenesis of tumors. Taken together, these results demonstrate that NDRG3 is a tumor promoter, the overexpression of which may contribute to the malignant phenotype of tumors.

Reduced expression of N-Myc downstream-regulated gene 2 in human thyroid cancer

BackgroundNDRG2 (N-Myc downstream-regulated gene 2) was initially cloned in our laboratory. Previous results have shown that NDRG2 expressed differentially in normal and cancer tissues. Specifically, NDRG2 mRNA was down-regulated or undetectable in several human cancers, and over-expression of NDRG2 inhibited the proliferation of cancer cells. NDRG2 also exerts important functions in cell differentiation and tumor suppression. However, it remains unclear whether NDRG2 participates in carcinogenesis of the thyroid.MethodsIn this study, we investigated the expression profile of human NDRG2 in thyroid adenomas and carcinomas, by examining tissues from individuals with thyroid adenomas (n = 40) and carcinomas (n = 35), along with corresponding normal tissues. Immunohistochemistry, quantitative RT-PCR and western blot methods were utilized to determine both the protein and mRNA expression status of Ndrg2 and c-Myc.ResultsThe immunostaining analysis revealed a decrease of Ndrg2 expression in thyroid carcinomas. When comparing adenomas or carcinomas with adjacent normal tissue from the same individual, the mRNA expression level of NDRG2 was significantly decreased in thyroid carcinoma tissues, while there was little difference in adenoma tissues. This differential expression was confirmed at the protein level by western blotting. However, there were no significant correlations of NDRG2 expression with gender, age, different histotypes of thyroid cancers or distant metastases.ConclusionOur data indicates that NDRG2 may participate in thyroid carcinogenesis. This finding provides novel insight into the important role of NDRG2 in the development of thyroid carcinomas. Future studies are needed to address whether the down-regulation of NDRG2 is a cause or a consequence of the progression from a normal thyroid to a carcinoma.

Study on NDRG3 in Mesenchyma of Prostate

Objective To study expression of NDRG3 in prostatic mesenchyma and effect of exogenous NDRG3 on prostatic stromal cells. Methods Immunohistochemical analysis was used to check expression of NDRG3 in prostate mesnenchyma. The WPMY-1 prostate immortalized mesenchyma cell line was stably-transfected with a NDRG3 gene expression vector. The NDRG3-stable transfected WPMY-1 sublines were studied along with parental and empty vector transfected WPMY-1 cells as controls. RT-PCR technology was applied to identity downstream gene expression under regulation of NDRG3 expression. Results Expression of DNRG3 was observed in prostate cancer mesenchyma, over-expression of NDRG3 in WPMY-1 cell up-regulated expression of chemotatic factors-CXCL3 and CXCL5. Conclusion Expression of stromal NDRG3 in prostate cancer specimens is significantly higher than that in benign prostatic hypertrophy (BPH) sample. There is a remarkable difference between the two groups of samples, NDRG3 may be related to angiogenesis in prostatic mesenchyma.

Mapping and Expression Analysis of Chicken NDRG1 and NDRG3 Genes

N-myc downstream-regulated genes 1 and 3 (NDRG1 and NDRG3) are members of the alpha/beta hydrolase superfamily. Phylogenetic analysis of the family demonstrated that human NDRG1 and 3 belong to a subfamily. The mapping and gene expression patterns of these genes represent one step toward further investigation into their possible roles in the chicken (Gallus gallus). To map these genes in the chicken chromosome, a 6000 rads chicken-hamster radiation hybrid panel (ChickRH6) was used. Primers were designed according to the published human sequences for amplification of those two genes. We compared the corresponding human mRNA sequences with the predicted coding sequences of the chicken NDRG1 and 3 genes and found that the assembled contigs shared a high percentage of similarity with the human genes. PCR of samples from ChickRH6 revealed that the locations of NDRG1 and 3 are linked to the markers MYC (58 cRs away, LOD score 4.52) and SEQ0265 (10 cRs away, LOD score 17.81), respectively. This result adds two new markers to the chicken RH map, and it reinforces that the RH technique is indeed a powerful tool for mapping genes due to its rapidity, precision, convenience, and reproducibility. In addition, we detected the gene expression and distribution of chicken NDRG1 and 3 in seven tissues, including heart, liver, spleen, lung, muscle, brain, and thymus, by RT-PCR, and found that NDRG1 is relatively ubiquitously expressed in all the tested tissues and highly expressed in heart and liver, whereas NDRG3 is high in heart, muscle, and brain.

Altered NDRG1 expression in breast cell lines influences apoptosis

Our objective was to detect variations of ovarian vascularization that occur in the estrus cycle of the ewe using an IV contrast agent. Five ewes were investigated using contrast-enhanced power Doppler after Sonovue® injection at day 0, 3, 5, 10 and 13 of the cycle in two successive estrus cycles. Transvaginal ultrasound monitoring of each ewe was performed after a dose of Sonovue®. Parameters derived from the time-intensity curves were compared. Quantification of the enhancement and wash-in period parameters changed significantly between ovaries and between the follicular and luteal periods of the cycle. Uptake time, wash-out time, total time of enhancement and area under the curve were the parameters with the smallest variation between ovaries. Wash-out time and area under the curve are two contrast parameters that did not change with cyclic changes. Thus, using these parameters in premenopausal women will allow more accurate detection of vascular modifications that may be associated with ovarian cancer. (E-mail: [email protected])

Immunohistochemical detection of Ndrg2 in the mouse nervous system

NDRG2, a member of the N-myc downstream-regulated gene (NDRG) family, is involved in cell differentiation and development. However, the distribution and function of Ndrg2 in the central nervous system remains unclear. Here, we analyzed the expression and distribution of Ndrg2 in the mouse brain and explored the potential physiological functions of Ndrg2. Ndrg2 was expressed in different regions of the brain, including the cerebral cortex, olfactory bulb, midbrain, hippocampus, and thalamus, with high levels in the midbrain and thalamus. Immunohistochemistry assay revealed that Ndrg2-positive cells distributed widely in the adult mouse brain and some of them showed nuclear staining. Indirect immunofluorescence and confocal microscopy studies showed that Ndrg2 protein colocalized with glial fibrillary acidic protein, indicating that Ndrg2 is expressed in astrocytes. Furthermore, Ndrg2 expression increased in glioma cells that were differentiating into astrocytes. Taken together, these findings suggest that Ndrg2 is possibly associated with glial cell proliferation and differentiation based on its immunolocalization in this study.

The relationship between NDRG1 gene and differentiation level and metastasis in prostate cancer

Objective To investigate the expression of NDRG1 and its relationship to differentiation level and metastasis in prostate cancer. Methods The expression NDRG1 was examined by immunohistochemistry LSAB method in 86 samples of prostate cancer and benigh prostate hyperplasia. Results The NDRG1 was shown to be highly expressed in 30(73.3%)of prostate cancer and 70.0%of benign prostate hyperplasia.There were no evident difference between prostate cancer and prestate hyperplasia(P＞0.05).The expression of NDRG1 was gradually reduction with the Gleason score from 2-4 to 5-7 to 8-10 in prostate cancer, which was statistical significance(P＜0.05).The expression of NDRG1 in lymph node or bone metastasis was significantly lower than that in no metastasis of prostate cancer. There was a negative correlation between the expression of NDRG1 and lymph node or bone metastasis. The age had no correlation with the expression of NDRG1(P＞0.05).Conclusion NDRG1 is involved in the genesis and development of prostate cancer, which may be related to the differentiation level of prostate cancer and serve as a useful marker for early diagnosis of cancer and metastasis. Key words: Proto-oncogene proteins c-myc; Prostatic neoplasms; Neoplasm metastasis

Human differentiation-related gene NDRG1 is a Myc downstream-regulated gene that is repressed by Myc on the core promoter region

N-Myc downstream-regulated gene 1 ( ndrg1) is up-regulated in N-Myc knockout mouse embryos. The human NDRG family consists of 4 highly homologous members and human Ndrg1 exhibits approximately 94% homology with mouse ndrg1. However, the regulatory mechanism of NDRG1 via Myc repression is as yet unknown. We previously identified human NDRG2 and demonstrated that this gene is transcriptionally down-regulated by Myc via Miz-1-dependent interaction with the core promoter region of NDRG2. Here, we provide evidence that human NDRG1 is regulated by Myc in a manner similar to NDRG2. We found that Ndrg1 expression levels were enhanced as Myc expression declined in differentiated cells, but were down-regulated following Myc induction. The data revealed that both N-Myc and c-Myc can repress human NDRG1 at the transcriptional level. We further determined that the core promoter region of human NDRG1 is required for Myc repression, and verified the interaction of Myc with the core promoter region. However, the presence of the protein synthesis inhibitor cycloheximide could reverse the repression of Myc, indicating the indirect repression of human NDRG1 by Myc. Moreover, we found that c-Myc-mediated repression can be inhibited by TSA, an HDACs inhibitor, which suggests the involvement of HDACs in the repression process. Taken together, our results demonstrate that, in common with NDRG2, human NDRG1 can be indirectly transcriptionally down-regulated by Myc via interaction with the NDRG1 core promoter.

Expression of NDRG2 in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (CCRCC) is the most common pathological type of renal cell carcinoma and the main cause of renal carcinoma mortality. NDRG2, a new member of the N-Myc downstream-regulated gene (NDRG) family, is a focus for study at present. Up to now, its expression and function in carcinoma remain unclear. The aim of this study was to investigate its expression in CCRCC tissues and several renal carcinoma cell lines. The expression of NDRG2 was evaluated in renal cell carcinoma cell lines, tumor and adjacent non-tumor tissues from same clear cell renal cell carcinoma patients, by using immunohistochemistry, immunofluorescence, RT-PCR and Western blot. By immunohistochemistry and immunofluorescence we found that NDRG2 was predominantly located in the cytoplasm and membrane of renal carcinoma cancer cells, and the positive rate of NDRG2 in renal carcinoma specimens was 30.3% (40/132), which is significantly lower than 91.67% (121/132) in normal renal tissues (p<0.01). The average staining score in normal renal tissues was significantly higher than renal carcinoma (6.12+/-1.84 versus 2.65+/-1.23, p<0.01). Moreover, NDRG2 mRNA and protein were down-regulated in 6 fresh CCRCC tissues compared with their adjacent noncancerous tissues and normal tissues. Its expression was also lower in the human CCRCC-derived cell lines A-498 and 786-O than in the human proximal tubular cell lines HK-2 and HKC. These results indicated that NDRG2 might play an important role in the carcinogenesis and development of CCRCC and may function as a tumor suppressor in CCRCC.

Alteration of Gene Expression Induced by Silurus asotus Lectin in Burkitt's Lymphoma Cells

Silurus asotus lectin (SAL) is a member of the rhamnose-binding lectin (RBL) family, and recognizes globotriaosylceramide (Gb3) on the cell surface of Burkitt's lymphoma cell lines, such as Raji and Daudi cells. The variation of gene expression in the treatment of both cells with SAL was analyzed using the differential display (DD) method with combination of 16 kinds of arbitary primers and 3 kinds of anchor primers. Treatment of Raji cells with SAL down-regulated mitochondria-associated granulocyte-macropharge colony-stimulating factor (GM-CSF) signaling molecule (Magmas) gene, and up-regulated N-myc downstream regulated gene (NDRG) 3. On the other hand, treatment of Daudi cells with SAL down-regulated Rad50 gene. Since Magmas gene expression was repressed in SAL-treated Raji cells, but did not change in SAL-treated D-threo-1-phenyl-2-decanoylamino-3-morphorino-1-propanol (PDMP)-pretreated Raji cells, it was clear that the expression of Magmas, NDRG3 or Rad50 was regulated by SAL binding to Gb3.

Expression of NDRG2 is down-regulated in high-risk adenomas and colorectal carcinoma

BackgroundIt has recently been shown that NDRG2 mRNA is down-regulated or undetectable in several human cancers and cancer cell-lines. Although the function of NDRG2 is unknown, high NDRG2 expression correlates with improved prognosis in high-grade gliomas. The aim of this study has been to examine NDRG2 mRNA expression in colon cancer. By examining affected and normal tissue from individuals with colorectal adenomas and carcinomas, as well as in healthy individuals, we aim to determine whether and at which stages NDRG2 down-regulation occurs during colonic carcinogenesis.MethodsUsing quantitative RT-PCR, we have determined the mRNA levels for NDRG2 in low-risk (n = 15) and high-risk adenomas (n = 57), colorectal carcinomas (n = 50) and corresponding normal tissue, as well as control tissue from healthy individuals (n = 15). NDRG2 levels were normalised to β-actin.ResultsNDRG2 mRNA levels were lower in colorectal carcinomas compared to normal tissue from the control group (p < 0.001). When comparing adenomas/carcinomas with adjacent normal tissue from the same individual, NDRG2 expression levels were significantly reduced in both high-risk adenoma (p < 0.001) and in colorectal carcinoma (p < 0.001). There was a trend for NDRG2 levels to decrease with increasing Dukes' stage (p < 0.05).ConclusionOur results demonstrate that expression of NDRG2 is down-regulated at a late stage during colorectal carcinogensis. Future studies are needed to address whether NDRG2 down-regulation is a cause or consequence of the progression of colorectal adenomas to carcinoma.

Egr-1 Mediates Hypoxia-Inducible Transcription of the NDRG1 Gene through an Overlapping Egr-1/Sp1 Binding Site in the Promoter

N-myc down-regulated gene 1 (NDRG1/Cap43) is inducible by a variety of environmental stressors, including hypoxia. The present study identified a cis-acting element mediating the transactivation of the NDRG1 gene in murine RAW264.7 macrophage cells treated with hypoxia or deferoxamine, an iron chelator mimicking hypoxia. Through a series of deletions of the promoter of NDRG1 luciferase constructs, a minimal cis-acting element conferring inducibility by hypoxia and deferoxamine was localized to an early growth response 1 (Egr-1) and Sp1 overlapping binding site. Electrophoretic mobility shift assay, antibody supershift assay, and mutations of the Egr-1 binding site confirmed the specific binding of Egr-1 protein to this Egr-1/Sp1 motif. In addition, hypoxia increased the level of Egr-1 protein that correlated with induction of NDRG1 expression at both RNA and protein levels. Transient transfection of the Egr-1 gene into HeLa cells also resulted in up-regulation of the NDRG1 mRNA. The role of Egr-1 was further verified by mutations in the Egr-1 binding site, which reduced promoter inducibility by hypoxia and deferoxamine. Furthermore, the induction of NDRG1 expression by hypoxia and deferoxamine was diminished by RNA interference knockdown of Egr-1 gene expression and in Egr-1-/- mouse embryonic fibroblasts (MEF) compared with Egr-1+/- MEFs. These results showed for the first time that Egr-1 regulates NDRG1 transcription through an overlapping Egr-1/Sp1 binding site that acts as a major site of positive regulation of the NDRG1 promoter by hypoxia signaling.

SOCS1 induced by NDRG2 expression negatively regulates STAT3 activation in breast cancer cells

Although NDRG2 inactivation has recently been found to have an important role in some tumorigenesis, its role in intracellular signal transduction pathways remains poorly defined. In the present study, we demonstrate that NDRG2 overexpression in malignant breast cancer cells specifically inhibits Akt phosphorylation and induces phosphorylation of p38 MAP kinase and SAPK/JNK. In addition, we investigated whether NDRG2 expression affects JAK/STAT- or mitogen-activated protein kinase-mediated signal activation. JAK2 or STAT3 activation in both resting and IGF-stimulating cells was remarkably inhibited by NDRG2 expression. Furthermore, NDRG2 has been found to highly up-regulate the expression level of SOCS1 mRNA and protein. We have found that NDRG2 was able to regulate cytokine signaling in breast cancer cells through the regulation of SOCS1 expression. Finally, inhibition of p38 MAPK activity blocked the induction of SOCS1 expression by NDRG2, resulting in the recovery of STAT3 phosphorylation level. Together, these data demonstrate that NDRG2 expression in breast cancer cells is able to inhibit STAT3 activation via SOCS1 induction in a p38 MAPK dependent manner, implicating NDRG2 as a growth inhibitory gene in signal transduction pathways of breast tumor cells.

Zoledronic acid induces anti-cancer effects on prostate cancer cells through the modulation of the angiogenesis associated CYR61 and the androgen-differentiation associated NDRG-1 genes

21079 Background: Aminobisphosphonates (ABPs) has a definite direct anti-tumour activity but a limited activity in vivo. Their molecular targets are still not completely defined. Therefore, we have studied the effects of zoledronic acid (ZOL) addition to prostate cancer PC3 cells on gene expression profile. Methods: We have treated PC3 cells with 100 μM ZOL for 24 hours, extracted mRNAs and probed on Affimetrix HG-U133. Thereafter, we have identified down modulated and upregulated genes and checked for modulation of mRNA with RT PCR and of the relative encoded proteins with western blotting. Results: We have found 6 down modulated and 32 upregulated genes. We have focused our attention on NDRG1 associated to the androgen-differentiation and on Cysteine rich 61 (CYR61) involved in the regulation of proliferation and angiogenesis. NDRG1 mRNA was up-regulated and CYR61 mRNA was downregulated by ZOL in a dose-dependent manner. Similar effects were observed at protein product levels with an about 2-fold change recorded already in cells treated with 50 μM ZOL. Interestingly, also Gefitinib, Sorafenib and Tipifarnib used at their IC:50s could induce changes in both NDRG1 and CYR61 expression, but 50 μM ZOL was about 2-fold more potent. On the other hand, cytotoxic agents such as docetaxel did not have any effect. The addition of farnesol (FOH) or geranylgeraniol (GGOH) to ZOL-treated cells was able to counteract the effect of ZOL on CYR61 expression partially or completely, respectively. On the other hand, both FOH and GGOH had poor effect on the regulation of NDRG1 expression induced by ZOL. Conclusions: ZOL induces a strong regulation of the expression of NDRG1 and CYR61 at both mRNA and protein levels that appears to be dose-dependent and specific. CYR61 modulation seems to be more dependent from the inhibition of geranylgeranylation processes while NDRG1 changes could be at least in part independent from the inhibition of isoprenylation induced by ZOL. The study of the biological relevance of these effects on the anti-cancer effects of ZOL is ongoing with small interference RNA approaches. No significant financial relationships to disclose.

Proteomics Analysis of the Interactome of N-myc Downstream Regulated Gene 1 and Its Interactions with the Androgen Response Program in Prostate Cancer Cells

NDRG1 is known to play important roles in both androgen-induced cell differentiation and inhibition of prostate cancer metastasis. However, the proteins associated with NDRG1 function are not fully enumerated. Using coimmunoprecipitation and mass spectrometry analysis, we identified 58 proteins that interact with NDRG1 in prostate cancer cells. These proteins include nuclear proteins, adhesion molecules, endoplasmic reticulum (ER) chaperons, proteasome subunits, and signaling proteins. Integration of our data with protein-protein interaction data from the Human Proteome Reference Database allowed us to build a comprehensive interactome map of NDRG1. This interactome map consists of several modules such as a nuclear module and a cell membrane module; these modules explain the reported versatile functions of NDRG1. We also determined that serine 330 and threonine 366 of NDRG1 were phosphorylated and demonstrated that the phosphorylation of NDRG1 was prominently mediated by protein kinase A (PKA). Further, we showed that NDRG1 directly binds to beta-catenin and E-cadherin. However, the phosphorylation of NDRG1 did not interrupt the binding of NDRG1 to E-cadherin and beta-catenin. Finally, we showed that the inhibition of NDRG1 expression by RNA interference decreased the ER inducible chaperon GRP94 expression, directly proving that NDRG1 is involved in the ER stress response. Intriguingly, we observed that many members of the NDRG1 interactome are androgen-regulated and that the NDRG1 interactome links to the androgen response network through common interactions with beta-catenin and heat shock protein 90. Therefore we overlaid the transcriptomic expression changes in the NDRG1 interactome in response to androgen treatment and built a dual dynamic picture of the NDRG1 interactome in response to androgen. This interactome map provides the first road map for understanding the functions of NDRG1 in cells and its roles in human diseases, such as prostate cancer, which can progress from androgen-dependent curable stages to androgen-independent incurable stages.

Hypoxia increases cytoplasmic expression of NDRG1, but is insufficient for its membrane localization in human hepatocellular carcinoma

NDRG1 is a hypoxia-inducible protein, whose modulated expression is associated with the progression of human cancers. Here, we reveal that NDRG1 is markedly upregulated in the cytoplasm and on the membrane in human hepatocellular carcinoma (HCC). We demonstrate further that hypoxic stress increases the cytoplasmic expression of NDRG1 in vitro, but does not result in its localization on the plasma membrane. However, grown within an HCC-xenograft in vivo, cells express NDRG1 in the cytoplasm and on the plasma membrane. In conclusion, hypoxia is a potent inducer of NDRG1 in HCCs, albeit requiring additional stimuli within the tumour microenvironment for its recruitment to the membrane.

A Study for Expression and Biological Function of N-myc Downstream Regulated Gene 2 in Breast Cancer

Purpose: It is important to identify a potential tumor marker that is associated with pathophysiologic processes of breast cancer. N-Myc downstream regulated genes (NDRG) are composed of four subtypes (NDRG 1-4) and NDRG2 gene has been reported as a specifically expressed gene in the human solid tumor including breast cancer. Although NDRG2 inhibits cell proliferation and promote differentiation, the molecular basis of the tumor-suppressor activity of NDRG2 in breast cancer is unknown. Herein, we tried to reveal the correlations between the expression of NDRG2 and the various clinicopathologic prognostic factors and evaluate its functional and pathophysiological roles in tumorigenesis of breast cancer. Methods: We were obtained the 67 breast cancers and paired normal tissue samples from patients who operated for breast cancer between June 2002 and June 2004. The expression of NDRG2 were measured with immunohistochemistry using monoclonal antibody and it was used eukaryotic transfection to manipulate the expression in MDAMB-231 breast cancer cell line. Cell proliferation analysis were evaluated with trypan blue stain and status of differentially-expressed genes by NDRG2 overexpression were investigated with oligo microarray chip analysis. Results: Significant difference of NDRG2 mRNA expression between breast cancer and normal tissue was not detected. However, NDRG2 was significantly down-regulated in breast cancer tissue, compared to normal tissue (p<0.0001). It was a inverse-correlation between the NDRG2 expression and tumor size, histologic grade although other clinicopathological parameters such as axillary lymph node metastasis were not correlated. Overexpression of NDRG2 in MDA-MB231 cell showed a decrease of cell proliferation compared with Mock control. Of the 24,000 genes, 64 genes were increased in expression while 256 genes including cyclin D1 were repressed by NDRG2 overexpression. Conclusion: Our results suggest that NDRG2 can function as a regulator of cell differentiation and cell cycle (as a tumor suppressor gene) in the early stage of breast cancer. In addition, NDRG2 protein indicates a prognostic tumor marker for breast cancer.

Direct evidence for neuronal differentiation of astrocyte-like progenitors in the postnatal hippocampus

N-myc downstream-regulated gene 2 (Ndrg2) is a differentiation- and stress-associated molecule predominantly expressed in astrocytes in the central nervous system (CNS). To study the expression and possible role of Ndrg2 in quiescent and activated astrocytes, mice were administrated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropypridine (MPTP), a Parkinson disease (PD)-related neurotoxin which causes both neurodegeneration and glial activation. Immunohistological analysis revealed that Ndrg2 was highly expressed in both types of astrocytes, but less so in astrocytes during the early process of activation. Ndrg2 was also expressed in astrocyte-like cells, but not in neurons, in human brains from PD and Cortico-basal degeneration (CBD) patients. In cultured astrocytes, gene silencing of Ndrg2 significantly enhanced the numbers of 5-bromo-2′-deoxy-uridine (BrdU)-incorporated and proliferating cell nuclear antigen (PCNA)-positive cells, and reduced the length of cell processes and the amount of F-actin. In contrast, adenovirus-mediated overexpression of Ndrg2 significantly reduced the numbers of BrdU-incorporated and PCNA-positive cells, and enhanced the amount of F-actin. Fractionation and immunocytochemical analysis further revealed that Ndrg2 was located in different cellular fractions including the cytosol and cell surface membranes. These results suggest that Ndrg2 may regulate astroglial activation through the suppression of cell proliferation and stabilization of cell morphology.

The Repression of Human Differentiation-related Gene NDRG2 Expression by Myc via Miz-1-dependent Interaction with the NDRG2 Core Promoter

The N-myc downstream-regulated gene 1 (ndrg1) is highly expressed in N-myc knock-out mice through an unknown regulatory mechanism. As one member of the human NDRG gene family, NDRG2 encodes a protein highly homologous to Ndrg1. However, it is uncertain whether the expression of human NDRG2 is regulated by Myc because mouse ndrg2 and -3 are not affected by Myc. In this study, we provide the novel evidence that the expression of human NDRG2 is down-regulated by Myc via transcriptional repression. A high level of NDRG2 was observed as Myc expression was reduced in differentiated cells, whereas a low level of NDRG2 was shown following increased Myc expression upon serum stimulation. The ectopic expression of c-Myc dramatically reduces the cellular Ndrg2 protein and mRNA level. We further identified the core promoter region of NDRG2 that is required for Myc repression on NDRG2 transcription, and we verified the interaction of Myc with the core promoter region both in vitro and in vivo. Moreover, the c-Myc-mediated repression of NDRG2 requires association with Miz-1, and possibly the recruitment of other epigenetic factors, such as histone deacetylases, to the promoter. The regulatory function of Myc on NDRG2 gene expression implicated the role of the Ndrg2 in regulating cell differentiation.

Decreased expression of Ndrg1 is correlated with tumor progression and poor prognosis in patients with esophageal squamous cell carcinoma

NDRG1 (N-myc downstream regulated gene-1) was reported to be necessary for p53-mediated apoptosis and to be regulated by PTEN (phosphatase and tensin homolog). In several cancers, it was suggested to be a tumor suppressor gene. Its significance in esophageal squamous cell carcinoma (ESCC) has not been studied. The objective of this study was to clarify the relation between clinicopathological and biologic factors in esophageal carcinoma and to determine the prognostic significance of the expression of NDRG1. Expression of NDRG1 mRNA was quantified by real-time reverse transcription polymerase chain reaction using a Lightcycler in 47 esophageal ESCC specimens. The data were analyzed with reference to clinicopathological factors. Among the esophageal cancer tissues, NDRG1 mRNA expression was significantly lower in tumors of more advanced pathological stage (0-I vs. II-IV; P = 0.0027) and local tumor invasion (T1-2 vs. T3-4; P = 0.0136). Patients who had low NDRG1 mRNA expression had a significantly shorter survival after surgery compared with patients who had high NDRG1 mRNA expression (log-rank test, P = 0.0478). Impaired NDRG1 expression may lead to more aggressive invasion of ESCC.