N-myc Downstream-regulated Gene 1 (NDRG1) a Differentiation Marker of Human Breast Cancer

NDRGs in Breast Cancer: A Review and In Silico Analysis

The N-myc downstream regulated gene family (NDRGs) includes four members: NDRG1, NDRG2, NDRG3, and NDRG4. These members exhibit 53-65% amino acid identity. The role of NDRGs in tumor growth and metastasis appears to be tumor- and context-dependent. While many studies have reported that these family members have tumor suppressive roles, recent studies have demonstrated that NDRGs, particularly NDRG1 and NDRG2, function as oncogenes, promoting tumor growth and metastasis. Additionally, NDRGs are involved in regulating different signaling pathways and exhibit diverse cellular functions in breast cancers. In this review, we comprehensively outline the oncogenic and tumor suppressor roles of the NDRG family members in breast cancer, examining evidence from in vitro and in vivo breast cancer models as well as tumor tissues from breast cancer patients. We also present analyses of publicly available genomic and transcriptomic data from multiple independent cohorts of breast cancer patients.

A review on the role of NDRG1 in different cancers

NDRG1 is a member of the α/β hydrolase superfamily that resides in the cytoplasm and participates in the stress responses, hormone response, cell growth, and differentiation. Several studies have pointed to the importance of NDRG1 in the carcinogenesis. This gene has been found to be up-regulated in an array of cancer types such as bladder, esophageal squamous cell carcinoma, endometrial, lung and liver cancers, but being down-regulated in other types of cancers such as colorectal, gastric and ovarian cancers. The current study summarizes the evidence on the role of NDRG1 in the carcinogenic processes in different types of tissues.

Re-Shaping the Pancreatic Cancer Tumor Microenvironment: A New Role for the Metastasis Suppressor NDRG1

Pancreatic cancer (PaC) is a highly aggressive disease, with poor response to current treatments and 5-year survival rates of 10-15%. PaC progression is facilitated by its interaction with the complex and multifaceted tumor microenvironment (TME). In the TME, cancer cells and surrounding stromal cells constantly communicate with each other via the secretion and uptake of factors including cytokines, chemokines, growth factors, metabolites, and extracellular vesicles (EVs), reshaping the landscape of PaC. Recent studies demonstrated that the metastasis suppressor N-myc downstream regulated 1 (NDRG1) not only inhibits oncogenic signaling pathways in PaC cells but also alters the communication between PaC cells and the surrounding stroma. In fact, NDRG1 was found to influence the secretome of PaC cells, alter cancer cell metabolism, and interfere with intracellular trafficking and intercellular communication between PaC cells and surrounding fibroblasts. This review will present recent advancements in understanding the role of NDRG1 in PaC progression, with a focus on how this molecule influences PaC-stroma communication and its potential for re-shaping the PaC TME.

NDRG1 in Cancer: A Suppressor, Promoter, or Both?

N-myc downregulated gene-1 (NDRG1) has been variably reported as a metastasis suppressor, a biomarker of poor outcome, and a facilitator of disease progression in a range of different cancers. NDRG1 is poorly understood in cancer due to its context-dependent and pleiotropic functions. Within breast cancer, NDRG1 is reported to be either a facilitator of, or an inhibitor of tumour progression and metastasis. The wide array of roles played by NDRG1 are dependent on post-translational modifications and subcellular localization, as well as the cellular context, for example, cancer type. We present an update on NDRG1, and its association with hallmarks of cancer such as hypoxia, its interaction with oncogenic proteins such as p53 as well its role in oncogenic and metastasis pathways in breast and other cancers. We further comment on its functional implications as a metastasis suppressor and promoter, its clinical relevance, and discuss its therapeutic targetability in different cancers.

NDRG1 in Aggressive Breast Cancer Progression and Brain Metastasis

BACKGROUND

N-Myc downstream regulated gene 1 (NDRG1) suppresses metastasis in many human malignancies, including breast cancer, yet has been associated with worse survival in patients with inflammatory breast cancer. The role of NDRG1 in the pathobiology of aggressive breast cancers remains elusive.

METHODS

To study the role of NDRG1 in tumor growth and brain metastasis in vivo, we transplanted cells into cleared mammary fat pads or injected them in tail veins of SCID/Beige mice (n = 7-10 per group). NDRG1 protein expression in patient breast tumors (n = 216) was assessed by immunohistochemical staining. Kaplan-Meier method with 2-sided log-rank test was used to analyze the associations between NDRG1 and time-to-event outcomes. A multivariable Cox regression model was used to determine independent prognostic factors. All statistical tests were 2-sided.

RESULTS

We generated new sublines that exhibited a distinct propensity to metastasize to the brain. NDRG1-high-expressing cells produced more prevalent brain metastases (100% vs 44.4% for NDRG1-low sublines, P = .01, Fisher's exact test), greater tumor burden, and reduced survival in mice. In aggressive breast cancer cell lines, silencing NDRG1 led to reduced migration, invasion, and tumor-initiating cell subpopulations. In xenograft models, depleting NDRG1 inhibited primary tumor growth and brain metastasis. In patient breast tumors, NDRG1 was associated with aggressiveness: NDRG1-high expression was also associated with shorter overall survival (hazard ratio [HR] = 2.27, 95% confidence interval [95% CI] = 1.20 to 4.29, P = .009) and breast cancer-specific survival (HR = 2.19, 95% CI = 1.07 to 4.48, P = .03). Multivariable analysis showed NDRG1 to be an independent predictor of overall survival (HR = 2.17, 95% CI = 1.10 to 4.30, P = .03) and breast cancer-specific survival rates (HR = 2.27, 95% CI = 1.05 to 4.92, P = .04).

CONCLUSIONS

We demonstrated that NDRG1 drives tumor progression and brain metastasis in aggressive breast cancers and that NDRG1-high expression correlates with worse clinical outcomes, suggesting that NDRG1 may serve as a therapeutic target and prognostic biomarker in aggressive breast cancers.

N-myc downstream regulated family member 1 (NDRG1) is enriched in myelinating oligodendrocytes and impacts myelin degradation in response to demyelination

The N-myc downstream regulated gene family member 1 (NDRG1) is a gene whose mutation results in peripheral neuropathy with central manifestations. While most of previous studies characterized NDRG1 role in Schwann cells, the detection of central nervous system symptoms and the identification of NDRG1 as a gene silenced in the white matter of multiple sclerosis brains raise the question regarding its role in oligodendrocytes. Here, we show that NDRG1 is enriched in oligodendrocytes and myelin preparations, and we characterize its expression using a novel reporter mouse (TgNdrg1-EGFP). We report NDRG1 expression during developmental myelination and during remyelination after cuprizone-induced demyelination of the adult corpus callosum. The transcriptome of Ndrg1-EGFP+ cells further supports the identification of late myelinating oligodendrocytes, characterized by expression of genes regulating lipid metabolism and bioenergetics. We also generate a lineage specific conditional knockout (Olig1^cre/+ ;Ndrg1^fl/fl ) line to study its function. Null mice develop normally, and despite similar numbers of progenitor cells as wild type, they have fewer mature oligodendrocytes and lower levels of myelin proteins than controls, thereby suggesting NDRG1 as important for the maintenance of late myelinating oligodendrocytes. In addition, when control and Ndrg1 null mice are subject to cuprizone-induced demyelination, we observe a higher degree of demyelination in the mutants. Together these data identify NDRG1 as an important molecule for adult myelinating oligodendrocytes, whose decreased levels in the normal appearing white matter of human MS brains may result in greater susceptibility of myelin to damage.

Expanding Roles of De Novo Lipogenesis in Breast Cancer

In recent years, lipid metabolism has gained greater attention in several diseases including cancer. Dysregulation of fatty acid metabolism is a key component in breast cancer malignant transformation. In particular, de novo lipogenesis provides the substrate required by the proliferating tumor cells to maintain their membrane composition and energetic functions during enhanced growth. However, it appears that not all breast cancer subtypes depend on de novo lipogenesis for fatty acid replenishment. Indeed, while breast cancer luminal subtypes rely on de novo lipogenesis, the basal-like receptor-negative subtype overexpresses genes involved in the utilization of exogenous-derived fatty acids, in the synthesis of triacylglycerols and lipid droplets, and fatty acid oxidation. These metabolic differences are specifically associated with genomic and proteomic changes that can perturb lipogenic enzymes and related pathways. This behavior is further supported by the observation that breast cancer patients can be stratified according to their molecular profiles. Moreover, the discovery that extracellular vesicles act as a vehicle of metabolic enzymes and oncometabolites may provide the opportunity to noninvasively define tumor metabolic signature. Here, we focus on de novo lipogenesis and the specific differences exhibited by breast cancer subtypes and examine the functional contribution of lipogenic enzymes and associated transcription factors in the regulation of tumorigenic processes.

NDRG1 Expression Is an Independent Prognostic Factor in Inflammatory Breast Cancer

Simple Summary

Inflammatory breast cancer (IBC) is a rare and aggressive variant of breast cancer that is responsible for a significant number of breast cancer-related deaths. Herein, we describe how the expression of a specific protein named N-myc downstream-regulated gene 1 (NDRG1), commonly described as a gene that prevents the spread of cancer cells to distant organs, may have a paradoxical role in cancer progression in IBC. We found that the level of expression of NDRG1 in tumor tissues predicts the survival outcome of patients with IBC. We also observed that NDRG1, together with other important prognostic factors such as estrogen receptor status and stage, could be used to further analyze prognostic outcome or treatment response of patients.

Abstract

NDRG1 is widely described as a metastasis suppressor in breast cancer. However, we found that NDRG1 is critical in promoting tumorigenesis and brain metastasis in mouse models of inflammatory breast cancer (IBC), a rare but highly aggressive form of breast cancer. We hypothesized that NDRG1 is a prognostic marker associated with poor outcome in patients with IBC. NDRG1 levels in tissue microarrays from 64 IBC patients were evaluated by immunohistochemical staining with NDRG1 (32 NDRG1-low (≤median), 32 NDRG1-high (>median)). Overall and disease-free survival (OS and DSS) were analyzed with Kaplan–Meier curves and log-rank test. Univariate analysis showed NDRG1 expression, tumor grade, disease stage, estrogen receptor (ER) status, and receipt of adjuvant radiation to be associated with OS and DSS. NDRG1-high patients had poorer 10-year OS and DSS than NDRG1-low patients (OS, 19% vs. 45%, p = 0.0278; DSS, 22% vs. 52%, p = 0.0139). On multivariable analysis, NDRG1 independently predicted OS (hazard ratio (HR) = 2.034, p = 0.0274) and DSS (HR = 2.287, p = 0.0174). NDRG1-high ER-negative tumors had worse outcomes OS, p = 0.0003; DSS, p = 0.0003; and NDRG1-high tumors that received adjuvant radiation treatment had poor outcomes (OS, p = 0.0088; DSS, p = 0.0093). NDRG1 was a significant independent prognostic factor for OS and DSS in IBC patients. Targeting NDRG1 may represent a novel strategy for improving clinical outcomes for patients with IBC.

NDRG1 and FOXO1 regulate endothelial cell proliferation in infantile haemangioma

The etiopathogenesis of infantile haemangioma has not been well understood, and it is accepted that angiogenic mediator dysregulation is the main contributor to the abnormal haemangioma capillary formation. The role of NDRG1, a hypoxia-inducible protein; FOXOs, which are tumor suppressor proteins; and the mTOR complex 2 pathway in infantile haemangioma have not been studied yet. The purpose of this study was to investigate NDRG1 and FOXO1 expression in the infantile haemangioma and the correlation of these proteins with proliferation and involution. Primary endothelial cells were obtained, with parental agreement, from 12 infantile haemangioma patients during surgery; 6 patients had proliferating infantile haemangiomas and 6 had involuting IHs. We compared the infantile haemangioma tissues and primary endothelial cells with human vein endothelial cells using microarrays, real-time PCR, Western blotting and immunohistochemical staining. Our data indicated that FOXO1 expression was downregulated in proliferating infantile haemangioma tissue. We found that the expression of NDRG1, a molecule upstream of the FOXO1 pathway, increased during haemangioma proliferation. NDRG1 knockdown decreased haemangioma endothelial cell proliferation and downregulated c-MYC oncoprotein levels. Our findings suggest that NDRG1 positively regulates haemangioma proliferation. FOXO1 dysregulation plays an important role in infantile haemangiomas pathogenesis.

Oncogenic MNK signalling regulates the metastasis suppressor NDRG1

The protein N-myc down-regulated gene 1 (NDRG1) represses tumour metastasis. It is phosphorylated at several sites by serum and glucocorticoid-regulated kinase 1 (SGK1). Here we show that NDRG1 is also regulated by the oncogenic MAP kinase-interacting kinase (MNK) pathway, a target for cancer therapy.Inhibiting MNKs increases the expression of NDRG1 protein and mRNA in breast cancer cells. MNK inhibition also decreases the phosphorylation of NDRG1. Phosphorylation of NDRG1 is reduced in cells lacking MNK1, but not MNK2-knockout cells, indicating that NDRG1 phosphorylation is a specific target for MNK1. However, MNK1 cannot directly phosphorylate NDRG1 in vitro, indicating that additional signalling connections are involved. Taken together, our data indicate that MNK signaling regulates NDRG1 at transcriptional and post-translational levels.We show that SGK1 phosphorylates MNK1 at a conserved site, which represses its activity. NDRG1, SGK1 and the MNKs are implicated in cell migration and metastasis. As expected, knocking-down NDRG1 promoted cell migration. However, whereas MNK inhibition impairs these processes irrespective of NDRG1 levels, SGK inhibition only did so in NDRG1-depleted cells. Thus, MNKs and SGK affect migration/invasion through distinct mechanisms.Our data reveal several novel connections between signalling pathways important for tumour biology.

Effects of long-term low oxygen tension in human chondrosarcoma cells

The cell-based therapies could be potential methods to treat damaged cartilage tissues. Instead of native hyaline cartilage, the current therapies generate mainly weaker fibrocartilage-type of repair tissue. A correct microenvironment influences the cellular phenotype, and together with external factors it can be used, for example, to aid the differentiation of mesenchymal stem cells to defined types of differentiated adult cells. In this study, we investigated the effect of long-term exposure to 5% low oxygen atmosphere on human chondrosarcoma HCS-2/8 cells. This atmosphere is close to normal oxygen tension of cartilage tissue. The proteome was analyzed with label-free mass spectrometric method and further bioinformatic analysis. The qRT-PCR method was used to gene expression analysis, and ELISA and dimethylmethylene blue assays for type II collagen and sulfated glycosaminoglycan measurements. The 5% oxygen atmosphere did not influence cell proliferation, but enhanced slightly ACAN and COL2A1 gene expression. Proteomic screening revealed a number of low oxygen-induced protein level responses. Increased ones included NDUFA4L2, P4HA1, NDRG1, MIF, LDHA, PYGL, while TXNRD1, BAG2, TXN2, AQSTM1, TNFRSF1B, and EPHX1 decreased during the long-term low oxygen atmosphere. Also a number of proteins previously not related to low oxygen tension changed during the treatment. Of those S100P, RPSS26, NDUFB11, CDV3, and TUBB8 had elevated levels, while ALCAM, HLA-B, EIF1, and ACOT9 were lower in the samples cultured at low oxygen tension. In conclusion, low oxygen condition causes changes in the cellular amounts of several proteins.

WNT-1 inducible signaling pathway protein-1 enhances growth and tumorigenesis in human breast cancer

WNT1 inducible signaling pathway protein 1 (WISP1) plays a key role in many cellular functions in a highly tissue-specific manner; however the role of WISP1 in breast cancer is still poorly understood. Here, we demonstrate that WISP1 acts as an oncogene in human breast cancer. We demonstrated that human breast cancer tissues had higher WISP1 mRNA expression than normal breast tissues and that treatment of recombinant WISP1 enhanced breast cancer cell proliferation. Further, ectopic expression of WISP1 increased the growth of breast cancer cells in vitro and in vivo. WISP1 transfection also induced epithelial-mesenchymal-transition (EMT) in MCF-7 cells, leading to higher migration and invasion. During this EMT-inducing process, E-cadherin was repressed and N-cadherin, snail, and β-catenin were upregulated. Filamentous actin (F-actin) remodeling and polarization were also observed after WISP1 transfection into MCF-7 cells. Moreover, forced overexpression of WISP1 blocked the expression of NDRG1, a breast cancer tumor suppressor gene. Our study provides novel evidence that WISP1-modulated NDRG1 gene expression is dependent on a DNA fragment (-128 to +46) located within the human NDRG1 promoter. Thus, we concluded that WISP1 is a human breast cancer oncogene and is a potential therapeutic target.

Frequent MYC coamplification and DNA hypomethylation of multiple genes on 8q in 8p11-p12-amplified breast carcinomas

Genetic and epigenetic (DNA methylation, histone modifications, microRNA expression) crosstalk promotes inactivation of tumor suppressor genes or activation of oncogenes by gene loss/hypermethylation or duplications/hypomethylation, respectively. The 8p11-p12 chromosomal region is a hotspot for genomic aberrations (chromosomal rearrangements, amplifications and deletions) in several cancer forms, including breast carcinoma where amplification has been associated with increased proliferation rates and reduced patient survival. Here, an integrative genomics screen (DNA copy number, transcriptional and DNA methylation profiling) performed in 229 primary invasive breast carcinomas identified substantial coamplification of the 8p11-p12 genomic region and the MYC oncogene (8q24.21), as well as aberrant methylation and transcriptional patterns for several genes spanning the 8q12.1-q24.22 genomic region (ENPP2, FABP5, IMPAD1, NDRG1, PLEKHF2, RRM2B, SQLE, TAF2, TATDN1, TRPS1, VPS13B). Taken together, our findings suggest that MYC activity and aberrant DNA methylation may also have a pivotal role in the aggressive tumor phenotype frequently observed in breast carcinomas harboring 8p11-p12 regional amplification.

N-myc downstream regulated gene 1 acts as a tumor suppressor in ovarian cancer

Although implicated in a number of tumor types, the role of N-myc downstream regulated gene 1 (NDRG1) in ovarian cancer (OC) is unclear. In the present study, we used short hairpin RNA (shRNA) to silence NDRG1 in the OC cell line OVCAR3 and assessed the effect of its knockdown on cell morphology, proliferation, colony formation, migration and invasion. To complement these knockdown studies, we overexpressed NDRG1 in the same cell line. We found that NDRG1 knockdown significantly enhanced OVCAR3 proliferation, migration and invasion; however, there were no apparent changes in cell morphology. We also examined the effect in vivo and found that NDRG1 depletion promoted OVCAR3 xenograft growth in nude mice. In accordance with these data, we found that NDRG1 overexpression decreased proliferation, adhesion and apoptosis, and induced G0/G1 cell cycle arrest in OVCAR3 cells; expression of p21 and p53 was also increased. In conclusion, we demonstrated that NDRG1 acts as a tumor suppressor in ovarian carcinogenesis and may be a potential therapeutic target in this disease.

Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

N-myc downstream-regulated gene 1: Diverse and complicated functions in human hepatocellular carcinoma (Review)

N-myc downstream-regulated gene 1 (NDRG1) has been reported to be a multifunctional protein associated with carcinogenesis and tumor progression. However, the cellular function of NDRG1 remains elusive in human hepatocellular carcinoma (HCC). No NDRG1 expression is observed in normal liver tissue. Overexpression of NDRG1 has been observed in human HCC, particularly with aggressive invasion, metastasis, poor differentiation and short patient survival. In addition, recent studies have shown that NDRG1 exhibits an inhibitory effect on HCC growth in vitro and in vivo, which contrasts with previous reports indicating that NDRG1 promotes the proliferation and invasion of HCC cell lines. Further studies have shown that the localization of NDRG1 is variable, translocating to the nucleus or membrane according to the cell state, which may relate to the diverse function of NDRG1. The present study reviews our current knowledge with regard to the functions of NDRG1 in HCC and other types of human cancer.

Aberrant NDRG1 methylation associated with its decreased expression and clinicopathological significance in breast cancer

Background

Cancer cell differentiation is an important characteristic of malignant tumor and has a great impact on prognosis and therapeutic decision for patients. The N-myc downstream regulated gene 1 (NDRG1), a putative tumor suppression gene, is involved in the regulation of human cell differentiation and metastasis in various cancers. Changes in the status of methylation of the NDRG1 gene have not been studied in detail in human breast cancer.

Results

The MDA-MB-231 breast tumor cell line could express NDRG1. However, it was only expressed after treatment with 5-Aza-2'-deoxycytidine (AZA) in T47D cell line, which revealed that NDRG1 expression could modulated by DNA methylation. Therefore, the fragment surrounding the transcript start site of NDRG1 gene promoter was cloned after sodium bisulfite DNA treatment. A high density (66%) of methylation for human NDRG1 gene promoter was detected in T47D; however, there was only 16% of methylated CpG dinucleotides in the NDRG1 gene promoter in MDA-MB-231. DNA methylation in the NDRG1 promoter was detected in 31.1% of primary breast cancer samples. Furthermore, the NDRG1 promoter methylation correlated with the Tumor Node Metastasis (TNM) at stage III/IV, metastasis, lymph invasion, moderate and poor histological grade in the breast cancer patients.

Conclusion

These findings suggest that the DNA methylation status of NDRG1 gene may play an important role in the pathogenesis and/or development of breast cancer, and the expression could be regulated by aberrant DNA methylation.

Metastasis suppressor, NDRG1, mediates its activity through signaling pathways and molecular motors

The metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), is negatively correlated with tumor progression in multiple neoplasms, being a promising new target for cancer treatment. However, the precise molecular effects of NDRG1 remain unclear. Herein, we summarize recent advances in understanding the impact of NDRG1 on cancer metastasis with emphasis on its interactions with the key oncogenic nuclear factor-kappaB, phosphatidylinositol-3 kinase/phosphorylated AKT/mammalian target of rapamycin and Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathways. Recent studies demonstrating the inhibitory effects of NDRG1 on the epithelial-mesenchymal transition, a key initial step in metastasis, TGF-β pathway and the Wnt/β-catenin pathway are also described. Furthermore, NDRG1 was also demonstrated to regulate molecular motors in cancer cells, leading to inhibition of F-actin polymerization, stress fiber formation and subsequent reduction of cancer cell migration. Collectively, this review summarizes the underlying molecular mechanisms of the antimetastatic effects of NDRG1 in cancer cells.

Targeting the metastasis suppressor, NDRG1, using novel iron chelators: regulation of stress fiber-mediated tumor cell migration via modulation of the ROCK1/pMLC2 signaling pathway

The iron-regulated metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), is up-regulated by cellular iron depletion mediated by iron chelators and can inhibit cancer cell migration. However, the mechanism of how NDRG1 achieves this effect remains unclear. In this study, we implemented established and newly constructed NDRG1 overexpression and knockdown models using the DU145, HT29, and HCT116 cancer cell lines to investigate the molecular basis by which NDRG1 exerts its inhibitory effect on cell migration. Using these models, we demonstrated that NDRG1 overexpression inhibits cell migration by preventing actin-filament polymerization, stress fiber assembly and formation. In contrast, NDRG1 knockdown had the opposite effect. Moreover, we identified that NDRG1 inhibited an important regulatory pathway mediated by the Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)/phosphorylated myosin light chain 2 (pMLC2) pathway that modulates stress fiber assembly. The phosphorylation of MLC2 is a key process in inducing stress fiber contraction, and this was shown to be markedly decreased or increased by NDRG1 overexpression or knockdown, respectively. The mechanism involved in the inhibition of MLC2 phosphorylation by NDRG1 was mediated by a significant (P < 0.001) decrease in ROCK1 expression that is a key kinase involved in MLC2 phosphorylation. Considering that NDRG1 is up-regulated after cellular iron depletion, novel thiosemicarbazone iron chelators (e.g., di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone) were demonstrated to inhibit ROCK1/pMLC2-modulated actin-filament polymerization, stress fiber assembly, and formation via a mechanism involving NDRG1. These results highlight the role of the ROCK1/pMLC2 pathway in the NDRG1-mediated antimetastatic signaling network and the therapeutic potential of iron chelators at inhibiting metastasis.

Molecular profiles of pre- and postoperative breast cancer tumours reveal differentially expressed genes

Gene expression studies on breast cancer have generally been performed on tissue obtained at the time of surgery. In this study, we have compared the gene expression profiles in preoperative tissue (core needle biopsies) while tumor is still in its normal milieu to postoperative tissue from the same tumor obtained during surgery. Thirteen patients were included of which eleven had undergone sentinel node diagnosis procedure before operation. Microarray gene expression analysis was performed using total RNA from all the samples. Paired significance analysis of microarrays revealed 228 differently expressed genes, including several early response stress-related genes such as members of the fos and jun families as well as genes of which the expression has previously been associated with cancer. The expression profiles found in the analyses of breast cancer tissue must be evaluated with caution. Different profiles may simply be the result of differences in the surgical trauma and timing of when samples are taken and not necessarily associated with tumor biology.

Secreted protein acidic and rich in cysteines-like 1 suppresses aggressiveness and predicts better survival in colorectal cancers

PURPOSE

Secreted protein acidic and rich in cysteines-like 1 (SPARCL1) is an extracellular matrix glycoprotein with malignancy-suppressing potential. The hypothesis that SPARCL1 reduces cancer invasiveness and predicts better survival in colorectal cancers (CRC) was investigated.

EXPERIMENTAL DESIGN

Stable SPARCL1 transfectants, RKO-SPARCL1, and corresponding vector control were constructed and implanted into nude mice to generate a mouse xenograft model of liver metastasis. Also, a retrospective outcome study was conducted on the COH set (222 CRCs) and ZJU set (412 CRCs). The protein expression level of SPARCL1 was determined by immunohistochemistry. The Kaplan-Meier and Cox analyses were used for survival analysis. The association of SPARCL1 with mesenchymal-epithelial transition (MET) was examined by reverse transcription PCR (RT-PCR) and Western blot analysis.

RESULTS

The ectopic expression of SPARCL1 significantly reduced the potential for anchorage-independent growth, migration, invasion and induced cell differentiation in RKO and SW620 cells. In mouse xenograft model, the expression of SPARCL1 significantly reduced the liver metastasis (P < 0.01). The patient-based studies revealed that the expression of SPARCL1 was related to better differentiation (P < 0.01), less lymph node involvement [OR, 0.67; 95% confidence interval (CI), 0.45-1.00], and less distant metastasis (OR, 0.38; 95% CI, 0.18-0.79). The Kaplan-Meier and Cox analysis showed that the expression of SPARCL1 was associated with better overall survival (log-rank: P < 0.01; HR, 0.57; 95% CI, 0.39-0.84). Transfection of SPARCL1 induced MET of colon cancer cells.

CONCLUSION

SPARCL1 functions as a tumor suppressor promoting differentiation possibly via MET, which inhibits the aggressiveness of CRCs.

c-MET protects breast cancer cells from apoptosis induced by sodium butyrate

Sodium Butyrate (NaBu) is regarded as a potential reagent for cancer therapy. In this study, a specific breast cancer cell population that is resistant NaBu treatment was identified. These cells possess cancer stem cell characters, such as the capability of sphere formation in vitro and high tumor incident rate (85%) in mouse model. Forty percent of the NaBu resistant cells express the cancer stem cells marker, the CD133, whereas only 10% intact cells present the CD133 antigen. Furthermore, the endogenous expressing c-MET contributes to the survival of cancer stem cell population from the treatment of NaBu. The CD133+ group also presents a higher level of c-MET. A combination treatment of MET siRNA and NaBu efficiently prohibited the breast cancer progression, and the incident rate of the tumor decrease to 18%. This study may help to develop a new and alternative strategy for breast cancer therapy.