Expression of the nm23 homologues nm23-H4, nm23-H6, and nm23-H7 in human gastric and colon cancer

Widely targeted metabolomic analyses unveil the metabolic variations after stable knock-down of NME4 in esophageal squamous cell carcinoma cells

NME4, also designated nm23-H4 or NDPK-D, has been known for years for its well-established roles in the synthesis of nucleoside triphosphates, though; little has been known regarding the differential metabolites involved as well as the biological roles NME4 plays in proliferation and invasion of esophageal squamous cell carcinoma (ESCC) cells. To understand the biological roles of NME4 in ESCC cells, lentiviral-based short hairpin RNA interference (shRNA) vectors were constructed and used to stably knock down NME4. Then, the proliferative and invasive variations were assessed using MTT, Colony formation and Transwell assays. To understand the metabolites involved after silencing of NME4 in ESCC cells, widely targeted metabolomic screening was taken. It was discovered that silencing of NME4 can profoundly suppress the proliferation and invasion in ESCC cells in vitro. Metabolically, a total of 11 differential metabolites were screened. KEGG analyses revealed that Tryptophan, Riboflavin, Purine, Nicotinate, lysine degradation, and Linoleic acid metabolism were also involved in addition to the well-established nucleotides metabolism. Some of these differential metabolites, say, 2-Picolinic Acid, Nicotinic Acid and Pipecolinic Acid were suggested to be associated with tumor immunomodulation. The data we described here support the idea that metabolisms occurred in mitochondrial was closely related to tumor immunity.

NME4 may enhance non‑small cell lung cancer progression by overcoming cell cycle arrest and promoting cellular proliferation

Nucleoside diphosphate kinase 4 (NME4) is abnormally expressed in a variety of cancer types. However, the function of the NME4 gene in non-small cell lung cancer (NSCLC) remains to be elucidated. In order to investigate the role of NME4 in NSCLC, the present study detected the expression of the NME4 gene in the Cancer Genome Atlas database, and in BEAS-2B, NCI-H1299 and A549 cell lines. NME4 was significantly overexpressed in NSCLC tissues and NSCLC cell lines. Furthermore, lentivirus-mediated knockdown vector infection, cell proliferation, cell cycle, apoptosis, colony formation and MTT assays were conducted to explore the effect of NME4 on NSCLC in vitro. After knockdown of NME4 with short hairpin RNA, the cell cycle was arrest at the G1 phase, and proliferation and colony formation were inhibited in the NCI-H1299 and A549 cell lines. The present results suggested that NME4 may serve as a novel tumor promoter, capable of enhancing NSCLC progression by overcoming cell cycle arrest and promoting proliferation.

The mitochondrial nucleoside diphosphate kinase (NDPK-D/NME4), a moonlighting protein for cell homeostasis

Mitochondrial nucleoside diphosphate kinase (NDPK-D; synonyms: NME4, NM23-H4) represents the major mitochondrial NDP kinase. The homohexameric complex emerged as a protein with multiple functions in bioenergetics and phospholipid signaling. It occurs at different but precise mitochondrial locations and can affect among other mitochondrial shapes and dynamics, as well as the specific elimination of defective mitochondria or cells via mitophagy or apoptosis. With these various functions in cell homeostasis, NDPK-D/NME4 adds to the group of so-called moonlighting (or gene sharing) proteins.

OncomiR-196 promotes an invasive phenotype in oral cancer through the NME4-JNK-TIMP1-MMP signaling pathway

Background

MicroRNA-196 (miR-196), which is highly up-regulated in oral cancer cells, has been reported to be aberrantly expressed in several cancers; however, the significance of miR-196 in oral cancer has not yet been addressed.

Methods

Cellular functions in response to miR-196 modulation were examined, including cell growth, migration, invasion and radio/chemosensitivity. Algorithm-based studies were used to identify the regulatory target of miR-196. The miR-196 target gene and downstream molecular mechanisms were confirmed by RT-qPCR, western blot, luciferase reporter and confocal microscopy analyses. miR-196 expression was determined in paired cancer and adjacent normal tissues from oral cancer patients.

Results

Both miR-196a and miR-196b were highly over-expressed in the cancer tissue and correlated with lymph node metastasis (P = 0.001 and P = 0.006, respectively). Functionally, miR-196 actively promoted cell migration and invasion without affecting cell growth. Mechanistically, miR-196 performed it's their function by inhibiting NME4 expression and further activating p-JNK, suppressing TIMP1, and augmenting MMP1/9.

Conclusion

miR-196 contributes to oral cancer by promoting cell migration and invasion. Clinically, miR-196a/b was significantly over-expressed in the cancer tissues and correlated with lymph node metastasis. Thus, our findings provide new knowledge of the underlying mechanism of cancer metastasis. miR-196 may serve as a promising marker for better oral cancer management.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-218) contains supplementary material, which is available to authorized users.

Evidence for field effect cancerization in colorectal cancer

We compared transcript expression, and chromosomal changes on a series of tumors and surrounding tissues to determine if there is evidence of field cancerization in colorectal cancer. Epithelial cells were isolated from tumors and areas adjacent to the tumors ranging from 1 to 10cm. Tumor abnormalities mirrored those previously reported for colon cancer and while the number and size of the chromosomal abnormalities were greatly reduced in cells from surrounding regions, many chromosome abnormalities were discernable. Interestingly, these abnormalities were not consistent across the field in the same patient samples suggesting a field of chromosomal instability surrounding the tumor. A mutator phenotype has been proposed to account for this instability which states that the genotypes of cells within a tumor would not be identical, but would share at least a single mutation in any number of genes, or a selection of genes affecting a specific pathway which provide a proliferative advantage.

Relationship between the nm23 gene and prognosis of esophageal carcinoma

The occurrence and development of esophageal cancer are the result of multiple gene interactions, and the nm23 gene is involved in the regulation of tumor cell metastasis and can inhibit lymph node metastasis. The detection of the change in the nm23 gene can help predict the presence of lymph node metastasis or not in esophageal carcinoma. Moreover, nm23 is an important indicator for prognosis evaluation in esophageal carcinoma.

Thioredoxin-like protein 2 is overexpressed in colon cancer and promotes cancer cell metastasis by interaction with ran

AIMS

Our previous work identified thioredoxin-like protein 2 (Txl-2) as the target of the monoclonal antibody MC3 associated with colon cancer, but its underlying mechanisms remain poorly understood. Txl-2, a novel thioredoxin (Trx) and nucleoside diphosphate kinase family member, is alternatively spliced and gives rise to three different Txl-2 isoforms. In this study, Txl-2 expression in colon cancer, differential functions for Txl-2 isoforms in cell invasion and metastasis, and the downstream signaling were investigated.

RESULTS

Txl-2 expression was elevated in colon cancer tissues compared to normal colonic tissues, with a high correlation between the histological grade and prognosis. Knockdown of Txl-2 expression significantly inhibited cancer cell motility, and the invasive and metastatic abilities of colon cancer cells. Interestingly, Txl-2 isoforms showed differential effects on cancer cell invasion and metastasis. Cell invasion and metastasis were significantly promoted by Txl-2b but inhibited by Txl-2c, while no obvious effect was observed for Txl-2a. Furthermore, a direct interaction was identified between Txl-2b and Ran, a Ras-related protein, by yeast two-hybrid assay and coimmunoprecipitation. PI3K pathway was found to be a major pathway mediating Txl-2b induced tumor invasion and metastasis.

INNOVATION

The current study provides a novel biomarker and target molecule for the diagnosis and treatment of colon cancer and provides a novel paradigm to understand how alternative splicing functions in human cancer.

CONCLUSION

Our findings demonstrate an elevated Txl-2 expression in colon cancer and that Txl-2b promotes cell invasion and metastasis through interaction with Ran and PI3K signaling pathway.

A shRNA functional screen reveals Nme6 and Nme7 are crucial for embryonic stem cell renewal

In contrast to the somatic cells, embryonic stem cells (ESCs) are characterized by its immortalization ability, pluripotency, and oncogenicity. Revealing the underlying mechanism of ESC characteristics is important for the application of ESCs in clinical medicine. We performed systematic functional screen in mouse ESCs with 4,801 shRNAs that target 929 kinases and phosphatases. One hundred and thirty-two candidate genes that regulate both ESC expansion and stem cell marker expression were identified. Twenty-seven out of the 132 genes were regarded as most important since knockdown of each gene induces morphological changes from undifferentiated to differentiated state. Among the 27 genes, we chose nonmetastatic cell 6 (Nme6, also named as Nm23-H6) and nonmetastatic cell 7 (Nme7, also designated as Nm23-H7) to study first. Nme6 and Nme7 both belong to the members of nucleoside diphosphate kinase family. We demonstrate that Nme6 and Nme7 are important for the regulation of Oct4, Nanog, Klf4, c-Myc, telomerase, Dnmt3B, Sox2, and ERas expression. Either knockdown of Nme6 or Nme7 reduces the formation of embryoid body (EB) and teratoma. The overexpression of either Nme6 or Nme7 can rescue the stem cell marker expression and the EB formation in the absence of leukemia inhibiting factor. This implies the importance of Nme6 and Nme7 in ESC renewal. This finding not only pinpoints Nme6 or Nme7 can regulate several critical regulators in ESC renewal but also increases our understanding of the ESC renewal and oncogenesis.

Characterization of Nme6-like gene/protein from marine sponge Suberites domuncula

Nucleoside diphosphate kinases (NDPKs) are evolutionarily conserved enzymes involved in many biological processes such as metastasis, proliferation, development, differentiation, ciliary functions, vesicle transport and apoptosis in vertebrates. Biochemical mechanisms of these processes are still largely unknown. Sponges (Porifera) are simple metazoans without tissues, closest to the common ancestor of all animals. They changed little during evolution and probably provide the best insight into the metazoan ancestors' genomic features. The purpose of this study was to address structural and functional properties of group II Nme6 gene/protein ortholog from the marine sponge Suberites domuncula, Nme6, in order to elucidate its evolutionary history. Sponge Nme6 gene and promoter were sequenced and analysed with various bioinformatical tools. Nme6 and Nme6Δ31 proteins were produced in E. coli strain BL21 and NDPK activity was measured using a coupled pyruvate kinase-lactate dehydrogenase assay. Subcellular localization in human tumour cells was examined by confocal scanning microscopy. Our results show that the sponge Nme6 compared to human Nme6 does not possess NDPK activity, does not localize in mitochondria at least in human cells although it has a putative mitochondrial signal sequence, lacks two recent introns that comprise miRNAs and have different transcriptional binding sites in the promoter region. Therefore, we conclude that the structure of Nme6 gene has changed during metazoan evolution possibly in correlation with the function of the protein.

Mass spectrometry detection of histidine phosphorylation on NM23-H1

Phosphorylation is a ubiquitous protein post-translational modification that is intimately involved in most aspects of cellular regulation. Currently, most proteomic analyses are performed with phosphorylation searches for serine, threonine, and tyrosine modifications, as the phosphorylated residues of histidine and aspartic acid are acid labile and thus undetectable with most proteomic methodologies. Here, we present a novel buffer system to show histidine phosphorylation of NM23-H1, the product of the first identified putative human metastasis suppressor gene (NME1), which catalyzes the transfer of the γ-phosphate from nucleoside triphosphates to nucleoside diphosphates. On the basis of a pH titration of LC elution buffers and MS/MS identification, recombinant NM23-H1 subjected to autophosphorylation was shown to contain phosphorylated histidine at residue 118 at pH 5 and 6, with each level giving over 75% peptide coverage for identification. The solvent system presented permits the detection of all five possible phosphorylation moieties. Application of histidine and aspartic acid phosphorylation modifications to proteomic analyses will significantly advance the understanding of phosphorylation relay signaling in cellular regulation, including elucidation of the role of NM23-H1 in metastasis.

Nm23-M5 mediates round and elongated spermatid survival by regulating GPX-5 levels

Nucleoside diphosphate (NDP) kinases are involved in numerous regulatory processes associated with proliferation, development, and differentiation. Previously, we cloned a new member of the NDPK family from mouse, Nm23-M5, which encodes a 211-amino acid protein and has 86% identity to the human Nm23-H5 [Hwang, K.C., Ok, D.W., Hong, J.C., Kim, M.O. and Kim, J.H. (2003) Cloning, sequencing, and characterization of the murine Nm23-M5 gene during mouse spermatogenesis and spermiogenesis. Biochem. Biophys. Res. Commun. 306, 198-207]. To better understand Nm23-M5 function, we generated transgenic mice with reduced Nm23-M5 levels in vivo using a short hairpin RNA (shRNA) knock-down system. Nm23-M5 expression was markedly reduced, as indicated by Northern and Western blot analysis. Nm23-M5 shRNA transgenic mice exhibited reduced numbers of haploid cells. Furthermore, the antioxidant enzyme glutathione peroxidase 5 (GPX-5) is regulated by Nm23-M5 at the level of both expression and activity. These results reveal that expression of Nm23-M5 plays a critical role in spermiogenesis by increasing the cellular levels of GPX-5 to eliminate reactive oxygen species.

High expression of ERCC1, FLT1, NME4 and PCNA associated with poor prognosis and advanced stages in myelodysplastic syndrome

Myelodysplastic syndrome (MDS) represents a good model for research of prognostic/progression markers due to frequent transformation into acute myeloid leukemia (AML). We analysed expression profiles of 26 MDS and 6 AML patients using cDNA arrays comprising 588 gene probes. The array data were validated in a larger set of 46 patients by qRT-PCR. Data analysis identified differently expressed genes in MDS and the cluster of four genes (ERCC1, FLT1, NME4 and PCNA) whose expression was correlated with MDS subtypes. High expression of these genes was associated with poor prognosis and/or unfavorable outcome. Furthermore, PCNA expression was correlated with peripheral blood blast percentage (r = 0.71, p < 0.05), while the other genes showed non-significant correlation. Our findings demonstrate the progressive up-regulation of the genes along the sequence of 5q-syndrome/RCMD/RAEB/de novo AML, suggesting their association with disease progression.

Emerging roles for protein histidine phosphorylation in cellular signal transduction: lessons from the islet beta-cell

Protein phosphorylation represents one of the key regulatory events in physiological insulin secretion from the islet β-cell. In this context, several classes of protein kinases (e.g. calcium-, cyclic nucleotide- and phospholipid-dependent protein kinases and tyrosine kinases) have been characterized in the β-cell. The majority of phosphorylated amino acids identified include phosphoserine, phosphothreonine and phosphotyrosine. Protein histidine phosphorylation has been implicated in the prokaryotic and eukaryotic cellular signal transduction. Most notably, phoshohistidine accounts for 6% of total protein phosphorylation in eukaryotes, which makes it nearly 100-fold more abundant than phosphotyrosine, but less abundant than phosphoserine and phosphothreonine. However, very little is known about the number of proteins with phosphohistidines, since they are highly labile and are rapidly lost during phosphoamino acid identification under standard experimental conditions. The overall objectives of this review are to: (i) summarize the existing evidence indicating the subcellular distribution and characterization of various histidine kinases in the islet β-cell, (ii) describe evidence for functional regulation of these kinases by agonists of insulin secretion, (iii) present a working model to implicate novel regulatory roles for histidine kinases in the receptor-independent activation, by glucose, of G-proteins endogenous to the β-cell, (iv) summarize evidence supporting the localization of protein histidine phosphatases in the islet β-cell and (v) highlight experimental evidence suggesting potential defects in the histidine kinase signalling cascade in islets derived from the Goto-Kakizaki (GK) rat, a model for type 2 diabetes. Potential avenues for future research to further decipher regulatory roles for protein histidine phosphorylation in physiological insulin secretion are also discussed.

Changes of histology and expression of MMP-2 and nm23-H1 in primary and metastatic gastric cancer

AIM: To investigate the changes of histology and expression of MMP-2 and nm23-H1 in primary and metastatic gastric cancer.

METHODS: One hundred and seventy-seven gastric cancer patients with lymph node and/or distal metastasis between 1997 and 2001 were reviewed. Differences in histology of the primary and metastatic gastric cancer were assessed. MMP-2 and nm23-H1 immunoreactivity was compared in 44 patients with tumor infiltration to the serosa layer.

RESULTS: Poorly and moderately differentiated metastatic gastric cancer was found in 88.7% (157/177) and primary gastric cancer in 75.7% (134/177) of the patients. The histological type of metastatic gastric cancer that was not completely in accordance with the preponderant histology of primary gastric cancer was observed in 25 patients (14.1%). MMP-2 immunoreactivity in metastatic gastric cancer was significantly stronger than that in primary gastric cancer, while nm23-H1 immunoreactivity showed no difference in primary and metastatic gastric cancer.

CONCLUSION: Metastatic gastric cancer presents more aggressive histological morphology and higher MMP-2 immunoreactivity than primary gastric cancer. This heterogeneity may elicit a possible mechanism of gastric cancer metastasis.

Association of EcoRI polymorphism of the metastasis-suppressor gene NME1 with susceptibility to and severity of non-small cell lung cancer

BACKGROUND

Human lung cancer cells with high metastatic potential show reduced expression of the metastasis-suppressor gene NME1. However, the biallelic EcoRI polymorphism of this gene has not been studied in lung cancer. With this allelic association study, we aimed to investigate the impact of polymorphisms of the NME1 gene on the susceptibility to and severity of non-small cell lung cancer (NSCLC).

METHODS

Through a case-control study design, genomic DNA samples of 255 NSCLC patients and 303 controls, who were age and sex-matched and recruited from the health check-up unit, were subjected to polymorphism analysis with polymerase chain reaction-restriction fragment length polymorphism technique. The validity of this technique was proven by direct sequencing of polymerase chain reaction products. Statistical analyses were conducted to explore the contribution of polymorphism of the metastasis-suppressor gene NME1 in the susceptibility to and severity of NSCLC.

RESULTS

Overall, the genotype frequencies of NME1 gene were significantly different between lung cancer patients and controls (p < 0.0001), and also different between patients with lung cancers of various stages (p < 0.0001). Logistic regression analysis revealed that higher odds ratios (ORs) for lung cancer were seen in patients homozygous (+/+) for variant allele (an OR of 4.02, 95% CI 2.39-6.76; p < 0.0001). Patients carrying a variant polymorphic homozygote (+/+) also had a tendency to advanced disease (p = 0.001).

CONCLUSION

A significant association between the polymorphisms of NME1 gene and the susceptibility to and severity of lung cancer was demonstrated.

Heterogeneous Metastasis Efficiency of Isogenic Orthotopic Colon Cancer Xenografts Reveals Distinctive Gene Expression Profiles

Hepatic and lung metastases are the leading causes of mortality and major indicators of aggressiveness in colorectal cancer. The underlying molecular mechanisms contributing to the development of metastasis are still unclear. Here, we designed a novel approach to explore gene expression profiles associated with metastasis in human colorectal cancer (hCRC). A series of ten isogenic tumors from three different hCRC models were orthotopically implanted into nude mice. In these series, we analyzed the contribution of dynamic heterogeneity, independently of any intrinsic gene expression program predictive of metastasis. When screened for the presence of disseminated tumor cells in the lung and liver, as the most common host tissues for hCRC metastases, both high- and low-metastatic efficient tumors were found among these isogenic orthotopic series. The metastasis-specific cDNA macroarray analysis of 96 genes, in both tumor populations for each of the three hCRC models, characterized a common differential gene expression within a small group of genes. Our results suggest that, independently of a gene expression profile predictive of metastasis, the progressive acquisition of additional alterations occurs during hCRC tumorigenesis. This dynamic process might determine tumor progression, namely the metastasis dissemination.

Novel lipid transfer property of two mitochondrial proteins that bridge the inner and outer membranes

This study provides evidence of a novel function for mitochondrial creatine kinase (MtCK) and nucleoside diphosphate kinase (NDPK-D). Both are basic peripheral membrane proteins with symmetrical homo-oligomeric structure, which in the case of MtCK was already shown to allow crossbridging of lipid bilayers. Here, different lipid dilution assays clearly demonstrate that both kinases also facilitate lipid transfer from one bilayer to another. Lipid transfer occurs between liposomes mimicking the lipid composition of mitochondrial contact sites, containing 30 mol % cardiolipin, but transfer does not occur when cardiolipin is replaced by phosphatidylglycerol. Ubiquitous MtCK, but not NDPK-D, shows some specificity in the nature of the lipids transferred and it is not active with phosphatidylcholine alone. MtCK can undergo reversible oligomerization between dimeric and octameric forms, but only the octamer can bridge membranes and promote lipid transfer. Cytochrome c, another basic mitochondrial protein known to bind to anionic membranes but not crosslinking them, is also incapable of promoting lipid transfer. The lipid transfer process does not involve vesicle fusion or loss of the internal contents of the liposomes.

Inhibition of ovarian cancer metastasis by adeno-associated virus-mediated gene transfer of nm23H1 in an orthotopic implantation model

Ovarian cancer is one of the most threatening malignant tumors in females due to the frequent occurrence of metastasis that precedes diagnosis. The present study explored the possibility of preventing ovarian cancer metastasis by promoting nm23H1 expression through adeno-associated virus (AAV)-mediated gene transfer. A cell line of high metastatic potential, SW626-M4, was derived by in vivo selection and used to establish an ovarian cancer metastasis model in the mouse. Liver metastasis and animal survival time were measured after transfer of a recombinant adeno-associated viral vector expressing nm23H1 (AAV-nm23H1) into the aforementioned model. Intraperitoneal injection of AAV-nm23H1 into this orthotopic implantation model of ovarian cancer resulted in (1) expression of the exogenous gene in more than 95% of tumor cells in situ in nude mice; (2) a 60% reduction in the number of animals developing liver metastases; and (3) a 35-day prolongation of median survival time compared with the untreated host group. In conclusion, the results support the feasibility of induction of nm23H1 expression through gene transfer as a therapeutic strategy for preventing metastases and prolonging host survival time, and indicate that AAV vectors deserve attention in the design of future gene therapy approaches to achieving long-term expression of curative genes in vivo.