Clinical-translational approaches to the Nm23-H1 metastasis suppressor

Mechanisms of action of NME metastasis suppressors - a family affair

Metastatic progression is regulated by metastasis promoter and suppressor genes. NME1, the prototypic and first described metastasis suppressor gene, encodes a nucleoside diphosphate kinase (NDPK) involved in nucleotide metabolism; two related family members, NME2 and NME4, are also reported as metastasis suppressors. These proteins physically interact with members of the GTPase dynamin family, which have key functions in membrane fission and fusion reactions necessary for endocytosis and mitochondrial dynamics. Evidence supports a model in which NDPKs provide GTP to dynamins to maintain a high local GTP concentration for optimal dynamin function. NME1 and NME2 are cytosolic enzymes that provide GTP to dynamins at the plasma membrane, which drive endocytosis, suggesting that these NMEs are necessary to attenuate signaling by receptors on the cell surface. Disruption of NDPK activity in NME-deficient tumors may thus drive metastasis by prolonging signaling. NME4 is a mitochondrial enzyme that interacts with the dynamin OPA1 at the mitochondria inner membrane to drive inner membrane fusion and maintain a fused mitochondrial network. This function is consistent with the current view that mitochondrial fusion inhibits the metastatic potential of tumor cells whereas mitochondrial fission promotes metastasis progression. The roles of NME family members in dynamin-mediated endocytosis and mitochondrial dynamics and the intimate link between these processes and metastasis provide a new framework to understand the metastasis suppressor functions of NME proteins.

Heterochiral dipeptide d-phenylalanyl- l-phenylalanine (H-D Phe-L Phe-OH) as a potential inducer of metastatic suppressor NM23H1 in p53 wild-type and mutant cells

In recent years, significant progress has been made to the use-case of small peptides because of their diversified edifice and hence their versatile application scope in cancer therapy. Here we identify the heterochiral dipeptide H-^D Phe-^L Phe-OH (F1) as a potent inducer of the metastatic suppressor NM23H1. We divulge the effect of F1 on the major EMT/metastasis-associated genes and the implications on the invasion and migration ability of cancer cells. The anti-invasive potential of F1 was directly correlated with NM23H1 expression. Mechanistically, F1 treatment elevated p53 levels as validated by localization and transcriptional studies. In the NM23H1 knockdown condition, F1 failed to induce any p53 expression/nuclear localization, indicating that the upregulation in p53 expression by F1 is NM23H1 dependent. We also demonstrate how the antimetastatic potential of F1 is primarily mediated through NM23H1 irrespective of the p53 status of the cell. However, both NM23H1 and a functional p53 protein in conjunction govern the apoptotic and cytostatic potential of F1. Coimmunoprecipitation studies unraveled the augmentation of the p53 and NM23H1 interaction in p53 wild-type cells. However, in p53 mutated cells, no such enrichment was evidenced. We employed mouse isogenic cell lines (4T-1 and 4T-1 p53) to determine the in vivo efficacy of F1 (spontaneous and experimental models). Decreased tumor volume in the cohort injected with 4T-1 p53 cells demonstrated that while the antimetastatic potential of F1 was reliant on NM23H1, p53 activation was required for ablation of primary tumor burden. Our findings unravel that F1 treatment induces significant abrogation of the migration, invasion and metastatic potential of both p53 wild-type and p53 deficient cancers mediated through NM23H1.

NM23-H1 Expression of Head and Neck Squamous Cell Carcinoma in Association With the Response to Irradiation

A low NM23-H1 expression in head and neck squamous cell carcinoma (HNSCC) was found to be associated with poor clinical outcome. Therefore, we investigated the role of NM23-H1 in the susceptibility of HNSCC cells to irradiation and its clinical significance. An in vitro study was also conducted to validate the results. Furthermore, we used immunohistochemistry to analyze NM23-H1 expression found in specimens of 50 HNSCC patients with cervical metastases receiving postoperative radiotherapy. Low tumor NM23-H1 expression was associated with locoregional recurrence of HNSCC (p=0.040; Hazard ratio=5.62) and poor clinical outcome (p=0.001; Hazard ratio=4.90). To confirm the effect of NM23-H1 on radiation-induced cytotoxicity, we generated several stable clones derived from a human HNSCC cell line (SAS) using knockdown and overexpression of NM23-H1. Knockdown of NM23-H1 decreased the radio-sensitivity of SAS cells, possibly associated with a decrease in the radiation-induced G2/M-phase accumulation and upregulation of cyclin B1. On the contrary, overexpression of NM23-H1 can reverse the aforementioned adverse results. Consequently, we suggest that NM23-H1 expression may be considered as a potential therapeutic treatment option for HNSCC patients.

Activation of Nm23-H1 to suppress breast cancer metastasis via redox regulation

Non-metastatic protein 23 H1 (Nm23-H1), a housekeeping enzyme, is a nucleoside diphosphate kinase-A (NDPK-A). It was the first identified metastasis suppressor protein. Nm23-H1 prolongs disease-free survival and is associated with a good prognosis in breast cancer patients. However, the molecular mechanisms underlying the role of Nm23-H1 in biological processes are still not well understood. This is a review of recent studies focusing on controlling NDPK activity based on the redox regulation of Nm23-H1, structural, and functional changes associated with the oxidation of cysteine residues, and the relationship between NDPK activity and cancer metastasis. Further understanding of the redox regulation of the NDPK function will likely provide a new perspective for developing new strategies for the activation of NDPK-A in suppressing cancer metastasis.

The multiple regulation of metastasis suppressor NM23-H1 in cancer

Metastasis is one of the leading causes of mortality in cancer patients. As the firstly identified metastasis suppressor, NM23-H1 has been endowed with expectation as a potent target in metastatic cancer therapy during the past decades. However, many challenges impede its clinical use. Accumulating evidence shows that NM23-H1 has a dichotomous role in tumor metastasis as a suppressor and promoter. It has potentially attributed to its versatile biochemical characteristics such as nucleoside diphosphate kinase (NDPK) activity, histidine kinase activity (HPK), exonuclease activity, and protein scaffold, which further augment the complexity and uncertainty of its physiological function. Simultaneously, tumor cells have evolved multiple ways to regulate the expression and function of NM23-H1 during tumorigenesis and metastasis. This review summarized and discussed the regulatory mechanisms of NM23-H1 in cancer including transcriptional activation, subcellular location, enzymatic activity, and protein degradation, which significantly modulate its anti-metastatic function.

The vital role of ATP citrate lyase in chronic diseases

Chronic or non-communicable diseases are the leading cause of death worldwide; they usually result in long-term illnesses and demand long-term care. Despite advances in molecular therapeutics, specific biomarkers and targets for the treatment of these diseases are required. The dysregulation of de novo lipogenesis has been found to play an essential role in cell metabolism and is associated with the development and progression of many chronic diseases; this confirms the link between obesity and various chronic diseases. The main enzyme in this pathway-ATP-citrate lyase (ACLY), a lipogenic enzyme-catalyzes the critical reaction linking cellular glucose catabolism and lipogenesis. Increasing lines of evidence suggest that the modulation of ACLY expression correlates with the development and progressions of various chronic diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, obesity, inflammation, and cancer. Recent studies suggest that the inhibition of ACLY activity modulates the glycolysis and lipogenesis processes and stimulates normal physiological functions. This comprehensive review aimed to critically evaluate the role of ACLY in the development and progression of different diseases and the effects of its downregulation in the prevention and treatment of these diseases.

Small Molecules as Drugs to Upregulate Metastasis Suppressors in Cancer Cells

It is well-recognized that the majority of cancer-related deaths is attributed to metastasis, which can arise from virtually any type of tumor. Metastasis is a complex multistep process wherein cancer cells must break away from the primary tumor, intravasate into the circulatory or lymphatic systems, extravasate, proliferate and eventually colonize secondary sites. Since these molecular processes involve the coordinated actions of numerous proteins, targeted disruptions of key players along these pathways represent possible therapeutic interventions to impede metastasis formation and reduce cancer mortality. A diverse group of proteins with demonstrated ability to inhibit metastatic colonization have been identified and they are collectively known as metastasis suppressors. Given that the metastasis suppressors are often downregulated in tumors, drug-induced re-expression or upregulation of these proteins represents a promising approach to limit metastasis. Indeed, over 40 compounds are known to exhibit efficacy in upregulating the expression of metastasis suppressors via transcriptional or post-transcriptional mechanisms, and the most promising ones are being evaluated for their translational potentials. These small molecules range from natural products to drugs in clinical use and they apparently target different molecular pathways, reflecting the diverse nature of the metastasis suppressors. In this review, we provide an overview of the different classes of compounds known to possess the ability to upregulate one or more metastasis suppressors, with an emphasis on their mechanisms of action and therapeutic potentials.

Comparative mitochondrial proteomic analysis of human large cell lung cancer cell lines with different metastasis potential

Background

Lung cancer is a highly aggressive cancer with a poor prognosis and is associated with distant metastasis; however, there are no clinically recognized biomarkers for the early diagnosis and prediction of lung cancer metastasis. We sought to identify the differential mitochondrial protein profiles and understand the molecular mechanisms governing lung cancer metastasis.

Methods

Mitochondrial proteomic analysis was performed to screen and identify the differential mitochondrial protein profiles between human large cell lung cancer cell lines with high (L‐9981) and low (NL‐9980) metastatic potential by two‐dimensional differential gel electrophoresis. Western blot was used to validate the differential mitochondrial proteins from the two cells. Bioinformatic proteome analysis was performed using the Mascot search engine and messenger RNA expression of the 37 genes of the differential mitochondrial proteins were detected by real‐time PCR.

Results

Two hundred and seventeen mitochondrial proteins were differentially expressed between L‐9981 and NL‐9980 cells (P < 0.05). Sixty‐four analyzed proteins were identified by matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry coupled with database interrogation. Ontology analysis revealed that these proteins were mainly involved in the regulation of translation, amino acid metabolism, tricarboxylic acid cycle, cancer invasion and metastasis, oxidative phosphorylation, intracellular signaling pathway, cell cycle, and apoptosis.

Conclusion

Our results suggest that the incorporation of more samples and new datasets will permit the definition of a collection of proteins as potential biomarkers for the prediction and diagnosis of lung cancer metastasis.

Small molecule activator of Nm23/NDPK as an inhibitor of metastasis

Nm23-H1/NDPK-A is a tumor metastasis suppressor having NDP kinase (NDPK) activity. Nm23-H1 is positively associated with prolonged disease-free survival and good prognosis of cancer patients. Approaches to increasing the cellular levels of Nm23-H1 therefore have significance in the therapy of metastatic cancers. We found a small molecule, (±)-trans-3-(3,4-dimethoxyphenyl)-4-[(E)-3,4-dimethoxystyryl]cyclohex-1-ene, that activates Nm23, hereafter called NMac1. NMac1 directly binds to Nm23-H1 and increases its NDPK activity. Employing various NMac1 derivatives and hydrogen/deuterium mass spectrometry (HDX-MS), we identified the pharmacophore and mode of action of NMac1. We found that NMac1 binds to the C-terminal of Nm23-H1 and induces the NDPK activation through its allosteric conformational changes. NMac1-treated MDA-MB-231 breast cancer cells showed dramatic changes in morphology and actin-cytoskeletal organization following inhibition of Rac1 activation. NMac1 also suppressed invasion and migration in vitro, and metastasis in vivo, in a breast cancer mouse model. NMac1 as an activator of NDPK has potential as an anti-metastatic agent.

Fatty acid metabolism in breast cancer subtypes

Dysregulation of fatty acid metabolism is recognized as a component of malignant transformation in many different cancers, including breast; yet the potential for targeting this pathway for prevention and/or treatment of cancer remains unrealized. Evidence indicates that proteins involved in both synthesis and oxidation of fatty acids play a pivotal role in the proliferation, migration and invasion of breast cancer cells. The following essay summarizes data implicating specific fatty acid metabolic enzymes in the genesis and progression of breast cancer, and further categorizes the relevance of specific metabolic pathways to individual intrinsic molecular subtypes of breast cancer. Based on mRNA expression data, the less aggressive luminal subtypes appear to rely on a balance between de novo fatty acid synthesis and oxidation as sources for both biomass and energy requirements, while basal-like, receptor negative subtypes overexpress genes involved in the utilization of exogenous fatty acids. With these differences in mind, treatments may need to be tailored to individual subtypes.

The dosage-dependent effect exerted by the NM23-H1/H2 homolog NDK-1 on distal tip cell migration in C. elegans

Abnormal regulation of cell migration and altered rearrangement of the cytoskeleton are fundamental properties of metastatic cells. The first identified metastasis suppressor NM23-H1, which displays nucleoside-diphosphate kinase (NDPK) activity is involved in these processes. NM23-H1 inhibits the migratory and invasive potential of some cancer cells. Correspondingly, numerous invasive cancer cell lines (eg, breast, colon, oral, hepatocellular carcinoma, and melanoma) display low endogenous NM23 levels. In this review, we summarize mechanisms, which are linked to the anti-metastatic activity of NM23. In human cancer cell lines NM23-H1 was shown to regulate cytoskeleton dynamics through inactivation of Rho/Rac-type GTPases. The Drosophila melanogaster NM23 homolog abnormal wing disc (AWD) controls tracheal and border cell migration. The molecular function of AWD is well characterized in both processes as a GTP supplier of Shi/Dynamin whereby AWD regulates the level of chemotactic receptors on the surface of migrating cells through receptor internalization, by its endocytic function. Our group studied the role of the sole group I NDPK, NDK-1 in distal tip cell (DTC) migration in Caenorhabditis elegans. In the absence of NDK-1 the migration of DTCs is incomplete. A half dosage of NDPK as present in ndk-1 (+/-) heterozygotes results in extra turns and overshoots of migrating gonad arms. Conversely, an elevated NDPK level also leads to incomplete gonadal migration owing to a premature stop of DTCs in the third phase of migration, where NDK-1 acts. We propose that NDK-1 exerts a dosage-dependent effect on the migration of DTCs. Our data derived from DTC migration in C. elegans is consistent with data on AWD's function in Drosophila. The combined data suggest that NDPK enzymes control the availability of surface receptors to regulate cell-sensing cues during cell migration. The dosage of NDPKs may be a coupling factor in cell migration by modulating the efficiency of receptor recycling.

NM23/NDPK proteins in transcription regulatory functions and chromatin modulation: emerging trends

NM23/NDPK proteins have been studied for their metastasis suppressor role but the molecular pathways involved in this process are not very vivid. Nucleotide binding and kinase activities of NM23 proteins implicated in anti-metastatic effects have been widely studied. In addition to these, transcriptional regulation adds another arm to the versatility of NM23 proteins that together with the other functions may contribute to better understanding of underlying mechanisms. In this review we discuss emerging reports describing the role of NM23 proteins in gene regulation and chromatin modulation in association with other factors or on their own.

NM23/NDPK proteins in transcription regulatory functions and chromatin modulation: emerging trends

NM23/NDPK proteins have been studied for their metastasis suppressor role but the molecular pathways involved in this process are not very vivid. Nucleotide binding and kinase activities of NM23 proteins implicated in anti-metastatic effects have been widely studied. In addition to these, transcriptional regulation adds another arm to the versatility of NM23 proteins that together with the other functions may contribute to better understanding of underlying mechanisms. In this review we discuss emerging reports describing the role of NM23 proteins in gene regulation and chromatin modulation in association with other factors or on their own.

Nucleoside diphosphate kinase (Ndk): A pleiotropic effector manipulating bacterial virulence and adaptive responses

Nucleoside diphosphate kinase (Ndk) is a housekeeping enzyme that balances cellular nucleoside triphosphate (NTP) pools by catalyzing the reversible transfer of γ-phosphate from NTPs to nucleoside diphosphates (NDPs). In addition to its fundamental role in nucleotide metabolism, Ndk has roles in protein histidine phosphorylation, DNA cleavage/repair, and gene regulation. Recent studies have also revealed that Ndk secreted from bacteria is important in modulating virulence-associated phenotypes including quorum sensing regulation, type III secretion system activation, and virulence factor production. Moreover, after infection, Ndks released from bacteria are involved in regulating host defense activities, such as cell apoptosis, phagocytosis, and inflammatory responses. Given that Ndk exerts a pleiotropic effect on bacterial virulence and bacteria-host interactions, the biological significance of the bacterial Ndks during infection is intriguing. This review will provide a synopsis of the current knowledge regarding the biological properties and roles of Ndks in regulating bacterial virulence and adaptation and will discuss in depth the biological significance of Ndk during bacteria-host interactions.

High expression of NME1 correlates with progression and poor prognosis in patients of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies that results from genes regulation via different pathways. NME/NM23 nucleoside diphosphate kinase 1 (NME1) is generally regarded as a metastasis suppressor, but its function in HCC is largely unknown. In our study, we explored the role of NME1 in HCC. By analyzing the gene expression omnibus (GEO) database, we discovered that NME1 was more highly expressed in HCC tumor tissues than non-HCC liver tissues (P < 0.001), and NME1 was significantly up-regulated in HCC tumor tissues than in adjacent normal tissues (P < 0.001). Then, validated by the enrolled HCC patients and The Cancer Genome Atlas (TCGA) database, NME1 was upregulated in HCC tumor tissues compared with matched adjacent normal tissue (P < 0.05). Besides, NME1 was down-regulated in Stage III/IV HCC patients than Stage I/II HCC patients (P = 0.009). Moreover, Kaplan-Meier analysis showed that HCC patients with high NME1 expression had poor overall survival (P = 0.004) and higher recurrence rate (P < 0.001). Our data revealed that NME1 was a special oncogene, and its expression was significantly associated with the progression and prognosis of HCC. NME1 may be a novel molecular biomarker for the targeted therapy and prognosis of HCC.

Differential regulation of NM23-H1 under hypoxic and serum starvation conditions in metastatic cancer cells and its implication in EMT

Multiple stresses are prevalent inside the tumor microenvironment rendering tumor growth, neighboring invasion and metastasis of the cancer cells to distant organs. NM23-H1 is the first metastasis suppressor gene identified and known to be implicated as an important regulator of stress-induced metastasis. Herein, we demonstrated that prototypical NM23-H1 expression diminished during hypoxia and serum starvation in Panc-1/MDA-MB-231 cells, but converse invasion patterns were obtained in these two diverse stresses. Supportingly, a compelling discrete difference in mRNA and protein levels of NM23-H1 was achieved in hypoxia as well as serum starvation. Knockdown of NM23-H1 activates EMT whereas the similar effects are subdued in serum starvation where NM23-H1 down-modulation prompted E-cadherin upregulation. Stable NM23-H1 expression augmented E-cadherin levels along with retardation in invadopodea formation and invasion. In hypoxia/serum starvation excess NM23-H1 effectively modulated the Twist1 promoter activity. Thus, differential regulation of NM23-H1 may corroborate/abrogate EMT depending on the nature of stress, tumor microenvironment and cellular context.

Nm23H1 mediates tumor invasion in esophageal squamous cell carcinoma by regulation of CLDN1 through the AKT signaling

Esophageal cancer is a lethal malignancy worldwide. Previously, low expression of metastasis suppressor Nm23H1 and tight junction (TJ) protein claudin-1 (CLDN1) have been known to correlate with poor prognosis in esophageal squamous cell carcinoma (ESCC). However, the molecular interaction between them has not been clarified. In the present study, we first examined the expression of Nm23H1 and CLDN1 in 74 surgical ESCC samples by immunohistochemistry (IHC) to verify their clinicopathologic significance. The biologic effects of Nm23H1 gene silencing or overexpression in ESCC cell lines were then studied by migration and invasion studies, and its regulation on CLDN1 expression was also investigated by western blot analysis. Moreover, the expression of Nm23H1 and CLDN1 at the same invasion front of ESCC tumors was verified by immunofluorescence. The results showed a significantly positive correlation between the expression of Nm23H1 and CLDN1 (γ=0.296, P=0.011) in surgical specimens, especially for the 34 tumors with lymph-node metastasis (γ=0.455, P=0.007). In ESCC cell lines, silencing of Nm23H1 expression markedly enhanced cell invasiveness, accompanied by increased Akt phosphorylation and decreased CLDN1 expression. Conversely, Nm23H1-expressed transfectants exhibited reduced invasiveness, decreased Akt phosphorylation and correspondingly increased CLDN1 expression. Regain of CLDN1 expression in ESCC cells significantly suppressed invasiveness, but did not influence the Akt phosphorylation. Moreover, treating Nm23H1-depleted cells with the AKT inhibitor MK2206 recovered CLDN1 expression, and diminished the invasiveness of ESCC cells. Finally, decreased expressions of both CLDN1 and E-cadherin were observed at the invasive front of the Nm23H1-negative tumors. Overall, our current study documented that reduced Nm23H1 expression activates the AKT signaling pathway, results in diminished CLDN1 expression and potentiates invasiveness of ESCC cells. Enhancement of Nm23H1 expression, inhibition of the AKT signaling pathway, or combined, might be a potential treatment strategy in selective ESCC patients.

Characterization of Functional Domains in NME1L Regulation of NF-κB Signaling

NME1 is a well-known metastasis suppressor which has been reported to be downregulated in some highly aggressive cancer cells. Although most studies have focused on NME1, the NME1 gene also encodes the protein (NME1L) containing N-terminal 25 extra amino acids by alternative splicing. According to previous studies, NME1L has potent anti-metastatic activity, in comparison with NME1, by interacting with IKKβ and regulating its activity. In the present study, we tried to define the role of the N-terminal 25 amino acids of NME1L in NF-κB activation signaling. Unfortunately, the sequence itself did not interact with IKKβ, suggesting that it may be not enough to constitute the functional structure. Further construction of NME1L fragments and biochemical analysis revealed that N-terminal 84 residues constitute minimal structure for homodimerization, IKKβ interaction and regulation of NF-κB signaling. The inhibitory effect of the fragment on cancer cell migration and NF-κB-stimulated gene expression was equivalent to that of whole NME1L. The data suggest that the N-terminal 84 residues may be a core region for the anti-metastatic activity of NME1L. Based on this result, further structural analysis of the binding between NME1L and IKKβ may help in understanding the anti-metastatic activity of NME1L and provide direction to NME1L and IKKβ-related anti-cancer drug design.

NM23-H1 expression of head and neck squamous cell carcinoma in association with the response to cisplatin treatment

We recently reported that low NM23-H1 expression of head and neck squamous cell carcinoma (HNSCC) correlated with poor patients' prognosis. Growing evidence has indicated that high tumor NM23-H1 expression contributes to a good response to chemotherapy. Therefore, we investigated the role of NM23-H1 in susceptibility of HNSCC cells to cisplatin and its clinical significance, as well as the in vitro study for validation was performed. Using immunohistochemistry, we analyzed NM23-H1 expression in surgical specimens from 46 HNSCC patients with cervical metastases receiving surgery and adjuvant chemoradiotherapy. Low tumor NM23-H1 expression correlated with locoregional recurrence of HNSCC following postoperative cisplatin-based therapy (p = 0.056) and poor patient prognosis (p = 0.001). To validate the clinical observation and the effect of NM23-H1 on cisplatin cytotoxicity, we established several stable clones derived from a human HNSCC cell line (SAS) by knockdown and overexpression. Knockdown of NM23-H1 attenuated the chemosensitivity of SAS cells to cisplatin, which was associated with reduced cisplatin-induced S-phase accumulation and downregulation of cyclin E1 and A. Overexpression of NM23-H1 reversed these results, indicating the essential role of NM23-H1 in treatment response to cisplatin. NM23-H1 may participate in HNSCC cell responses to cisplatin and be considered a potential therapeutic target.

Hepatocellular Carcinoma Growth Is Inhibited by Euphorbia helioscopia L. Extract in Nude Mice Xenografts

Euphorbia helioscopia L. is a traditional Chinese medicine; recently research found that its ethyl acetate extract (EAE) plays an important role on tumor cell proliferation, apoptosis, invasion, and metastasis in vitro. But the effect of EAE for tumor cells in vivo has not been reported. To explore the inhibitory effect of EAE and molecular mechanism on hepatocellular carcinoma (HCC) SMMC-7721 cells in vivo, we utilized the nude mouse xenograft model of HCC. Treated with EAE (50, 100, and 200 μg/mL), the volume of xenograft was measured during the entire process of EAE treatment. In EAE treatment group, the volume of xenograft was significantly reduced compared with the control group (P < 0.05) and the protein expressions of CyclinD1, bcl-2, and MMP-9 were reduced, while those of bax, caspase-3, and nm23-H1 were increased. A significant change trend with increasing EAE concentrations has presented, compared with controls. Moreover, the ultrastructural morphology of xenografts showed significant changes, including nuclear pyknosis and chromatin condensation, We found that EAE could effectively inhibit tumor growth, induce apoptosis, and inhibit tumor invasion and metastasis in vivo; it is suggested that EAE is a potential candidate for as a new anticancer agent.

Regulation of the metastasis suppressor Nm23-H1 by tumor viruses

Metastasis is the most common cause of cancer mortality. To increase the survival of patients, it is necessary to develop more effective methods for treating as well as preventing metastatic diseases. Recent advancement of knowledge in cancer metastasis provides the basis for development of targeted molecular therapeutics aimed at the tumor cell or its interaction with the host microenvironment. Metastasis suppressor genes (MSGs) are promising targets for inhibition of the metastasis process. During the past decade, functional significance of these genes, their regulatory pathways, and related downstream effector molecules have become a major focus of cancer research. Nm23-H1, first in the family of Nm23 human homologues, is a well-characterized, anti-metastatic factor linked with a large number of human malignancies. Mounting evidence to date suggests an important role for Nm23-H1 in reducing virus-induced tumor cell motility and migration. A detailed understanding of the molecular association between oncogenic viral antigens with Nm23-H1 may reveal the underlying mechanisms for tumor virus-associated malignancies. In this review, we will focus on the recent advances to our understanding of the molecular basis of oncogenic virus-induced progression of tumor metastasis by deregulation of Nm23-H1.

A splicing variant of NME1 negatively regulates NF-κB signaling and inhibits cancer metastasis by interacting with IKKβ

IKKβ functions as a principal upstream activator of the canonical NF-κB pathway by phosphorylating IκB, leading to its proteasomal degradation. Because IKKβ is considered a therapeutic target, understanding its regulation may facilitate the design of efficient regulators of this molecule. Here, we report a novel IKKβ-interacting molecule, NME1L, a splicing variant of the NME1 protein. NME1 has attracted attention in cancer research because of its antimetastatic activity and reduced expression in multiple aggressive types of cancer. However, the effect was just moderate but not dramatic in anti-cancer activities. We found that only NME1L interacts with IKKβ. Exogenous expression of NME1L resulted in a potent decrease in TNFα-stimulated NF-κB activation, whereas knockdown of NME1/NME1L with shRNA enhanced activity of NF-κB. NME1L down-regulates IKKβ signaling by blocking IKKβ-mediated IκB degradation. When NME1L was introduced into highly metastatic HT1080 cells, the mobility was efficiently inhibited. Furthermore, in a metastasis assay, NME1L-expressing cells did not colonize the lung. Based on these results, NME1L is a potent antimetastatic protein and may be a useful weapon in the fight against cancers.

Reduced expression of AMPK-β1 during tumor progression enhances the oncogenic capacity of advanced ovarian cancer

AMP-activated protein kinase (AMPK) is a key energy sensor that is involved in regulating cell metabolism. Our previous study revealed that the subunits of the heterotimeric AMPK enzyme are diversely expressed during ovarian cancer progression. However, the impact of the variable expression of these AMPK subunits in ovarian cancer oncogenesis remains obscure. Here, we provide evidence to show that reduced expression of the AMPK-β1 subunit during tumor progression is associated with the increased oncogenic capacity of advanced ovarian cancer cells. Immunohistochemical analysis revealed that AMPK-β1 levels were reduced in advanced-stage (P = 0.008), high-grade (P = 0.013) and metastatic ovarian cancers (P = 0.008). Intriguingly, down-regulation of AMPK-β1 was progressively reduced from tumor stages 1 to 3 of ovarian cancer. Functionally, enforced expression of AMPK-β1 inhibited ovarian-cancer-cell proliferation, anchorage-independent cell growth, cell migration and invasion. Conversely, depletion of AMPK-β1 by siRNA enhanced the oncogenic capacities of ovarian cancer cells, suggesting that the loss of AMPK-β1 favors the aggressiveness of ovarian cancer. Mechanistically, enforced expression of AMPK-β1 increased AMPK activity, which, in turn, induced cell-cycle arrest via inhibition of AKT/ERK signaling activity as well as impaired cell migration/invasion through the suppression of JNK signaling in ovarian cancer cells. Taken together, these findings suggest that the reduced expression of AMPK-β1 confers lower AMPK activity, which enhances the oncogenic capacity of advanced-stage ovarian cancer.

Metastasis suppressors in breast cancers: mechanistic insights and clinical potential

For the most part, normal epithelial cells do not disseminate to other parts of the body and proliferate, as do metastatic cells. Presumably, a class of molecules-termed metastasis suppressors-are involved in this homeostatic control. Metastasis suppressors are, by definition, cellular factors that, when re-expressed in metastatic cells, functionally inhibit metastasis without significantly inhibiting tumor growth. In this brief review, we catalog known metastasis suppressors, what is known about their mechanism(s) of action, and experimental and clinical associations to date.

Extracellular NM23 Signaling in Breast Cancer: Incommodus Verum

The notion that breast cancers can survive in an individual patient in a dormant state only to grow as metastatic disease in the future, is in our view incontrovertibly established. Convincing too is the evidence that surgery to remove the primary tumor often terminates dormancy resulting in accelerated relapses. Accepting that many deaths due to breast cancer might be averted were we to understand the cellular mechanisms underlying escape from dormancy, we have examined the extracellular signals produced by breast cancers derived from women with metastatic breast disease. In this perspective, we explore the role of extracellular nucleotide signaling that we have proposed constitutes a pathological axis from the transformed tumor cell to the endothelium in the service of intravasation, dissemination, extravasation and angiogenesis. A role for the dinucleotide kinase NM23/NDPK (nucleoside diphosphate kinase) secreted by breast tumor cells in the generation of signals that stimulate vascular leakiness, anti-thrombosis, endothelial migration and growth, constitutes a mechanistic basis for escape from latency and offers putative therapeutic targets for breast cancer management not previously appreciated.

Plakoglobin represses SATB1 expression and decreases in vitro proliferation, migration and invasion

Plakoglobin (γ-catenin) is a homolog of β-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of plakoglobin during tumorigenesis and metastasis, we expressed plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following plakoglobin expression in the very low plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, plakoglobin expression resulted in decreased in vitro proliferation, migration and invasion in different carcinoma cell lines. Together with the results of our previous studies, the data suggests that plakoglobin suppresses tumorigenesis and metastasis through the regulation of genes involved in these processes.

c-Abl and Arg induce cathepsin-mediated lysosomal degradation of the NM23-H1 metastasis suppressor in invasive cancer

Metastasis suppressors comprise a growing class of genes whose downregulation triggers metastatic progression. In contrast to tumor suppressors, metastasis suppressors are rarely mutated or deleted, and little is known regarding the mechanisms by which their expression is downregulated. Here, we demonstrate that the metastasis suppressor, NM23-H1, is degraded by lysosomal cysteine cathepsins (L,B), which directly cleave NM23-H1. In addition, activation of c-Abl and Arg oncoproteins induces NM23-H1 degradation in invasive cancer cells by increasing cysteine cathepsin transcription and activation. Moreover, c-Abl activates cathepsins by promoting endosome maturation, which facilitates trafficking of NM23-H1 to the lysosome where it is degraded. Importantly, the invasion- and metastasis-promoting activity of c-Abl/Arg is dependent on their ability to induce NM23-H1 degradation, and the pathway is clinically relevant as c-Abl/Arg activity and NM23-H1 expression are inversely correlated in primary breast cancers and melanomas. Thus, we demonstrate a novel mechanism by which cathepsin expression is upregulated in cancer cells (via Abl kinases). We also identify a novel role for intracellular cathepsins in invasion and metastasis (degradation of a metastasis suppressor). Finally, we identify novel crosstalk between oncogenic and metastasis suppressor pathways, thereby providing mechanistic insight into the process of NM23-H1 loss, which may pave the way for new strategies to restore NM23-H1 expression and block metastatic progression.

Insights into the biology and prevention of tumor metastasis provided by the Nm23 metastasis suppressor gene

Metastatic disease is the major cause of death among cancer patients. A class of genes, named metastasis suppressors, has been described to specifically regulate the metastatic process. The metastasis suppressor genes are downregulated in the metastatic lesion compared to the primary tumor. In this review, we describe the body of research surrounding the first metastasis suppressor identified, Nm23. Nm23 overexpression in aggressive cancer cell lines reduced their metastatic potential in vivo with no significant reduction in primary tumor size. A complex mechanism of anti-metastatic action is unfolding involving several known Nm23 enzymatic activities (nucleotide diphosphate kinase, histidine kinase, and 3'-5' exonuclease), protein-protein interactions, and downstream gene regulation properties. Translational approaches involving Nm23 have progressed to the clinic. The upregulation of Nm23 expression by medroxyprogesterone acetate has been tested in a phase II trial. Other approaches with significant preclinical success include gene therapy using traditional or nanoparticle delivery, and cell permeable Nm23 protein. Recently, based on the inverse correlation of Nm23 and LPA1 expression, a LPA1 inhibitor has been shown to both inhibit metastasis and induce metastatic dormancy.

Targeting tumor metastasis by regulating Nm23 gene expression

The Nm23 gene is a metastatic suppressor identified in a melanoma cell line and expressed in different tumors where their levels of expression are associated with reduced or increased metastatic potential. Nm23 is one of the over 20 metastasis suppressor genes (MSGs) confirmed in vivo. It is highly conserved from yeast to human, implying a critical developmental function. Tumors with alteration of the p53 gene and reduced expression of the Nm23 gene are more prone to metastasis. Nm23-H1 has 3'-5' exonuclease activity. This review focuses on the role of Nm23 in cancer progression and also a potential novel target for cancer therapy.

Nm23-H1 nuclear expression is associated with a more favourable prognosis in laryngeal carcinoma: univariate and multivariate analysis

AIMS

To use image analysis and multivariate analysis to investigate the prognostic significance of Nm23-H1 subcellular localization in a large cohort of laryngeal squamous cell carcinomas (LSCCs).

METHODS AND RESULTS

Nm23-H1 total and nuclear levels were immunohistochemically determined and calculated with an image analysis system in 104 consecutively operated LSCCs. The mean follow-up was 58.3 ± 35.1 months (median 45 months). Total Nm23-H1 levels correlated only with patient stratification by pT (P=0.01). Mean nuclear Nm23-H1 levels were lower in patients with recurrent disease (P=0.01), and disease-free survival (DFS) was longer in patients whose nuclear levels of Nm23-H1 were >2.0% than in those with levels ≤ 2.0% (P=0.019). On multivariate analysis, Nm23-H1 nuclear expression [hazard ratio (HR) 2.59, P=0.005] and N stage (HR 3.60, P=0.0001) were prognostically significant in relation to DFS.

CONCLUSIONS

In LSCC, Nm23-H1 nuclear expression may be useful for identifying patients at higher risk of recurrence after treatment and who might be considered for more aggressive therapy. Further investigations are needed before Nm23-H1 can be considered for use in targeted treatments for LSCC.

[NM23, an example of a metastasis suppressor gene]

Metastasis suppressor genes - unlike tumor suppressor genes - are defined by their capacity to control metastatic dissemination in vivo without affecting growth of the primary tumor. The first of these metastasis suppressor genes, NM23, was identified in 1988. Since then, expression of NM23 has been studied widely in human tumor cohorts, often with contradictory results. Not only is NM23 overexpressed in most human solid tumors when compared to healthy tissues, but also low expression of NM23 correlates with metastasis and poor clinical prognosis in the advanced stages of a number of epithelial cancer types, including melanoma, breast, colon, and liver carcinoma. This does not hold true, however, for other cancer types such as neuroblastoma and hematological malignancies, in which high NM23 expression correlates with more aggressive disease. Genetic alterations in the NM23 gene - loss of heterozygosity, spontaneous mutations and polymorphisms - are rarely found in tumors; thus, the metastatic potential of tumor cells is probably affected by NM23 protein levels. Three lines of evidence demonstrate the anti-metastatic activity of NM23: first, overexpression of NM23 in metastatic cell lines reduces their metastatic potential in xenograft models; second, the incidence of lung metastases is elevated in NM23 knockout mice prone to develop hepatocellular carcinoma, and, third, silencing NM23 by RNA interference confers a "metastatic phenotype" on non-invasive human epithelial liver and colon cancer cell lines. It appears that NM23 is crucial for inhibiting invasive migration, so acting at early stages of metastatic dissemination. The mechanistic basis of the metastasis suppressor function of NM23 and its regulated expression still remains obscure, however. Reactivation of expression of the endogenous NM23 gene in tumor cells, or stimulation of the pathways it controls, constitutes a promising avenue for anti-metastatic therapy.

RhoGDI2 suppresses lung metastasis in mice by reducing tumor versican expression and macrophage infiltration

Half of patients with muscle-invasive bladder cancer develop metastatic disease, and this is responsible for most of the deaths from this cancer. Low expression of RhoGTP dissociation inhibitor 2 (RhoGDI2; also known as ARHGDIB and Ly-GDI) is associated with metastatic disease in patients with muscle-invasive bladder cancer. Moreover, a reduction in metastasis is observed upon reexpression of RhoGDI2 in xenograft models of metastatic cancer. Here, we show that RhoGDI2 suppresses lung metastasis in mouse models by reducing the expression of isoforms V1 and V3 of the proteoglycan versican (VCAN; also known as chondroitin sulfate proteoglycan 2 [CSPG2]). In addition, we found that high versican levels portended poor prognosis in patients with bladder cancer. The functional importance of tumor expression of versican in promoting metastasis was established in in vitro and in vivo studies in mice that implicated a role for the chemokine CCL2 (also known as MCP1) and macrophages. Further analysis indicated that RhoGDI2 suppressed metastasis by altering inflammation in the tumor microenvironment. In summary, we demonstrate what we believe to be a new mechanism of metastasis suppression that works by reducing host responses that promote metastatic colonization of the lung. Therapeutic targeting of these interactions may provide a novel adjuvant strategy for delaying the appearance of clinical metastasis in patients.

Plakoglobin: role in tumorigenesis and metastasis

Plakoglobin (γ-catenin) is a member of the Armadillo family of proteins and a homolog of β-catenin. As a component of both the adherens junctions and desmosomes, plakoglobin plays a pivotal role in the regulation of cell-cell adhesion. Furthermore, similar to β-catenin, plakoglobin is capable of participating in cell signaling. However, unlike β-catenin that has well-documented oncogenic potential through its involvement in the Wnt signaling pathway, plakoglobin generally acts as a tumor/metastasis suppressor. The exact roles that plakoglobin plays during tumorigenesis and metastasis are not clear; however, recent evidence suggests that it may regulate gene expression, cell proliferation, apoptosis, invasion, and migration. In this paper, we describe plakoglobin, its discovery and characterization, its role in regulating cell-cell adhesion, and its signaling capabilities in regulation of tumorigenesis and metastasis.

Targeting lysophosphatidic acid receptor type 1 with Debio 0719 inhibits spontaneous metastasis dissemination of breast cancer cells independently of cell proliferation and angiogenesis

Metastasis is the main cause of death for cancer patients. Targeting factors that control metastasis formation is a major challenge for clinicians. Lysophosphatidic acid (LPA) is a bioactive phospholipid involved in cancer. LPA activates at least six independent G protein-coupled receptors (LPA_1–6). Tumor cells frequently co-express multiple LPA receptors, puzzling the contribution of each one to cancer progression. All three receptors, LPA₁, LPA₂ and LPA₃, act as oncogenes and prometastatic factors in the mouse mammary gland. The competitive inhibitor of LPA₁ and LPA₃ receptors, Ki16425, inhibits efficiently breast cancer bone metastases in animal models. We showed here that Debio 0719, which corresponds to the R-stereoisomer of Ki16425 exhibited highest antagonist activities at LPA₁ (IC₅₀=60 nM) and LPA₃ (IC₅₀=660 nM) than Ki16425 [IC₅₀=130 nM (LPA₁); IC₅₀=2.3 μM (LPA₃)]. In vitro, Debio 0719, inhibited LPA-dependent invasion of the 4T1 mouse mammary cancer cells. In vivo, early but not late administration of Debio 0719 (50 mg/kg p.o. twice daily) to BALB/c mice during the course of orthotopic 4T1 primary tumor growth reduced the number of spontaneously disseminated tumor cells to bone and lungs without affecting the growth of primary tumors and tumor-induced angiogenesis. We found that increased LPA₁ mRNA expression in primary tumors of breast cancer patients correlated significantly with their positive lymph node status (p<0.001). Altogether, our results suggest that LPA₁ controls early events of metastasis independently of cell proliferation and angiogenesis. Therefore, targeting this receptor with Debio 0719 has a high therapeutic potential against metastasis formation for breast cancer patients.

Protein-protein interactions: a mechanism regulating the anti-metastatic properties of Nm23-H1

Nm23-H1, also known as NDPK-A, was the first of a class of metastasis suppressor genes to be identified. Overexpression of Nm23-H1 in metastatic cell lines (melanoma, breast carcinoma, prostate, colon, hepatocellular, and oral squamous cell carcinoma) reduced cell motility in in vitro assays and metastatic potential in xenograft models, without a significant effect on primary tumor size. The mechanism of Nm23-H1 suppression of metastasis, however, is incompletely understood. Nm23-H1 has been reported to bind proteins, including those in small G-protein complexes, transcriptional complexes, the Map kinase, the TGF-β signaling pathways and the cytoskeleton. Evidence supporting these associations is presented together with evidence of resultant biochemical and phenotypic consequences of association. Cumulatively, the data suggest that part of the anti-metastatic function of Nm23-H1 lies in pathways that it interrupts via binding and inactivation of proteins.

Protein-protein interactions: a mechanism regulating the anti-metastatic properties of Nm23-H1

Nm23-H1, also known as NDPK-A, was the first of a class of metastasis suppressor genes to be identified. Overexpression of Nm23-H1 in metastatic cell lines (melanoma, breast carcinoma, prostate, colon, hepatocellular, and oral squamous cell carcinoma) reduced cell motility in in vitro assays and metastatic potential in xenograft models, without a significant effect on primary tumor size. The mechanism of Nm23-H1 suppression of metastasis, however, is incompletely understood. Nm23-H1 has been reported to bind proteins, including those in small G-protein complexes, transcriptional complexes, the Map kinase, the TGF-β signaling pathways and the cytoskeleton. Evidence supporting these associations is presented together with evidence of resultant biochemical and phenotypic consequences of association. Cumulatively, the data suggest that part of the anti-metastatic function of Nm23-H1 lies in pathways that it interrupts via binding and inactivation of proteins.

Building on the foundation of daring hypotheses: using the MKK4 metastasis suppressor to develop models of dormancy and metastatic colonization

The identification of a novel metastasis suppressor function for the MAP Kinase Kinase 4 protein established a role for the stress-activated kinases in regulating the growth of disseminated cancer cells. In this review, we describe MKK4's biological mechanism of action and how this information is being used to guide the development of new models to study cancer cell dormancy and metastatic colonization. Specifically, we describe the novel application of microvolume structures, which can be modified to represent characteristics similar to those that cancer cells experience at metastatic sites. Although MKK4 is currently one of many known metastasis suppressors, this field of research started with a single daring hypothesis, which revolutionized our understanding of metastasis, and opened up new areas of exploration for basic research. The combination of our increasing knowledge of metastasis suppressors and such novel technologies provide hope for possible clinical interventions to prevent suffering from the burden of metastatic disease.

Functional modulation of the metastatic suppressor Nm23-H1 by oncogenic viruses

Evidence over the last two decades from a number of disciplines has solidified some fundamental concepts in metastasis, a major contributor to cancer associated deaths. However, significant advances have been made in controlling this critical cellular process by focusing on targeted therapy. A key set of factors associated with this invasive phenotype is the nm23 family of over twenty metastasis-associated genes. Among the eight known isoforms, Nm23-H1 is the most studied potential anti-metastatic factor associated with human cancers. Importantly, a growing body of work has clearly suggested a critical role for Nm23-H1 in limiting tumor cell motility and progression induced by several tumor viruses, including Epstein-Barr virus (EBV), Kaposi's sarcoma associated herpes virus (KSHV) and human papilloma virus (HPV). A more in depth understanding of the interactions between tumor viruses encoded antigens and Nm23-H1 will facilitate the elucidation of underlying mechanism(s) which contribute to virus-associated cancers. Here, we review recent studies to explore the molecular links between human oncogenic viruses and progression of metastasis, in particular the deregulation of Nm23-H1 mediated suppression.

Learning about the functions of NME/NM23: lessons from knockout mice to silencing strategies

The human NME gene family (also known as NM23) comprises ten genes that are involved in diverse physiological and pathological processes including proliferation, differentiation, development, ciliary functions, and metastasis. For the moment, only the NME1, NME2, and NME7 genes have been inactivated in transgenic knockout mice, as well as a double NME1-NME2 gene knockout. Mice lacking NME1 or NME2 grow to adulthood without health problems, although NME1 (-/-) mice have modest growth retardation. Double knockout NME1 (-/-)-NME2 (-/-) mice, by contrast, are highly hypotrophic and die at birth from profound anemia due to impaired erythroblast development. Evidence for a metastasis suppressor function of NME1 in vivo comes from crossing NME1 (-/-) mice with mice prone to develop hepatocellular carcinoma; the double transgenic mice present a higher incidence of lung metastases. Silencing of NME1 by siRNA interference has confirmed this function by conferring a "metastatic phenotype" on non-invasive human epithelial cancer cell lines. This function is specific to NME1 and is not observed when the NME2 is silenced. The data indicate that NME1 loss is causally involved at the early stages of the metastatic cascade. NME2 (-/-) mice and NME2 silencing experiments reveal a specific role of NME2 in activation of heterotrimeric G proteins and of KCa3.1 channel in T cells, pointing to a role of NME2 as a histidine phosphotransferase. Regarding NME7, consistent with its expression in axonemal structures, NME7 (-/-) mice present lesions similar to primary ciliary dyskinesia. This review summarizes the recent data obtained by knockout and silencing of NME/NM23 genes that provide mechanistic insights into their respective roles in physiology and pathology.

Mechanisms of non-metastatic 2 (NME2)-mediated control of metastasis across tumor types

Non-metastatic 23 [NM23/nucleoside diphosphate kinases (NDPK)] genes are the first discovered metastasis suppressor genes. More than two decades of research has demonstrated their roles in a variety of biological processes with NME1 and NME2 being most studied in the context of metastasis suppression. Although NME1 and NME2 share >85% homology at amino acid level, they show redundant as well as unique molecular functions. Phenotypic analyses of knockout (KO) mice for NM23 members (NDPK-A, B) and compound KO (A as well as B) showed requirement of both proteins in hematopoiesis suggesting shared functions in development disease. Several reviews have discussed NME1, however the role of NME2 appears to be relatively less understood in the context of metastasis suppression. Here, we focus on NME2 and by meta-analysis of gene expression from multiple tumor types, and survey of in vivo and vitro studies, suggest the possibility that NME2 may be one of the key factors in metastasis. This along with the relevance of normal physiological functions of NME2 in the context of metastasis is discussed. We further examined the genetic and epigenetic features of NME2 and NME1 gene promoters and found aspects of transcription control that could be unique to NME2/NME1. Findings on signaling pathways and small molecules which regulate the expression of NME2 that could be therapeutically important are also discussed.

Metastasis-suppressor genes in clinical practice: lost in translation?

Over the past 25 years, an expanding set of metastasis-suppressor genes (MSGs) has been identified that specifically regulate metastasis formation without affecting primary growth. MSGs are involved in diverse molecular processes in multiple tumor types. Given the wealth of metastasis biology that underlies their functions, treatment strategies based on MSGs have an unparalleled potential to improve patient care. Using NM23 as a prime example, we discuss how specific MSGs have been used as prognostic markers, tools for predicting response to treatment, and targets for the development of novel therapies. Barriers specific to the translation of MSG biology into clinical practice are reviewed and future research directions necessary for clinical advances are delineated. Although to date the impact of MSGs on patient care is limited, it is an expanding field with vast potential to help develop new treatments and identify patients who will most benefit from them.

Aggregation of the neuroblastoma-associated mutant (S120G) of the human nucleoside diphosphate kinase-A/NM23-H1 into amyloid fibrils

The human nucleoside diphosphate (NDP) kinase A, product of the NME1 gene also named NM23-H1, is known as a metastasis suppressor protein. A naturally occurring variant, S120G, identified in neuroblastomas, possesses native three-dimensional structure and enzymatic activity but displays reduced conformational stability and a folding defect with the accumulation of a "molten globule" folding intermediate during refolding in vitro. As such intermediate has been postulated to be involved in amyloid formation, NDP kinase A may serve as a model protein for studying the relationship between folding intermediates and amyloid fibrils. The NDP kinase A S120G was heated in phosphate buffer (pH 7.0). The protein precipitated as amyloid fibrils, as demonstrated by electron microscopy, Congo red, and thioflavin T binding and FTIR spectroscopy. The NDP kinase A S120G, at neutral pH and at moderate temperature experiences a transition towards amyloid fibrils. The aggregation process was faster if seeded by preformed fibrils. The fibrils presented a large proteinase K-resistant core not including residue Gly 120, as shown by mass spectrometry. This suggests that the aggregation process is triggered by the reduced stability of the S120G variant and not by a specific increase in the kinase domain intrinsic aggregation propensity at the place of mutation. This constitutes one of the few reports on a protein involved in cancer biology able to aggregate into amyloid structures under mild conditions.

Expression of nm23-H1 is associated with poor prognosis in peripheral T-cell lymphoma, not otherwise specified

PURPOSE

We examined whether nm23-H1 is a prognostic factor of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS).

EXPERIMENTAL DESIGN

We studied 102 consecutive, untreated PTCL-NOS patients from 1998 to 2008. The expression of nm23-H1 and TIA-1 was studied by immunohistochemistry.

RESULTS

nm23-H1 was positive in 44.1% and TIA-1 in 78.4% of the PTCL-NOS patients. nm23-H1 expression was not correlated with age, performance status (PS), lactate dehydrogenase (LDH) level, or stage but was significantly correlated with the prognostic index for T-cell lymphoma. The serum nm23-H1 level was 43.44 ng/mL in the cytoplasmic nm23-H1 strongly positive, 24.32 ng/mL in the cytoplasmic nm23-H1 moderately positive, and 13.64 ng/mL in the cytoplasmic nm23-H1-negative patients. The nm23-H1-positive group had significantly shorter overall survival (OS). TIA-1 had no prognostic impact on 5-year OS rates. OS was significantly shorter in patients with the following clinicopathologic features: age 60 or more years, PS of 2 to 4, LDH level greater than normal, bone marrow involvement, or nm23-H1-positive lymphoma. Multivariate analysis confirmed nm23-H1 expression to be an independent prognostic factor.

CONCLUSIONS

The nm23-H1 protein may be an important prognostic factor in PTCL-NOS. Because our results suggested that nm23-HI is produced by lymphoma cells, we expect to see the development of new treatments targeting nm23 overexpression.