Tumor cell autocrine motility factor

Osteopontin knockdown suppresses the growth and angiogenesis of colon cancer cells

AIM: To investigate the effects of osteopontin (OPN) gene expression knockdown on colon cancer Lovo cells in vitro.

METHODS: Four candidate small interfering RNA (siRNA) constructs targeting the OPN gene and a scrambled control sequence (NC-siRNA) were synthesized and inserted into a pGPU6/GFP/Neo expression vector. After confirmation by restriction enzyme digestion and DNA sequencing, the recombinant plasmids were subsequently transfected into a human colon cancer cell line (Lovo) using a liposome transfection method. Stably transfected cells were maintained with G418 selection and referred to as Lovo-OPN-1, -2, -3, -4, and Lovo-NC cells. Knockdown efficiency of each of the four siRNA constructs was determined by real-time reverse transcription polymerase chain reaction assays and western blotting, and the construct with the most effective silencing was used for subsequent experiments. Cell proliferation, adhesion, and Matrigel invasion assays were performed to analyze the effects of OPN knockdown in stably transfected Lovo cells. The levels of four angiogenic factors, namely vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-2, MMP-9 and urokinase plasminogen activator were detected by enzyme-linked immunosorbent assays (ELISA).

RESULTS: Recombinant vectors containing OPN-specific and scrambled siRNA sequences were successfully constructed and stably transfected into Lovo cells. Compared with the control Lovo and Lovo-NC cells, the levels of OPN mRNA and protein expression in Lovo-OPN-1, -2, -3, and -4 were significantly reduced (all P < 0.05), with the most efficient reduction observed in Lovo-OPN-4 cells (P < 0.05). Relative to untransfected Lovo cells, OPN mRNA expression levels in Lovo-NC and Lovo-OPN-4 cells were 1.008 ± 0.067 and 0.160 ± 0.023, respectively. The relative OPN protein expression levels in Lovo, Lovo-NC, and Lovo-OPN-4 cells were 3.024 ± 0.211, 2.974 ± 0.630, and 0.121 ± 0.008, respectively. Moreover, transfection with the scrambled sequence had no effect on the expression of OPN. After 24, 48, 72, and 96 h of cultivation, absorption values at 450 nm to assess proliferation of Lovo-OPN-4 cells were 0.210 ± 0.017, 0.247 ± 0.024, 0.314 ± 0.037, and 0.359 ± 0.043, respectively, which were significantly lower than those of Lovo (0.244 ± 0.031, 0.313 ± 0.024, 0.513 ± 0.048 and 0.783 ± 0.051) and Lovo-NC cells (0.241 ± 0.029, 0.309 ± 0.022, 0.563 ± 0.023, and 0.735 ± 0.067) (all P < 0.05). The absorption values at 595 nm, which were measured in a cell adhesion assay, showed that adhesion of Lovo-OPN-4 cells (0.215 ± 0.036) was significantly decreased compared to Lovo (0.490 ± 0.037) and Lovo-NC cells (0.462 ± 0.043) (P < 0.05). The number of invasive Lovo-OPN-4 cells (16.1 ± 1.9) was also significantly decreased compared to Lovo (49.9 ± 5.4) and Lovo-NC cells (48.8 ± 4.5) (P < 0.05). ELISA assays showed significant reductions in Lovo-OPN-4 cells compared to Lovo and Lovo-NC cells with regard to the expression of VEGF (1687.85 ± 167.84 ng/L vs 2348.54 ± 143.80 ng/L and 2284.39 ± 138.62 ng/L, respectively), MMP-2 (2966.07 ± 177.36 μg/L vs 4084.74 ± 349.54 μg/L and 4011.41 ± 424.48 μg/L, respectively), MMP-9 (3782.89 ± 300.64 μg/L vs 5062.90 ± 303.02 μg/L and 4986.38 ± 300.75 μg/L, respectively) and uPA (1152.69 ± 120.79 μg/L vs 1380.90 ± 147.25 μg/L and 1449.80 ± 189.92 μg/L, respectively) (all P < 0.05).

CONCLUSION: Knockdown of OPN gene expression suppresses colon cancer cell growth, adherence, invasion, and expression of angiogenic factors.

Increased migration of human mesenchymal stromal cells by autocrine motility factor (AMF) resulted in enhanced recruitment towards hepatocellular carcinoma

Background and Aims

Several reports described the migration of human mesenchymal stromal cells (MSCs) towards tumor-released factors. Autocrine motility factor (AMF) is produced by several tumors including hepatocellular carcinoma (HCC). The aim of this study was to analyze AMF involvement on MSC migration towards human HCC.

Methods

Production of AMF by HCC tumors was evaluated by western analysis. The effects of AMF on MSCs from different sources (bone marrow, adipose tissue and perivascular cells from umbilical cord) were analyzed using in vitro migration assay; metalloproteinase 2 (MMP2) activity and expression of critical genes were studied by zymography and qRT-PCR, respectively. To assess AMF involvement on the in vivo MSC migration, noninvasive fluorescence imaging was performed. To test the effect of AMF-primed MSCs on tumor development, in vitro proliferation and spheroids growth and in vivo tumor volume were evaluated.

Results

AMF produced by HCC was found to induce migration of different MSCs in vitro and to enhance their MMP2 activity. Stimulation of MSCs with recombinant AMF (rAMF) also induced the in vitro adhesion to endothelial cells in coincidence with changes in the expression levels of MMP3, AMF receptor, caveolin-1, and -2 and GDI-2. Importantly, stimulation of MSCs with rAMF increased the in vivo migration of MSCs towards experimental HCC tumors. AMF-priming of MSCs did not induce a pro-tumorigenic effect on HCC cells neither in vivo nor in vitro.

Conclusion

AMF plays a role in MSC recruitment towards HCC. However, its ability to increase MSC migration to HCC for therapeutic purposes merits further evaluation.

Regulation of mitochondrial antiviral signaling (MAVS) expression and signaling by the mitochondria-associated endoplasmic reticulum membrane (MAM) protein Gp78

In a previous study, we identified the E3 ubiquitin ligase Gp78 by RNAi high-throughput screening as a gene whose depletion restricted enterovirus infection. In the current study, we show that Gp78, which localizes to the ER-mitochondria interface, is a regulator of RIG-I-like receptor (RLR) antiviral signaling. We show that depletion of Gp78 results in a robust decrease of vesicular stomatitis virus (VSV) infection and a corresponding enhancement of type I interferon (IFN) signaling. Mechanistically, we show that Gp78 modulates type I IFN induction by altering both the expression and signaling of the mitochondria-localized RLR adaptor mitochondrial antiviral signaling (MAVS). Expression of mutants of Gp78 that abolish its E3 ubiquitin ligase and its participation in ER-associated degradation (ERAD) lost their ability to degrade MAVS, but surprisingly maintained their ability to repress RLR signaling. In contrast, Gp78 lacking its entire C terminus lost both its ability to degrade MAVS and repress RLR signaling. We show that Gp78 interacts with both the N- and C-terminal domains of MAVS via its C-terminal RING domain, and that this interaction is required to abrogate Gp78-mediated attenuation of MAVS signaling. Our data thus implicate two parallel pathways by which Gp78 regulates MAVS signaling; one pathway requires its E3 ubiquitin ligase and ERAD activity to directly degrade MAVS, whereas the other pathway occurs independently of these activities, but requires the Gp78 RING domain and occurs via a direct association between this region and MAVS.

Differential expression of fascin, E-cadherin and vimentin: Proteins associated with survival of cholangiocarcinoma patients

INTRODUCTION

This study investigated the differential expression of fascin, E-cadherin and vimentin in human carcinogenesis.

METHODS

This study detected their expressions in 142 cholangiocarcinoma and 20 benign bile duct tissue specimens using immunohistochemistry. Clinicopathologic characteristics and survival data were also collected and analyzed for their association with expression of these 3 proteins.

RESULTS

The data showed that both fascin and vimentin proteins were significantly overexpressed in cholangiocarcinoma, whereas E-cadherin expression was reduced in cholangiocarcinoma compared with normal tissues. Fascin protein expression was associated with tumor dedifferentiation, venous invasion and lymph node or distant metastasis. Similarly, vimentin expression was associated with tumor dedifferentiation and venous invasion, as well as hepatitis virus infection. In contrast, loss of E-cadherin expression was associated with tumor dedifferentiation (P < 0.05). Because the functions of these 3 proteins were closely related, the data showed that fascin and E-cadherin protein expression was reversely associated. However, fascin and vimentin protein expression was positively associated with cholangiocarcinoma. Cox multiple regression analysis showed that distant tumor metastasis, tumor differentiation and overexpression of fascin and vimentin proteins were all independent risk factors for prognosis (P < 0.05).

CONCLUSION

The data from the current study demonstrated that overexpression of fascin and vimentin proteins could be further evaluated as biomarkers for the prediction of cholangiocarcinoma patient survival.

p53 regulates glucose metabolism by miR-34a

Cancer cells rely mainly on glycolysis rather than mitochondrial respiration for energy production, which is called the Warburg effect. p53 mutations are observed in about half of cancer cases, and p53 controls the cell cycle and cell death in response to cellular stressors. p53 has been emphasized as a metabolic regulator involved in glucose, glutamine, and purine metabolism. Here, we demonstrated metabolic changes in cancer that occurred through p53. We found that p53-inducible microRNA-34a (miR-34a) repressed glycolytic enzymes (hexokinase 1, hexokinase 2, glucose-6-phosphate isomerase), and pyruvate dehydrogenase kinase 1. Treatment with an anti-miR-34a inhibitor relieved the decreased expression in these enzymes following DNA damage. miR-34a-mediated inhibition of these enzymes resulted in repressed glycolysis and enhanced mitochondrial respiration. The results suggest that p53 has a miR-34a-dependent integrated mechanism to regulate glucose metabolism.

The hyaluronan synthesis inhibitor 4-methylumbelliferone exhibits antitumor effects against mesenchymal-like canine mammary tumor cells

Hyaluronan (HA), a principal constituent of the extracellular matrix (ECM), mediates growth and metastasis of tumor cells. The role of HA in the epithelial-mesenchymal transition (EMT) is well known, and increased ECM remodeling is observed in mesenchymal-like cells. The HA synthesis inhibitor 4-methylumbelliferone (4-MU) is anti-tumorigenic for various malignant tumors. However, the antitumor effect of 4-MU against canine mammary tumor cells that possess a mesenchymal-like phenotype is unclear. We examined the antitumor effect of 4-MU on CF41.Mg mesenchymal-like canine mammary tumor cells. We investigated the influence of 4-MU on the expression of HA synthase (HAS) 1-3 mRNA and observed dose-dependent downregulation of HAS2 mRNA at 24-72 h; in contrast, HAS3 expression was elevated at 24 h. Thus, 4-MU inhibited HA synthesis via HAS2 repression. 4-MU also inhibited cell proliferation and induced apoptosis in the CF41.Mg cells. Our experiments showed that 4-MU-induced apoptosis in CF41.Mg cells involved induction of the pro-apoptotic gene BAX. We also assessed motility and found that 4-MU reduced chemokinesis and chemotaxis in CF41.Mg cells. Our data suggest that 4-MU may serve as a candidate therapeutic agent for the treatment of canine mammary tumors. Since 4-MU exhibits antitumor activity in mesenchymal-like cells, it may also be a useful inhibitor of canine mammary tumor invasion and metastasis.

Autocrine motility factor promotes HER2 cleavage and signaling in breast cancer cells

Trastuzumab (Herceptin) is an effective targeted therapy in HER2-overexpressing human breast carcinoma. However, many HER2-positive patients initially or eventually become resistant to this treatment, so elucidating mechanisms of trastuzumab resistance that emerge in breast carcinoma cells is clinically important. Here, we show that autocrine motility factor (AMF) binds to HER2 and induces cleavage to the ectodomain-deleted and constitutively active form p95HER2. Mechanistic investigations indicated that interaction of AMF with HER2 triggers HER2 phosphorylation and metalloprotease-mediated ectodomain shedding, activating phosphoinositide-3-kinase (PI3K) and mitogen-activated protein kinase signaling and ablating the ability of trastuzumab to inhibit breast carcinoma cell growth. Furthermore, we found that HER2 expression and AMF secretion were inversely related in breast carcinoma cells. On the basis of this evidence that AMF may contribute to HER2-mediated breast cancer progression, our findings suggest that AMF-HER2 interaction might be a novel target for therapeutic management of patients with breast cancer, whose disease is resistant to trastuzumab.

Interleukin-8 (CXCL8) in tumor associated non-vascular extracellular fluids: its diagnostic and prognostic values. A review

Interleukin-8 (IL-8, CXCL8) was originally discovered as a powerful attractor and activator of polymorphonuclear leukocytes. It was soon recognized that IL-8 also affects proliferation and migration of cancer cells, tumor angiogenesis and metastasis, and that it is expressed in many cancerous cell types. IL-8 protein expression is usually increased in serum of cancer patients, but markedly higher concentrations are found in cancer-associated non-vascular extracellular fluids, such as pleural effusion, ascites and cyst fluid. Elevated concentrations of IL-8 are indicative of malignant processes also in cerebrospinal fluid, urine, saliva, interstitial fluid and cervicovaginal secretions. Higher IL-8 levels are typically found in high-grade peritumoral fluids rather than low-grade tumors and benign conditions, with the exception of inflammatory processes. In line with recent molecular biology investigations, it appears that the local IL-8 production is related to its malignant origin and to tumor progression. Hence, IL-8 in peritumoral fluid is to be taken into consideration while assessing tumor character and monitoring the tumor progression/remission status. Besides, the data here collected justify the attempts to find an IL-8-targeted inhibitory therapy

Synthesis and evaluation of malonate-based inhibitors of phosphosugar-metabolizing enzymes: class II fructose-1,6-bis-phosphate aldolases, type I phosphomannose isomerase, and phosphoglucose isomerase

In the design of inhibitors of phosphosugar metabolizing enzymes and receptors with therapeutic interest, malonate has been reported in a number of cases as a good and hydrolytically-stable surrogate of the phosphate group, since both functions are dianionic at physiological pH and of comparable size. We have investigated a series of malonate-based mimics of the best known phosphate inhibitors of class II (zinc) fructose-1,6-bis-phosphate aldolases (FBAs) (e.g., from Mycobacterium tuberculosis), type I (zinc) phosphomannose isomerase (PMI) from Escherichia coli, and phosphoglucose isomerase (PGI) from yeast. In the case of FBAs, replacement of one phosphate by one malonate on a bis-phosphorylated inhibitor (1) led to a new compound (4) still showing a strong inhibition (K(i) in the nM range) and class II versus class I selectivity (up to 8×10(4)). Replacement of the other phosphate however strongly affected binding efficiency and selectivity. In the case of PGI and PMI, 5-deoxy-5-malonate-D-arabinonohydroxamic acid (8) yielded a strong decrease in binding affinities when compared to its phosphorylated parent compound 5-phospho-D-arabinonohydroxamic acid (2). Analysis of the deposited 3D structures of the kinetically evaluated enzymes complexed to the phosphate-based inhibitors indicate that malonate could be a good phosphate surrogate only if phosphate is not tightly bound at the enzyme active site, such as in position 7 of compound 1 for FBAs. These observations are of importance for further design of inhibitors of phosphorylated-compounds metabolizing enzymes with therapeutic interest.

Phosphoglucose isomerase/autocrine motility factor mediates epithelial-mesenchymal transition regulated by miR-200 in breast cancer cells

Phosphoglucose isomerase/autocrine motility factor (PGI/AMF) plays an important role in glycolysis and gluconeogenesis and is associated with invasion and metastasis of cancer cells. We have previously shown its role in the induction of epithelial-mesenchymal transition (EMT) in breast cancer cells, which led to increased aggressiveness; however, the molecular mechanism by which PGI/AMF regulates EMT is not known. Here we show, for the first time, that PGI/AMF overexpression led to an increase in the DNA-binding activity of NF-κB, which, in turn, led to increased expression of ZEB1/ZEB2. The microRNA-200s (miR-200s) miR-200a, miR-200b, and miR-200c are known to negatively regulate the expression of ZEB1/ZEB2, and we found that the expression of miR-200s was lost in PGI/AMF overexpressing MCF-10A cells and in highly invasive MDA-MB-231 cells, which was consistent with increased expression of ZEB1/ZEB2. Moreover, silencing of PGI/AMF expression in MDA-MB-231 cells led to overexpression of miR-200s, which was associated with reversal of EMT phenotype (i.e., mesenchymal-epithelial transition), and these findings were consistent with alterations in the relative expression of epithelial (E-cadherin) and mesenchymal (vimentin, ZEB1, ZEB2) markers and decreased aggressiveness as judged by clonogenic, motility, and invasion assays. Moreover, either reexpression of miR-200 or silencing of PGI/AMF suppressed pulmonary metastases of MDA-MB-231 cells in vivo, and anti-miR-200 treatment in vivo resulted in increased metastases. Collectively, these results suggest a role of miR-200s in PGI/AMF-induced EMT and thus approaches for upregulation of miR-200s could be a novel therapeutic strategy for the treatment of highly invasive breast cancer.

Silencing of autocrine motility factor induces mesenchymal-to-epithelial transition and suppression of osteosarcoma pulmonary metastasis

Phosphoglucose isomerase (PGI) is a multifunctional enzyme that functions in glucose metabolism as a glycolytic enzyme catalyzing an interconversion between glucose and fructose inside the cell, while it acts as cytokine outside the cell, with properties that include autocrine motility factor (AMF)-regulating tumor cell motility. Overexpression of AMF/PGI induces epithelial-to-mesenchymal transition with enhanced malignancy. Recent studies have revealed that silencing of AMF/PGI resulted in mesenchymal-to-epithelial transition (MET) of human lung fibrosarcoma cells and breast cancer cells with reduced malignancy. Here, we constructed a hammerhead ribozyme specific against GUC triplet at the position G390 in the human, mouse, and rat AMF/PGI mRNA sequence. Mesenchymal human osteosarcoma MG-63, HS-Os-1, and murine LM8 cells were stably transfected with the ribozyme specific for AMF/PGI. The stable transfectant cells showed effective downregulation of AMF/PGI expression and subsequent abrogation of AMF/PGI secretion, which resulted in morphologic change with reduced growth, motility, and invasion. Silencing of AMF/PGI induced MET, in which upregulation of E-cadherin and cytokeratins, as well as downregulation of vimentin, were noted. The MET guided by AMF/PGI gene silencing induced osteosarcoma MG-63 to terminally differentiate into mature osteoblasts. Furthermore, MET completely suppressed the tumor growth and pulmonary metastasis of LM8 cells in nude mice. Thus, acquisition of malignancy might be completed in part by upregulation of AMF/PGI, and waiver of malignancy might also be controlled by downregulation of AMF/PGI.

Utility of functional imaging in prediction or assessment of treatment response and prognosis following thermotherapy

The purpose of this review is to examine the roles that functional imaging may play in prediction of treatment response and determination of overall prognosis in patients who are enrolled in thermotherapy trials, either in combination with radiotherapy, chemotherapy or both. Most of the historical work that has been done in this field has focused on magnetic resonance imaging/magnetic resonance spectroscopy (MRI/MRS) methods, so the emphasis will be there, although some discussion of the role that positron emission tomography (PET) might play will also be examined. New optical technologies also hold promise for obtaining low cost, yet valuable physiological data from optically accessible sites. The review is organised by traditional outcome parameters: local response, local control and progression-free or overall survival. Included in the review is a discussion of future directions for this type of translational work.

Metabolic genes in cancer: their roles in tumor progression and clinical implications

Re-programming of metabolic pathways is a hallmark of physiological changes in cancer cells. The expression of certain genes that directly control the rate of key metabolic pathways including glycolysis, lipogenesis and nucleotide synthesis are drastically altered at different stages of tumor progression. These alterations are generally considered as an adaptation of tumor cells; however, they also contribute to the progression of tumor cells to become more aggressive phenotypes. This review summarizes the recent information about the mechanistic link of these genes to oncogenesis and their potential utility as diagnostic markers as well as for therapeutic targets. We particularly focus on three groups of genes; GLUT1, G6PD, TKTL1 and PGI/AMF in glycolytic pathway, ACLY, ACC1 and FAS in lipogenesis and RRM2, p53R2 and TYMS for nucleotide synthesis. All these genes are highly up-regulated in a variety of tumor cells in cancer patients, and they play active roles in tumor progression rather than expressing merely as a consequence of phenotypic change of the cancer cells. Molecular dissection of their orchestrated networks and understanding the exact mechanism of their expression will provide a window of opportunity to target these genes for specific cancer therapy. We also reviewed existing database of gene microarray to validate the utility of these genes for cancer diagnosis.

A role for KAI1 in promotion of cell proliferation and mammary gland hyperplasia by the gp78 ubiquitin ligase

Expression of gp78, an E3 ubiquitin ligase in endoplasmic reticulum-associated degradation, is associated with tumor malignancy. To study gp78 overexpression in mammary gland development and tumorigenicity, we generated murine mammary tumor virus (MMTV) long terminal repeat-driven gp78 transgenic mice. Embryos carrying the gp78 transgene cassette were implanted in FVB surrogate mothers, and two founders with high copy integration showed elevated gp78 expression at both transcript and protein levels at the virgin stage and at 12 days gestation. Transgenic mammary glands showed increased ductal branching, dense alveolar lobule formation, and secondary terminal end bud development. Bromodeoxyuridine staining showed increased proliferation in hyperplastic ductal regions at the virgin stage and at 12 days gestation compared with wild type mice. Reduced expression of the metastasis suppressor KAI1, a gp78 endoplasmic reticulum-associated degradation substrate, demonstrates that gp78 ubiquitin ligase activity is increased in MMTV-gp78 mammary gland. Similarly, metastatic MDA-435 cells exhibit increased gp78 expression, decreased KAI1 expression, and elevated proliferation compared with nonmetastatic MCF7 cells whose proliferation was enhanced upon knockdown of KAI1. Importantly, stable gp78 knockdown HEK293 cells showed increased KAI1 expression and reduced proliferation that was rescued upon KAI1 knockdown, demonstrating that gp78 regulation of cell proliferation is mediated by KAI1. Mammary tumorigenesis was not observed in repeatedly pregnant MMTV-long terminal repeat-gp78 transgenic mice over a period of 18 months post-birth. Elevated gp78 ubiquitin ligase activity is therefore not sufficient for mammary tumorigenesis. However, the hyperplastic phenotype observed in mammary glands of MMTV-gp78 transgenic mice identifies a novel role for gp78 expression in enhancing mammary epithelial cell proliferation and nontumorigenic ductal outgrowth.

Phosphoglucose isomerase/autocrine motility factor promotes melanoma cell migration through ERK activation dependent on autocrine production of interleukin-8

It is well known that phosphoglucose isomerase/autocrine motility factor (AMF) promotes cell migration in an autocrine manner in various tumor cells. However, it remains unclear whether certain cytokines modulate the effects of AMF on tumor cell migration. Because interleukin (IL)-8, a proinflammatory cytokine, is produced by melanoma cells and has been correlated with melanoma migration, the migratory ability of melanoma cells induced by AMF may also involve induction of IL-8 expression. In the present study, we assessed whether AMF promotes melanoma cell migration through autocrine production of IL-8. We found that AMF stimulation increased IL-8 production through up-regulation of IL-8 mRNA transcription, especially in biologically early stage melanoma cells. AMF-induced migration of these cells was inhibited by a specific neutralizing antibody against IL-8. The IL-8 production induced by AMF was mediated by the ERK1/2 pathways. These findings suggest that melanoma migration induced by AMF is mediated by autocrine production of IL-8 as a novel downstream modulator of the AMF signaling pathway.

Autotaxin

Autotaxin is a protein of approximately 900 amino acids discovered in the early 1990s. Over the past 15 years, a strong association between cancer cells and autotaxin production has been observed. Recent publications indicate that autotaxin and the capacity of cancer to metastasise are intimately linked. The discovery of new molecular targets in pharmacology is a mixture of pure luck, hard work and industrial strategy. Despite a crucial and desperate need for new therapeutic tools, many targets are approached in oncology, but only a few are validated and end up at the patient bed. Outside the busy domain of kinases, few targets have been discovered that can be useful in treating cancer, particularly metastatic processes. The fortuitous relationship between autotaxin and lysophosphatidic acid renders the results of observations made in the diabetes/obesity context considerably important. The literature provides observations that may aid in redesigning experiments to validate autotaxin as a potential oncology target.

AMF/G6PI induces differentiation of leukemic cells via an unknown receptor that differs from gp78

Autocrine Motility Factor (AMF)/maturation factor (MF)/neuroleukin (NLK) is a multifunctional protein, which acts as a glucose 6-phosphate isomerase (G6PI) intracellularly. Exto-G6PI stimulates invasion and metastasis of tumor cells, neurotropic growth and differentiation of leukemic cells. The cell motility and proliferation receptor is known to be gp78 (78 kilo-Dalton glycoprotein), which has seven transmembrane domains in its N-terminal region, but the maturation factor receptor remains unclear. The human acute monocytic leukemia line does not express gp78 and its motile activity is not enhanced by AMF though it is well differentiated by AMF exposure. The forced expression of gp78 in leukemic cells recovered acceptable motile stimulation, concomitant with reduced differentiation ability. Two unknown proteins were detected by crosslinking between AMF and leukemic cells. The results of this report suggest that the receptor molecule for AMF/NLK/MF in leukemic differentiation is not gp78.

The complex biology of autocrine motility factor/phosphoglucose isomerase (AMF/PGI) and its receptor, the gp78/AMFR E3 ubiquitin ligase

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits a dual function as an extracellular cytokine, under the name autocrine motility factor (AMF). Its cell surface receptor, gp78/AMFR, is also localized to the endoplasmic reticulum where it functions as an E3 ubiquitin ligase. Expression of both AMF/PGI and gp78/AMFR is associated with cancer and, in this review, we will discuss various aspects of the biology of this ligand-receptor complex and its role in tumor progression.

Trophoblast infiltration

Sexual reproduction in the ocean necessitates only the combination of gametes, followed by absorption of nutrients and oxygen from the surrounding watery medium. As life moved from the sea to the land, reproductive strategies required compensation for the loss of this aquatic environment. For the mammals, and scattered other animals, the solution to this problem was the development of the placenta, the means by which the fetus extracts nutrients from its environment. As the animals that utilized the placenta evolved from small rodent-like creatures with short gestations to larger animals with prolonged gestations, the demands of the developing fetus grew. Whereas the placenta of the fetal pig, with a gestational period of a little less than four months, can extract sufficient nutrients from the mother by simple diffusion across the uterus to the placenta, the human fetus needs a far more complex uteroplacental relationship.

Enzymatic function of multiple origins regulates the progression of colorectal cancer and the development of metastases

Enzymes play a crucial role in the progression of colorectal cancer and the development of metastases. They facilitate malignant cell invasion through the degradation of the extracellular matrix, the rupture of the basement membrane and the derangement of cell-cell adhesion. Furthermore, they promote tumour cell migration and support the evolution of metastatic lesions in the liver and other organs, through multiple molecular mechanisms, including growth factor release and angiogenesis. Urokinase plasminogen activator system, matrix metalloproteinases, heparanase and autocrine motility factor constitute important enzymatic complexes which assist colorectal cancer growth, with potential clinical applications in the diagnosis and treatment of the disease.

Raft-dependent endocytosis of autocrine motility factor/phosphoglucose isomerase: a potential drug delivery route for tumor cells

Background

Autocrine motility factor/phosphoglucose isomerase (AMF/PGI) is the extracellular ligand for the gp78/AMFR receptor overexpressed in a variety of human cancers. We showed previously that raft-dependent internalization of AMF/PGI is elevated in metastatic MDA-435 cells, but not metastatic, caveolin-1-expressing MDA-231 cells, relative to non-metastatic MCF7 and dysplastic MCF10A cells suggesting that it might represent a tumor cell-specific endocytic pathway.

Methodology/Principal Findings

Similarly, using flow cytometry, we demonstrate that raft-dependent endocytosis of AMF/PGI is increased in metastatic HT29 cancer cells expressing low levels of caveolin-1 relative to metastatic, caveolin-1-expressing, HCT116 colon cells and non-metastatic Caco-2 cells. Therefore, we exploited the raft-dependent internalization of AMF/PGI as a potential tumor-cell specific targeting mechanism. We synthesized an AMF/PGI-paclitaxel conjugate and found it to be as efficient as free paclitaxel in inducing cytotoxicity and apoptosis in tumor cells that readily internalize AMF/PGI compared to tumor cells that poorly internalize AMF/PGI. Murine K1735-M1 and B16-F1 melanoma cells internalize FITC-conjugated AMF/PGI and are acutely sensitive to AMF/PGI-paclitaxel mediated cytotoxicity in vitro. Moreover, following in vivo intratumoral injection, FITC-conjugated AMF/PGI is internalized in K1735-M1 tumors. Intratumoral injection of AMF/PGI-paclitaxel induced significantly higher tumor regression compared to free paclitaxel, even in B16-F1 cells, known to be resistant to taxol treatment. Treatment with AMF/PGI-paclitaxel significantly prolonged the median survival time of tumor bearing mice. Free AMF/PGI exhibited a pro-survival role, reducing the cytotoxic effect of both AMF/PGI-paclitaxel and free paclitaxel suggesting that AMF/PGI-paclitaxel targets a pathway associated with resistance to chemotherapeutic agents. AMF/PGI-FITC uptake by normal murine spleen and thymus cells was negligible both in vitro and following intravenous injection in vivo where AMF/PGI-FITC was selectively internalized by subcutaneous B16-F1 tumor cells.

Conclusions/Significance

The raft-dependent endocytosis of AMF/PGI may therefore represent a tumor cell specific endocytic pathway of potential value for drug delivery to tumor cells.

Drug development against metastasis-related genes and their pathways: a rationale for cancer therapy

It is well recognized that the majority of cancer related deaths is caused by metastatic diseases. Therefore, there is an urgent need for the development of therapeutic intervention specifically targeted to the metastatic process. In the last decade, significant progress has been made in this research field, and many new concepts have emerged that shed light on the molecular mechanism of metastasis cascade which is often portrayed as a succession of six distinct steps; localized invasion, intravasation, translocation, extravasation, micrometastasis and colonization. Successful metastasis is dependent on the balance and complex interplay of both the metastasis promoters and suppressors in each step. Therefore, the basic strategy of our interventions is aimed at either blocking the promoters or potentiating the suppressors in this disease process. Toward this goal, various kinds of antibodies and small molecules have been designed. These include agents that block the ligand-recepter interaction of metastasis promoters (HGF/c-Met), antagonize the metastasis-promoting enzymes (AMF, uPA and MMP) and inhibit the transcriptional activity of metastasis promoter (beta-Catenin). On the other hand, the intriguing roles of metastasis suppressors and their signal pathways have been extensively studied and various attempts have been made to potentiate these factors. Small molecules have been developed to restore the expression or mimic the function of metastasis-suppressor genes such as NM23, E-cadherin, Kiss-1, MKK4 and NDRG1, and some of them are under clinical trials. This review summarizes our current understanding of the molecular pathway of tumor metastasis and discusses strategies and recent development of anti-metastatic drugs.

AMF/PGI transactivates the MMP-3 gene through the activation of Src-RhoA-phosphatidylinositol 3-kinase signaling to induce hepatoma cell migration

We have previously shown that AMF/PGI induces hepatoma cell migration through the induction of MMP-3. This work investigates how AMF/PGI activates the MMP-3 gene. We demonstrated that AMF/PGI transactivates the MMP-3 gene promoter through AP-1. The transactivation and induction of cell migration effect of AMF/PGI directly correlates with its enzymatic activity. Various analyses showed that AMF/PGI stimulated the Src-RhoA-PI3-kinase signaling pathway, and these three signaling molecules could form a complex. Our results demonstrate a new mechanism of AMF/PGI-induced cell migration and a link between Src-RhoA-PI3-kinase, AP-1, MMP-3 and hepatoma cell migration.

Metastasis signatures: genes regulating tumor-microenvironment interactions predict metastatic behavior

The possibility of predicting clinical outcome of cancer patients through the analysis of gene expression profiles in the primary tumor is a kind of ideological revolution as the multistep carcinogenesis model postulates that the proportion of cells within the primary tumor that actually acquire metastasis driving mutation(s) is small; too small to leave its imprint on the gene expression profile. The data collected to date have brought a new paradigm to reality in the metastasis field: metastasis must at least in part rely on mutations and/or gene regulation events present in the majority of cells which constitute the primary tumor mass. By analyses of differential expression of primary tumors versus metastases or by functional analyses of putative metastasis genes in experimental metastasis, many metastasis-associated gene expression events have been identified that correlate with the development of metastases. Among genes "favoring" metastasis, we find many molecules that are expressed not by the tumor cell itself but by the cells of the microenvironment, as well as genes over-expressed in the primary tumor that have a principle role in mediating tumor-host interactions. Here we review these concepts and advance hypotheses on how gene expression of the primary tumor and the microenvironment can favor the spread of the metastasis seeds and how this knowledge can provide tools to secondary prevention.

Prognostic significance of 18F-FDG uptake in primary osteosarcoma after but not before chemotherapy: a possible association with autocrine motility factor/phosphoglucose isomerase expression

Response to neoadjuvant chemotherapy is a significant prognostic factor for osteosarcoma (OS). 18-F-fluorodeoxy-D: -glucose (FDG) positron emission tomography (PET) is a noninvasive imaging modality that correlates with histological grading in musculoskeletal sarcomas. To determine the prognostic value of FDG PET in patients receiving chemotherapy, 13 patients were evaluated by FDG-PET, and followed for more than 4 years. FDG PET standardized uptake values before (SUV1) and after (SUV2) chemotherapy were analyzed and correlated with the expression of metastasis-related glycolytic enzyme, autocrine motility factor (AMF)/phosphoglucose isomerase (PGI) by immunohistochemical examination in surgically excised tumors. Although mean SUV1 for OS patients with metastatic lesions were similar to those in the completely disease-free (CDF) group (6.5 vs. 6.6, respectively, P = 0.975), mean SUV2 for OS with metastatic lesions were significantly higher than those in the CDF group (5.1 vs. 2.5, respectively, P = 0.0445). Interestingly, immunohistochemical analysis using anti-AMF/PGI antibody revealed that SUV2 correlated significantly with the AMF/PGI staining titers (P = 0.0303), while no correlation between SUV1 and the AMF/PGI staining titers existed (P = 0.964). The present study suggests that FDG PET after chemotherapy may provide information for AMF/PGI-related metastatic potentiality of residual tumors located out side of the area surgically resected afterward, and then lead to a useful prediction of the patients' prognosis.

The role of autocrine motility factor in tumor and tumor microenvironment

Autocrine motility factor (AMF) is a tumor-secreted cytokine and is abundant at tumor sites, where it may affect the process of tumor growth and metastasis. AMF is a multifunctional protein capable of affecting cell migration, invasion, proliferation, and survival, and possesses phosphoglucose isomerase activity and can catalyze the step in glycolysis and gluconeogenesis. Here, we review the role of AMF and tumor environment on malignant processes. The outcome of metastasis depends on multiple interactions between tumor cells and homeostatic mechanisms, therefore elucidation of the tumor/host interactions in the tumor microenvironment is essential in the development of new prevention and treatment strategies. Such knowledge might provide clues to develop new future therapeutic approaches for human cancers.

Oncogene induction of metastases

A metastatic colony is the end result of a complex series of steps involving multiple gene products. In some cases, the augmented metastatic potential of certain tumour cells may be due to the increased expression of specific gene products which confer a selective advantage. Transfection of the c-Ha-ras oncogene into suitable recipient cells constitutes a powerful experimental model with which to identify putative gene products augmented in highly metastatic tumour cells compared to their non-metastatic counterparts. Transfection of the activated ras oncogene into 3T3 and 10T1/2 embryo fibroblasts, and adult rat fibroblasts, results in transformants which produce high numbers of spontaneous metastases in nude mice or syngeneic recipients. The ras oncogene will also increase the metastatic aggressiveness of murine tumours with low metastatic potential. However, the ras oncogene will not induce the metastatic phenotype in all recipient cells. Furthermore, specific genes such as adenovirus 2 E1A suppress the ability of ras to induce the metastatic phenotype. Natural 'suppressor' gene products may exist which render certain cells resistant to the induction of metastases by ras. Ras oncogene transfection induces the production of type IV collagenase, motility factors and growth factors. The ras oncogene therefore induces a cascade of gene functions leading to rapid progression to the metastatic phenotype. The mechanism of the induction probably involves complex interactions between the ras p21 product and multiple cellular gene products.

Induction of epithelial to mesenchymal transition in PMC42-LA human breast carcinoma cells by carcinoma-associated fibroblast secreted factors

Background

Breast carcinoma is accompanied by changes in the acellular and cellular components of the microenvironment, the latter typified by a switch from fibroblasts to myofibroblasts.

Methods

We utilised conditioned media cultures, Western blot analysis and immunocytochemistry to investigate the differential effects of normal mammary fibroblasts (NMFs) and mammary cancer-associated fibroblasts (CAFs) on the phenotype and behaviour of PMC42-LA breast cancer cells. NMFs were obtained from a mammary gland at reduction mammoplasty, and CAFs from a mammary carcinoma after resection.

Results

We found greater expression of myofibroblastic markers in CAFs than in NMFs. Medium from both CAFs and NMFs induced novel expression of α-smooth muscle actin and cytokeratin-14 in PMC42-LA organoids. However, although conditioned media from NMFs resulted in distribution of vimentin-positive cells to the periphery of PMC42-LA organoids, this was not seen with CAF-conditioned medium. Upregulation of vimentin was accompanied by a mis-localization of E-cadherin, suggesting a loss of adhesive function. This was confirmed by visualizing the change in active β-catenin, localized to the cell junctions in control cells/cells in NMF-conditioned medium, to inactive β-catenin, localized to nuclei and cytoplasm in cells in CAF-conditioned medium.

Conclusion

We found no significant difference between the influences of NMFs and CAFs on PMC42-LA cell proliferation, viability, or apoptosis; significantly, we demonstrated a role for CAFs, but not for NMFs, in increasing the migratory ability of PMC42-LA cells. By concentrating NMF-conditioned media, we demonstrated the presence of factor(s) that induce epithelial-mesenchymal transition in NMF-conditioned media that are present at higher levels in CAF-conditioned media. Our in vitro results are consistent with observations in vivo showing that alterations in stroma influence the phenotype and behaviour of surrounding cells and provide evidence for a role for CAFs in stimulating cancer progression via an epithelial-mesenchymal transition. These findings have implications for our understanding of the roles of signalling between epithelial and stromal cells in the development and progression of mammary carcinoma.

Moving in the right direction-nanoimaging in cancer cell motility and metastasis

Although genetic and protein manipulations have been the cornerstone for the study and understanding of biological processes for many decades, complimentary nanoscale observations have only more recently been achieved in the live-imaging mode. It is at the nano measurement level that events such as protein-protein interactions, enzymatic conversions, and single-molecule stochastic behavior take place. Therefore, nanoscale observations allow us to reinterpret knowledge from large-scale or bulk techniques and gain new insight into molecular events that has cellular, tissue, and organismal phenotypic manifestations. This review identifies pertinent questions relating to the sensing and directional component of cancer cell chemotaxis and discusses the platforms that provide insight into the molecular events related to cell motility. The study of cell motility at the molecular imaging level often necessitates the use of devices such as microinjection, microfluidics, in vivo/intravital and in vitro chemotaxis assays, as well as fluorescence methods like uncaging and FRET. The micro- and nanofabricated devices that facilitate these techniques and their incorporation to specialized microscopes such as the multiphoton, AFM, and TIR-FM, for high-resolution imaging comprise the nanoplatforms used to explore the mechanisms of carcinogenesis. In real-time observations, within a milieu of physiological protein concentrations, true states of dynamic and kinetic fluxes can be monitored.

Histologic changes after meniscal repair using radiofrequency energy in rabbits

PURPOSE

Our purpose was to investigate histologic changes in the rabbit meniscus after meniscal repair via radiofrequency energy (RFE).

METHODS

Twenty Japanese white rabbits underwent bilateral knee arthrotomies, and a longitudinal tear was made in the avascular area of both medial menisci. On the right knees, RFE treatment (60 degrees C and 40 W) was performed on the femoral surface of the meniscal tear in monopolar mode. On the left knees, the meniscus was left untreated as a control. The rabbits were killed at 0, 1, 2, 4, or 12 weeks after surgery, and all medial menisci were examined histologically. The expression of autocrine motility factor in meniscal fibrochondrocytes was examined by immunohistochemical analysis.

RESULTS

Histologic examination at baseline showed fusion of collagen fibers in the tear. Failure of fusion was found in 2 of 4 menisci at 2 weeks and 1 of 4 menisci at 4 and 12 weeks. One week after surgery, the specimens showed an acellular area as a result of fibrochondrocyte death. The acellular area expanded deeper until 4 weeks and was reduced at 12 weeks. On the femoral surface of the RFE-treated area, fibroblast proliferation was found at 2 weeks, and fibroblasts had invaded into the meniscus tissue from the meniscal surface at 12 weeks. Immunohistochemical analysis showed that the expression of autocrine motility factor in RFE-treated menisci was significantly higher than that in control menisci from 1 to 12 weeks.

CONCLUSIONS

RFE treatment at 60 degrees C and 40 W fused the collagen fiber in the meniscal tear in rabbits just after surgery. After RFE treatment, an acellular area developed as a result of fibrochondrocyte damage. RFE caused fibroblast proliferation at 2 weeks. The acellular area was reduced by cell repopulation at 12 weeks.

CLINICAL RELEVANCE

RFE may induce fibroblast proliferation for meniscal repair.

Differential expression and pathological significance of autocrine motility factor/glucose-6-phosphate isomerase expression in human lung carcinomas

To clarify the involvement of autocrine motility factor (AMF) in the phenotype and biological profiles of human lung carcinomas, we analysed protein and mRNA expression in a total of 180 cases. Immunohistochemistry revealed positive staining in 67.2%, with the highest frequency in squamous cell carcinoma (SCC; 90.8%) and the lowest in small cell carcinoma (SmCC; 27.8%). In SCC, the staining frequency and intensity correlated with the degree of morphological differentiation. Generally, the expression levels in immunoblotting analysis corresponded well with immunohistochemical positivity. However, there was less agreement between protein and mRNA levels: in SmCC and large cell carcinomas (LCCs), mRNA showed higher, but protein showed lower expression. Among non-small cell lung carcinomas (NSCLCs), AMF protein levels correlated inversely with tumour size, but tumours exhibiting lymph node metastasis showed higher mRNA expression. In cultured lung carcinoma cells which comprised all histological subtypes, AMF was detected in the lysates of all ten cell lines. Secreted AMF protein was detected in the conditioned media from six cell lines, most of which were SmCC or LCC. Thus, a particular subset of lung carcinomas secrete AMF, which may promote cell motility via autocrine stimulation through its cognate receptor and cause the biological aggressiveness seen in SmCC and LCC. Moreover, treatment by proteasome inhibitors resulted in increased cellular AMF in five cell lines, suggesting that intracellular AMF levels are regulated by both secretion and proteasome-dependent degradation. In conclusion, AMF was detected in a major proportion of lung carcinomas, and may play a part not only in proliferation and/or progression of the tumours, but also, possibly, in the differentiation of SCC. Furthermore, higher mRNA expression may be related to the high metastatic potential of NSCLC and increased protein secretion, leading to a more aggressive phenotype, such as the invasiveness of SmCC and LCC.

Expression of autocrine motility factor mRNA is a poor prognostic factor in high-grade astrocytoma

It has been reported that tumor infiltration is correlated with the expression of autocrine motility factor (AMF) and its receptor 78 kDa glycoprotein (gp78). The purpose of the present study was to detect AMF and gp78 mRNA expression levels and their localization in high-grade astrocytomas (glioblastoma and anaplastic astrocytoma) and to determine whether AMF and gp78 are important prognostic factors. A total of 32 formalin-fixed and paraffin-embedded glioblastomas and 23 formalin-fixed and paraffin-embedded anaplastic astrocytomas was used. The expressions of AMF and gp78 mRNA were detected using the highly sensitive in situ hybridization method. The expression of AMF mRNA was detected in 27 of 32 glioblastomas (84.4%) and 11 of 23 anaplastic astrocytomas (47.8%). The positivity of AMF mRNA was significantly higher in glioblastomas than in anaplastic astrocytomas (P = 0.0094), but gp78 mRNA was detected in most cases and no statistical significance was observed. The overall survival of patients with AMF expression was significantly shorter than patients without AMF expression (P = 0.0175). In anaplastic astrocytomas, the overall survival of patients with AMF expression was also significantly shorter than in patients without AMF expression (P = 0.0058). This study demonstrated that AMF is a poor prognostic factor in high-grade astrocytomas.

Glycolysis inhibition for anticancer treatment

Most cancer cells exhibit increased glycolysis and use this metabolic pathway for generation of ATP as a main source of their energy supply. This phenomenon is known as the Warburg effect and is considered as one of the most fundamental metabolic alterations during malignant transformation. In recent years, there are significant progresses in our understanding of the underlying mechanisms and the potential therapeutic implications. Biochemical and molecular studies suggest several possible mechanisms by which this metabolic alteration may evolve during cancer development. These mechanisms include mitochondrial defects and malfunction, adaptation to hypoxic tumor microenvironment, oncogenic signaling, and abnormal expression of metabolic enzymes. Importantly, the increased dependence of cancer cells on glycolytic pathway for ATP generation provides a biochemical basis for the design of therapeutic strategies to preferentially kill cancer cells by pharmacological inhibition of glycolysis. Several small molecules have emerged that exhibit promising anticancer activity in vitro and in vivo, as single agent or in combination with other therapeutic modalities. The glycolytic inhibitors are particularly effective against cancer cells with mitochondrial defects or under hypoxic conditions, which are frequently associated with cellular resistance to conventional anticancer drugs and radiation therapy. Because increased aerobic glycolysis is commonly seen in a wide spectrum of human cancers and hypoxia is present in most tumor microenvironment, development of novel glycolytic inhibitors as a new class of anticancer agents is likely to have broad therapeutic applications.

Rapid chemokinetic movement and the invasive potential of lung cancer cells; a functional molecular study

Background

Non-small cell lung cancer is the most common cause of early casualty from malignant disease in western countries. The heterogeneous nature of these cells has been identified by histochemical and microarray biomarker analyses. Unfortunately, the morphological, molecular and biological variation within cell lines used as models for invasion and metastasis are not well understood. In this study, we test the hypothesis that heterogeneous cancer cells exhibit variable motility responses such as chemokinesis and chemotaxis that can be characterized molecularly.

Methods

A subpopulation of H460 lung cancer cells called KINE that migrated under chemokinetic (no gradient) conditions was harvested from Boyden chambers and cultured. Time-lapsed microscopy, immunofluorescence microscopy and microarray analyses were then carried out comparing chemokinetic KINE cells with the unselected CON cell population.

Results

Time-lapsed microscopy and analysis showed that KINE cells moved faster but less directionally than the unselected control population (CON), confirming their chemokinetic character. Of note was that chemokinetic KINE cells also chemotaxed efficiently. KINE cells were less adhesive to substrate than CON cells and demonstrated loss of mature focal adhesions at the leading edge and the presence of non-focalized cortical actin. These characteristics are common in highly motile amoeboid cells that may favour faster motility speeds. KINE cells were also significantly more invasive compared to CON. Gene array studies and real-time PCR showed the downregulation of a gene called, ROM, in highly chemokinetic KINE compared to mainly chemotactic CON cells. ROM was also reduced in expression in a panel of lung cancer cell lines compared to normal lung cells.

Conclusion

This study shows that cancer cells that are efficient in both chemokinesis and chemotaxis demonstrate high invasion levels. These cells possess different morphological, cytoskeletal and adhesive properties from another population that are only efficient at chemotaxis, indicating a loss in polarity. Understanding the regulation of polarity in the context of cell motility is important in order to improve control and inhibition of invasion and metastasis.

Antibody Responses Associated with the Graft-versus-Leukemia Effect in Adult T-Cell Leukemia

Adult T-cell leukemia (ATL) is a peripheral T-cell neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). The prognosis of ATL, especially the acute and lymphoma subtypes, is poor with conventional and high-dose chemotherapy. The effectiveness of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for ATL has been reported, suggesting the presence of a graft-versus-leukemia (GVL) effect against this malignancy. To identify the target antigens associated with tumor rejection, we used SEREX (serological identification of antigens by recombinant cDNA expression cloning) to screen ATL complementary DNA expression libraries with sera from an ATL patient who had a GVL response after allo-HSCT. Among the isolated clones, autocrine motility factor receptor (AMFR), which encodes a glycosylated transmembrane protein, was found to have selective reactivity with the sera obtained during tumor regression. Real-time reverse transcription polymerase chain reaction analysis for AMFR showed highest expression in the testis among normal tissues. Furthermore, aberrant AMFR expression was found in at least some ATL patients. Taken together, these findings suggest that AMFR may be one of the GVL antigens that provoke effective antitumor immunity against ATL in allogeneic settings.

The Autocrine Motility Factor (AMF) and AMF-receptor Combination Needs Sugar Chain Recognition Ability and Interaction Using the C-terminal Region of AMF

The autocrine motility factor (AMF) promotes cellular locomotion or invasion, and regulates tumor angiogenesis or ascites accumulation. These signals are triggered by binding between AMF and its receptor (AMFR), a glycoprotein on the cell surface. AMF has been identified as phosphohexose isomerase (PHI). Previous reports have suggested that the substrate-recognition of exo-PHI is significant for receptor binding. Crystallographic studies have shown that AMF consists of three domains, and that the substrate or inhibitor of PHI is stored between the large and small domains, corresponding to approximately residues 117-288. Here, site-directed mutagenesis was used to investigate 18 recombinant human AMF point mutants involving critical amino acid residues for substrate or enzyme inhibitor recognition or binding. Mutation of residues that interact with the phosphate group of the PHI substrate significantly reduced the cell motility-stimulating activity. Their binding capacities for AMFR were also lower than wild-type human AMF. Mutants that retained the enzymic activity showed the motility-stimulating effect and receptor binding and had sensitivity to a PHI inhibitor. Mutant AMFR lacking the N-sugar chain was expressed on the cell membrane but did not respond to AMF-stimulation, and N-glycosidase-treated AMFR did not compete with receptor binding of AMF. Furthermore, the AMF domains that contain the substrate storage domain and C-terminal region stimulate cell locomotion. These results suggest that the N-glyco side-chain of AMFR is a trigger and that interaction between the 117-C-terminal part of AMF and the extracellular core protein of AMFR is needed during AMF-AMFR interactions.

Systems analyses characterize integrated functions of biochemical networks

Metabolic, regulatory and signaling pathways have been characterized in detail over the past century. As the amount of genomic, proteomic and metabolic data has increased, and the mathematical and analytical capabilities of interrogating these data have advanced, the overlapping roles of pathway constituents have been described. These developments reflect the truly integrated nature of subcellular biochemical networks. Systems analyses, including the reconstruction of stoichiometric networks, provide a key set of tools for quantifying overlap among the metabolic, regulatory and signaling functions of network components. Accounting for this integration is crucial for accurately describing the function of biochemical networks.

Identification of large-scale molecular changes of Autotaxin(ENPP2) knock-down by small interfering RNA in breast cancer cells

To understand comprehensive molecular mechanisms by which Autotaxin (ENPP2) mediates, we identified large-scale molecular changes responsible for aberrant expression of Autotaxin (ATX) on breast cancer cells by using DNA microarrays. Transcriptional over-expression of ENPP2 gene was endogenously silenced by using RNA interference technique, and then recapitulated corresponding molecular changes in MDA435 breast cancer cells. Application of nonparametric Wilcoxon statistical analyses (P<0.05) and the selection criteria of 2-fold differential gene expression change resulted in the identification of 368 genes including 133 up-regulated and 235 genes under-expressed in ENPP2-silencing MDA435 cells. Most of the functional categories of identified genes are associated with cellular metabolism, cytoskeleton organization, transcription regulation, signal transduction as well as cellular organization and biogenesis. Our data suggest that the molecular signature identified by the ENPP2-silencing methods may represent potential candidates that can explain the complicated characteristics of ATX and may serve as biomarkers, for the development of molecular-targeting therapy, in human breast cancer.

Regulation of phosphoglucose isomerase/autocrine motility factor expression by hypoxia

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a housekeeping cytosolic enzyme of the sugar metabolism pathways that plays a key role in glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine with properties that include autocrine motility factor (AMF) eliciting mitogenic, motogenic, differentiation functions and has been implicated in tumor progression and metastasis. Since metastasis is regulated in part by hypoxia, which induces the transcription of metastasis-associated genes and anaerobic glycolic metabolism, we questioned whether hypoxia also regulates the expression level of tumor cells' PGI/AMF. We establish here that in the human breast carcinoma BT-549 cells hypoxia enhanced expression of the transcription factor hypoxia-inducible factor (HIF)-1, which in turn led to the up-regulation of PGI/AMF expression and was specifically inhibited by inhibitors of the phosphatidylinositol 3'-kinase signaling pathway. In addition, the hypoxia induction of PGI/AMF expression was suppressed by inhibitors of vascular endothelial growth factor (VEGF) or VEGF receptors, suggesting that hypoxia-inducible VEGF regulates the PGI/AMF expression. Hypoxia also enhanced cancer cell motility, and these effects were strongly inhibited by the PGI/AMF, VEGF, or VEGF receptor inhibitors. The results presented here suggest that under hypoxic conditions the expression of PGI/AMF is regulated in part by the HIF pathway, which in turn increases the flow of the glycolytic cascade leading to an increased anaerobic energy generation; thus, inhibition of PGI/AMF expression and activities may provide a new therapeutic modality for treatment of hypoxic tumors.

Malignant effusions are sources of fibronectin and other promigratory and proinvasive components

Metastatic dissemination is the primary cause of death in ovarian cancer (OvCa) patients, and dissemination to pleural and peritoneal effusions is a common clinical event. Effusion samples were collected from 15 OvCa patients. Twenty-six samples were collected prospectively, two were archival, and eight were taken from patients with other malignancies. Twenty-nine samples were from malignant ascites, and seven specimens were pleural fluids. In addition, six ascites and two pleural fluids from noncancer patients were studied as effusion controls. Effusion supernatants were tested for migration-stimulation activity, using A2058 human melanoma cells as the index responder cell. Malignant samples induced a 400-1200% increase in migration. Sixty percent of the migration was inhibited by incubation of the malignant fluid with antifibronectin (FN) antibody, in contrast to 75% inhibition of control fluid-stimulated migration (P = 0.017). Gelatin zymography and Western blot analyses showed that latent and activated MMP-2 and MMP-9 collagenases, and tissue inhibitor of metalloproteinase-2 (TIMP-2) were present in all malignant fluids. Serial samples were taken from several patients, and a trend for correlation between MMPs and clinical behavior of the tumors was shown. Free TIMP-2 correlated with CA-125 levels in two patients for whom serial samples were available. The demonstration of promigratory and proinvasive activity in malignant effusions is consistent with their association with other metastatic disease in OvCa patients and their function as a haven for metastatic cells.

Crystal Structures of Mouse Autocrine Motility Factor in Complex with Carbohydrate Phosphate Inhibitors Provide Insight into Structure–Activity Relationship of the Inhibitors

Autocrine motility factor (AMF), a tumor-secreted cytokine, stimulates cell migration in vitro and metastasis in vivo. AMF is identical to the extracellular cytokines neuroleukin and maturation factor and, interestingly, to the intracellular enzyme phosphoglucose isomerase. The cytokine activity of AMF is inhibited by carbohydrate phosphate compounds as they compete for AMF binding with the carbohydrate moiety of the AMF receptor (AMFR), which is a glycosylated seven transmembrane helix protein. Here, we report the first comprehensive high-resolution crystal structure analyses of the inhibitor-free form and the eight types of inhibitor (phosphate, erythrose 4-phosphate (E4P), arabinose 5-phosphate (A5P), sorbitol 6-phosphate (S6P), 6-phosphogluconic acid (6PGA), fructose 6-phosphate (F6P), glucose 6-phosphate (G6P), or mannose 6-phosphate (M6P)) complexes of mouse AMF (mAMF). We assayed the inhibitory activities of these inhibitors against the cytokine activity of mAMF. The inhibitory activities of the six-carbon sugars (G6P, F6P, M6P, and 6PGA) were found to be significantly higher than those of the four or five-carbon sugars (E4P or A5P). The inhibitory activities clearly depend on the length of the inhibitor molecules. A structural comparison revealed that a water-mediated hydrogen bond between one end of the inhibitor and a rigid portion of the protein surface in the shorter-chain inhibitor (E4P) complex is replaced by a direct hydrogen bond in the longer-chain inhibitor (6PGA) complex. Thus, to obtain a new compound with higher inhibitory activities against AMF, water molecules at the inhibitor binding site of AMF should be replaced by a functional group of inhibitors in order to introduce direct interactions with the protein surface. The present structure-activity relationship studies will be valuable not only for designing more effective AMF inhibitors but also for studying general protein-inhibitor interactions.

Autocrine motility factor/glucose-6-phosphate isomerase is a possible predictor of metastasis in bone and soft tissue tumours

In order to assess the involvement of autocrine motility factor (AMF) in mesenchymal tumours, AMF protein and mRNA expression was analysed in tumours, tumour-like lesions, and other lesions of bone and soft tissue. Immunohistochemical analysis of 200 cases revealed positive staining in 72.5% of the cases, suggesting that AMF is a widely expressed protein. Chordoid, chondroid, and muscular tumours revealed higher immunoreactivity in both benign and malignant tumours. Immunoblotting analysis corroborated the results of immunohistochemistry. Generally, malignant tumours revealed higher expression of AMF than benign tumours of the same histopathological lineage, except for dermatofibroma/dermatofibrosarcoma protuberans. However, mRNA levels were not concordant with protein levels, and sarcomas that displayed higher mRNA and lower protein expression levels showed a trend for distant metastasis. In cultured cells, AMF was secreted and detected in conditioned culture medium. Furthermore, when proteasome inhibitors were added to cells in order to examine the changes in turnover rates, these compounds did not significantly alter the intracellular levels of AMF protein. On the basis of these overall findings, it is suggested that a particular subset of sarcomas secrete AMF, rather than degrading this protein at a higher turnover rate. This secreted AMF presumably enhances their cell motility through an autocrine effect and eventually causes increased metastatic potential. Collectively, AMF was observed in a wide spectrum of lesions of mesenchymal tissue, supporting the notion that it is involved in various cellular functions, including proliferation, differentiation, metabolism, and metastasis. In addition, higher expression of its mRNA may indicate higher levels of protein secretion and define a particularly aggressive group of tumours with high metastatic potential.

Generation of inhibitory DNA aptamers against human hepatocyte growth factor

Hepatocyte growth factor (HGF), a multifunctional cytokine, can act on many cell types. It is involved in cancer growth and metastasis by enhancing the motility of cancer cells and stimulating angiogenesis. The development of effective inhibitors for HGF is an important issue in cancer therapy. In this study, we isolated DNA aptamers against human HGF using the systematic evolution of ligands by exponential enrichment method. The selected DNA aptamers had a highly conserved consensus sequence, and could be divided into two major classes (classes I and II). The consensus motif of classes I and II might contribute to the formation of a hairpin loop structure and a G-quartet structure, respectively. These DNA aptamers bound to human HGF with high affinity and specificity. The dissociation constants of typical aptamers H38-15 and H38-21, representative of the two classes, were calculated to be approximately 20 nM. H38-15 and H38-21 inhibited the biological activities of HGF including the stimulation of scattering, migration, and invasion of pancreatic cancer KP-3 cells. Furthermore, both aptamers inhibited HGF-induced tube formation by human umbilical vein endothelial cells. These results suggested that the isolated DNA aptamers will be useful as therapeutic and diagnostic reagents for cancers.

Giant cell tumors of the bone: Molecular profiling and expression analysis of Ephrin A1 receptor, Claudin 7, CD52, FGFR3 and AMFR

Giant cell tumors (GCTs) of the bone are osteolytic neoplasms with variable degrees of aggressiveness. The aim of this study was the molecular characterization of GCT tissue. We established gene expression profiles and discovered a number of genes that have not been described in GCTs before. RNA was prepared from 7 cryopreserved GCTs (primary tumors n = 5, relapses n = 2) and was hybridized to Affymetrix HG U133A microarrays. Paraffin-embedded samples were used for immunohistochemical validation (primary tumors n = 16, relapses n = 6). Gene ontology revealed that the majority of genes, found to be differentially expressed between primary and recurrent GCTs, were associated with receptor tyrosine kinase activity. We selected one upregulated gene (Claudin 7) and four downregulated genes (CD52, Ephrin A1 receptor, autocrine motility factor receptor [AMFR] and fibroblast growth factor receptor 3 [FGFR3] for further analysis using immunohistochemistry. Immunohistochemical analysis of CD52, AMFR, and Ephrin A1 receptor revealed expression profiles concordant with the microarray data, also with regard to differences between primary tumors and relapses.