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1.  Inhibition of transforming growth factor-β-activated kinase-1 blocks cancer cell adhesion, invasion, and metastasis 
British Journal of Cancer  2012;107(1):129-136.
Tumour cell metastasis involves cell adhesion and invasion, processes that depend on signal transduction, which can be influenced by the tumour microenvironment. N-6 polyunsaturated fatty acids, found both in the diet and in response to inflammatory responses, are important components of this microenvironment.
We used short hairpin RNA (shRNA) knockdown of TGF-β-activated kinase-1 (TAK1) in human tumour cells to examine its involvement in fatty acid-stimulated cell adhesion and invasion in vitro. An in vivo model of metastasis was developed in which cells, stably expressing firefly luciferase and either a control shRNA or a TAK1-specific shRNA, were injected into the mammary fat pads of mice fed diets, rich in n-6 polyunsaturated fatty acids. Tumour growth and spontaneous metastasis were monitored with in vivo and in situ imaging of bioluminescence.
Arachidonic acid activated TAK1 and downstream kinases in MDA-MB-435 breast cancer cells and led to increased adhesion and invasion. Knockdown of TAK1 blocked this activation and inhibited both cell adhesion and invasion in vitro. Tumour growth at the site of injection was not affected by TAK1 knockdown, but both the incidence and extent of metastasis to the lung were significantly reduced in mice injected with TAK1 knockdown cells compared with mice carrying control tumour cells.
These data demonstrate the importance of TAK1 signalling in tumour metastasis in vivo and suggest an opportunity for antimetastatic therapies.
PMCID: PMC3389413  PMID: 22644295
adhesion; invasion; metastasis; fatty acid; TGF-β-activated kinase-1; breast cancer
2.  PI3K/Akt signalling is required for the attachment and spreading, and growth in vivo of metastatic scirrhous gastric carcinoma 
British Journal of Cancer  2012;106(9):1535-1542.
PI3K/Akt (PKB) pathway has been shown in several cell types to be activated by ligands to cell surface integrins, leading to the metastasis of tumour cells. The signalling pathways involved in the metastatic spread of human scirrhous gastric carcinoma cells have not been defined.
The role of the PI3K/Akt pathway in an extensive peritoneal-seeding cell line, OCUM-2MD3 and a parental cell line, OCUM-2M, was investigated by assessing in vitro adhesion and spreading assay, and in vivo peritoneal metastatic model. We also examined the correlation of PI3K/Akt pathway with integrin signals by immunoprecipitations, using cells by transfection with mutant p85 (Δp85).
Adhesiveness and spreading of OCUM-2MD3 cells on collagen type IV was significantly decreased by PI3K inhibitors and expression of mutant p85, but not by inhibitors of protein kinase C (PKC) or extracellular signal-regulated kinase (ERK). Immunoprecipitation studies indicated that the PI3K/Akt pathway was associated with integrin signalling through Src and vinculin. In an in vivo experimental metastasis model, p85 inhibition reduced peritoneal metastasis of OCUM-2MD3 cells.
PI3K/Akt signalling may be required for integrin-dependent attachment and spreading of scirrhous gastric carcinoma cells, and would be translated into generating better strategies to optimise their use in cancer clinical trials.
PMCID: PMC3341864  PMID: 22531720
PI3 kinase; gastric carcinoma; adhesion; spreading: metastasis; integrin signalling
3.  Linoleic acid enhances angiogenesis through suppression of angiostatin induced by plasminogen activator inhibitor 1 
British Journal of Cancer  2011;105(11):1750-1758.
The intake of dietary fatty acids is highly correlated with the risk of various cancers. Linoleic acid (LA) is the most abundant polyunsaturated fat in the western diet, but the mechanism(s) by fatty acids such as LA modulate cancer cells is unclear. In this study, we examined the role of LA in various steps in gastric cancer progression.
The difference in gene expression between LA-treated and untreated OCUM-2MD3 gastric carcinoma cells was examined by mRNA differential display. The involvement of candidate genes was examined by oligo- and plasmid-mediated RNA interference. Biological functions of several of these genes were examined using in vitro assays for invasion, angiogenesis, apoptosis, cell viability, and matrix digestion. Angiogenesis in vivo was measured by CD-31 immunohistochemistry and microvessel density scoring.
LA enhanced the plasminogen activator inhibitor 1 (PAI-1) mRNA and protein expression, which are controlled by PAI-1 mRNA-binding protein. LA-stimulated invasion depended on PAI-1. LA also enhanced angiogenesis by suppression of angiostatin, also through PAI-1. LA did not alter cell growth in culture, but increased dietary LA-enhanced tumour growth in an animal model.
Our findings suggest that dietary LA impacts multiple steps in cancer invasion and angiogenesis, and that reducing LA in the diet may help slow cancer progression.
PMCID: PMC3242595  PMID: 22015554
gastric carcinoma; linoleic acid; plasminogen activator inhibitor 1; angiostatin; invasion
4.  Elevated dietary linoleic acid increases gastric carcinoma cell invasion and metastasis in mice 
British Journal of Cancer  2010;103(8):1182-1191.
Dietary (n-6)-polyunsaturated fatty acids influence cancer development, but the mechanisms have not been well characterised in gastric carcinoma.
We used two in vivo models to investigate the effects of these common dietary components on tumour metastasis. In a model of experimental metastasis, immunocompromised mice were fed diets containing linoleic acid (LA) at 2% (LLA), 8% (HLA) or 12% (VHLA) by weight and inoculated intraperitoneally (i.p.) with human gastric carcinoma cells (OCUM-2MD3). To model spontaneous metastasis, OCUM-2MD3 tumours were grafted onto the stomach walls of mice fed with the different diets. In in vitro assays, we investigated invasion and ERK phosphorylation of OCUM-2MD3 cells in the presence or absence of LA. Finally, we tested whether a cyclooxygenase (COX) inhibitor, indomethacin, could block peritoneal metastasis in vivo.
Both the HLA and VHLA groups showed increased incidence of tumour nodules (LA: 53% HLA: 89% VHLA: 100% P<0.03); the VHLA group also displayed increased numbers of tumour nodules and higher total volume relative to LLA group in experimental metastasis model. Both liver invasion (78%) and metastasis to the peritoneal cavity (67%) were more frequent in VHLA group compared with the LLA group (22% and 11%, respectively; P<0.03) in spontaneous metastasis model. We also found that the invasive ability of these cells is greatly enhanced when exposed to LA in vitro. Linoleic acid also increased invasion of other scirrhous gastric carcinoma cells, OCUM-12, NUGC3 and MKN-45. Linoleic acid effect on OCUM-2MD3 cells seems to be dependent on phosphorylation of ERK. The data suggest that invasion and phosphorylation of ERK were dependent on COX. Indomethacin decreased the number of tumours and total tumour volume in both LLA and VHLA groups. Finally, COX-1, which is known to be an important enzyme in the generation of bioactive metabolites from dietary fatty acids, appears to be responsible for the increased metastatic behaviour of OCUM-2MD3 cells in the mouse model.
Dietary LA stimulates invasion and peritoneal metastasis of gastric carcinoma cells through COX-catalysed metabolism and activation of ERK, steps that compose pathway potentially amenable to therapeutic intervention.
PMCID: PMC2967057  PMID: 20842125
gastric carcinoma; dietary fatty acid; cyclooxygenase; metastasis; invasion
6.  In vivo gene therapy for hyperlipidemia: phenotypic correction in Watanabe rabbits by hepatic delivery of the rabbit LDL receptor gene. 
Journal of Clinical Investigation  1995;95(2):768-773.
Elevations of plasma total or LDL cholesterol are major risk factors for cardiovascular disease. Efforts directed at preventing and treating cardiovascular disease have often focused on reducing the levels of these substances in the blood. The Watanabe Heritable Hyperlipidemic Rabbit, which has exceedingly high plasma cholesterol levels resulting from an LDL receptor deficiency, provides an excellent animal model for testing new treatments. A recombinant adenoviral vector containing the rabbit LDL receptor cDNA was administered to Watanabe rabbits. Plasma total cholesterol levels in the treated animals were reduced from 825.5 +/- 69.8 (mean +/- SD) to 247.3 +/- 61.5 mg/dl 6 d after infusion. These animals also demonstrated a 300-400% increase in plasma levels of HDL cholesterol and apo AI 10 d after treatment. As a result, the LDL:HDL ratio exhibited a dramatic decrease. Because only the rabbit LDL receptor gene was used for treatment, the results strongly suggest that the elevations of plasma HDL cholesterol and apo AI were secondary to a reduction in plasma total cholesterol in the treated animals. These results suggest an inverse relationship between plasma LDL and HDL cholesterol levels and imply that reduction of LDL cholesterol levels may have a beneficial effect on plasma HDL cholesterol.
PMCID: PMC295550  PMID: 7860759
7.  Efficiency factors and ATP/ADP ratios in nitrogen-fixing Bacillus polymyxa and Bacillus azotofixans. 
Journal of Bacteriology  1990;172(4):1962-1968.
The efficiency factor, the number of moles of ATP generated per mole of glucose fermented, was determined in anaerobic, non-carbon-limited N2-fixing cultures of Bacillus polymyxa, Bacillus macerans, Bacillus azotofixans, and Clostridium butyricum through identification and quantitation of the fermentation products by 13C nuclear magnetic resonance spectroscopy and measurement of acetate kinase activities. All three Bacillus species had acetate kinase activities and produced acetate and ethanol as the major fermentation products. The maximum amounts of ATP generated per mole of glucose fermented were 2.70, 2.64, and 2.88 mol in B. polymyxa, B. macerans, and B. azotofixans, respectively, compared with 3.25 mol in C. butyricum. Thus, in the N2-fixing Bacillus species, the efficiency factors are lower than that in C. butyricum. Steady-state ATP/ADP concentration ratios were measured in non-carbon-limited N2-fixing cultures of B. polymyxa and B. azotofixans through separation and quantitation of the adenylates in cell extracts by ion-pair reversed-phase high-performance liquid chromatography. The observed ATP/ADP ratios were 4.5 and 3.8, and estimated energy charges were 0.81 to 0.86 and 0.81 to 0.83, respectively, for B. polymyxa and B. azotofixans. The results suggest that under these growth conditions, the rate of ATP regeneration is adequate to meet the energy requirement for N2 fixation in the Bacillus species, in contrast to N2-fixing Clostridium pasteurianum and Klebsiella pneumoniae, for which substantially lower steady-state ATP/ADP ratios and energy charges have been reported. Implications of the results are discussed in relation to possible differences between Bacillus and Clostridium species in energy requirements for N2 fixation and concomitant ammonia assimilation.
PMCID: PMC208692  PMID: 2318806
8.  Ammonia assimilation pathways in nitrogen-fixing Clostridium kluyverii and Clostridium butyricum. 
Journal of Bacteriology  1989;171(4):2148-2154.
Pathways of ammonia assimilation into glutamic acid were investigated in ammonia-grown and N2-fixing Clostridium kluyverii and Clostridium butyricum by measuring the specific activities of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. C. kluyverii had NADPH-glutamate dehydrogenase with a Km of 12.0 mM for NH4+. The glutamate dehydrogenase pathway played an important role in ammonia assimilation in ammonia-grown cells but was found to play a minor role relative to that of the glutamine synthetase/NADPH-glutamate synthase pathway in nitrogen-fixing cells when the intracellular NH4+ concentration and the low affinity of the enzyme for NH4+ were taken into account. In C. butyricum grown on glucose-salt medium with ammonia or N2 as the nitrogen source, glutamate dehydrogenase activity was undetectable, and the glutamine synthetase/NADH-glutamate synthase pathway was the predominant pathway of ammonia assimilation. Under these growth conditions, C. butyricum also lacked the activity of glucose-6-phosphate dehydrogenase, which catalyzes the regeneration of NADPH from NADP+. However, high activities of glucose-6-phosphate dehydrogenase as well as of NADPH-glutamate dehydrogenase with a Km of 2.8 mM for NH4+ were present in C. butyricum after growth on complex nitrogen and carbon sources. The ammonia-assimilating pathway of N2-fixing C. butyricum, which differs from that of the previously studied Bacillus polymyxa and Bacillus macerans, is discussed in relation to possible effects of the availability of ATP and of NADPH on ammonia-assimilating pathways.
PMCID: PMC209870  PMID: 2564848
9.  Fidelity of two retroviral reverse transcriptases during DNA-dependent DNA synthesis in vitro. 
Molecular and Cellular Biology  1989;9(2):469-476.
We determined the fidelity of avian myeloblastosis virus and Moloney murine leukemia virus reverse transcriptases (RTs) during DNA synthesis in vitro using the M13mp2 lacZ alpha gene as a mutational target. Both RTs commit an error approximately once for every 30,000 nucleotides polymerized. DNA sequence analysis of mutants generated in a forward mutation assay capable of detecting many types of errors demonstrated that avian myeloblastosis virus RT produced a variety of different mutations. The majority (58%) were single-base substitutions; all of which resulted from the misincorporation of either dAMP or dGMP. Minus-one frameshifts were also common, composing about 30% of the mutations. In addition to single-base events, eight mutants contained sequence changes involving from 2 to 59 bases. The frequency of these mutants suggests that, at least during DNA synthesis in vitro, RTs also commit errors by mechanisms other than classical base miscoding and misalignment. We examined the ability of RTs to synthesize DNA from a mismatched primer terminus at a sequence where the mismatched base was complementary to the next base in the template. Unlike cellular DNA polymerases which polymerize from the mismatched template-primer, RTs preferred to polymerize from a rearranged template-primer containing a matched terminal base pair and an unpaired base in the template strand. The unusual preference for this substrate suggests that the interactions between RTs and the template-primer are different from those of cellular DNA polymerases. The overall error rate of RT in vitro is sufficient to account for the estimated mutation rate of these viruses.
PMCID: PMC362622  PMID: 2469002
10.  Role of glutamate dehydrogenase in ammonia assimilation in nitrogen-fixing Bacillus macerans. 
Journal of Bacteriology  1987;169(10):4692-4695.
Pathways of ammonia assimilation into glutamic acid in Bacillus macerans were investigated by measurements of the specific activities of glutamate dehydrogenase (GDH), glutamine synthetase, and glutamate synthase. In ammonia-rich medium, GDH was the predominant pathway of ammonia assimilation. In nitrogen-fixing cells in which the intracellular NH4+ concentration was 1.4 +/- 0.5 mM, the activity of GDH with a Km of 2.2 mM for NH4+ was found to be severalfold higher than that of glutamate synthase. The result suggests that GDH plays a significant role in the assimilation of NH4+ in N2-fixing B. macerans.
PMCID: PMC213841  PMID: 2888750
11.  The bacteriophage lambda O replication protein: isolation and characterization of the amplified initiator. 
Nucleic Acids Research  1983;11(21):7435-7452.
The bacteriophage lambda O protein participates in the initiation of lambda DNA replication. The lambda O gene was cloned into plasmid pKC30 such that its expression was controlled by the lambda PL promoter. A lambda prophage-coded thermosensitive cI repressor was used to regulate transcription of the cloned O gene. Thermal inactivation of the lambda cI repressor resulted in overproduction of the O protein until it constituted approximately 20% of the total cellular protein of Escherichia coli. A simple three-step purification protocol was developed that yields several milligrams of homogeneous O protein per gram of cell paste. The precise position of the O gene in the known lambda DNA sequence was identified from the amino-terminal sequence of the isolated O protein. Purified O protein stimulated the replication of plasmid lambda dv DNA in vitro and specifically bound to duplex DNA fragments carrying the lambda replication origin.
PMCID: PMC326494  PMID: 6316261
12.  Interaction of novel bis(platinum) complexes with DNA. 
Nucleic Acids Research  1989;17(23):9719-9733.
Bis(platinum) complexes [[cis-PtCl2(NH3)]2H2N(CH2)nNH2] are a novel series of potential anticancer agents in which two cis-diamine(platinum) groups are linked by an alkyldiamine of variable length. These complexes are potentially tetrafunctional, a unique feature in comparison with known anticancer agents. Studies of DNA interactions of bis(platinum) complexes in comparison with cisplatin demonstrate significant differences. Investigations of interstrand crosslink formation in which crosslinking of a short DNA fragment is detected by gel electrophoresis under denaturing conditions demonstrate that interstrand crosslinks are 250 fold more frequent among bis(platinum) adducts than among cisplatin-derived adducts under the conditions examined. These investigations indicate that bis(platinum) adducts contain a high frequency of structurally novel interstrand crosslinks formed through binding of the two platinum centers to opposite DNA strands. Unlike cisplatin, bis(platinum) complex binding does not unwind supercoiled DNA. Studies with the E. coli UvrABC nuclease complex demonstrate that both linear and supercoiled DNA containing bis(platinum) adducts are subject to incision by the repair enzyme complex. Initial studies using UvrABC nuclease as a probe to define the base and sequence specificity for bis(platinum) complex binding suggest that the specificity of the bis(platinum)s is similar, but not identical, to that of cisplatin.
PMCID: PMC335209  PMID: 2690006

Results 1-12 (12)