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1.
Bioprocess Biosyst Eng ; 44(6): 1147-1154, 2021 Jun.
Article in English | MEDLINE | ID: mdl-33559750

ABSTRACT

L-Ribose, a starting material for the synthesis of L-nucleoside, has attracted lots of attention since L-nucleoside is responsible for the antiviral activities of the racemic mixtures of nucleoside enantiomers. In this study, the L-ribulose-producing Candida tropicalis strain was engineered for the conversion of L-arabinose to L-ribose. For the construction of a uracil auxotroph, the URA3 gene was excised by homologous recombination. The expression cassette of codon-optimized L-ribose isomerase gene from Acinetobacter calcoaceticus DL-28 under the control of the GAPDH promoter was integrated to the uracil auxotroph. The resulting strain, K1 CoSTP2 LsaAraA AcLRI, was cultivated with the glucose/L-arabinose mixture. At 45.5 h of fermentation, 6.0 g/L of L-ribose and 3.2 g/L of L-ribulose were produced from 30 g/L of L-arabinose. The proportion between L-ribose and L-ribulose was approximately 2:1 and the conversion yield of L-arabinose to L-ribose was about 20% (w/w). The L-ribose-producing yeast strain was successfully constructed for the first time and could convert L-arabinose to L-ribose in one-pot fermentation using the mixture of glucose and L-arabinose.


Subject(s)
Arabinose , Candida tropicalis , Microorganisms, Genetically-Modified , Ribose , Arabinose/genetics , Arabinose/metabolism , Candida tropicalis/genetics , Candida tropicalis/metabolism , Microorganisms, Genetically-Modified/genetics , Microorganisms, Genetically-Modified/metabolism , Ribose/biosynthesis , Ribose/genetics
2.
Indian J Microbiol ; 59(1): 96-99, 2019 Mar.
Article in English | MEDLINE | ID: mdl-30728636

ABSTRACT

To improve the antimicrobial property of chitosan, water-soluble chitosan modified in their quaternary ammonium groups were synthesized. The antimicrobial properties were evaluated against Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Candida tropicalis. The activities increased with increasing cationic charges and the length of the alkyl chain as follows amino-chitosan, dimethylaminoethyl-chitosan, dimethylpropyl amino-chitosan, dimethylamino-1-propyl-chitosan, diethylaminoethyl (DEAE)-chitosan, and quaternized DEAE-chitosan. The modified cationic chitosans showed high antimicrobial property against B. subtilis-Gram-positive bacteria, but were less active towards yeast (C. tropicalis and S. cerevisiae) and E. coli-Gram-negative bacteria. The simple structure of the Gram-positive bacteria may explain why the cationic chitosan derivatives are more active towards B. subtilis than yeast and E. coli. The target sites of the chitosan derivatives are assumed to be the cytoplasmic membranes of microorganisms. The antimicrobial activities were strongly dependent on the cationic charge and the molecular weight. It can be suggested that these cationic chitosan derivatives have potential as antimicrobial agents.

3.
Sci Rep ; 8(1): 7273, 2018 05 08.
Article in English | MEDLINE | ID: mdl-29740059

ABSTRACT

Sialylation of recombinant therapeutic glycoproteins modulates their pharmacokinetic properties by affecting their in vivo half-life. N-glycan branching on glycoproteins increases the number of potential attachment sites for sialic acid. Here, we introduce a new approach for increasing the sialylation of recombinant human erythropoietin (rhEPO) produced in CHO cells by modulating poly-N-acetyllactosamine (poly-LacNAc) biosynthesis. We did not observe an increase in rhEPO sialylation, however, until the feedback inhibition by intracellular cytidine monophosphate-N-acetylneuraminic acid (CMP-Neu5Ac), which is a limiting factor for sialylation, was released. Thus, we found that a combined approach inhibiting poly-LacNAc biosynthesis and releasing CMP-Neu5Ac feedback inhibition produces the most significant increase in rhEPO sialylation in metabolically engineered CHO cells. Furthermore, a detailed analysis of the resulting N-glycan structures using LC/MS revealed increased tri- and tetra- sialylated N-glycan structures accompanied by a reduction of di-sialylated N-glycan structures. These results validate our new approach for glycosylation engineering, and we expect this approach will be useful in future efforts to enhance the efficacy of other therapeutic glycoproteins.


Subject(s)
Erythropoietin/genetics , Metabolic Engineering , Recombinant Proteins/chemistry , Sialic Acids/metabolism , Animals , CHO Cells , Chromatography, Liquid , Cricetinae , Cricetulus , Erythropoietin/chemistry , Erythropoietin/metabolism , Glycoproteins/chemistry , Glycoproteins/genetics , Glycosylation , Humans , Polysaccharides/chemistry , Recombinant Proteins/biosynthesis , Recombinant Proteins/genetics , Sialic Acids/chemistry , Tandem Mass Spectrometry
4.
J Biotechnol ; 274: 9-14, 2018 May 20.
Article in English | MEDLINE | ID: mdl-29407417

ABSTRACT

For the biological production of l-ribulose, conversion by enzymes or resting cells has been investigated. However, expensive or concentrated substrates, an additional purification step to remove borate and the requirement for cell cultivation and harvest steps before utilization of resting cells make the production process complex and unfavorable. Microbial fermentation may help overcome these limitations. In this study, we constructed a genetically engineered Candida tropicalis strain to produce l-ribulose by fermentation with a glucose/l-arabinose mixture. For the uptake of l-arabinose as a substrate and conversion of l-arabinose to l-ribulose, two heterologous genes coding for l-arabinose transporter and l-arabinose isomerase, were constitutively expressed in C. tropicalis under the GAPDH promoter. The Arabidopsis thaliana-originated l-arabinose transporter gene (STP2)-expressing strain exhibited a high l-arabinose uptake rate of 0.103 g/g cell/h and the expression of l-arabinose isomerase from Lactobacillus sakei 23 K showed 30% of conversion (9 g/L) from 30 g/L of l-arabinose. This genetically engineered strain can be used for l-ribulose production by fermentation using mixed sugars of glucose and l-arabinose.


Subject(s)
Arabinose/chemistry , Candida tropicalis/growth & development , Genetic Engineering/methods , Pentoses/metabolism , Aldose-Ketose Isomerases/genetics , Candida tropicalis/genetics , Candida tropicalis/metabolism , Fermentation , Glucose/chemistry , Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating)/genetics , Monosaccharide Transport Proteins/genetics , Promoter Regions, Genetic
5.
Anal Bioanal Chem ; 410(6): 1617-1629, 2018 Feb.
Article in English | MEDLINE | ID: mdl-29285644

ABSTRACT

Gastric cancer (GC) is one of the leading causes of cancer-related death worldwide, largely because of difficulties in early diagnosis. Despite accumulating evidence indicating that aberrant glycosylation is associated with GC, site-specific localization of the glycosylation to increase specificity and sensitivity for clinical use is still an analytical challenge. Here, we created an analytical platform with a targeted glycoproteomic approach for GC biomarker discovery. Unlike the conventional glycomic approach with untargeted mass spectrometric profiling of released glycan, our platform is characterized by three key features: it is a target-protein-specific, glycosylation-site-specific, and structure-specific platform with a one-shot enzyme reaction. Serum haptoglobin enriched by immunoaffinity chromatography was subjected to multispecific proteolysis to generate site-specific glycopeptides and to investigate the macroheterogeneity and microheterogeneity. Glycopeptides were identified and quantified by nano liquid chromatography-mass spectrometry and nano liquid chromatography-tandem mass spectrometry. Ninety-six glycopeptides, each corresponding to a unique glycan/glycosite pairing, were tracked across all cancer and control samples. Differences in abundance between the two groups were marked by particularly high magnitudes. Three glycopeptides exhibited exceptionally high control-to-cancer fold changes along with receiver operating characteristic curve areas of 1.0, indicating perfect discrimination between the two groups. From the results taken together, our platform, which provides biological information as well as high sensitivity and reproducibility, may be useful for GC biomarker discovery. Graphical abstract ᅟ.


Subject(s)
Glycopeptides/analysis , Haptoglobins/chemistry , Proteomics/methods , Stomach Neoplasms/diagnosis , Tandem Mass Spectrometry/methods , Biomarkers, Tumor/analysis , Biomarkers, Tumor/blood , Glycosylation , Humans , Models, Molecular , Proteolysis , Stomach Neoplasms/blood , Stomach Neoplasms/chemistry
6.
Sci Rep ; 7(1): 13059, 2017 10 12.
Article in English | MEDLINE | ID: mdl-29026192

ABSTRACT

Sialylation regulates the in vivo half-life of recombinant therapeutic glycoproteins, affecting their therapeutic efficacy. Levels of the precursor molecule cytidine monophospho-N-acetylneuraminic acid (CMP-Neu5Ac) are considered a limiting factor in the sialylation of glycoproteins. Here, we show that by reducing the amount of intracellular CMP-Neu5Ac consumed for glycosphingolipid (GSL) biosynthesis, we can increase the sialylation of recombinant human erythropoietin (rhEPO) produced in CHO cells. Initially, we found that treating CHO cells with a potent inhibitor of GSL biosynthesis increases the sialylation of the rhEPO they produce. Then, we established a stable CHO cell line that produces rhEPO in the context of repression of the key GSL biosynthetic enzyme UDP-glucose ceramide glucosyltransferase (UGCG). These UGCG-depleted cells show reduced levels of gangliosides and significantly elevated levels of rhEPO sialylation. Upon further analysis of the resulting N-glycosylation pattern, we discovered that the enhanced rhEPO sialylation could be attributed to a decrease in neutral and mono-sialylated N-glycans and an increase in di-sialylated N-glycans. Our results suggest that the therapeutic efficacy of rhEPO produced in CHO cells can be improved by shunting intracellular CMP-Neu5Ac away from GSL biosynthesis and toward glycoprotein sialylation.


Subject(s)
Erythropoietin/metabolism , Glycosphingolipids/biosynthesis , Recombinant Proteins/metabolism , Animals , CHO Cells , Cell Line , Cricetinae , Cricetulus , Erythropoietin/genetics , Monosaccharide Transport Proteins/metabolism , Propanolamines/pharmacology , Pyrrolidines/pharmacology , Recombinant Proteins/genetics
7.
Oncotarget ; 8(7): 11094-11104, 2017 Feb 14.
Article in English | MEDLINE | ID: mdl-28052004

ABSTRACT

Based on our previous studies, differential analysis of N-glycan expression bound on serum haptoglobin reveals the quantitative variation on gastric cancer patients. In this prospective case-control study, we explore the clinically relevant glycan markers for gastric cancer diagnosis. Serum samples were collected from patients with gastric cancer (n = 44) and healthy control (n = 44). N-glycans alteration was monitored by intact analysis of Hp using liquid chromatography-mass spectrometry followed by immunoaffinity purification with the serum samples. Intensity and frequency markers were defined depending on the mass spectrometry data analysis. Multiple markers were found with high diagnostic efficacy. As intensity markers (I-marker), six markers were discovered with the AUC > 0.8. The high efficiency markers exhibited AUC of 0.93 with a specificity of 86% when the sensitivity was set to 95%. We additionally established frequency marker (f-marker) panels based on the tendency of high N-glycan expression. The AUC to conclude patients and control group were 0.82 and 0.79, respectively. This study suggested that N-glycan variation of serum haptoglobin were associated with patients with gastric cancer and might be a promising marker for the cancer screening.


Subject(s)
Biomarkers, Tumor/metabolism , Haptoglobins/metabolism , Polysaccharides/metabolism , Stomach Neoplasms/metabolism , Adult , Aged , Biomarkers, Tumor/blood , Case-Control Studies , Chromatography, Liquid , Early Detection of Cancer/methods , Female , Glycosylation , Humans , Male , Mass Spectrometry , Middle Aged , Prospective Studies , Reproducibility of Results , Sensitivity and Specificity , Stomach Neoplasms/blood , Stomach Neoplasms/diagnosis
8.
Mol Biosyst ; 12(12): 3611-3621, 2016 11 15.
Article in English | MEDLINE | ID: mdl-27722599

ABSTRACT

Gastric cancer has one of the highest cancer mortality rates worldwide, largely because of difficulties in early-stage detection. Aberrant glycosylation in serum proteins is associated with many human diseases including inflammation and various types of cancer. Serum-based global glycan profiling using mass spectrometry has been explored and has already led to several potential glycan markers for several disease states. However, localization of the aberrant glycosylation is desirable in order to improve the specificity and sensitivity for clinical use. Here, we combined protein-specific immunoaffinity purification, glycan release, and MS analysis to examine haptoglobin glycosylation of gastric cancer patients for glyco-markers. Age- and sex-matched 60 serum samples (30 cancer patients and 30 healthy controls) were used to profile and quantify haptoglobin N-glycans. A T-test based statistical analysis was performed to identify potential glyco-markers for gastric cancer. Interestingly, abundances of several tri- and tetra-antennary fucosylated N-glycans were increased in gastric cancer patients. Additionally, structural analysis via LC/MS/MS indicated that the fucosylated complex type N-glycans were primarily decorated with antenna fucose, which can be categorized as sialyl-Lea or sialyl-Lex type structures. This platform demonstrates quantitative, structure-specific profiling of haptoglobin glycosylation for the purposes of biomarker discovery for gastric cancer.


Subject(s)
Glycomics , Haptoglobins , Stomach Neoplasms/blood , Biomarkers , Case-Control Studies , Chromatography, Liquid , Glycomics/methods , Glycosylation , Haptoglobins/isolation & purification , Humans , Metabolic Networks and Pathways , Polysaccharides/biosynthesis , Polysaccharides/blood , Stomach Neoplasms/pathology , Tandem Mass Spectrometry
10.
J Biotechnol ; 185: 28-36, 2014 Sep 20.
Article in English | MEDLINE | ID: mdl-24892811

ABSTRACT

The high molecular weight (>1 MDa) of hyaluronic acid (HA) is important for its biological functions. The reported limiting factors for the production of HA with high molecular weight (MW) by microbial fermentation are the insufficient HA precursor pool and cell growth inhibition. To overcome these issues, the Xenopus laevis xhasA2 and xhasB genes encoding hyaluronan synthase 2 (xhasA2) and UDP-glucose dehydrogenase (xhasB), were expressed in Pichia pastoris widely used for production of heterologous proteins. In this study, expression vectors containing various combination cassettes of HA pathway genes including xhasA2 and xhasB from X. laevis as well as UDP-glucose pyrophosphorylase (hasC), UDP-N-acetylglucosamine pyrophosphorylase (hasD) and phosphoglucose isomerase (hasE) from P. pastoris were constructed and tested. First, HA pathway genes were overexpressed using pAO815 and pGAPZB vectors, resulting in the production of 1.2 MDa HA polymers. Second, in order to decrease hyaluronan synthase expression a strong AOX1 promoter in the xhasA2 gene was replaced by a weak AOX2 promoter which increased the mean MW of HA to 2.1 MDa. Finally, the MW of HA polymer was further increased to 2.5 MDa by low-temperature cultivation (26 °C) which reduced cell growth inhibition. The yield of HA production by the P. pastoris recombinant strains in 1L of fermentation culture was 0.8-1.7 g/L.


Subject(s)
Biosynthetic Pathways/genetics , Glucuronosyltransferase/genetics , Hyaluronic Acid/biosynthesis , Hyaluronic Acid/chemistry , Metabolic Engineering/methods , Pichia/metabolism , Xenopus Proteins/genetics , Xenopus laevis/genetics , Animals , Base Sequence , DNA Primers/genetics , Escherichia coli , Genetic Vectors/genetics , Glucose 1-Dehydrogenase/genetics , Hyaluronan Synthases , Molecular Sequence Data , Molecular Weight , Pichia/genetics , Promoter Regions, Genetic/genetics , Real-Time Polymerase Chain Reaction , Sequence Analysis, DNA , Temperature
11.
J Microbiol Biotechnol ; 23(5): 699-706, 2013 May.
Article in English | MEDLINE | ID: mdl-23648861

ABSTRACT

We have previously reported that N-acetylcysteine (NAC) not only delayed apoptosis but also enhanced the production of recombinant erythropoietin (EPO) in Chinese hamster ovary (CHO) cell culture. To investigate the production enhancement mechanism, the effects of similar thiolreducing agents were studied. Intriguingly, all mild reducing agents examined including mercaptoethanesulfonic acid (MESNA), thiolactic acid (TLA), and thioglycolate (TG) were shown to block apoptosis and increase EPO production. A pulse-chase study of EPO secretion revealed that all four thiol-reducing agents increased the EPO secretion rate; among them TLA showed the highest rate. In terms of product quality, the sialic acid content of the glycoprotein is one of the most important factors. It was reported that a number of glycoproteins produced by CHO cells often have incomplete sialylation, particularly under high-producing conditions. Human alpha2,3-sialyltransferase (alpha2,3-ST) was introduced into EPO-producing CHO cells in order to compensate for the reduced sialylation during supplementation with NAC. When alpha2,3-ST was expressed in the presence of NAC, reduced sialylation was restored and an even more sialylated EPO was produced. Thus, our study is significant in that it offers increased EPO production while still allowing the prevention of decreased sialylation of EPO.


Subject(s)
Erythropoietin/metabolism , Gene Expression , Reducing Agents/metabolism , Sialyltransferases/genetics , Sialyltransferases/metabolism , Animals , CHO Cells , Cricetinae , Cricetulus , Erythropoietin/genetics , Glycolates/metabolism , Humans , Protein Transport , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Secretory Pathway , Sulfhydryl Compounds/metabolism
12.
Bioprocess Biosyst Eng ; 36(6): 809-17, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23411871

ABSTRACT

Xylose utilization is inhibited by glucose uptake in xylose-assimilating yeasts, including Candida tropicalis, resulting in limitation of xylose uptake during the fermentation of glucose/xylose mixtures. In this study, a heterologous xylose transporter gene (At5g17010) from Arabidopsis thaliana was selected because of its high affinity for xylose and was codon-optimized for functional expression in C. tropicalis. The codon-optimized gene was placed under the control of the GAPDH promoter and was integrated into the genome of C. tropicalis strain LXU1 which is xyl2-disrupted and NXRG (codon-optimized Neurospora crassa xylose reductase) introduced. The xylose uptake rate was increased by 37-73 % in the transporter expression-enhanced strains depending on the glucose/xylose mixture ratio. The recombinant strain LXT2 in 500-mL flask culture using glucose/xylose mixtures showed a xylose uptake rate that was 29 % higher and a xylitol volumetric productivity (1.14 g/L/h) that was 25 % higher than the corresponding rates for control strain LXU1. Membrane protein extraction and Western blot analysis confirmed the successful heterologous expression and membrane localization of the xylose transporter in C. tropicalis.


Subject(s)
Arabidopsis Proteins/biosynthesis , Arabidopsis/enzymology , Candida tropicalis/enzymology , Monosaccharide Transport Proteins/biosynthesis , Xylitol/biosynthesis , Xylose/metabolism , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Candida tropicalis/genetics , Monosaccharide Transport Proteins/genetics , Recombinant Proteins/biosynthesis , Recombinant Proteins/chemistry , Xylitol/genetics
13.
Bioprocess Biosyst Eng ; 36(9): 1279-84, 2013 Sep.
Article in English | MEDLINE | ID: mdl-23232964

ABSTRACT

Glycerol can be used as a primary carbon source by yeasts, little is known regarding glycerol metabolism in Candida tropicalis. In this study, glycerol kinase gene (gk) was disrupted from xylitol dehydrogenase gene (XYL2) knockout C. tropicalis strain BSXDH-3. The resultant gk knockout C. tropicalis strain was incapable to grow on glycerol. The cells growth on glycerol was resumed by co-expressing Scheffersomyces stipitis gcy1, 2 and 3 genes, which respectively encode NADP(+)-dependent glycerol dehydrogenase 1, 2 and 3, under the control of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter. NADPH-dependent xylitol production was higher in the engineered strain, termed "GK", than in BSXDH-3. In fermentation experiments using glycerol as co-substrate with xylose, strain GK produced xylitol 0.85 and 1.28 g l(-1) h(-1) at the time periods of 16 and 24 h, respectively, which is 30 and 18 % higher at same time intervals in BSXDH-3. This is the first report of gk gene disruption and co-expression of gcy1, 2 and 3 genes for NADPH regeneration and enhanced xylitol production in C. tropicalis.


Subject(s)
Candida tropicalis , Fungal Proteins , Gene Deletion , Gene Expression , Glycerol Kinase , Saccharomycetales , Sugar Alcohol Dehydrogenases , Xylitol/biosynthesis , Candida tropicalis/enzymology , Candida tropicalis/genetics , Candida tropicalis/growth & development , Fungal Proteins/genetics , Fungal Proteins/metabolism , Saccharomycetales/enzymology , Saccharomycetales/genetics , Sugar Alcohol Dehydrogenases/biosynthesis , Sugar Alcohol Dehydrogenases/genetics
14.
J Palliat Care ; 28(1): 5-12, 2012.
Article in English | MEDLINE | ID: mdl-22582466

ABSTRACT

This study identified factors associated with higher medical costs for patients with terminal cancer in hospice units in order to develop a daily payment system for hospice services within Korea's National Health Insurance (NHI) program. Through chart reviews conducted by staff nurses, medical information and costs were obtained for 274 patients with terminal cancer in 20 hospice units in October 2007. The daily medical cost per patient was calculated based on the fee-for-service scheme. The characteristics of the hospice units were examined by means of a semistructured questionnaire administered to hospice unit coordinators. Higher daily costs were associated with general hospital-based hospice units (as compared with free-standing units: p<0.01), low Palliative Performance Scale scores (PPS<50, p<0.05), and the presence of fever (p<0.01). In multivariate analysis, hospice unit type was found to be the factor most strongly associated with medical cost. A hospice payment system based on patient characteristics should be thoroughly considered.


Subject(s)
Health Care Costs , Hospices/economics , Neoplasms/economics , Aged , Cost Control , Female , Health Planning , Humans , Linear Models , Male , Middle Aged , Multivariate Analysis , Neoplasms/therapy , Republic of Korea , Retrospective Studies
15.
Cancer ; 118(22): 5688-97, 2012 Nov 15.
Article in English | MEDLINE | ID: mdl-22570083

ABSTRACT

BACKGROUND: The assessment of pain management outcomes is important for the quality assurance of palliative care. The objective of this study was to determine whether there are significant variations in pain management outcomes among palliative care centers and whether they are affected by organizational factors. METHODS: Data used in this investigation were from the 2009 Korean Terminal Cancer Patient Information System and administrative records of the 34 inpatient palliative care centers designated by the Korean Ministry of Health and Welfare in 2009. Self-reported pain scores (range, from 0 to 10) at admission and 1 week after admission were prospectively collected. Multilevel mixed-effect regression models were used to analyze the variations and the impact of organizational-level factors on 2 pain management outcomes (ie, reduction in average pain score and achievement of adequate pain control at 1 week after admission). RESULTS: In total, 1711 patients with terminal cancer were included in the analyses. The mean reduction in the pain score was 0.69 to 1.91 after 1 week, and most patients (82.8%) achieved adequate pain control. There were significant variations in pain management outcomes among palliative care centers. Higher composite scores for human resources adequacy were associated significantly with a greater reduction in pain score (ß, 0.11; 95% confidence interval, 0.01-0.21), and achievement of adequate pain control (adjusted odds ratio, 1.26; 95% confidence interval, 1.10-1.45). CONCLUSIONS: There were significant variations in pain management outcomes among inpatient palliative care centers, and they were affected by organizational factors, such as human resources adequacy.


Subject(s)
Pain Management/methods , Pain Measurement , Palliative Care/methods , Hospitalization , Humans , Neoplasms/complications , Pain/complications , Treatment Outcome
16.
Biochim Biophys Acta ; 1820(7): 1141-8, 2012 Jul.
Article in English | MEDLINE | ID: mdl-22542783

ABSTRACT

BACKGROUND: Globoside (Gb4), a globo-series glycosphingolipid (GSL), has been characterized as a stage-specific embryonic antigen (SSEA), and is highly expressed during embryogenesis as well as in cancer tissues. However, the functional role and molecular mechanism of Gb4 are so far unknown. METHODS: GSLs were preferentially inhibited by treatment with D-threo-1-ethylenedioxyphenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (EtDO-P4), a nanomolar inhibitor of GSL synthesis, in two carcinoma cell lines, HCT116 and MCF7. The effect of EtDO-P4 was examined by MTT assay, FACS, wound assay, western blotting, and RTK array analysis. The functional role of Gb4 was determined by the exogenous addition of various GSLs, and an assay utilizing GSL-coated latex beads. RESULTS: Both cell lines contained higher levels of neutral GSLs than of sialic acid-containing GSLs. Gb4 was one of the major neutral GSLs. The depletion of total GSLs caused significant reduction of cell proliferation, but had less effect on cell apoptosis or motility. EtDO-P4 treatment also suppressed activation of the epidermal growth factor receptor (EGFR)-induced ERK pathway and various receptor tyrosine kinases (RTKs). The reduced activation of ERK was restored by the exogenous addition of Gb4, but not by the addition of gangliosides (GM1, GM2, GM3, and GD1a). The GSL-coated bead assay indicated that Gb4 forms a complex with EGFR, but not with other RTKs. Taken together, Gb4 promotes activation of EGFR-induced ERK signaling through direct interaction with EGFR. GENERAL SIGNIFICANCE: A globo-series GSL, Gb4, promotes EGFR-induced MAPK signaling, resulting in cancer cell proliferation. These findings suggest a possible application of Gb4 in cancer diagnostics and drug targeting.


Subject(s)
Breast Neoplasms/metabolism , Colonic Neoplasms/metabolism , ErbB Receptors/metabolism , Globosides/pharmacology , Mitogen-Activated Protein Kinase 3/metabolism , Signal Transduction/drug effects , Apoptosis/drug effects , Blotting, Western , Breast Neoplasms/drug therapy , Breast Neoplasms/pathology , Cell Communication/drug effects , Cell Movement/drug effects , Cell Proliferation/drug effects , Chromatography, Thin Layer , Colonic Neoplasms/drug therapy , Colonic Neoplasms/pathology , Glycosphingolipids/pharmacology , Humans , Phosphorylation , Tumor Cells, Cultured
17.
Bioprocess Biosyst Eng ; 35(1-2): 199-204, 2012 Jan.
Article in English | MEDLINE | ID: mdl-21969058

ABSTRACT

The yeast Candida tropicalis produces xylitol, a natural, low-calorie sweetener whose metabolism does not require insulin, by catalytic activity of NADPH-dependent xylose reductase. The oxidative pentose phosphate pathway (PPP) is a major basis for NADPH biosynthesis in C. tropicalis. In order to increase xylitol production rate, xylitol dehydrogenase gene (XYL2)disrupted C. tropicalis strain BSXDH-3 was engineered to co-express zwf and gnd genes which, respectively encodes glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), under the control of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter. NADPH-dependent xylitol production was higher in the engineered strain, termed "PP", than in BSXDH-3. In fermentation experiments using glycerol as a co-substrate with xylose, strain PP showed volumetric xylitol productivity of 1.25 g l(-1) h(-1), 21% higher than the rate (1.04 g l(-1) h(-1)) in BSXDH-3. This is the first report of increased metabolic flux toward PPP in C. tropicalis for NADPH regeneration and enhanced xylitol production.


Subject(s)
Candida tropicalis/enzymology , Candida tropicalis/genetics , Genetic Enhancement/methods , Glucosephosphate Dehydrogenase/metabolism , Glycerol/metabolism , Phosphogluconate Dehydrogenase/metabolism , Xylitol/biosynthesis , Glucosephosphate Dehydrogenase/genetics , Phosphogluconate Dehydrogenase/genetics , Xylitol/isolation & purification
18.
Bioprocess Biosyst Eng ; 35(1-2): 191-8, 2012 Jan.
Article in English | MEDLINE | ID: mdl-21922311

ABSTRACT

Xylose reductase (XR) is the first enzyme in D: -xylose metabolism, catalyzing the reduction of D: -xylose to xylitol. Formation of XR in the yeast Candida tropicalis is significantly repressed in cells grown on medium that contains glucose as carbon and energy source, because of the repressive effect of glucose. This is one reason why glucose is not a suitable co-substrate for cell growth in industrial xylitol production. XR from the ascomycete Neurospora crassa (NcXR) has high catalytic efficiency; however, NcXR is not expressed in C. tropicalis because of difference in codon usage between the two species. In this study, NcXR codons were changed to those preferred in C. tropicalis. This codon-optimized NcXR gene (termed NXRG) was placed under control of a constitutive glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter derived from C. tropicalis, and integrated into the genome of xylitol dehydrogenase gene (XYL2)-disrupted C. tropicalis. High expression level of NXRG was confirmed by determining XR activity in cells grown on glucose medium. The resulting recombinant strain, LNG2, showed high XR activity (2.86 U (mg of protein)(-1)), whereas parent strain BSXDH-3 showed no activity. In xylitol fermentation using glucose as a co-substrate with xylose, LNG2 showed xylitol production rate 1.44 g L(-1) h(-1) and xylitol yield of 96% at 44 h, which were 73 and 62%, respectively, higher than corresponding values for BSXDH-3 (rate 0.83 g L(-1) h(-1); yield 59%).


Subject(s)
Aldehyde Reductase/metabolism , Candida tropicalis/enzymology , Codon/genetics , Genetic Enhancement/methods , Neurospora crassa/metabolism , Xylitol/biosynthesis , Xylose/metabolism , Aldehyde Reductase/genetics , Candida tropicalis/genetics , Neurospora crassa/genetics , Transfection , Xylitol/isolation & purification
19.
Support Care Cancer ; 20(3): 539-47, 2012 Mar.
Article in English | MEDLINE | ID: mdl-21347522

ABSTRACT

PURPOSES: Hospice programs in Korea have been largely based on volunteer activity, religious services, or social services. Recent government policy of designating medically based inpatient palliative care services and per diem payment system made it necessary to monitor the quality of these services. We examined the variation in the process and outcomes of palliative care services, using 2009 data obtained from the Korean Terminal Cancer Patient Information System. METHODS: Data were collected from 3,867 patients with terminal cancer who were registered in 34 inpatient palliative care centers designated by the Ministry of Health and Welfare. We used the mean length of stay and the subsequent place of care as process indicators, and change in average pain score as an outcome indicator. The data were analyzed using descriptive statistics, and analysis of covariance for the case-mix adjustment. RESULTS: There were considerable variations among services with regards to the mean length of stay (i.e., 10.5 to 32.6 days for each admission) and subsequent place of care (i.e., 39.8% to 92.6% ended in death at the first admission), even after stratification by service level. The mean change in average pain score varied from -1.48 to 2.16, and remained significant after case-mix adjustment. CONCLUSION: We found considerable variations among palliative care services with regard to the mean length of stay, subsequent place of care, and change in average pain score. Continued assessment of the variations in process and outcomes will assist in developing the national benchmarking system and the evaluation of the government policy.


Subject(s)
Hospitalization/statistics & numerical data , Neoplasms/therapy , Outcome and Process Assessment, Health Care/methods , Palliative Care/methods , Palliative Care/statistics & numerical data , Adolescent , Adult , Aged , Aged, 80 and over , Comorbidity , Female , Home Care Services/statistics & numerical data , Humans , Inpatients/statistics & numerical data , Korea , Length of Stay , Male , Middle Aged , Neoplasms/classification , Neoplasms/mortality , Pain/epidemiology , Pain Measurement , Palliative Care/standards , Patient Education as Topic , Quality Improvement/organization & administration , Republic of Korea , Survival Rate , Terminal Care/methods , Terminal Care/statistics & numerical data , Young Adult
20.
J Pain Symptom Manage ; 42(2): 251-64, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21458215

ABSTRACT

CONTEXT: There is an increasing need for the comparative assessment of palliative care services; however, few systematic empirical studies have been performed to determine the most feasible, representative, efficient survey method. OBJECTIVES: To investigate the feasibility, representativeness, and efficiency of several survey methods. METHODS: This study was performed as a part of a national initiative to develop a system to evaluate the quality of palliative care services. Three separate but related surveys of patients, caregivers, and bereaved family members were conducted. These surveys were designed to simulate an independent assessment in a nationwide quality evaluation project. RESULTS: The effective response rates for the patient, caregiver, and bereavement surveys were 30.4% (105 of 344), 46.5% (160 of 344), and 20.9% (501 of 2398), respectively. Subjects who responded to the patient and caregiver surveys were likely to have better physical and mental conditions, whereas subjects who responded to the bereaved family survey did not differ significantly from nonrespondents in regard to patient characteristics, except for a small difference in patient gender (females: 47.2% vs. 41.7%, P=0.028). The average number of responses per institution was 3.2, 4.8, and 15.2, respectively. The cost of the patient and caregiver surveys was much higher than the cost of the bereaved family member survey. CONCLUSION: There were significant differences between the three methods. Despite the low response rate, our findings suggest that the bereaved family member survey has strengths in terms of feasibility and efficiency, and could be considered as a practical option for the comparative assessment of palliative care services by an independent body.


Subject(s)
Health Care Surveys/methods , Palliative Care/standards , Quality Assurance, Health Care/methods , Adult , Aged , Aged, 80 and over , Caregivers , Cholestasis , Female , Health Services Needs and Demand , Humans , Male , Middle Aged , Pneumonia , Republic of Korea
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