Biomedical subjects

Y Chen

Publications and source records attributed to Y Chen.

At least 379 records · Page 21Linked to original sources

PubMed2001

Evidence of two distinct subsubtypes within the HIV-1 subtype A radiation.

Members of HIV-1 group M are responsible for the vast majority of AIDS cases worldwide and have been classified on the basis of their phylogenetic relationships into nine roughly equidistant clades, termed subtypes. Although there are no known phenotypic correlates for these genotypes, the disproportionate spread of certain of these lineages has been taken to indicate that subtype-specific biological differences may exist. The subtype nomenclature thus remains an important molecular epidemiological tool with which to track the course of the group M pandemic. In this study, we have characterized HIV-1 strains described previously as unusual subtype A variants on the basis of partial sequence analysis. Six such strains from Cyprus (CY), South Korea (KR), and the Democratic Republic of Congo (CD) were PCR amplified from infected cell culture or patient PBMC DNA, cloned, and sequences in their entirety (94CY017, 97KR004, 97CDKTB48, and 97CDKP58) or as half genomes (97CDKS10 and 97CDKFE4). Distance and phylogenetic analyses showed that four of these viruses (94CY017, 97CDKTB48, 97CDKFE4, and 97CDKS10) were closely related to each other, but quite divergent from all other HIV-1 strains, except for subtype A viruses, which represented their closest relatives. In phylogenetic trees from gag, pol, env, and nef regions, the four newly characterized HIV-1 strains formed a distinct sister clade to subtype A, which was as closely related to subtype A as subsubtypes F1 and F2 are to each other. According to current nomenclature rules, this defines a subsubtype, which we have tentatively termed A2. The two other viruses, 97KR004 and 97CDKP58, as well as a full-length HIV-1 sequence from the sequence database (ZAM184), were found to represent complex A2/D, A2/G, and A2/C recombinants, respectively. These results indicate that HIV-1 subtype A is composed of two subsubtypes (A1 and A2), both of which appear to have a widespread geographic distribution. The A2 viruses described here represent the first reference reagents for this new group M lineage.

Cyprus↗

PubMed2001

Determination of carbohydrates as their p-sulfophenylhydrazones by capillary zone electrophoresis.

p-Hydrazinobenzenesulfonic acid was explored as an ultraviolet labeling reagent for capillary electrophoresis of mono-, di- and trisaccharides. The labeling reaction that produces p-sulfophenylhydrazines took less than 8 min, and introduced both chromphore and charged groups into the carbohydrate molecules. The derivatives of nine mono- and disaccharides were completely separated in 9 min using a 100 mM borate buffer at pH 10.24. On-column UV detection at 200 nm allowed the detection of glucose with a mass detection limit of 17.6 fmol or a concentration limit of 3.6 microM. Reproducible quantification of carbohydrates was achieved in the concentration range of 0.1-9.1 mM in reaction solution. The method was applied successfully to determine the monosaccharide composition of laminaran.

Acetylglucosamine↗

PubMed2001

Cloning of differentially expressed genes in an HIV-1 resistant T cell clone by rapid subtraction hybridization, RaSH.

An HIV-1 resistant T cell clone R1c2 has been generated that carries mutant, latent HIV-1 in a minority of the cell population. Resistant cells express HIV-1 receptors CD4 and CXCR4 and display resistance to infection by wild type (wt) HIV-1 at the level of virus transcription. To begin to define the repertoire of genes modulated in R1c2 cells that correlate with and potentially control expression of the HIV-1 resistance phenotype we have employed a rapid subtraction hybridization (RaSH) technique. For this approach, cDNA libraries were prepared from double-stranded cDNAs that were enzymatically digested into small fragments, ligated to adapters, PCR amplified followed by incubation of tester and driver PCR fragments. The RaSH scheme resulted in the cloning of genes displaying differential expression between HIV-1 resistant (R1c2) and susceptible (SupT1) cells, including known genes and those not described in current DNA databases. Analysis of the pattern of expression of the differentially expressed genes documented eleven genes with enhanced (HR clones) and six genes with reduced (HS clones) expression in HIV-1 resistant versus HIV-1 susceptible T-cell clones.

Cell Line↗

PubMed2001

Release of hydrogen chloride from combustibles in municipal solid waste.

Study of the inorganic chlorides in municipal solid waste (MSW) shows that the main source of inorganic chlorides in MSW is food. The main organic source of HCl emission from MSW is plastic. But wood, textiles, and food also produce a large amount of HCl when they are combusted. Each combustible shows a different HCl releasing temperature range. At 973 K, there are 30-70% of the total chlorine left in the char of each combustibles in MSW.

Air Pollutants↗

PubMed2001

Defects of DNA mismatch repair in human prostate cancer.

Loss of mismatch repair (MMR) function leads to the accumulation of errors that normally occur during DNA replication, resulting in genetic instability. Germ-line mutations of MMR genes in the patients with hereditary nonpolyposis colorectal cancer lead to inactivation of MMR protein functions, and the defects of MMR are well correlated to the high rate of microsatellite instability in their tumors. Previous studies (T. Uchida, et al. Oncogene, 10: 1019-1022, 1995; S. Egawa, et al. Cancer RES:, 55: 2418-2421, 1995; J. M. Cunningham, et al. Cancer RES:, 56: 4475-4482, 1996; X. Gao, et al. Oncogene, 9: 2999-3003, 1994; H. Rohrbach, et al. Prostate, 40: 20-27, 1999) have shown that genetic instability (chromosomal and microsatellite instability) is detectable in human prostate cancer. To elucidate the role of MMR genes in the tumorigenesis of prostate cancer, we evaluated the expression of these genes in human cancer cell lines and in tumor specimens. Using Western blot analysis, we detected loss among MSH2, MLH1, PMS2, and PMS1 proteins in DU145, LNCaP, p69SV40T, M2182, and M12 cells. In addition, genomic instability in the prostate cell lines including DU145, PC3, LNCaP, p67SV40T, M2182, and M12 was detected by a microsatellite mutation assay. Significantly, immunohistochemical analysis of prostatic tissue revealed the reduction or absence of MMR protein expression in the epithelium of prostate tumor foci compared with normal adjacent prostate tissue. In contrast to hereditary nonpolyposis colorectal cancer, characterized by defects predominantly in MLH1 and MSH2, the samples we examined showed more tumor foci with loss of PMS1 and PMS2. PMS1, which is only expressed in the basal cells in normal glands, is conspicuously absent in most prostate cancer. From these results, we conclude that there are defects of MMR genes in human prostate cancer.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Fibroblast growth factor signaling and basement membrane assembly are connected during epithelial morphogenesis of the embryoid body.

Fibroblast growth factors and receptors are intimately connected to the extracellular matrix by their affinity to heparan sulfate proteoglycans. They mediate multiple processes during embryonic development and adult life. In this study, embryonic stem cell-derived embryoid bodies were used to model fibroblast growth factor signaling during early epithelial morphogenesis. To avoid redundancy caused by multiple receptors, we employed a dominant negative mutation of Fgfr2. Mutant-derived embryoid bodies failed to form endoderm, ectoderm, and basement membrane and did not cavitate. However, in mixed cultures they displayed complete differentiation induced by extracellular products of the normal cell. Evidence will be presented here that at least one of these products is the basement membrane or factors connected to it. It will be shown that in the mutant, collagen IV and laminin-1 synthesis is coordinately suppressed. We will demonstrate that the basement membrane is required for embryoid body differentiation by rescuing columnar ectoderm differentiation and cavitation in the mutant by externally added basement membrane proteins. This treatment induced transcription of Eomesodermin, an early developmental gene, suggesting that purified basement membrane proteins can activate inherent developmental programs. Our results provide a new paradigm for the role of fibroblast growth factor signaling in basement membrane formation and epithelial differentiation.

Animals↗

PubMed2001

[Mycophenolate mofetil in the treatment of primary nephrotic syndrome].

OBJECTIVE: To investigate the efficacy and safety of mycophenolate mofetil (MMF) on treating refractory primary nephrotic syndrome. METHODS: Forty-one patients with refractory nephrotic syndrome confirmed by renal biopsy, 19 with minor lesion (minimal lesion nephropathy and mesangial proliferative glomerulonephritis), 18 with membranous nephropathy (MN), 3 with focal segmental glomerulosclerosis (FSGS), and one with mesangioproliferative glomerulonephritis (MPGN), were treated by MMF combined with prednisone. The initial dosage of MMF was 1.0 - 2.0 g/d for three months and then the dosage was tapered gradually. The duration of MMF treatment was at least six months. Prednisone at the dose of 20 - 60 g/d was used at the beginning of the combined treatment and then the dosage was tapered gradually. Follow-up interview was conducted regularly. Four patients were rebiopsyed by the end of observation. RESULTS: The combined treatment of MMF/prednisone decreased the urine protein and elevated the serum albumin significantly among patients with minor lesion and MN (P < 0.001). All patients with minor lesion achieved clinical remission. Eleven of the nineteen cases responded within four weeks, and twelve of them obtained complete clinical remission. The dosage of prednisone could be tapered smoothly among the steroid dependent patients. Thirteen of the eighteen patients with MN achieved remission, however only six responded within four weeks and only three of them achieved complete clinical remission. During the treatment, four patients experienced transient increase of urine protein due to infection and recovered spontaneously without alteration of treatment. Side effects were tolerable except one case was withdrawn due to the decrease of hemoglobin. Renal function remained stable during the treatment. No obvious alteration could be found in renal biopsy by the end of treatment among four patients. CONCLUSION: MMF is an effective and safe immunosuppressive agent for refractory nephrotic syndrome.

Adolescent↗

PubMed2001

[Antigen presentation of eosinophils in mice].

OBJECTIVE: To explore whether or not eosinophils can present antigen to T lymphocytes in vivo, and to further elucidate the process and characteristics of antigen-presentation by eosinophils in vivo. METHODS: BALB/c mice were sensitized and challenged by ovalbumin to recruit eosinophil infiltration into the airways. The airway eosinophils were purified and were labeled with a fluorescent dye. The labeled eosinophils were instilled into the mouse tracheas, fluorescent microscope was used to observe the migration of endobronchial eosinophils in vivo. Single cell suspension was prepared from paratracheal lymph nodes of mice receiving antigen-exposed eosinophil instillation, and flow cytometry was used to determine proliferation response of T cells and to identify the subset of responding T cells. RESULTS: By 8 h after tracheal instillation, labeled eosinophils were visible in the subcapsular region and streaming through the subcapsular sinus (19.0 +/- 1.8/mm(2)). With increasing time, the numbers of eosinophils entering the regional lymph nodes increased, peaking at 24 h (59.2 +/- 7.2/mm(2)) and persisting for at least 120 h (29.6 +/- 2.8/mm(2)). In sensitized mice that received 5 x 10(5) antigen-exposed eosinophils, in vivo percentage of proliferating T cell in the paratracheal lymph nodes 1 d after eosinophil instillation (6.9% +/- 0.5%) were much higher than basic control value (3.2% +/- 0.3%, P < 0.01), peaked at day 3 (10.8% +/- 0.8%, P < 0.01), and then declined over 7 d (6.1% +/- 0.6%, P < 0.05). Eosinophil-induced in vivo T cell proliferation was antigen-specific, and the responding T cells were limited to CD4(+) cells. CONCLUSIONS: Eosinophils within the lumina of airways can process inhaled antigens, traffick to regional lymph nodes and function in vivo as antigen-presenting cells to stimulate responses of CD4(+) T cells.

Animals↗

PubMed2001

Antiviral activities of the soluble extracellular domains of type I interferon receptors.

Alternative splicing leads to the expression of multiple isoforms of the subunits (IFNAR1 and IFNAR2) of the type I IFN receptor. Here we describe two transcripts representing extracellular forms of ovine IFNAR1 and show that soluble extracellular forms of both IFNAR2 and IFNAR1, prepared in recombinant form in Escherichia coli, have antiviral (AV) activity in the absence of IFN. Exposure of Madin-Darby bovine kidney cells to the extracellular domain (R2E) of IFNAR2 at concentrations as low as 10 nM afforded complete protection against vesicular stomatitis virus and led to the rapid activation of the transcription factors ISGF3 and GAF. Although R2E can bind IFN (K(d) approximately 70 nM), activity was observed irrespective of whether or not ligand was present. R2E was inactive on mouse L929 cells but active on L929 cells expressing a membraneanchored, ovine/human chimeric IFNAR2 with an ovine extracellular domain. The data suggest that AV activity is conferred by the ability of soluble R2E to associate with the transfected IFNAR2 subunit rather than resident murine IFNAR1. Soluble extracellular forms of IFNAR1 have lower AV activity than R2E on Madin-Darby bovine kidney cells but are less species-specific and protect wild-type L929 cells as efficiently as the transfected cell line, presumably by interacting with one of the murine receptor subunits.

Animals↗

PubMed2001

Perchlorophenalenyl radical.

We report the preparation and solid-state characterization of the perchlorophenalenyl radical (1). The radical is initially obtained as a yellow-green solid by reduction of the perchlorophenalenium salt (12(+)). This solid sublimes in a sealed tube to give black shiny hexagonal crystals of the perchlorophenalenyl radical (1). The structure consists of 1-dimensional stacks of the monomeric radical. The peri-chlorine atoms force the phenalenyl system to be strongly nonplanar leading to a large separation between adjacent molecules within the stacks (3.78 A), and the molecules adopt two distinct stacking motifs (quasisuperimposed and rotated by 60 degrees with respect to neighbors). Because of the packing frustration in the lattice and the large intermolecular spacing, the solid shows Curie paramagnetism in the temperature range 100-400 K, before antiferromagnetic coupling sets in at low temperatures. Due to the narrow bandwidth that results from the isolation of the individual molecules, the solid is a Mott-Hubbard insulator, with a room-temperature conductivity of rho(RT) = 10(-10) S/cm.

Journal Article↗

PubMed2001

Comprehensive copy number and gene expression profiling of the 17q23 amplicon in human breast cancer.

The biological significance of DNA amplification in cancer is thought to be due to the selection of increased expression of a single or few important genes. However, systematic surveys of the copy number and expression of all genes within an amplified region of the genome have not been performed. Here we have used a combination of molecular, genomic, and microarray technologies to identify target genes for 17q23, a common region of amplification in breast cancers with poor prognosis. Construction of a 4-Mb genomic contig made it possible to define two common regions of amplification in breast cancer cell lines. Analysis of 184 primary breast tumors by fluorescence in situ hybridization on tissue microarrays validated these results with the highest amplification frequency (12.5%) observed for the distal region. Based on GeneMap'99 information, 17 known genes and 26 expressed sequence tags were localized to the contig. Analysis of genomic sequence identified 77 additional transcripts. A comprehensive analysis of expression levels of these transcripts in six breast cancer cell lines was carried out by using complementary DNA microarrays. The expression patterns varied from one cell line to another, and several overexpressed genes were identified. Of these, RPS6KB1, MUL, APPBP2, and TRAP240 as well as one uncharacterized expressed sequence tag were located in the two common amplified regions. In summary, comprehensive analysis of the 17q23 amplicon revealed a limited number of highly expressed genes that may contribute to the more aggressive clinical course observed in breast cancer patients with 17q23-amplified tumors.

Breast Neoplasms↗

PubMed2001

Evidence from the Pacific troposphere for large global sources of oxygenated organic compounds.

The presence of oxygenated organic compounds in the troposphere strongly influences key atmospheric processes. Such oxygenated species are, for example, carriers of reactive nitrogen and are easily photolysed, producing free radicals-and so influence the oxidizing capacity and the ozone-forming potential of the atmosphere-and may also contribute significantly to the organic component of aerosols. But knowledge of the distribution and sources of oxygenated organic compounds, especially in the Southern Hemisphere, is limited. Here we characterize the tropospheric composition of oxygenated organic species, using data from a recent airborne survey conducted over the tropical Pacific Ocean (30 degrees N to 30 degrees S). Measurements of a dozen oxygenated chemicals (carbonyls, alcohols, organic nitrates, organic pernitrates and peroxides), along with several C2-C8 hydrocarbons, reveal that abundances of oxygenated species are extremely high, and collectively, oxygenated species are nearly five times more abundant than non-methane hydrocarbons in the Southern Hemisphere. Current atmospheric models are unable to correctly simulate these findings, suggesting that large, diffuse, and hitherto-unknown sources of oxygenated organic compounds must therefore exist. Although the origin of these sources is still unclear, we suggest that oxygenated species could be formed via the oxidation of hydrocarbons in the atmosphere, the photochemical degradation of organic matter in the oceans, and direct emissions from terrestrial vegetation.

Journal Article↗

PubMed2001

Smads in human trophoblast cells: expression, regulation and role in TGF-beta-induced transcriptional activity.

Smad proteins have recently been shown to be downstream signaling molecules that transduce TGF-beta signals from cell surface to the nucleus. To determine the mechanisms of TGF-beta action in human trophoblast cells, we investigated the expression and regulation of Smad2,3,4, and 7 mRNAs in a normal trophoblast cell line, NPC, and a cell line derived from choriocarcinoma, JEG-3. Messenger RNAs for Smad2,3,4 and 7 were detected in both NPC and JEG-3 cells. TGF-beta1 induced modest increases in Smad2 and Smad4 mRNA levels without affecting Smad3 mRNA expression in both cell lines. Significant increases in Smad7 mRNA levels in both NPC and JEG-3 cells following TGF-beta1 treatment were observed. TGF-beta1 also induced promoter activity of the Smad7 gene, indicating a direct effect at the level of gene transcription. The transcriptional activity of TGF-beta was examined in JEG-3 cells using two TGF-beta responsive reporter constructs, p3TP-Lux and pAR3-Lux. We found that Smad3 and to a lesser extent, Smad2 and Smad4, enhanced, while Smad7 inhibited, TGF-beta1-induced transcriptional activities. The basal and TGF-beta1-induced transcription can be blocked by overexpression of a dominant negative TGF-beta type II receptor. Taken together, these findings demonstrate that in human trophoblast cell lines, the Smad pathway involved in TGF-beta signal transduction is functional and that TGF-beta plays an autocrine role in regulating gene expression.

DNA-Binding Proteins↗

PubMed2001

Cost-effectiveness analysis of long-term moderate exercise training in chronic heart failure.

The purpose of this study is to perform a cost-effectiveness analysis of long-term moderate exercise training (ET) in patients with stable chronic heart failure. In particular, the study focuses on the survival analysis and cost savings from the reduction in the hospitalization rate in the exercise group. In the past 10 years, ET has been shown to be beneficial for patients with stable class II and III heart failure in many randomized clinical trials. However, the cost-effectiveness of a long-term ET program has not been addressed for outcomes related to morbidity/mortality end points or health care utilization. We examined the cost-effectiveness of a 14-month long-term training in patients with stable chronic heart failure. The estimated increment cost for the training group, $3,227/patient, was calculated by subtracting the averted hospitalization cost, $1,336/patient, from the cost of ET and wage lost due to ET, estimated at $4,563/patient. For patients receiving ET, the estimated increment in life expectancy was 1.82 years/person in a time period of 15.5 years, compared with patients in the control group. The cost-effectiveness ratio for long-term ET in patients with stable heart failure was thus determined at $1,773/life-year saved, at a 3% discount rate. Long-term ET in patients with stable chronic heart failure is cost-effective and prolongs survival by an additional 1.82 years at a low cost of $1,773 per/life-year saved.

Cardiac Output, Low↗

PubMed2001

Design, synthesis, and structural analysis of influenza neuraminidase inhibitors containing pyrrolidine cores.

The discovery of (+/-)-(2S,3R,4R)-2-(trifluoroacetamido)methyl-3-amino-1-(N'-ethyl-N'-isopropylcarbamyl)pyrrolidine-4-carboxylic acid (A-192558, 20e) as a potent inhibitor of influenza neuraminidase (NA) is described. Efficient syntheses of two core structures, cis-3-(allyloxycarbonyl)amino-1-(9'-fluorenylmethoxycarbonyl)pyrrolidine-4-carboxylic acid (7) and tert-butyl (+/-)-(2S,3R,4R)-2-aminomethyl-3-bis(tert-butyloxycarbonyl)amino-1-(N'-ethyl-N'-isopropylcarbamyl)pyrrolidine-4-carboxylate (18b), were developed. Starting with these core structures and using available structural information of the NA active site as the guide, analogues were synthesized in both the tri- and tetrasubstituted pyrrolidine series by means of high-throughput parallel synthesis in solid or solution phase for expeditious SAR. These studies accelerated the identification of (+/-)-(2S,3R,4R)-2-(trifluoroacetamido)methyl-3-amino-1-(N-ethyl-N-isopropylcarbamyl)pyrrolidine-4-carboxylate (20e, A-192558) as the most potent NA inhibitor in this series (IC50 = 0.2 microM against NA A and 8 microM against NA B). The X-ray crystallographic structure of A-192558 bound to NA revealed the predicted interaction of the carboxylic group with the positively charged pocket (Arg118, Arg292, Arg371) and interaction of the trifluoroacetamino residue with the hydrophobic pocket (Ile222, Trp178) of the enzyme active site. Surprisingly, the ethyl and isopropyl groups of the urea functionality induced a conformational change of Glu276, turning the Glu276/Glu277 hydrophilic pocket, which normally accommodates the triglycerol side chain of substrate sialic acid, into an induced hydrophobic pocket.

Antiviral Agents↗

PubMed2001

[Cardiac troponin I: a marker for detecting non-ischemic cardiac injury].

OBJECTIVE: To investigate if cardiac troponin I (cTnI) could be used to monitor non-ischemic cardiac damage. METHODS: Two categories of patients without clinical evidence of acute myocardial infarction but suspected to have cardiac damage were included: acute heart failure (n = 37, heart function classified as class IV); and post burn injury (n = 30, TBSA 4% approximately 98%). Serum samples from these patients were analyzed for cTnI by chemiluminescent immunoassay. RESULTS: Elevated plasma cTnI was found in 89% of patients with acute heart failure (P < 0.001). Clinical conditions of the patients improved with declining of cTnI, while heart function deteriorated with the increasing of cTnI. Elevated plasma cTnI was also found between the 5(th) day to 14(th) day of post burn in 90% of burn patients. Mean cTnI level was significantly higher in patients with TBSA > 30% (P < 0.001) and in those patients with obvious burn wound exudation (P < 0.002). cTnI peaked when obvious burn wound exudation or eschar spontaneous separation. cTnI decreased after surgical excision. Two patients with persistent high cTnI developed tachycardia. CONCLUSION: cTnI is a sensitive marker for non-ischemic cardiac damage. Monitoring of cTnI is useful in differentiating the two categories of patients.

Biomarkers↗

PubMed2001

Reversal effects of nomegestrol acetate on multidrug resistance in adriamycin-resistant MCF7 breast cancer cell line.

BACKGROUND: Chemotherapy is important in the systematic treatment of breast cancer. To enhance the response of tumours to chemotherapy, attention has been focused on agents to reverse multidrug resistance (MDR) and on the sensitivity of tumour cells to chemical drugs. Hundreds of reversal drugs have been found in vitro, but their clinical application has been limited because of their toxicity. The reversal activity of progestogen compounds has been demonstrated. However, classical agents such as progesterone and megestrol (MG) also have high toxicity. Nomegestrol (NOM) belongs to a new derivation of progestogens and shows very low toxicity. We studied the reversal activity of NOM and compared it with that of verapamil (VRP), droloxifene (DRO), tamoxifen (TAM) and MG, and investigated the reversal mechanism, i.e. effects on the expression of the MDR1, glutathione S-transferase Pi (GSTpi), MDR-related protein (MRP) and topoisomerase IIalpha (TopoIIalpha) genes, as well as the intracellular drug concentration and the cell cycle. The aim of the study was to examine the reversal effects of NOM on MDR in MCF7/ADR, an MCF7 breast cancer cell line resistant to adriamycin (ADR), and its mechanism of action. METHODS: MCF7/ADR cells and MCF7/WT, an MCF7 breast cancer cell line sensitive to ADR, were treated with NOM as the acetate ester. With an assay based on a tetrazolium dye [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide; MTT], the effects of various concentrations of NOM on MDR in MCF7/ADR cells were studied. Before and after the treatment with 5 microM NOM, the expression of the MDR-related genes MDR1, GSTpi, TopoIIalpha and MRP were assayed with a reverse transcriptase polymerase chain reaction (RT-PCR) immunocytochemistry assay. By using flow cytometry (FCM), we observed the intracellular ADR concentration and the effects of combined treatment with NOM and ADR on the cell cycle. Results collected were analysed with Student's t test. RESULTS: NOM significantly reversed MDR in MCF7/ADR cells. After treatment NOM at 20, 10 and 5 microM, chemosensitivity to ADR increased 21-fold, 12-fold and 8-fold, respectively. The reversal activity of NOM was stronger than that of the precursor compound MG, and comparable to that of VRP. After treatment with 5 microM NOM, the expression of both the MDR1 and the GSTpi mRNA genes began to decline on the second day (P <0.05 and P <0.01, respectively), and reached the lowest level on the third day (both P <0.01); however, on the fifth day the expression levels began to increase again (both P <0.05). The expression of MRP and TopoIIalpha had no significant changes. Changes in the expression of P-glycoprotein (P-gp) and GSTpi were similar to those of their mRNA expressions, showing early declines and late increases. Two hours after treatment with 20, 10 and 5 microM NOM, the intracellular ADR concentration increased 2.7-fold, 2.3-fold and 1.5-fold respectively. However, NOM did not increase ADR accumulation in MCF7/WT cells. FCM data showed that after 48 h of combined administration of NOM (20 microM) and ADR (from low to high concentration), MCF7/ADR cells showed a gradual arrest at the G2M phase with increasing ADR dose. The arrest effect with combined drug treatment was stronger than that with the single ADR treatment. CONCLUSION: MDR is the major mechanism of drug resistance in malignant tumour cells. To overcome MDR and to increase chemosensitivity, many reversal agents have been found. Most progestogen compounds have been demonstrated to have reversal effects, but we found no data on NOM, a new progestogen compound. Our results show that NOM has strong reversal activity. The reversal effects were stronger than those of the precursor compound, MG, and were comparable to that of VRP. Because NOM has low toxicity, it might have good prospects in clinical application. Using RT-PCR and immunocytochemistry assays, we studied the effects of NOM on MDR-related genes. The results were that NOM could markedly downregulate the mRNA and protein expression levels of MDR1 and GSTpi. TopoIIalpha and MRP gene expression showed no significant changes. It is known that P-gp induces MDR in tumour cells mainly by decreasing the intracellular drug concentration. After treatment with NOM, the intracellular drug concentration in MCF7/ADR cells increased significantly. Combined treatment with NOM and ADR induced arrest at the G2M phase. It is worth noting that NOM caused an early decrease and a late increase in the expression of some MDR-related genes in a time-dependent manner. The phenomena raise a question for the continued administration of reversal agents in clinics that merits further study. We demonstrate that NOM has strong reversal effects on MDR in MCF7/ADR cells. The reversal is via different routes, namely downregulating the mRNA and protein expression levels of MDR1 and GSTpi, increasing intracellular drug concentration and arresting cells at the G2M phase (NOM in combination with ADR). The reversal mechanism needs further study.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

Effects of Motexafin gadolinium on tumor metabolism and radiation sensitivity.

PURPOSE: Experiments were undertaken to determine if metabolic changes induced by Motexafin gadolinium (Gd-Tex(+2), XCYTRIN) predict time intervals between drug and radiation wherein there is enhancement of radiation efficacy. METHODS AND MATERIALS: We evaluated the effect of Gd-Tex(+2) on tumor metabolism and on tumor growth using a mouse mammary carcinoma model and (31)P nuclear magnetic resonance (NMR) experiments. Response to therapy was evaluated based on time for the tumor to regrow to pretreatment size and also tumor doubling time. RESULTS: (31)P NMR experiments indicated that Gd-Tex(+2) effected tumor energy metabolism during the first 24 hours postadministration. A decrease in phosphocreatine was noted at 2 (p < 0.04), 6 (p < 0.006), and 24 (p < 0.001) hours post Gd-Tex(+2). A decrease in nucleoside triphosphates was noted only at 2 hours (p < 0.02), with subsequent recovery at 6 hours. Phosphocreatine in control (saline treated) tumors showed a significant decrease only at 24 hours (p < 0.01). Irradiation at 2 and 6 hours post Gd-Tex(+2) induced an enhanced effect compared to radiation alone as measured by analyzing the growth curves, maximum tumor volumes, and the time for the tumors to regrow to their initial volumes. Irradiation at 24 hours post Gd-Tex(+2) induced a modest enhancement in tumor growth delay compared to radiation alone. DISCUSSION: NMR spectroscopy may be useful for monitoring tumor metabolism after treatment with Gd-Tex(+2) and administering radiation during the time of maximal efficacy of Gd-Tex(+2).

Animals↗