Biomedical subjects
Publications and source records attributed to Ming Guan.
Human pigment epithelium-derived factor (PEDF), a neurotrophic factor, is the most potent natural inhibitor of angiogenesis. To produce the active PEDF, the gene coding for the human PEDF protein was expressed in E. coli. The rPEDF protein was expressed at 457 mg l-1 as a soluble protein. The yield of purified GST fusion protein was 14 mg l-1. Purified rPEDF inhibited tube formation in endothelial cells.
OBJECTIVE: Cisplatin (DDP) resistance is a major barrier to overcome before chemotherapy can become curative for most patients presenting with ovarian cancer. In this study, we investigated the effect of siRNAs on expression of p-gp, GST-pi mRNA and protein in cisplatin-resistant human ovarian cancer cells in order to restore sensitivity to DDP. METHODS: Small interfering double-stranded RNAs (siRNA) were designed to target p-glycoprotein (p-gp) and glutathione S-transferases (GST) mRNA as a strategy to inhibit both resistant gene expression at the mRNA level. Using Real-Time PCR and western blotting assay the changes of the RNA and protein levels of both drug resistant genes were studied. RESULTS: Transfection of MDR-1 and GST siRNAs into human multi-drug resistance (MDR) ovarian cancer cell lines, COC1/DDP and SKOV3/DDP, resulted in a time-dependent inhibition of both gene expressions with the decline of the IC(50) values but had no effect on the expression of a-Tubulin. Inhibition of P-gp and GST expression by siRNA enhanced the intracellular accumulation of and restored sensitivity to DDP. CONCLUSIONS: These studies suggest that p-gp and GST siRNAs are effective inhibitors of MDR gene expression and reverse the resistance of ovarian carcinomas. Our studies may provide a new insight to develop siRNAs as a novel therapeutic tool for the treatment of ovarian carcinomas.
An immunochromatographic test for rapid detection of IgM antibodies in patients with acute hepatitis E infection was developed utilizing the well-characterized recombinant protein EP2.1 and monoclonal antibody 4B2. The new rapid test based on a novel reverse-flow technology was able to generate a positive result within 2 to 3 min. Our study showed that this test was able to detect anti-HEV IgM antibodies in 96.7% of the patient samples tested (n = 151) while maintaining an excellent specificity of 98.6% with samples from various patient or healthy control groups (total n = 208). Furthermore, this rapid test gave a good specificity of 90.9% when tested with rheumatoid factor (RF)-positive sera (RF value of < or =850 IU/ml; n = 11) although a higher concentration of RF in samples might cause cross-reactivity. The new test has a good agreement of 97.2% with a kappa value of 0.943 when compared with a reference enzyme-linked immunosorbent assay. The positive predictive value and the negative predictive value for the rapid test thus reached 98.0 and 97.6%, respectively. This is the first rapid, point-of-care test for hepatitis E and will be especially useful for the diagnosis of acute hepatitis E virus infection in field and emergency settings and in resource-poor countries.
A rapid and reliable diagnostic assay for acute hepatitis E virus (HEV) infection is needed. We evaluated a rapid, immunochromatographic assay for IgM antibodies to HEV (ASSURE HEV IgM Rapid Test) using acute-phase HEV samples (n = 200) from Indonesia and Nepal and convalescent-phase HEV samples (n = 70) from Nepal. Blood donors in Thailand (n = 100), individuals with hepatitis A (n = 80), hepatitis B (n = 45), and hepatitis C (n = 50) in Thailand and Nepal, acute-phase sera of individuals with Epstein-Barr virus infection (n = 20), and rheumatoid factor-positive blood (n = 26) served as negative controls. The assay had a sensitivity of 93% (95% confidence interval [CI] = 88.5-96.1%) and a specificity of 99.7% (95% CI = 98.3-100%). The positive and negative predictive values were 99.5% (95% CI = 97.1-100%) and 95.8% (95% CI = 93.1-97.7%), respectively. These results suggest that this assay is a sensitive and specific tool for the rapid diagnosis of acute HEV infection.
OBJECTIVE: To evaluate the effect of a novel blockade technique for gastric cancer on blood-borne metastasis of gastric cancer cells to portal vein. METHODS: Twenty-three cases of gastric cancer were divided into routine operation group (8 cases intraoperatively without blockade technique) and blockade group (15 cases with blockade technique). Blood samples from portal vein pre- and intraoperatively, as well as gastroepiploic vein limited within the blockade area were obtained to detect CK19 mRNA expression by using RT-PCR technique. RESULTS: Before the dissection of gastric lesion, the overall positive rate of CK19 mRNA expression in portal vein blood is 34.7% (9/23), including 37.5% (3/8) in routine operation group and 33.3% (5/15) in blockade group. While the course of tumor resection, those positive rates were 87.5% (7/8) in routine operation group and 6.7% (1/15) in blockade group respectively (P < 0.05). CK19 mRNA expression in the right gastroepiploic venous blood limited within the blocking area was all positive in 15 cases of blockade group. CONCLUSION: This blockade technique can be used effectively to block the intraoperative spread of gastric cancer cells, thus prevent blood-borne metastasis due to operative manipulation.
OBJECTIVE: To determine whether SELDI protein profiling of urine coupled with a tree analysis pattern could differentiate TCC from noncancer patients. METHODS: The ProteinChip Arrays were performed on a ProteinChip PBS II reader of the ProteinChip Biomarker System. The study was divided into two phases: a preliminary phase with construction of tree analysis pattern, and a testing phase with test urine samples. Generation of the tree analysis pattern was performed by a training data set consisting of 104 samples. The validity of the tree analysis pattern was then challenged with a test set of 68 samples. RESULTS: Average of 187 mass peaks was detected in the urine samples, and five of these peaks were used to construct the tree analysis pattern. The classification pattern correctly predicted 91.67-94.64% of the samples for both of the two groups in the training set, for an overall correct classification of about 93%. The pattern correctly predicted 72.0% (49 of 68) of the test samples, with 71.4% (25 of 35) of the TCC samples, 72.7% (24 of 33) of the noncancer samples. CONCLUSIONS: The high sensitivity and specificity obtained by the urine protein profiling approach demonstrate that SELDI-TOF-MS combined with a tree analysis pattern can both facilitate discriminate TCC bladder cancer with noncancer and provide an innovative clinical diagnostic platform improve the detection of TCC bladder cancer patients.
OBJECTIVE: To screen relatively specifical markers in urines from renal cell carcinoma patients using surface-enhanced laser desorption and ionization time of flight mass spectrometry (SELDI-TOF-MS) ProteinChip technology. METHODS: Urine samples from 40 renal cell carcinoma (RCC) patients, 40 healthy volunteers and 40 patients with other urogenital diseases were analyzed using IMAC-Cu-3 PoteinChip, which can specifically bind the metal-combining-proteins. Proteomic spectra were generated by mass spectrometry. RESULTS: Four differentially expressed potentially biomarkers were identified with the relative molecular weights of 4020, 4637, 5070, and 5500. The sensitivity for diagnosing RCC was 57.5%, 66.7%, 63.7%, 65%, and specificity was 86.2%, 95%, 82.5% and 75% when the critical points were 2.0, 5.0, 5.0 and 5.0 respectively. CONCLUSIONS: SELDI-TOF-MS ProteinChip technology is a quickly, easy and convenient, and high-throughput analyzing method capable of screening several relatively specific, potential biomarkers from the urines of RCC patients and had better clinical value.
BACKGROUND: Promoter methylation is an important pathway in transcriptional silencing of tumor suppressor genes (TSGs) in brain tumors. The identified 3p21.3 tumor suppressor gene RAS association domain family protein 1A (RASSF1A) is highly methylated in primary lung, breast and other tumors. We investigated the promoter methylation and gene expression of RASSF1A in gliomas. METHODS: The methylation status of the promoter region of RASSF1A, p16INK4A and death-associated protein kinase (DAPK) genes was analyzed by methylation-specific PCR (MSP) in 41 surgically resected gliomas. RASSF1A expression was also detected by reverse-transcription polymerase chain reaction (RT-PCR) in 28 glioma tissues. RESULTS: The frequencies of RASSF1A, p16INK4A and DAPK promoter methylation were 13/41 (31.7%), 3/41 (7.3%) and 6/41 (14.6%) respectively. However, the methylations of those genes were not correlated with the clinical characteristics of patients (tumor grade, tumor types and sex). Among 28 glioma tissues, 6 showed the loss of the gene (21.4%). Promoter hypermethylation of RASSF1A is associated with loss of gene expression in glioma tissues. (p=0.022). CONCLUSIONS: Our results suggested that the RASSF1A gene might play an important role in glioma carcinogenesis. It also gives us an insight for future glioma medical therapy with a demethylating agent.
BACKGROUND: Recent advances in proteomic profiling technologies, such as surface-enhanced laser desorption/ionization mass spectrometry (SELDI), have allowed preliminary profiling and identification of tumor markers in biological fluids in several cancer types and establishment of clinically useful diagnostic computational models. We developed a bioinformatics tool and used it to identify proteomic patterns in urine that distinguish transitional cell carcinoma (TCC) from noncancer. METHODS: Proteomic spectra were generated by mass spectroscopy (surface-enhanced laser desorption and ionization). A preliminary "training" set of spectra derived from analysis of urine from 46 TCC patients, 32 patients with benign urogenital diseases (BUD), and 40 age-matched unaffected healthy men were used to train and develop a decision tree classification algorithm that identified a fine-protein mass pattern that discriminated cancer from noncancer effectively. A blinded test set, including 38 new cases, was used to determine the sensitivity and specificity of the classification system. RESULTS: The algorithm identified a cluster pattern that, in the training set, segregated cancer from noncancer with sensitivity of 84.8% and specificity of 91.7%. The discriminatory pattern correctly identified. A sensitivity of 93.3% and a specificity of 87.0% for the blinded test were obtained when comparing the TCC vs. noncancer. CONCLUSIONS: These findings justify a prospective population-based assessment of proteomic pattern technology as a screening tool for bladder cancer in high-risk and general populations.
Pigment epithelium-derived factor (PEDF) is a potent inhibitor of angiogenesis and an inducer of neural differentiation. We previously reported the loss of PEDF expression in glioma progression. In this study, we investigated whether PEDF overexpression could suppress glioma growth and invasion. Glioma cell line U251 was stably transfected with a full-length human PEDF expression vector. The expression and release of various cytokines and angiogenic factors into the medium were analyzed by real-time reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and gelatin zymography. Apoptosis was checked by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Growth inhibition was evaluated by using the in vitro Matrigel invasion. Tumorigenicity was examined in vivo by subcutaneous xenotransplantation into severe combined immunodeficient mice. In U251 cells overexpressing PEDF, thrombospondin-1 protein was upregulated (5.3-fold more), but the production of vascular endothelial growth factor (VEGF) (1.8-fold less) and basic fibroblast growth factor (2.5-fold less) was lower than in cells transfected with the vector only. PEDF also downregulated the production of matrix metalloproteinase-9. Conditioned medium collected from the PEDF-transfected U251 cells showed a significant reduction of VEGF expression. In vitro invasiveness was reduced by approximately 40%. PEDF expression prevented the growth of transfected cells and caused a significant increase in the percentage of cells undergoing apoptosis (50.4% in PEDF-transfected cells). Furthermore, the size of xenotransplants was significantly smaller. In conclusion, PEDF overexpression decreased malignancy, and this might be attributed to the promotion of apoptosis and the regulation of expression of angiogenic effectors. Thus, treatment with PEDF may be useful in patients with malignant gliomas. However, the mechanism of apoptosis induction needs to be investigated.
An enzyme-linked immunosorbent assay (ELISA) and a rapid immunochromatographic test for detection of immunoglobulin G (IgG) antibodies in severe acute respiratory syndrome (SARS) patients were developed by utilizing the well-characterized recombinant proteins Gst-N and Gst-U274. The ELISA detected IgG antibodies to SARS-CoV in all 74 convalescent-phase samples from SARS patients while weakly cross-reacting to only 1 of the 210 control sera from healthy donors. This finding thus led to a kit sensitivity, specificity, and accuracy of 100, 99.5, and 99.6%, respectively. The test thus provided a positive predictive value (PPV) of 98.7% and a negative predictive value (NPV) of 100%. In addition, the ELISA gave a positive delta of 5.4 and a negative delta of 3.6, indicating an excellent differentiation between positives and negatives. The same recombinant proteins were also applied to a newly developed platform for the development of a 15-min rapid test. The resulting rapid test has an excellent agreement of 99.6%, with a kappa value of 1.00, with the ELISA. Again, this rapid test was able to detect 100% of the samples tested (n = 42) while maintaining a specificity of 99.0% (n = 210). The PPV and NPV for the rapid test thus reached 95.3 and 100%, respectively.
A newly developed severe acute respiratory syndrome (SARS)-specific enzyme-linked immunosorbent assay (ELISA) was further validated to confirm cutoff values and evaluate its diagnostic performance with clinical samples. In parallel, an immunochromatographic test was also evaluated. A total of 227 clinical serum specimens collected from SARS patients were used in the study, together with 385 samples from healthy donors. By use of an immunofluorescent (IF) test as the "gold standard", both the ELISA and the immunochromatographic test were able to detect immunoglobulin G antibodies to SARS not only from late-convalescent-stage samples (>21 days from the onset of clinical symptoms), as previously established, but also from early-acute-phase samples (1 to 10 days from onset). The ELISA, using an optical density (OD) of 0.25 as its cutoff value, produced the best sensitivity while maintaining high specificity. It detected SARS-specific antibodies in 58, 70, 75, and 95%, respectively, of the four groups of samples collected from patients 1 to 10 days, 11 to 20 days, 21 to 30 days, and more than 30 days after the onset of clinical symptoms. Similarly, the immunochromatographic test detected SARS-specific antibodies in 55, 68, 81, and 79% of the four groups, respectively. The overall specificities for the ELISA and the rapid test were 99.5 and 97.7%, respectively. Although the positive correlation observed between the ELISA OD values and the IF titers was moderate (r = 0.6915; P < 0.001), the detection rates of both the ELISA and the rapid test were found well in agreement with the IF titers.
A Western immunoblot assay for confirmatory serodiagnosis of severe acute respiratory syndrome (SARS) was developed utilizing viral lysate antigens combined with a recombinant nucleocapsid protein, GST-N (glutathione S-transferase-nucleocapsid) of the SARS coronavirus (SARS-CoV). The viral lysate antigens were separated by electrophoresis and transblotted onto nitrocellulose membranes. The resultant membrane was subsequently added with the GST-N recombinant protein at a specific location. The positions of bands corresponding to some of the structural proteins immobilized on the membrane were then located and verified with mouse or rabbit antisera specific to the respective proteins. The Western immunoblot assay was able to detect antibodies to SARS-CoV in all 40 serum specimens from SARS patients and differentiate the SARS-positive samples from those of the healthy donor or non-SARS patient controls (150 samples) when set criteria were followed. In addition, when the immunoblot was used to test samples considered falsely positive by an in-house-developed SARS-specific enzyme-linked immunosorbent assay, band patterns different from those with samples from SARS patients were obtained.
The authors labeled bovine serum albumin (BSA) with a new europium chelator 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA) which was synthesized by solid phase time-resolved fluorescence immunoassay (TRFIA) technology. The process of BCPDA-labeling-BSA reaction was studied. Using Coomassie brilliant blue method, concentrations of BSA and BCPDA were determined in BCPDA-BSA labeled sample. The labeling reaction condition was studied. Labeling ratio and protein labeling recovery were calculated. BCPDA-BSA-Eu3+ complex has a very large Stokes shift (270 nm) and can emit very strong fluorescence band at 611.2 nm which is very narrow (10 nm). BCPDA-BSA-Eu3+ complex exhibits very long fluorescence lifetimes by the experiment demonstration. Also, BCPDA and protein-BCPDA-Eu3+ complex is relatively stable.
OBJECTIVE: To explore the effect of hypoxia and high glucose concentration on the production and secretion of vascular endothelial growth factor (VEGF) and pigment epithelium derived factor (PEDF), an antiangiogenesis factor, in the cultured human retinal pigment epithelium (RPE) cells. METHODS: Human RPE cells were cultured under normoxic or hypoxic (1% O(2)) condition with or without (25 mmol/L) glucose. RT-PCR and real-time quantificaton analysis were used to examine the expression of VEGF and of PEDF mRNAs. Western blot analysis was used to measure the levels of VEGF and PEDF proteins. RESULTS: The expression of VEGF mRNA in RPE cells under hypoxic condition for 12 hours was 2.6 times that under the normoxic condition (P = 0.001), and the expression of PEDF mRNA was only 0.77 time that of the controls (P = 0.251). Under hypoxic condition with high concentration of glucose the expression of VEGF mRNA in RPE cells was 3.8 times that under the normoxic condition (P < 0.001), and the expression of PEDF mRNA was further decreased (only 0.23 time that of the controls, P = 0.02). The expression levels of VEGF protein under hypoxic condition with and without glucose were 1.69 and 1.27 times respectively those under the normoxic condition (P < 0.0001 and P = 0.004). The expression level of PEDF protein under hypoxic condition with glucose was 0.49 time that under the normoxic condition (P < 0.0001) and the expression level of PEDF protein under hypoxic condition without glucose was 0.92 time that under the normoxic condition (P = 0.114). CONCLUSION: Hypoxia indirectly influence the downregulation of PEDF and high concentration of glucose directly downregulates the expression of PEDF and increases the expression of VEGF simultaneously, thus supporting the concept that hyperglycemia is one of the most dangerous consequences of diabetes-associated "glucose toxicity" in vivo.
Lipocalin-type prostaglandin D synthase (LPGDS; PGH(2)D-isomerase; EC 5.3.99.2) is a bifunctional protein first identified in the mammalian brain. It acts as a PGD(2)-producing enzyme and a retinoid transporter. Recent studies have shown that LPGDS is anomalously expressed in ovarian tumors and that retinoid may have a role as an ovarian cancer chemotherapeutic agent. To determine whether there is a relationship between retinoid and LPGDS in ovarian tumors, we examined the regulation of the gene encoding LPGDS by all-trans retinoic acid (RA). Real-time quantitative RT-PCR analysis showed that RA strongly induced the accumulation of LPGDS mRNA in human 3AO ovarian cancer cells. Furthermore, treatment of the cells with RA induced the synthesis and secretion of LPGDS into the culture medium. This increased expression of LPGDS was accompanied by an inhibition of cell proliferation in the ovarian cancer cells. Prostaglandin D synthase, ovarian cancer, retinoic acid, real-time quantitative RT-PCR.
BACKGROUND: Solid tumors requires neovascularization for growth and metastasis. Angiogenesis depends on the local balance between positive and negative effectors, the production of which can be regulated by oncogenes and tumor suppressor genes. The aim of this study was to investigate expression of p73, a gene homologous to the tumor suppressor gene p53, in colorectal cancer and its relationship to angiogenesis. METHODS: p73 expression was examined by immunohistochemistry and western blot analysis on 56 primary colon carcinomas with matched normal mucosas. Vascular endothelial growth factor (VEGF) and microvessels were highlighted using a monoclonal antibody specific to VEGF and von Willebrand factor (vWF). RESULTS: The immunoexpressions of p73 were significantly higher in the primary colorectal carcinomas than that in the matched normal mucosa (P < 0.001). Western blotting showed that 85% patients have a high level of p73 expression (more than double the normal level). A close association between p73 and VEGF expression level was observed (P = 0.016). Colorectal adenocarcinoma that expressed p73 showed significantly greater vascularity than p73-negative tumors (P = 0.012). However, no association between immunoexpression of p73 and tumor stage or differentiation was observed. CONCLUSION: These findings suggest a potential role of p73 in tumor angiogenesis.
PURPOSE: Pterygia are histologically composed of proliferating fibrovascular tissue. This study compared expression levels of an angiogenic inhibitor, pigment epithelium-derived factor (PEDF), in pterygia with those in normal corneal and conjunctival tissues. METHODS: The normal human conjunctival and corneal tissues were obtained from surgery or from donor eyes without ocular diseases. Pterygia were excised by therapeutic surgery under a microscope. Pigment epithelium-derived factor and vascular endothelial growth factor (VEGF) were measured by Western blot analysis. Their cellular localizations were determined by immunohistochemistry. RESULTS: Intensive PEDF immunostaining was detected in all the normal corneal and conjunctival samples analyzed, predominantly in the epithelium and endothelium of the cornea and in the epithelium of the limbus and conjunctiva. Under the same immunostaining conditions, pterygial samples showed negative or faint PEDF staining. In contrast, the same pterygial samples all showed intensive VEGF staining, predominantly in the epithelium and in blood vessels. Western blot analysis confirmed that the average PEDF level in pterygia was drastically lower than those in normal corneal and conjunctival tissues, respectively. In contrast, the VEGF level in pterygia was significantly higher than in the normal tissues. CONCLUSION: Pterygia exhibit significantly lower PEDF but higher VEGF levels than those in normal corneas and conjunctivae. The decreased PEDF level in pterygia may play a role in the formation and progression of pterygia.