Biomedical subjects

Dexian Zheng

Publications and source records attributed to Dexian Zheng.

At least 19 recordsLinked to original sources

PubMed2006

Therapeutic expression of an anti-death receptor 5 single-chain fixed-variable region prevents tumor growth in mice.

The clinical use of the single-chain fixed-variable (scFv) fragments of recombinant monoclonal antibodies as credible alternatives for classic therapeutic antibodies has two limitations: rapid blood clearance and inefficient local expression of functional molecules. In attempt to address these issues, we have developed a novel gene therapy protocol in which the anti-death receptor 5 (DR5) scFv fragments were either in vitro expressed in several tumor cell lines, or in vivo expressed in mice, using recombinant adeno-associated virus (rAAV)-mediated gene transfer. Viral transduction using the rAAV-S3C construct, which encodes a scFv molecule (S3C scFv) specific to DR5, led to stable expression in tumor cell lines and showed apoptosis-inducing activity in vitro, which could be inhibited by recombinant DR5 but not by DR4. A single i.m. injection of rAAV-S3C virus in nude mice resulted in stable expression of DR5-binding S3C scFv proteins in mouse sera for at least 240 days. Moreover, the expression of S3C scFv was associated with significant suppression of tumor growth and the increase of tumor cell apoptosis in previously established s.c. human lung LTEP-sml and liver Hep3B tumor xenografts.

Animals↗

PubMed2006

An integrated machine learning system to computationally screen protein databases for protein binding peptide ligands.

A fairly large set of protein interactions is mediated by families of peptide binding domains, such as Src homology 2 (SH2), SH3, PDZ, major histocompatibility complex, etc. To identify their ligands by experimental screening is not only labor-intensive but almost futile in screening low abundance species due to the suppression by high abundance species. An ideal way of studying protein-protein interactions is to use high throughput computational approaches to screen protein sequence databases to direct the validating experiments toward the most promising peptides. Predictors with only good cross-validation were not good enough to screen protein databases. In the current study we built integrated machine learning systems using three novel coding methods and screened the Swiss-Prot and GenBank protein databases for potential ligands of 10 SH3 and three PDZ domains. A large fraction of predictions has already been experimentally confirmed by other independent research groups, indicating a satisfying generalization capability for future applications in identifying protein interactions.

Amino Acid Motifs↗

PubMed2005

Microwave-assisted protein preparation and enzymatic digestion in proteomics.

The combinations of gel electrophoresis or LC and mass spectrometry are two popular approaches for large scale protein identification. However, the throughput of both approaches is limited by the speed of the protein digestion process. Present research into fast protein enzymatic digestion has been focused mainly on known proteins, and it is unclear whether these results can be extrapolated to complex protein mixtures. In this study microwave technology was used to develop a fast protein preparation and enzymatic digestion method for protein mixtures. The protein mixtures in solution or in gel were prepared and digested by microwave-assisted protein enzymatic digestion, which rapidly produces peptide fragments. The peptide fragments were further analyzed by capillary LC and ESI-ion trap-MS or MALDI-TOF-MS. The technique was optimized using bovine serum albumin and then applied to human urinary proteins and yeast lysate. The method enabled preparation and digestion of protein mixtures in solution (human urinary proteins) or in gel (yeast lysate) in 6 or 25 min, respectively. Equivalent (in-solution) or better (in-gel) digestion efficiency was obtained using microwave-assisted protein enzymatic digestion compared with the standard overnight digestion method. This new application of microwave technology to protein mixture preparation and enzymatic digestion will hasten the application of proteomic techniques to biological and clinical research.

Chromatography, Liquid↗

PubMed2005

Concanavalin A-captured glycoproteins in healthy human urine.

Both the urinary proteome and its glycoproteome can reflect human health status, and more directly, functions of kidney and urinary tracts. Because the high abundance protein albumin is not N-glycosylated, the urine N-glycoprotein enrichment procedure could deplete it, and urine proteome could thus provide a more detailed protein profile in addition to glycosylation information especially when albuminuria occurs in some kidney diseases. In terms of describing the details of urinary proteins, the urine glycoproteome is even a better choice than the proteome itself. Pooled urine samples from healthy volunteers were collected and acetone-precipitated for proteins. N-Linked glycoproteins enriched with concanavalin A affinity purification were separated and analyzed by SDS-PAGE-reverse phase LC/MS/MS or two-dimensional LC/MS/MS. A total of 225 urinary proteins were identified based on two-hit criteria with reliability over 97% for each peptide. Among these proteins, 94 were identified in previous urine proteome works, 150 were annotated as glycoproteins in Swiss-Prot, and 43 were predicted as glycoproteins by NetNGlyc 1.0. A number of known biomarkers and disease-related glycoproteins were identified. Because changes in protein quantity or the glycosylation status can lead to changes in the concanavalin A-captured glycoprotein profile, specific urine glycoproteome patterns might be observed for specific pathological conditions as multiplex urinary biomarkers. Knowledge of the urine glycoproteome is important in understanding kidney and body function.

Concanavalin A↗

PubMed2005

A novel anti-human DR5 monoclonal antibody with tumoricidal activity induces caspase-dependent and caspase-independent cell death.

Like anti-Fas monoclonal antibodies, some monoclonal antibodies against tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors have tumoricidal activity too. In this article we report a novel mouse anti-human DR5 monoclonal antibody, AD5-10, that induces apoptosis of various tumor cell lines in the absence of second cross-linking in vitro and showed strong tumoricidal activity in vivo. AD5-10 does not compete with TRAIL for binding to DR5 and synergizes with TRAIL to induce apoptosis of tumor cells. AD5-10 induces both caspase-dependent and caspase-independent cell death in Jurkat cells, whereas TRAIL induces only caspase-dependent cell death. We show for the first time that DR5 can mediate caspase-independent cell death, and DR5 can mediate distinct cell signals when interacting with different extracellular proteins. Studies on AD5-10 help us to understand more on the functions of DR5 and may provide new ideas for cancer immunotherapy.

Animals↗

PubMed2005

PKCdelta protects human breast tumor MCF-7 cells against tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a number of tumorogenic or transformed cells, yet is relatively non-toxic to most normal cells, therefore, it is a promising agent for cancer therapy. However, some cancer cell lines were resistant to TRAIL cytoxicity, including MCF-7 breast cancer cells. The mechanism is not clear. Here, we report that protein kinase C delta (PKCdelta) protects MCF-7 cells from the recombinant soluble TRAIL (rsTRAIL)- mediated apoptosis. It was demonstrated that rottlerin, a PKCdelta inhibitor, sensitized MCF-7 cells to rsTRAIL cytoxicity. Combination of rottlerin and rsTRAIL inhibited PKCdelta translocation from the cytosol to membrane, and PKCdelta kinase activity on the cell membrane was kept pace with the change of PKCdelta expression. Moreover, inhibition of PKCdelta by interference RNA could facilitate apoptosis of MCF-7 cells induced by rsTRAIL. Further experiments on the signal machinery showed that rottlerin increased the sensitivity of MCF-7 cells to rsTRAIL by suppressing the transcription activity of NF-kappaB, and enhancing the caspase-processing to generate executive apoptotic signals. These findings indicate that PKCdelta functions as a survival factor protecting MCF-7 cells from the apoptosis induced by rsTRAIL.

Acetophenones↗

PubMed2005

Recombinant adeno-associated virus-mediated TRAIL gene therapy suppresses liver metastatic tumors.

To evaluate the tumoricidal activity of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) on disseminated liver metastatic tumors, we constructed a recombinant adeno-associated virus (rAAV) expressing the extracellular domain (95-281aa) of human TRAIL (TRAIL(95-281), and the recombinant virus was designated as rAAV-TRAIL) using the 3-plasmid, helper-virus-free, packaging system. Transduction of mouse lymphoma EL-4 cells and Jurkat T cells lead to the expression of TRAIL(95-281) protein in both virus-transduced cells and the culture media, along with apoptosis of these cells in vitro. The therapeutic potential of rAAV-TRAIL was then evaluated in an orthotopic transplanted mouse model mimicking liver cancer metastasis, which was established by injection of EL-4 cells into the liver of C57BL/6 mice via the hepatic portal veins. Subsequent intraportal vein injection of rAAV-TRAIL, not the control virus, into the liver of these mice resulted in significant suppression of tumor growth and prolonged survival, while normal hepatocyte toxicity is undetectable. Histological and biochemical analysis in tumor tissue and serum confirmed that TRAIL(95-281) was stably expressed in relatively high level in hepatocytes and was secreted into the serum in active trimeric form. Futhermore, the mechanism for rAAV-TRAIL to inhibit tumor growth was by inducing apoptosis of the tumor cells metastasizing to the livers. These results strongly suggest that the rAAV-TRAIL-mediated gene delivery could be a promising approach for the treatment of liver metastasis cancer.

Adenoviridae↗

PubMed2005

A crucial role of angiotensin converting enzyme 2 (ACE2) in SARS coronavirus-induced lung injury.

During several months of 2003, a newly identified illness termed severe acute respiratory syndrome (SARS) spread rapidly through the world. A new coronavirus (SARS-CoV) was identified as the SARS pathogen, which triggered severe pneumonia and acute, often lethal, lung failure. Moreover, among infected individuals influenza such as the Spanish flu and the emergence of new respiratory disease viruses have caused high lethality resulting from acute lung failure. In cell lines, angiotensin-converting enzyme 2 (ACE2) has been identified as a potential SARS-CoV receptor. The high lethality of SARS-CoV infections, its enormous economic and social impact, fears of renewed outbreaks as well as the potential misuse of such viruses as biologic weapons make it paramount to understand the pathogenesis of SARS-CoV. Here we provide the first genetic proof that ACE2 is a crucial SARS-CoV receptor in vivo. SARS-CoV infections and the Spike protein of the SARS-CoV reduce ACE2 expression. Notably, injection of SARS-CoV Spike into mice worsens acute lung failure in vivo that can be attenuated by blocking the renin-angiotensin pathway. These results provide a molecular explanation why SARS-CoV infections cause severe and often lethal lung failure and suggest a rational therapy for SARS and possibly other respiratory disease viruses.

Analysis of Variance↗

PubMed2005

Overexpression of soluble TRAIL induces apoptosis in human lung adenocarcinoma and inhibits growth of tumor xenografts in nude mice.

Recombinant adeno-associated virus 2/5 (rAAV2/5), a hybrid rAAV-2 with AAV-5 capsid, seems to be a very efficient delivery vector for the transduction of the lung adenocarcinoma cell line A549. Infection of the A549 cell line with a rAAV2/5 vector encoding the extracellular domain of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL, amino acids 114-281) resulted in secretion of soluble TRAIL (sTRAIL) and induction of apoptosis in these cells. rAAV2/5-sTRAIL mediated delivery and stable expression of sTRAIL resulted in the presence of the trimeric form of sTRAIL in sera of nude mice that were implanted with s.c. or orthotopic A549 tumors. The rAAV2/5-sTRAIL transduction of the tumors resulted in a statistically significant reduction in tumor growth and prolonged survival of the tumor-bearing animals. Primary cell culture, histologic examination of the tumors, and serum analyses showed the absence of detectable TRAIL-induced toxicity in normal tissues including the liver. The successful inhibition of lung cancer growth and the absence of detectable toxicity suggest a putative role for rAAV2/5-sTRAIL(114-281) in the therapy of lung cancer.

Adenocarcinoma↗

PubMed2005

Oral adeno-associated virus-sTRAIL gene therapy suppresses human hepatocellular carcinoma growth in mice.

The extracellular domain of the tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) may function as a soluble cytokine to selectively kill various cancer cells without toxicity to most normal cells. We constructed a series of recombinant adeno-associated virus (AAV) vectors expressing the extracellular domain of human TRAIL fused with signal peptides of human insulin, interferon, human growth hormone, and serum albumin and designated them as AAV-ISN-T, AAV-IFN-T, AAV-HGH-T, and AAV-Alb-T, respectively. Transduction of human SMMC-7721 liver cancer cells with AAV-ISN-T led to higher levels of TRAIL(95-281) protein expression in the cell culture media and produced more apoptosis of the cells in vitro than those with AAV-IFN-T, AAV-HGH-T, and AAV-Alb-T. The therapeutic potential of AAV-ISN-T was then evaluated in a transplanted mouse model established by injection of human liver cancer SMMC-7721 cells subcutaneously. Subsequent oral or intraperitoneal administration of AAV-ISN-T resulted in a rapid, high level and long time expression of soluble TRAIL in the sera and livers of the animals, as well as effective suppression of tumor growth, with no toxicity to normal hepatocytes. These data strongly suggest that it is possible to increase soluble TRAIL expression to make full use of tumoricidal activity of TRAIL as a therapeutic strategy. In conclusion, we provide evidence that oral administration of AAV-TRAIL might be an important alternative route with practical significance for cancer gene therapy.

Animals↗

PubMed2005

Human urine proteome analysis by three separation approaches.

The urinary proteome is known to be a valuable field of study related to organ functions. There have been several extensive urine proteome studies. However, the overlapping rate among different studies is relatively low. Whether the low overlapping rate was caused by different sample sources, preparation, separation and identification methods is unknown. Moreover, low molecular mass (<10 kDa) proteins have not been studied extensively. In this report, male and female pooled urine samples were collected from healthy volunteers. The urinary proteins were acetone precipitated, separated and identified by three approaches, 1-DE plus 1-D LC/MS/MS, direct 1-D LC/MS/MS and 2-D LC/MS/MS. 1-D tricine gels were used to separate low molecular mass proteins. The tandem mass spectra of positive identifications were quality controlled both by manual validation and using advanced mass spectrum scanner software. A total of 226 urinary proteins were identified; 171 proteins were identified by proteomics approach for the first time, including 4 male-specific proteins. Twelve low molecular mass proteins were identified. Most urinary proteins had a molecular mass between 30 and 60 kDa and a pI between 4 and 10. The apparent molecular masses of many proteins were different from theoretical ones, which indicated their post-translational modification and degradation. The effects of sample preparation, separation and identification methods on the overlapping rate of different experiments are discussed.

Adult↗

PubMed2005

An analysis of protein abundance suppression in data dependent liquid chromatography and tandem mass spectrometry with tryptic peptide mixtures of five known proteins.

Reverse phase liquid chromatography (RPLC) has been widely used in proteomics research for peptide separation. When protein samples are separated by RPLC and identified with electrospray ion trap mass spectrometry (ESI-MS), the signals of high-abundance proteins may suppress those of low-abundance proteins, a phenomenon known as abundance suppression. To what degree the abundance suppression correlates to the number of tryptic peptides in the high-abundance proteins has not been carefully investigated. We tried to answer this question by studying the mixtures digested from five known proteins. The numbers of identified tryptic peptides (longer than five amino acids) of the five proteins ranged from 12 to 47. Four different peptide mixtures with 10- to 100-fold abundance differences of five known proteins were separated by RPLC and identified by ESI-MS. Our results showed that abundance suppression was related to the tryptic peptide numbers in the high-abundance protein. Within a 100-fold protein abundance difference range, tryptic peptide number in the low-abundance proteins could be suppressed up to seven times by high-abundance proteins. The procedure we suggest here can help to identify low-abundance proteins co-purified with their high-abundance binding protein. The result can also help to identify specific high-abundance proteins for removal by immunoaffinity.

Animals↗

PubMed2005

Comparative proteome analysis of breast cancer and normal breast.

Breast cancer is a leading cause of death for women. The underlying molecular mechanism is still not well understood. In this study, two-dimensional gel electrophoresis combined with mass spectrometry was used to analyze changes in the proteome of infiltrating ductal carcinoma compared to normal breast tissue. Ten sets of two-dimensional gels per experimental condition were analyzed and more than 500 spots each were detected. This revealed 39 spots for which expression in breast cancer cells were reproducibly altered more than twofold compared to normal controls (p < 0.01). These spots represented 25 different proteins after identification using the database search after mass spectrometry, comprising cell defense proteins, enzymes involved in glycolytic energy metabolism and homeostasis, protein folding and structural proteins, proteins involved in cytoskeleton and cell motility, and proteins involved in other functions. In addition, 28 nondifferentially expressed proteins with different functions were also mapped and identified, which might help to establish a two-dimensional gel electrophoresis reference map of human breast cancer. Our study shows that proteomics offers a powerful methodology to detect the proteins that show different expression patterns in breast cancer tissue and may provide an accurate molecular classification. The differentially expressed proteins may be used as potential candidate markers for diagnostic purposes or for determination of tumor sensitivity to therapy. The functional implications of the identified proteins are discussed.

Biomarkers, Tumor↗

PubMed2005

Current understanding on the immunological functions of tumor necrosis factor-related apoptosis-inducing ligand.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in various tumor cells and virus-infected cells, but rarely in normal cells. The killing specificity of TRAIL has brought great interests to develop a novel apoptosis-based anti-tumor agent for clinical application. TRAIL is expressed in many normal tissues and cells, such as liver, brain, kidney, heart, colon, lung, and testis. However, immunological and physiological functions of TRAIL in vivo have not been understood well. In the present paper we summarized the progress in the research on immunological functions of TRAIL.

Animals↗

PubMed2004

AMASS: software for automatically validating the quality of MS/MS spectrum from SEQUEST results.

Time-consuming and experience-dependent manual validations of tandem mass spectra are usually applied to SEQUEST results. This inefficient method has become a significant bottleneck for MS/MS data processing. Here we introduce a program AMASS (advanced mass spectrum screener), which can filter the tandem mass spectra of SEQUEST results by measuring the match percentage of high-abundant ions and the continuity of matched fragment ions in b, y series. Compared with Xcorr and DeltaCn filter, AMASS can increase the number of positives and reduce the number of negatives in 22 datasets generated from 18 known protein mixtures. It effectively removed most noisy spectra, false interpretations, and about half of poor fragmentation spectra, and AMASS can work synergistically with Rscore filter. We believe the use of AMASS and Rscore can result in a more accurate identification of peptide MS/MS spectra and reduce the time and energy for manual validation.

Algorithms↗

PubMed2004

A systematical analysis of tryptic peptide identification with reverse phase liquid chromatography and electrospray ion trap mass spectrometry.

In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identified peptides in reverse phase liquid chromatography and electrospray tandem mass spectrometry (RPLC-MS/MS) analysis. Following protein digestion with trypsin, the peptide mixture was analyzed by on-line RPLC-MS/MS. Bovine serum albumin (BSA) was used to optimize acetonitrile (ACN) elution gradient for tryptic peptides, and Cytochrome C was used to retest the gradient and the sensitivity of LC-MS/MS. The characteristics of identified peptides were also analyzed. In our experiments, the suitable ACN gradient is 5% to 30% for tryptic peptide elution and the sensitivity of LC-MS/MS is 50 fmol. Analysis of the tryptic peptides demonstrated that longer (more than 10 amino acids) and multi-charge state (+2, +3) peptides are likely to be identified, and the hydropathicity of the peptides might not be related to whether it is more likely to be identified or not. The number of identified peptides for a protein might be used to estimate its loading amount under the same sample background. Moreover, in this study the identified peptides present three types of redundancy, namely identification, charge, and sequence redundancy, which may repress low abundance protein identification.

Acetonitriles↗

PubMed2004

8-Chloro-adenosine sensitizes a human hepatoma cell line to TRAIL-induced apoptosis by caspase-dependent and -independent pathways.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor (TNF) super-family, induces apoptosis in various cancer cells with little or no effect on normal cells. 8-Chloro-adenosine (8-Cl-Ado) is a potential anti-cancer chemical agent now in clinical trail phase II, though its molecular mechanism remains poorly understood. In the present study, we report that 8-Cl-Ado can promote TRAIL killing activity in the hepatoma cell line BEL-7402 in dose- and time-dependent manner when jointly used in vitro. We showed that the expression of death receptor DR5, but not DR4 was up-regulated and the decoy receptor DcR1 was down-regulated in the cells treated with 8-Cl-Ado and the recombinant soluble TRAIL (rsTRAIL, 95-281 a.a.). Further experiments demonstrated that caspase-family inhibitor z-VAD-fmk prevented the cells from apoptosis induced by co-treatment with 8-Cl-Ado and rsTRAIL for 6 h, however, apoptosis occurred in the cells cultured for 24 h, suggesting that co-treatment induce a caspase-dependent and -independent signaling pathway in the BEL-7402 cells. This phenomenon was confirmed by cleavage analysis of caspase-3 and poly(ADP-ribose) polymerase (PARP), and ROS (reactive oxygen species) assay, respectively. Moreover, transcriptional activity test showed that NF-kappaB was inhibited in the BEL-7402 cells during co-treatment. Our results provided evidence for the first time that 8-Cl-Ado sensitizes the human hepatoma cells BEL-7402 to rsTRAIL-induced apoptosis by up-regulating DR5 expression, inactivating the NF-kappaB activity, and signaling by the caspase-dependent and -independent pathway.

2-Chloroadenosine↗

PubMed2003

Tyrosine mutation in CD3epsilon-ITAM blocked T lymphocyte apoptosis mediated by CD3epsilon.

Anti-CD3epsilon monoclonal antibody induces programmed cell death of thymocytes and accelerates activation-induced cell death (AICD) by apoptosis of matured or transformed T lymphocytes. However, the underlying molecular mechanism of this phenomenon is unclear. Therefore, we produced a chimera protein (termed CD8epsilon by fusing the extracellular and transmembrane domains of human CD8alpha to the intracellular domain of mouse CD3epsilon and expressed in CD8- Jurkat T cells. Stable cell lines of mutants expressing the motifs of Y170F, Y181F, and Y170F/Y181F in the CD3epsilon-ITAM were established. Experiments showed that apoptosis could be induced only in the T Jurkat cells with intact CD3epsilon intracellular domain, but not in the cells with the mutant CD8epsilon when stimulated with anti-CD8alpha monoclonal antibody. This finding indicated that a single tyrosine mutation in CD3epsilon-ITAM blocked the signal transduction, causing the cell death by apoptosis when stimulated by CD8epsilon molecule. During the apoptotic process, we showed that expressions of CD95, CD95L and Nur77 were enhanced in stimulated TJK cells but not in control cells. In addition, the high expression of Nur77 kept pace with the onset of apoptosis of T-cells mediated by CD8epsilon. We further showed that 3'-phosphatidylinositol kinase (PI3K) were not only enhanced during T cell activation, but also in the AICD process. The results suggest that PI3K/Akt is not only a cell proliferation signal, but also a potential apoptosis regulator in T lymphocytes.

Animals↗