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Biomedical subjects

Jian Cao

Publications and source records attributed to Jian Cao.

At least 19 recordsLinked to original sources
PubMed2007

MT1-MMP down-regulates the glucose 6-phosphate transporter expression in marrow stromal cells: a molecular link between pro-MMP-2 activation, chemotaxis, and cell survival.

Bone marrow-derived stromal cells (BMSC) are avidly recruited by experimental vascularizing tumors, which implies that they must respond to tumor-derived growth factor cues. In fact, BMSC chemotaxis and cell survival are regulated, in part, by the membrane type-1 matrix metalloproteinase (MT1-MMP), an MMP also involved in pro-MMP-2 activation and in degradation of the extracellular matrix (ECM). Given that impaired chemotaxis was recently observed in bone marrow cells isolated from a glucose 6-phosphate transporter-deficient (G6PT-/-) mouse model, we sought to investigate the potential MT1-MMP/G6PT signaling axis in BMSC. We show that MT1-MMP-mediated activation of pro-MMP-2 by concanavalin A (ConA) correlated with an increase in the sub-G1 cell cycle phase as well as with cell necrosis, indicative of a decrease in BMSC survival. BMSC isolated from Egr-1-/- mouse or MT1-MMP gene silencing in BMSC with small interfering RNA (siMT1-MMP) antagonized both the ConA-mediated activation of pro-MMP-2 and the induction of cell necrosis. Overexpression of recombinant full-length MT1-MMP triggered necrosis and this was signaled through the cytoplasmic domain of MT1-MMP. ConA inhibited both the gene and protein expression of G6PT, while overexpression of recombinant G6PT inhibited MT1-MMP-mediated pro-MMP-2 activation but could not rescue BMSC from ConA-induced cell necrosis. Cell chemotaxis in response to the tumorigenic growth factor sphingosine 1-phosphate was significantly abrogated in siMT1-MMP BMSC and in chlorogenic acid-treated BMSC. Altogether, we provide evidence for an MT1-MMP/G6PT signaling axis that regulates BMSC survival, ECM degradation, and mobilization. This may lead to optimized clinical applications that use BMSC as a platform for the systemic delivery of therapeutic or anti-cancer recombinant proteins in vivo.

Animals↗
PubMed2006

Chemical genetics reveals an RGS/G-protein role in the action of a compound.

We report here on a chemical genetic screen designed to address the mechanism of action of a small molecule. Small molecules that were active in models of urinary incontinence were tested on the nematode Caenorhabditis elegans, and the resulting phenotypes were used as readouts in a genetic screen to identify possible molecular targets. The mutations giving resistance to compound were found to affect members of the RGS protein/G-protein complex. Studies in mammalian systems confirmed that the small molecules inhibit muscarinic G-protein coupled receptor (GPCR) signaling involving G-alphaq (G-protein alpha subunit). Our studies suggest that the small molecules act at the level of the RGS/G-alphaq signaling complex, and define new mutations in both RGS and G-alphaq, including a unique hypo-adapation allele of G-alphaq. These findings suggest that therapeutics targeted to downstream components of GPCR signaling may be effective for treatment of diseases involving inappropriate receptor activation.

Animals↗
PubMed2006

Loss of intercellular adhesion activates a transition from low- to high-grade human squamous cell carcinoma.

The relationship between loss of intercellular adhesion and the biologic properties of human squamous cell carcinoma is not well understood. We investigated how abrogation of E-cadherin-mediated adhesion influenced the behavior and phenotype of squamous cell carcinoma in 3D human tissues. Cell-cell adhesion was disrupted in early-stage epithelial tumor cells (HaCaT-II-4) through expression of a dominant-negative form of E-cadherin (H-2Kd-Ecad). Three-dimensional human tissue constructs harboring either H-2Kd-Ecad-expressing or control II-4 cells (pBabe, H-2Kd-EcadDeltaC25) were cultured at an air-liquid interface for 8 days and transplanted to nude mice; tumor phenotype was analyzed 2 days and 2 and 4 weeks later. H-2Kd-Ecad-expressing tumors demonstrated a switch to a high-grade aggressive tumor phenotype characterized by poorly differentiated tumor cells that infiltrated throughout the stroma. This high-grade carcinoma revealed elevated cell proliferation in a random pattern, loss of keratin 1 and diffuse deposition of laminin 5 gamma2 chain. When II-4 cell variants were seeded into type I collagen gels as an in vitro assay for cell migration, we found that only E-cadherin-deficient cells detached, migrated as single cells and expressed N-cadherin. Function-blocking studies demonstrated that this migration was matrix metalloproteinase-dependent, as GM-6001 and TIMP-2, but not TIMP-1, could block migration. Gene expression profiles revealed that E-cadherin-deficient II-4 cells demonstrated increased expression of proteases and cell-cell and cell-matrix proteins. These findings showed that loss of E-cadherin-mediated adhesion plays a causal role in the transition from low- to high-grade squamous cell carcinomas and that the absence of E-cadherin is an important prognostic marker in the progression of this disease.

Animals↗
PubMed2006

Detection of activated, TIMP-free MMPs.

MMP inhibitor-tethered resins provide a method for detection of activated MMPs in tissues. These measurements will help to elucidate in situ mechanisms of MMP activation, further our understanding of the tumor microenvironment, and facilitate development of MMP-inhibitor therapy.

Enzyme Activation↗
PubMed2006

Regulated expression of TATA-binding protein-related factor 3 (TRF3) during early embryogenesis.

RNA polymerase (Pol) II transcription persists in TATA-box-binding protein (TBP)(-/-) mutant mouse embryos, indicating TBP-independent mechanisms for Pol II transcription in early development. TBP-related factor 3 (TRF3) has been proposed to substitute for TBP in TBP(-/-) mouse embryos. We examined the expression of TRF3 in maturing oocytes and early embryos and found that TRF3 was co-expressed with TBP in the meiotic oocytes and early embryos from the late one-cell stage onward. The amounts of TBP and TRF3 changed dynamically and correlated well with transcriptional activity. Chromatin immunoprecipitation (ChIP) assay revealed that different gene promoters in mouse embryonic stem (ES) cells recruited TRF3 and TBP selectively. Comparative analyses of TRF3 and TBP during cell cycle showed that both factors proceeded through cell cycle in a similar pace, except that TRF3 was slightly delayed than TBP in entering the nucleus when cells were exiting the M-phase. Data from expression and biochemical analyses therefore support the hypothesis that TRF3 plays a role in early mouse development. In addition, results from co-localization study suggest that TRF3 may be also involved in Pol I transcription.

Animals↗
PubMed2006

Continuous template collection and updating for electrogram morphology discrimination in implantable cardioverter defibrillators.

INTRODUCTION: Electrogram morphology analysis improves discrimination of supraventricular tachycardias (SVTs) from ventricular tachycardias (VTs) in implantable cardioverter defibrillators (ICDs), but electrogram morphology may change with lead maturation, drugs, or disease progression. We report the clinical performance of an automatic algorithm that creates and updates templates from non-paced, slow rhythm and continuously checks the quality of the template used for arrhythmia discrimination. METHODS AND RESULTS: We studied this algorithm in 193 patients with single-chamber ICDs (Marquis VR, Medtronic Inc., Minneapolis, MN, USA). Of the 112 patients who completed 6-month follow-up, 99.1% of the patients had > or =1 automatic template created. Match scores between template and ongoing rhythm are computed using Haar Wavelets. Of the 435 automatic templates evaluated at follow-up, 423 (97.2%) had a median match score > or =70%. Intrinsic rhythm at 1 month had significantly higher match scores (P < 0.001) with automatic templates (90.3 +/- 7.0%) than with manual templates (85.7 +/- 10.9%) generated at pre-hospital discharge (PHD). The percentage of appropriately rejected SVTs was slightly higher with the automatic template (280/339 episodes) than with the manual template at PHD (272/339 episodes) while the Wavelet detection of VT was the same (218/220 episodes). CONCLUSIONS: In patients receiving ICDs, the automatic templates were successfully created during a 6-month follow-up period, and consistently matched the patients' intrinsic rhythm at the nominal match threshold. Both early (<1 month postimplant) and late (1- to 3-month follow-up period) changes in electrogram morphology were identified, confirming the need for automatic template updating.

Algorithms↗
PubMed2006

Drug therapy of paroxysmal atrial fibrillation in the elderly over 75 years old.

OBJECTIVE: To investigate the effectiveness and safety of various agents on paroxysmal atrial fibrillation in the elderly over 75 years old. METHODS: Totally 264 in-patients (75-91 years old, 185 males and 79 females) with atrial fibrillation history of less than 7 days were enrolled in this study. A total of 611 atrial fibrillation episodes were recorded, but 130 episodes (22.3%) of atrial fibrillation were auto-converted to sinus rhythm. The rest 481 episodes of atrial fibrillation were divided into six groups based on the drug used. RESULTS: The cardioversion ratio of atrial fibrillation were 9.5%, 46.9%, 71.7%, 55.9%, 32.7%, and 73.6% in control, cedilanid, amiodarone, propafenone, verapamil, and quinidine groups, respectively. Ventricular rate control were 5.4%, 83.6%, 84.9%, 77.9%, 78.8%, and 11.3% in those groups, respectively. The total effective rates of amiodarone and cedilanid groups were the highest. When the ventricular rate was controlled to below 90 bpm, the patients would almost complain of no discomfort. No severe side-effect was observed in each group. CONCLUSION: Amiodarone and cedilanid may be the proper drugs for the treatment of paroxysmal atrial fibrillation in the elderly. The above antiarrhythmics in each therapeutic group were relatively safe and effective.

Aged↗
PubMed2006

[Value of ThinPrep bronchial brushing cytology in the diagnosis of lung cancers].

OBJECTIVE: To evaluate the ThinPrep bronchial brushing cytology in the diagnosis of lung cancers. METHODS: The smear slides of ThinPrep bronchial brushing cytology in 1000 patients collected from April 2001 to April 2002 were reviewed. RESULTS: Of 389 patients diagnosed as having lung cancer clinically or histopathologically, 273 (70.2%) were revealed by ThinPrep bronchial brushing cytology. Among the 74 patients with benign lung diseases comfirmed by pathology, 3 had been suspected as having lung cancer by ThinPrep bronchial brushing cytology. Actually, they were two patients suffering from tuberculosis and one hamartoma proven by histopathology later. The sensitivity and specificity of ThinPrep bronchial brushing cytology were 70.2% and 95.9%, respectively. Of the 179 patients who had both cytological and histopathological results, the cytology and pathology concordance rate was 95.4% in squamous carcinoma, 87.0% in adenocarcinoma and 95.7% in small cell carcinoma. CONCLUSION: Although ThinPrep bronchial brushing cytology has a high specificity, it is not good in diagnosing lung cancer. Poor smearing technique may be responsible for most of the false negative. Type diagnosis of poorly differentiated carcinomas can be difficult when based on the ThinPrep bronchial brushing cytology alone.

Adenocarcinoma↗
PubMed2005

Inhibition of enzyme activity of and cell-mediated substrate cleavage by membrane type 1 matrix metalloproteinase by newly developed mercaptosulphide inhibitors.

MT1-MMP (membrane type 1 matrix metalloproteinase, or MMP-14) is a key enzyme in molecular carcinogenesis, tumour-cell growth, invasion and angiogenesis. Novel and potent MMP inhibitors with a mercaptosulphide zinc-binding functionality have been designed and synthesized, and tested against human MT1-MMP and other MMPs. Binding to the MT1-MMP active site was verified by the competitive-inhibition mechanism and stereochemical requirements. MT1-MMP preferred deep P1' substituents, such as homophenylalanine instead of phenylalanine. Novel inhibitors with a non-prime phthalimido substituent had K(i) values in the low-nanomolar range; the most potent of these inhibitors was tested and found to be stable against air-oxidation in calf serum for at least 2 days. To illustrate the molecular interactions of the inhibitor-enzyme complex, theoretical docking of the inhibitors into the active site of MT1-MMP and molecular minimization of the complex were performed. In addition to maintaining the substrate-specificity pocket (S1' site) van der Waals interactions, the P1' position side chain may be critical for the peptide-backbone hydrogen-bonding network. To test the inhibition of cell-mediated substrate cleavage, two human cancer-cell culture models were used. Two of the most potent inhibitors tested reached the target enzyme and effectively inhibited activation of proMMP-2 by endogenous MT1-MMP produced by HT1080 human fibrosarcoma cells, and blocked fibronectin degradation by prostate cancer LNCaP cells stably transfected with MT1-MMP. These results provide a model for mercaptosulphide inhibitor binding to MT1-MMP that may aid in the design of more potent and selective inhibitors for MT1-MMP.

Binding, Competitive↗
PubMed2005

The 3D-QSAR analysis of 4(3H)-quinazolinone derivatives with dithiocarbamate side chains on thymidylate synthase.

Thymidylate synthase (TS) is a critical enzyme for DNA biosynthesis and many nonclassical lipophilic antifolates targeting this enzyme are quite efficient and encouraging as antitumor drug. In this paper, the binding model of 14 antifolates of 4(3H)-quinazolinone derivatives with dithiocarbamate side chains was examined using molecular simulation methods--FlexiDock and SCORE2.0. The resulted conformation and orientation of these antifolates were directly applied to CoMFA study. A good correlation between the calculated binding energies of these antifolates complexed with TS and their inhibitory activities was derived. The robust QSAR model, its three-dimensional contour map, and binding score for these antifolates derived from SCORE2.0 provided guidelines for structural optimization of current antifolates.

Computer Simulation↗
PubMed2005

Wolbachia utilizes host microtubules and Dynein for anterior localization in the Drosophila oocyte.

To investigate the role of the host cytoskeleton in the maternal transmission of the endoparasitic bacteria Wolbachia, we have characterized their distribution in the female germ line of Drosophila melanogaster. In the germarium, Wolbachia are distributed to all germ cells of the cyst, establishing an early infection in the cell destined to become the oocyte. During mid-oogenesis, Wolbachia exhibit a distinct concentration between the anterior cortex and the nucleus in the oocyte, where many bacteria appear to contact the nuclear envelope. Following programmed rearrangement of the microtubule network, Wolbachia dissociate from this anterior position and become dispersed throughout the oocyte. This localization pattern is distinct from mitochondria and all known axis determinants. Manipulation of microtubules and cytoplasmic Dynein and Dynactin, but not Kinesin-1, disrupts anterior bacterial localization in the oocyte. In live egg chambers, Wolbachia exhibit movement in nurse cells but not in the oocyte, suggesting that the bacteria are anchored by host factors. In addition, we identify mid-oogenesis as a period in the life cycle of Wolbachia in which bacterial replication occurs. Total bacterial counts show that Wolbachia increase at a significantly higher rate in the oocyte than in the average nurse cell, and that normal Wolbachia levels in the oocyte depend on microtubules. These findings demonstrate that Wolbachia utilize the host microtubule network and associated proteins for their subcellular localization in the Drosophila oocyte. These interactions may also play a role in bacterial motility and replication, ultimately leading to the bacteria's efficient maternal transmission.

Animals↗
PubMed2005

Cyclic mechanical strain-induced proliferation and migration of human airway smooth muscle cells: role of EMMPRIN and MMPs.

Airway smooth muscle (ASM) proliferation and migration are major components of airway remodeling in asthma. Asthmatic airways are exposed to mechanical strain, which contributes to their remodeling. Matrix metalloproteinase (MMP) plays an important role in remodeling. In the present study, we examined if the mechanical strain of human ASM (HASM) cells contributes to their proliferation and migration and the role of MMPs in this process. HASM were exposed to mechanical strain using the FlexCell system. HASM cell proliferation, migration and MMP release, activation, and expression were assessed. Our results show that cyclic strain increased the proliferation and migration of HASM; cyclic strain increased release and activation of MMP-1, -2, and -3 and membrane type 1-MMP; MMP release was preceded by an increase in extracellular MMP inducer; Prinomastat [a MMP inhibitor (MMPI)] significantly decreased cyclic strain-induced proliferation and migration of HASM; and the strain-induced increase in the release of MMPs was accompanied by an increase in tenascin-C release. In conclusion, cyclic mechanical strain plays an important role in HASM cell proliferation and migration. This increase in proliferation and migration is through an increase in MMP release and activation. Pharmacological MMPIs should be considered in the pursuit of therapeutic options for airway remodeling in asthma.

Asthma↗
PubMed2005

Furin directly cleaves proMMP-2 in the trans-Golgi network resulting in a nonfunctioning proteinase.

Proprotein convertases play an important role in tumorigenesis and invasiveness. Here, we report that a dibasic amino acid convertase, furin, directly cleaves proMMP-2 within the trans-Golgi network leading to an inactive form of matrix metalloproteinase-2 (MMP-2). Co-transfection of COS-1 cells with both proMMP-2 and furin cDNAs resulted in the cleavage of the N-terminal propeptide of proMMP-2. The molecular mass of cleaved MMP-2 (63 kDa), detected in both cell lysates and conditioned medium, is between the intermediate and fully activated forms of MMP-2 induced by membrane type 1-MMP. Furin-cleaved MMP-2 does not possess proteolytic activity as examined in a cell-free assay. Treatment of transfected cells with a furin inhibitor resulted in a dose-dependent inhibition of proMMP-2 cleavage; recombinant tissue inhibitor of metalloproteinase-2, which binds to the active site of membrane type 1-MMP, had no inhibitory effect. Site-directed mutagenesis of amino acids in the furin consensus recognition motif of proMMP-2(R69KPR72) prevented propeptide cleavage, thereby identifying the scissile bond and characterizing the basic amino acids required for cleavage. Other experimental observations were consistent with intracellular furin cleavage of proMMP-2 in the trans-Golgi network. The furin cleavage site in other proMMPs was examined. MMP-3, which contains the RXXR furin consensus sequence, was cleaved in furin co-transfected cells, whereas MMP-1, which lacks an RXXR consensus sequence, was not cleaved. In conclusion, we report the novel observation that furin can directly cleave the RXXR amino acid sequence in the propeptide domain of proMMP-2 leading to inactivation of the enzyme.

Amino Acid Sequence↗
PubMed2005

The organomercurial 4-aminophenylmercuric acetate, independent of matrix metalloproteinases, induces dose-dependent activation/inhibition of platelet aggregation.

Matrix metalloproteinases (MMPs) play an important role in many biological and pathological processes including tissue remodeling, wound healing, inflammation, atherosclerosis, and cancer. Numerous publications have supported the concept that activated MMP-2 enhances agonist-induced platelet aggregation and activated MMP-9 inhibits platelet aggregation. In this study, we demonstrated that the organomercurial compound, 4-aminophenyl mercuric acetate (APMA), which is routinely employed to activate latent MMPs at a concentration of 1000 microM, induces platelet aggregation at low concentration (5 microM) and inhibits agonist-induced platelet aggregation at concentrations >or= 50 microM. Activated MMP-2, MMP-1, and MMP-9, following removal of APMA by ultrafiltration through an anisotropic membrane, exert no independent effect on platelet aggregation. Acetylsalicylic acid and BAPTA inhibited APMA-induced platelet aggregation indicating that the APMA mediated pathway of platelet activation is dependent upon thromboxane and calcium signaling. Zinc chelation with 1,10-phenanthroline, which inhibits zinc-dependent proteins including metalloproteinases, also abrogated platelet functional responses to APMA. Additional studies will be required to clarify the mechanism of the biphasic effect of APMA on platelet aggregation.

Calcium Signaling↗
PubMed2005

Membrane type 1-matrix metalloproteinase promotes human prostate cancer invasion and metastasis.

Development of metastases requires cancer cells to breach underlying basement membrane, migrate through interstitial stroma and gain access to blood or lymphatic vessels. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been linked with these processes. Expression of MT1-MMP in human prostate cancer correlates with the stage of this disseminated disease. The mechanism underlying this observation, however, still remains to be understood. To study the role of MT1-MMP in prostate cancer dissemination, endogenous and recombinant MT1-MMP expressed in human prostate cancer cell lines (DU-145 and LNCaP) were examined. Using FITC-labeled Matrigel, a soluble basement membrane extract coated coverslips, LNCaP cells stably expressing a chimera of MT1-MMP and Green Fluorescent Protein (MT1-GFP) degraded Matrigel and readily migrated over degraded substrates. The degradation of Matrigel by LNCaP cells expressing MT1-GFP was sensitive to MMP inhibitors, CT-1746 and TIMP-2, but not TIMP-1. Cell migration was dramatically enhanced by expression of MT1-MMP. By employing surgical orthotopic implantation of LNCaP cells stably expressing MT1-GFP into the prostate gland of immunodeficient mice, we demonstrated that MT1-MMP promotes lymph node and lung metastasis of prostate cancer cells. Together, these results emphasize the pivotal role of MT1-MMP in prostate cancer dissemination and confirm that MT1-MMP is a suitable target to prevent cancer metastasis.

Animals↗
PubMed2005

[Inducement effect of (DIPP-L-Trp)2-L-Lys-OCH3 on apoptosis of K562 cells through mitochondrial-dependent pathway].

BACKGROUND & OBJECTIVE: Phosphorylation of protein and peptide plays an important role in life activity. Some phosphoryl peptides are found to have activities to inhibit proliferation of tumor cells, but the involved mechanisms are unclear. This study was designed to investigate cell apoptosis induced by (O,O-diisopropyl phosphoryl-L-tryptophan)(2)-L-lysine methyl ester [(DIPP-L-Trp)(2)-L-Lys-OCH(3)], and its mechanism in K562 cells. METHODS: K562 cells were double stained by AnnexinV-FITC and propidium iodide (PI) to detect (DIPP-L-Trp)(2)-L-Lys-OCH(3)-induced apoptosis by flow cytometry (FCM). After treatment of different concentrations of (DIPP-L-Trp)(2)-L-Lys-OCH(3), K562 cells were stained by rhodamine123 and PI to detect changes in membrane potential (Delta Psi m), or stained by 2',7'-dichlorofluorescein diacetate (DCFH-DA) to detect reactive oxygen species (ROS) of mitochondrial by FCM. RESULTS: When treated with 50 microg/ml of (DIPP-L-Trp)(2)-L-Lys-OCH(3) for 24 h, apoptosis rate of K562 cells was 61.9%, Delta Psi m was decreased in 93.6% of K562 cells,and ROS production was decreased. Both Delta Psi m and ROS production in K562 cells mitochondria were decreased with the increasing concentration and extending treatment time of (DIPP-L-Trp)(2)-L-Lys-OCH(3). CONCLUSION: (DIPP-L-Trp) (2)-L-Lys-OCH(2) could induce apoptosis in K562 cells, which might relate with down-regulation of mitochondrial Delta Psi m and reduction of ROS production.

Apoptosis↗