Biomedical subjects

Zhuo Zhang

Publications and source records attributed to Zhuo Zhang.

At least 37 records · Page 2Linked to original sources

PubMed2005

Oncogenes as novel targets for cancer therapy (part IV): regulators of the cell cycle and apoptosis.

This is the final part of a four-part serial review on oncogenes and their potential use as targets for cancer therapy. Previous sections discussed various categories of oncogenes (growth factors, tyrosine kinases, intermediate signaling molecules, and transcription factors) and the advances made in various strategies being used to alter their actions. This part describes four oncogenes, MDM2, BCL2, XIAP, and Survivin, that are involved in regulation of the cell cycle and apoptosis.

Animals↗

PubMed2005

p53-independent activities of MDM2 and their relevance to cancer therapy.

The feed-back auto-regulatory loop between p53 and MDM2 has been extensively investigated. MDM2 is under the transcriptional control of p53, and MDM2 acts as a negative regulator of p53. There is increasing evidence, however, supporting the notion that MDM2 has activities independent of p53. In the absence of p53, MDM2 may retain its role in cell cycle control, differentiation, cell fate determination, DNA repair, transcription regulation, signal transduction of steroid receptors, cellular response to hypoxia, internalization of surface receptors, and other processes. MDM2 also has oncogenic transformational activities independent of p53. Moreover, anti-MDM2 antisense oligonucleotides have in vitro and in vivo antitumor activity and chemosensitizing and radiosensitizing effects in several human cancer models, regardless of their p53 status. In this article, the p53 independent activities of MDM2 and its interactions with various cellular proteins are considered. The studies reviewed provide a basis for developing novel MDM2 inhibitors as a therapy against human malignancies.

Animals↗

PubMed2005

[Distribution and change of NGF, BDNF and NT3 in the hippocampus of rat with AD].

OBJECTIVE: To investigate the distribution and change of NGF, BDNF and NT3 in hippocampus of rat with Alzheimer disease(AD) by immunohistochemistry. METHODS: AD model was established by injecting beta amyloid protein into the hippocampus of rat. The rats were killed ten days after injection. The hippocampus sections were made coronally on a freezing microtome. Brain sections were processed by immunohistochemical procedure with molocloned antibodies against NGF, BDNF and NT3. The number of positive neurons of NGF, BDNF and NT3 was counted and analyzed statistically. RESULTS: It was found that the number of NGF positive neurons increased and the immunostaining intensity became stronger as compared with the control (P<0.01). The number of BDNF positive neurons decreased and the immunostaining intensity weakened (P<0.01). There Our was no change in the number and immunostaining intensity of NT3 positive neurons (P>0.05). CONCLUSION: results show that NGF, BDNF, NT3 have experienced different changes in hippocampus of rat with AD, suggesting that they play different roles in the course of AD and bear relation to the physiological function of cholinergic neurons in hippocampus of rat with AD. In particular, BDNF exerts crucial effect on the degeneration of neuronal function in the hippocampus of rat with AD.

Alzheimer Disease↗

PubMed2004

Combination therapy for adult T-cell leukemia-xenografted mice: flavopiridol and anti-CD25 monoclonal antibody.

Adult T-cell leukemia (ATL) develops in a small proportion of individuals infected with human T-cell lymphotrophic virus-1. The leukemia consists of an overabundance of activated T cells, which express CD25 on their cell surfaces. Presently, there is no accepted curative therapy for ATL. Flavopiridol, an inhibitor of cyclin-dependent kinases, has potent antiproliferative effects and antitumor activity. We investigated the therapeutic efficacy of flavopiridol alone and in combination with humanized anti-Tac antibody (HAT), which recognizes CD25, in a murine model of human ATL. The ATL model was established by intraperitoneal injection of MET-1 leukemic cells into nonobese diabetic/severe combined immunodeficient mice. Either flavopiridol, given 2.5 mg/kg body weight daily for 5 days, or HAT, given 100 microg weekly for 4 weeks, inhibited tumor growth as monitored by serum levels of human beta-2-microglobulin (beta2mu; P < .01), and prolonged survival of the leukemia-bearing mice (P < .05) as compared with the control group. Combination of the 2 agents dramatically enhanced the antitumor effect, as shown by both beta2mu levels and survival of the mice, when compared with those in the flavopiridol or HAT alone group (P < .01). The significantly improved therapeutic efficacy by combining flavopiridol with HAT provides support for a clinical trial in the treatment of ATL.

Adult↗

PubMed2004

Activating Fc receptors are required for antitumor efficacy of the antibodies directed toward CD25 in a murine model of adult t-cell leukemia.

We previously showed therapeutic efficacy of humanized anti-Tac (HAT), murine anti-Tac (MAT), and 7G7/B6 monoclonal antibodies, which recognize CD25, for human adult T-cell leukemia (ATL) in a murine model. In this study, we investigated the mechanism underlying the tumor-killing action mediated by these antibodies on an ATL model in nonobese diabetic/severe combined immunodeficient (SCID/NOD) wild-type mice that lack effective T and natural killer (NK) cells and in SCID/NOD Fc receptor common gamma chain knockout (FcRgamma-/-) mice. The ATL model was established by i.p. injection of human ATL cells (MET-1) into SCID/NOD wild-type or SCID/NOD FcRgamma-/- mice. HAT, MAT, and 7G7/B6 were given to the leukemia-bearing mice at a dose of 100 microg weekly for 4 weeks. The three antibodies inhibited the leukemia growth significantly in SCID/NOD wild-type mice, as monitored by serum levels of human beta2-microglobulin (P < 0.01), and prolonged survival of the leukemia-bearing SCID/NOD wild-type mice (P < 0.01) as compared with the control group. However, none of the antibodies manifested efficacy on the leukemia growth and survival of the SCID/NOD FcRgamma-/- mice bearing MET-1 leukemia. In a pharmacokinetics study, the blood concentrations of the radiolabeled antibodies decreased with time similarly in SCID/NOD wild-type and SCID/NOD FcRgamma-/- mice. Although NK cells may play a role in humans, in this murine model FcRgamma receptors on non-NK cells, such as polymorphonuclear leukocytes or monocytes, are required for the tumor-killing action of the antibodies directed toward CD25.

Animals↗

PubMed2004

[NOTCH3 gene mutations in four Chinese families with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy].

OBJECTIVES: To search for mutations in NOTCH3 gene in four Chinese families with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). METHODS: Four probands from four unrelated families with typical manifestations of CADASIL were studied. The 1 approximately 12 coding exons and their flanking intron sequences of NOTCH3 gene were amplified by PCR and sequenced. Some family members in the pedigree 2 and 4 were also examined for the NOTCH3 gene mutations. RESULTS: Four heterozygous missense mutations were identified in the four families: the proband 1 carrying a 268C-->T mutation in exon 3, the proband 2 a 322 C-->T mutation in exon 3, the proband 3 a 328 C-->T mutation inexon 3, and the proband 4 a 1819 C-->T mutation in exon 11, which resulted in the amino acid substitutions of R90C, C108R, R110C, and R607C respectively. Among them the C108R is a novel mutation not reported previously. Additionally, some members in the pedigree 2 and 4 also harbored the same mutations with the probands. CONCLUSION: Four heterozygous missense mutations in NOTCH3 gene have been found in four Chinese families with CADASIL. Different point mutations in NOTCH3 lead to similar phenotype of the disease. To search for mutations in NOTCH3 in related patients will help further understand and accurately diagnose the disease and perform prenatal diagnosis in CADASIL families.

Adult↗

PubMed2004

InterWeaver: interaction reports for discovering potential protein interaction partners with online evidence.

InterWeaver is a web server for discovering potential protein interactions with online evidence automatically extracted from protein interaction databases, literature abstracts, domain fusion events and domain interactions. Given a new protein sequence, the server identifies potential interaction partners using two approaches. In the homology-based approach, the system performs sequence homology searches to find similar proteins in other species, and then searches the protein interaction databases and the biomedical literature for interaction partners. In the domain-based approach, the system detects the domains in the input protein sequence and searches databases of domain fusion events and putative domain interactions to suggest potential interacting partners. The results are compiled into a personalized and downloadable interaction report to aid biologists in their discovery of protein interactions. InterWeaver is freely available for academic users at http://interweaver.i2r.a-star.edu.sg/.

Computational Biology↗

PubMed2004

ADVICE: Automated Detection and Validation of Interaction by Co-Evolution.

ADVICE (Automated Detection and Validation of Interaction by Co-Evolution) is a web tool for predicting and validating protein-protein interactions using the observed co-evolution between interacting proteins. Interacting proteins are known to share similar evolutionary histories since they undergo coordinated evolutionary changes to preserve interactions and functionalities. The web tool automates a commonly adopted methodology to quantify the similarities in proteins' evolutionary histories for postulating potential protein-protein interactions. ADVICE can also be used to validate experimental data against spurious protein interactions by identifying those that have few similarities in their evolutionary histories. The web tool accepts a list of protein sequences or sequence pairs as input and retrieves orthologous sequences to compute the similarities in the proteins' evolutionary histories. To facilitate hypothesis generation, detected co-evolved proteins can be visualized as a network at the website. ADVICE is available at http://advice.i2r.a-star.edu.sg.

Evolution, Molecular↗

PubMed2004

Dragon TF Association Miner: a system for exploring transcription factor associations through text-mining.

We present Dragon TF Association Miner (DTFAM), a system for text-mining of PubMed documents for potential functional association of transcription factors (TFs) with terms from Gene Ontology (GO) and with diseases. DTFAM has been trained and tested in the selection of relevant documents on a manually curated dataset containing >3000 PubMed abstracts relevant to transcription control. On our test data the system achieves sensitivity of 80% with specificity of 82%. DTFAM provides comprehensive tabular and graphical reports linking terms to relevant sets of documents. These documents are color-coded for easier inspection. DTFAM complements the existing biological resources by collecting, assessing, extracting and presenting associations that can reveal some of the not so easily observable connections among the entities found which could explain the functions of TFs and help decipher parts of gene transcriptional regulatory networks. DTFAM summarizes information from a large volume of documents saving time and making analysis simpler for individual users. DTFAM is freely available for academic and non-profit users at http://research.i2r.a-star.edu.sg/DRAGON/TFAM/.

Gene Expression Regulation↗

PubMed2004

G1 cell cycle progression and the expression of G1 cyclins are regulated by PI3K/AKT/mTOR/p70S6K1 signaling in human ovarian cancer cells.

Ovarian cancer is one of the most common cancers among women. Recent studies demonstrated that the gene encoding the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K) is frequently amplified in ovarian cancer cells. PI3K is involved in multiple cellular functions, including proliferation, differentiation, antiapoptosis, tumorigenesis, and angiogenesis. In this study, we demonstrate that the inhibition of PI3K activity by LY-294002 inhibited ovarian cancer cell proliferation and induced G(1) cell cycle arrest. This effect was accompanied by the decreased expression of G(1)-associated proteins, including cyclin D1, cyclin-dependent kinase (CDK) 4, CDC25A, and retinoblastoma phosphorylation at Ser(780), Ser(795), and Ser(807/811). Expression of CDK6 and beta-actin was not affected by LY-294002. Expression of the cyclin kinase inhibitor p16(INK4a) was induced by the PI3K inhibitor, whereas steady-state levels of p21(CIP1/WAF1) were decreased in the same experiment. The inhibition of PI3K activity also inhibited the phosphorylation of AKT and p70S6K1, but not extracellular regulated kinase 1/2. The G(1) cell cycle arrest induced by LY-294002 was restored by the expression of active forms of AKT and p70S6K1 in the cells. Our study shows that PI3K transmits a mitogenic signal through AKT and mammalian target of rapamycin (mTOR) to p70S6K1. The mTOR inhibitor rapamycin had similar inhibitory effects on G(1) cell cycle progression and on the expression of cyclin D1, CDK4, CDC25A, and retinoblastoma phosphorylation. These results indicate that PI3K mediates G(1) progression and cyclin expression through activation of an AKT/mTOR/p70S6K1 signaling pathway in the ovarian cancer cells.

Antibiotics, Antineoplastic↗

PubMed2004

Radiosensitization by antisense anti-MDM2 mixed-backbone oligonucleotide in in vitro and in vivo human cancer models.

PURPOSE: The MDM2 oncogene, amplified or overexpressed in many human cancers, has been suggested to be a novel target for cancer therapy. We have demonstrated a second-generation antisense antihuman-MDM2 oligonucleotide to have antitumor activity when administered alone or in combination with cancer chemotherapeutic agents. In the present study, we investigated the effect of the antisense oligonucleotide on radiation therapy. EXPERIMENTAL DESIGN: The in vitro radiosensitization activity was determined in cell lines of human cancers of prostate (LNCaP and PC3), breast (MCF-7 and MDA-MB-468), pancreas (PANC-1), and glioma (U87-MG and A172) and its in vivo radiosensitization activity in xenograft models of LNCaP, PC3, MCF-7, MDA-MB-468, and PANC-1. RESULTS: In cells containing at least one functional p53 allele (LNCaP, U87-MG, and A172), after specific inhibition of MDM2 expression, p53 and p21 levels were elevated. In LNCaP cells, the Bax level was increased, and Bcl-2 and E2F1 levels were decreased. In PC3 cells that are p53 null, after inhibition of MDM2 expression, Bax and p21 levels were elevated, and E2F1 levels were decreased. On the basis of in vitro clonogenic assay, the antisense oligonucleotide, in a sequence-specific manner, significantly increased radiation-induced antiproliferation effects. It also increased radiation-induced inhibitory effects on tumor growth in SCID or nude mice bearing LNCaP, PC3, MCF-7, MDA-MB-468, and PANC-1 xenografts. CONCLUSIONS: These results suggest that MDM2 has a role in radiation therapy of human cancers, regardless of p53 status, providing a basis for future development of MDM2 inhibitors, such as antisense oligonucleotides, as radiosensitizers.

Alleles↗

PubMed2004

MDM2 is a negative regulator of p21WAF1/CIP1, independent of p53.

The MDM2 oncogene has both p53-dependent and p53-independent activities. We have previously reported that antisense MDM2 inhibitors have significant anti-tumor activity in multiple human cancer models with various p53 statuses (Zhang, Z., Li, M., Wang, H., Agrawal, S., and Zhang, R. (2003) Proc. Natl. Acad. Sci. U. S. A. 100, 11636-11641). We have also provided evidence that MDM2 has a direct role in the regulation of p21, a cyclin-dependent kinase inhibitor. Here we provide evidence supporting functional interaction between MDM2 and p21 in vitro and in vivo. The inhibition of MDM2 with anti-MDM2 antisense oligonucleotide or Short Interference RNA targeting MDM2 significantly elevated p21 protein levels in PC3 cells (p53 null). In contrast, overexpression of MDM2 diminished the p21 level in the same cells by shortening the p21 half-life, an effect reversed by MDM2 antisense inhibition. MDM2 facilitates p21 degradation independent of ubiquitination and the E3 ligase function of MDM2. Instead, MDM2 promotes p21 degradation by facilitating binding of p21 with the proteasomal C8 subunit. The physical interaction between p21 and MDM2 was demonstrated both in vitro and in vivo with the binding region in amino acids 180-298 of the MDM2 protein. In summary, we provide evidence supporting a physical interaction between MDM2 and p21. We also demonstrate that, by reducing p21 protein stability via proteasome-mediated degradation, MDM2 functions as a negative regulator of p21, an effect independent of both p53 and ubiquitination.

Cell Line↗

PubMed2004

Twelve C2H2 zinc-finger genes on human chromosome 19 can be each translated into the same type of protein after frameshifts.

We report a discovery that, of the 226 C2H2 zinc-finger (C2H2-ZNF) genes on human chromosome 19, 12 genes each have two open reading frames (ORFs) that are in different reading frames but that can be translated into the same type of C2H2-ZNF proteins. We came to this observation after using standard tools in an original manner. First, we found that the both ORFs of such a gene contained the same type of significant C2H2-ZNF domain with e-values of e-2 or better. Second, the both ORFs had a promoter, a transcription start site, a start codon, a Kozak pattern and a poly(A) site; hence, each of them can be viewed as a gene in terms of a gene's primary structure. Third, both the ORFs matched not only human C2H2-ZNF expressed sequence tags (ESTs) but also human C2H2-ZNF proteins with e-values of e-50 or better. This indicates that the both ORFs can be transcribed and translated into the same zinc-finger proteins. More importantly, we observed that the phenomenon-a DNA can be translated into the same type of proteins after a frameshift-also occurred in a set of 160 human C2H2-ZNF ESTs and in a set of nine cDNAs of human C2H2-ZNF proteins. This observation based on the two sets of wet-experimental data much strengthened our confidence on the discovery. Our discovery is useful in the deeper understanding of a gene's regulatory mechanism to maintain its function.

Base Sequence↗

PubMed2004

Intracellular angiotensin II fusion protein alters AT1 receptor fusion protein distribution and activates CREB.

In recently published studies, we show that angiotensin II (AII) generated from an engineered rat angiotensinogen cDNA, and maintained intracellularly, is growth stimulatory for a rat hepatoma cell line. In the present study, we report that co-expression of AII fused to cyan fluorescent protein (ECFP/AII) and angiotensin type I receptor fused to yellow fluorescent protein (AT1R/EYFP) enhances proliferation of COS-7 and CHO-K1 cells by 59% and 64%, respectively, compared to cells expressing the corresponding independent proteins (P < 0.001 for both). This effect is inhibited by losartan, suggesting (as in our previous published studies) that losartan is internalized by the cells, via receptor-mediated endocytosis, and thus inhibits intracellular receptor-ligand interaction. The growth effect is independent of anti-AII antibodies suggesting that it does not reflect AII secretion into the culture media; AII is also undetectable in the media. Expression of AT1R/EYFP with ECFP/AIIC (control scrambled sequence AII fused to ECFP) has no effect upon cell proliferation. ECFP/AII also alters the cellular localization of AT1R/EYFP. ECFP/AII is concentrated in the nucleus, but shows diffuse cytoplasmic fluorescence as well. AT1R/EYFP, expressed independently, is visible in the endoplasmic reticulum and Golgi apparatus of COS-7 and CHO-K1 cells as early as 24-h post-transfection. At 72 h, it is visibly associated with the plasma membrane. By 144 h, 85% of the cells show detectable circumferential fluorescence. In contrast, in cells that express AT1R/EYFP and ECFP/AII, both proteins accumulate in the nucleus and only 13% of the cells show visible plasma membrane-associated yellow fluorescence at 144 h (P < 0.001). Furthermore, co-expression of ECFP/AII with AT1R/EYFP stimulates cAMP response element-binding protein (CREB) activity in CHO-K1 and COS-7 cells. Exogenous AII similarly significantly increases CREB activation in AT1R/EYFP-stably transfected CHO-K1 and COS-7 cells.

Amino Acid Sequence↗

PubMed2004

Arsenite induces HIF-1alpha and VEGF through PI3K, Akt and reactive oxygen species in DU145 human prostate carcinoma cells.

Arsenite is widely distributed environmental toxicant in water, food and air. It is a known human carcinogen, which is strongly associated with human cancers originated from liver, nasal cavity, lung, skin, bladder, kidney, and prostate. In this study, we investigated whether arsenite induces expression of hypoxia-inducible factor 1 (HIF-1). HIF-1 is a heterodimeric basic helix-loop-helix transcription factor, composed of HIF-1alpha and HIF-1beta/ARNT subunits; and is involved in tumor growth and angiogenesis. Here we demonstrate that arsenite induces the expression of HIF-1alpha but not HIF-1beta subunit in DU145 human prostate carcinoma cells. Arsenite also increases the expression of VEGF through the induction of HIF-1. We also found that arsenite activates PI3K and Akt that are required for arsenite-induced expression of HIF-1alpha and VEGF. The induction of HIF-1 and VEGF by arsenite can not be inhibited by MAP kinase inhibitors. Arsenite causes production of reactive oxygen species (ROS). The major species of ROS required for the induction of HIF-1 and VEGF is H2O2. These data indicate that the arsenite-induced activation of PI3K/Akt signaling and the expression of HIF-1 and VEGF through the generation of ROS could be an important mechanism in the arsenite-induced carcinogenesis.

Androstadienes↗

PubMed2004

NF-kappaB prevents cells from undergoing Cr(VI)-induced apoptosis.

The transcription factor NF-kappaB has been reported to prevent cells from undergoing apoptosis as well as promote cell apoptosis. To investigate the role of NF-kappaB in Cr(VI)-induced apoptosis, two cell lines were developed from human bronchial epithelial BEAS-2B cells: IKK cells, which were stably transfected with IkappaBalpha expression vector, that have normal NF-kappaB activity, and KM cells, which were stably transfected with mutated IkappaBalpha kinase expression vector, that exhibit very little NF-kappaB activity. With Cr(VI) stimulation, KM cells, but not IKK cells, exhibited substantial cell death. Cell morphological and TUNEL analyses indicated that the KM cells showed apoptotic features. These results suggest that NF-kappaB activation is required to prevent the cells from undergoing Cr(VI)-induced apoptosis.

Apoptosis↗

PubMed2004

Vanadate activated Akt and promoted S phase entry.

Protein kinase B (PKB)/Akt and its upstream signal transducer, phosphatidylinosito-3 kinase (PI3K) play an essential role in control of transcription and translation, which impact cell growth, survival, and metabolism. Transcription factor E2F is a component of the downstream proliferative machinery regulated by Akt. Hyperphosphorylation of retinoblastoma protein (pRb), a pocket protein, leads to release of E2F1, resulting in transition from G1 to S phase. The present study shows that in normal C141 cells, vanadate treatment increased the percentage of cells at S phase and elevated cyclin E and cyclin A expression. Vanadate treatment triggered phosphorylation of pRb and release of E2F1. Furthermore, vanadate increased Akt kinase activity and caused its phosphorylation at Ser473 and Thr308. Inhibition of Akt by either inhibitors or transfected cells with dominant negative kinase mutant or dominant negative phosphorylation mutant decreased the percentage of the cells at the S phase induced by vanadate, and reduced both cyclin E and E2F1 expression and phosphorylation of pRb. The present study indicates that Akt plays an essential role in vanadate-induced increase in cell number at S phase and transition from G1 to S phase through E2F-pRb pathway.

Animals↗

PubMed2004

The role of phosphatidylinositol-3 kinase in vanadate-promoted S phase entry.

Phosphatidylinositil-3 kinase (PI3K) is a heterodimer of catalytic and regulatory subunits. It is involved in various signaling pathways and key functions of the cells. The present study investigated the role of PI3K in vanadate-induced alteration in cell cycle regulation in C141 mouse epidermal cells. Vanadate caused a time- and dose-dependent increase in PI3K activity and phosphorylation of p70 S6 kinase (p70S6K) at Thr421/Ser424 and Thr389 sites. The phosphorylation at these sites was inhibited by PI3K inhibitor, LY294002, and p70S6K mutation. Vanadate promoted S phase entry and this promotion was inhibited by LY294002 and rapmycin, a p70S6K inhibitor. Vanadate-induced enhancement in S phase entry was also inhibited in transfection with dominant negative p70S6K mutant cells. The results obtained show that vanadate is able to increase PI3K activity through phosphorylation. PI3K activated p70S6K, which phosphated protein S6, and promoted S phase entry.

Animals↗