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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 559 records · Page 31Linked to original sources

Studies on treatment of acute promyelocytic leukemia with arsenic trioxide: remission induction, follow-up, and molecular monitoring in 11 newly diagnosed and 47 relapsed acute promyelocytic leukemia patients.

Fifty-eight acute promyelocytic leukemia (APL) patients (11 newly diagnosed and 47 relapsed) were studied for arsenic trioxide (As2O3) treatment. Clinical complete remission (CR) was obtained in 8 of 11 (72.7%) newly diagnosed cases. However, As2O3 treatment resulted in hepatic toxicity in 7 cases including 2 deaths, in contrast to the mild liver dysfunction in one third of the relapsed patients. Forty of forty-seven (85.1%) relapsed patients achieved CR. Two of three nonresponders showed clonal evolution at relapse, with disappearance of t(15;17) and PML-RARalpha fusion gene in 1 and shift to a dominant AML-1-ETO population in another, suggesting a correlation between PML-RARalpha expression and therapeutic response. In a follow-up of 33 relapsed cases over 7 to 48 months, the estimated disease-free survival (DFS) rates for 1 and 2 years were 63.6% and 41.6%, respectively, and the actual median DFS was 17 months. Patients with white blood cell (WBC) count below 10 x 10(9)/L at relapse had better survival than those with WBC count over 10 x 10(9)/L (P =.038). The duration of As2O3-induced CR was related to postremission therapy, because there was only 2 of 11 relapses in patients treated with As2O3 combined with chemotherapy, compared with 12 of 18 relapses with As2O3 alone (P =.01). Reverse transcription polymerase chain reaction (RT-PCR) analysis in both newly diagnosed and relapsed groups showed long-term use of As2O3 could lead to a molecular remission in some patients. We thus recommend that ATRA be used as first choice for remission induction in newly diagnosed APL cases, whereas As2O3 can be either used as a rescue for relapsed cases or included into multidrug consolidation/maintenance clinical trials.

Adult↗

A human IAP-family gene, apollon, expressed in human brain cancer cells.

IAP is a family of protein that has baculovirus IAP repeat (BIR) domains and inhibits apoptosis. We found a human IAP family gene, which we named Apollon, encoding a huge protein (530 kDa) that contains a single BIR domain and a ubiquitin-conjugating enzyme domain, that is a human homolog of BRUCE. Apollon protein was expressed in four of six brain cancers (gliomas), and one of five ovarian cancers in 38 human cancer cell lines that we examined. Among the brain cancer cell lines, SNB-78 expressed a high level of Apollon, and this cell line shows resistance against various anticancer drugs. Treating SNB-78 cells with antisense oligonucleotide against Apollon reduced the expression of Apollon protein, and significantly sensitized the cells to apoptosis induced by cisplatin and camptothecin. These results suggest that Apollon protects SNB-78 cells from undergoing apoptosis and, at least in part, plays a role in tumorigenesis and drug resistance of this cell line.

Amino Acid Sequence↗

Optimum timing for image-based dose evaluation of 125I and 103PD prostate seed implants.

PURPOSE/OBJECTIVE: Image-based dose evaluation of permanent brachytherapy implants for prostate cancer is important for optimal patient management after implantation. Because of edema caused by the surgical procedure in the implantation, if the dose evaluation is based on the images obtained too early after implantation, dose coverage will usually be underestimated. Conversely, if the images are obtained too late, the dose coverage will be overestimated. This study uses a biomathematical model to simulate edema and its resolution on 29 patients, so that the optimum time to obtain image scans and perform dose evaluation can be investigated and estimated. METHODS AND MATERIALS: Edema of a prostate and its resolution has been shown to follow an exponential function V(t) = V(0)(1 + deltaV[e-0.693t/Te - 1]) where deltaV is the initial relative increase in the prostate volume due to edema (and is related to edema magnitude), and Te (edema half-life) is the time for the edema to decrease by half in volume. In this study, edema was simulated by increasing the volume of preimplant prostate (obtained from ultrasound volume study) to a given magnitude of edema. Similarly, the locations of planned seeds were changed to their corresponding locations in the edematous prostate proportionally. The edema was then allowed to resolve according to the exponential function. The correct dose distribution was calculated by taking into account the dynamic variations of the prostate volume, seed locations, and source strengths with respect to time. Dose volume histograms (DVHs) were then generated from this dose distribution. The conventional postimplant DVHs, which assume the prostate volume and seed locations are as in the image scans and constant in time, were also calculated based on the simulated image scans for various days postimplantation. The conventional DVHs of prostate on various days after implantation were compared to the DVH calculated assuming dynamic conditions. The optimum timing for conventional postimplant dose evaluation was identified as the time at which a minimum difference between the conventional DVH and the dynamic model DVH was achieved. The analysis was done on 29 prostate seed implant patients for both 125I and 103Pd. The edema magnitude was assumed to be 30%, 40%, 50%, 75%, and 100% of original prostate volume, and the half-life of edema was assumed to be 4, 7, 10, 15, 20, and 25 days. In this study, the original volume of prostate varied from 17 cm3 to 91 cm3, and number of seeds in the implants varied from 57 to 119. RESULTS: The optimum timing was mainly dependent on the half-lives of edema and radionuclides, and varied slightly with edema magnitude, prostate volume, and number of seeds. It can be expressed as a function of edema half-life in the form of C0 + C1exp(-C2Te). However, if the dose evaluation was performed based on the image scans taken too early or too late, the error became larger, as the edema magnitude was larger. By averaging all 29 patients and various edemas, it was found that for 125I seed implants, if the postimplant dose evaluation is performed based on image scans taken between 5 and 9 weeks, the average error will be less than 5%, with a maximum possible error less than 10% in 80% coverage dose; for 103Pd seed implants, if the postimplant dose evaluation is performed based on image scans taken between 2 and 4 weeks, the average error will be less than 5%, with a maximum error less than 15% in 80% coverage dose. Because of edema, a conventional preimplant plan also overestimates dose coverage of prostate. On the average, a standard preimplant planning overestimates dose coverage by about 6% for 125I implants and 14% for 103Pd implants in our study. CONCLUSION: Based on the dynamic model, the optimum timing of image scans for postimplant dose evaluation of prostate seed implantation is 7 weeks postimplantation for 125I implants and about 3 weeks for 103Pd implants. (ABSTRACT TRUNCATED)

Brachytherapy↗

Expression of the AMP-activated protein kinase beta1 and beta2 subunits in skeletal muscle.

A heterotrimeric member of the AMP-activated protein kinase (AMPK) isoenzyme family was purified from rat skeletal muscle by immunoaffinity chromatography, consisting of an alpha2 catalytic and two non-catalytic subunits, beta2 and gamma1. The AMPK beta2 cDNA (271 amino acids (aa), molecular weight (MW)=30¿ omitted¿307, pI 6. 3) was cloned from skeletal muscle and found to share an overall identity of 70% with beta1 (270 aa, MW=30¿ omitted¿475, pI 6.0). In the liver AMPK beta1 subunit, Ser-182 is constitutively phosphorylated whereas in skeletal muscle beta2 isoform, we find that Ser-182 is only partially phosphorylated. In addition, the autophosphorylation sites Ser-24, Ser-25 found in the beta1 are replaced by Ala-Glu in the beta2 isoform. beta2 contains seven more Ser and one less Thr residues than beta1, raising the possibility of differential post-translational regulation. Immunoblot analysis further revealed that soleus muscle (slow twitch) contains exclusively beta1 associated with alpha2, whereas extensor digitorum longus muscle alpha2 (EDL, fast twitch) associates with beta2 as well as beta1. Sequence analysis revealed that glycogen synthase, a known AMPK substrate, co-immunoprecipitated with the AMPK alpha2beta2gamma1 complex.

AMP-Activated Protein Kinases↗

Non-suppressed conductivity and indirect UV detection of carboxylic acids in environmental samples by ion-exclusion chromatography using 2,6-pyridinedicarboxylic acidic eluent.

2,6-Pyridinedicarboxylic acid (PDCA) was evaluated as an eluent for indirect UV and non-suppressed conductivity detection of carboxylic acids in ion-exclusion chromatography. The effect of PDCA concentration on the separation and detection sensitivity was investigated. The reasonable resolutions between carboxylic acids were achieved using 1 mM PDCA eluent. Detection limits were 1.0-7.0 microM for conductivity detection and 8-30 microM for UV detection. Compared to the eluent containing 1 mM sulfuric acid, the method offers a high resolution and high detection sensitivity for both detectors due to its high molar absorptivity and low background conductance. The proposed method was demonstrated to be useful for the determination of carboxylic acids in environmental samples with direct sample injection.

Carboxylic Acids↗

Embryonic lethality and defective neural tube closure in mice lacking squalene synthase.

Squalene synthase (SS) catalyzes the reductive head-to-head condensation of two molecules of farnesyl diphosphate to form squalene, the first specific intermediate in the cholesterol biosynthetic pathway. We used gene targeting to knock out the mouse SS gene. The mice heterozygous for the mutation (SS+/-) were apparently normal. SS+/- mice showed 60% reduction in the hepatic mRNA levels of SS compared with SS+/+ mice. Consistently, the SS enzymatic activities were reduced by 50% in the liver and testis. Nevertheless, the hepatic cholesterol synthesis was not different between SS+/- and SS+/+ mice, and plasma lipoprotein profiles were not different irrespective of the presence of the low density lipoprotein receptor, indicating that SS is not a rate-limiting enzyme in the cholesterol biosynthetic pathway. The mice homozygous for the disrupted SS gene (SS-/-) were embryonic lethal around midgestation. E9.5-10.5 SS-/- embryos exhibited severe growth retardation and defective neural tube closure. The lethal phenotype was not rescued by supplementing the dams either with dietary squalene or cholesterol. We speculate that cholesterol is required for the development, particularly of the nervous system, and that the chorioallantoic circulatory system is not mature enough to supply the rapidly growing embryos with maternal cholesterol at this developmental stage.

Animals↗

Isolation of the protein kinase TAO2 and identification of its mitogen-activated protein kinase/extracellular signal-regulated kinase kinase binding domain.

We previously reported the cloning of the thousand and one-amino acid protein kinase 1 (TAO1), a rat homolog of the Saccharomyces cerevisiae protein kinase sterile 20 protein. Here we report the complete sequence and properties of a related rat protein kinase TAO2. Like TAO1, recombinant TAO2 selectively activated mitogen-activated protein/extracellular signal-regulated kinase kinases (MEKs) 3, 4, and 6 of the stress-responsive mitogen-activated protein kinase pathways in vitro and copurified with MEK3 endogenous to Sf9 cells. To examine TAO2 interactions with MEKs, the MEK binding domain of TAO2 was localized to an approximately 135-residue sequence just C-terminal to the TAO2 catalytic domain. In vitro this MEK binding domain associated with MEKs 3 and 6 but not MEKs 1, 2, or 4. Using chimeric MEK proteins, we found that the MEK N terminus was sufficient for binding to TAO2. Catalytic activity of full-length TAO2 enhanced its binding to MEKs. However, neither the autophosphorylation of the MEK binding domain of TAO2 nor the activity of MEK itself was required for MEK binding. These results suggest that TAO proteins lie in stress-sensitive kinase cascades and define a mechanism by which these kinases may organize downstream targets.

Amino Acid Sequence↗

Effects of histamine on MK-801-induced memory deficits in radial maze performance in rats.

The effects of histamine on the spatial memory deficits induced by MK-801 were investigated using the eight-arm radial maze paradigm in rats. Intracerebroventricular (i.c.v.) injection of histamine or thioperamide, and intraperitoneal (i.p.) injection of histidine improved the spatial memory deficits induced by MK-801. Similar results were obtained with 2-thiazolylethylamine. In contrast, 4-methylhistamine showed no significant effect. Based on these observations, it seems likely that the protective effect of histamine on MK-801-induced spatial memory deficit is mediated by H(1)-receptors.

Analysis of Variance↗

An immunoadhesin incorporating the molecule OX-2 is a potent immunosuppressant that prolongs allo- and xenograft survival.

We have established that, in mice receiving donor-specific immunization by the portal vein, the increased graft survival seen is associated with the increased expression of a molecule (OX-2) on a subpopulation of dendritic cells (DC), and polarization of cytokine production to type 2 cytokines on Ag-specific restimulation of cells from these mice. Furthermore, infusion of a mAb to OX-2 blocks both the increased graft survival and the altered cytokine production seen. We have constructed an immunoadhesin in which the extracellular domain of OX-2 is linked to the murine IgG2a Fc region, and we have expressed this molecule (OX-2:Fc) in a eukaryotic (baculovirus) expression system. Incubation of lymphocytes with 50 ng/ml OX-2:Fc inhibits a primary mixed lymphocyte reaction in vitro, as assayed by proliferation and induction of cytotoxic T cells, and also alters cytokine production with decreased IL-2 (IFN-gamma) production and increased IL-4 (IL-10) production. Similarly, in vivo infusion of OX-2:Fc promotes increased allo- and xenograft (both skin and renal grafts) survival and decreases the Ab response to sheep erythrocytes. Our data suggest this molecule might have clinical importance in allo- and xenotransplantation.

Animals↗

Decreased expression of CD80 is a marker for increased tumorigenicity in a new murine model of oral squamous-cell carcinoma.

We established a new syngeneic murine model of oral squamous-cell carcinoma (SCC) to analyze the potential role of immune recognition determinants in the early development of oral cancer. In this study, we examined whether SCC that undergo transformation and development in the absence of specific immunity exhibit differences in tumorigenicity that relate to differences in expression of CD80, CD86 or MHC class I. Mucosal keratinocytes from BALB/c mice were transformed in vitro with 4-nitroquinolone-1-oxide (4-NQO) and inoculated into SCID mice to obtain tumorigenic cell lines. Five SCC cell lines were re-isolated from tumors, and 4 retained cytokeratin and beta4-integrin markers of epithelial origin. Their growth was compared in BALB/c and in congenic SCID mice to establish whether the cell lines exhibit differences in immunogenicity. Three lines that showed slower growth or completely regressed when implanted in immune competent hosts retained or developed increased expression of CD80 during development in SCID mice. Conversely, 2 SCC lines that lost expression of CD80 after passage in vivo grew progressively in immune-competent hosts. MHC-class-I and CD86 expression did not correlate with tumorigenicity. These observations provide evidence that decreased expression of CD80 may serve as a marker for increased tumorigenicity during early development of oral SCC. The development of this new murine oral SCC model should prove useful in determining the potential effects of CD80 expression on the immune pathogenesis and therapy of SCC.

4-Nitroquinoline-1-oxide↗

Prodrugs of CL316243: a selective beta3-adrenergic receptor agonist for treating obesity and diabetes.

CL316243 is a highly selective and potent beta3-adrenergic receptor agonist, and has been shown in rodent models to be an effective agent for treating obesity and Type II diabetes. To improve the oral absorption and pharmacokinetic profiles of CL316243, a number of prodrugs have been synthesized and evaluated. Several ester-type prodrugs show significant improvements in oral bioavailability in both rodent and primate models.

Adrenergic beta-Agonists↗

Mutants of cholera toxin as an effective and safe adjuvant for nasal influenza vaccine.

The effectiveness and safety of mutants of cholera toxin (CT) as an adjuvant for nasal influenza vaccine was examined. Four CT mutants, called CT7 K (Arg to Lys), CT61F (Arg to Phe), CT112 K (Glu to Lys), and CT118E (Glu to Gln), were produced by the replacement of one amino acid at the A1-subunit using site-directed mutagenesis. All these mutants were confirmed to be less toxic than native CT when the toxicity was analysed by using Y1 adrenal cells in vitro. When high (1 microg) and low (0.1 microg) doses of these CT mutants, together with high (1 microg) and low (0.1 microg) doses of influenza A/PR/8/34 virus (H1N1) vaccine, respectively, were administered intranasally into BALB/c mice in a two dose regimen (twice, 4 weeks apart), they produced both anti-PR8 hemagglutinin (HA) IgA and IgG antibody (Ab) responses roughly in a dose-dependent manner. The relatively low level of anti-HA Ab responses, induced by the low dose CT mutants, were enough to provide complete protection against the homologous virus infection. Under these vaccination conditions, no anti-CTB IgE Ab responses were induced. The mutant CT112 K, which showed a relatively high adjuvant activity, the lowest toxicity and relatively high yields in a bacterial culture, seems to be the most effective and safest adjuvant for nasal influenza vaccine among those examined. The low dose of CT derivatives or vaccine used in the mouse model (0.1 microg/20 g mouse) corresponded to 100 microg/20 kg, the estimated dose per person. A tentative plan for safety standards for human use of CT (or LT) derivatives as an adjuvant of nasal influenza vaccine is discussed.

Adjuvants, Immunologic↗

[Arg8]-vasopressin-induced increase in intracellular Ca2+ concentration in cultured rat hippocampal neurons.

Changes in intracellular Ca2+ concentration ([Ca2+]i) induced by [Arg8]-vasopressin (AVP) were studied in cultured rat hippocampal neurons by fura-2 fluorometry. AVP (10-1,000 nM) caused a dose-dependent increase in [Ca2+]i. The selective V1 vasopressin receptor agonist [Phe2, Ile3, Orn8]-vasopressin also induced a significant increase in [Ca2+]i, whereas the selective V2 vasopressin receptor agonist [deamino Cys1, D-Arg8]-vasopressin showed no effect. The AVP-induced increase in [Ca2+]i was inhibited by the selective V1 vasopressin receptor antagonist d(CH2)5[Tyr2(Me), Arg8]-vasopressin and nonpeptide V1 antagonist OPC-21268. On the other hand, no antagonistic effects were observed with the V2 vasopressin antagonist desglycinamide-[d(CH2)5, D-Ile2, Ile4, Arg8]-vasopressin and nonpeptide V2 antagonist OPC-31260. The increase in [Ca2+]i induced by AVP was abolished after removal of extracellular Ca2+. In addition, AVP-induced [Ca2+]i elevation was not affected by treatment with verapamil, which blocked the [Ca2+]i increase induced by an isotonic high K(+)-medium (50 mM). However, omega-conotoxin GVIA completely inhibited the effect of AVP. These results suggested that the AVP-induced [Ca2+]i increase in cultured rat hippocampal neurons is due to influx of Ca2+ through V1 VP receptors coupled with N-type calcium channels.

Animals↗

Expression of a dominant-negative mutant inhibitor-kappaBalpha of nuclear factor-kappaB in human head and neck squamous cell carcinoma inhibits survival, proinflammatory cytokine expression, and tumor growth in vivo.

We demonstrated recently that constitutive expression of proinflammatory cytokines interleukin (IL)-1alpha, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor in head and neck squamous cell carcinoma is correlated with activation of transcription factor nuclear factor (NF)-kappaB/Rel A (p50/p65), which binds the promoter region within each of the genes encoding this repertoire of cytokines. NF-kappaB can be activated after signal-dependent phosphorylation and degradation of inhibitor-kappaBalpha and has been reported to promote cell survival and growth. In the present study, we expressed a phosphorylation site mutant of inhibitor-kappaBalpha (IkappaBalphaM) in head and neck squamous cell carcinoma lines UM-SCC-9, -11B, and -38 to determine the effect of inhibition of NF-kappaB on cytokine expression, cell survival in vitro, and growth in vivo. After transfection with IKBalphaM, only a few UM-SCC-9 clones were obtained that stably expressed the mutant IkappaB, suggesting that expression of a mutant IkappaBalpha may affect survival of the transfected UM-SCC cell lines. After cotransfection of IkappaBalphaM with a Lac-Z reporter, we found that the number of surviving beta-galactosidase-positive cells in the three cell lines was reduced by 70-90% when compared with controls transfected with vector lacking the insert. In UM-SCC-9 cells that stably expressed IkappaBalphaM, inhibition of constitutive and tumor necrosis factor-a induced NF-kappaB activation, and production of all four cytokines was observed. Although UM-SCC-9 IkappaBalphaM-transfected cells proliferated at the same rate as vector-transfected cells in vitro, a significant reduction in growth of tumor xenografts was observed in SCID mice in vivo. The decreased growth of UM-SCC-9 IkappaBalphaM-transfected tumor cells accompanied decreased immunohistochemical detection of the activated form of NF-kappaB in situ. These results provide evidence that NF-KB and IkappaBalpha play an important role in survival, constitutive and inducible expression of proinflammatory cytokines, and growth of squamous cell carcinoma. NF-kappaB could serve as a potential target for therapeutic intervention against cytokine and other immediate-early gene responses that contribute to the survival, growth, and pathogenesis of these cancers.

Animals↗

The host environment promotes the constitutive activation of nuclear factor-kappaB and proinflammatory cytokine expression during metastatic tumor progression of murine squamous cell carcinoma.

We reported previously that tumor cells isolated from metastases of the in vitro transformed squamous cell carcinoma line Pam 212 exhibit an elevation in constitutive production of proinflmmatory cytokines interleukin (IL)-1alpha, IL-6, granulocyte-macrophage colony-stimulating factor, and KC (the murine homologue of chemokine Gro-alpha). The basis for constitutive expression of these cytokines after tumor progression in vivo is unknown. Regulation of the expression of these proinflammatory cytokines involves transcription factor nuclear factor kappaB (NF-kappaB), which can be activated by cytokines such as tumor necrosis factor (TNF)-alpha. In this study, we compared the constitutive and TNF-alpha-induced expression of proinflammatory cytokines in parental Pam 212 and metastatic LY-2 and LY-8 cell lines and determined the relationship of cytokine expression to activation of NF-kappaB. We found that the metastatic cell lines exhibited an increase in constitutive and TNF-alpha-inducible expression of proinflammatory cytokines when compared with parental Pam 212 cells. The increased cytokine expression was associated with an increase in constitutive and TNF-alpha-inducible activation of NF-kappaB as demonstrated by electrophoretic mobility shift assay and luciferase-reporter gene assay. Constitutive nuclear localization of NF-kappaB p65 was observed in LY-2 and LY-8 cells in culture and in tumor specimens but rarely in Pam 212 cells, consistent with the constitutive activation of NF-kappaB in tumor cels after selection in vivo. Induction of NF-kappaB by TNF-alpha was inhibited by the addition of protease inhibitors calpain inhibitor I and N-tosyl-phechloromethyl ketone and antioxidant 1-pyrrolidinecarbodithioic acid, whereas constitutive activation of NF-kappaB and cytokine KC mRNA expression was inhibited by N-tosyl-phechloromethyl ketone alone. Overexpression of a human Ikappa(B)alpha dominant suppresser in Pam 212 cells inhibited TNF-alpha-induced NF-kappaB binding activity and KC expression. These data indicate that activation of NF-kappaB contributes to increased expression of proinflammatory cytokines during metastatic tumor progression of squamous cell carcinoma, and that distinct mechanisms may be involved in the regulation of constitutive and TNF-alpha-induced activation of NF-kappaB in squamous cell carcinoma.

Animals↗

Induction of apoptosis and suppression of clonogenicity of ovarian carcinoma cells with estrogen mustard.

BACKGROUND: This study was conducted to evaluate whether estramustine (estrogen mustard [EM]) is a promising alternative in the treatment of patients with epithelial ovarian carcinoma (OVCA). EM is a microtubule-associated protein (MAP) specific antimicrotubule agent with low toxicity. METHODS: The authors investigated the ability of EM to induce apoptosis and suppress colony formation of OVCA cells. Paclitaxel was used as a positive control. DNA electrophoresis and terminal deoxynucleotidyl dUTP-X nick end labeling (TUNEL) assays were used to detect internucleosomal DNA fragmentation. Flow cytometry was used to identify apoptotic cells and disturbance of the cell cycle of EM-treated OVCA cells further. Quantitation of detached cultured cells also provided a relative estimate of the apoptotic response of OVCA cells to treatment with EM. The colony formation assay was used to evaluate the effects of EM on clonogenicity. RESULTS: The effects of EM on four OVCA cell lines in culture were highly similar to those of paclitaxel in causing apoptosis and inhibiting clonogenicity. DNA electrophoresis and TUNEL assays showed that EM induced internucleosomal DNA fragmentation in OVCA cells. Flow cytometry showed changes typical of apoptotic changes and cell cycle block and synchronization at the G2/M-phase. Counting of detached cells showed a log-dose response to EM treatment. The colony formation assay also showed a log-dose response suppression of OVCA cell clonogenicity after treatment with EM. CONCLUSIONS: EM may be a promising candidate in the clinical treatment of patients with OVCA. The lower toxicity and MAP specific action of EM is a novel chemotherapy for OVCA.

Antineoplastic Agents, Alkylating↗