Synergistic anticancer effects of ganciclovir/thymidine kinase and 5-fluorocytosine/cytosine deaminase gene therapies

BACKGROUND: A bacterial enzyme, Escherichia coli cytosine deaminase, which converts the prodrug 5-fluorocytosine into the toxic drug 5-fluorouracil, and a viral enzyme, herpes simplex virus thymidine kinase, which converts ganciclovir from an inactive prodrug to a cytotoxic agent by phosphorylation, are being actively investigated for use in gene therapy for cancer. The purpose of this study was to determine whether combining these prodrug-activating gene therapies might result in enhanced anticancer effects. METHODS: Rat 9L gliosarcoma cells were transfected with plasmids containing the E. coli cytosine deaminase gene (9L/CD cells), with plasmids containing the herpes simplex virus thymidine kinase gene (9L/TK cells), or with both expression plasmids (9L/CD-TK cells). The drug sensitivities of the cell lines were evaluated; in addition, the sensitivities of 9L and 9L/CD-TK cells mixed in varied proportions were measured. The effects of prodrug treatment on 9L/CD-TK tumor growth (i.e., size and volume) in nude mice were monitored. The isobologram method of Loewe and the multiple drug-effect analysis method of Chou-Talalay were used to measure the interaction between the two prodrug-activating gene therapies. To elucidate the mechanism of interaction, the phosphorylation of ganciclovir in 9L/CD-TK cells after varying prodrug treatments was studied. RESULTS AND CONCLUSIONS: The presence of transfected cytosine deaminase and thymidine kinase genes in 9L gliosarcoma cells reduced cell survival, both in vitro and in vivo, following treatment with the relevant prodrugs; the effects of the two components appeared to be synergistic and related mechanistically to the enhancement of ganciclovir phosphorylation by thymidine kinase following 5-fluorouracil treatment.     

Vaccination for experimental gliomas using GM-CSF-transduced glioma cells

Within the pituitary, folliculostellate (FS) cells are considered to regulate the intercellular communication between endocrine cells by paracrine mechanisms. One of the possible paracrine factors involved, could be interleukin-6 (IL-6) which is produced by these cells. Since IL-6 has been shown to be a growth factor of pituitary cells, we have determined whether IL-6 can also influence FS cell proliferation. To test this, a FS cell-like mouse pituitary cell line (TtT/GF cells) was used that exhibits most characteristics of normal FS cells. Under serum-free conditions the proliferation of TtT/GF cells is critically dependent on the initial seeding density: cells seeded at low density do not grow at all whereas cells seeded at high density proliferate with maximal doubling times of 34 hrs. Mouse IL-6 (mIL-6) stimulated only low density cell cultures in a dose and time dependent manner. For cells seeded at high density, exogenously added IL-6 may have failed to stimulate growth because of endogenously produced mIL-6. Conditioned medium from TtT/GF cells, in which mIL-6 concentrations up to 1017 pg/ml were measured, stimulated the proliferation of TtT/GF cells, indicating an autocrine growth stimulatory mechanism. A neutralizing mIL-6 antibody partially suppressed the growth of TtT/GF cells seeded at high density and partially reduced the growth stimulatory activity of TtT/GF conditioned medium. Thus, IL-6 is one but not the only factor that is involved in the autocrine growth stimulatory loop. The relevance of this mechanism for normal FS cells and its physiological consequence needs to be elucidated.     

Search for a founder mutation in idiopathic focal dystonia from Northern Germany

Both the discovery of the DYT1 gene on chromosome 9q34 in autosomal dominant early-onset torsion dystonia and the detection of linkage for one form of adult-onset focal dystonia to chromosome 18p (DYT7) in a family from northern Germany provide the opportunity to further investigate genetic factors in the focal dystonias. Additionally, reports of linkage disequilibrium between several chromosome 18 markers and focal dystonia, both in sporadic patients from northern Germany and in members of affected families from central Europe suggest the existence of a founder mutation underlying focal dystonia in this population. To evaluate the role of these loci in focal dystonia, we tested 85 patients from northern Germany who had primary focal dystonia, both for the GAG deletion in the DYT1 gene on chromosome 9q34 and for linkage disequilibrium at the chromosome 18p markers D18S1105, D18S1098, D18S481, and D18S54. None of these patients had the GAG deletion in the DYT1 gene. Furthermore, Hardy-Weinberg analysis of markers on 18p in our patient population and in 85 control subjects from the same region did not support linkage disequilibrium. Taken together, these results suggest that most cases of focal dystonia in patients of northern German or central European origin are due neither to the GAG deletion in DYT1 nor to a proposed founder mutation on chromosome 18p but must be caused by other genetic or environmental factors.     

Outcomes following mechanical ventilation in children undergoing bone marrow transplantation

Between 1976 and 1992, 869 patients <19 years of age underwent BMT at the University of Minnesota for a variety of malignant and non-malignant disorders. One hundred and ninety-six required mechanical ventilation (MV) at some time from the start of pre-BMT cyto reduction through the first year following BMT. Reasons for MV included respiratory compromise, upper airway management and non-pulmonary indications for respiratory support. In multivariate models, underlying diagnosis, receipt of HLA-mismatched marrow and the presence of acute graft-versus-host disease (aGVHD) were independent predictors of the need for MV. Indication for MV, underlying diagnosis, and presence of aGVHD were independent predictors of successful extubation. Overall survival at 2 years was 14% among MV patients and 52% among non-MV patients. While the need for MV during BMT reduces the overall likelihood of survival, 40% of children who required MV were successfully extubated; 35% of these extubated patients were long-term survivors. This outcome is better than that reported for adult BMT patients requiring respiratory support, who show survival of <5% at 6 months following BMT. Our data suggest extrapolation of outcome data from adult to pediatric patients is not appropriate and aggressive care of pediatric patients requiring respiratory support is not futile.     

Targeting gene therapy vectors to CNS malignancies

Multidrug resistance to anti-cancer drugs is a major medical problem. Resistance is manifested largely by the product of the human MDR1 gene, P-glycoprotein, an ABC transporter that is an integral membrane protein of 1280 amino acids arranged into two homologous halves, each comprising 6 putative transmembrane alpha-helices and an ATP binding domain. Despite the plethora of data from site-directed, scanning and domain replacement mutagenesis, epitope mapping and photoaffinity labeling, a clear structural model for P-glycoprotein remains largely elusive. In this report, we propose a new model for P-glycoprotein that is supported by the vast body of previous data. The model comprises 2 membrane-embedded 16-strand beta-barrels, attached by short loops to two 6-helix bundles beneath each barrel. Each ATP binding domain contributes 2 beta-strands and 1 alpha-helix to the structure. This model, together with an analysis of the amino acid sequence alignment of P-glycoprotein isoforms, is used to delineate drug binding and translocation sites. We show that the locations of these sites are consistent with mutational, kinetic and labeling data.     

Body mass index and the risk of cancers of the gastric cardia and distal stomach in Shanghai, China

The divergent incidence patterns of gastric cardia and distal stomach cancers suggest different etiologies. Although obesity has recently been linked to cardia cancer in Western populations, its association with distal stomach cancer remains unclear. This study examined the relation of anthropometric measurements to risk by subsites of stomach cancer in a Chinese population. We identified 1124 population-based cases of stomach cancer, ages 20-69 years, newly diagnosed between December 1988 and November 1989 in Shanghai, China. Controls (n = 1451) were randomly selected from permanent Shanghai residents and frequency-matched to cases by age and sex. Information on demographic characteristics, height and weight, diet, smoking, and other exposures was obtained by trained interviewers in person. The body mass index (BMI) was calculated as weight in kilograms divided by height in square meters and categorized into quartiles based on the distribution among controls. Odds ratios and 95% confidence intervals were estimated using logistic regression models, simultaneously adjusting for age, education, income, cigarette smoking (men only), alcohol drinking (men only), intake of total calories, and chronic gastric diseases. For gastric cardia cancer, the odds ratios among men were 1.4, 1.5, and 3.0 in the second, third, and fourth quartiles of usual BMI (P for trend, < 0.01). Among women, elevated risks also were associated with excess weight, but the gradient in risk was not smooth. Risk patterns for usual body weight, maximum BMI, and minimum BMI were similar to those found for usual BMI. For distal stomach cancer, no association with usual BMI was observed among men, but a slightly elevated risk was seen among women. Our observations in China support recent findings in Western populations that obesity contributes to the risk of gastric cardia cancer, especially among men.     

Analysis of failure times for multiple infections following bone marrow transplantation: an application of the multiple failure time proportional hazards model

We report an application of the proportional hazards model for multiple failure times in a study arising from the Bone Marrow Transplant Database at the University of Minnesota. The study compared the risk of infections after transplantation for patients who received allogeneic bone marrow transplants from unrelated donors (URD) versus related donors (RD). In 249 patients there was a total of 365 infections in 2.5 years of follow-up. The multiple failure time model uses all the data and provides empirical estimates of standard errors that incorporate the within-person dependencies in the data. The estimate of relative risk associated with URD was 1.4 (naive 95 per cent confidence interval 1.14 to 1.73, empirical 1.08 to 1.79), compared to the estimate 1.6 (naive or empirical, 1.1 to 2.1) from the proportional hazards model on 165 first infections only. The multivariate model gives great flexibility in modelling, for example, in accommodating a separate base hazard function for each type of failure and in allowing analysis of intervals between infections as an alternative to analysis of time from a marker event, here transplantation.     

CCTV主楼大悬臂钢结构施工关键技术

CCTV主楼为复杂连体结构,连体悬臂结构是结构的核心部分,呈空间“L”形,具有结构施工难度大,悬挑跨度大、结构位形控制要求高、施工安全控制难度大等特点。通过合理制订悬臂钢结构安装方案,采用合龙关键施工技术,包括合龙前的位形分析、合龙构件结构分析及主要施工措施等,确保了悬臂结构合龙顺利完成。     

Effects of the novelty or familiarity of visual stimuli on the expression of the immediate early gene c-fos in rat brain

To investigate substrates of recognition memory, the cellular expression of Fos protein in rat brain has been studied after groups of rats were either shown sets of novel or highly familiar objects, or were exposed to the same pattern of illumination without objects being shown. Counts of stained nuclei were made in eight brain regions, where information about novel or familiar visual stimuli is likely to be processed or stored. The counts were relatively high in occipital visual association cortex and area TE of temporal cortex, intermediate in perirhinal cortex, entorhinal cortex, anterior cingulate cortex and the diagonal band of Broca, and low in the hippocampal formation and mediodorsal nucleus of the thalamus. The number of Fos-stained cells was significantly higher for the rats shown novel objects than for those shown familiar objects in perirhinal cortex, area TE, occipital cortex and anterior cingulate cortex. Arguments are advanced that these differences in counts indicate areas involved in the processing and/or storage of information about the novelty or familiarity of visual stimuli, information important to recognition memory.     

协同过滤算法中一种改进的相似性计算方法

协同过滤算法作为一种成功的个性化推荐技术已经被应用到很多领域中.传统的协同过滤算法中用户相似性的计算只考虑了用户评分信息而没有考虑到用户的社会背景信息,针对这个问题,本文提出了基于用户社会信息的相似度计算方法,实验表明,改进后的协同过滤算法能更好地反映用户兴趣,提高推荐精度,在推荐效果方面得到了更好的改善.