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D E Post

Publications and source records attributed to D E Post.

4 recordsLinked to original sources
PubMed2004

Tumor-specific gene expression using the survivin promoter is further increased by hypoxia.

Increasing evidence indicates that survivin, an inhibitor of apoptosis protein (IAP), is expressed in human cancer cells but is absent from most normal adult tissues. Here, we examined the feasibility of using a survivin promoter (Sur-P) to direct therapeutic expression of a proapoptotic gene specifically in human tumor cells. First, we demonstrated that this promoter was highly active in human tumor cells but not in normal cells. Second, we found that Sur-P activity was upregulated by hypoxia in tumor cells. Third, to further enhance this promoter's activity under hypoxia, we added a hypoxia-responsive element (HRE) from the vascular endothelial growth factor gene promoter in its 5' region, and showed that this combination resulted in a further increase in the level of gene expression in hypoxic tumor cells. Finally, we demonstrated that expression of an autocatalytic reverse caspase-3 gene by this promoter specifically induced apoptotic cell death in human tumor cells but not in normal cells. These findings support the use of promoters Sur-P or chimeric HRE-Sur-P for generating novel vectors for cancer gene therapy.

Apoptosis↗
PubMed2001

Generation of bidirectional hypoxia/HIF-responsive expression vectors to target gene expression to hypoxic cells.

Hypoxia initiates an adaptive physiological response in all organisms and plays a role in the pathogenesis of several human diseases. The hypoxia/HIF-inducible factor-1 (HIF-1) transcription factor mediates transcriptional responses to hypoxia by binding to a cis-acting hypoxia-responsive element (HRE) present within target genes. The use of the HIF-1/HRE system of gene regulation can be utilized as a mechanism to target expression of therapeutic genes to hypoxic cells or cells that have a constitutively active HIF-1/HRE pathway due to cell transformation. Given the rapid resistance of tumors to single therapeutic strategies, new vector systems need to be developed that can deliver multimodal therapy. Here we show that HREs function as classical enhancer elements and function bidirectionally to co-regulate the expression of two genes. We designed a large series of novel bidirectional hypoxia/HIF-responsive expression vectors using HREs derived from the human vascular endothelial growth factor (VEGF) and erythropoietin (EPO) genes. We measured the ability of these constructs to express the luciferase and LacZ/beta-galactosidase (beta-gal) reporter genes bidirectionally under normoxic (21% O(2)) versus hypoxic (1, 3, 5, and 10% O(2)) conditions by transient transfection in three human glioma cell lines (LN229, U251MG and U138MG). Nine constructs were identified that exhibited moderate to high inducibility at 1% O(2) while maintaining tight regulation under normoxic conditions. Moreover, the level of activation was a function of O(2) concentration and was exponential at O(2) levels below 5%. These vectors will be valuable tools in a variety of gene therapy applications targeting pathological activation of the HIF-1/HRE pathway.

Cell Hypoxia↗
PubMed1995

Culture media for the isolation of campylobacters.

The history of the development of selective media for isolation of campylobacters, including the rationale for choice of selective agents is described. Developments have included modifications to allow incubation at 37 degrees C instead of 42 or 43 degrees C and changes in the types and concentrations of antibiotics in order not to inhibit organisms such as Campylobacter upsaliensis, C. jejuni subsp. doylei and some strains of C. coli and C. lari. When examining foods, plating media originally developed for isolation from faeces are normally used, sometimes after liquid enrichment. Most of the media include ingredients intended to protect campylobacters from the toxic effect of oxygen derivatives. Most commonly used are lysed or defibrinated blood; charcoal; a combination of ferrous sulphate, sodium metabisulphite and sodium pyruvate (FBP); and haemin or haematin. To date no medium includes an indicator system--for instance a pH indicator to show whether colonies produce acid or alkali from particular substrates. The manner in which liquid enrichment media are used has been modified for food samples to avoid inhibitory effects on sublethally damaged cells by toxic components in the formula. This is done by a preliminary period of incubation at reduced temperature and sometimes by delayed addition of antibiotics. Expensive and time-consuming methods have been proposed to achieve a microaerobic atmosphere while using liquid enrichment media. To date there is no generally accepted 'standard' method of isolating campylobacters from food.

Anti-Bacterial Agents↗