Gene expression levels

When applying any of these models it is crucial to understand the main transport mechanisms as well as the metabolic route and characterization of the activity of the transporter/enzyme involved. It is well recognized that the activities of carrier-mediated processes in Caco-2 cells are considerably lower than in vivo [20, 42, 48] therefore, it is crucial to extrapolate in vitro cell culture data to the in vivo situation with great care [18, 20, 42, 48], This is especially important when carrier-mediated processes are involved, as evidenced by a recent report which showed significant differences in gene expression levels for transporters, channels and metabolizing enzymes in Caco-2 cells than in human duodenum [48], If an animal model is used, then potential species differences must also be considered [18, 20, 45],... 

Figure 2.13 Comparison of gene expression levels for (A) MDR1 (i.e. P-gp) and (B) human CYP3A4 and the homology in rat (CYP3A9), in duodenum and colon of human and rat intestine. The expression levels of transporters and metabolic enzymes are normalised by GADPH expression, transformed by natural logarithm and absolute values were used in the correlation analysis [121].

Ex Vivo Transporter Gene Expression Levels at the Inner Blood-Retinal Barrier (Magnetic Isolation of Retinal Vascular Endothelial Cells)... 

Figure 14.5 Schematic diagram of the magnetic isolation method for rat retinal vascular endothelial cells (RVEC) (A) and the transcript level of organic anion-transporting polypeptides (Oatps) in RVEC (B). A Endothelial cells (RVEC) EC, Nonendothe-lial cells (Non-RVEC) Non-EC. B Not detected N.D. Data taken from Journal of Neurochemistry, 91, Tomi and Hosoya, Application of magnetically isolated rat retinal vascular endothelial cells for the determination of transporter gene expression levels at the inner blood-retinal barrier. 1244-1248, 2004, with permission from Blackwell Publishing.

M. Tomi and K. Hosoya. Application of magnetically isolated rat retinal vascular endothelial cells for the determination of transporter gene expression levels at the inner blood-retinal barrier. J. Neurochem. 91 1244—1248 (2004). 

Acetylation is a reversible modification on proteins that can also contribute to protein localization and function. Acetylation of lysine residues in histone proteins can control the secondary structure of chromatin as well as gene expression levels from certain loci, and chromatin remodeling and its consequences in a variety of molecular and cell biological questions are intensely researched. Many other proteins undergo reversible acetylation, and the functional consequences of these modifications are poorly understood in many cases. 

Salonga, D., Danenberg, K. D., Johnson, M., et al. (2000) Colorectal tumors responding to 5-fluorouracil have low gene expression levels of drhydropyrimidine dehydrogenase, thymi-dylate synthase, and thymidine phosphorylase. Clin. Cancer Res. 6, 1322-1327. 

Antigen-induced, non immune response-related gene expression changes Immune response characteristics on gene expression level at 6 and 13 months, respectively ... 

Host organism Construct and gene Expression level Comments and references... 

Another important point was made by this study if possible, use reference samples with gene expression levels similar to those expected for the test samples. This should improve quantification at the low end. Moreover, the Tan et al., (2003) and Barczak (2003) studies also demonstrate the need for the standardization of commercial microarray products and reference standards so that both interlaboratory and cross-platform performances can be properly assessed. While commercial microarrays from different vendors all claim substantial gene probe "real estate," the number of probes in common is smaller. This makes it difficult to compare experiments across platforms, especially those from major suppliers such as Affymetrix, Agilent, and Amersham (Figure 2.8). 

Figure 5.1 Comparison of gene expression levels Northern (mRNA) vs. microarray. (From Schena, M. et al., Proc. Natl. Acad. Sci. USA, 93, 10614-10619, 1996. With permission.)...

Check the staining status occasionally under a dissection microscope since the staining can show up quickly, but minimize exposure of samples to light. Generally, the color develops within 20 min at room temperature if the gene expression level is relatively high. 

Many of the anti-neoplastic drugs currently available on the market specifically target the cancerous tumor and do not account for the overall heterogeneity of the disease. It is reasonable to assume that due to the complex make-up of a tumor, combined therapies may be necessary to treat the different cell types involved. One major hurdle to understanding tumor cells at the gene expression level is our limited ability to isolate pure populations of diseased cells. 

Gene expression, a determinant of a cell s characteristics, is another phenotype that can be studied using lymphoblastoid cell lines. Studies have shown that gene expression levels in humans differ not only among cell types within an individual, but also among individuals (16,31). As a result, there have been several recent studies that have identified polymorphic genetic variants that influence gene expression levels (15,25,32). 

Wallqvist A, Rabow AA, Shoemaker RH et al. Linking the growth inhibition response from the National Cancer Institute s anti-cancer screen to gene expression levels and other molecular target data. Bioinformatics 2003 19 2212- 2224. 

Gene Expression Levels Associated with Outcome (5-FU Chemotherapy)... 

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