Disconnecting the yin and yang relation of epidermal growth factor receptor (EGFR)-mediated delivery: a fully synthetic, EGFR-targeted gene transfer system avoiding receptor activation.

The epidermal growth factor receptor (EGFR) is upregulated within a high percentage of solid tumors and hence is an attractive target for tumor-targeted therapies including gene therapy. The natural EGFR ligand epidermal growth factor (EGF) has been used for this purpose, despite the risk of mitogenic effects due to EGFR activation. We have developed a fully synthetic, EGFR-targeted gene delivery system based on PEGylated linear polyethylenimine (LPEI), allowing evaluation of different EGFR-binding peptides in terms of transfection efficiency and EGFR activation. Peptide sequences directly derived from the human EGF molecule enhanced transfection efficiency with concomitant EGFR activation. Only the EGFR-binding peptide GE11, which has been identified by phage display technique, showed specific enhancement of transfection on EGFR-overexpressing tumor cells including glioblastoma and hepatoma, but without EGFR activation. EGFR targeting led to high levels of cell association of fluorescently labeled polyplexes after only 30 min of incubation. EGF pretreatment of cells induced enhanced cellular internalization of all polyplex types tested, pointing at generally enhanced macropinocytosis. EGF polyplexes diminished cell surface expression of EGFR for up to 4 hr, whereas GE11 polyplexes did not. In a clinically relevant orthotopic prostate cancer model, intratumorally injected GE11 polyplexes were superior in inducing transgene expression when compared with untargeted polyplexes.

Priming the cow for mobilization in the periparturient period: effects of supplementing the dry cow with saturated fat or linseed.

High-producing dairy cows experience negative energy balance in early lactation. Dry-cow feeding management will affect the performance and metabolic status of dairy cows in the following early lactation. The present study evaluates dry-cow feeding strategies for priming lipid metabolism in the dairy cow to overcome the metabolic challenges in the following early lactation. Five weeks before expected calving, 27 cows were assigned to 1 of 3 isonitrogenous and isoenergetic dietary treatments: a low-fat control diet (dry-control); a high saturated fat diet (dry-HSF); and a high linseed diet (dry-HUF). The cows were fed the same TMR lactation diet after calving. The treatments were evaluated by performance and metabolic parameters in blood and liver. The cows fed dry-HSF and dry-HUF had significantly greater plasma nonesterified fatty acid concentrations compared with dry-control, and the dry-HUF cows had the greatest C18:3 concentrations in plasma in the prepartum period. Further, the cows fed dry-HSF and dry-HUF diets had a tendency for the greatest capacity for incomplete beta-oxidation of fatty acids in the liver in wk 3 prepartum. The plasma cholesterol concentration was greatest for cows fed dry-HSF in the prepartum period compared with those fed dry-control and dry-HUF. The cows fed dry-HSF had the lowest plasma nonesterified fatty acid and liver fat concentrations in early lactation compared with the cows fed dry-control and dry-HUF. Data in the literature and the present experiment indicate that supplementing dry cows with a saturated fatty acid source is a positive strategy for priming dairy cows for body fat mobilization in the following early lactation.