Regulation of the phosphoenolpyruvate carboxykinase/human factor IX gene introduced into the livers of adult rats by receptor-mediated gene transfer.

Gene transfer systems targeting the asialoglycoprotein receptor have been developed to introduce functional genes into cells in culture and livers of intact animals. A synthetic neoglycoprotein carrier was constructed and complexed to a chimeric gene containing the cDNA for human factor IX ligated to the promoter-regulatory region of the gene for phosphoenolpyruvate carboxykinase from the rat. The complex was used to transfect human hepatoma cells that express the asialoglycoprotein receptor. Human factor IX DNA sequences were found in cells 10 days after treatment. A 1.4 kB mRNA transcript was detected by Northern blot hybridization, which was inducible by treatment with dexamethasone or cAMP with theophylline. Western blot hybridization of proteins secreted into the culture medium detected human factor IX. The chimeric gene was also transferred into livers of rats using the neoglycoprotein carrier system after partial hepatectomy. Although the results were variable, the exogenous gene was transcribed in livers of several animals, and maximal levels of expression of the fully processed human factor IX were detected 30 days after introduction. The concentration of factor IX in the blood returned to control levels 60 days after transfection. Factor IX production was induced as late as 96 days after treatment by feeding transfected animals a diet high in protein but devoid of carbohydrates. This DNA carrier system can be used to introduce functional genes into the livers of rats, and may be a useful technique for gene therapy targeting the liver.