EFFICIENT ADENOVIRUS-MEDIATED ECTOPIC GENE-EXPRESSION OF HUMAN LIPOPROTEIN-LIPASE IN HUMAN HEPATIC (HEPG2) CELLS

Gene therapy to deliver and express a corrective lipoprotein lipase (L PL) gene may improve the lipid profile and reduce the morbidity and po tential atherogenic risk from hypertriglyceridemia and dyslipoproteine mia in patients with complete or partial LPL deficiency, We have used an E1-/E3- adenoviral vector, with an RSV-driven human LPL cDNA expres sion cassette (Ad-RSV-LPL), to achieve high ectopic LPL gene expressio n in the human hepatoma cell line HepG2, an accepted hepatocellular mo del of lipoprotein metabolism, Ad-RSV-LPL transduction of HepG2 cells with a multiplicity of infection (moi) between 12.5 and 100 yielded do se-dependent increments in LPL mass and activity, Peak levels of LPL p rotein of 2,032.1 +/- 274.5 ng/10(5) cells per mi (moi 100) correlated with increased activity of 92.7 +/- 22.6 mU/10(5) cells per mi relati ve to negligible LPL levels in Ad-RSV-LacZ (beta-galactosidase) contro ls. Exogenous LPL expression over a 5-day period peaked at day 3. Susc eptibility to inhibition by 1 M NaCl and an anti-LPL monoclonal antibo dy confirmed that lipase activity was indeed derived from human LPL, H ydrolysis, by LPL-overexpressing HepG2 cells, of TG carried in very-lo w-density lipoprotein (VLDL) showed that greater than 50% of the trigl ycerides (TG) disappeared after 4 hr of incubation, These results were compatible with FPLC evidence of a marked reduction in VLDL-TG, These results provide strong in vitro evidence that adenoviral-mediated ect opic expression of the human LPL gene could render hepatic cells capab le of VLDL catabolism and thus support the possibility for in vivo ade noviral vector-mediated liver-targeted LPL gene therapy.