Hepatocyte targeting with Gd-EOB-DTPA - Potential application for gene therapy

RATIONALE AND OBJECTIVES. TO evaluate the suitability of the liver-specific MRI contrast agent Gd-EOB-DTPA as a nonviral vector for gene therapy of he patocellular carcinoma. METHODS. Specific uptake of Gd-EOB-DTPA was quantified by relaxometry in ra t cultured hepatocytes and the hepatoma cells HepG2 and Huh7. Nonviral vect ors for gene transfer were synthesized by coupling Gd-EOB-DTPA to polyethyl eneimine or polylysine as DNA condensing agents, and their efficiency was s tudied using P-galactosidase (lacZ) as the reporter gene. RESULTS. Gd-EOB-DTPA was specifically taken up by rat cultured hepatocytes (4.32 vs. 1.08 mmol/L in nonhepatocyte control cells) but not by the hepato ma cells; this uptake was concentration-dependently inhibited by Bromsulpht alein, Polycation linkages were achieved with yields of 0.9 Gd-EOB-DTPA mol ecule per polyethyleneimine molecule and 10 Gd-EOB-DTPA molecules per polyl ysine molecule. Incubating the cells with plasmids containing lacZ reporter gene and polyethyleneimine-Gd-EOB-DTPA resulted in a few blue (transfected ) cells, whereas no blue cells were observed on incubation with polylysine- Gd-EOB-DTPA. CONCLUSIONS. Gd-EOB-DTPA is taken up by normal hepatocytes but not by HepG2 and Huh7 cells, probably because of the lack of the organic anion transpor ter in these hepatoma cells. The Gd-EOB-DTPA polycation conjugates, such as polyethyleneimine-Gd-EOB-DTPA, could serve as transfer vectors of interest for gene targeting imagery at the early stage of hepatocarcinogenesis. How ever, the transfer efficiency of such conjugates is low and requires improv ement.