Adenovirus-mediated apo(a)-antisense-RNA expression efficiently inhibits apo(a) synthesis in vitro and in vivo

Apo(a) is a very atherogenic plasma protein without apparent function, whic h is highly expressed in humans. The variation in plasma Lp(a) concentratio n among individuals is considerable. Approximately 10-15% of the white popu lation exhibit plasma Lp(a) concentrations above the atherogenic cut-off va lue of approximately 30 mg/dl. Since there is currently no safe way of trea ting those patients with drugs, we have tested the possibility of interferi ng with apo(a) biosynthesis by adenovirus-mediated expression of antisense apo(a) mRNA comprising the 5' UTR, the signal sequence and the first three kringles of native apo(a). Transduction of rat hepatoma McA RH 7777 cells w hich stably expressed apo(a) with 18 kringle IV (KIV) domains with apo(a)-a ntisense adenovirus (AS-Ad) at multiplicity of infection (MOl) of 30 reduce d apo(a) synthesis to 23% as compared with control cells. As apo(a) is not synthesized in laboratory animals, we induced biosynthesis of the N-termina l fragments of apo(a) in mice by adenovirus-mediated gene transfer. Cotrans duction of these mice with AS-Ad which expressed up to eight times higher a mounts of apo(a) than stable transgenic apo(a) mice, led to an almost compl ete disappearance of apo(a)from plasma. We conclude that the proposed AS-co nstruct is very efficient in interfering with apo(a) biosynthesis in vivo. The strategy of inducing the synthesis of a nonexpressed protein followed b y knocking it out by AS technology may also be applicable to other systems.