Construction of a bispecific antisense oligonucleotide containing multiple binding sites for the treatment of hormone insensitive prostate tumors

Abstract

Antisense oligonucleotides (oligos) have demonstrated efficacy for the treatment of various cancers, infectious diseases and metabolic disorders. While most studies have utilized single oligos either administered alone, or more recently in combination therapy with other drugs, some investigators have administered more than one oligo in a combined administration or have designed oligos which target multiple proteins (those which share mRNA sequence homology). Antisense oligos inhibit mRNA translation through complementary base pair binding, often about the AUG initiation codon. This inhibition is further enhanced through destruction of the mRNA:oligo hybrid by RNAse H. Construction of an oligo with multiple binding sites located about the respective mRNA initiation codons could simultaneously block translation of more than one protein, even those unrelated in sequence. Such binding could produce a complex mRNA:oligo hybrid more prone to degradation and clearance. Furthermore, such a formulation would increase oligo specific activity and cellular uptake, reduce toxicity, and stabilize at 1:1 the ratio between multiple oligo active sites which otherwise must be comparably delivered (in amount) and individually targeted. The activity of these newly constructed oligos could be tested in both in vitro and in vivo prostate tumor models, utilizing the hormone sensitive LNCaP and the hormone insensitive PC-3 lines. In vitro testing would evaluate oligos administered either alone or in combination with other chemotherapeutics. In vivo testing would administer the oligos to tumors carried in athymic nude mice by either intratumoral inoculation or by using a diffusion pump. Antisense oligos which target proteins associated with growth factors or their receptors, could have a role in the treatment of human prostate cancers when administered with hormone deprivation therapy, or against tumors which have already become hormone insensitive. In the later case, such treatment could form the basis of a second tier of therapy based upon growth factor deprivation.