Improved Delivery in Cell Culture of Radiolabeled Antisense DNAs by Duplex Formation

Abstract

Delivery remains an unresolved problem in applications requiring intravenous administration of DNAs. Recently improved antisense translation interruption in cells was reported for an antisense (AS) oligomer as a duplex compared to singlet AS oligomer presumably because of improved delivery. The unstable phosphodiester backbone of the sense (S) oligomer and its shorter chain length apparently encouraged intracellular dissociation and release of the AS oligomer. We have investigated the mechanism involved to evaluate whether the approach may be useful for antisense radionuclide imaging. Duplexes were formed between an AS phosphorothioate DNA against the mdr1 mRNA and the uniform phoshorothioate or uniform phosphodiester sense (S) DNAs with either four or six mismatches. Accumulations in KB-G2 (Pgp++) cells of radiolabeled AS DNA as duplex accumulated threefold higher compared to singlet. Accumulation was still antisense as shown by reduced accumulations with the radiolabel on the S DNA. However, the DNA backbone had no clear influence on accumulations. Targeting of mRNAs with radiolabeled AS DNAs may be improved in cell culture if duplexed with an S DNA engineered for low hybridization affinity to encourage dissociation in the presence of the target mRNA.