Selective gene inhibition by antisense
oligodeoxynucleotide (AS-ODN) or by small interference RNA (
siRNA)
therapeutics promises the treatment of diseases that cannot be cured by conventional drugs. However, antisense
therapy is hindered due to poor stability in physiological fluids and limited intracellular uptake. To address these problems, a
ligand targeted and sterically stabilized nanoparticle formulation has been developed in our lab. Human
lung cancer cells often overexpress the
sigma receptor and, thus, can be targeted with a specific
ligand such as anisamide. AS-ODN or
siRNA against human
survivin was mixed with a carrier
DNA, calf thymus DNA, before complexing with
protamine, a highly positively charged
peptide. The resulting particles were coated with cationic
liposomes consisting of
DOTAP and
cholesterol (1:1, molar ratio) to obtain LPD (
liposome-polycation-
DNA) nanoparticles.
Ligand targeting and steric stabilization were then introduced by incubating preformed LPD nanoparticles with
DSPE-PEG-anisamide, a PEGylated
ligand lipid developed earlier in our lab, by the postinsertion method. Nontargeted nanoparticles coated with
DSPE-PEG were also prepared as a control. Antisense activities of nanoparticles were determined by
survivin mRNA down-regulation,
survivin protein down-regulation, ability to trigger apoptosis in
tumor cells,
tumor cell growth inhibition, and chemosensitization of the treated
tumor cells to anticancer drugs. We found that
tumor cell delivery and antisense activity of PEGylated nanoparticles were sequence dependent and rely on the presence of anisamide
ligand. The uptake of
oligonucleotide in targeted, PEGylated nanoparticles could be competed by excess free
ligand. Our results suggest that the
ligand targeted and sterically stabilized nanoparticles can provide a selective delivery of AS-ODN and
siRNA into
lung cancer cells for
therapy.