We used polypropylenimine dendrimers for delivering a 31 nt triplex-forming oligonucleotide (ODN) in breast, prostate and ovarian cancer cell lines, using 32P-labeled ODN. Dendrimers enhanced the uptake of ODN by ∼14-fold in MDA-MB-231 breast cancer cells, compared with control ODN uptake. Dendrimers exerted their effect in a concentration-and molecular weight-dependent manner, with generation 4 (G-4) dendrimer having maximum efficacy. A similar increase in ODN uptake was found with MCF-7 and SK-BR-3 (breast), LNCaP (prostate) and SK-OV-3 (ovarian) cancer cells. The dendrimers had no significant effect on cell viability at concentrations at which maximum ODN uptake occurred. [3H]Thymidine incorporation showed that complexing the ODN with G-4 significantly increased the growth-inhibitory effect of the ODN. Western blot analysis showed a significant 65% reduction of c-myc protein level in ODN-G-4 treated cells compared with that of ODN-treated/control cells. Gel electrophoretic analysis showed that ODN remained intact in cells even after 48 h of treatment. The hydrodynamic radii of nanoparticles formed from ODN in the presence of the dendrimers were in the range of 130-280 nm, as determined by dynamic laser light scattering. Taken together, our results indicate that polypropylenimine dendrimers might be useful vehicles for delivering therapeutic oligonucleotides in cancer cells.
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