Patterns of cellular uptake and effects on cell survival using antimetallothionein oligodeoxyribonucleotide conjugates in vitro

Synthetic oligodeoxyribonucleotides (ODNs) offer the potential for the sequence-specific modulation of viral and cellular gene expression. However, several problems such as efficient delivery into cells, metabolic stability and delivery to specific cellular targets may limit their usefulness. Studies were designed to demonstrate that the covalent conjugation of an 18 mer ODN complementary in sequence to mRNA ODN with various polypeptide ligands, including poly(L-lysine), phosphomannan and asialo-orosomucoid, elicits a pattern of enhanced yet differential uptake into Chang and V79 cells in culture. Viability of cells exposed to conjugated ODNs was measured using a colorimetric assay (MTT). The ODNs covalently linked to poly(L-lysine) reveal an increased efficiency of antisense-directed cell killing from concentrations greater than 3 μM to less than 100 nM. Finally, poly(L-lysine) is also cytotoxic, particularly at extremes of molecular weight. Hence, these studies indicate that synthetic ODNs conjugated to peptides may offer enhanced cellular uptake leading to more efficient antisense activity. However, the cytotoxicity of ODN conjugates may limit their usefulness as research tools or therapeutic agents.