CELLULAR UPTAKE OF OLIGODEOXYRIBONUCLEOSIDE METHYLPHOSPHONATES

The cellular uptake of oligodeoxyribonucleoside methylphosphonates has been evaluated using three radiolabeled oligomers, Oligomers I and II ([H-3]-T-8 and [H-3]-T-16, respectively) are nonionic methylphosphonate oligomers labeled with tritium on the phosphonate internucleotide linkage. EDA-III contains a single phosphodiester linkage, a [P-32]-label and an ethylenediamine conjugate at the [P-32]-5'-end, All three oligomers are stable in cells. At a 1 mu M concentration, oligomer I is not taken up by human erythrocytes, The octanol/DPBS partition coefficients for oligomers I and II (1.5 x 10(-4) and 4.2 x 10(-4), respectively) further indicate that these molecules should not diffuse across cell membranes at appreciable rates. Oligomer I is taken up by HL-60 cells, although at a slower rate than the uptake of the fluid-phase marker sucrose, The cell-associated levels of oligomer II in K-562 cells following incubation of cells with the oligomer for 2 days is independent of concentration and nonsaturable, suggesting a mechanism of uptake independent of receptor, Finally, the initial uptake rate of EDA-III in mouse L cells is greater than the uptake of two oligodeoxyribonucleotides (T-8, T-16), reaching a plateau after 3 hours incubation with cells. These observations should aid in the elucidation of the mechanism by which this class of antisense agents enters the intracellular environment.