ANTISENSE OLIGODEOXYRIBONUCLEOTIDES SUPPRESS HEMATOLOGIC CELL-GROWTH THROUGH STEPWISE RELEASE OF DEOXYRIBONUCLEOTIDES

Antisense oligodeoxyribonucleotides (ODNs) are now being extensively i nvestigated in an attempt to achieve cell growth suppression through s pecific targeting of genes related to cell proliferation, despite incr easing evidence of non-antisense cytotoxic effects. In the context of anti-BCR/ABL antisense strategies in chronic myeloid leukemia, we have reexamined the antiproliferative effect of phosphodiester and phospho rothioate ODNs on the leukemic cell line BV173 and on CD34(+) bone mar row cells in liquid culture. The 3' sequences of the ODNs determine th eir effect. At concentrations of 10 mu mol/L (for phosphorothioate ODN s) or 25 mu mol/L (for phosphodiester ODNs), all the tested ODNs exert an antiproliferative activity, except those that contain a cytosine r esidue at either their two most terminal 3' positions. We show that th is antiproliferative effect is due to the toxicity of the d-NMPs (5' m onophosphate deoxyribonucleosides), the enzymatic hydrolysis products of the ODNs inculture medium. The toxicity of the d-NMPs on hematologi c cells depends on their nature (d-CMP [2'deoxycytidine 5'-monophospha te] is not cytotoxic), on their concentration (d-GMP [2'-deoxyguanosin e 5'-monophosphate], TMP [thymidine 5'-monophosphate], and d-AMP [2'-d eoxyadenosine 5'-monophosphate] are cytotoxic at concentrations betwee n 5 and 10 mu mol/L), and on the coincident presence of other d-NMPs i n the culture medium (d-CMP neutralizes the toxicity of d-AMP, d-GMP, or TMP). The antiproliferative activity of ODNs is thus restricted to conditions where the 3' hydrolysis process by exonucleases generates s ignificant amounts of d-NMPs with a low proportion of d-CMP. Our resul ts reveal a novel example of a nonantisense effect of ODNs, which shou ld be taken into account when performing any experiment using assumed antisense ODNs. (C) 1997 by The American Society of Hematology.