Inhibition of cell adhesion to plastic substratum by phosphorothioate oligonucleotide.

Antisense oligonucleotides have been widely used to achieve specific inhibition of targeted gene expression. However, the mechanism of action is not well understood and in many systems sequence-independent effects occur. We have recently shown that chronic administration of an antisense c-myc phosphorothioate oligonucleotide can specifically inhibit expression of the c-myc protein and growth in human breast cancer cells. We now identify an additional effect of the same oligonucleotide on cell adhesion. Transient delivery through electroporation of 2.5 microM antisense-myc oligonucleotide to MCF-7 cells results in 85% inhibition of adhesion to plastic substratum within 24 h. Both the onset of this effect and the subsequent recovery occur without a change in cell viability, growth, or alteration of adhesion to Matrigel, collagen IV, laminin, or fibronectin. However, no parallel changes in c-myc mRNA or protein expression are detectable, suggesting that in this instance inhibition of adhesion caused by antisense-myc oligonucleotide may involve a mechanism independent of the target sequence.