Inhibition of P210BCR/ABL Expression in K562 Cells by Electroporation with an Antisense Oligonucleotide

We designed experiments to study the effects on P210BCR/ABL expression of introducing antisense oligonucleotides into K562 cells. We used two antisense oligonucleotides: one (AS1) is complementary to the first coding codon of the BCR/ABL mRNA and the two 5' and three 3' codons, and the other (AS2) to BCR coding codons 5 to 11 inclusive. To facilitate entry of the oligonucleotides the K562 cells were subjected to electroporation on three occasions at 24 hr intervals (0, 24 and 48 hr). P210BCR/ABL expression was assayed by in vivo phosphorylation followed by immune precipitation with a BCR antibody. Introduction of AS1 inhibited P210BCR/ABL expression at 72 and 96 hrs, whereas AS2 and the control oligonucleotide had no effect. AS1 also killed K562 cells. We conclude that selected antisense oligonucleotides can modify leukaemia-specific protein expression in K562 cells. This approach could prove valuable for purging CML bone marrow cells in vitro.