OLIGONUCLEOTIDES COMPLEMENTARY TO C-MYB MESSENGER-RNA INHIBIT GROWTH AND INDUCE APOPTOSIS IN HUMAN BURKITT-LYMPHOMA CELLS

A 24-mer (antisense) phosphorothioate oligonucleotide (ODN) correspond ing to the codons 2-9 of the c-myb gene was evaluated for its effects on the growth of a human Burkitt lymphoma cell line (Raji) in vitro. R aji cells incubated with different concentrations of c-myb antisense O DN (5-15 mu g/ml) for 24-72 h showed a significant dose-dependent decr ease in growth. The same concentrations of control (sense) or scramble d c-myb phosphorothioate ODNs did not inhibit Raji cell growth. The c- myb antisense ODN, but not the control ODNs, significantly decreased c -myb mRNA levels in treated cells as determined by RT-PCR. Additionall y, the c-myb antisense ODN induced apoptosis of Raji cells as demonstr ated by i) flow cytometry to enumerate the A(o) (apoptotic cell popula tion) population of propidium iodide stained cells; ii) electron micro scopy to evaluate the cell morphology; and iii) DNA fragmentation patt ern. Thus, an antisense c-myb ODN causes significant growth inhibition of Burkitt lymphoma cells, and one mechanism of growth inhibition is the induction of apoptosis of the lymphoma cells. In addition, antisen se c-myb ODN did not reduce CFU-GM or BFU-e colony-forming ability of normal hematopoietic stem/progenitor cells. Because the inhibition is sequence-specific and Burkitt lymphoma cell selective, evaluation of t he therapeutic effects of c-myb antisense ODN against Burkitt lymphoma is warranted.