A novel antisense oligonucleotide targeting survivin expression induces apoptosis and sensitizes lung cancer cells to chemotherapy

Survivin, an inhibitor of apoptosis protein, deserves attention as a select ive target for cancer therapy because it lacks expression in differentiated adult tissues but is expressed in a variety of human tumors. We designed 2 0-mer phosphorothioate antisense oligonucleotides targeting different regio ns of survivin mRNA and investigated their ability to down-regulate survivi n mRNA and induce apoptosis in the lung adenocarcinoma cell line A549, Olig onucleotide 4003, which targets nucleotides 232-251 of survivin mRNA, was i dentified as the most potent compound. As measured by real-time PCR, 4003 d own-regulated survivin mRNA in a dose-dependent manner with an IC50 of 200 nM. Its maximum effect was achieved at a concentration of 400 nM, at which mRNA was downregulated by 70%, As revealed by increased caspase3-like prote ase activity, nuclear condensation and fragmentation, and trypan blue uptak e, treatment with 4003 induced apoptosis and sensitized tumor cells to the chemotherapeutic agent etoposide, Oligonucleotide 4003 did not reduce the v iability of normal blood leukocytes with marginal levels of survivin mRNA.