Systematic in vitro evaluation of survivin directed antisense oligodeoxynucleotides in bladder cancer cells

Purpose: The rather poor responses to conventional treatment for bladder cancer (BCa) require novel, specific therapy approaches. The down-regulation of BCa associated genes may represent a new option to inhibit specifically BCa cell growth and induce cell death. Survivin, an apoptosis inhibitor that is up-regulated in the majority of malignancies, including BCa, provides an attractive target for molecular therapies, such as treatment with specific antisense oligode-oxynucleotides (AS-ODNs). Materials and Methods: We used mRNA secondary structure prediction to design survivin directed AS-ODNs. After lipid mediated transfection with 30 selected antisurvivin AS-ODN inhibitory effects on cell growth properties as well as on survivin expression were measured. Results: Three of 30 tested constructs reproducibly impaired the growth characteristics of 4 BCa cell lines. Detailed analysis of the cell line EJ28 treated with the constructs SVV261, SVV264 and SVV286 revealed a clear decrease in viability (down to 35%) and long-term proliferation (down to 14%), which were caused by cell cycle arrest and an increase in apoptosis (from 19.5% to 51.3% maximum). The inhibition of tumor cell growth was associated with up to 60% to 80% survivin expression down-regulation. Interestingly all 3 evolved AS-ODNs were directed against the putative single strand survivin mRNA motif between 274 to 285 nucleotides, identified by secondary structure prediction. The reported accessibility of this motif to other nucleic acid based inhibitors such as ribozymes and small interfering RNAs emphasizes the rationale of a systematic selection of mRNA target sites. Conclusions: The survivin directed AS-ODNs shown to inhibit effectively the proliferation of BCa cells in the current study may provide suitable adjuvant therapeutic agents for the specific local treatment of BCa.