Resistance of Decoy PNA-DNA Chimeras to Enzymatic Degradation in Cellular Extracts and Serum

Double-stranded molecules based on peptide nucleic acids (PNAs)-DNA chimeras carrying binding sites for known transcription factors could be of great interest in decoy pharmacotherapy of neoplastic diseases. For instance, decoy molecules recognizing Sp1 and NF-κB transcription factors were found to inhibit tumor cell growth and invasion activity. In this respect, we have recently found that double-stranded PNA-DNA chimeras carrying NF-κB binding sites inhibit the binding of NF-κB p52 and p50 transcription factors to target DNA molecules. In this article we determined the resistance of double-stranded decoy molecules based on PNA-DNA chimeras to exonucleases (both 3′→5′ and 5′→3′ exonucleases), endonucleases, and 5′-phosphatases. In addition, we performed experiments aimed at determining the resistance of these molecules in cellular extracts and serum. Finally, we used liposomes as protective agents in experimental conditions in which the decoy molecules employed were found to be unstable (high concentrations of enzymes, cellular extracts, or serum). The results obtained demonstrated that decoy molecules based on PNA-DNA chimeras are more resistant than DNA-based decoys to exo- and endonucleases, serum, and cellular extracts. In addition, the resistance of DNA/PNA hybrids in the presence of high concentrations of serum and cellular extracts was increased after complexation to cationic liposomes, due to the fact that double-stranded PNA-DNA-PNA chimeras bind to these delivery systems. The results obtained in the present study support the proposal of molecules based on PNA-DNA chimeras for an efficient decoy treatment of tumor cells both in vitro and in vivo.