Biological activity and delivery of peptide nucleic acids (PNA)-DNA chimeras for transcription factor decoy (TFD) pharmacotherapy.

Peptide nucleic acids (PNAs) are recently described DNA mimics, in which the sugar-phosphate backbone is replaced by N-(2-aminoethyl)glycine units. These molecules efficiently hybridize with complementary DNA, forming Watson-Crick double helices. In addition, the interest of PNAs and PNA-based analogs is related to the fact that they are resistant to DNases and proteinases. While applications of PNAs as antisense and antigéne molecules in non-viral gene therapy are well documented, their effects as potential transcription factor decoy (TFD) molecules is not demonstrated. PNA/PNA and PNA/DNA duplex are not suitable for TFD. In fact, PNA/PNA duplex does not recognize transcription factors, while, in the case of PNA/DNA hybrids containing nuclear factor binding sites, the interaction with transcription factors is unstable. By sharp contrast, double stranded molecules based on PNA-DNA chimeras exhibit strong TFD activity, display enzymatic stability in serum and cellular extracts and can be delivered to target cells after complexation with liposomes and microspheres. The TFD molecules based on PNA-DNA chimeras can be further engineered by addition of short peptides facilitating cell penetration and nuclear localization. Therefore, these engineered molecules could be of great interest for in vivo experiments on non-viral gene therapy of a variety of diseases, including neoplastic and viral diseases, for which the TFD approach has been already demonstrated as a very useful strategy.