Target Protector PNA: a new tool in Cystic Fibrosis treatment

Cystic Fibrosis (CF) is the most common lethal genetic disorder among Caucasians. Several studies demonstrated that CF has been associated with the deregulation of specific microRNAs (miRNAs)[1]. Nowadays, the approaches to regulate a specific miRNA essentially use oligonucleotide (ON) analogues, which, being complementary to miRNAs, are able to reduce or inhibit their activity, leading to the control of gene expression. Recently, our group proposed the use of peptide nucleic acids (PNAs) as inhibitors of miR-509-3p, a miRNA involved in the pathological progress of Cystic Fibrosis[2]. In our previous works, two negatively charged PNAs, 14 and 7 bases long, conveniently modified at their termini to allow delivery and individuation within the cells, and complementary to the 5’-terminus of miR-509-3p, were proposed for the selective inhibition of the miRNA[3,4]. The in vitro studies demonstrated that both PNAs were able to recognize the target within the cells. Herein, we propose the synthesis and characterization of new PNA sequences, 13 and 7 bases long, complementary to a sequence within the promoter of the CFTR gene. Spectroscopic data confirm the ability of PNA sequences to bind their complementary DNA target by forming a stable PNA-DNA heteroduplexes, and preliminary biological studies show that the longest PNA sequence is able to counteract better the action of miRNA. This approach differs from the previous works, in which the gene was the target site of miRNA with the subsequent inhibition of the CFTR protein expression. The aim of our work is to clarify the role of PNAs as new therapeutic agents for all the CF cases characterized by mutations that do not completely abolish the protein function, with the final goal to improve or resolve a severe CF phenotype by virtue of the increased expression of the protein and the increased chloride flow