Cell-penetrating peptides in protein mimicry and oligonucleotide delivery Applications and mechanisms

Abstract: The plasma membrane functions as a barrier, restricting entry of hydrophilic pharmaceutical agents. Cell-penetrating peptides (CPPs) are capable of transporting bioactive cargos into the cell and have consequently been extensively investigated for their mechanism of entry and capability to deliver various cargos spanning from peptides to plasmids.The main aim of this thesis was to investigate the mechanism and capability of some of these CPPs to deliver mainly oligonucleotides and peptides into the cell. Oligonucleotides in the form of ds DNA decoy for sequestering of transcription factors or PNAs for redirection of splicing. In addition, peptides derived from the interaction interface of a tumor suppressor protein were investigated for their potential to combine a biological effect with internalization.Peptides with or without any cargo were predominantly dependent on some form of endocytic mechanism for internalization, substantiated by using a functional assay, where all tested CPPs were associated with endocytosis for delivery of splice correcting PNAs. A new CPP, M918 proved most efficient in promoting splice correction and internalized mainly via macropinocytosis. In addition, TP10 efficiently delivered dsDNA decoy oligonucleotides for sequestering of the transcription factor Myc with a concomitant biological response, i.e. reduced proliferation. Finally, for the first time, to our knowledge, a novel pro-apoptotic peptide with cell-penetrating properties was designed from the tumor suppressor p14ARF, which decreased proliferation and induced apoptosis in cancer cell-lines, potentially mimicking the full-length protein. Altogether, this thesis highlights the functionality of CPPs and the possibility to develop new CPPs with improved or new properties, having the potential to advance delivery of therapeutic compounds.