Modification of Short Non-Permeable Peptides to Increase Cellular Uptake and Cytostatic Activity of Their Conjugates

Cell-penetrating peptides (CPPs) are well-known delivery vectors, oligoarginines are an important class of CPPs, which was modified to increase the cellular uptake and change the internalization mechanism. A minimum number of four Arg residues was used and tetrarginine sequence was modified by 4-((4-(dimethylamino)phenyl)azo)benzoic acid (Dabcyl) and Trp(s). The Dabcyl group was attached to the N-terminus, while peptides were different in the number and position of Trp in their sequence. Their internalization was studied on breast cancer cells (MCF-7 and MDA-MB-231), and Chinese hamster ovary cells (CHO) using different fluorescence techniques. Our most active CPPs, Dabcyl-RRWRRK and Dabcyl-WRRRRK were conjugated to antitumor drugs, resulting in considerable cytostatic activity, especially on MDA-MB-231 cell lines. These newly developed cell-penetrating tetrarginine derivatives may enter cells very efficiently, mainly by direct translocation and caveolae-mediated endocytosis, thus they may be promising delivery vehicle. Tetragrinines are considered inefficient CPPs, but with our modifications, we rendered them effective.