TAT Modification of Alpha-Helical Anticancer Peptides to Improve Specificity and Efficacy

HPRP-A1 is an amphipathic a-helical anticancer peptide (ACP) derived from the N-terminus of ribosomal protein L1 (RpL1) of Helicobacter pylori. In our previously study, HPRP-A1 has been reported that induced HeLa cell apoptosis in a caspase-dependent approach and involved both by the death receptor 'extrinsic' pathway and the mitochondria 'intrinsic' pathway. Here we report the construction of a new hybrid peptide, HPRP-A1-TAT, comprising the cell-permeating peptide TAT linked to the C-terminus of HPRP-A1. This peptide exhibits higher anticancer activity against HeLa cells with lower toxicity against human RBC than HPRP-A1. Two FITC-labeled peptides, FITC-HPRP-A1 and FITC-HPRP-A1-TAT, were used to investigate and compare the cellular uptake mechanism using fluorescence spectra and flow cytometry. Compared with HPRP-A1, HPRP-A1-TAT quickly crossed cell, entered the cytoplasm via endocytosis, and disrupted the cell membrane integrity. HPRP-A1-TAT exhibited stronger anticancer activity than HPRP-A1 at the same concentration by increasing early apoptosis of HeLa cells and inducing caspase activity. Notably, after 24 h, the cellular concentration of HPRP-A1-TAT was higher than that of HPRP-A1. This result suggests that TAT protects HPRP-A1 against degradation, likely due to its high number of positively charged amino acids or the further release of peptides into cancer cells from endocytotic vesicles. We believe that this TAT modification approach may provide an effective new strategy for improving the therapeutic index and anticancer activity of ACPs for clinical use.