[概要] In the present study, we investigated the intracellular delivery of siRNA using synthetic peptides as transfection reagents and the silencing effect of siRNA targeting hTERT mRNA in 3 human cancer cell lines, Jurkat, HeLa and K562. The complex of siRNA and a specific amphiphilic peptide could be effectively taken up into cells. The complex also showed a high silencing effect against hTERT mRNA. Moreover, the combination of siRNA-NES conjugates and the amphiphilic peptides improved silencing effects up to 95.2%. The amphiphilic peptides and their hybrids showed almost no cyto-toxicity and protected siRNA against intracellular nuclease digestion in 10% FBS (half life time was over 48h).