Penetratin, a 16-mer Drosophila Antennapedia derived peptide, like TAT, crosses the biological membranes and is transported to the nucleus of the cells. The interaction between penetratin (P16; RQIKIWFQNRRMKWKK) and phospholipid bicelles mimicking biological membranes was studied by NMR spectroscopy. The secondary structure and positioning studies confirmed the two tryptophan residues (48W and 56W) as the most important amino acids required for cellular internalization . The P16 or its shortened variant P7 (RRMKWKK) has been utilized to promote cellular uptake of impermeable targeting peptides such as G7-18NATE. Antitumor efficacy and translocation across the BBB of liposomes or liposome encapsulated drugs (doxorubicin and erlotinib) were evaluated using the in vitro BBB and intracranial glioblastoma xenograft models. Dual conjugation of penetratin and transferrin to liposomes (Tf-Pen-Lipo) significantly enhanced the BBB translocation. In addition, doxorubicin/erlotinib containing Tf-Pen-Liposomes very significantly accumulated in tumors, inhibited tumor growth, and prolonged survival rate when compared to the free drugs.