Novel peptides are also being used as targeted drug delivery systems for breast cancer therapy and also for tumor imaging strategies. A telomerasederived peptide has been shown to increase the cytosolic delivery of macromolecules by heat shock mediated cell penetration. Other studies support the use of peptides as lead compounds for anti-cancer therapy. For example a yeast two-hybrid screening Epimedin-B has identified peptide aptamers which bind to Hsp70 and specifically inhibit chaperone activity, thereby increasing sensitivity to druginduced apoptosis. For the first time we have shown that a 14-mer peptide TPP derived from the native Hsp70 protein can specifically recognize and target tumor cells expressing the membrane form of Hsp70. Given the selective, but widespread, expression of memHsp70 on tumor cells, but not their non-malignant counterparts appropriately formulated TPP could offer a promising new clinically relevant small molecule for imaging and/or Epimedin-A specifically targeting tumors. TPP has advantages over other peptides that are currently being evaluated, as the latter are restricted to targeting specific receptors on specific types of tumor cells. Another potential advantage of TPP as a therapeutic vehicle is that memHsp70 is expressed on a large proportion of tumors and its expression on tumor cells can be induced/increased using relevant chemotherapeutic agents and radiation therapy. The proportion of patients to which the TPP can be administered can therefore be increased by standard therapies. Fluorescence microscopy has previously revealed the internalization of Hsp70 and granzyme B into the CT26 murine colon cancer cell line involves Rab and LAMP dependent vesicles, and we therefore anticipated that the internalization of TPP also involves an endosomal pathway which is associated with Rab proteins inside tumor cells. Endosomes are intracellular vesicles that are responsible for the transport of molecules between different intracellular compartments, and they can be described as early endosomes, late endosomes, and recycling endosomes. The endosomal vesicles are also linked to the endoplasmic reticulum and the trans-Golgi network.