Targeting heat shock proteins on cancer cells: selection, characterization, and cell-penetrating properties of a peptidic GRP78 ligand.
Peptidic ligands can be used for specific cell targeting and the delivery of payloads into the target cell. Here we describe the screening of a pool of cyclic peptide phage display libraries using whole-cell panning against human melanoma cell line Me6652/4. This strategy resulted in the selection of the cyclic 13-mer Pep42, CTVALPGGYVRVC, which showed preferential internalization into melanoma cell line Me6652/4 versus the reference cell line Me6652/56. This translocation is a receptor-mediated process that does not require electrostatic interactions nor does it involve transfer to the lysosomal compartment. The cellular receptor for Pep42 was identified as the surface membrane form of glucose-regulated protein 78 (GRP78), a member of the heat shock protein family and a marker on malignant cancer cells. The cellular uptake and intracellular trafficking of Pep42-Quantum Dot conjugates was monitored by confocal laser microscopy, and colocalization within the endoplasmic reticulum was observed. The uptake of Pep42 could be blocked by a monoclonal antibody against the identified receptor. Furthermore, Pep42 was shown to target specifically GRP78-expressing cancer cells. The in vitro cytotoxicity of a Pep42-Taxol conjugate was evaluated by flow cytometry wherein the conjugate was shown to induce apoptosis and was more effective in promoting programmed cell death in Me6652/4 cells. In summary, the data presented suggest that cyclic peptide Pep42 might be a powerful tool in the construction of drug conjugates designed to selectively kill malignant cancer cells.
Kim
Youngsoo
Y
The Skaggs Institute for Chemical Biology and Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Lillo
Antonietta M
AM
Steiniger
Sebastian C J
SC
Liu
Ying
Y
Ballatore
Carlo
C
Anichini
Andrea
A
Mortarini
Roberta
R
Kaufmann
Gunnar F
GF
Zhou
Bin
B
Felding-Habermann
Brunhilde
B
Janda
Kim D
KD
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D045744:Cell Line, Tumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008545:Melanoma / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017239:Paclitaxel / Q000494:pharmacology; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects
D000911:Antibodies, Monoclonal; D000972:Antineoplastic Agents, Phytogenic; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008024:Ligands; D018832:Molecular Chaperones; C513552:Pep42 peptide; D019151:Peptide Library; D010456:Peptides, Cyclic; D017239:Paclitaxel