title: Targeting pancreatic islets with phage display assisted by laser pressure catapult microdissection.
abstract: Heterogeneity of the microvasculature in different organs has been well documented by multiple methods including in vivo phage display. However, less is known about the diversity of blood vessels within functionally distinct regions of organs. Here, we combined in vivo phage display with laser pressure catapult microdissection to identify peptide ligands for vascular receptors in the islets of Langerhans in the murine pancreas. Protein database analyses of the peptides, CVSNPRWKC and CHVLWSTRC, showed sequence identity to two ephrin A-type ligand homologues, A2 and A4. Confocal microscopy confirmed that most immunoreactivity of CVSNPRWKC and CHVLWSTRC phage was associated with blood vessels in pancreatic islets. Antibodies recognizing EphA4, a receptor for ephrin-A ligands, were similarly associated with islet blood vessels. Importantly, binding of both islet-homing phage and anti-EphA4 antibody was strikingly increased in blood vessels of pancreatic islet tumors in RIP-Tag2 transgenic mice. These results indicate that endothelial cells of blood vessels in pancreatic islets preferentially express EphA4 receptors, and this expression is increased in tumors. Our findings show in vivo phage display and laser pressure catapult microdissection can be combined to reveal endothelial cell specialization within focal regions of the microvasculature.
authors.affiliation: Departments of Genitourinary Medical Oncology and Cancer Biology, The University of Texas, M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
authors.forename: Virginia J
authors.initials: VJ
authors.lastname: Yao
authors.forename: Michael G
authors.initials: MG
authors.lastname: Ozawa
authors.forename: Martin
authors.initials: M
authors.lastname: Trepel
authors.forename: Wadih
authors.initials: W
authors.lastname: Arap
authors.forename: Donald M
authors.initials: DM
authors.lastname: McDonald
authors.forename: Renata
authors.initials: R
authors.lastname: Pasqualini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002986:Clinical Trials as Topic; D019992:Databases as Topic; D004210:Dissection; D036382:Ephrin-A1 / Q000737:chemistry; D006801:Humans; D007150:Immunohistochemistry; D007515:Islets of Langerhans / Q000378:metabolism* / Q000473:pathology; D007834:Lasers; D008024:Ligands; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008833:Microcirculation; D018613:Microscopy, Confocal / Q000379:methods*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D017433:Protein Structure, Secondary; D012984:Software
chemical_list: D036382:Ephrin-A1; D008024:Ligands; D019151:Peptide Library; D010455:Peptides; D019408:Platelet Endothelial Cell Adhesion Molecule-1