title: Internalization of indium-labeled LDL through a lipid chelating anchor in human pancreatic-cancer cells as a potential radiopharmaceutical for tumor localization.
abstract: Low-density lipoproteins (LDL) labeled with indium via a lipid-chelating agent, the bis(stearylamide) of diethylenetri-aminepentaacetic acid (L), were evaluated as a potential radiopharmaceutical (111In-L-LDL) for tumor localization by studying their internalization in human pancreatic cancer cells (Capan-1). Using Dil-LDL (1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine perchlorate-LDL), this cell line was shown to bind human LDL with a high-affinity saturable component and a low-affinity non-saturable (40%) component. The single saturable high-affinity binding site had a KD of 27.5 +/- 2.1 micrograms/ml and a maximal binding of 610 +/- 7.5 ng/ml protein. Electron-microscopic examination of the In-L-LDL particles revealed the peripheral distribution of the electron-dense indium atoms at the outer surface of LDL. The modified LDL were then shown to be internalized by the cells. After conjugation of In-L-LDL to colloidal gold to follow the different stages of internalization, electron-microscopic examination showed that the In-L-LDL gold conjugates were stuck to the external sheet of the plasma apical and microvilli membrane, into earlier and later endosomes and into multivesicular bodies, suggesting the penetration of the In-L-LDL particles into lysosomal vacuoles. The observation of In-L-LDL-gold conjugates in deep-seated cytoplasm suggests that LDL could be employed as a drug-transport vehicle for targeting cytotoxics or radionuclides close to the cell nucleus.
authors.affiliation: Laboratoire de Synthèse, Physico-Chimie et Radiobiologie, Université Paul Sabatier, Toulouse, France.
authors.forename: P
authors.initials: P
authors.lastname: Urizzi
authors.forename: J P
authors.initials: JP
authors.lastname: Souchard
authors.forename: C
authors.initials: C
authors.lastname: Palevody
authors.forename: G
authors.initials: G
authors.lastname: Ratovo
authors.forename: E
authors.initials: E
authors.lastname: Hollande
authors.forename: F
authors.initials: F
authors.lastname: Nepveu
mesh_terms: D002232:Carbocyanines / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D006801:Humans; D007205:Indium Radioisotopes / Q000493:pharmacokinetics*; D008077:Lipoproteins, LDL / Q000493:pharmacokinetics*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D014407:Tumor Cells, Cultured / Q000378:metabolism
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; D007205:Indium Radioisotopes; D008077:Lipoproteins, LDL; D019275:Radiopharmaceuticals; C072024:carbocyanine dye DiIC12(3)