title: Tumor-targeted delivery of polyethylene glycol-conjugated D-amino acid oxidase for antitumor therapy via enzymatic generation of hydrogen peroxide.
abstract: Hydrogen peroxide (H(2)O(2)) is a strong oxidant that induces apoptosis of tumor cells in vitro. Here, we investigated the antitumor activity of an H(2)O(2)-generating enzyme, D-amino acid oxidase (DAO), and its conjugate with polyethylene glycol (PEG; PEG-DAO). Compared with DAO, PEG-DAO showed improved pharmacokinetic parameters in mice after i.v. injection. PEG-DAO administered i.v. accumulated selectively in tumor tissue with insignificant accumulation in normal organs and tissues. To generate cytotoxic H(2)O(2) at the tumor site, PEG-DAO was first administrated i.v. to tumor-bearing mice. After an adequate lag time, the substrate of DAO, D-proline, was injected i.p. This treatment resulted in significant suppression of tumor growth compared with tumor growth in control animals (not given treatment; P < 0.001). Similar treatment with native DAO showed no effect under the same conditions. Oxidative metabolites were significantly increased in solid tumors by administration of PEG-DAO followed by D-proline (P < 0.002, compared with the group receiving no treatment), as evidenced by thiobarbituric acid-reactive substance assay. This treatment did not affect results from the metabolites in the liver and kidney. These findings suggest that tumor-targeted delivery of DAO is accomplished by using pegylated enzyme and thereby taking advantage of the enhanced permeability and retention effect in solid tumor. PEG-DAO thus delivered together with D-proline produces remarkable antitumor activity via extensive generation of H(2)O(2).
authors.affiliation: Department of Microbiology, Kumamoto University School of Medicine, Honjo 2-2-1, Kumamoto 860-0811, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Fang
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sawa
authors.forename: Takaaki
authors.initials: T
authors.lastname: Akaike
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maeda
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D003605:D-Amino-Acid Oxidase / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D016503:Drug Delivery Systems; D005079:Excipients / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics; D006207:Half-Life; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008297:Male; D051379:Mice; D011092:Polyethylene Glycols / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D011392:Proline / Q000494:pharmacology; D013552:Swine; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
chemical_list: D005079:Excipients; D017392:Thiobarbituric Acid Reactive Substances; D011092:Polyethylene Glycols; D011392:Proline; D006861:Hydrogen Peroxide; D003605:D-Amino-Acid Oxidase