title: Site-specific PEGylation endows a mammalian ribonuclease with antitumor activity.
abstract: Mammalian ribonucleases are emerging as cancer chemotherapeutic agents. Their cationicity engenders cell permeability, and their enzymatic activity destroys the biochemical information encoded by RNA. The pharmacologic potential of ribonucleases is, however, obviated by their high sensitivity to a cytosolic inhibitor protein (RI) and their small size, which limits their residence in serum. We reasoned that site specific conjugation of a poly(ethylene glycol) (PEG) chain could both reduce sensitivity to RI and increase serum half-life. We found that appending a PEG moiety can enable bovine pancreatic ribonuclease (RNase A) to evade RI, depending on the site of conjugation and the length and branching of the chain. Although a pendant PEG moiety decreases antiproliferative activity in vitro, PEGylation discourages renal clearance in vivo and leads to nearly complete tumor growth inhibition in a mouse xenograft model. These data demonstrate that a pendant PEG moiety can be beneficial to the action of proteins that act within the cytosol, and that strategic site-specific PEGylation can endow a mammalian ribonuclease with potent antitumor activity.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, WI, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Rutkoski
authors.forename: John A
authors.initials: JA
authors.lastname: Kink
authors.forename: Laura E
authors.initials: LE
authors.lastname: Strong
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Raines
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology*; D002417:Cattle; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003600:Cytosol; D004354:Drug Screening Assays, Antitumor; D004355:Drug Stability; D006207:Half-Life; D006801:Humans; D008297:Male; D051379:Mice; D010926:Placental Hormones / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000737:chemistry; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D010926:Placental Hormones; C022052:placental ribonuclease inhibitor; D011092:Polyethylene Glycols; D012259:Ribonuclease, Pancreatic