title: Multivalent cyclic RGD conjugates for targeted delivery of small interfering RNA.
abstract: We have designed, synthesized, and tested conjugates of chemically modified luciferase siRNA (Luc-siRNA) with bi-, tri-, and tetravalent cyclic(arginine-glycine-aspartic) (cRGD) peptides that selectively bind to the αvβ3 integrin. The cellular uptake, subcellular distribution, and pharmacological effects of the cRGD-conjugated Luc-siRNAs compared to those of unconjugated controls were examined using a luciferase reporter cassette stably transfected into αvβ3 positive M21(+) human melanoma cells. The M21(+) cells exhibited receptor-mediated uptake of cRGD-siRNA conjugates but not of unconjugated control siRNA. The fluorophore-tagged cRGD-siRNA conjugates were taken up by a caveolar endocytotic route and primarily accumulated in cytosolic vesicles. The bi-, tri-, and tetravalent cRGD conjugates were taken up by M21(+) cells to approximately the same degree. However, there were notable differences in their pharmacological effectiveness. The tri- and tetravalent versions produced progressive, dose-dependent reductions in the level of luciferase expression, while the bivalent version had little effect. The basis for this divergence of uptake and effect is currently unclear. Nonetheless, the high selectivity and substantial "knock down" effects of the multivalent cRGD-siRNA conjugates suggest that this targeting and delivery strategy deserves further exploration.
authors.affiliation: Division of Molecular Pharmaceutics, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
authors.forename: Md Rowshon
authors.initials: MR
authors.lastname: Alam
authors.forename: Xin
authors.initials: X
authors.lastname: Ming
authors.forename: Michael
authors.initials: M
authors.lastname: Fisher
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Lackey
authors.forename: Kallanthottathil G
authors.initials: KG
authors.lastname: Rajeev
authors.forename: Muthiah
authors.initials: M
authors.lastname: Manoharan
authors.forename: Rudy L
authors.initials: RL
authors.lastname: Juliano
mesh_terms: D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D015195:Drug Design; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D008156:Luciferases; D008546:Melanoma, Experimental / Q000188:drug therapy; D058990:Molecular Targeted Therapy / Q000379:methods*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000008:administration & dosage*; D014162:Transfection
chemical_list: D039302:Integrin alphaVbeta3; D010456:Peptides, Cyclic; D034741:RNA, Small Interfering; C507169:cyclic arginine-glycine-aspartic acid peptide; D008156:Luciferases