Theantiproliferativ e activity ofc-mybandc-mycantisense oligonucleotides insmoothmusclecells iscausedbya nonantisense mechanism

Smoothmusclecell (SMC)proliferation is thought toplaya majorroleinvascular restenosis after angioplasty andisaserious complication oftheprocedure. Developing antisense (AS)oligonucleotides astherapeutics is attractive because ofthepotentially highspecificity ofbinding totheir targets, andseveral investigators havereported inhibition ofSMCproliferation invitro andinvivo byusing AS strategies. We report heretheresults ofourexperiments on vascular SMCsusingAS oligonucleotides directed toward c-mybandc-myc. Wefound thatsignificant inhibition ofSMC proliferation occurred withthese specific ASsequences but thatthisinhibition wasclearly notviaa hybridization- dependent ASmechanism. Rather, inhibition wasduetothe presence offourcontiguous guanosine residues intheoligo- nucleotide sequence. Thiswasdemonstrated invitro inpri- marycultures ofSMCsandinarteries exvivo. Theexvivo modeldeveloped hereprovides arapid andeffective system in which toscreen potential oligonucleotide drugs forrestenosis. We havefurther explored thesequence requirements ofthis non-ASeffect anddetermined thatphosphorothioate oligo- nucleotides containing atleast twosetsofthreeorfour consecutive guanosine residues inhibit SMC proliferation in vitro andexvivo. Theseresults suggest thatprevious ASdata obtained usingtheseandsimilar, contiguous guanosine- containing ASsequences bereevaluated andthat there maybe anadditional class ofnucleic acidcompounds thathave potential asantirestenosis therapeutics. A great dealofinterest hasbeenfocused onthepotential for developing humantherapeutics based onantisense (AS)phos- phorothioate oligonucleotide (oligo) strategies. Theelegant specificity ofWatson-Crick basepairing between theASoligo andthetarget mRNA orgenecould formthebasis forahighly specific andeffective drug. ASoligo drugs could bedesigned