title: Targeted gene delivery in tumor xenografts by the combination of ultrasound-targeted microbubble destruction and polyethylenimine to inhibit survivin gene expression and induce apoptosis.
abstract: BACKGROUND
  Noninvasive and tissue-specific technologies of gene transfection would be valuable in clinical gene therapy. This present study was designed to determine whether it could enhance gene transfection in vivo by the combination of ultrasound-targeted microbubble destruction (UTMD) with polyethylenimine (PEI) in tumor xenografts, and illuminate the effects of gene silencing and apoptosis induction with short hairpin RNA (shRNA) interference therapy targeting human survivin by this novel technique.
  
  
  METHODS
  Two different expression vectors (pCMV-LUC and pSIREN) were incubated with PEI to prepare cationic complexes (PEI/DNA) and confirmed by the gel retardation assay. Human cervical carcinoma (Hela) tumors were planted subcutaneously in both flanks of nude mice. Tumor-bearing mice were administered by tail vein with PBS, plasmid, plasmid and SonoVue microbubble, PEI/DNA and SonoVue microbubble. One tumor was exposed to ultrasound irradiation, while the other served as control. The feasibility of targeted delivery and tissue specificity facilitated by UTMD and PEI were investigated. Moreover, immunohistochemistry analyses about gene silencing and apoptosis induction were detected.
  
  
  RESULTS
  Electrophoresis experiment revealed that PEI could condense DNA efficiently. The application of UTMD significantly increases the tissue transfection. Both expression vectors showed that gene expressions were present in all sections of tumors that received ultrasound exposure but not in control tumors. More importantly, the increases in transgene expression were related to UTMD with the presence of PEI significantly. Silencing of the survivin gene could induce apoptosis effectively by downregulating survivin and bcl-2 expression, also cause up-regulation of bax and caspase-3 expression.
  
  
  CONCLUSIONS
  This noninvasive, novel combination of UTMD with PEI could enhance targeted gene delivery and gene expression in tumor xenografts at intravenous administration effectively without causing any apparently adverse effect, and might be a promising candidate for gene therapy. Silencing of survivin gene expression with shRNA could be facilitated by this non-viral technique, and lead to significant cell apoptosis.
authors.affiliation: Department of Medical Ultrasound, The Third Affiliated Hospital of Guangzhou Medical University, PR China. winchen1408@126.com
authors.forename: Zhi-Yi
authors.initials: ZY
authors.lastname: Chen
authors.forename: Kun
authors.initials: K
authors.lastname: Liang
authors.forename: Ri-Xiang
authors.initials: RX
authors.lastname: Qiu
mesh_terms: D000818:Animals; D017209:Apoptosis; D004247:DNA / Q000008:administration & dosage; D015870:Gene Expression; D018390:Gene Targeting / Q000379:methods*; D015316:Genetic Therapy / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins; D051379:Mice; D008819:Mice, Nude; D045423:Microbubbles; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000235:genetics; D009374:Neoplasms, Experimental / Q000628:therapy*; D011094:Polyethyleneimine / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D000077022:Survivin; D014162:Transfection / Q000379:methods*; D014465:Ultrasonics; D023041:Xenograft Model Antitumor Assays
chemical_list: C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D000077022:Survivin; D011094:Polyethyleneimine; D004247:DNA