title: In vivo tumor imaging using a novel RNAi-based detection mechanism.
abstract: A new concept of tumor imaging is introduced using a siRNA-based probe that is capable of amplifying a specific endogenous fluorescence emission in cancerous tissue. In previous studies, we demonstrated a significant downregulation of Ferrochelatase (FECH) mRNA-expression in colorectal carcinomas leading to the accumulation of protoporphyrin IX (PpIX), a fluorescent metabolite of the heme synthesis. In this article, we report on first in vivo experiments in xenografted nude mice using folate-coupled liposomes or dendritic polyglycerolamine nanoparticles carrying ferrochelatase-siRNA to enhance PpIX-derived fluorescence in the tumor tissue. Tiny tumor foci could be monitored by the emission of PpIX fluorescence in vivo. Due to the omnipresence of the heme synthesis pathway, targeted application of ferrochelatase-siRNA may provide a general means for molecular imaging.
  
  
  BACKGROUND
  A new concept of tumor imaging is presented in this paper using a siRNA-based probe detecting protoporphyrin IX (PpIX), a fluorescent metabolite of the heme synthesis previously demonstrated to accumulate in cancer tissue.
authors.affiliation: Research Group Surgical Oncology, Experimental and Clinical Research Center, Charité Campus Buch, Berlin, Germany.
authors.forename: Kayiu
authors.initials: K
authors.lastname: Wan
authors.forename: Bernd
authors.initials: B
authors.lastname: Ebert
authors.forename: Jan
authors.initials: J
authors.lastname: Voigt
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.forename: Yiyang
authors.initials: Y
authors.lastname: Dai
authors.forename: Rainer
authors.initials: R
authors.lastname: Haag
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kemmner
mesh_terms: D000818:Animals; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D005294:Ferrochelatase / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D053758:Nanoparticles; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009368:Neoplasm Transplantation; D011524:Protoporphyrins / Q000235:genetics / Q000378:metabolism; D015347:RNA Probes / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D014183:Transplantation, Heterologous
chemical_list: D009363:Neoplasm Proteins; D011524:Protoporphyrins; D015347:RNA Probes; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C028025:protoporphyrin IX; D005294:Ferrochelatase