title: Systemic siRNA-mediated gene silencing: a new approach to targeted therapy of cancer.
abstract: OBJECTIVE
  RNA interference (RNAi), mediated by small interfering RNA (siRNA), silences genes with a high degree of specificity and potentially represents a general approach for molecularly targeted anticancer therapy. The aim of this study was to evaluate the ability of systemically administered siRNA to silence gene expression in vivo and to assess the effect of this approach on tumor growth using a murine pancreatic adenocarcinoma xenograft model.
  
  
  BACKGROUND
  Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is widely overexpressed in human gastrointestinal cancer. Overexpression of CEACAM6 promotes cell survival under anchorage independent conditions, a characteristic associated with tumorigenesis and metastasis.
  
  
  METHODS
  CEACAM6 expression was quantified by real-time polymerase chain reaction (PCR) and Western blot. Mice (n = 10/group) were subcutaneously xenografted with 2 x 10 BxPC3 cells (which inherently overexpress CEACAM6). Tumor growth, CEACAM6 expression, cellular proliferation (Ki-67 immunohistochemistry), apoptosis, angiogenesis (CD34 immunohistochemistry), and survival were compared for mice administered either systemic CEACAM6-specific or control single-base mismatch siRNA over 6 weeks, following orthotopic tumor implantation.
  
  
  RESULTS
  Treatment with CEACAM6-specific siRNA suppressed primary tumor growth by 68% versus control siRNA (P < 0.05) and was associated with a decreased proliferating cell index, impaired angiogenesis and increased apoptosis in the xenografted tumors. CEACAM6-specific siRNA completely inhibited metastasis (0% of mice versus 60%, P < 0.05) and significantly improved survival, without apparent toxicity.
  
  
  CONCLUSIONS
  Our data demonstrate the efficacy of systemically administered siRNA as a therapeutic modality in experimental pancreatic cancer. This novel therapeutic strategy may be applicable to a broad range of cancers and warrants investigation in patients with refractory disease.
authors.affiliation: Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Duxbury
authors.forename: Evan
authors.initials: E
authors.lastname: Matros
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Ito
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zinner
authors.forename: Stanley W
authors.initials: SW
authors.lastname: Ashley
authors.forename: Edward E
authors.initials: EE
authors.lastname: Whang
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000556:secondary / Q000628:therapy*; D000818:Animals; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic / Q000235:genetics; D000951:Antigens, Neoplasm / Q000235:genetics; D017209:Apoptosis / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D004195:Disease Models, Animal; D058851:GPI-Linked Proteins; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D018390:Gene Targeting; D015316:Genetic Therapy; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000628:therapy*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics*; D012878:Skin Neoplasms / Q000628:therapy; D014183:Transplantation, Heterologous
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000951:Antigens, Neoplasm; C504117:CEACAM6 protein, human; D015815:Cell Adhesion Molecules; D058851:GPI-Linked Proteins; D019394:Ki-67 Antigen; D034741:RNA, Small Interfering