title: Confirming the RNAi-mediated mechanism of action of siRNA-based cancer therapeutics in mice.
abstract: siRNAs that specifically silence the expression of cancer-related genes offer a therapeutic approach in oncology. However, it remains critical to determine the true mechanism of their therapeutic effects. Here, we describe the preclinical development of chemically modified siRNA targeting the essential cell-cycle proteins polo-like kinase 1 (PLK1) and kinesin spindle protein (KSP) in mice. siRNA formulated in stable nucleic acid lipid particles (SNALP) displayed potent antitumor efficacy in both hepatic and subcutaneous tumor models. This was correlated with target gene silencing following a single intravenous administration that was sufficient to cause extensive mitotic disruption and tumor cell apoptosis. Our siRNA formulations induced no measurable immune response, minimizing the potential for nonspecific effects. Additionally, RNAi-specific mRNA cleavage products were found in tumor cells, and their presence correlated with the duration of target mRNA silencing. Histological biomarkers confirmed that RNAi-mediated gene silencing effectively inhibited the target's biological activity. This report supports an RNAi-mediated mechanism of action for siRNA antitumor effects, suggesting a new methodology for targeting other key genes in cancer development with siRNA-based therapeutics.
authors.affiliation: Tekmira Pharmaceuticals Corporation, 100-8900 Glenlyon Parkway, Burnaby, British Columbia, Canada.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Judge
authors.forename: Marjorie
authors.initials: M
authors.lastname: Robbins
authors.forename: Iran
authors.initials: I
authors.lastname: Tavakoli
authors.forename: Jasna
authors.initials: J
authors.lastname: Levi
authors.forename: Lina
authors.initials: L
authors.lastname: Hu
authors.forename: Anna
authors.initials: A
authors.lastname: Fronda
authors.forename: Ellen
authors.initials: E
authors.lastname: Ambegia
authors.forename: Kevin
authors.initials: K
authors.lastname: McClintock
authors.forename: Ian
authors.initials: I
authors.lastname: MacLachlan
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics; D004195:Disease Models, Animal; D020440:Gene Duplication; D015316:Genetic Therapy; D051379:Mice; D009369:Neoplasms / Q000235:genetics* / Q000628:therapy*; D009374:Neoplasms, Experimental / Q000235:genetics / Q000473:pathology; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D000097869:Polo-Like Kinase 1