title: Small interfering RNAs induce macrophage migration inhibitory factor production and proliferation in breast cancer cells via a double-stranded RNA-dependent protein kinase-dependent mechanism.
abstract: Small interfering RNAs (siRNAs) represent a novel tool to induce gene silencing in mammalian cells and clinical trials are currently ongoing to assess the therapeutic efficacy of siRNAs in various human diseases, including age-related macular degeneration and respiratory syncytial virus infection. However, previously reported off-target, nonspecific effects of siRNAs, including activation of type I IFNs and proinflammatory cytokines, remain an outstanding concern regarding use of these agents in vivo. Macrophage-migration inhibitory factor (MIF) is a pleiotropic cytokine with well-described roles in cell proliferation, tumorigenesis, and angiogenesis and represents a target gene for siRNA-based therapy in the treatment of breast cancer. However, in this study we describe an increase in MIF production from mammary adenocarcinoma (MCF-7) cells following transfection with MIF siRNA and various control siRNAs. This effect was shown to be dose-dependent and was attenuated in the presence of a double-stranded RNA-dependent protein kinase inhibitor, 2-aminopurine. Furthermore, treatment of MCF-7 cells with poly(I:C) also stimulated a PKR-dependent increase in MIF production from MCF-7 cells. The biological consequence of the siRNA-induced increase in MIF production from MCF-7 cells was a PKR-dependent increase in proliferation of breast cancer cells. Furthermore, in cDNAs prepared from a primary human breast cancer cohort, we demonstrated a significant correlation (Spearman rank correlation coefficient, r = 0.50, p < 0.0001, n = 63) between PKR- and MIF-mRNA expression. In conclusion, this study highlights the potential biological consequences of off-target, nonspecific effects of siRNAs and underlines the safety concerns regarding the use of siRNAs in the treatment of human diseases, such as cancer.
authors.affiliation: School of Medicine and Medical Science, College of Life Sciences, University College Dublin Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Armstrong
authors.forename: Michael
authors.initials: M
authors.lastname: Gantier
authors.forename: Lili
authors.initials: L
authors.lastname: Li
authors.forename: Wen Y
authors.initials: WY
authors.lastname: Chung
authors.forename: Amanda
authors.initials: A
authors.lastname: McCann
authors.forename: John A
authors.initials: JA
authors.lastname: Baugh
authors.forename: Seamas C
authors.initials: SC
authors.lastname: Donnelly
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology; D001943:Breast Neoplasms / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D016899:Interferon-beta / Q000276:immunology / Q000378:metabolism; D008263:Macrophage Migration-Inhibitory Factors / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D011070:Poly I-C / Q000235:genetics / Q000494:pharmacology; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000276:immunology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D014162:Transfection; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D008263:Macrophage Migration-Inhibitory Factors; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D015075:2-Aminopurine; D016899:Interferon-beta; D019892:eIF-2 Kinase; D011070:Poly I-C