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

• Published in: The Journal of immunology (1950) Vol. 180; no. 11; pp. 7125 - 7133
• Main Authors: Armstrong, Michelle E, Gantier, Michael, Li, Lili, Chung, Wen Y, McCann, Amanda, Baugh, John A, Donnelly, Seamas C
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.06.2008
• Subjects: 2-Aminopurine - pharmacology; Breast Neoplasms - immunology; Breast Neoplasms - metabolism; Cell Line, Tumor; Cell Proliferation; eIF-2 Kinase - antagonists & inhibitors; eIF-2 Kinase - metabolism; Humans; Interferon-beta - immunology; Interferon-beta - metabolism; Macrophage Migration-Inhibitory Factors - biosynthesis; Macrophage Migration-Inhibitory Factors - genetics; Macrophage Migration-Inhibitory Factors - immunology; Poly I-C - genetics; Poly I-C - pharmacology; Respiratory syncytial virus; RNA Interference; RNA, Double-Stranded - immunology; RNA, Double-Stranded - metabolism; RNA, Small Interfering - immunology; RNA, Small Interfering - metabolism; RNA, Small Interfering - pharmacology; Transfection
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.180.11.7125

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.