RNA Interference of Interferon Regulatory Factor-1 Gene Expression in THP-1 Cell Line Leads to Toll-Like Receptor-4 Overexpression/Activation As Well As Up-modulation of Annexin-II

• Published in: Neoplasia (New York, N.Y.) Vol. 9; no. 12; pp. 1012 - 1020
• Main Authors: Maratheftis, Christos I., Giannouli, Stavroula, Spachidou, Maria P., Panayotou, George, Voulgarelis, Michael
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2007; Elsevier
• Subjects: Amino Acid Sequence; Annexin A2 - biosynthesis; Annexin A2 - genetics; Annexin II; Apoptosis; bcl-2-Associated X Protein - biosynthesis; bcl-2-Associated X Protein - genetics; Bone Marrow Cells - metabolism; Bone Marrow Cells - pathology; Cells, Cultured - drug effects; Cells, Cultured - metabolism; Gene Expression Regulation - drug effects; Humans; Intercellular Adhesion Molecule-1 - biosynthesis; Intercellular Adhesion Molecule-1 - genetics; Interferon Regulatory Factor-1 - antagonists & inhibitors; Interferon Regulatory Factor-1 - genetics; Interferon Regulatory Factor-1 - physiology; IRF-1; Leukemia, Promyelocytic, Acute - metabolism; Leukemia, Promyelocytic, Acute - pathology; Molecular Sequence Data; Monocytes - metabolism; myelodysplastic syndrome; Myelodysplastic Syndromes - metabolism; Myelodysplastic Syndromes - pathology; Protein Structure, Tertiary; RNA Interference; RNA, Messenger - genetics; RNA, Small Interfering - pharmacology; RNAi; TLR-4; Toll-Like Receptor 4 - biosynthesis; Toll-Like Receptor 4 - genetics; Transfection; IFN; TLR-4; RNAi; Annexin II; MS; IRF-1; siRNA; myelodysplastic syndrome; MS/MS; MDS; LPS; PCR
• ISSN: 1476-5586; 1476-5586; 1522-8002
• DOI: 10.1593/neo.07640

Interferon regulatory factor-1 (IRF-1) is a candidate transcription factor for the regulation of the Toll-like receptor-4 (TLR-4) gene. Using a small interfering RNAbased (siRNA) process to silence IRF-1 gene expression in the leukemic monocytic cell line THP-1, we investigated whether such a modulation would alter TLR-4 expression and activation status in these cells. The siIRF-1 cells expressed elevated levels of TLR-4 mRNA and protein compared to controls by 90% and 77%, respectively. ICAM.1 protein expression and apoptosis levels were increased by 8.35- and 4.25-fold, respectively. The siIRF-1 cells overexpressed Bax mRNA compared to controls. Proteomic analysis revealed upmodulation of the Annexin-II protein in siIRF-1 THP-1 cells. Myelodysplastic syndrome (MDS) patients with an absence of full-length IRF-1 mRNA also overexpressed Annexin-II. It is plausible that this overexpression may lead to the activation of TLR-4 contributing to the increased apoptosis characterizing MDS.