Synthesis of a stabilized 177Lu–siRNA complex and evaluation of its stability and RNAi activity. Issue 6 (June 2015)

• Record Type: Journal Article
• Authors: Fathi, Mojtaba; Yavari, Kamal; Taghikhani, Mohammad; Ghannadi Maragheh, Mohammad
• Is Part Of: Nuclear medicine communications. Volume 36:Issue 6(2015:Jun.)
• Publication Date: 2015-06
• Subjects: apoptosis -- colon cancer -- IGF-1R -- 177Lu -- modified siRNA; Nuclear medicine -- Periodicals; 616.07575
• DOI: 10.1097/MNM.0000000000000292
• Languages: English
• ISSNs: 0143-3636

Abstract

Abstract : Purpose: Serum and intracellular instability limits the therapeutic applications of short interfering RNA (siRNA) as a radiopharmaceutical. Chemical modifications like phosphorothioate (PS) substitution and 2′-O-methoxy (2′-O-Me) modifications could eliminate such limitations. In this study, the effects of PS and 2′-O-Me modifications at the backbone of siRNA on serum stability and RNA interference activity were investigated. Materials and methods: Fully PS and 2′-O-Me-modified type 1 insulin-like growth factor receptor (IGF-1R) siRNA was radiolabeled with lutetium-177 ( 177 Lu) through p-SCN-Bn-DTPA as a chelator. After purification with Vivaspin and PD-10 columns, the radiolabs were examined for stability in serum by instant thin-layer chromatography and polyacrylamide gel electrophoresis. The level of IGF-1R in response to the modified and labeled IGF-1R siRNA was examined using RT-PCR and ELISA assay in colon cancer cells. The effects of such siRNA on the prevention of proliferation of colon cancer cells and its apoptosis were investigated using MTT assay and Annexin-V/propidium iodide double staining, respectively. Cellular accumulation quantities of the labeled and modified IGF-1R siRNA were determined using a γ-counter by taking advantage of 177 Lu as a γ-emitter. Results: Both the modified 177 Lu–siRNA complex and the modified nonlabeled siRNA showed significant stability in serum. The levels of IGF-1R mRNA and protein significantly decreased with both the labeled and nonlabeled IGF-1R siRNAs, but no such reduction in IGF-1R was observed with luciferase siRNA ( P <0.01). Proliferation decreased significantly and apoptosis increased in the cells treated with modified 177 Lu–IGF-1R siRNA in comparison with either 177 Lu or labeled luciferase siRNA ( P <0.001). Conclusion: Uniform chemically modified siRNAs can form stable complexes with 177 Lu that pronounce its cytotoxic effect through apoptosis in colon cancer cells.