2'-OMe-phosphorodithioate-modified siRNAs show increased loading into the RISC complex and enhanced anti-tumour activity.

Wu SY, Yang X, Gharpure KM, Hatakeyama H, Egli M, McGuire MH, Nagaraja AS, Miyake TM, Rupaimoole R, Pecot CV, Taylor M, Pradeep S, Sierant M, Rodriguez-Aguayo C, Choi HJ, Previs RA, Armaiz-Pena GN, Huang L, Martinez C, Hassell T, Ivan C, Sehgal V, Singhania R, Han HD, Su C, Kim JH, Dalton HJ, Kovvali C, Keyomarsi K, McMillan NA, Overwijk WW, Liu J, Lee JS, Baggerly KA, Lopez-Berestein G, Ram PT, Nawrot B, Sood AK
Nat Commun. 2014 5: 3459

PMID: 24619206 · PMCID: PMC4112501 · DOI:10.1038/ncomms4459

Improving small interfering RNA (siRNA) efficacy in target cell populations remains a challenge to its clinical implementation. Here, we report a chemical modification, consisting of phosphorodithioate (PS2) and 2'-O-Methyl (2'-OMe) MePS2 on one nucleotide that significantly enhances potency and resistance to degradation for various siRNAs. We find enhanced potency stems from an unforeseen increase in siRNA loading to the RNA-induced silencing complex, likely due to the unique interaction mediated by 2'-OMe and PS2. We demonstrate the therapeutic utility of MePS2 siRNAs in chemoresistant ovarian cancer mouse models via targeting GRAM domain containing 1B (GRAMD1B), a protein involved in chemoresistance. GRAMD1B silencing is achieved in tumours following MePS2-modified siRNA treatment, leading to a synergistic anti-tumour effect in combination with paclitaxel. Given the previously limited success in enhancing siRNA potency with chemically modified siRNAs, our findings represent an important advance in siRNA design with the potential for application in numerous cancer types.

MeSH Terms (11)

Animals Cell Line, Tumor Female Humans Immunohistochemistry Mice Mice, Nude Phosphates RNA, Small Interfering RNA-Induced Silencing Complex Xenograft Model Antitumor Assays

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