Small Interfering Double-Stranded RNAs as Therapeutic Molecules to Restore Chemosensitivity to Thymidylate Synthase Inhibitor Compounds

John C. Schmitz, Tian Min Chen, Edward Chu

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

RNA interference is a post-transcriptional mechanism by which double-stranded RNA specifically silence expression of a corresponding gene. Small interfering double-stranded RNA (siRNA) of 21-23 nucleotides can induce the process of RNA interference. Studies from our laboratory have shown that translation of thymidylate synthase (TS) mRNA is controlled by its own protein end-product TS in a negative autoregulatory manner. Disruption of this process gives rise to increased synthesis of TS and leads to the development of cellular drug resistance to TS-targeted compounds. As a strategy to inhibit TS expression at the mRNA level, siRNAs were designed to target nucleotides 1058-1077 on human TS mRNA. Transfection of TS1058 siRNA into human colon cancer RKO cells resulted in a dose-dependent inhibition of TS expression with an IC50 value of 10 pM but had no effect on the expression of α-tubulin or topoisomerase I. Inhibition of TS expression by TS1058 was maximal at 48 h and remained suppressed for up to 5 days. Pretreatment of RKO cells with TS1058 siRNA suppressed TS protein induction following exposure to raltitrexed. In addition, TS1058 restored chemosensitivity of the resistant RKO-HTStet cell line to various TS inhibitor compounds. On treatment with TS1058, IC50 values for raltitrexed, 1843U89, and 5-fluoro-2′-deoxyuridine decreased by ∼15-16-fold. These studies suggest that TS-targeted siRNAs are effective inhibitors of TS expression and may have therapeutic potential by themselves or as chemosensitizers in combination with TS inhibitor compounds.

Original languageEnglish (US)
Pages (from-to)1431-1435
Number of pages5
JournalCancer research
Volume64
Issue number4
DOIs
StatePublished - Feb 15 2004
Externally publishedYes

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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