Abstract 2335: Thymoquinone induces the MUC4 mRNA-destabilizing activity of Tristetraprolin

Tristetraprolin (TTP) is an AU-rich element binding protein that destabilizes ARE-containing mRNAs. We previously reported that TTP suppresses several target genes such as those encoding proto-oncogenes and cytokines in various cancer cells. However, the signaling pathway to induce TTP expression is not well known. In this study, we investigate that Tymoquinone (TQ) which is an active ingredient derived from the medicinal plant Nigella satia induces the TTP mRNA and protein expression in AGS and MDA-MB231. TQ treatment destabilized a luciferase mRNA containing cIAP2, VEGF and MUC4 ARE. Transfected cells were treated with various kinds of MAPK inhibitors, treatment with Sorafenib (RAF inhibitor) and U0126 (MEK-1/2) reduced the TTP induction activity of TQ in a dose-dependent manner. We confirmed that co-treatment with sorafenib/U0126 and TQ also reduced TTP expression. Following TQ downregulated the expression of MUC4 in previous study, we next examined whether the changes of TTP expression affects the expression of MUC4. Overexpression of TTP decreased the stability of MUC4 mRNA and expression level of MUC4. On the contrary, inhibition of TTP using siRNA increased the MUC4 expression. MUC4 mRNA contains two AREs within the 3′UTR and TTP destabilized a luciferase mRNA containing MUC4 mRNA 3′UTR. Analyses of point mutants of MUC4 mRNA 3′UTR demonstrated that ARE2 were mostly responsible for the TTP mediated destabilization of MUC4 mRNA. Our data suggest that TQ enhances the mRNA and protein level of TTP via the modulation of the Raf-MEK MAPK signaling and suppressed cancer cell growth and promotion through destabilizing MUC4 mRNA as TTP novel target gene. Citation Format: Hyun Hee Lee, Se-Ra Lee, Sun-Hee Leem. Thymoquinone induces the MUC4 mRNA-destabilizing activity of Tristetraprolin. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2335. doi:10.1158/1538-7445.AM2014-2335