Abstract C141:In vitroandin vivocharacterization of two novel β‐catenin RNA antagonists, EZN‐3889 and 3892

Background: β‐Catenin is an important signaling molecule in the Wnt pathway that plays a key role in tumorgenesis. In the absence of Wnt signaling, the cytoplasmic level of β‐catenin is kept low due to rapid proteasomal‐mediated degradation of GSK3β phosphorylated β‐catenin. Activation of Wnt signaling leads to the inactivation of GSK3β, resulting in stabilization and accumulation of β‐catenin in the cytoplasm. Consequently, β‐catenin translocates into the nucleus, where it binds with members of the T‐cell factor (Tcf)/lymphocyte enhancer‐binding factor family of transcription factors and activates the expression of many target genes important for cancer development. Most colon cancers have activating mutations in the APC tumor suppressor or in β‐catenin itself. Furthermore, activating β‐catenin mutations have been found in a variety of other tumors such as melanomas, hepatocellular carcinomas, skin, breast, and prostate cancer, whereas β‐catenin is not activated in most normal tissues. Therefore, inhibition of β‐catenin is likely to have therapeutic effects in many cancers. We report here the identification of two β‐catenin LNA‐based mRNA‐antagonists, EZN‐3889 and EZN‐3892. Material and Methods:In vitro, the ability of the compounds to inhibit mRNA, cell growth, and reporter gene were evaluated by qRT‐PCR, MTS, and luciferase assays respectively, in multiple cell lines. In vivo, β‐catenin mRNA down‐modulation in liver and human tumors, which were grown on the flank of nude mice, was evaluated after intravenous administration of the compounds. Results: These molecules were potent down‐modulators of β‐catenin (IC50 = 0.1 to 3 nM) as well as protein (> 80% at 20 nM) of multiple cell lines, when transfected into tumor cells. Growth inhibition appeared to correlate with the status of either APC mutation or activating β‐catenin mutations, suggesting that β‐catenin is the driver of cancer cells. Interestingly, we found that these two antagonists specifically down modulated β‐catenin mRNA and protein effectively in multiple cell lines with a long‐lasting effect in the absence of any tranfection reagent. In mice, both molecules significantly down modulated β‐catenin mRNA in the liver. Conclusions: β‐catenin antagonists potently and specifically inhibited β‐catenin mRNA expression both in vitro and in vivo after intravenous injection. Further studies will examine the antitumor efficacy of the compounds. hese novel agents specifically inhibit a transcription factor that has been difficult to target with conventional agents. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C141.