Abstract Mortality in metastatic triple negative breast cancer (TNBC) remains high due to a lack of targeted therapy options. Consequently, there is a pressing need to identify prognostic markers and therapeutic targets for TNBC. Our group identified the DEAD-box RNA helicase DP103 as a novel prognostic biomarker and metastasis-driving oncogene enriched in TNBC. Aberrant Wnt/β-catenin signaling has been implicated for driving growth and metastasis of many cancers, like TNBC. Our studies found that the depletion of DP103 in metastatic TNBC cells resulted in decreased Wnt activity and expression of downstream Wnt target genes such as Axin2 and c-Myc. In addition, stimulation of the Wnt pathway via GSK3β inhibition or Wnt-3a recombinant protein significantly increased the transcriptional expression of DP103, indicating a possible positive feedback loop. To validate this new role for DP103 in regulating the Wnt/β-catenin signaling pathway in vivo, we developed a novel Drosophila stem cell and tumor model by generating a genetic mosaic of oncogenic Ras and β-catenin in Drosophila. The co-expression of these oncogenes caused benign tumor formation in Drosophila larval tissue that were visualized and used to identify key genetic modifiers necessary for growth and invasion into neighboring tissues. RX-5902, a novel Wnt/β-catenin modulator preventing the nuclear translocation of β-catenin via phosphorylated p68 decreased the transcriptional expression of DP103 and inhibited tumor formation as observed in our Drosophila model. Interestingly, overexpression of DP103 abrogated the effects of RX-5902, suggesting a requirement for RX-5902-mediated downregulation of DP103 to bring about anti-tumorigenic effects. Collectively, our data suggests a novel regulatory role for DP103 in the Wnt/β-catenin signaling pathway that is targetable by drugs like RX-5902. Citation Format: Bunnag N, Yuan Y, Cai W, Suresh J, Young Bok L, Deog Joong K, Tolwinski N, Kumar AP. Characterization of a novel prognostic and targetable modulator of the Wnt/β-catenin signaling pathway in breast cancers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-15.