Abstract Objectives. Aberrant Notch signaling promotes melanoma progression, yet the underlying molecular mechanism remains largely unknown. We hypothesized a potential involvement of epigenetic mechanism in this process and sought to identify Notch-regulated miRNAs and their functional targets. Methods. Notch-regulated miRNAs were identified by examining miRNA profiles in response to Notch activation/inhibition in human melanoma cells using RT2-miRNAArray. The role of specific miRNA in mediating the oncogenic effect of the Notch signaling was studied by testing whether alteration of miRNA expression could reverse the Notch's effects on melanoma cell growth, survival and colony-formation in vitro, and lung metastasis in vivo. The targets of the Notch-regulated miRNA were identified by searching miRNA target database and validated by immunoblot. The roles of miRNA targets in mediating the Notch's oncogenic effects were further assessed by in vitro colony-formation and in vivo lung metastasis assays. Results. Notch activation down-regulated mi143 in melanoma cells. Reconstituted expression of mi143 antagonized Notch1's oncogenic effect. The anti-oncogenic effect of mi143 is mediated by inhibiting Notch1-induced expression of FGF-1, uPA and uPAR since expression of these targets was up-regulated by the Notch1 activation while down-regulated by reconstituted overexpression of mi143. Supplementation of exogenous FGF-1 or reconstituted expression of uPA/uPAR, but not uPA alone, reversed the suppressive effect of mir143 on Notch-enhanced melanoma cells colony formation in soft-agar or lung metastasis in SCID mice. Conclusions. Notch activation up-regulates expression of FGF-1, uPA and uPAR through down-regulating mi143 expression in melanoma cells. mi143 is responsible for mediating aberrant Notch signaling-driven melanoma progression. The effect of down-regulated mi143 is transmitted through elevated FGF-1 and enhanced uPA-uPAR signaling activity, but not enzyme activity of uPA. This study unveils novel Notch1/mi143/FGF-1 and Notch1/mi143/uPA-uPAR cascades and uncovers an epigenetic mechanism underlying the oncogenic effect of Notch signaling, and provides potential novel targets for melanoma prognosis and therapy. Note: This abstract was not presented at the meeting. Citation Format: Ling Yin, Qinghua Huang, Alan S. Livingstone, Omaida C. Velazquez, Zhao-Jun Liu. Epigenetic regulation of Notch1 signaling-driven melanoma progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 193. doi:10.1158/1538-7445.AM2015-193