We found that the downregulation of miR-145 appeared to be one of the earliest oncogenic events and demonstrated that miR-145 is the principal regulator of the premalignant BC phenotype characterized by downregulated IFN-STAT1/2 signaling and upregulated BC-related oncogenes, including c-Myc, Fascin, and PTBP1. Here, FSCN1 is linked to breast cancer.