NFKB1 and breast cancer: Our findings in this study were that: (i) miR-214 is among the set of miRNAs that are significantly differentially expressed between canine and equine MDECs; (ii) increasing miR-214 levels or (iii) decreasing expression of the miR-214 target gene nuclear factor kappa B subunit 1 (NFKB1) prevents DMBA-induced apoptosis of equine MDECs; and (iv) miR-214-3p directly interacts with target gene UNC5A. Collectively, this work provides critical molecular insights into mechanisms in normal mammary epithelial cells that may confer resistance to mammary cancer.