Inhibition Of Ubiquitin-Specific Protease 34 (Usp34) Regenerates Mammary Glands Via Induction Of Epithelial-Mesenchymal Transition (Emt) And Stemness

Mammary stem cells (MaSCs) possess specific biological properties including self-renewal capacity and the ability to differentiate into two primary cell lineages; luminal cells and myoepithelial cells. Epithelial-mesenchymal transition (EMT) is a key process during mammary gland development. Recent study demonstrates that ubiquitin-specific protease 34 (USP34), as a member of the USP family plays a critical role in Wnt/b-catenin signaling pathway. Our objective was to investigate possible roles of USP34 on induction of EMT and properties of mammary epithelial stem cells as well as mammary gland regeneration. We observed that USP34 level was relatively lower in mesenchymal-like phenotype MDA-MB-231 and 4T1 cells, compared to epithelial-like phenotype cells. Inhibition of USP34 induced EMT in NMuMG cells, which was accompanied with upregulation of EMT markers, such as N-cadherin, phospho-smad3, snail and active-β-catenin as well as downregulation of E-cadherin. NMuMG cells exhibited a typical epithelial phenotype with an absence of invasive behavior, while USP34 knockdown NMuMG cells acquired an invasive property. This observation was associated with a significant increased MMP2 level. Furthermore, inhibition of USP34 promotes stemness as evidenced by increased mammosphere-forming ability, concomitant with upregulation of Nanog, Oct4 and Sox2 mRNA levels in NMuMG cells. To examine the importance observations of our in vitro studies physiologically, the CTL-KD or USP34-KD cells were transplanted into the cleared mammary fat pads (CFP), and then mammary gland regeneration was observed for 10 months. Our in vivo data showed that USP34-KD cells regenerated elongated ductal branching and TEB of mammary gland in CFP. Our findings suggest that USP34 may be potentially involved in development of mammary glands. Citation Format: Eunhye Oh, Daeil Sung, Yoon-Jae Kim, Tae-Min Cho, Seojin Jang, Ji Young Kim, Jae Hong Seo. Inhibition of ubiquitin-specific protease 34 (USP34) regenerates mammary glands via induction of epithelial-mesenchymal transition (EMT) and stemness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-311.