USP9X promotes apoptosis in cholangiocarcinoma by modulation expression of KIF1Bβ via deubiquitinating EGLN3

Abstract

Cholangiocarcinoma represents the second most common primary liver malignancy. The incidence rate has constantly increased over the last decades. Cholangiocarcinoma silent nature limits early diagnosis and prevents efficient treatment. Here we demonstrated that USP9X is downregulated in cholangiocarcinoma which contributes to tumorigenesis. The expression of USP9X in cholangiocarcinoma inhibited cell proliferation and colony formation in vitro as well as xenograft tumorigenicity in vivo. Clinical data demonstrated that expression levels of USP9X were positively correlated with favorable clinical outcomes. Mechanistic investigations further indicated that USP9X was involved in the deubiquitination of EGLN3, a member of 2-oxoglutarate and iron-dependent dioxygenases. USP9X elicited tumor suppressor role by preventing degradation of EGLN3. Importantly, knockdown of EGLN3 impaired USP9X-mediated suppression of proliferation. USP9X positively regulated the expression level of apoptosis pathway genes KIF1Bβ through EGLN3 thus involved in apoptosis of cholangiocarcinoma. Together, these findings help to understand that USP9X alleviates the malignant potential of cholangiocarcinoma through upregulation of EGLN3. Consequently, we provided novel insight into that USP9X is a potential biomarker or serves as a therapeutic or diagnostic target for cholangiocarcinoma.