Deubiquitinating Enzyme USP9X Suppresses Tumor Growth via LATS Kinase and Core Components of the Hippo Pathway

Abstract

The core LATS kinases of the Hippo tumor suppressor pathway phosphorylate and inhibit the downstream transcriptional coactivators YAP and TAZ, which are implicated in various cancers. Recent studies have identified various E3 ubiquitin ligases that negatively regulate the Hippo pathway via ubiquitination, yet few deubiquitinating enzymes (DUB) have been implicated. In this study, we report the DUB USP9X is an important regulator of the core kinases of this pathway. USP9X interacted strongly with LATS kinase and to a lesser extent with WW45, KIBRA, and Angiomotin, and LATS co-migrated exclusively with USP9X during gel filtration chromatography analysis. Knockdown of USP9X significantly downregulated and destabilized LATS and resulted in enhanced nuclear translocation of YAP and TAZ, accompanied with activation of their target genes. In the absence of USP9X, cells exhibited an epithelial-to-mesenchymal transition phenotype, acquired anchorage-independent growth in soft agar, and led to enlarged, disorganized, three-dimensional acini. YAP/TAZ target gene activation in response to USP9X knockdown was suppressed by knockdown of YAP, TAZ, and TEAD2. Deletion of USP9X in mouse embryonic fibroblasts resulted in significant downregulation of LATS. Furthermore, USP9X protein expression correlated positively with LATS but negatively with YAP/TAZ in pancreatic cancer tissues as well as pancreatic and breast cancer cell lines. Overall, these results strongly indicate that USP9X potentiates LATS kinase to suppress tumor growth. Cancer Res; 77(18); 4921-33. Ó2017 AACR.

Deubiquitinase ubiquitin‐specific protease 9X regulates the stability and function of E3 ubiquitin ligase ring finger protein 115 in breast cancer cells

“…19,36,37 For example, elevated expression of USP9X has been documented in several types of human cancers, including non-small-cell lung cancer, esophageal squamous cell carcinoma, B-cell lymphoma, cervical carcinoma, and melanoma, and its high expression is closely linked with tumor growth, invasion, metastasis, and chemoresistance. 26,36,[38][39][40][41][42][43] Conversely, USP9X has tumor suppressor functions in pancreatic ductal adenocarcinoma 37,44,45 and colorectal cancer. 46 Interestingly, 2 recent studies showed that USP9X stabilizes large tumor suppressor kinase 2, an upstream component of the Hippo pathway, to negatively regulate YAP and its target genes to suppress tumor growth in pancreatic 44,45 and breast 44 cancer.…”

“…26,36,[38][39][40][41][42][43] Conversely, USP9X has tumor suppressor functions in pancreatic ductal adenocarcinoma 37,44,45 and colorectal cancer. 46 Interestingly, 2 recent studies showed that USP9X stabilizes large tumor suppressor kinase 2, an upstream component of the Hippo pathway, to negatively regulate YAP and its target genes to suppress tumor growth in pancreatic 44,45 and breast 44 cancer. In contrast, another study reported that USP9X deubiquitinates and stabilizes YAP1, a major downstream effector of the Hippo pathway, thus promoting breast cancer cell survival and chemoresistance.…”

Inhibition of Ubiquitin-Specific Proteases as a Novel Anticancer Therapeutic Strategy

“…Increased USP9X expression significantly up-regulates and stabilizes LATS and leads to a decrease in the transport of YAP/TAZ into the nucleus as well as inhibiting of their target genes. Furthermore, the expression level of USP9X is positively related to LATS expression but negatively associated with the expression of YAP/TAZ in multiple tumor tissues, such as pancreatic cancer and breast cancer, demonstrating that USP9X potentiates LATS kinase in suppressing tumor growth (Toloczko et al, 2017). …”

Ubiquitination‑deubiquitination in the Hippo signaling pathway (Review)

“…Overexpression of YOD1 leads to enhanced hepatocyte proliferation and hepatomegaly in a YAP-dependent manner in a transgenic mouse model, and a strong connection exists between YOD1 and YAP expression in patients with liver cancer, which implies that YOD1 may promote tumor initiation (155). In comparison, USP9X (FAM) deubiquitinates LATS kinases to suppress tumor growth (156). The DUB3 family of deubiquitinating enzymes, which includes 25 USP17-like proteins, was identified, using a short hairpin RNA-based screening technique, to be a mediator of YAP/TAZ activity (157,158).…”