USP10 Promotes Proliferation of Hepatocellular Carcinoma by Deubiquitinating and Stabilizing YAP/TAZ.

Yes-associated protein (YAP) and its paralog, transcriptional coactivator with PDZ-binding motif (TAZ), play pivotal roles in promoting the progression of hepatocellular carcinoma. However, the regulatory mechanism underpinning aberrant activation of YAP/TAZ in hepatocellular carcinoma remains unclear. In this study, we globally profiled the contribution of deubiquitinating enzymes (DUB) to both transcriptional activity and protein abundance of YAP/TAZ in hepatocellular carcinoma models and identified ubiquitin-specific peptidase 10 (USP10) as a potent YAP/TAZ-activating DUB. Mechanistically, USP10 directly interacted with and stabilized YAP/TAZ by reverting their proteolytic ubiquitination. Depletion of USP10 enhanced polyubiquitination of YAP/TAZ, promoted their proteasomal degradation, and ultimately arrested the proliferation of hepatocellular carcinoma in vitro and in vivo. Expression levels of USP10 positively correlated with the abundance of YAP/TAZ in hepatocellular carcinoma patient samples as well as in N-nitrosodiethylamine (DEN)-induced liver cancer mice models. Collectively, this study establishes the causal link between USP10 and hyperactivated YAP/TAZ in hepatocellular carcinoma cells and provides a rationale for potential therapeutic interventions in the treatment of patients with hepatocellular carcinoma harboring a high level of YAP/TAZ. SIGNIFICANCE: These findings identify USP10 as a DUB of YAP/TAZ and its role in hepatocellular carcinoma progression, which may serve as a potential therapeutic target for hepatocellular carcinoma treatment.

Zhu H ，Yan F ，Yuan T ，Qian M ，Zhou T ，Dai X ，Cao J ，Ying M ，Dong X ，He Q ，Yang B ... -  《-》

Simultaneous knockdown of YAP and TAZ increases apoptosis of hepatocellular carcinoma cells under hypoxic condition.

Hepatocellular carcinoma (HCC) is one of the common malignant tumors of the digestive system and its five-year survival rate is low. Hypoxia is an important feature of HCC, which can promote cell death resistance. However, the key regulator of HCC cell survival remains elusive in the hypoxic condition. Emerging researches have showed that the Hippo signaling pathway is involved in the initiation and progression of HCC. Here, we provide evidence that key downstream effectors YAP and its paralog TAZ play vital role in apoptosis resistance of HCC cells under hypoxia. Knockdown of YAP or TAZ does not affect the survival of HCC cells in normoxic and hypoxic microenvironment. In addition, the rate of apoptosis by knockdown or inhibition of both YAP and TAZ under hypoxic condition is largely higher than which under normoxia. In conclusion, simultaneous knockdown or inhibition of YAP and TAZ promote apoptosis of HCC cells dramatically. To our knowledge, this is the first research to explore the role of both YAP and TAZ in HCC hypoxic microenvironment in vitro and in vivo. Therefore, it may be useful for establishing novel targeted therapies of HCC, especially subtypes with plenty of hypoxic areas.

Yan B ，Li T ，Shen L ，Zhou Z ，Liu X ，Wang X ，Sun X ... -  《-》

Deubiquitinating enzyme USP10 promotes hepatocellular carcinoma metastasis through deubiquitinating and stabilizing Smad4 protein.

Hepatocellular carcinoma (HCC) has emerged as one of the most prevalent life-threatening cancers, and the high mortality rate is largely due to the metastasis. The sustained activation of Smad4 and transforming growth factor-β (TGF-β) is closely associated with advanced HCC metastasis. However, the regulatory mechanism underlying the aberrant activation of Smad4 and TGF-β pathway remains elusive. In this study, using a functional screen of USPs siRNA library, we identified ubiquitin-specific proteases USP10 as a deubiquitinating enzyme (DUB) that sustains the protein level of Smad4 and activates TGF-β signaling. Further analysis showed that USP10 directly interacts with Smad4 and stabilizes it through the cleavage of its proteolytic ubiquitination, thus promoting HCC metastasis. The suppression of USP10 by either shRNAs or catalytic inhibitor Spautin-1 significantly inhibited the migration of HCC cells, whereas the reconstitution of Smad4 was able to efficiently rescue this defect. Overall, our study not only uncovers the regulatory effect of USP10 on the protein abundance of Smad4, but also indicates that USP10 could be regarded as a potential intervention target for the metastatic HCC in Smad4-positive patients.

Yuan T ，Chen Z ，Yan F ，Qian M ，Luo H ，Ye S ，Cao J ，Ying M ，Dai X ，Gai R ，Yang B ，He Q ，Zhu H ... -  《-》

An Imbalance in TAZ and YAP Expression in Hepatocellular Carcinoma Confers Cancer Stem Cell-like Behaviors Contributing to Disease Progression.

Transcriptional coactivator with PDZ-binding motif (TAZ) and yes-associated protein (YAP) are equivalently placed downstream effectors of the Hippo pathway with oncogenic roles in human cancers. However, the expression profiles of TAZ/YAP differ depending on the cancer cell type, suggesting that these proteins have different roles during cancer progression, yet no studies have examined the biologic significance of the balance between TAZ and YAP expression levels. Here we examined the functional roles of TAZ/YAP in hepatocellular carcinoma progression. We found that TAZ, but not YAP, was predominantly expressed in HCC. TAZ knockdown under normal conditions attenuated cell growth in HCC cells; however, TAZ knockdown combined with 5-fluorouracil treatment significantly increased chemoresistance compared with control cells. Notably, TAZ knockdown induced compensatory YAP expression and was accompanied by upregulation of CD90, a HCC-specific cancer stem cell marker. Continuous treatment with 5-fluorouracil also induced YAP expression and promoted tumor formation in vivo. Conversely, double knockdown of TAZ/YAP reduced chemoresistance and tumorigenicity. Moreover, YAP knockdown aggravated HCC cell growth to a greater degree than TAZ knockdown, and YAP overexpression was strongly associated with poor prognoses in patients with HCC. Collectively, these studies demonstrate that TAZ and YAP exhibit different functional roles in cancer progression, and a shift to predominant YAP expression upon TAZ depletion conferred cancer stem cell-like properties including chemoresistance and tumorigenicity in HCC. Therefore, targeting of both TAZ/YAP will be required for a complete antitumor response in HCC.

Hayashi H ，Higashi T ，Yokoyama N ，Kaida T ，Sakamoto K ，Fukushima Y ，Ishimoto T ，Kuroki H ，Nitta H ，Hashimoto D ，Chikamoto A ，Oki E ，Beppu T ，Baba H ... -  《-》

The calcimimetic agent cinacalcet inhibits hepatocellular carcinoma via YAP/TAZ suppression.

Zheng L ，Du J ，Ge F ，Qian M ，Yang B ，He Q ，Weng Q ，Zhu H ... -  《PHARMAZIE》