OTU domain-containing protein 3 (OTUD3), a deubiquitinating enzyme, has been shown to participate in progression of multiple malignancies. The accurate function of OTUD3 in hepatocellular carcinoma (HCC) progression remains elusive. We found that OTUD3 was significantly overexpressed in HCC, and higher OTUD3 expression was correlated with larger tumor size, more distant metastasis, and worse TNM stage. A series of gain-and loss-of-function assays were also performed to examine the oncogenic function of OTUD3 in promoting HCC cell growth and metastasis in vitro. Using a xenograft mouse model, we showed that OTUD3 accelerated HCC progression in vivo. Furthermore, alpha-actinin 4 (ACTN4) was identified as a downstream target of OTUD3 through mass spectrometry analysis, and the ACTN4 protein level was significantly related to OTUD3 expression. Additionally, OTUD3 directly bound with ACTN4 and deubiquitinated ACTN4 to stabilize it. Finally, ACTN4 was found to be essential for OTUD3-mediated HCC proliferation and metastasis in vitro and in vivo. Collectively, our findings identify the oncogenic role of OTUD3 in HCC and suggest that OTUD3 can be considered as a pivotal prognostic biomarker and a potential therapeutic target.

Deubiquitinating enzyme OTU domain‐containing ubiquitin aldehyde‐binding proteins 1 (OTUB1) has been shown to have an essential role in multiple carcinomas. However, the function of OTUB1 in papillary thyroid cancer (PTC) and the underlying mechanisms regulating PTC cells proliferation remain poorly understood. In this study, OTUB1 was significantly upregulated in papillary thyroid carcinoma tissues and cells. Through in vitro and in vivo experiments, knockdown of OTUB1 suppressed PTC cells growth whereas OTUB1 overexpression enhanced the proliferation ability of PTC cells. Moreover, the eyes absent homologue 1 (EYA1) was recognized as a potential target of OTUB1 through mass spectrometry analysis, and we further verified that EYA1 protein level was positively correlated with OTUB1 expression in PTC cells and clinical samples. Mechanistically, OTUB1 could interact with EYA1 directly and deubiquitinate EYA1 to stabilize it. At last, EYA1 was found to play an essential role in OTUB1‐derived PTC cells growth. Overall, our investigation reveals that OTUB1 is a previously unrecognized oncogenic factor in PTC cells proliferation and suggests that OTUB1 might be a novel therapeutic target in PTC.

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Background: OTUD3, a deubiquitinating enzyme, has emerged as important role in some cancer. It showed that OTUD3 plays suppressive role in breast cancer whereas oncogenic role in lung cancer. However, the function and mechanism of OTUD3 in hepatocellular carcinoma (HCC) progression remain elusive. Methods: Gene and protein expression of OTUD3 in HCC tissues were determined by qRT-PCR, western blot and immunohistochemistry. A series of gain- and loss-of-function assays were used to investigated the role of OTUD3 in HCC cells progression. Moreover, mass spectroscopic analysis and RNA-seq were used to identify the downstream targets of OTUD3 in HCC cells. The interaction between OTUD3 and ACTN4 was examined through co-IP experiment and in vitro ubiquitination assay.Results: In our research, OTUD3 was significantly overexpressed in HCC tissues and higher OTUD3 expression was correlated with bigger tumor size, more distant metastasis, and worse TNM stage. Additionally, OTUD3 promoted HCC cells growth and metastasis in vitro and in vivo. Furthermore, ACTN4 was identified as a downstream target of OTUD3 and ACTN4 protein level was significantly related to OTUD3 expression. Rescue experiments indicated that ACTN4 was essential for OTUD3-mediated HCC proliferation and metastasis in vitro and in vivo. Moreover, we identified that NF-κB signaling pathway was activated by OTUD3 through ACTN4 to promote HCC cells progression. Importantly, OTUD3 protein level was correlated with ACTN4 protein level and activity of NF-κB signaling pathway in HCC tissues. Conclusion: Our findings identify the oncogenic role of OTUD3 in HCC and suggest that OTUD3 can be considered as a pivotal prognostic biomarker and a potential therapeutic target.