TRIM66 confers tumorigenicity of hepatocellular carcinoma cells by regulating GSK-3β-dependent Wnt/β-catenin signaling

Tripartite motif 66 (TRIM66) protein, a member of the tripartite motif (TRIM) protein superfamily, has emerged as an oncogenic protein that is closely related to carcinogenesis in multiple cancers. However, whether TRIM66 plays a role in the progression of hepatocellular carcinoma (HCC) remains unknown. This study was aimed to investigate TRIM66 expression and its potential biological function in HCC cell lines. Here we showed that TRIM66 expression was significantly upregulated in HCC cell lines compared with normal control cells. Loss-of-function experiments by RNA interfering knockdown of TRIM66 showed that TRIM66 inhibition significantly reduced the proliferation, colony formation, and invasion of HCC cells, whereas gain-of-function by overexpression of TRIM66 exhibited the opposite effect. Further investigation showed that TRIM66 was involved in regulating glycogen synthase kinase-3 beta (GSK-3 beta) phosphorylation and beta-catenin expression. Knockdown of TRIM66 impeded the activation of Wnt signaling, while overexpression of TRIM66 promoted Wnt signaling activation. Moreover, inhibition of GSK-3 beta by specific inhibitor partially reversed TRIM66 inhibition-mediated antitumor effect, while knockdown of beta-catenin blocked the oncogenic effect of TRIM66 overexpression in HCC cells. Additionally, in vivo experiments using a xenograft tumor model showed that TRIM66 knockdown blunted the tumorigenicity of HCC cells associated with downregulation of beta-catenin expression. Overall, our results showed that TRIM66 functioned as an oncogenic protein in HCC by promoting the activation of Wnt/beta-catenin signaling. Our study suggests that TRIM66 is a potential target for HCC treatment.