To explore the roles of transcription factor E26 transformation-specific 1 (ETS1) and F-box protein 45 (FBXO45) in invasion and metastasis in hepatocellular carcinoma cells and the potential molecular mechanism.

Jaspar, hTFtarget and Cistrome transcription factor database prediction websites were used to predict the transcription factors of FBXO45. According to the intersection of the predicted results of each database, the expression of FBXO45 was detected after the candidate transcription factors were knockdown in HCCLM3 and Huh7 liver cancer cells, respectively. The most significant influence on FBXO45 expression was selected for further analysis, and chromatin immunoprecipitation assay (ChIP) was used to verify the binding to the FBXO45 promoter. Finally, the potential transcription factor of FBXO45 was identified. The effect of ETS1 overexpression on invasion and migration in HCCLM3 and Huh7 cells was detected by Transwell assay, and the expression levels of epithelial-mesenchymal transition (EMT) pathway proteins were detected by Western blot assay. The effects of FBXO45 knockdown on the invasion and migration under the condition of overexpression of ETS1 were also studied.

Intersection of FBXO45 transcription factors identified 3 candidate transcription factors, ETS1, SPI1 and YY1. When the 3 transcription factors were knocked down in HCCLM3 and Huh7 cells, respectively, ETS1 knockdown significantly reduced the expression of FBXO45. According to the analysis of The Cancer Genome Atlas (TCGA) data and the Gene Expression Omnibus (GEO) data, the expression levels of ETS1 and FBXO45 were significantly positively correlated (R=0.31, P<0.000 1; R=0.40, P=0.021 9). ChIP suggested that ETS1 could specifically bind to FBXO45 promoter sequence to regulate its expression, confirming that ETS1 was a potential transcription factor of FBXO45. After overexpression of ETS1 in HCCLM3 and Huh7 cells, the invasion and migration abilities of cells were significantly enhanced, and the expression of N-cadherin and Snail was up-regulated(P<0.01). In addition, in the case of ETS1 overexpression, FBXO45 knockdown significantly inhibited the invasion and migration(P<0.01).

ETS1 activates the transcription of FBXO45 and leads its high expression, which enhances the invasion and migration of HCC cells via EMT pathway and promotes the progression of hepatocellular carcinoma.