E3 Ubiquitin Ligase TRIM47 Promotes Intrahepatic Cholangiocarcinoma Progression by Ubiquitinating Fumarate Hydratase and Modulating Macrophage Polarization

To explore potential biomarkers in the progression of intrahepatic cholangiocarcinoma (ICC), the gene expression profiles in ICC and paired normal tissues were analyzed using mRNA-sequencing. E3 ubiquitin ligase tripartite motif containing 47 (TRIM47) was found highly expressed in ICC tissues (Log 2 FC=2.473, p<0.001), which was also observed in seven ICC samples compared with paired normal tissues. Patients with higher TRIM47 expression exhibited shorter disease-free survival period. Functional studies indicated that TRIM47 knockdown in ICC cells suppressed cell growth in vitro and the tumorigenicity of tumor cells in vivo , whereas TRIM47 overexpression of had the opposite effect. Furthermore, after co-culture of TRIM47-silenced ICC cells and macrophages, the macrophages showed a reduction in M2 polarization bias. Cancer cells with TRIM47 downregulation were sensitive to macrophage cytotoxicity. Notably, the secretion of fumarate was reduced in TRIM47-silenced cancer cells, and the treatment of dimethyl fumarate, a derivative of fumarate, reversed the effect of TRIM47 downregulation on M2 polarization in macrophages. Through IP-LC/MS analysis, we obtained 1166 binding partners of TRIM47 in ICC cells. Among those partners, fumarate hydratase (FH), a catalytic enzyme for fumarate metabolism, was bound with TRIM47. Knockdown of TRIM47 increased the protein half-life of FH from 1.33 h to 2.25 h. Overexpression of TRIM47 reduced the protein expression of FH and increased its ubiquitination. FH overexpression restored the effects of TRIM47. Collectively, the observations demonstrate that TRIM47 accelerates the progression of ICC by interacting with FH and ubiquitinating FH, indicating that TRIM47/FH axis may be potential target for ICC treatment.