RAB40C recruiting TRIM21 facilitates the progression of hepatocellular carcinoma by stabilizing EGFR.

[BACKGROUND] RAB40C, a member of the Ras oncogene family, is an important regulator in cell signal transduction, cell growth and differentiation. Studies imply that it is a potentially pernicious factor in cancers, however, the correlation between RAB40C and hepatocellular carcinoma (HCC) progression is still not explored.

[METHODS] RAB40C expression and its clinical significance in HCC were analyzed using the Cancer Genome Atlas (TCGA) databases. The gene expression in liver tumor tissues was detected by western blot and quantitative real-time PCR. The effects of RAB40C in vitro and in vivo were evaluated by CCK8, colony formation, transwell assays and tumor xenograft. Mass spectrometry analysis, co-immunoprecipitation assay, ubiquitination modification was applied to revealed the potential mechanisms by which RAB40C regulates the progression of hepatocellular carcinoma. Virtual screening technology was used to find small molecule drugs targeting RAB40C.

[RESULTS] Our study demonstrated that RAB40C displayed oncogenic roles in promoting cell growth, tumorigenesis and migration of HCC cells by positively modulating of EGFR signaling. Mechanistically, we evaluated that RAB40C, one downstream target of STAT3, mediated K63-linked ubiquitination at Lys713 of EGFR by recruiting TRIM21, which led to increased stability of EGFR protein and sustained activation the downstream signaling of EGFR and conferring malignant capacities to HCC cells. Moreover, the drug artemisinin, selected by virtual screening, reduced the RAB40C expression, and effectively suppressed the viability of HCC cells and EGFR signaling.

[CONCLUSIONS] This research, we identified that RAB40C, an oncogene, was a target of STAT3 and boosted the malignant progression of HCC by regulation of EGFR cascades, and exerted a promising potential in HCC therapy.