SMURF1-mediated EFEMP1 ubiquitination reverses the resistance of HCC cells to sorafenib by promoting ferroptosis.

BACKGROUND

Acquired resistance to sorafenib remains a major obstacle to effectively treating advanced hepatocellular carcinoma (HCC). Ferroptosis has emerged as a key mechanism influencing therapeutic response. EGF-containing fibulin extracellular matrix protein 1 (EFEMP1) contributes to sorafenib resistance in HCC cells by regulating ferroptosis, but its upstream regulatory mechanisms remain elusive.

METHODS

Potential E3 ligases for EFEMP1 were screened using the UbiBrowser database. Protein interactions were validated by co-immunoprecipitation. The effects of SMAD ubiquitination regulatory factor 1 (SMURF1) and EFEMP1 on sorafenib sensitivity were assessed via IC50, colony formation, apoptosis, and migration/invasion assays. Assessment of ferroptosis was based on measuring levels of ROS, MDA, and iron, along with the expression of SLC7A11 and GPX4. The in vivo efficacy was demonstrated employing a xenograft mouse model.

RESULTS

SMURF1 could bind to and ubiquitinate EFEMP1, promoting its proteasomal degradation. Overexpression of SMURF1 in sorafenib-resistant HCC cells decreased EFEMP1 protein stability, reversed drug resistance, and suppressed malignant phenotypes, but these effects were rescued following EFEMP1 upregulation. Mechanistically, SMURF1-mediated EFEMP1 degradation activated ferroptosis, evidenced by increased ROS/MDA/iron and decreased SLC7A11/GPX4, which was also reversed by EFEMP1. In vivo, SMURF1 overexpression synergized with sorafenib to inhibit tumor growth, which was again reversed by EFEMP1.

CONCLUSION

This study demonstrates a novel SMURF1-EFEMP1-ferroptosis regulatory axis, wherein SMURF1 overcomes sorafenib resistance by ubiquitinating and degrading EFEMP1 to relieve its inhibition on ferroptosis. Targeting this axis presents a promising strategy for combating acquired resistance in HCC.