E3 ubiquitin ligase RNF180 reduces sensitivity of triple-negative breast cancer cells to Gefitinib by downregulating RAD51

Background: Gefitinib (Gef) is an EGFR inhibitor and its resistance in triple negative breast Cancer (TNBC) is a critical concern. E3 ubiquitin ligases are pivotal for mediation of TNBC metastasis. However, the role of E3 ubiquitin Ligase Ring Finger Protein 180 (RNF180) in EGFR inhibitor resistance of TNBC remains unclear. This study was performed to investigate how the E3 ubiquitin protein Ligase RNF180 manipulated the growth, metastasis, and resistance to Gef of TNBC cells.

Methods: TNBC tissues were harvested for detection of RNF180 and RAD51 expression. Gef-resistant cell lines were constructed. Next, gain- and loss-of-function assays were implemented in TNBC cell lines and Gef-resistant cell lines, followed by assessment of TNBC cell biological processes. IP assay was performed to detect the interaction between RNF180 and RAD51. Drug resistance-related genes (MRP1, BCRP, and MDR1) were evaluated by Western blot and RT-qPCR. The tumorigenesis was performed in nude mice to observe the growth and metastasis of TNBC in vivo.

Results: RAD51 was highly expressed in TNBC tissues and cells, while RNF180 was poorly expressed. Mechanistically, RNF180 degraded RAD51 by ubiquitination. Overexpression of RNF180 or silencing of RAD51 suppressed proliferation, invasion, migration, and Gef resistance of TNBC cells and accelerated their Apoptosis. Upregulation of RNF180 or downregulation of RAD51 diminished tumorigenesis and Gef resistance of TNBC in mice.

Conclusion: RNF180 degraded RAD51 by ubiquitination, thereby inhibiting TNBC cell growth and metastasis and sensitizing TNBC cells to Gef.