RNFT2 promotes malignancy of triple-negative breast cancer and predicts poor outcomes

Triple-negative breast cancer (TNBC) is a subtype of breast cancer, and has a high recurrence rate. RING finger transmembrane-domain containing protein 2 (RNFT2) is a RING-finger E3 ubiquitin ligase that exerts oncogene functions in multiple malignant tumors such as bladder cancer and gastric cancer. However, RNFT2's role in TNBC is still unclear. Here, we investigated RNFT2's function and mechanism in TNBC. RNFT2 expressions in different stages of breast cancer were evaluated using the Gene Expression Profiling Interactive Analysis database. Overall survival (OS) in TNBC patients with high RNFT2 expressions was assessed with the Kaplan-Meier plotter database. Meanwhile, RNFT2 expressions in TNBC cells and tissues were determined using Western blot and quantitative real-time PCR. The relationship between RNFT2 and TNBC patients' OS rates was examined with Kaplan-Meier curve analysis. The correlation between RNFT2 expressions and TNBC clinicopathological data was estimated by the chi-square test. Moreover, RNFT2 functions in TNBC were determined using loss-of-function assay, Cell Counting Kit-8 analysis, Transwell, and tube formation assay. Furthermore, RNFT2's mechanism in TNBC was evaluated by prediction software, dual-luciferase reporter assay, and rescue experiments. Additionally, RNFT2's roles in TNBC in vivo were identified with cell-derived xenograft, hematoxylin-eosin staining, and immunohistochemical assays. RNFT2 was elevated in breast cancer, and owned different degrees of overexpression in breast cancer at different stages. Meanwhile, OS of TNBC patients with high RNFT2 expressions was poor. Also, RNFT2 expressions were positively correlated with size, TNM stage, and lymph node metastasis of TNBC. Functionally, silencing RNFT2 repressed TNBC cell proliferation, invasion, and angiogenesis. Mechanistically, miR-211-5p targeted RNFT2, and RNFT2 was negatively regulated by miR-211-5p in TNBC cells. Rescue assays further validated that miR-211-5p overexpression restrained TNBC cell proliferation, invasion, and angiogenesis, yet these impacts were abolished after RNFT2 overexpression. Meanwhile, animal experimental data further implied that RNFT2 knockdown reduced TNBC cell proliferation in vivo. RNFT2 facilitated TNBC development and predicted its adverse outcomes.