Anticancer Effect of E26 Transformation-Specific Homologous Factor through the Induction of Senescence and the Inhibition of Epithelial–Mesenchymal Transition in Triple-Negative Breast Cancer Cells

SIMPLE SUMMARY: N-myc downstream-regulated gene 2 (NDRG2) is a tumor suppressor in breast cancer, and its expression is positively correlated with ETS homologous factor (EHF) expression. To determine the functional role of EHF in breast cancer cells, EHF was overexpressed in breast cancer cells, which resulted in growth retardation and an increased apoptotic rate by chemotherapeutic agent treatment. Moreover, cellular senescence was induced, and the migration ability was suppressed by EHF overexpression. Signal transducer and activator of transcription 3 (STAT3) signaling was also suppressed by EHF overexpression. The subcutaneous injection of 4T1-EHF cells into Balb/c mice resulted in smaller tumor sizes compared to 4T1-mock tumors, and pulmonary metastasis was also suppressed by EHF overexpression. Patients with a high EHF expression showed a better prognosis than patients with low EHF expression. These results suggest that EHF might be a tumor suppressor gene in breast cancer cells and might be a prognostic marker of breast cancer. ABSTRACT: The aim of the present study was to evaluate the effect of ETS homologous factor (EHF) in malignant breast cancer cells. The overexpression and knockdown of the EHF gene in human and mouse breast cancer cells were performed, and the TCGA dataset and Q-omics were analyzed. We found that the tumor suppressor NDRG2 is correlated with EHF gene expression in triple-negative breast cancer cells, that EHF overexpression results in reduced cell proliferation and that apoptosis is promoted by the chemotherapeutic reagent treatment of EHF-overexpressing cells. By EHF overexpression, senescence-associated β-galactosidase activity and p21(WAF1/CIP1) expression were increased, suggesting that EHF may induce cellular senescence. In addition, the overexpression of EHF reduced the migratory ability and inhibited epithelial–mesenchymal transition (EMT). Furthermore, EHF inhibited the phosphorylation of STAT3. The overexpression of EHF also reduced the tumor size, and lung metastasis in vivo. At the tumor site, β-galactosidase activity was increased by EHF. Finally, the Kaplan–Meier-plotter analysis showed that TNBC patients with a high expression of EHF had a longer relapse-free survival rate. Our findings demonstrated that EHF inhibits breast tumor progression by inducing senescence and regulating EMT in TNBC cells.