Engrailed 2 facilitates progression of triple-negative and HER2-enriched breast cancer by binding to enhancer region of Tenascin-C.

Engrailed 2 (EN2) is a homeodomain-containing protein whose aberrant expression is observed in various cancer types, yet its role in breast cancer remains unclear. This study investigates the roles and mechanisms of EN2 in breast cancer progression. Using online dataset analysis, we assessed the correlation between EN2 expression and breast cancer progression and chemotherapeutic sensitivity. Functional assays, including RT-qPCR, Western blot, cell viability, transwell migration and invasion, spheroid formation, and flow cytometry, were conducted to explore EN2's role. Mechanistic insights were obtained through luciferase reporter assays, ChIP, and Caspase 3 activity detection. Our results showed that EN2 is highly expressed in breast cancer patients, negatively correlating with survival rates and positively with disease progression and reduced chemotherapy sensitivity. Functional experiments confirmed EN2's oncogenic role, and it was found to promote the expression of the oncogenic Tenascin-C (TNC) gene. Notably, EN2 directly interacts with the super-enhancer region within the TNC locus. Elevated TNC expression mitigated the effects of EN2 knockdown on breast cancer cell progression. Our study unveils a novel mechanism by which EN2 regulates the TNC locus super-enhancer, thereby activating oncogenic pathways in breast cancer.