CircEML1 upregulates BTG2 to suppress the progression of triple-negative breast cancer

Accumulating evidence has demonstrated the significant involvement of circular RNAs (circRNAs) in breast cancer pathogenesis. Among these, triple-negative breast cancer (TNBC) presents a particular therapeutic challenge. However, the specific biological functions and underlying molecular mechanisms of circRNAs in this aggressive subtype remain largely unexplored. circEML1 was explored by GEO database analysis. Expression of circEML1 in TNBC cells and tissues were evaluated using quantitative real-time PCR and in situ hybridization. The effects of circEML1 on TNBC proliferation and metastasis were assessed via in vitro and in vivo functional experiments. The underlying mechanisms were investigated using RNA immunoprecipitation, dual-luciferase reporter, fluorescence in situ hybridization and rescue experiments. circEML1 was downregulated in TNBC cells and tissues. Expression of circEML1 was correlated with lymph node invasion, clinical stage and overall survival in TNBC patients. Functionally, overexpression of circEML1 inhibited the growth and metastasis of TNBC cells both in vitro and in vivo. Mechanistically, circEML1 acted as a molecular sponge for miR-21, thereby relieving its inhibitory effect on BTG2, then suppressed the tumorigenesis of TNBC. circEML1 inhibits TNBC progression by regulating the miR-21/BTG2 axis and may provide a novel prospective anticancer strategy for TNBC.