STAT1 Mediates the Transcription of CircIFI30 and Promotes the Progression of Triple-Negative Breast Cancer by Up-Regulating CDCA4.

Signal transducers and activators of transcription 1 (STAT1) is an important transcription factor that regulates the growth, survival, differentiation and apoptosis of various tumor cells. However, the biological roles of STAT1 and potential mechanisms in triple-negative breast cancer (TNBC) remain largely unknown. The expression levels of STAT1, CircIFI30, CDCA4, and epithelial-mesenchymal transition (EMT)-associated molecules (MM2, MMP9, E-cadherin, and N-cadherin) were evaluated using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Furthermore, cell-counting kit-8 assay, Transwell assay, flow cytometry, and immunofluorescence staining were performed to investigate the biological functions of STAT1 and CircIFI30 in TNBC cells. In addition, Dual luciferase activity assay and chromatin immunoprecipitation qPCR were used to predict the interaction between STAT1 and CircIFI30 promoter. The effects of CircIFI30 on the stability of CDCA4 mRNA were also confirmed in further function study. Up-regulation of STAT1 was detected in TNBC tissues and cells, which were positively correlated with tumor metastasis, advanced clinical stage and poor survival rate. Up-regulated STAT1 could promote the proliferation, invasion, migration, EMT and inhibit the apoptosis of TNBC cells. RNA-seq indicated has_circ_0005571 (CircIFI30) was significantly down-regulated in TNBC cells after knockdown of STAT1. Moreover, STAT1 could be novel transcription factor that binds to CircIFI30 promoter to enhance its transcription. Additionally, knockdown of CirclFl30 down regulated the expression of cell division cycleassociated protein 4 (CDCA4) through reducing the stability of its mRNA. Our data revealed the STAT1/CircIFI30/CDCA4 axis could regulate the proliferation, invasion, migration, EMT and apoptosis of TNBC cells. Therefore, STAT1 may be a putative therapeutic candidate for targeted treatment of TNBC.