SOX8 acts as a prognostic factor and mediator to regulate the progression of triple-negative breast cancer.

The molecular mechanisms underlying triple-negative breast cancer (TNBC) pathology are not fully understood. Here, we reviewed the SOX8 transcript level in 24 types of cancer and normal tissues and the SOX8 expression pattern in breast cancer from the TCGA and METABRIC data sets and found that SOX8 was highly expressed in TNBC. We investigated the effect of SOX8 on tumorigenicity, migration and apoptosis in TNBC cell lines and xenografts models. We identified SOX8 as a functional oncogene that involved in the maintenance of stem-like capacities in TNBC cells. Through a promoter truncation experiment and ChIP experiment, we verified zinc finger E-box binding homeobox 1 (ZEB1) as a transcriptional activator of SOX8 that enhanced SOX8 expression by binding to its promoter. We evaluated the ZEB1 and the SOX8 levels in 240 TNBC patients and high expression of ZEB1 and SOX8 were significantly associated with poor prognosis. We demonstrated the significance of the ZEB1-SOX8 axis in regulating TNBC cancer stem-like cells (CSCs) and its connection with poor prognosis. Due to its vital role in TNBC CSCs, the ZEB1-SOX8 regulatory axis could be a promising therapeutic target for TNBC.