Decreased expression of SOX17 is associated with tumor progression and poor prognosis in breast cancer.

The SOX17 (SRY-related HMG-box) transcription factor is involved in a variety of biological processes and is related to the tumorigenesis and progression of multiple tumors. However, the clinical application of SOX17 for breast cancer prognosis is currently limited. The aim of this study was to investigate the clinicopathologic and prognostic significance of SOX17 expression in human breast cancer. qPCR and western blot assays were performed to measure the expression of SOX17 in breast cancer cell lines and 30 matched pairs of breast cancer and corresponding noncancerous tissues. A SOX17 overexpression cell model was used to examine changes in cell growth in vitro. Immunohistochemical analyses were performed to retrospectively examine the prognostic impact of SOX17 expression in 187 additional breast cancer patients. Our results showed that SOX17 expression was decreased at both the messenger RNA (mRNA) and protein levels in the breast cancer cell lines and tissues, and that SOX17 overexpression could strongly suppress cell growth in vitro. Furthermore, the lack of SOX17 protein expression was strongly correlated with higher tumor grade (P = 0.002), lymph node metastasis (P < 0.001), and tumor node metastasis (TNM) stage (P = 0.001) and had poorer disease-free survival (DFS) and overall survival (OS) compared to normal SOX17 expression (P = 0.002 and 0.001, respectively). Univariate and multivariate analyses indicated that lower SOX17 expression was an independent prognostic factor for DFS (P = 0.007; HR = 2.854; 95 % CI 1.326-6.147) and OS (P = 0.005; HR = 5.035; 95 % CI 1.648-15.385) for breast cancer. Our findings indicate that SOX17 expression is a useful prognostic biomarker for breast cancer.