High expression of SPAG5 sustains the malignant growth and invasion of breast cancer cells through the activation of Wnt/β-catenin signalling.

Sperm-associated antigen 5 (SPAG5) has currently emerged as a novel oncogene in various cancers. High expression of SPAG5 has been frequently detected in breast cancer. However, the biological function and regulatory mechanism of SPAG5 in breast cancer remain unclear. In this study, we aimed to investigate the potential biological function of SPAG5 in breast cancer cells. Herein, we found that both the mRNA and protein expression of SPAG5 were significantly up-regulated in breast cancer cell lines. Functional experiments showed that silencing of SPAG5 inhibited the proliferation and invasion of breast cancer cells, while the overexpression of SPAG5 promoted the proliferation and invasion of breast cancer cells. Mechanistic investigation demonstrated that SPAG5 promoted the expression of Wnt3 and β-catenin, and increased the activation of β-catenin/TCF4 transcriptional activity. Notably, the inhibition of Wnt3 partially reversed the promotion effect of SPAG5 on breast cancer cell proliferation and invasion and β-catenin/TCF4 signalling. In addition, the inhibition of β-catenin also significantly abrogated SPAG5-mediated oncogenic effects in breast cancer. Taken together, these findings demonstrate that SPAG5 promotes the proliferation and invasion of breast cancer cells by activating Wnt/β-catenin signalling via up-regulating Wnt3 expression.