Osterix Decreases the Chemosensitivity of Breast Cancer Cells by Upregulating GALNT14

Background/Aims: Osterix (Osx), a key regulator of osteoblast differentiation and bone formation, has been recently reported to be associated with the progression of breast cancer. However, the precise roles of Osx in breast cancer remain unclear. Methods: Drug sensitivity of the cancer cells was assessed using an 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Target genes were obtained by high-throughput Illumina sequencing and were confirmed in vitro and in vivo. Apoptosis was analysed by Hoechst staining and western blotting. A tissue microarray including 129 samples from breast cancer patients was used for immunohistochemistry (IHC) assays. Results: Overexpression of Osx decreased the chemosensitivity of breast cancer cells, while knockdown of Osx increased the chemosensitivity of breast cancer cells. In particular, we found that the decreased chemosensitivity effect was significantly associated with elevated expression of the polypeptide N-acetylgalactosaminyltransferase 14 (GALNT14). Silencing of GALNT14 in Osx-overexpressed cells restored the decreased chemosensitivity. Conversely, overexpression of GALNT14 in Osx-knockdown cells abrogated the increased chemosensitivity in breast cancer cells. In addition, we revealed that Osx decreased GALNT14-dependent chemosensitivity by enhancing anti-apoptosis. GALNT14 expression exhibited a significant association with breast cancer stages as well as the disease-free survival (DFS) rate. Conclusion: Osx plays an important role in the chemosensitivity and inhibition of Osx expression may represent a therapeutic strategy to enhance the chemosensitivity of breast cancer.