Discoidin Domain Receptor 2 Contributes to Breast Cancer Progression and Chemoresistance by Interacting with Collagen Type I

<b>Background</b>: Chemoresistance is an important issue to be solved in breast cancer. It is well known that the content and morphology of collagens in tumor tissues are drastically altered following chemotherapy, and discoidin domain receptor 2 (DDR2) is a unique type of receptor tyrosine kinase (RTK). This RTK is activated by collagens, playing important roles in human malignancies. However, the contribution to the chemoresistance of DDR2 in terms of the association with collagens remains largely unclear in breast cancer. <b>Methods</b>: We immunolocalized DDR2 and collagen type I in 224 breast cancer tissues and subsequently conducted in vitro studies to confirm the role of DDR2 in breast cancer chemoresistance using chemosensitive and chemoresistant cell lines. <b>Results</b>: DDR2 immunoreactivity was positively correlated with aggressive behaviors of breast cancer and was significantly associated with an increased risk of recurrence, especially in those who received chemotherapy. Moreover, in vitro experiments demonstrated that DDR2 promoted the proliferative activity of breast cancer cells, and cell viability after epirubicin treatment was significantly maintained by DDR2 in a collagen I-dependent manner. <b>Conclusions</b>: These data suggested that DDR2 could be a poor prognostic factor associated with cell proliferation and chemotherapy resistance in human breast cancer.