Furthermore, using an immunodeficient Rag2−/−γc−/− murine model of breast cancer lacking the major PD-1 expressing immune cells (T, B and NK cells), our study showed that blockade of the PD-1/PD-L1 axis using PD-1 blocking antibodies in combination with doxorubicin had no effect on the number of metastases, highlighting the essential role of immune cells in the acquisition of chemoresistance. This evidence concerns the gene CD274 and breast cancer.