The percentage of MDSCs in the bone marrow has been found to be far greater than that in the lungs and mammary glands.135 An innate immune pathway of interferon regulatory factor 7 (IRF7) silencing has been identified to facilitate the immune escape of breast cancer cells and promote bone metastasis via selective modulation of MDSCs and natural killer (NK) effectors in the bone marrow135 (Fig. 2b). This evidence concerns the gene IRF7 and breast cancer.