CXCR4 and breast cancer: Recently, numerous studies have pointed out its importance in tumor cell proliferation [32, 33, 35], migration, invasion [45, 46], angiogenesis [47], and anti-inflammatory, as our previous work revealed that MiR-5100 of PGRN−/− TAMs derived exosomes inhibited the CXCL12/CXCR4 axis and then ultimately inhibited the invasion, migration and EMT of breast cancer cells [48]; however, its role in immune evasion of breast cancer is poorly understood.