CXCR4 and neoplasm: More than intrinsic tumour cell behaviour, CXCR4/CXCL12 signalling contributes to the immune suppressive microenvironment seen in TNBC by recruiting regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumour-associated macrophages (TAMs) to the tumour, creating a block to tumour-specific immunity and promoting tumour evasion of the immune system.