While we have not directly assessed the levels of specific pro-metastatic chemokines and their cognate receptors, such as CXCR4, in the present study, previous work has demonstrated that CAIX is required for nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-mediated production of granulocyte colony stimulating factor (G-CSF) by hypoxic breast cancer cells in vivo, and that CAIX is required for the G-CSF-driven mobilization of granulocytic myeloid-derived suppressor cells (MDSCs) to the breast cancer lung metastatic niche [35]. Here, CXCR4 is linked to breast cancer.