LCN2 and cancer: The tumor microenvironment in central nervous system metastases, particularly LM, was shown to involve cancer cells in the CSF expressing the iron-binding protein lipocalin-2 and its receptor SCL22A17. This transcriptional diversity gives cancer cells a competitive edge over macrophages, which do not produce lipocalin-2, thereby depleting macrophages of iron and impairing their respiratory burst and phagocytic functions (138).