Single-cell atlas of human leptomeningeal metastasis

The tumor microenvironment plays a critical regulatory role in cancer progression, especially in metastases to the central nervous system. Cancer cells inhabiting the cerebrospinal spinal fluid (CSF)-filled leptomeningeal space face substantial microenvironmental challenges including inflammation and sparse extracellular iron. Unlike CSF leukocytes, we find that cancer cells within the CSF express the iron-binding protein LCN2 and its receptor SCL22A17. Employing mouse models of LM, we find that the LCN2/SLC22A17 system is necessary to support leptomeningeal cancer cell growth. We find that infiltrating CSF macrophages generate inflammatory cytokines that induce cancer cell LCN2 expression. This LCN2/SLC22A17 system provides cancer cells superior access to limiting extracellular iron, allowing LCN2-expressing cancer cells to outcompete CSF macrophages for this resource. Finally, pharmacologic interruption of these interactions prevents cancer cell growth within the leptomeninges. Overall design: 10x single-cell RNA-sequencing of human leptomeningeal metastasis