Lipocalin 2, an iron-siderophore-binding protein, converts embryonic kidney mesenchyme to
epithelia. We found that lipocalin 2 could also convert 4T1-Ras-transformed mesenchymal
tumor cells to an epithelial phenotype, increase E-cadherin expression, and suppress cell
invasiveness in vitro and tumor growth and lung metastases in vivo. The Ras-MAPK
pathway mediated the epithelial to mesenchymal transition in part by increasing E-cadherin
phosphorylation and degradation. Lipocalin 2 antagonized these effects at a point upstream …