Tumor microenvironment on the move and the Aselli connection.

The tumor microenvironment is involved in many activities that promote tumor cell growth, local spreading, and metastasis. In this issue of Science Signaling, Jung et al found that lymphangiogenesis may result from the cooperation of two molecules, sphingosine-1-phosphate (S1P) and lipocalin 2 (LCN2), produced by tumor cells and macrophages, respectively. The new S1P-LCN2 axis stresses the importance of innate immunity in remodeling the tumor microenvironment and in lymphangiogenesis.