Attack of the Clones: Tracing the Dynamics of Innate Immune Cells in Human Cancer.

In this issue of Cancer Cell, Liu et al. use mitochondrial DNA mutations to reconstruct clonal lineages of the innate immune compartment in human tumors. They show that intratumoral type 3 dendritic cells (DC3s) arise from circulating monocytes and that a monocyte's fate in the tumor microenvironment is programmed peripherally, prior to tissue entry.