In Cell this week, researchers in Italy say that TAZ, a transducer of the Hippo pathway, is responsible for conferring the properties of cancer stem cells onto breast cancer cells. TAZ is required to sustain self-renewal and tumor-initiation capacities in breast cancer stem cells, the authors write. "TAZ protein levels and activity are elevated in prospective CSCs and in poorly differentiated human tumors and have prognostic value," they add.