Many cancers are thought to be driven by cancer stem cells — cancer cells that divide continuously and seed tumours. Researchers in Italy have elucidated a molecular mechanism by which one component of a key pathway linked to organ size confers cancer stem-cell properties on breast-cancer cells.

Michelangelo Cordenonsi and Stefano Piccolo at the University of Padua and their team examined the Hippo pathway, which controls organ size by inhibiting cell growth and promoting cell death. They found that levels and activity of a protein called TAZ — which inhibits the Hippo pathway — are elevated in aggressive breast tumours. TAZ is also required in breast-cancer stem cells to maintain their ability to self-renew and generate tumours, and it reprograms non-stem-cell tumour cells into stem-cell-like cancer cells.

Furthermore, TAZ is activated when a key regulator of the cell's spatial organization is lost.

Cell 147, 759–772 (2011)