piRNA-unbound PIWIL1 promotes metastasis.

Piwi proteins are aberrantly induced in human tumours, but their function in cancer has been poorly understood. A study now shows that in the absence of piRNA loading, human PIWIL1 promotes pancreatic cancer metastasis by acting as a co-activator of the anaphase-promoting complex/cyclosome (APC/C) to degrade the cell-adhesion protein Pinin.