The tumour suppressor PTEN is an antagonist of the phosphoinositide 3-kinase (PI3K) pathway that is mutated in several cancers. Hopkins et al. identified a translational variant of PTEN, dubbed PTEN-long, that was a secreted, membrane-permeable lipid phosphatase that interacted with cell surface proteins and could enter other cells. In vitro, administration of PTEN-long antagonized PI3K signalling and it reduced tumour growth in a mouse model. The authors suggest that recombinant PTEN-long could provide therapeutic benefit by delivering functional tumour suppressor protein to cells.