In Drosophila, normal and transformed cells do not always sit comfortably side-by-side. Instead, they compete for survival in a process referred to as ‘cell competition’. The events that occur at the interface of normal and transformed cells could have important implications for carcinogenesis, but so far it has been unclear whether a similar process occurs in mammals. On page , Yasuyuki Fujita and colleagues now suggest that cell competition is evolutionarily conserved by showing that loss of the tumour suppressor Scribble induces this process in MDCK cells. The authors find that, in the presence of normal cells, Scribble-knockdown cells undergo apoptosis and are extruded from the monolayer. Cell death does not occur, however, when cells lacking Scribble are cultured alone. Furthermore, caspase-3 is activated independently of cell extrusion, which indicates that cells do not die as a result of anoikis. Studies in Drosophila have implicated JNK with a role in mediating competition-induced cell death. By contrast, here, the researchers find that p38 MAPK (MAPK14) is required for the induction of apoptosis in mammalian cells lacking Scribble. These observations not only contribute to the understanding of how the cell environment can influence cell death but, importantly, also highlight that cell competition could act as an alternative tumour suppressor pathway in mammals.
