Loss of the Tumor Suppressor <em>Pten</em> Promotes Proliferation of <em>Drosophila melanogaster</em> Cells In Vitro and Gives Rise to Continuous Cell Lines

<div><p>In vivo analysis of <em>Drosophila melanogaster</em> has enhanced our understanding of many biological processes, notably the mechanisms of heredity and development. While in vivo analysis of mutants has been a strength of the field, analyzing fly cells in culture is valuable for cell biological, biochemical and whole genome approaches in which large numbers of homogeneous cells are required. An efficient genetic method to derive <em>Drosophila</em> cell lines using expression of an oncogenic form of <em>Ras (Ras^V12)</em> has been developed. Mutations in tumor suppressors, which are known to cause cell hyperproliferation in vivo, could provide another method for generating <em>Drosophila</em> cell lines. Here we screened <em>Drosophila</em> tumor suppressor mutations to test if they promoted cell proliferation in vitro. We generated primary cultures and determined when patches of proliferating cells first emerged. These cells emerged on average at 37 days in wild-type cultures. Using this assay we found that a <em>Pten</em> mutation had a strong effect. Patches of proliferating cells appeared on average at 11 days and the cultures became confluent in about 3 weeks, which is similar to the timeframe for cultures expressing <em>Ras^V12</em>. Three <em>Pten</em> mutant cell lines were generated and these have now been cultured for between 250 and 630 cell doublings suggesting the life of the mutant cells is likely to be indefinite. We conclude that the use of <em>Pten</em> mutants is a powerful means to derive new <em>Drosophila</em> cell lines.</p>