To test whether upregulating PI3K/Akt signalling in the eye could also modulate the growth-promoting activity of the PATs (Figures 7B and C compared to 7A), we generated eyes that were almost entirely mutant for the key antagonist of this pathway, the fly homologue of the major tumour suppressor gene, PTEN (Figure 7D; [17], [60]), using the ey-FLP/FRT somatic recombination system and a recessive cell lethal chromosome [61]. This evidence concerns the gene PTEN and neoplasm.