To test the interaction between Pico and Ras, we used a cancer model in Drosophila in which genetically defined tumours can be induced in the developing eye disc and brain.20, 21 In this model (Figure 1a), expression of the Flp gene, under the control of the eyeless promoter (eyFLP), is used to irreversibly switch on constitutive, GAL4-mediated expression of upstream activator element (UAS) target genes in the developing eye. This evidence concerns the gene LGALS4 and cancer.