Our previous study demonstrated that Bnl protein expression was elevated in the secondary tumours associated with tracheal branches13; we now demonstrate that Bnl protein expression is strongly upregulated in ras1G12V;csk−/− primary tumours, but not in the wild-type (LacZ) eye discs of animals fed an HSD (Fig. 2b, c and Supplementary Fig. 3c–e). Here, CSK is linked to neoplasm.