RABGEF1 and neoplasm: Given that Ras is ubiquitinated by Rabex-5, and the Ras pathway has been shown to be upregulated in Rabex-5 mutant larvae (Xu et al., 2010; Yan et al., 2010), it is intriguing to speculate whether this may be contributing in some way to the neoplastic phenotype seen in mutant larval discs, not only in the Rabex-5 background but perhaps more generally in other endocytic neoplastic tumour suppressor mutants.