RAC1 and neoplasm: We selected these models for our experiments because: (i) they are known to be Rac1- (ID number: 19353) and Tiam1-dependent [4],[31]; (ii) high levels of two Vav family proteins and a large number of additional Rho GEFs are present in normal and tumoral skin (see Figure S1), thus making a perfect working model to address intra-GEF family redundancies in a tumorigenic context; and (iii) they are compatible with the analysis of the role of the proteins under study in the tumor initiation, promotion, and progression phases [28].