RAB4A and neoplasm: RAB4A suppression leads to the loss of cancer cell sphere formation in vitro and loss-of-tumor formation in both subcutaneous and orthotopic xenograft mouse models (Fig. 1A, B and Supplementary Fig. S1) [29]; this loss of tumorigenesis can be rescued by exogenous expression of constitutively active RAC1 (RAC1CA) (Fig. 1A, B and Supplementary Fig. S1) [29].