RAC1 and breast cancer: However, how TUFT1 specifically regulates Rac1 expression, in a recent study, Kawasak et al. (14) found that TUFT1 activated the mTORC1 signaling pathway by regulating the Rab GTPase, and that the interaction of TUFT1 and RabGAP1 mediated intracellular lysosome localization and vesicle transport in BC cells, while Rac1 is the substrate of mTOR.