RAC1 and keratoacanthoma: According to reports, Tiam1/Rac signaling could regulate the Par3 complex in keratinocytes, while the inhibitory function of Par3 on keratoacanthoma formation was not observed in Tiam1- and Rac1-deficient mice (118), indicating that Tiam/Rac signaling is crucial for Par3 function as a tumor repressor.