RAC1 and breast carcinoma: In a recent report on splice switching in breast cancer biopsies, two different isoforms of Rap1 GTPase-GDP Dissociation Stimulator 1 (RAP1GDS1) (protein name SmgGDS) were identified, called SmgGDS-607 and SmgGDS-558, both involved in prenylation of multiple small GTPases that contain a C-terminal polybasic region, including Rac1, RhoA, Kras, and Rap1 [53].