RAC3 is a small GTPase that plays critical roles in cytoskeletal organization, cell migration, and cancer progression. As a member of the Rac family, RAC3 cycles between active GTP-bound and inactive GDP-bound states to regulate cellular responses including actin-based protrusions and cell adhesion 1. Unlike the ubiquitously expressed Rac1, RAC3 has more restricted tissue distribution and appears late in vertebrate evolution, suggesting specialized functions 1. In cancer biology, RAC3 demonstrates oncogenic properties across multiple tumor types. In endometrial cancer, RAC3 overexpression correlates with poor prognosis, promotes cell proliferation and invasion through FASN upregulation, and is associated with DNA hypomethylation 2. Similarly, RAC3 drives breast cancer metastasis by enhancing invasive and motile phenotypes 3, while its silencing in lung cancer inhibits proliferation and induces apoptosis 4. RAC3 also maintains cancer stem cell properties in colorectal cancer through functional relationships with CFTR 5. The protein's expression is negatively correlated with immune cell infiltration in tumors, suggesting potential immunomodulatory effects 2. These findings establish RAC3 as both a critical regulator of cytoskeletal dynamics and a significant oncogenic driver across multiple cancer types.