FGD3 (FYVE, RhoGEF and PH domain containing 3) is a guanine nucleotide exchange factor that specifically activates the Rho GTPase CDC42 by promoting GDP-to-GTP exchange 1. The protein contains canonical domains including RhoGEF, pleckstrin homology (PH), and FYVE domains that form the core structure characteristic of FGD1 family members 1. FGD3 promotes filopodia formation and regulates actin cytoskeleton organization through the CDC42-ARP2/3 signaling axis 12. Beyond cytoskeletal regulation, FGD3 serves as a key mediator of lytic cell death by coupling cell swelling to plasma membrane rupture in response to chemotherapy agents, facilitating the release of damage-associated molecular patterns and enhancing immunogenicity 2. Clinically, FGD3 functions as a tumor suppressor, with high expression correlating with improved prognosis in breast cancer patients, particularly after chemotherapy 342. In pancreatic cancer, FGD3 inhibits tumor progression by binding HSF4 to suppress p65 expression and inhibit NF-κB signaling 5. The gene shows tissue-diverse expression during embryogenesis, suggesting developmental roles, and is located on chromosome 9 1.