CORO1B (coronin 1B) is an actin-binding protein that regulates cell motility and lamellipodia dynamics through interaction with the ARP2/3 complex. 1 The protein functions as a negative regulator of actin nucleation; phosphorylation of CORO1B at serine-2 by PKCε disrupts its interaction with ARP2/3, promoting lamellipodial protrusion and cell migration in response to PDGF signaling. 1 During cardiac development, CORO1B expression is transcriptionally regulated by the Wilms' tumor suppressor Wt1 in epicardial regions where epithelial-mesenchymal transition occurs. 2 At the molecular level, USP45 deubiquitinase stabilizes CORO1B protein levels; loss of either USP45 or CORO1B promotes F-actin patch formation and enhances lysosomal acidification through N-WASP-dependent mechanisms, ultimately activating autophagy. 3 Clinically, elevated CORO1B expression correlates with poor prognosis in multiple cancers, including pancreatic ductal adenocarcinoma and gastric cancer. 4 CORO1B is enriched in small extracellular vesicles from cancer cells with increased migratory capacity, 5 and its DNA methylation status in leukocytes is altered following chemotherapy in breast cancer patients. 6 These findings establish CORO1B as a critical node in both normal cell migration processes and cancer-associated cell motility.