STAP1 (signal transducing adaptor family member 1) functions as a docking protein in B cell receptor (BCR) signaling downstream of TEC kinase, participating in a positive feedback loop that increases TEC activity 1. The protein localizes to cytoplasmic and nuclear compartments and mediates signaling adaptor activity through phosphotyrosine binding and protein kinase interactions [GO annotations]. STAP1 is implicated in immune cell activation, including microglial cell-mediated cytotoxicity and responses to lipopolysaccharide [GO annotations]. In disease contexts, STAP1 methylation status serves as a diagnostic and prognostic biomarker for hepatitis B-related liver disease progression. Hypermethylation of STAP1 in peripheral blood T cells correlates with poor prognosis in hepatocellular carcinoma (HCC) ≤5 cm and is an independent prognostic factor for overall survival and disease-free survival 23. The combination of STAP1 and AHNAK methylation predicts different stages of HBV-related hepatopathy 3. Regarding familial hypercholesterolemia (FH), STAP1 was initially proposed as a causative gene, but subsequent evidence questions this role. Multiple studies found no cosegregation between STAP1 variants and hypercholesterolemia in FH families 45, and Stap1-/- mice showed no lipid metabolism abnormalities 6. In pediatric B-cell precursor acute lymphoblastic leukemia, STAP1 knockdown did not affect cell proliferation or viability, suggesting limited therapeutic targeting potential 1.