FAM171A1 (also known as Astroprincin/APCN) is a 98-kDa type 1 transmembrane glycoprotein that regulates cytoskeletal dynamics and cell shape through modulation of actin stress fiber formation 1. Functionally, FAM171A1 overexpression induces cellular sprouting and invasive growth potential in tumor cells, while its knockdown causes disappearance of actin stress fibers 1. The protein contains a conserved carboxyterminal domain essential for these morphological effects and interacts with multiple partners including ADAM10 and ornithine decarboxylase antizyme-1 1. In cancer contexts, FAM171A1 exhibits elevated expression in invasive tumor cells compared to intratumoral cells 1. High FAM171A1 expression constitutes an independent marker of poor prognosis in colon cancer, independent of stage, grade, age, or gender 2. In triple-negative breast cancer, FAM171A1 functions as a hub gene regulated by miR-9-3p and serves as a prognostic biomarker 3. Additionally, exosomal lncRNA SNHG14 from breast cancer cells upregulates FAM171A1 through the EBF1 axis to promote fibroblast-to-CAF transformation 4. Beyond oncology, FAM171A1 emerged as a diagnostic biomarker for age-related sarcopenia, identified through WGCNA and LASSO analyses 5 6, and was associated with cataract risk in Mendelian randomization studies 7.