EIF4EBP3 is a translational repressor that regulates translation initiation by competing with EIF4G proteins for binding to EIF4E, the cap-binding protein required for ribosome recruitment 1. In its hypophosphorylated state, EIF4EBP3 sequesters EIF4E and prevents mRNA translation; upon hyperphosphorylation, it dissociates from EIF4E, allowing translation to proceed 2. During prolonged mTORC1 inhibition, EIF4EBP3 expression is transcriptionally induced via the TFE3 transcription factor, serving as a robust biomarker of mTOR inhibitor response 2. EIF4EBP3 acts as a tumor suppressor in gastric cancer, where it is frequently downregulated through promoter methylation; overexpression inhibits cell proliferation, migration, and invasion by targeting the eIF4E/β-catenin axis 3. In cervical cancer, miR-22-3p-mediated suppression of EIF4EBP3 promotes cell proliferation and inhibits apoptosis 4. EIF4EBP3 is also a marker of CDC73 tumor suppressor haploinsufficiency in parathyroid cancer 5. Notably, elevated serum autoantibodies against EIF4EBP3 were identified as the most upregulated autoantigen in immune checkpoint inhibitor-associated myocarditis, suggesting a role in immune-related adverse events 6. These findings establish EIF4EBP3 as a critical translational regulator with multiple disease implications.