PDCD4 (programmed cell death 4) is a tumor suppressor protein that primarily functions as a translational inhibitor by binding to the 40S ribosomal subunit at the mRNA entry channel 1. The protein's C-terminal domain interacts with eIF4A at the mRNA entry site, while its N-terminal domain inserts into the mRNA channel, blocking eIF4F-independent translation initiation 1. PDCD4 specifically suppresses translation of oncogenic factors including Slug, preventing epithelial-to-mesenchymal transition and invasion in colorectal cancer 2. The protein also inhibits viral replication by disrupting eIF4A-mediated translation through four key residues (E249, D253, D414, D418) within its MA3 domains 3. PDCD4 demonstrates broad disease relevance as a tumor suppressor, with hypermethylation-mediated silencing correlating with poor survival in hepatocellular carcinoma 4. In thyroid carcinoma, PDCD4 loss leads to eIF4A-dependent overexpression of immunosuppressive effectors, promoting tumor-associated macrophage infiltration during dedifferentiation 5. Clinically, PDCD4 is frequently downregulated through proteasomal degradation mediated by various mechanisms, including DTL-mediated ubiquitination in cancer 6 and viral proteins in infections 3. Additionally, PDCD4 downregulation via miR-141-3p contributes to endothelial dysfunction and atherosclerosis in COPD patients 7.