SAMD4B is an RNA-binding protein with dual regulatory roles depending on cellular context. Structurally, it contains a sterile alpha motif (SAM) domain that enables binding to target mRNAs through stem-loop structures called Smaug recognition elements (SREs) 1. Primary transcriptional functions include repression of AP-1, p53, and CDKN1A through SAM domain-mediated interactions 2. Post-transcriptionally, SAMD4B regulates mRNA stability, degradation, and translation while forming cytoplasmic biomolecular condensates 1. Mechanistically, SAMD4B functions in metabolic sensing: BAG2 releases SAMD4B during arginine deficiency, promoting β-catenin degradation and ATF4 stabilization for cancer cell survival 3. Conversely, SAMD4B activates the Wnt/β-catenin pathway in breast cancer by stabilizing β-catenin mRNA 4. Additionally, SAMD4B regulates immune responses through 2'-O-methylation modifications affecting APOA2 mRNA stability and PD-L1 expression in hepatocellular carcinoma 5. Disease relevance spans multiple cancers: SAMD4B is upregulated in breast and endometrial cancers, correlating with poor prognosis and promoting proliferation, migration, and EMT 46. In hepatocellular carcinoma, targeting the SAMD4B-APOA2-PD-L1 axis significantly improves overall survival 5. These findings position SAMD4B as a potential therapeutic target across multiple malignancies.