MUC3A is a membrane-bound mucin encoded on chromosome 7 that serves as a major glycoprotein component of mucus gels, providing protective and lubricating barriers at mucosal surfaces 1. The gene contains a 21-residue signal peptide followed by a 233-residue Thr-, Ser-, and Pro-rich nonrepetitive sequence contiguous with a hypervariable domain of tandem repeats 1. MUC3A transcription initiates from multiple sites within a TATA-less promoter containing binding sites for intestinal gene transcription factors 1. Human-specific tandem repeat expansions in MUC3A may contribute to transcriptional variation and potential genetic instability 2. In disease contexts, MUC3A exhibits oncogenic functions across multiple cancer types. In colorectal cancer, MUC3A activates the PI3K/Akt/mTOR signaling pathway to promote cell proliferation, invasion, and chemotherapy resistance 3. In non-small cell lung cancer, MUC3A upregulates PD-L1 expression through EGFR stabilization and PI3K/Akt pathway activation, promoting immune escape and reducing tyrosine kinase inhibitor sensitivity 4, while also activating the NFκB pathway to attenuate radiosensitivity 5. Non-synonymous MUC3A SNPs have been associated with Crohn's disease susceptibility 6. MUC3A's high expression in gastric adenocarcinoma makes it a promising immunotherapy target, with potential for CAR T cell-based approaches 78.