UAP1L1 (UDP-N-acetylglucosamine pyrophosphorylase 1 like 1) is a cytosolic enzyme involved in UDP-N-acetylglucosamine biosynthesis and protein O-GlcNAcylation. Unlike its homolog UAP1, UAP1L1 exhibits limited UDP-GlcNAc synthesis activity but directly interacts with O-GlcNAc transferase (OGT) to modulate protein glycosylation 1. UAP1L1 functions distinctly by promoting c-MYC O-GlcNAcylation and stabilization 1. UAP1L1 is significantly upregulated across multiple cancer types and promotes tumorigenicity through distinct downstream mechanisms. In prostate cancer, UAP1L1 enhances proliferation, migration, and invasion via CDCA8 regulation 2. In gastric cancer, it acts through CDK6-mediated cell cycle progression 3. In hepatocellular carcinoma and esophageal squamous cell carcinoma, UAP1L1 overexpression increases proliferation while knockdown induces apoptosis through modulation of pro-apoptotic proteins and PI3K/Akt/MAPK signaling 14. In glioblastoma, elevated UAP1L1 correlates with higher tumor grades and poor prognosis, with knockdown suppressing proliferation in vitro and in vivo 5. UAP1L1 is also identified as a potential marker of temozolomide resistance in glioblastoma 6. In breast cancer, UAP1L1 hypermethylation associates with tumor relapse 7. These findings establish UAP1L1 as a pan-cancer oncogenic factor with therapeutic potential.