RPN2 (ribophorin II) is a subunit of the oligosaccharyl transferase (OST) complex that catalyzes the initial transfer of glycan from dolichol-pyrophosphate to asparagine residues in nascent polypeptide chains, representing the first step in protein N-glycosylation at the endoplasmic reticulum 1. This process occurs cotranslationally in association with the Sec61 translocon complex. Beyond its fundamental role in protein glycosylation, RPN2 has emerged as an important oncogene widely expressed in human malignancies 2. RPN2 contributes to tumorigenicity, metastasis, progression, and multi-drug resistance across multiple cancer types 2. In osteosarcoma, higher RPN2 expression correlates with poor prognosis, and RPN2 silencing reduces cell proliferation, invasion, and drug resistance 3. In breast cancer, RPN2 expression is higher in aggressive subtypes like triple-negative and HER2-enriched cancers, and correlates with p53 nuclear accumulation 4. RPN2 is also involved in autoimmune diseases, being upregulated in rheumatoid arthritis where it influences T lymphocyte activation and proliferation 5. Additionally, RPN2 is upregulated in Alzheimer's disease brain capillaries, specifically in ribosome complexes and protein processing pathways 6. These findings establish RPN2 as both a critical component of protein glycosylation and a promising biomarker and therapeutic target.