EMP3 (epithelial membrane protein 3) is a tetraspan membrane protein belonging to the PMP22 gene family, characterized by four transmembrane domains and widespread tissue expression 1. Primary function: EMP3 regulates membrane receptor trafficking and stability, particularly EGFR, by interacting with endocytic proteins and preventing receptor degradation via RAB7-mediated endosomal trafficking 2. The protein also regulates immune cell function in T cells and macrophages 1. Mechanism: EMP3 sustains oncogenic signaling cascades including EGFR/CDK2, HER-2/PI3K/Akt, MAPK/ERK, and TGF-beta/Smad pathways, promoting cell cycle progression and proliferation while suppressing apoptosis 1. Disease relevance: EMP3 expression patterns distinguish tumor types—overexpression correlates with poor prognosis in IDH-wild-type glioblastoma and breast cancer, where high EMP3 associates with HER-2 expression 34. Conversely, EMP3 functions as a tumor suppressor gene in oligodendroglial tumors where promoter hypermethylation silences expression 56. Clinical significance: EMP3 hypermethylation status serves as a prognostic marker in gliomas and can predict therapeutic outcomes 6. EMP3 emerges as a promising therapeutic target, with EMP3 inhibition enhancing sensitivity to kinase inhibitors including osimertinib and CDK2 inhibitors in glioblastoma 2.