NPM3 (nucleophosmin/nucleoplasmin 3) is a nuclear chaperone protein that regulates diverse cellular processes including ribosome biogenesis, chr10 remodeling, and protein chaperoning 1. The protein is primarily localized to the nucleus and is widely expressed across human tissues, with particularly high expression in pancreas and testis 1. NPM3 functions through homo- and hetero-oligomer formation with other NPM family members, particularly NPM1, to mediate chr10 assembly and nucleosome formation 2. The protein modulates NPM1's histone chaperone function and RNA-binding activity, with NPM3 suppressing NPM1's RNA-binding capability while enhancing its nucleoplasm-nucleolus shuttling 2. In disease contexts, NPM3 demonstrates oncogenic properties across multiple cancer types, with elevated expression associated with poor prognosis in lung adenocarcinoma, gastric cancer, and prostate cancer 345. NPM3 promotes tumor progression by enhancing cell proliferation and migration, and contributes to immune escape mechanisms through regulation of PD-L1 expression 4. The protein is also involved in vasculogenic mimicry formation in lung adenocarcinoma, supporting tumor aggressiveness and metastasis 6. These findings establish NPM3 as both a critical cellular chaperone and potential therapeutic target in cancer.