RPL9 (ribosomal protein L9) is a structural component of the large ribosomal subunit essential for protein synthesis 1. The protein functions as part of the cytosolic ribosome complex responsible for cellular translation. RPL9 variants can differentially impair ribosome function, with some causing pre-rRNA processing defects and 80S monosome reduction 1. Beyond its ribosomal role, RPL9 exhibits disease-relevant functions including acting as a putative tumor suppressor in bladder cancer, where higher expression correlates with longer recurrence-free survival after BCG therapy 2. However, RPL9 also demonstrates oncogenic properties in hepatocellular carcinoma by shuttling miRNAs through exosomes and promoting cancer cell proliferation, migration, and invasion 3. In B-cell acute lymphocytic leukemia, RPL9 knockdown triggers nucleolar stress, disrupts ribosome biosynthesis, and activates p53 signaling pathways, leading to decreased proliferation and increased apoptosis 4. The gene is located on chromosome 4 and shows tissue-specific expression patterns, with highest levels in retina and liver 5. RPL9's dual role as both tumor suppressor and oncogene appears context-dependent, highlighting its complex regulatory functions beyond ribosomal protein synthesis.