MRPL55 (mitochondrial ribosomal protein L55) is a structural component of the mitochondrial large ribosomal subunit essential for mitochondrial translation 1. The protein contains a KOW-like motif implicated in translational regulation and is dynamically required during development, particularly for mitochondrial biogenesis and G2/M phase cell cycle progression 1. Clinically, MRPL55 has emerged as a significant biomarker across multiple malignancies. In hepatocellular carcinoma, MRPL55 is among 14 mitochondrial ribosomal protein genes significantly upregulated in tumors and shows good diagnostic performance 2. In breast cancer, MRPL55 is overexpressed and correlates with advanced pathological stage, lymph node involvement, metastasis, and poor overall survival 3. Functionally, MRPL55 promotes cancer progression by modulating lipogenesis and cyclin-dependent kinase pathways, with knockdown suppressing proliferation and migration in breast cancer cells 3. Conversely, in ankylosing spondylitis, elevated MRPL55 levels are negatively associated with disease risk (OR 0.23), positioning it as a potential therapeutic target 4. These findings suggest MRPL55 serves dual roles: essential for normal mitochondrial function and cell cycle regulation, but oncogenic in malignant contexts through metabolic and cell cycle pathway dysregulation.