MYO18B encodes myosin XVIIIB, a structural myosin that lacks active ATPase-driven motor activity and functions in organizing contractile machinery in both muscle and non-muscle cells 1. The protein localizes to diverse cellular compartments including lamella, actomyosin bundles, the Golgi apparatus, focal adhesions, and sarcomeres, where it contributes to organization, maturation, and regulation of contractile structures 1. MYO18B functions as a tumor suppressor gene, with frequent inactivation in lung cancers (approximately 50%) through deletion, mutation, and promoter methylation 2. Restoration of MYO18B expression suppresses anchorage-independent growth in lung cancer cells and inhibits tumor progression in malignant pleural mesothelioma 23. The gene is also inactivated in colorectal cancers through similar mechanisms, particularly histone deacetylation 4. Expression is regulated by histone acetylation, with deacetylation contributing to gene silencing in cancer cells 5. Gene amplification of MYO18B occurs during myogenic differentiation, suggesting a role in muscle cell development 6. High MYO18B expression predicts favorable prognosis in cutaneous squamous-cell carcinoma and is associated with smaller tumor size 7. The gene is also associated with cardiac aging and cardiomyopathy-related phenotypes 8.