BMI1 and osteosarcoma: Several other tumours are characterized by a significant increase in both EZH2 and BMI1 expression, suggesting deregulation of PcG proteins is a common feature of transformed cells; such tumours include oral squamous cell carcinomas [143,144], hepatocellular carcinomas [145,146], gastrointestinal cancers [147,148,149], osteosarcomas [150], and bladder tumours [151,152,153,154].