Despite promising results during early engraftment, the observed long-term displacement of wt cells by apoptosis-resistant counterparts could be hazardous: overshooting haematopoietic expansion may increase the risk of tumourigenesis and both bim−/− and vav-bcl-2 tg mice show an increased incidence of tumours when paired with aberrant oncogene activation and are prone to develop signs of autoimmunity (reviewed by Strasser, 2005). Here, BCL2 is linked to neoplasm.