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). The gene discussed is VAV1; the disease is neoplasm.