As HO-1 was almost undetectable at the stage which is most vulnerable to malignant transformation into BCP-ALL (the pre-pro-B to pre-BI transition [70]), and in the malignant cells its expression was very low, we doubt that HO-1 may play a significant role in protection of B progenitors from leukogenesis. This evidence concerns the gene HMOX1 and acute lymphoblastic leukemia.