MDM2 and p53 in childhood acute lymphoblastic leukemia: Higher expression in childhood leukemias with poor prognosis compared to long-term survivors

In previous studies the authors have found increased expression of p53 and MDM2 proteins in leukemic cells in a majority of children eligible for bone marrow transplantation (BMT) due to relapse or prognostically unfavorable features. In this study the immunohistochemical expression of p53, MDM2, an d p21(Cip1) was investigated in bone marrow samples from the time of diagno sis in 30 children with acute lymphoblastic leukemia (ALI) surviving diseas e-free at least 5 years. This group was compared with 15 advanced ALL patie nts, admitted for BMT In 7 of the BMT patients original diagnostic marrow s amples were also available for analysis. Four out of 30 ALL patients in the relapse-free group expressed p53 in the original leukemic cell population, while 8/15 advanced ALL patients did before BMT (P =.014). Four out of 30 cases in the relapse-free group expressed MDM2, while 10/15 in the BMT grou p did (p =.0011). In retrospect, MDM2 overexpression at the time of diagnos is was also more common (p =.0098) in the BAIT group as well as p53 overexp ression (p =.054) compared to nonrelapsed patients.