Bone marrow Th2 cytokine expression as predictor for relapse in childhood acute lymphoblastic leukemia (ALL)

The immunological environment of leukemic blasts in the bone marrow might play a decisive role in determining an individual's risk for relapse. In order to identify potential predictors of relapse and to elucidate the mechanisms of immune control of leukemic blasts we examined the expression of cytokines, costimulatory molecules and members of the TNF family in leukemic marrow samples in a prospective study. Samples from 49 consecutive pediatric patients with B cell precursor acute lymphocytic leukemia (BCP ALL) were analyzed by semiquantitative RT-PCR. We identified interleukin (IL)-10 expression as a significant adverse prognostic indicator in childhood BCP-ALL. The event free survival (EFS) of patients expressing IL-10 mRNA in high quantity was significantly lower compared with patients expressing low IL-10 mRNA. Taqman RT-PCR of sorted cell populations showed that IL-10 mRNA was synthetized almost exclusively by NK or T cells. In addition, we found an increased expression of IL-1, IL-4, CD86 and VEGF mRNA in patients with late relapses. Possibly, ALL cells mediate a Th2 shift through increased expression of CD86 and thereby influence the individual relapse risk. These findings emphasize the role of the immune system for the outcome of childhood ALL.