Gene Expression of Insulin-Like Growth Factor Binding Proteins (IGFBP-2 and IGFBP-3) in Childhood Acute Myeloblastic Leukemia. Intr. by Herbert Sayer.

Abstract

Insulin-like growth factor (IGF) system plays an important role in regulating cellular proliferation. Alterations to the Insulin-like growth factor system have been reported for different tumors. They are of particular interest in the search for new prognostic and therapeutic approaches to cancer treatment. This study aimed to investigate the expression of IGFBP-2, IGFBP-3, IGF-I and IGF-II genes in leukemic cells from children with previously untreated acute myeloblastic leukemia (AML).The expression of IGF-I and IGF-II genes as well as IGFBP-2 and IGFBP-3 genes were measured using TaqMan real-time PCR in 50 children (mean age 10.8±4.8 years). All four genes were expressed with a great variability. RNA samples were extracted from leukemic cells enriched by Ficoll-Hypaque density gradient separation of bone marrow or peripheral blood mononuclear cells (MNC). MNC samples from peripheral blood and bone marrow of healthy children were used as controls. The median expression of IGFBP-2 was 25 times higher in AML cells than in peripheral MNC (p<0.001) and 10 times higher in bone marrow of healthy children (p<0.01). Increased IGFBP-2 gene expression at time of diagnosis was associated with a poor prognosis and a shortened survival time. Leukemic cells of patients who remained in continuous complete remission during the follow up showed a significant decreased IGFBP-2 gene expression at time of diagnosis compared to patients who suffered from relapse (p=0.05).On the other hand, AML cells showed a significantly lower IGFBP-3 gene expression than controls. The median expression of IGFBP-3 was 30 times lower in AML cells than in peripheral MNC (p<0.001) and 20 times lower than in bone marrow of healthy children (p<0.001). No significant difference could be found in IGF-I and IGF-II expression between leukemic and normal cells. Leukemic cells from children with previously untreated AML express components of IGF system. Especially IGFBP-2 seems to play an important role. By this mechanism, IGFBP-2 promotes their own growth in an autocrine, paracrine or endocrine manner. Whether these components will be useful as prognostic factors in stratification of AML treatment in children needs to be evaluated.