The c-kit receptor and its ligand stem cell factor in childhood malignant lymphoid precursors

The c-kit receptor (CD117) and its ligand stem cell factor (SCF) play an im portant role in the development, differentiation, and survival of normal an d malignant hematopoietic cells. The aim of this work is to review the cell ular distribution of this receptor and the effect of SCF on the hematopoiet ic system, particularly among lymphoid lineage, either in normal or maligna nt cell progenitors. We examined reports and results in the field and artic les or abstracts published in journals covered by MEDLINE. Additionally, we evaluated CD117 expression on fresh blast cells of 376 newly diagnosed cas es of childhood acute lymphoblastic leukemia (ALL) that were referred to ce nters affiliated with the Italian Association for Pediatric Hematology and Oncology (AIEOP), In view of our data, approximately 11% of ALL are CD117 p ositive. In particular, this receptor can be expressed in 10% and 11.5% of T-lineage and B-lineage ALL, respectively. Its expression is associated wit h an intermediate/mature phenotype in T-lineage ALL, whereas in B-lineage A LL, the majority of the positive cases are classified as early B ALL. The e ffect of SCF on malignant hematopoiesis and its potential clinical uses are reviewed.