Therapeutic opportunities and targets in childhood leukemia.

Childhood leukemia is a common pediatric cancer in the developed world, the disease is biologically diverse and there is much discussion as to its causal mechanisms. Acute lymphoblastic leukemia (ALL) is the most common subtype and infants with ALL have a greatly increased risk of treatment failure. There are molecular and biological properties of leukemic cells that determine treatment outcome; these can usually be attributed to distinct genetic abnormalities that alter the normal proliferative and survival signals of hematopoietic cells. Experimental evidence for the existence of leukemic stem cells (LSC) has been obtained, and it is presumed that these cells arise from mutations in normal hematopoetic stem cells or progenitor cells, and they are difficult to eradicate. LSC seem to be surprisingly different from their normal counterparts and therefore are obvious new targets for drug therapy. Therapeutic concepts using monoclonal antibodies have substantially improved response rates in patients with malignant lymphomas and are currently being evaluated in other types of cancer.