Aetiology of childhood leukemia

Leukemia is the most common cancer to affect children, accounting for approximately a third of all childhood cancers. The major morphological subtypes of leukemia, acute lymphoblastic leukemia (ALL), and acute myeloblastic leukemia (AML), are characterized by chromosomal translocations involving over 200 genes including mixed lineage leukemia (MLL), TEL, and AML1. Chromosomal translocations involving the MLL gene at 11q23 are a common feature of infant acute leukemia, found in up to 80% of all cases, and there is strong evidence that rearrangements involving the MLL gene or the TEL-AML1 gene fusion can originate in utero. As with most other cancers, the mechanism by which leukemia arises is likely to involve gene-environment interactions. Accordingly, it is important to identify exposures that cause DNA damage and induce chromosome breaks which are inadequately repaired, ultimately leading to the initiation and disease progression. Exposures acting before birth and early in life has long been thought to be important determinants of leukemia, and the list of suspected chemical, physical, and biological agents continues to increase. Unfortunately, the evidence regarding the majority of suggested exposures is limited and often contradictory, and there are areas, which clearly warrant further investigation in order to further our understanding of the aetiology of childhood leukemia.