Causes of leukemia
Leukemias may be due to viral infections, such as the Epstein-Barr virus, but also ionizing radiations, chronic exposure to chemicals such as alkylating agents and topoisomerase 2 inhibitors (AMLs) or benzene aniline dyes, and genetic mutations. Acute leukemias are due to a block in the maturation process and arrest of differentiation due to gene mutations. Genes involved are usually transcription factors such as TELI, AMLI, E2A and EBF in B cell AML (B-ALL), or TALI and NOTCHI gene mutations in T cell ALL (T-ALL).
B-ALL is also associated with Philadelphia chromosome translocation. This mutation accelerates the production of tyrosine kinases, which have similar effect as other growth factors. These growth factors cause uncontrolled proliferation of cells.
CLL is due to mutations in genes that regulate an anti-apoptotic gene. This leads to over survival of lymphocytes. CLL is also associated with Down syndrome, deletion of chromosome 11 and 13.