Stem Cells and Leukaemia

Studies performed at RCRM have shown that hematopoietic and immune systems’ reconstitution after irradiation depends greatly on the functional abilities of the stem cells. Subset analysis and expression of CD34+ antigens on bone marrow and peripheral blood cells were studied in Chernobyl accident clean-up workers including patients with leukemia and myelodysplasia and patients exposed to the natural levels of irradiation. In myelodysplasia the elevation of early CD34+ cells was detected in bone marrow and peripheral blood. In leukemia the CD34+117+38- primitive progenitor cell counts were elevated mainly in patients with proliferation of poorly differentiated cells while in ALL’s the CD34+ counts were smaller. Circulating HSC and progenitors after radiation exposure in a wide range of doses have are preserved in a number and with proliferation potencies sufficient for the onset of clonal proliferation. In AML FLT3 mutations are the most abundant single-gene mutations. There is no difference in prevalence of FLT3 mutations in groups of radiation-associated and spontaneous AML cases. LOH/deletions at 5q and/or 7q and 7? tend to be more frequent in radiation-associated AML cases. Bone marrow and bone tissue microenvironment plays a key role in normal and neoplastic HSC changes. Differentiation to B-lineage isn’t changed and is associated with B-cell compartment growth.

Keywords: stem cells; radiation; leukemia; Chernobyl