TELOMERIC DNA IN NORMAL AND LEUKEMIC BLOOD-CELLS

We studied telomeric DNA in leukemic cells as well as in normal T cell s, B cells, monocytes, polymorphonuclear leukocytes, and bone marrow h ematopoietic progenitor cells. No marked differences were observed in the sizes of the telomeric repeats in the various populations of norma l blood cells obtained from donors in their twenties to sixties, and t he telomere length ranged between 8.5 and 9.0 kb. The leukemic cells o f 12 patients with acute leukemia (seven with myeloid and five with ly mphoid leukemia) showed a variable reduction in the length of telomeri c DNA, ranging from 2.7 to 6.4 kb. The average telomere length was 4.8 and 4.7 kb in myeloid and lymphoid leukemia, respectively, while the telomere length in peripheral blood mononuclear cells obtained from th e same patients during complete remission was 8.5 and 7.9 kb, respecti vely. When the same Southern blots were hybridized with Alu or alphoid sequences, no marked changes in the sizes of the repetitive DNA seque nces were observed, indicating that the DNA abnormality in the leukemi c cells was specific to the telomere region. Investigation of telomeri c DNA changes may be helpful in determining the biological properties of leukemic cells.