Overgrowth of a leukemic culture by a minor CD34+ population.
We have investigated the differentiation potential of blast cells in a case of acute myeloid leukemia which comprised a majority CD34- population and a minor (2%) CD34+ fraction. Blasts were cultured for 2 weeks in a combination of cytokines--c-Kit ligand, interleukin 3 and granulocyte macrophage colony-stimulating factor (SIGm mix)--together with all-trans retinoic acid or 1alpha ,25-dihydroxy vitamin D3. Maturation of blasts was assessed by morphology on Romanowsky-stained slides, changes in surface CD markers and clonogenic culture. After 7 days of culture of unseparated blasts in SIGm, most maturation was monocytic, but with retinoic acid 63% of blasts had matured into granulocytes. Vitamin D3 enhanced monocytic differentiation, with 60% of cells becoming monocytic. The percentage of CD14 and CD15 positive cells decreased over 7 days in SIGm (from 62% to 17% and from 76% to 39% for CD14 and CD15, respectively). CD14+ cell numbers were maintained, or recovered, in cultures supplemented with vitamin D3 (59% at day 7), and CD15+ cell numbers, too, remained unchanged in the presence of retinoic acid (67%) or vitamin D3 (66%). Aberrant markers CD7 and CD56 declined under any conditions. When separated, both the CD34- and CD34+ fractions showed similar changes in morphology and surface maturation markers, suggesting that these two populations may be closely related. However, only a few CD34+ cells expressed the aberrant markers present on the majority blast population. The CD34- population declined in culture while the CD34+ fraction rapidly expanded. This probably reflects the difference in progenitor content; high numbers of colony-forming cells were concentrated in the CD34+ subpopulation. We conclude that both CD34- and CD34+ populations can differentiate but only the CD34+ fraction proliferates. Primitive clonogenic CD34+ cells from this patient may generate occasional aberrant CD34+ blasts which could then differentiate into the accumulating aberrant CD34- blast population.
Haematology Department, University of Hospital of Wales and University of Wales College of Medicine, Cardiff, UK.
P
P
Baines
H
H
Lake
J
J
Fisher
L
L
Truran
T
T
Hoy
A K
AK
Burnett
D000208:Acute Disease; D000368:Aged; D018952:Antigens, CD34 / Q000032:analysis*; D019011:Antigens, CD7 / Q000032:analysis; D019002:CD56 Antigen / Q000032:analysis; D002455:Cell Division; D002999:Clone Cells / Q000166:cytology; D003114:Colony-Forming Units Assay; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology*; D017493:Leukocyte Common Antigens / Q000032:analysis; D007958:Leukocyte Count; D007963:Leukocytes, Mononuclear / Q000166:cytology* / Q000276:immunology*; D016256:Lewis X Antigen / Q000032:analysis; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D014407:Tumor Cells, Cultured
D018952:Antigens, CD34; D019011:Antigens, CD7; D019002:CD56 Antigen; D016256:Lewis X Antigen; D018950:Lipopolysaccharide Receptors; D017493:Leukocyte Common Antigens