Relationship between myeloblasts and cluster-forming cells in acute non-lymphocytic leukemia

The relationship between myeloblast-like cells and cluster-forming cells detected by growth in agar has been studied in 22 untreated patients with acute non-lymphocytic leukemia by means of comparing data for 3H-TdR labelling of myeloblast-like cells and 3H-TdR suiciding of cluster-forming cells. The fraction of myeloblast-like cells in S-phase was significantly smaller (13.1 +/- 8.7 per cent) than the fraction of cluster-forming cells in S-phase (35.5 +/- 15.3 per cent). In 2/22 patients approximately half of the myeloblast-like cells in DNA-synthesis were calculated to produce clusters in agar which may suggest similarity for cell cycle active myeloblast-like cells and cluster-forming cells. The other patients showed decreased plating efficiency for myeloblast-like cells in S-phase indicating non-identity or modification of the growth pattern due to environmental factors and variations in death rate during culture. Sequential studies in three patients indicated a changing relationship between myeloblast-like cells and cluster-forming cells suggesting non-identity or differences in growth regulation during the course of the disease.