CYTOGENETIC INVESTIGATIONS ON HUMAN X-CHROMATIN, Y-CHROMATIN, F-BODY, AND DIFFERENTIATION OF A MYELOID CELL LINE (HL-60)

The relationship between in vitro cell density, cell cycle phase, and X- and Y-chromatin body frequencies was examined in synchronized populations of male and female fibroblasts. A significantly lower X-chromatin body frequency was observed in cells synchronized at S as compared to G(,1), G(,2) and non-synchronized controls. No significant difference was noted at various cell densities. The frequency of the Y-chromatin body did not vary with respect to either cell density or cell cycle phase. The results of this study indicate that a cell cycle factor may be responsible for the previously reported differences in X- and Y-chromatin body frequencies. HL-60 is a continuous myeloid cell line established from the peripheral blood leukocytes of a patient with acute promyelocytic leukemia. With the aid of dimethylsulfoxide (DMSO) and dimethylformamide (DMF) a high proportion of promyelocytes was induced to undergo terminal differentiation to more mature myelocytic granulocytes. Cytogenetic studies revealed aneuploidy, clones with 45 or 46 chromosomes became predominent with continued passaging of cultures. HL-60 cells were continuously exposed to 1.25% DMSO and 90 mM DMF for 8 days. Analyses of the relationship between lobe counts and drumsticks frequency in the resulting polymorphs indicated that the frequency of drumsticks goes up with increasing lobe counts. The highest frequency was observed in 5-lobed nuclei of polymorphs (12% for DMSO and 17.7% for DMF). These results were consistent with previously reported in vivo studies. The relative frequency of lymphocytes with nuclear Y-body-like fluorescent structures (F-bodies) was examined in 10 patients with chronic lymphocytic leukemia (CLL) and in 10 normal individuals. In each patient the frequency was significantly higher as compared to that of normal controls. There was a significant correlation between the sex and the corresponding frequency of F-body positive (F-body+) cells, i.e., females showing a higher proportion than males. There was no apparent relationship between the frequency of F-body+ lymphocytes and the relative age of an individual. The presence of F-bodies in CLL had no obvious correlation with the presence of karyotypic abnormalities in these patients. Isolated T- and B- lymphocytes derived from 4 normal subjects showed no extra F-bodies as found in CLL patients