S-phase DNA content and aneuploidy of immunophenotypic defined subpopulations in acute myeloid leukemia determined by multi-parameter flow cytometry

Cholesterol catabolism in patients with acute myelogenous leukemia and hypocholesterolemia: suppressed levels of a circulating marker for bile acid synthesis

Hypocholesterolemia is a frequent finding in patients with acute myelogenous leukemia (AML) and in other types of malignancies. Since bile acids are major excretion products of cholesterol, the hepatic degradation of cholesterol to bile acids was investigated in AML patients by analyzing a circulating marker for bile acid synthesis. In addition, plasma levels of a marker for cholesterol synthesis were determined. The plasma levels of 7alpha-hydroxy-4-cholesten-3-one, reflecting bile acid production, were markedly lower in patients with AML than in healthy controls. The median levels were 3.3 and 18.5ng/ml (P<0.0001) in the AML patients (n=29) and the healthy subjects (n=16), respectively. The plasma levels of 7-dehydrocholesterol, reflecting hepatic cholesterol synthesis, were similar for the AML patients and the controls. The results show that the conversion of cholesterol to bile acids was suppressed in AML patients, a phenomenon that may result in a decreased intestinal absorption of cholesterol and subsequent hypocholesterolemia.

Myelopoiesis in myelodysplasia evaluated by multiparameter flow cytometry

Evaluating the proliferative activity of the immature erythro- and myelopoiesis as well as the mature myelopoiesis in 21 MDS patients and 14 healthy controls by simultaneously staining bone marrow cells for surface phenotype and DNA content, we found the percentages of proliferating S-phase cells in the early stage of MDS were higher. With disease progression evaluated by the FAB classification this parameter decreased significantly for both the immature myelo- and erythropoiesis. Evaluation of the proliferative activity of the mature myelopoiesis defined by the CD66 antigen revealed no difference between the normal controls and the MDS patients. Using another assay simultaneously labelling bone marrow cells for three leucocyte differentiation antigens during treatment with GM-CSF and low-dose AraC the cells clearly differentiated in one case. In another patient the disease seemed to progress as evaluated by cells only expressing immature antigens. The above mentioned immunophenotypic changes persisted at least one month after termination of treatment. In conclusion, the evaluation of proliferation and differentiation of leucocyte subsets using multiparameter flowcytometric assays in myelodysplastic patients from different FAB groups before as well as during treatment with haemopoietic growth factors may prove valuable in the future.

Over-expression and amplification of the CDC2 gene in leukaemia cells

The expression and structure of the cdc2 gene, one of the master regulators of the eukaryotic cell cycle, were investigated in fresh leukaemic cells from 51 cases of various types of leukaemia. Cdc2 mRNA transcripts were detectable in approximately 40% (21/51) of cases by Northern blotting. Over-expression of cdc2 mRNA as compared to normal bone marrow cells was noted in 10/21 cases with detectable cdc2 mRNA transcripts. Amplification of the cdc2 gene was found in three cases. Cdc2 mRNA was over-expressed in these three cases, suggesting that gene amplification is a direct cause of mRNA over-expression in a subset of cases. Cell proliferative capacity was well correlated with the amount of cdc2 mRNA transcripts, i.e. 3H-thymidine incorporation was highest in cases with cdc2 mRNA over-expression and was significantly higher in cdc2-positive cases than in cdc2-negative cases. These results suggest that over-expression of CDC2, which is due to the gene amplification in some cases, might play a role in altered growth of leukaemic cells.

The proliferative activity of myelopoiesis in myelodysplasia evaluated by multiparameter flow cytometry

Double staining of bone marrow cells for CD13 and CD33 leucocyte differentiatian antigens and for DNA content has allowed us to evaluate the proliferative capacity of myelopoiesis in patients with myelodysplastic syndromes (MDS) using flow cytometry. By analysing 39 patients (15 RA/RAS, 14 RAEB and 10 RAEB-t) and eight normal controls, we found significant differences in both the percentage of cells positive for these immature myeloid antigens between the FAB groups as well as in the fractions of CD13 and CD33 positive cells in S or S-G2M phase of the cell cycle. Moreover, a clear decrease in the immature myeloid cell proliferative activity upon progression within the FAB groups was evident. Finally, we found a significant negative association between the percentage of myeloblasts in the bone marrow and the proliferative activity of the immature myeloid cells, indicating that the block in differentiation in MDS patients might be coupled to a simultaneous block in proliferation, especially in advanced stages. These data suggest that the use of double parameter assays in the longitudinal follow-up of MDS patients might yield new information about the biology of MDS.