Heike Engel

Quantitation of minimal residual disease in acute myelogenous leukemia and myelodysplastic syndromes in complete remission by molecular cytogenetics of progenitor cells

Detection of karyotypic clonal abnormalities are prognostically useful in patients with acute myelogenous leukemia (AML) and myelodysplastic syndromes (MDS), but cytogenetic methods are not sensitive enough to detect low numbers of residual leukemic cells in patients who have achieved complete remission (CR). Fluorescence in situ hybridization (FISH) and fluorescence activated cell sorting (FACS) were used to investigate the frequency and presence of minimal residual disease (MRD) in AML and MDS patients (n = 28) with monosomy of chromosomes 7, 17 and 18 and trisomy of chromosomes 6, 8, 9 and 10 in CR. MRD was detected in all patients with monosomy 7 (n = 10) and followed by relapse in eight patients after 4.8 ± 3.1 months. In contrast, persistent leukemic cells occurred in 11/12 patients with trisomy 8, but only three of them relapsed after 7.7 ± 4.0 months. Cox regression analysis showed that cytogenetic class and levels of clonal cells at CR were related to time to relapse (P = 0.001). The level of MRD identified patients at high and low risk of relapse. High absolute levels of proliferating residual leukemic cells correlated with monosomy 7 and high risk of relapse.

Minimal residual disease in acute myelogenous leukaemia and myelodysplastic syndromes: a follow‐up of patients in clinical remission

The majority of patients with acute myelogenous leukaemia (AML) and myelodysplastic syndromes (MDS) relapse, especially those with unfavourable cytogenetics.

Expression of MDR1 by Normal Bone Marrow Cells and its Implication for Leukemic Hematopoiesis

Expression of MDR1 is a well-characterized mechanism leading to resistance of tumor cells to drugs like vinca-alkaloids, anthracyclines, and epipodophyllotoxins. In hematopoiesis, recent data indicate that not only leukemic cells, but also some populations of normal hematopoietic cells, particularly CD34+ progenitor cells as well as peripheral blood lymphocytes, express a functional multidrug-resistant phenotype. Among CD34+ cells, we found evidence that myeloid committed precursor cells (CD34+/CD33+) have lower levels of MDR1 expression than earlier CD34+ cell populations, but there was no difference in MDR1 expression between CD34+/HLA-DR- and CD34+/HLA-DR+ subpopulations. During normal myeloid differentiation, MDR1 expression is down-regulated, which is similar to our observations in acute myelogenous leukemia (AML): MDR1 expression was only rarely detected in acute promyelocytic leukemia, which was in contrast to other subtypes of AML; also, within leukemic subpopulations of the same patient, higher MDR1 levels were correlated with a more immature immunophenotype. Regarding regulation of MDR1 expression, we did not observe changes of MDR1 expression in normal CD34+ cells in response to various cytokines. However, in 2 patients with AML treated with interleukin-3 and granulocyte-colony stimulating factor, respectively, a significant down-regulation of MDR1 expression was found after 24 hours. In conclusion, there is evidence that the pattern of MDR1 expression observed in leukemias reflects the distribution of MDR1 in normal hematopoiesis. In contrast to normal CD34+ cells, leukemic cells from some AML patients can respond to cytokines with a down-regulation of MDR1, which may contribute to response to cytokine/chemotherapy combinations.

High incidence of monosomy 18 in lymphoid malignancies that have bone marrow and peripheral blood involvement

We studied the incidence of numerical chromosome 18 abnormalities in 107 patients with lymphoid malignancies by fluorescence in situ hybridization (FISH) using a directly conjugated centromeric probe for chromosome 18. Samples were obtained by fine needle aspiration of diseased nodes, bone marrows or peripheral blood. Monosomy 18 was more common in chronic lymphocytic leukemia (43%), small lymphocytic lymphoma (28%), and follicular lymphomas (12.5%) than in diffuse lymphomas (5.3%; p < 0.01). Monosomy 18 was detected in 9.7-17.1% of the cells in non-Hodgkins lymphoma (NHL) (background, 5.4%; 99% CI, 4.2%-6.6%) and in 8%-16.7% (median, 10%) of the cells in (CLL) (background, 3.4%; 99% CI, 2.5%-4.3%). All patients with monosomy 18 were found to have bone marrow involvement. Of all untreated patients who had disease involving the bone marrow, 32% were found to have monosomy 18. Trisomy 18 was detected in 3.6%-48.2% of the cells in NHL (background, 0.9%; 99% CI, 0.2%-1.6%) and was most common in diffuse large-cell lymphoma (34%) and follicular lymphomas (31%). None of the patients with small lymphocytic lymphoma or chronic lymphocytic leukemia had trisomy 18. There was no correlation between trisomy 18 and response to treatment or clinical presentation. In this study, monosomy 18 was observed frequently in patients with lymphoid malignancies that involve the bone marrow and peripheral blood. Our data suggest that important gene(s) located on chromosome 18 may be involved in homing of the malignant lymphocytes to the bone marrow and peripheral blood.