engleski

Thiorphan stimulates clonal growth of GM-CFU in short term cultures of bone marrow from patients with acute leukemia

Thiorphan is a potent and specific inhibitor of neutral endopeptidase (membrane metallo-endopeptidase, EC 3.4.24.11). That enzyme, also known as the cell surface marker CD10/CALLA is expressed on many cells in various tissues, including the lymphoid tissue and bone marrow. Potential therapeutic applications of thiorphan include managment of pain, depression, diarrhoea, asthma and hypertension. However, its effects on the human hematopoietic cells have not been investigated. Here we report the effects of thiorphan in short-term GM-CFU clonal cultures of the bone marrow from 10 patients with acute leukemia. All patients were in complete remission (6 in the first and 4 in the second remmision). At the time of diagnosis, cytomorphological analysis of the bone marrow smears from the patients has shown 7 acute lymphoblastic leukemias (5 patients with L2 type and 2 with L1 type), 2 acute myeloblastic leukemias (1 patient with M1-M2 type and 1 with M2 type) and 1 myelodysplastic syndrome (1 patient with RAEB-t), The immunophenotyping revealed a high content of CD10+ cells in 3 patients (>30% CD10+ cells), medium in 3 patients (15-30% CD10+ cells) and low in 2 patients (0-15% CD10+ cells). Two patients have not been immunophenotyped. The median seeding efficiency of the specimens in the control groups without thiorphan varied from 10 to 366 colonies and clusters per 105 seeded cells. In order to make the results comparable, GM-CFUs counts in thiorphan-treated triplicate cultures of each patient were expressed as the percentages of the median count in the control, thiorphan-free triplicate cultures of that patient. Final concentrations of thiorphan in the cultures ranged from 10-5 to 10-13 M. Based on the statistical analysis of the data scatter, alterations of the clonal growth for 15 percent or more above or below the control counts were considered meaningful. These criteria were fulfilled in 32 out of 83 thiorphan-treated cultures (41 percent). In those cultures the stimulatory effects outnumbered the inhibitory ones (24 versus 8). The significance of the observations was confirmed by the c2-test (c2=8,0, p<0,005 with 1 level of freedom). The stimulatory effects of thiorphan occurred predominantly in bone marrow samples of the patients with T-ALL or with myeloid-type AL, whereas the bone marrow cultures of the patients with 'common'-type ALL were almost refractory. Thiorphan effects on the hematopoietic cells may be attributed to its interactions with the membrane metallo-endopeptidase (the CD10/CALLA marker) resulting in direct and/or indirect interference with cell proliferation.

bone marrow cells; acute leukemia; GM-CFU; CD10; thiorphan

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