Variable differentiation patterns of acute myelogenous leukaemia blasts in liquid suspension cultures

Surface marker expression in acute myeloid leukaemia at first relapse

Surface markers were studied at first relapse in 66 cases of acute myeloid leukaemia (AML), using a panel of five monoclonal antibodies directed to CD13, CD14, CD15, CD33 and CD34 antigens. At time of relapse, there was increased expression of CD33 (P = 0.002) and CD34 (P = 0.0001), and decreased expression of CD13 (P = 0.004) and CD15 (P = 0.0001) antigens by comparison to initial diagnosis. There was no strict correlation with the FAB classification. However, CD13 and CD33 expression changes preferentially affected granulocytic leukaemias. At relapse, CD14 and CD34 were significantly more expressed in monocytic than in granulocytic AML (P = 0.01 and 0.003 respectively). In a multivariate analysis, CD34 expression was associated with a low CR rate (P = 0.001) and short survival (P = 0.05), whereas CD15 expression was associated with long survival (P = 0.0004). These results suggest that AML tends to relapse with a less differentiated phenotype than observed at diagnosis and that AML with less differentiated phenotype is of poor prognosis after first relapse, as also observed at diagnosis.

Neoplastic basophil/mast cell precursors from chronic myelogenous leukemia display heterogeneous responses for a hematopoietic factor

The response of neoplastic basophil/mast cell precursors to various hematopoietic factors was examined. Blastic or promyelocytic immature cells were obtained from six patients in basophilic crisis of chronic myelogenous leukemia. In all cases, after 14 days suspension culture more then 90% of the cells had basophilic features. 3H-thymidine uptake was markedly increased by the addition of GM-CSF in two cases, G-CSF in one, and IL-3 in two. In clonogenic cell assays, numerous colony formations were obtained when using the same growth factors as in the 3H-thymidine uptake assay. In addition, IL-3 induced colony formation in one case, despite a lack of thymidine uptake IL-4 had a synergistic effect on colony formation with IL-3 in one other case. None of the factors used showed any effect on differentiation. These findings indicate that the proliferation of neoplastic basophil/mast cell precursors may be regulated by various growth factors but response patterns are divergent.

Primary human acute myeloblastic leukaemia: an analysis of in vitro granulocytic maturation following stimulation with retinoic acid and G-CSF

Acute myeloid leukaemia (AML) is characterized by the inability of myeloid cells to reach terminal maturation. We examined to what degree granulocytic maturation could be achieved by stimulating AML blast cells in an in vitro serum-free system with a combination of granulocyte-colony stimulating factor (G-CSF) and all-trans-retinoic acid (RA). Specimens from 41 AML patients were cultured for 7 d and then examined for cytochemistry (myeloperoxidase, Sudan Black, naphthyl-ASD-chloracetate esterase, periodic acid Schiff) an nitroblue tetrazolium reduction. The expression of CD11a, CD11b, CD11c, CD15, CD18, CD10, CD24 and B13-3 membrane antigens was also evaluated. Morphological and cytochemical studies were also performed after AML colony culture and culture of normal bone marrow cells (NBM). The comparative analysis of the panel of parameters was indicative of granulocytic maturation although to different degrees. The cells from 25/41 cases showed morphologic maturation (May-Grünwald-Giemsa). A positive correlation was evident between morphological maturation and CD11b expression (11/22 patients) as well as that of CD11c and CD15 (6 patients). Napthyl ASD chloroacetate esterase and PAS stainings also correlated with morphology (in 10/22 and 10/24 patients respectively). Nevertheless, the pattern of granulocytic maturation was remarkably variable among the 41 cases examined. The cells from only a few patients acquired the full spectrum of granulocytic markers. The comparison with normal bone marrow blasts indicates that serum-free culture conditions can, per se, limit granulocytic maturation, but it also confirms the intrinsic inability of AML cells to attain complete maturation in response to two potent granulocytic inducers.

Abnormal granulopoiesis of leukemic cells with basophil/mast cell features. Cytochemical and ultrastructural observations

We have carried out cytochemical and ultrastructural examination of human leukemic cells showing basophil/mast cell features derived from patients with acute myelogenous leukemia or basophilic crisis in chronic myelogenous leukemia. Leukemic cells in each case initially showed metachromasia with toluidine blue and various degrees of positivity for astra blue. Other cytochemical results showed considerable variety among cases. The number of granules increased in short-term culture in every case. Ultrastructurally, small membrane-bound granules with or without myelinoid bodies or glycogen particles were present in immature blasts, followed by production of other granule types. In some cases, leukemic cells before and after liquid culture contained the typical basophil granules with or without myelinoid bodies, but the matrix was more loose than normal. Granules showing whorl or scroll matrix profiles, which were typical for mast cells, were present in two cases. In one case, immature leukemic cells contained theta granules, and some mature forms after short-term culture contained typical basophil/mast cell granules as well as theta granules. Leukemic cells occasionally contained multivesicular granules predominantly. These results indicate that leukemic cells with basophil/mast cell features show a heterogeneous configuration and contain abnormal granules differing from normal ones. This abnormal granulopoiesis may be attributable to the results of leukemic events and may be a hallmark for recognition of leukemic basophils/mast cells.

Cooperative effects of gamma-interferon and 1 alpha, 25-dihydroxyvitamin D3 on in vitro differentiation of the blast cells of RAEB and RAEB-T

We added recombinant human gamma-interferon (gamma-IFN) and 1 alpha, 25-dihydroxyvitamin D3 (1 alpha, 25 (OH)2D3) to the bone marrow cells from six patients with RAEB or RAEB-T in liquid suspension cultures. After cultivation for 7 to 9 days, numerical, morphological and functional changes of the cells were assessed. gamma-IFN and 1 alpha, 25 (OH)2D3 additively suppressed cell growth, especially the number of blast cells decreased. The expression of alpha-naphthylbutyrate esterase (NBE) activity appeared to be promoted but that of naphthol AS-D chloroacetate esterase (NAE) activity was apparently suppressed by the addition of gamma-IFN and/or 1 alpha, 25 (OH)2D3. The percentage of NBT reduction-positive cells and latex-phagocytizing cells was only slightly increased by both agents. These results indicate that gamma-IFN and 1 alpha, 25 (OH)2D3 cooperate to induce monocytoid differentiation of the patients' blast cells. Combination therapy with both agents merits further study.

Effects of recombinant G-CSF and GM-CSF on in vitro differentiation of the blast cells of RAEB and RAEB-T

To evaluate the effects of recombinant G-CSF and GM-CSF on RAEB and RAEB-T cells, blast cells from 6 patients were incubated in liquid culture systems with these CSFs for 7 days, and their numerical, morphological and functional changes were assessed. Both CSFs stimulated cell growth, but decreased the proportion of blast cells in 5 of the 6 cases. Karyotypic abnormalities persisted during cultivation in some cases. The CSFs also stimulated the expression of part of the esterase activities, and a positive interaction of both CSFs was seen in part. Although CSFs had no significant effects on the ability of cells to reduce NBT or to phagocytize latex particles, the results indicated that they induce partial differentiation of blast cells. It appears that such pathological cells still retain the capacity to respond to growth factors.

Sustained viability of acute myelogenous leukemia cells in liquid suspension culture correlates with occurrence of differentiation

To examine the relationship between viability of acute myelogenous leukemia (AML) blasts in liquid suspension culture and the occurrence of myeloid maturation in culture, total and differential cell counts and viability as determined by trypan blue dye exclusion were followed over 21 days of culture. A significant positive correlation was found between viability of cells on day 21 of culture and percentage of mature cells present. These data suggest that myeloid maturation may be a mechanism by which AML cells maintain viability in an adverse environment.