Cytokinetic studies in chronic myeloid leukaemia: evidence for early presence of abnormal myeloblasts

Interphase ribosomal RNA cistron staining in chronic myeloid leukaemia

Aim-To evaluate the haemopoietic function of bone marrow blood forming cells in human chronic myeloid leukaemia (CML) by means of silver staining of nucleolar organiser region (AgNOR).Methods-Nucleoli were investigated in bone marrow blast cells and in erythroid, granulocytic, and megakaryocytic cells from 10 haematologically healthy subjects and from 26 patients with chronic myeloid leukemia (17 in benign phase, nine with blast crisis). The investigation was done before treatment, by means of a one step silver staining method. In every case 50 to 100 blasts, promyelocytes, myelocytes, immature (pronormoblastic and basophilic normoblastic) and mature (polychromatic normoblastic) erythroid elements, and megakaryocytes were evaluated for the mean numbers of nucleoli and for the average number of AgNORs per nucleus. Student's t test was used to compare the patient and control groups. Other statistical analyses were carried out by means of the computer assisted "HEMA" system.Results-Compared with controls, activation of NORs was noticed only in CML blasts, while there was a decrease in NORs in the erythroid elements, promyelocytes, and megakaryocytes. The AgNOR score of polychromatic normoblasts and megakaryocytes started to decrease in the benign stage of CML, whereas a similar decrease in pronormoblasts, basophilic normoblasts, and promyelocytes was detected only in patients with CML blast crisis.Conclusions-The loss of AgNOR sites in cell series in CML may be related to intrinsic defects in their proliferation.

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

Cell cycle-dependence of HL-60 cell deformability

In this study, the role of cytoskeleton in HL-60 deformability during the cell cycle was investigated. G1, S, and G2/M cell fractions were separated by centrifugal elutriation. Cell deformability was evaluated by pipette aspiration. Tested at the same aspiration pressures, S cells were found to be less deformable than G1 cells. Moreover, HL-60 cells exhibited power-law fluid behavior: mu = mu c(gamma m/ gamma c)-b, where mu is cytoplasmic viscosity, gamma m is mean shear rate, mu c is the characteristic viscosity at the characteristic shear rate gamma c, and b is a material constant. At a given shear rate, S cells (mu c = 276 +/- 14 Pa.s, b = 0.51 +/- 0.03) were more viscous than G1 cells (mu c = 197 +/- 25, b = 0.53 +/- 0.02). To evaluate the relative importance of different cytoskeletal components in these cell cycle-dependent properties, HL-60 cells were treated with 30 microM dihydrocytochalasin B (DHB) to disrupt F-actin or 100 microM colchicine to collapse microtubules. DHB dramatically softened both G1 and S cells, which reduced the material constants mu c by approximately 65% and b by 20-30%. Colchicine had a limited effect on G1 cells but significantly reduced mu c of S cells (approximately 25%). Thus, F-actin plays the predominate role in determining cell mechanical properties, but disruption of microtubules may also influence the behavior of proliferating cells in a cell cycle-dependent fashion.

Cytogenetic study of circulating blasts in leukemias

A special cultivation technique of separated blasts of peripheral blood in suspension culture has been used for cytogenetic diagnosis of patients suffering from acute nonlymphocytic leukemia, chronic myeloid leukemia, and refractory anemia with excess of blasts. Twenty-three patients were examined; in ten cases isolation of blasts was performed on Ficoll-Verografin and in the remaining 13 patients further separation of T-lymphocyte precursors by means of sheep erythrocytes was performed. Remarkably, a 100% success rate was attained in all cultivations. The optimum harvesting time was 72-96 hours; the rate of cell division per cultivation was determined by means of bromodeoxyuridine incorporation; second mitoses were revealed only after 96-hour cultivation. In all patients, except one, abnormal karyotypic changes were ascertained in separated blasts of peripheral blood cultivations. In most cases the morphology of chromosomes obtained from separated blasts of peripheral blood cultivations was of excellent quality.

Bone marrow biopsy instead of 'marrow juice' for cell kinetic analysis. Comparison of bone marrow biopsy and aspiration material

Since cell kinetic bone marrow studies have so far exclusively been carried out on aspiration material and have yielded inconsistent or even contradictory results, we investigated the adequacy and reliability of aspirates for cell kinetic analyses in comparison to biopsies. Paired samples of bone marrow (133) were taken simultaneously by aspiration and Jamshidi biopsy from 48 patients with acute leukemias and 67 patients with non-leukemic disorders. Cell kinetic analysis by (1) flow cytometry (FCM) of cellular DNA and RNA content, (2) autoradiography for [3H]TdR pulse labelling indices and (3) liquid scintillation counting of [3H]TdR uptake revealed significantly higher values in biopsies (p less than 0.001) exceeding the corresponding results from aspirates on average by factors of 1.65 for FCM S-phase index, 1.90 for G0/1 cells with high RNA content, 1.82 for [3H]TdR LI and 1.90 for [3H]TdR uptake. In more than 70% of all samples results from biopsies were 1.1-11.4 times higher, indicating that aspirates were equivalent to biopsies in fewer tan 30% of cases. Cell kinetic analysis in vitro blood/biopsy mixtures and measurements of DNA synthesis rate in corresponding aspirates and biopsies revealed that these discrepancies are due to the contamination of aspirates with non-proliferating nucleated blood cells. Biopsy, however, was found to provide representative and reproducible sampling of marrow for cell kinetic studies and should replace the presently used aspirate already characterized as "unreliable marrow juice" by Dameshek et al. in 1937 [18].

Staging of chronic myeloid leukaemia

The prognostic value of nine clinical and haematological features, recorded at diagnosis in chronic myeloid leukaemia (CML), was analysed in two distinct series of patients. One series (116 cases) was collected at a single hospital over a 12-year period. The second series (139 cases) was collected from a multicentre trial over a 20-month period. Six features were associated with a poor prognosis: splenomegaly (more than 15 cm below the costal margin), hepatomegaly (more than 6 cm below the costal margin), thrombocytopenia (< 150 X 10(9)/l) or thrombocytosis (> 500 X 10(9)/l), a leucocyte count above 100 X 10(9)/l, peripheral blood non-granulated precursors (blast cells) above 1%, and peripheral blood granulated precursors (promyelocytes and myelocytes) above 20%. Depending on the number of negative prognostic factors, patients were divided into three categories: group I (0 or 1 factor), group II (2 or 3 factors) and group III (4,5 or 6 factors). Survival was significantly different in the three groups (P < 0.0005), and this was independent of age (below and above 50). The prognostic value of the classification was confirmed in a third series of 153 patients. We suggest that this classification provides a useful tool to identify prognostic categories in CML, and thus allows a proper allocation of patients to different therapies.

Persistence of nucleolar RNA-rich structures and Ph1 duplication in the blastic crisis of chronic myeloid leukaemia

Nucleolar persistence in metaphase plates is a feature observed in most of the cells in neoplastic processes. Pathological persistence or fragmentation of the nucleoli is thought to be the cause of some numerical chromosomal aberrations due to non-disjunction of the chromatids, with particular involvement of the satellite chromosomes. Thus, a combined selective staining of both the nucleoli (amido black 10B according to Mundkur and Brauer's cytochemical technique) and the chromosomes (neutral red) was applied to the metaphase plates of patients with chronic myeloid leukaemia in the blastic crisis. Duplicated Ph1 was associated with amido black-stained areas at a very high rate in some cases. Since the blastic crisis in chronic myeloid leukaemia is characterized by the appearance of an increased number of immature, highly nucleolated cells, these findings lend support to the hypothesis that the duplication of the Ph1 represents a feature possibly favoured by the pathological persistence of nucleolar RNA-rich structures in the metaphase.

Morphologic studies of the erythropoietic part of bone marrow in myeloid leukaemias

The erythropoietic part of the bone marrow has been morphologically analyzed in 147 patients with various forms of myeloid leukaemias and in 20 healthy controls. In all the patients the percentage of basophilic erythroblasts was abnormally high and correlated to elevated mitotic indices. Megaloblastic changes were found to be relatively common in the patients. All these findings are compatible with an ineffective erythropoiesis where the normal differentiation towards more mature erythroblasts becomes in creasingly blocked during the course of the disease regardless of the type of myeloid leukaemia.

A quantitative assessment of neutrophil marrow in seven patients with chronic granulocytic leukaemia

Neutrophil marrow cellularity was determined in seven patients with chronic granulocytic leukaemia (CGL). The size of the mitotic pool (promyelocytes and myelocytes) and the number of metamyelocytes and bands and of segmented neutrophils in the postmitotic pool were determined from measurements of neutrophil--erythroid ratios in marrow biopsy sections and ferrokinetic estimates of marrow normoblasts. A section mitotic index was calculated in each patient from the numbers of mitotic figures and mitotic pool cells counted on marrow sections. Basal values previously established in normal subjects for the mitotic pool, for metamyelocytes and bands, and for segmented neutrophils, were 2.11 +/- 0.36 x 10(9) cells/kg, 3.33 +/- 0.61 x 10(9) cells/kg, and 2.26 +/- 0.42 x 10(9) cells/kg, respectively (+/- 1 SD, n = 13). The basal section mitotic index was 0.07 +/- 0.01 (+/- 1 SD, n = 13). In the seven patients with CGL the mitotic pool comprised 3.71--25.70 x 10(9) cells/kg, metamyelocytes and bands 7.70--51.02 x 10(9) cells/kg, and segmented neutrophils 3.45--28.81 x 10(9) cells/kg. Mitotic indices ranged from 0.04 to 0.10. No relationship was found between marrow cellularity and blood neutrophil count. A negative correlation existed between mitotic pool cellularity and mitotic index (r = -0.76, n = 7 pairs). The results provide quantitative affirmation of neutrophil marrow hyperplasia and of increased neutrophil production by the marrow in CGL.

Mitotic activity in myeloid leukaemias. A study of 277 cases

The proportions of myeloblasts, promyelocytes, myelocytes and promonocytes within the granulopoietic precursor pool of the bone marrow and mitotic indices (MI) of the precursor cells were determined in 277 patients with various forms of myeloid leukaemias. The MI of the leukaemic patients were significantly lower than those of 20 normals. Thus the median MI in 186 cases of acute myeloid leukaemias was 0.68%, compared with 1.0% in 85 cases of chronic leukaemias and 1.2% in the normals. Separate MI of the different leukaemic precursor cells were counted in 21 cases of acute myeloid leukaemias and these indices were lower than those of the corresponding normal cells. There were significant differences between the different groups and subtypes of leukaemias and it is suggested that mitotic countings might be of diagnostic and prognostic significance.

Mitotic activity of the granulopoietic precursor cells in the peripheral blood in chronic myeloid leukaemia

The mitotic indices (MI) of granulopoietic precursor cells in peripheral blood and bone marrow were studied in 38 patients with typical chronic myeloid leukaemia (CML) in the chronic phase. The MI in the peripheral blood were very low, in the median 0.07%, compared to those in the bone marrow with a median of 1.07%. The blood MI were significantly increasing with raising WCC and the values of the MI above the median were combined with short survival times. The bone marrow MI were negatively correlated to the blood MI and it is suggested that this is a sign of an increased exchange of cells between bone marrow and blood.

Arabinosyl cytosine in chronic myeloid leukaemia: evidence for high cytokinetic sensitivity of myeloblasts

The effect of a single and of repeated i.v. push dose(s) of Arabinosyl Cytosine (ARA-C) has been investigated in 9 chronic myeloid leukaemia (CML) patients in non-blastic phase. This was done by determining separately the relative compartment size, the mitotic index (IM), and the in vitro 3H-TdR labelling index (IL) of marrow and blood myeloblasts (MB) and promyelocytes plus myelocytes (PMC + MC), before and at intervals after the drug. After a single dose of ARA-C, the IL of marrow MB declines rapidly, and recovers thereafter, often with an overshoot at 15 h. After 2 to 4 doses of ARA-C, the IL of marrow and blood MB rises by a factor of 2 to 3, and is maintained at a plateau during further treatment. The behaviour of the IL of blood MB is not always the same as that of marrow MB. The IM of marrow MB does not rise proportionally to the IL, and sometimes is even found to be decreased. It is suggested that these kinetic perturbations reflect an accumulation of MB in S-phase where many but not all of them are trapped and sooner or later die off. With a few exceptions, ARA-C induces only milder kinetic perturbations in marrow and blood PMC+MC. The overall results of this study are in agreement with the generally accepted mechanism of action of ARA-C (S-phase specific effector agent), and with studies that indicate that the effect of ARA-C depends on the growth pattern and on the degree of maturation of the target cells. It is suggested that a proper evaluation of ARA-C on a cell population should take into account the existence of different cell pools, provided with different proliferative activity and potential, and with variable degrees of maturation.

Cell proliferation and protein synthesis in human leukaemic myeloblasts after cytosine arabinoside therapy

The effect of a single intravenous bolus injection of cytosine arabinoside (ARA-C) on the cytokinetics and 3H-leucine uptake of leukaemic myeloblasts in bone marrow and blood was studied at intervals up to 96 h after ARA-C in five patients with previously untreated acute myelogenous leukaemia. An early decrease in mitotic index and in 3H-thymidine labelling was observed in four of five patients and pretreatment values were reached again within the observation period. Changes suggesting synchronization were not observed. ARA-C induced a marked decrease in protein synthesis in the leukaemic myeloblasts as estimated from either a decrease in the 3H-leucine labelling index or the mean grain count of 3H-leucine labelled cells. It is suggested that ARA-C is incorporated also by cell which are not in S-phase and has a prolonged biochemical effect on the leukaemic cells.

Originalarbeiten

In 5 cases of polycythaemia vera and 2 cases with other myeloproliferative disorders accompanied by thrombocythaemia (megakaryocytic myelosis), the megakaryocytes were differentiated and studied by use of the combined application of cytophotometric determination of the DNA content and autoradiography with tritiated thymidine (3H-TdR) in vitro. A shift to the right of the megakaryocyte series, occurence of high polyploidy cells at 64c and a decrease of the 3H-TdR-labeling indices were observed. The data suggest a disturbance of the rhythmical polyploidization of the megakaryocytes, consisting of an elevated proportion of rest cells at the different ploidy stages. The maturation capacity of megakaryocytes may be related more to the resting than to the DNA synthesizing cells.