Predicting relapse of human leukemia by means of premature chromosome condensation

Prophasing interphase chromatin for assessing genetic damages-The evolution, applications and the future prospects

Premature chromosome condensation (PCC) involves induction of near-chromosome-like morphology to interphase chromatin. Experimental induction of PCC was achieved by somatic cell hybridization (SCH), an approach which evolved into a chemical-induction process. PCC presents most probably the only way in which cytogenetic assessment of damages can be analyzed in special situations such as availability of limited numbers of sample cells and for cells which have lost their ability to divide. Initial experiments on PCC were reported in late 1960s and the technique has evolved into one with wide range of applications owing to its increased efficiency in detecting primary DNA damages. Biodosimetry remains as the primary area which utilizes PCC technique to the maximum efficiency with several multiple-groups participating in collaborative exercises for biodosimetric applications. However, in spite of the advantages that the technique offers, it is yet to reach its full potential. This is due to the inherent limitations of the manner in which PCC is induced currently; by the somatic cell hybridization and chemical-induction processes. An approach which combines these two would sure help in taking PCC to its highest potential as the preferred technique for assessment of primary DNA damages. We present the chronological events of evolution of the PCC technique along with its applications. Also, the limitations of the technique along with the suggestions for further refinement of the PCC technique are discussed.

Comparison of mitotic cell death by chromosome fragmentation to premature chromosome condensation

Mitotic cell death is an important form of cell death, particularly in cancer. Chromosome fragmentation is a major form of mitotic cell death which is identifiable during common cytogenetic analysis by its unique phenotype of progressively degraded chromosomes. This morphology however, can appear similar to the morphology of premature chromosome condensation (PCC) and thus, PCC has been at times confused with chromosome fragmentation. In this analysis the phenomena of chromosome fragmentation and PCC are reviewed and their similarities and differences are discussed in order to facilitate differentiation of the similar morphologies. Furthermore, chromosome pulverization, which has been used almost synonymously with PCC, is re-examined. Interestingly, many past reports of chromosome pulverization are identified here as chromosome fragmentation and not PCC. These reports describe broad ranging mechanisms of pulverization induction and agree with recent evidence showing chromosome fragmentation is a cellular response to stress. Finally, biological aspects of chromosome fragmentation are discussed, including its application as one form of non-clonal chromosome aberration (NCCA), the driving force of cancer evolution.

Is there an accumulation of cells during G2 in some acute lymphoblastic leukaemias?

In some cases of acute lymphoblastic leukaemia (ALL) the percentage of cells in G2 + M is higher than anticipated when compared with the percentage in S phase. This increase in G2 + M, as detected by flow cytometry measurement of DNA content, may be due to an accumulation of cells, either in G2 or during the end of S phase; it may also be related to the existence of small tetraploid clones generally ignored by cytogeneticists. In order to identify possible subpopulations of cells with a DNA index greater than or equal to 2.0, we have compared the results of a cytogenetic analysis to the G2 + M values. We have also studied the distribution of S phase cells in 24 cases of ALL by incorporating 5-bromodeoxyuridine, labelling the cells by indirect immunofluorescence, and analysing them by flow cytometry after propidium iodide staining. The distribution of cells during S phase was quantified: no accumulation of cells was ever observed at the end of S phase. The question of the existence of small tetraploid clones, G2 arrested cells or cells with a G2 elongation remains open. However, we feel that it is more probable that, in this pathology, an elongation of the duration of G2 occurs.

Colony-stimulating factors (rhG-CSF, rhGM-CSF, rhIL-3, and BCGF) recruit myeloblastic and lymphoblastic leukemic cells and enhance the cytotoxic effects of cytosine-arabinoside

Prognostic models for acute myeloid and lymphoid leukemias are presented that demonstrate that cell kinetic quiescence in acute leukemia is associated with poor response to chemotherapy, short remission duration, and survival. Recruitment of cells into the cell cycle should therefore enhance cytotoxic effects of cell cycle - specific chemotherapeutic agents. We previously demonstrated recruitment of myeloid leukemic cells by cytokines. We have now investigated whether recruitment can be used to increase cell killing by cytosine arabinoside (Ara-C). Blast cells from 16 acute leukemias were stimulated with cytokines as follows: 13 acute myeloid leukemias (AML) and 3 chronic myeloid leukemia (CML) in blastic phase (1 lymphoid, 2 myeloid) were treated with recombinant human granulocyte colony stimulating factor (rhG-CSF), recombinant human granulocyte-macrophage colony stimulating factor (rhG-CSF, AMGEN, 500 U/ml each), and recombinant human interleukin-3 (rhIL-3, IMMUNEX, 20 ng/ml), alone and in combination. After 48 h, at the time of maximal DNA synthesis, Ara-C (10(-3) M) was added and cell counts, cytokinetics (DNA/RNA, DNA/bromodeoxyuridine and DNA/Ki67 flow cytometry), and cell viability/clonogenicity (fluorescein diacetate/propidium iodide exclusion flow cytometry) were investigated. In all 13 cases of AML recruitment was found; in 6 of these cases over a three fold increase in S phase (P = 0.008) and a significant (P = 0.004) depletion of G0 was demonstrated. In 9 of 13 patients with AML, the effect of Ara-C was investigated, and in 3 of 5 patients with over three fold increase in S phase, Ara-C toxicity was enhanced. None of the patients with less than a three fold increase in S phase and no demonstrable recruitment from G0 had increased Ara-C cytotoxicity. Ara-C cytoreduction was paralled by reduction in clonogenicity as demonstrated by fluorescein diacetate/propidium iodide (FDA/PI) flow cytometry. Four samples of acute lymphoblastic leukemia (ALL) were treated with low molecular weight B-cell growth factor (15 kDa) and recruitment of aneuploid cells from G0 to G1 was found in all patients (from 19.3% to 84.9%). These results indicate that recruitment of leukemic cells is inducible by cytokines and that the cytotoxicity of cell cycle-specific drugs such as Ara-C can be increased. This concept is presently being tested in vivo.

Premature chromosome condensation in childhood acute lymphoblastic leukaemia: correlation of proliferative potential index in blood and marrow

The proliferative potential index (PPI), which is the proportion of all GI cells which are in late GI, has been shown to reflect disease state in patients with acute leukaemia. We have determined PPI in paired blood and marrow samples from children with acute lymphoblastic leukaemia (ALL) at different stages of the disease, and found a close correlation between blood and marrow PPI irrespective of disease stage. Therefore blood PPI can replace marrow PPI for monitoring disease control in ALL.

In vivo biologic activities of recombinant human granulocyte-macrophage colony-stimulating factor

We evaluated the biologic effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) in 25 patients with malignancy and/or bone marrow failure of diverse etiologies. The continuous infusion of GM-CSF (15 to 500 micrograms/m2/day) elicited marked leukocytosis (2- to 70-fold increase), consisting primarily of neutrophils, eosinophils, and monocytes. Six patients with cytopenias experienced a multilineage response characterized by significant increases in platelet counts and improvement in erythropoiesis. Response in blood counts was accompanied by significant increases in bone marrow cellularity, myeloid:erythroid cell ratios, and frequency of cycling progenitors, indicating an effect at the stem cell level. By premature chromosome condensation analysis, neutrophils from patients with myeloid diseases were found to be derived from normal as well as abnormal clones. Side effects were generally mild and commonly included constitutional symptoms and bone pain. These results indicate that GM-CSF is a significant stimulus for hematopoiesis in vivo and might play an important role in several clinical arenas.

Improvements in the premature chromosome condensation technique for cytogenetic analysis

In this paper we report a combination of procedures that serve to improve the usefulness of the technique of premature chromosome condensation in cytogenetic investigations. The mitotic inducer population was preincubated in high concentrations of BrdU, and the duration of fusion was increased to yield more discrete prematurely condensed chromosomes (PCC). After fusion, chromosome preparations were treated with a combination of G- or C-banding techniques and differential staining techniques. This combination of procedures allowed unequivocal distinction between the PCC and mitotic inducer chromosomes and yielded banded G1 and G2 PCC suitable for routine cytogenetic investigations.

Survival in acute myeloblastic leukemia is not prolonged by remission maintenance or early reinduction chemotherapy. The Toronto Leukemia Study Group

A role for post-induction chemotherapy for adult patients with acute myeloblastic leukemia in remission has not been established. We have studied 125 patients with acute myeloblastic leukemia in complete remission to determine the effect on survival of remission maintenance therapy and of early reinduction therapy given at the time of predicted imminent relapse. Following remission induction with 6-thioguanine, cytosine arabinoside and daunorubicin (TAD), all patients received consolidation therapy with these same three drugs. Forty-three patients were randomized to arm A, continuing chemotherapy; 40 patients were randomized to arm B, no further chemotherapy until morphological relapse; and 42 patients were randomized to arm C, no further chemotherapy until an increase in myeloblast associated antigens was detected in bone marrow by means of antimyeloblast heteroantisera. The median durations of complete remission, age adjusted, for the three groups are not significantly different: 15.7 months for group A, 16.2 months for group B and 14.1 months for group C. The age adjusted median survivals for the three groups are also not significantly different: 17.6 months for group A, 21.8 months for group B and 18.8 months for group C. Quality of life was determined to be superior for patients having no further maintenance therapy (arms B and C). We conclude that our patients receiving induction and consolidation therapy with TAD did not benefit from remission maintenance or early reinduction chemotherapy, and had an improved quality of life if no maintenance therapy was given.

Effects of recombinant human granulocyte-macrophage colony-stimulating factor in patients with myelodysplastic syndromes

The myelodysplastic syndromes are characterized by ineffective hematopoiesis and refractory cytopenias. In an attempt to improve hematopoiesis, we administered recombinant human granulocyte--macrophage colony-stimulating factor (GM-CSF) to eight patients with myelodysplastic syndrome, as part of a Phase I trial. The GM-CSF was given by continuous intravenous infusion daily for two weeks and then again after a two-week rest period. Over the entire dose range tested (30 to 500 micrograms per square meter of body-surface area), treatment was associated with marked increases in peripheral-blood leukocytes (5- to 70-fold), including granulocytes (5- to 373-fold), in all eight patients. The absolute number of monocytes, eosinophils, and lymphocytes increased in all patients. Three of eight patients also had 2- to 10-fold increases in platelet counts and improvement in erythropoiesis, with the result that two of three patients who had required red-cell and platelet transfusions no longer needed them (at 20 to 27 weeks of follow-up). Treatment was also associated with increased marrow cellularity and a decreased percentage of blasts in the bone marrow of patients with excess blasts, resulting in an increase in the ratio of differentiated myeloid cells to immature myeloid cells. We observed relatively few side effects, but bone pain was dose-limiting when it was associated with high white-cell counts. Our results showed that GM-CSF is a potent stimulator of hematopoiesis in vivo and may produce hematologic improvement in the short term (8 to 32 weeks of observation) in patients with myelodysplastic syndrome. More experience, with longer follow-up periods, will be necessary to assess the long-term safety and efficacy of this new treatment.

Premature chromosome condensation as a predictive indicator of relapse in children and adolescents with acute leukemia: initial observations

Premature chromosome condensation has been used to determine a proliferative potential index (PPI) in a study of children in leukemia remission at varying times during the disease. Values 35% and greater were considered predictive of relapse. Such values preceded relapse with a mean of 5 months in acute lymphoblastic leukemia (ALL) patients who had previously relapsed and in myeloid leukemia patients. ALL patients followed from diagnosis and children off therapy had fluctuating and false predictive PPI values preceding long courses of continued remission. This study suggests that the PPI as a predictive indicator for relapse may be useful for patients with ALL who have previously relapsed and for patients with myeloid leukemias. Future exploration to further evaluate this mechanism of prediction is to be attempted by investigating the ability to obtain similar and more detailed information through the use of peripheral blood rather than bone marrow samples.

Methodology of premature chromosome condensation and its potential for relapse prediction in acute leukemia of children and adolescents

Premature chromosome condensation has been examined as a method for measuring the proliferative potential of bone marrow cells derived from children with acute leukemia with the intention of finding a predictor of relapse. A proliferative potential index (PPI) has been determined for patients with active disease at diagnosis and relapse, as well as at onset of remission and at extramedullary relapse. A modification of the technique established by Hittelman is described, which can be easily performed by the leukemia cytogeneticist. A PPI of 35% or greater is usually obtained for patients at diagnosis or in relapse. At the onset of remission, the PPI declines to values significantly below 35% and during extramedullary relapse the value of the PPI is near normal (12%). The method for the determination of the PPI is given in detail.

Premature chromosome condensation--studies on human metastatic carcinoma cells

Utilizing the phenomenon of premature chromosome condensation (PCC) studies were carried out on interphase chromatin of metastatic cells from 52 cancerous effusions obtained from 45 patients presenting with various solid carcinomas. A highly individual pattern of distribution of the various interphase stages was detected, reflecting the heterogeneity of human solid tumors in an advanced stage. Nevertheless a variety of clinical, biologic, and technical factors were examined for their possible influence on these PCC patterns. The duration in culture was one of the influencing factors, as were the time lapse between the first diagnosis and the sampling of the respective effusion, or the nature of cytostatic therapy. Cytogenetic equivalents of gene amplification, as represented by "double minutes", could be found in the prematurely interphase chromatin of 35 of the 52 effusions. G1-PCC proved to be most reliable with regard to screening of double minutes. In addition, an adequate quality of Giemsa banding was achieved in PCC of 21 out of 24 effusions yielding a sufficient number of well-spread PCC. In six of these 21 cases PCC was superior to metaphase analysis in obtaining karyotypes, while the same was true for 14 of the 52 effusions screened for double minutes. Thus the PCC technique was shown to be an indispensable additional source of cytogenetic information in cells of human solid tumors.

The technique of premature chromosome condensation to study the leukemic process: review and speculations

The technique of premature chromosome condensation involves the fusion of mitotic cells with interphase cells resulting in the immediate condensation of the interphase chromatin into discrete chromosome units, the prematurely condensed chromosomes (PCC). The ability to visualize the interphase chromosomes of bone marrow and blood cells by this technique has proved useful in the study of human leukemia. This article describes how the PCC technique has been used to predict clinical outcome as well as gain insight into the biology of leukemia.

Predictors of response of acute nonlymphocytic leukemia

Given the time and effort expended by investigators and given the large numbers of patients studied, there are disappointingly few "predictors" of response. From the clinical perspective, aside from performance status, age, prior history of toxic exposure, and grossly abnormal organ function, there are essentially no reliable indicators of the likelihood of a patient surviving remission induction therapy. The absence of such indicators might reflect the fact that without grossly abnormal organ function, all patients generally begin with an equal possibility of survival and that events which occur during therapy determine survival. One thing is certain, death directly attributable to leukemic cell overgrowth despite chemotherapy is an extremely rare event. Hence, therapeutic inadequacy in this sense, at the time of initial diagnosis, is not a common cause of treatment failure. Studies aimed at the prediction of leukemic cell responsiveness to therapy have been plagued by two general problems. The first is that the drug sensitivity assays have been quite primitive. For example, the ability of a cell to take up a drug is not synonymous with sensitivity to that drug. Additionally, tests which are dependent upon assays capable of making measurements in only a small subpopulation of cells, such as in vitro clonogenic assays, are likely to have only limited applicability. On the other hand, assays which measure the properties of the leukemic cell population as a whole are incapable of recognizing arabinoside therapy have provided data which suggest that in addition to patient survival three conditions must be satisfied if a complete remission is to occur: the pretherapy leukemic cell mass must be moderate or low, an adequate number of cells must be synthesizing DNA, and cytosine arabinoside must produce significant inhibition of DNA synthesis in vitro. Each factor is consistent with what is known about cytosine arabinoside: it is an S-phase-specific agent which must be incorporated into DNA in order to kill leukemic cells. When the relationship between these same factors and response to combination chemotherapy were studied, not unexpectedly, no relationship was discerned. Finally, in this setting pharmacokinetic studies have demonstrated that the amount of araCTP formed in leukemic cells in vivo when doses of 2 g and 3 g/m2 are administered are indistinguishable, thereby explaining the clinical equivalence of these two dosage levels.(ABSTRACT TRUNCATED AT 400 WORDS)

High-performance liquid chromatographic assay of 6-methylthioguanine, a major metabolite of 6-thioguanine, in urine

A flow-fluorimetric high-performance liquid chromatographic assay for 6-methylthioguanine in urine has been developed. This compound is a major catabolite of 6-thioguanine, an important drug in cancer chemotherapy. The metabolite was extracted from alkaline urine with ethyl acetate which was injected onto a reversed-phase high-performance liquid chromatographic system for separation and detection. The method is simple, rapid and sensitive to below 500 ng ml-1 which is below the levels encountered following a therapeutic dose of 6-thioguanine. Another metabolite was chromatographically separated from 6-methylthioguanine and partially characterised.

Cell-cycle, protein content, and nuclear size in acute myeloid leukemia

Simultaneous analysis of DNA and cellular proteins provides information on cell proliferation and metabolism. Cellular protein content coupled with nuclear geometric parameters can be used to evaluate cellular maturation and differentiation. In this study, leucoblasts from 50 cases of adult acute myeloid leukemia were analyzed by flow cytometry, and semiautomatic morphometry was performed on bone marrow smears. Ethanol-fixed bone marrow blast cells were stained for DNA with propidium iodide (PI) and for proteins with fluorescein isothiocyanate (FITC). On the resulting FITC versus PI histograms we defined the cells with low protein content which are associated with a nonproliferating subpopulation (LPC fraction). Low protein content fraction and S-phase are correlated (p less than 0.01). The LPC fraction values are more dispersed than S-phase values and thus should indicate more clearly eventual differences between cellular populations. This hypothesis has been tested with the prognostic significance of cell-cycle variables: The LPC fraction was significantly higher in the complete remission group than in the other (p less than 0.01), while S-phase did not show any difference. The peak value of the protein content histograms is significantly lower in the granulocytic leukemias (M1, M2, M3) than in the leukemias with a monoblastic component (M4, M5). Furthermore, we showed that the differentiation and the maturation of the myeloid blast cells modify the nuclear size. The combination of these two parameters provides useful information for cytological classification.

Evolution of oligoleukemia

Chronic lithium administration to 22 patients with oligoleukemia did not alleviate cytopenia or stimulate bone marrow proliferative activity. The authors identified, however, pretreatment characteristics discriminating two evolutionary endpoints of oligoleukemia (marrow failure, 10 patients; overt acute leukemia, 12 patients): higher marrow leukemic infiltrate, normal myeloid precursor proportion, platelet count, and female sex all favored eventual transition to overt leukemia which, in comparison with marrow failure, was associated with a significantly longer survival duration from symptoms. For patients developing overt leukemia, survival from diagnosis was inversely correlated with the degree of marrow leukemic infiltrate. The lack of lithium responsiveness in oligoleukemia is consistent with the concept of differentiated leukemia with abnormalities either at the level of a lithium-responsive adherent cell elaborating colony stimulating activity (CSA) or at the level of CSA-responsive CFUs.

Cytogenetic analysis of urologic malignancies: study of tumor colony forming cells and premature chromosome condensation

We have utilized a human tumor clonogenic assay to grow, and subsequently cytogenetically analyze, tumor colony forming cells from human urologic malignancies. Results following chromosome banding analysis are presented from 4 cases of transitional cell carcinoma and 1 case of renal cell carcinoma. Preliminary evidence suggests a possible association between the loss of chromosome 8 and progression or recurrence of transitional cell carcinoma. Additionally, we have utilized the technique of premature chromosome condensation to identify the interphase chromatin profile of urothelial cells obtained by cystoscopy from 8 patients with transitional cell carcinoma and compared these results to urothelial cells obtained from 7 control patients. This study demonstrates that cells obtained from urologic cancers contain a high proportion of cells in late G1, while normal urothelial cells are usually found in the early G1 phase of the cell cycle. Statistical correlation of premature chromosome condensation analysis suggests this method may be a useful adjunct to routine histopathology in discriminating between normal and cancerous urothelium.

A simple method for premature chromosome condensation induction in primary human and rodent cells using polyethylene glycol

Even though polyethylene glycol (PEG) has been shown to be a potent fusogen, it has not been widely exploited as an alternative to the Sendai virus for premature chromosome condensation (PCC) induction. A simple, rapid, and reproducible PEG protocol for primary cells in suspension is presented which allows satisfactory cell fusion and PCC indices, giving at the same time high cell viability and low giant, multinucleated cell formation. Technical details for PEG-mediated fusion and premature chromosome condensation induction in human and rat lymphocytes, rodent spleen cells, and spleen and whole body cells of newborn mice are provided. Further applications of the method are suggested.

Circulating immune complexes and the prognosis of acute myeloid leukemia

We studied the relation between the clinical course and the presence of circulating immune complexes at diagnosis and/or during complete remission in 186 patients with acute myeloid leukemia. Patients with immune complexes at diagnosis had significantly fewer complete remissions (32 vs. 94 per cent), remissions of shorter duration (median, 4.3 vs. 15.0 months), and shorter survival times (median, 1.8 vs. 22.3 months) than patients without such complexes (all comparisons, P less than 0.01). All patients with immune complexes during the first two months of remission remained in remission for less than six months, whereas only 11 per cent of patients without complexes within this period had such early relapse. Of 23 patients who relapsed after long remissions, 18 (78 per cent) had immune complexes that preceded hematologic evidence of relapse by three weeks to six months (median, 3.7 months). These findings suggest that circulating immune complexes may reflect an important aspect of the pathophysiology of acute myeloid leukemia, and that measurement of these complexes can provide useful prognostic information at diagnosis and during remission.

2' and 3' ribonucleoside monophosphate in leukocytes of acute myeloid leukemia: markers for early diagnosis of relapse

Levels of 2' and 3' purine and pyrimidine ribonucleoside monophosphates (2'-, 3'-NMP) in leukocytes from blood and/or bone marrow were measured in three adult patients with acute non-lymphoblastic leukemias. The measurements of 2'-, 3'-NMP were made by high-performance liquid chromatography (HPLC) at various times in the course of the disease. Complete remission (CR) was obtained for all three patients but two of these have since died after relapsing at 8 and 9 months, respectively. The third patient remains in CR at 1 1/2 year. The levels of 2'-, 3'-NMP in the leukocytes of the patient remaining in remission have not changed since the beginning of his remission. However, in the patients who relapsed 2'- and 3'-NMP levels increased first in bone marrow than in blood leukocytes. These increases occurred about 3 months before the relapse was detected by morphological criteria. These data suggest that 2'-, 3'-NMP measurements may have a prognostic value if used to monitor patients with acute myeloid leukemia in CR.