DNA repair mechanisms and acute myeloblastic leukemia

DNA repair mechanisms play a vital role in maintaining genomic integrity. With the wealth of knowledge gained recently on these processes it is becoming clear that defects in repair proteins and proteins associated with the regulation of repair are connected to many different human diseases including cancer. This paper has aimed to review the four major DNA repair processes and in particular concentrate on their association with acute myeloblastic leukemia (AML).     

Chronic neutrophilic leukemia with acute myeloblastic transformation

We report a rare case of chronic neutrophilic leukemia (CNL) which terminated in acute myeloblastic transformation 3 years after the onset of the disease. The increased leukocytes were mainly neutrophils at various maturational stages until 1 month before transformation without dysplastic hematopoietic cells or other myeloproliferative disorders. Repeated analyses for the Philadelphia chromosome (Ph1), rearrangement of the BCR gene or chimeric BCR/ABL mRNA, major, minor and mu, were negative. Genomic analysis of granulocyte colony-stimulating factor (G-CSF) receptor did not reveal any abnormality. The clinical manifestations were characterized by hyperleukocyte syndrome with respiratory distress and ischemic legs with gangrene.     

Double minute chromosomes in acute myeloblastic leukemia

Two patients with acute myeloblastic leukemia (AML) with double minute chromosomes (dmins) are described. One patient had dmins in approximately one-third of bone marrow cells examined at diagnosis; no other karyotypic changes were observed. The dmins disappeared when the patient achieved a complete remission. The second patient developed acute leukemia as a second cancer, having previously received radiotherapy and chemotherapy for a breast carcinoma. At the time of diagnosis of AML, the patient exhibited dmins in 12% of bone marrow cells; other complex karyotypic changes were observed. Data on the clinical and cytogenetic features of these cases are compared with those of other reported cases of acute leukemia with dmins. The possible biologic and clinical significance of dmins in acute leukemia is discussed.     

Chemoimmunotherapy for maintenance in acute myeloblastic leukemia.

Of 30 adult patients with acute myeloblastic leukemia, 14 achieved complete remission. Eight of these were given chemoimmunotherapy for maintenance. The immunotherapy consisted of intradermal pooled allogeneic leukemic cells (snap-frozen irradiated) and BCG vaccine given by Heaf gun, given twice in 4 weeks. The chemotherapy was given for 1 week in 4 weeks. The median duration of remission in these eight patients was 115+ weeks and the median duration of survival was 147+ weeks. The other six patients who were given chemotherapy only for maintenance had a median duration of remission of 15 weeks and a median survival of 52 weeks. The two groups cannot be compared properly, however, as allocation of patients was not random, and the chemotherapy differed significantly.     

Phase II study of aclarubicin in acute myeloblastic leukemia

Aclarubicin is a new anthracycline antibiotic that produces substantially less cardiotoxicity in animals that does doxorubicin. Based upon prior Phase I and II trials in leukemia, a Phase II study in acute myeloblastic leukemia was developed to assess the response rate and toxicity in previously treated patients. Forty patients received aclarubicin 100 mg/m2 per day X 3 with repeated course on days 14-16 if marrow hypoplasia was not produced. Complete responses were achieved in 27.5% (11/40) with durations of 1.5, 2, 2, 2, 3, 3+, 4, 5+, 32+, 33+, and 34+ months. Toxic effects of this therapy included severe neutropenia and thrombocytopenia, nausea/vomiting, mucositis, and diarrhea. No patient developed significant changes in the left ventricular ejection fraction, as measured by radionuclide angiography, or any clinical cardiac symptoms. Alopecia was minimal. Aclarubicin can produce a significant response rate in previously treated patients with acute myeloblastic leukemia and should be considered for study in initial therapy.     

The rheumatological prodrome: an unusual inaugural manifestation of acute myeloblastic leukemia

Uncommon patterns of presentation of acute leukemia pose diagnostic problems. A rheumatological prodrome in acute myeloblastic leukemia is very rare. We describe one such patient who had a normal haemogram. Bone marrow examination done later revealed acute myeloblastic leukemia. The case is discussed with reference to literature.     

Clonal expansion and progression in acute myeloblastic leukemia.

Diseaes originating in pluripotent stem cells, then developing through clonal expansion and clonal progression may properly be grouped together because of their common features. Among these, AML appears to be unique by reason of the presence within the clone of a blast cell population. Studies of cellular composition and regulation in AML clones require assays that measure not only myelopoiesis but also blast cell proliferation. The relation of the blast population to other components of AML clones remains uncertain. Resolution of the uncertainty is important in considering therapeutic strategies.     

Molecular biology in acute leukemia

Acute leukemia is a clonal expansion of tumoral cells in bone marrow, blood or other tissues. The acute leukemias are classified as myeloid or lymphoid based on the lineage of the blast cells. Over the past three decades, remarkable advances have been made in the classification and treatment of acute leukemias. In the last years, the research into the molecular pathogenesis of acute leukemia has progressed. The knowledge of chromosomal translocations breakpoints and possible candidate oncogenes and tumor suppressor genes has allowed the integration of all these events into multistep cascades that impact specific signal transduction pathways and lead to leukemic transformation. Supported by an unrestricted educational grant by Bristol-Myers Squibb.     

The biology and therapy of adult acute lymphoblastic leukemia

BACKGROUND: Much progress has been made in understanding the biology of acute lymphoblastic leukemia (ALL). This has translated into the recognition of several subgroups of ALL and the institution of risk-adapted therapies. New therapies are emerging based on the definition of specific cytogenetic-molecular abnormalities. METHODS: A review from the English literature, including original articles and related reviews from Medline (Pubmed) and abstracts based on publication of meeting material, was performed. RESULTS: Changes in the pathologic classification of ALL have led to therapeutic consequences. Adaptation of successful treatment strategies in children with ALL has resulted in similar complete response rates in adults. Prognosis has especially improved in mature-B-cell and T-lineage ALL. The role of tyrosine kinase inhibitors in Philadelphia chromosome-positive ALL was evaluated in the current study. However, regardless of the ALL subgroup, long-term survival of adults is still inferior to that in children. CONCLUSIONS: Intense clinical and laboratory research is attempting to close the gap in outcome between children and adults with ALL. Investigations are focusing on 1) refinement of the basic treatment stratagem of induction, consolidation, and maintenance; 2) expansion of risk-based, subgroup-oriented therapies; 3) assessment of minimal residual disease, its impact on disease recurrence, and its practical implications in clinical practice; 4) salvage strategies; 5) the role of stem cell transplantation in ALL; and 6) the development of new drugs based on a better understanding of disease biology.     

Cytosine arabinoside phosphorylation and deamination in acute myeloblastic leukemia cells

Extracts of peripheral leukocytes from patients with AML and from controls were examined for enzymes involved in the metabolism of ara-C in order to investigate a possible relationship between enzymes activities and improvement of treatment with ara-C. The enzymes are deoxycytidine kinase and cytidine deaminase, which activates and inactivates ara-C respectively. Cytidine deaminase activity was found to be lower in AML cells than in normal cells, while deoxycytidine kinase was higher in AML cells. Furthermore, the ratio between kinase activity with ara-C as substrate and activity with deoxycytidine as substrate was higher in AML cells than in normal leukocytes. However, there was no significant difference between those patients with AML, who respond to ara-C treatment, and the patients who did not respond.The enzymatic differences between normal and AML leukocytes with regard to activity and substrate specificity might suggest that ara-C could be combined with advantage with deoxycytidine in the clinic.     

In vitro growth in acute myeloblastic leukemia: clinico-biological correlations

In the present review we analyse the current knowledge about the growth properties of AML progenitor cells and their relationship with other clinico-biological characteristics of the disease. Leukaemic colony forming unit L-CFU is considered to be the clonogenic cell in AML and more immature than the blast cell population. Our studies have shown that in leukaemic hematopoiesis colony forming cells can exist among both cell fractions CD34+ and CD34-. Optimal "in vitro" proliferation of L-CFU is dependent upon the addition of exogenous growth factors. However, it has been observed that leukaemic progenitor cells frequently display a certain degree of autonomous proliferation. In order to quantify the "in vitro" behaviour of L-CFU, we have explored 3 parameters: 1) plating efficiency (PE); 2) autonomous growth (AG); and 3) autonomous proliferative index (API) which was calculated as AG divided by PE and we have correlated them with other clinico-biological data. According to the FAB classification we could observe that patients with M3 subtype showed an higher PE than other AML subgroups and a significantly lower API. Regarding CD34 expression we observed that AG was enhanced in CD34+ cases and also in those showing a higher rh123 elimination. In order to determine whether PE could condition clinical evolution, we analysed this parameter in a large series of patients but failed to demonstrate any relationship. By contrast, we observed that patients who displayed a higher API showed a shorter survival than patients with lower API (18% vs 48% surviving at 3 years). We have also shown that abnormalities in the CFU-GM growth pattern could be associated with risk the of relapse in AML patients; a switch from normal to abnormal "in vitro" growth should alert us. But for the assessment of the real value of these analyses sequential follow-up studies are mandatory. In summary, cell culture studies contribute not only to a better understanding of leukaemic hematopoiesis but may also contribute to better disease monitoring.     

Long-term survival in an elderly patient with acute myeloblastic leukemia

A 79-year-old patient with acute myeloblastic leukemia (M2 type in FAB), who has survived more than 5 years, is reported. She was admitted because of fever and anemia. Her white blood cell count was 6200/mm3 with 58% blasts. Bone marrow aspiration showed a nucleated cell count of 26 X 10(4)/mm with 84% blasts, Complete remission was achieved within one month by DCMP two-step method therapy. She relapsed in the third and fifth years after initial therapy. Because leukemic change is atypical, she was treated with a low dose of Ara-C therapy, resulting in complete remission. In cases of acute myelobastic leukemia in elderly patients, long-term survival is rare. However in this case, follow-up has succeeded for 5 years. This patient is the oldest case of acute myeloblastic leukemia ever reported in Japan.     

The expression of the proto-oncogene C-kit in the blast cells of acute myeloblastic leukemia

The oncogene kit has been shown genetically to map in the W locus of the mouse. This locus is known to have an important role in the regulation of normal hemopoietic stem cell growth. The blast cells of acute myeloblastic leukemia may be considered to arise in predeterministic stem cells. Accordingly, we sought evidence that kit was involved in the regulation of AML blast growth, using a cDNA probe to the external domain of c-kit. With this probe the gene was found to be in germline configuration in blast cells from AML, ALL, and continuous myeloblastic cell lines. However, expression could be detected by Northern analysis or RNA dot blots only in fresh AML blast cells. Fresh cells from ALL patients, normal bone marrow, PHA-stimulated lymphocytes, and four myeloblastic continuous cell lines were expression negative by the same techniques.     

Adherent cells in cultures of blast progenitors in acute myeloblastic leukemia

Blast cells from patients with acute myelogenous leukemia (AML) grow exponentially in suspension culture and form colonies in cultures "stiffened" with methylcellulose; under both culture conditions, cells are generated which have the ability to adhere to plastic or glass. These adherent cells lack the capacity to form colonies, to proliferate in liquid culture or to support growth. Adherent cells are generated in parallel with changes in the frequency of clonogenic cells and express surface markers of AML blasts but with a higher frequency of an antigen recognized by the monoclonal MO1, a late stage marker associated with the macrophage differentiation lineage. While the appearance of adherent cells provides further evidence that blast cells follow differentiation programs in culture, the generation of adherent cells does not indicate that normal differentiation is occurring; rather the data is consistent with the view that components of normal monocytic differentiation programs are assembled abnormally in the programs of some blast progenitors.     

Therapy of advanced acute myeloblastic leukemia with cytarabine and interleukin 2

A child with acute myelogenous leukemia who relapsed three months after an allogeneic bone marrow transplant received intermediate-dose cytarabine followed by interleukin 2 (IL-2). Complete remission was achieved after the first cycle of IL-2. Five more combined cycles of cytarabine and IL-2 were given over the next year, during which remission has persisted. IL-2 therapy affected serum tumor necrosis factor (TNF), interferon gamma (IFN gamma) and soluble IL-2 receptor (sIL-2r) levels. In vitro cytotoxicity against leukemia cell lines and recipient leukemia cells was also increased.     

The effects of leukemia inhibitory factor (LIF) on the blast stem cells of acute myeloblastic leukemia

Leukemia inhibitory factor (LIF) was tested using three established acute myelocytic leukemia (AML) cell lines. In growth assays in two of the three lines, we found that the addition of LIF increased the doubling time of the clonogenic population but not the total population as assessed by nucleated cell counts. Similarly, tritiated thymidine uptake into total AML populations was not affected by LIF, but the percentage of clonogenic cells killed by exposure to high specific activity 3HTdR was reduced in LIF-treated cultures compared to controls. We interpret these results to indicate that LIF prolongs the cell cycle of stem cells in some AML lines, possibly by increasing the time spent in the G2-M-G1 parts of the cycle. Consistent with this interpretation, we observed a decrease in ara-C sensitivity in LiF treated cultures. Variable results were obtained when freshly obtained AML blasts were exposed to LIF.     

Distinct lymphoblastic and myeloblastic populations in TdT positive acute myeloblastic leukemia: evidence by double-fluorescence staining

Double-immunofluorescent staining for the enzyme terminal deoxynucleotidyl transferase (TdT) as a marker of primitive lymphoblasts, and for the VIM-D5 antigen as a differentiation antigen of the myeloid system gave direct evidence for distinct lymphoblastic and myeloblastic populations (mixed leukemic cell populations) in seven patients with acute leukemia. The percentage of malignant TdT positive cells contributing to a leukemic cell bulk with unequivocal signs of myeloid origin was between 10 and 80%. A defect at the level of a common progenitor cell giving rise to both the TdT and the VIM-D5 positive blast cell population is discussed.