Editorial: Terminal transferase and leukemia

Enzyme alterations in leukemic cells

Recently, much attention has been focused on various enzyme alterations found in leukemic cells. Most of the data generated thus far has involved the study of terminal deoxynucleotidyl transferase, the purine pathway enzymes, and hexosaminidase and other lysosomal enzymes. Differences in both total enzyme activities and isoenzyme patterns have been found to occur among the various leukemia types and subtypes. These changes may prove to be useful aids in diagnosing, classifying, detecting subclinical recurrent or residual disease, and as therapeutic determinants in hematopoietic neoplasia, especially in the lymphoid malignancies.

Induction of lymphocyte differentiation by epidermal cultures

Human and murine lymphoid cell populations were induced to express terminal deoxynucleotidyl transferase, a marker of early lymphoid differentiation, by exposure to allogeneic or syngeneic epidermal cells. Control growth medium, fibroblasts, or a mammary epithelial cell line did not induce this marker. These findings suggest that epidermal cells can induce lymphoid cell differentiation in vitro.

Glucocorticoid receptors and terminal deoxynucleotidyl transferase activities in leukemic cells

Glucocorticoid (GC) receptor and terminal deoxynucleotidyl transferase (TdT) activities were studied in leukemia cells to investigate their diagnostic and therapeutic implications. Among cell lines with T-cell character, higher GC-receptor and TdT activities were found in T-ALL (HPB-ALL and ALL-Ichikawa) than in cells from adult pleomorphic T-cell leukemia (HPB-MLT). HPB-Null with pre-B cell-character exhibited moderate GC receptor but low TdT activity; Raji cells and CCRF-SB, derived from B-cell Burkitt lymphoma and B-ALL, respectively, manifested low GC receptor and no TdT activity. The highest GC receptor activity was demonstrated in null-cell ALL, followed, in order, by juvenile T-ALL, adult pleomorphic T-cell leukemia, and AML. Other kinds of lymphoid and monocytic leukemias exhibited low GC receptor and no TdT activity. Although low GC receptor and negative TdT were demonstrated in cells from seven out of nine patients under CML blastic crisis, the last patient had cells with positive TdT and GC receptor activity.

Histopathology of bone marrow in human chronic leukemias

Among the patients with chronic myeloproliferative diseases including clinical symptoms of chronic myelogenous leukemia--CML--two varying compartments with substantially differing histology of hemopoiesis were found: one with predominating granulopoiesis for which the usual term of chronic granylocytic leukemia--CGL--seems inadequate. The other with proliferation of granylopoiesis and megakaryopoiesis as a neoplasia with a mixed cellularity is observed to be different in its clinical course: there are often a leukemic or subleukemic cell counts, but mostly considerable increased platelets in the peripheral blood; there is a prolonged period of latency, a higher age group, an infrequent occurrence of blastic crisis and a regular outcome into myelofibrosis. This entity of chronic megakaryocytic granulocytic myelosis--CMGM--can be seen very frequently among myeloproliferative diseases. Among a total of 718 core biopsies from the bone marrow the CMGM-patients are up to 29% compared with 21% of the typical one-cell-line disease CGL. The Ph1-chromosome may be presented in the CMGM-entity likewise.

The management of adult acute lymphoblastic leukaemia

The important advances made in recent years in the therapy of adult ALL have been reviewed. The definition of bad-prognosis patients has been improved and includes those with T-ALL, ABLL, and Ph1+ALL, in addition to those presenting with evidence of extensive disease. In contrast to childhood ALL, induction chemotherapy should include another drug (or drugs) in addition to VCR and prednisolone, and one of the anthracycline drugs (ADR or DNR) has been employed most frequently in this context. Such therapy should result in a CR rate of 70 to 75%. Similar to the experience in childhood ALL, the improvement in haematological response rate has led to an apparent increase in CNS leukaemia, and the need for adequate CNS prophylaxis is stressed. Despite these improvements, the outlook for adults with ALL is not yet as good as it is for childhood ALL. Controlled studies involving large numbers of patients are urgently needed to provide answers to a number of questions. In induction therapy, the use of higher drug dosage, the use of more and other drugs, and the use of an individual patient's risk factors to determine drug dosage, must be assessed. The benefits of consolidation therapy and the optimal duration and intensity of maintenance therapy have yet to be established. Methods of CNS prophylaxis other than cranial irradiation and IT MTX must be carefully studied. These important questions require that adult patients with ALL should be concentrated in centres capable of providing optimal overall care and, at the same time, able to conduct the necessary clinical trials.

Induction in vivo and in vitro of terminal deoxynucleotidyl transferase by thymosin in bone marrow cells from athymic mice

Terminal deoxynucleotidyl transferase (TdT) expression in bovine serum albumin (BSA) gradient-fractionated bone marrow cells was examined in NIH Swiss nu/nu and thymectomized C57BL/6 mice. In nude mice, TdT levels were approximately 10% of those of thymus-bearing littermates. In C57BL/6 mice, thymectomy caused a time-dependent loss of TdT activity in bone marrow cells. To determine whether or not not the apparent thymic requirement for TdT expression in bone marrow was mediated by thymic hormones, we examined the effects of thymosin fraction 5. Treatment of either NIH Swiss nu/nu or thymectomized C57BL/6 mice with thymosin fraction 5 restored the levels of TdT activity in BSA gradient-fractionated bone marrow cells to normal. Moreover, treatment of BSA gradient-fractionated bone marrow cells from NIH Swiss nu/nu or thymectomized C57BL/6 mice in tissue culture with thymosin fraction 5 induced TdT expression. In tissue culture, TdT induction was optimal with 25 ng/ml of thymosin fraction 5, it occurred within 6 h, and it was completely inhibited by actinomycin D. The effect was specific in that neither control nor spleen fraction 5-treated cells were induced to express TdT. These data demonstrate that TdT expression in bone marrow cells is under the direct control of thymic polypeptide hormones.

Lymphoid blastic crisis at the onset of chronic granulocytic leukemia: report of two cases

Two patients with a typical hematologic pattern of acute lymphatic leukemia were brought into complete remission by treatment. A few weeks later they developed a typical peripheral and bone marrow pattern of chronic granulocytic leukemia, with Philadelphia chromosome and very low leukocyte alkaline phosphatase. These cases, along with other findings recently reported in the literature, support the possibility of a previously unrecognized relationship between lymphoblastic cell populations and chronic granulocytic leukemia.

Analysis of human leukaemic cells using cell surface binding probes and the fluorescence activated cell sorter

Cell surface binding fluorescent ligands have been used to distinguish between different types of leukaemic cells and between leukaemic cells and their presumed normal counterparts or progenitors. Binding of these probes was evaluated using the Fluorescence Activated Cell Sorter (FACS) which provides both rapid, objective and quantitative recording of fluorescent signals from individual cells plus physical separation of cells of particular interest. Binding sites for cholera toxin (monosialoganglioside GM1) were found to be normally expressed in chronic leukaemias but greatly diminished or absent in acute leukaemias irrespective of their morphological type. Antibodies specific for the common form of acute lymphoblastic leukaemia (ALL, non-T, non-B) have been produced in rabbits. After extensive absorption and testing these were shown to define a cell surface antigen of non-T, non-B type ALLs. The antigen is absent from other leukaemias with two interesting exceptions--the majority of acute undifferentiated leukaemias express the antigen as do a proportion of chronic granulocytic leukaemias in blast crisis relapse. The anti-ALL antibodies can therefore be used to distinguish different leukaemias and, more significantly, can identify the existence of relatively rare leukaemic cells in the blood of untreated patients and the marrow of treated patients considered to be in remission.

Terminal deoxynucleotidyl transferase as a biological marker for human leukemia

High levels of terminal deoxynucleotidyl transferase have been observed in leukocytes of 7 out of 20 patients with chronic myelogenous leukemia in acute blast phase of the disease. These levels are comparable to the levels observed in human and calf thymus gland and cell lines with some T cell characteristics (Molt 4 and 8402). Negligible levels of this activity were observed in chronic myelogenous leukemia not in an acute blast phase of the disease, chronic lymphocytic leukemia, human B cells, mature T cells, and the mixed population of lymphocytes present in normal human blood. The detection of this enzyme in some patients with chronic myelogenous leukemia in acute blast phase of the disease suggests that the blast proliferation may involve primitive stem cells which have more lymphoid than myelogenous characteristics. This enzyme assay may be of use as a biological marker for following patients during treatment and in remission.