Membrane phenotype and response to deoxycoformycin in mature T cell malignancies

The adenosine deaminase inhibitor deoxycoformycin was used in low doses to treat 19 patients with clinically aggressive T cell malignancy with a mature membrane phenotype. The patients comprised eight with prolymphocytic leukaemia, two with chronic lymphocytic leukaemia, four with adult T cell leukaemia-lymphoma, three with Sézary syndrome, and two with T cell lymphoma. Two thirds of the patients had been resistant or minimally responsive to combination chemotherapy. Complete remission was obtained in five patients (two with prolymphocytic leukaemia and one each with chronic lymphocytic leukaemia, adult T cell leukaemia-lymphoma, and Sézary syndrome) and partial remission in two others. Unmaintained complete remission lasting more than one year was seen in three patients. Responses were obtained only in patients with CD4+,CD8-membrane markers (seven out of 10), and no responses were recorded in any of the nine patients with a different phenotype. In this series remission appeared to correlate with the membrane phenotype of the neoplastic cell and not with the cytopathological diagnosis. Future studies should establish the biochemical basis for the greater sensitivity of CD4+ lymphoid cells to deoxycoformycin.     

The Effect of Deoxyuridine, Vitamin B12, Folate and Alcohol on the Uptake of Thymidine and on the Deoxynucleoside Triphosphate Concentrations in Normal and Megaloblastic Cells

Deoxyuridine suppression of labelled thymidine uptake tests were performed in the bone marrows of 58 patients with megaloblastic anaemia (haemoglobin less than 10.0 g/dl) and invariably gave values (range 10.3-58.8%) above the range in 16 control marrows (range 1.0-9.0%). Folinic acid corrected the test equally well in either folate or vitamin B12 deficiency, even at concentrations as low as 60 ng/ml. Folic acid also corrected the test equally well in either deficiency but was only effective at concentrations down to 5 microgram/ml. Vitamin B12 (100 microgram/ml) only corrected the test in vitamin B12 deficiency and 5-methyltetrahydrofolate only corrected the test in folate deficiency at the concentrations tested between 60 and 1.2 microgram/ml. Among 16 patients with subnormal serum levels of both vitamin B12 and folate, vitamin B12 partially corrected the test in eight, including all five with pernicious anaemia, but had no effect in the other eight. Despite the clear-cut results of the dU suppression test, measurement of the deoxythymidine triphosphate (dTTP) concentration in normal and megaloblastic phytohaemagglutinin stimulated lymphocyte cultures or short-term bone marrow cultures gave no clear-cut differences between normal and megaloblastic cells after addition of deoxyuridine nor did the addition of vitamin B12, folic acid or folinic acid either alone or with deoxyuridine produce consistent changes in the dTTP concentration in lymphocytes or bone marrow cells in megaloblastic anaemia. Alcohol caused a rise in deoxyadenosine triphosphate concentration in normal PHA-stimulated lymphocytes which was concentration dependent but caused no consistent change in any of the other three deoxynucleoside triphosphate (dNTP) concentrations. Diphenylhydantoin (10(-3)M, 10(-4)M) had no consistent effect on any of the four dNTP concentrations.     

Increase in 2',5'-oligoadenylate synthetase caused by deoxycoformycin in hairy cell leukaemia.

2',5'-oligoadenylate synthetase (2-5OAS) has been studied in peripheral blood mononuclear cells from nine patients with hairy cell leukaemia (HCL) receiving therapy with the adenosine deaminase inhibitor deoxycoformycin (dCF) or alpha interferon (alpha-IFN). 2-5OAS mRNA was assayed by dot-blot hybridization. Increase of 2-5OAS mRNA level was seen in six patients with HCL treated with dCF and in one patient treated with alpha-IFN who responded to therapy. A patient with a variant form of HCL treated with dCF and the second patient treated with alpha-IFN did not show an increase of 2-5OAS mRNA and neither responded to therapy. The 15 other patients with T or B-chronic lymphoblastic leukaemia (CLL), T-acute lymphoblastic leukaemia (ALL), adult T-cell leukaemia lymphoma (ATLL), non-Hodgkins lymphoma (NHL), Sezary and T or B-prolymphocytic leukaemia (PLL) treated with dCF did not show an increase in 2-5OAS, though four patients, all with T-cell tumours, responded clinically. 2-5OAS activity is known to be stimulated by alpha-IFN and recent work suggests that this rise in 2-5OAS may result in increased cleavage of mRNA for tumour necrosis factor (TNF) and other cytokines on which autocrine growth and proliferation of the tumour cells are dependent. By analogy, we suggest that one mechanism of action of dCF in hairy cell leukaemia may be to break down an autocrine growth loop for TNF or other cytokines. An alternative explanation for these observations is that cytokines released from hairy cells in the bone marrow killed by dCF induce a rise in 2-5OAS in circulating leucocytes.     

The effect of external deoxyribonucleosides on deoxyribonucleoside triphosphate concentrations in human lymphocytes.

The effects of deoxyribonucleosides on the intracellular levels of deoxyribonucleoside triphosphates (dNTP) and on the rate of labelled thymidine incorporated into DNA of human phytohaemag-glutinin-stimulated lymphocytes have been studied. Thymidine (10^?2–10^?6M) expanded the dTTP and reduced dATP and dCTP levels. Deoxycytidine (10^?3M) expanded the dCTP level and caused inhibition of [³H] thymidine incorporation into DNA but had no detectable effect on the other dNTP concentrations. Deoxyadenosine (10^?3 M) expanded the dATP level, and reduced the other dNTP levels and deoxyguanosine (10^?4M) expanded the dGTP level and reduced the dCTP level; both inhibited [³H] thymidine incorporation into DNA. The sensitivity of these cells to the addition of deoxynucleosides to their culture medium indicates that the plasma and tissue levels of nucleosides may profoundly influence DNA synthesis by human cells in vivo.     

CCK2 gastrin receptor as a potential target for therapy in leukaemia cell lines

The gastrin CCK2 pathway has been implicated in the development of various cancers including leukaemia. An autocrine or intracrine pathway may exist in the leukaemia cell that is involved in stimulating proliferation. We tested four leukaemia cell lines, KU812, ML-1, MOLT-4 and U937 for the existence of the CCK2 receptor and gastrin precursor protein using immunoblotting. We also assessed the effect of CCK2 antagonist PD 135 and both gastrin 17 and glycine-extended gastrin on the proliferation of the cell lines. We found immunoreactive CCK2 and gastrin precursors present in all 4 cell lines. We also observed a stimulatory effect on proliferation by gastrin and glycine-extended gastrin on 2 and 3 of the cell lines respectively and an inhibitory effect of PD 135 on all 4 cell lines. These results demonstrate that the gastrin-gastrin receptor axis is a potential target for new therapeutic strategies.     

First intron and M-bcr breakpoints are restricted to the lymphoid lineage in Philadelphia positive acute lymphoblastic leukemia

Knowledge of the level of commitment of the target cell in hematological malignancies may have important therapeutic and prognostic implications. Cell lineage involvement was investigated in two cases presenting with acute lymphoblastic leukemia diagnosed on clinical and immunological findings and having the Philadelphia translocation t(9;22)(q34;q11). DNA from cells separated into mononuclear (lymphoid) and granulocytic fractions was hybridized with Philadelphia breakpoint-specific probes. This revealed that the breakpoint giving rise to the Philadelphia chromosome in case 1 was within the major breakpoint cluster region and in case 2 was in the first intron of the BCR gene. Rearrangement was found in the lymphoid but not the granulocyte fraction in each case. It is therefore concluded that the target cell for chromosomal change in these cases was a lymphoid committed progenitor cell, irrespective of breakpoint location.     

Deoxyribonucleoside Triphosphates in Human Cells: Changes in Disease and Following Exposure to Drugs

Abstract. Deoxyribonucleic acid synthesis requires adequate cellular concentrations of the four deoxyribonucleoside triphosphates. Using a sensitive enzymic assay, we have measured the concentrations (pools) of these compounds in human bone marrow cells and in lymphocytes. The mean concentrations (pmol/10⁶ cells) in normal human bone marrow cells were: deoxyadenosine triphosphate (dATP) 1. 5; deoxyguanosine triphosphate (dGTP) 0.4; thymidine triphosphate (dTTP) 1. 4 and deoxycytidine triphosphate (dCTP) 0.6; and in normal phytohaemagglutinin (PHA)-stimulated lymphocytes (72 h cultures); dATP 3. 7; dGTP 1. 9; dTTP 9. 4 and dCTP 2. 9. The deoxyribonucleoside triphosphate concentrations were increased approximately threefold in the nucleated marrow cells from patients with leukaemia and myeloproliferative diseases. PHA-stimulation of lymphocytes caused a marked increase of the deoxyribonucleoside triphosphate concentrations, particularly of dTTP, between 24 and 48 h of culture. In PHA-stimulated lymphocytes, the antifolate drugs methotrexate, pyrimethamine and trimethoprim, all produced a fall in dTTP and a rise in dATP concentrations within 1 h. These effects could be reversed by folinic acid. 5-Fluorouracil caused a fall in dTTP and in dCTP but no consistent changes in dATP; hydroxyurea caused a fall in dATP with a rise in dTTP. BCNU caused a significant fall in dATP and dCTP. Dibutyryl cyclic 3', 5' adenosine monophosphate and theophylline had no consistent effect on the deoxyribonucleoside triphosphate concentrations. 6-Mercaptopurine caused a fall in dATP and dGTP, the fall in dATP being marked after 4 h incubation.
It is concluded that measurement of the deoxyribonucleoside triphosphates in human cells provides a new method of studying DNA synthesis in human disease states and of analysing the action of antimetabolite drugs on normal and diseased cells.     

Enzymes of purine metabolism in lymphoid neoplasms,clinical relevance for treatment with enzyme inhibitors

Summary A few enzymes of the purine degradative pathway have proved valuable in diagnosis and treatment of lymphomas and lymphocytic leukemia. Of particular interest are the enzymes adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and ecto-5-nucleotidase (5NT). Intact activities of ADA and PNP have been shown to be vital for lymphoid cells. During development, lymphoid precursors go through remarkable changes in the concentrations of these enzymes and the neoplasma derived from them show a frozen biochemical profile similar to the corresponding normal cell of origin. Knowledge of the role of these enzymes has led to the pharmacological use of enzyme inhibitors for the specific treatment of lymphoid neoplasms. This review concerns the enzymatic make-up of normal and neoplastic lymphocytes and exploitation of this knowledge for the treatment of lymphomas. Special emphasis will be put on the clinical use of an ADA-inhibitor, deoxycoformycin.Abbreviations ADA Adenosine deaminase - ALL Acutelymphocytic leukemia - CdA 2-Chloradeoxyadenosine - CLL Chronic lymphocytic leukemia - dATP Deoxyadenosine triphosphate - dCTP Deoxycytidine triphosphate - dGTP Deoxyguanosine triphosphate - 5NT Ecto-5-nucleotidase - PNP Purine nucleoside phosphorylase - SAH S-adenosylhomocysteine - SAM S-adenosyl-methionine - SCID Severe combined immunodeficiency disease Dedicated to Professor Werner Hunstein on the occasion of his 60th birthday     

Biochemical mechanisms of deoxycoformycin toxicity in chronic leukemias

The in-vitro effects of deoxycoformycin (dCF) on dATP, NAD, ATP and DNA strand breaks have been evaluated in the cells from 42 patients with various types of chronic lymphoid leukemia. These included 18 with B-cell chronic lymphoid leukemias of different types (BCL); 10 with hairy cell leukemia (HCL) and 14 with T-cell chronic lymphoid leukemias of different types (TCL). The dATP concentrations in HCL, BCL and TCL increased from means of 2.9, 1.8 and 3.0 to 100.3, 68.2 and 51.3 pmol/10(6) cells respectively after 2 h with 10(-5) M dCF and 10(-4)M deoxyadenosine. After 18-24 h, the NAD levels and total double-stranded DNA decreased to 37 and 12.5% (HCL) to 36 and 21.6% (BCL) and 40 and 20.5% (TCL) of control values respectively. Similar decreases were observed in ATP levels. The results do not suggest that these measurements in vitro would predict which patients with these disorders will respond to dCF therapy. Although HCL responds particularly well to dCF in vivo, no difference in the in-vitro effects of dCF studied here could be detected between cases of HCL and the other types of chronic leukemia.