Adenosine deaminase and purine nucleoside phosphorylase levels in acute myeloblastic leukemia cells. Relationship to diagnosis and clinical course

The Emerging Role of Cytidine Deaminase in Human Diseases: A New Opportunity for Therapy?

The recycling activity of cytidine deaminase (CDA) within the pyrimidine salvage pathway is essential to DNA and RNA synthesis. As such, CDA deficiency can lead to replicative stress, notably in Bloom syndrome. Alternatively, CDA also can deaminate cytidine and deoxycytidine analog-based therapies, such as gemcitabine. Thus, CDA overexpression is often associated with lower systemic, chemotherapy-related, adverse effects but also with resistance to treatment. Considering the increasing interest of CDA in cancer chemoresistance, the aims of this review are to describe CDA structure, regulation of expression, and activity, and to report the therapeutic strategies based on CDA expression that recently emerged for tumor treatment.

Purine metabolizing enzymes in lymphocytes from patients with solid tumors

The activities of five clinically important enzymes of purine metabolism have been determined in lymphocytes from 62 patients with various types of solid tumors. The activity of purine nucleoside phosphorylase was increased in all patient groups studied, i.e. small cell bronchogenic carcinoma (n = 30), carcinoma of the breast (n = 17) and other tumors (n = 15), compared to cells form normal donors. Activities of adenosine deaminase, adenine phosphoribosyltransferase (APRT), hypoxanthine (guanine) phosphoribosyltransferase (HGPRT), and 5'-nucleotidase (5'-NUC) vary little from control values, except for lower levels of APRT in lymphocytes from patients with carcinoma of the breast. In patients with small cell bronchogenic carcinoma, enzyme levels were also determined in granulocytes, where increased APRT activity was found. Following cytostatic treatment of these patients, significant decreases were seen in lymphocytic HGPRT and 5'-NUC activities.

Adenosine deaminase in body fluids: a useful diagnostic tool in tuberculosis

The performance of a colorimetric ADA determination in body fluids other than serum in the diagnosis of tuberculosis was assessed in 1063 patients from whom pleural (600), peritoneal (136), pericardial (77), or cerebrospinal (250) fluids were obtained. In exudative pleuroperitoneal and pericardial effusions, an ADA decision level of 0.71 mu kat/L displayed a sensitivity of 1.00, and was higher than those of histologic (0.83) and bacteriologic (0.62) studies. At this level, ADA reached a specificity of 0.92 and efficiency of 0.94. In cerebrospinal fluid, an ADA catalytic concentration above 0.15 mu kat/L strongly suggests tuberculous meningitis in patients older than 7 years (sensitivity 1.00, specificity 0.99 and efficiency 0.99). ADA results obtained with a UV-method were closely correlated with those of the colorimetric method in pleuroperitoneal effusions (r = 0.989) and in cerebrospinal fluids (r = 0.905). Sample blanks should be processed, otherwise false positive results may be found in non-tuberculous cerebrospinal fluids (5.3%) and pleuroperitoneal effusions (3.8%).

Adenosine deaminase (ADA) in leukemia: clinical value of plasma ADA activity and characterization of leukemic cell ADA

Adenosine deaminase (ADA) activity was measured in plasma, erythrocytes, and mononuclear cells from 18 patients with acute and chronic leukemia. High levels of ADA activities were found in plasma, erythrocytes, and mononuclear cells from patients with acute leukemia, especially acute lymphoblastic leukemia, and blastic crisis of chronic myeloid leukemia. Serial determination of plasma ADA activities was done in 9 patients with acute leukemia. All patients untreated or in relapse had an elevation of plasma ADA activity, which decreased to normal or subnormal levels during complete remission. On starch gel electrophoresis, plasma ADA in leukemic patients separated into two bands. The major band showed a mobility identical to that of normal red cells and mononuclear cells, and the minor band corresponded to that of normal plasma ADA. Enzymatic and immunological studies were performed on ADA from leukemic cells of acute myeloid and lymphoblastic leukemia. There were no differences in Michaelis constant for adenosine, thermostability, electrophoretic mobility, immunological reactivity, and specific activity between ADA of leukemic cells and normal mononuclear cells. These results strongly suggest that the increased ADA activity in leukemic cells is caused by an increased synthesis of a structurally normal enzyme and that increased plasma ADA activity in leukemic patients reflects an increment of leukemic cells in bone marrow. Therefore, serial determination of plasma ADA activities seems to provide a good indicator of the total mass of leukemic cells in bone marrow.

Biochemical enzyme analysis in acute leukaemia

This report summarises the current knowledge regarding the clinical utility of biochemical enzyme markers for both diagnostic and therapeutic purposes in acute leukaemia. The enzymes studied most extensively in this field are terminal deoxynucleotidyl transferase, adenosine deaminase, 5'-nucleotidase, purine nucleoside phosphorylase, and acid phosphatase, esterase, hexosaminidase isoenzymes. For each enzyme, the quantitative and qualitative characteristics in various immunologically defined subclasses of acute leukaemia are described. The quantitative evaluation of enzyme activities represents an adjunctive classification technique which should be incorporated into the multivariate analysis, the "multiple marker analysis." By qualitative characterisation pronounced heterogeneity of leukaemia subsets is uncovered. The application of 2'-deoxycoformycin, a specific inhibitor of adenosine deaminase, and the potential usefulness of two other enzymes as targets for treatment with selective agents is discussed. The concept that gene products expressed at certain developmental stages of normal cells can similarly be detected in leukaemic cells (which therefore seem to be "frozen" or "arrested" at this particular maturation/differentiation stage) is supported by the results obtained in enzyme studies. Besides their practical clinical importance for classification and treatment of acute leukaemias, biochemical enzyme markers constitute a valuable research tool to disclose biological properties of leukaemic cells.

Hexosaminidase isoenzyme profiles in leukemic cells

The isoenzyme profiles of hexosaminidase in leukemic cells from 39 patients were examined with DEAE-Sephadex chromatography. There was a clear difference in the isoenzyme composition between normal lymphocytes and granulocytes. In acute non-T/non-B lymphocytic leukemia (ALL) a characteristic alteration was found in the intermediate forms of hexosaminidase (Hex I), which was significantly higher than those of normal lymphocytes (p less than 0.001). Subtypes of Hex I (Hex i1-i4) and the heterogeneity of their abnormal expression in ALL was demonstrated. There was no type-specific alteration of the isoenzyme profiles in T-cell leukemia. Leukemic cells of acute myelocytic leukemia (AML) had significantly higher Hex P component than granulocytes (p less than 0.01) and ALL cells (p less than 0.01). The increase of Hex P was evident in childhood AML. There was a significant difference in Hex P level between childhood AML and adult myelo(mono)genous leukemia (p less than 0.001). Chronic myelo(mono)genous leukemia showed similar isoenzyme compositions to normal granulocytes. The isoenzyme profiles in acute undifferentiated leukemia differed from those in other types of leukemia. Isoenzyme analysis might be useful for probing the nature and the intrinsic biochemical abnormality of leukemic cells.

Effects of adenosine and deoxyadenosine on PHA-stimulation of lymphocytes of man, horse and pig

1. Adenosine inhibits thymidine and uridine incorporation of PHA-stimulated lymphocytes of man and horse at concentrations higher than 50 and 10 microM, respectively. Deoxyadenosine is inhibitory at concentrations higher than 100 microM. Thymidine and uridine incorporation of porcine lymphocytes are elevated 5-7-fold by 25-100 microM adenosine, deoxyadenosine, inosine and hypoxanthine. Leucine incorporation of PHA-stimulated lymphocytes was affected by adenosine and deoxyadenosine in the same way, but to a lower extent. 2. Effects of adenosine and deoxyadenosine were more pronounced at shorter cultivation times. 3. EHNA potentiated the effects of adenosine and deoxyadenosine on human and equine lymphocytes. With human lymphocytes inhibition by deoxyadenosine and EHNA was higher than by adenosine and EHNA. With porcine lymphocytes only the combination of deoxyadenosine and EHNA was inhibitory. 4. Homocysteine potentiated the inhibition of thymidine incorporation by the combination of adenosine and deoxyadenosine with equine lymphocytes, but not the inhibition of adenosine or deoxyadenosine alone. 5. Adenosine suppressed the PHA-stimulated elevation of PRPP concentrations. With porcine lymphocytes PRPP remained at the level of 0 hr, while with equine lymphocytes PRPP concentration decreased to below that level. 6. The various effects of adenosine and deoxyadenosine on lymphocytes of man, horse and pig can partially be related to differences in adenosine and deoxyadenosine metabolism.

The use of enzyme marker analysis for subclassification of acute lymphocytic leukemia in childhood

Subclassification of acute lymphocytic leukemias in childhood by multiple marker analysis has proven the heterogeneity of this disease and this methodology has led to a better understanding of the cell-biological basis of ALL. Enzyme markers have become important tools in multiple marker analysis. This is especially true for TdT, purine metabolic enzymes, hexosaminidase I, acid phosphatase and carboxylic esterases. In spite of sophisticated methods and encouraging results multiple marker analysis has not been totally satisfactory in defining patients at risk. The same is true for a risk score established by clinical data. More efforts in the future are necessary for combining multiple marker analysis, cytogenetics, proliferation characteristics, basic clinical findings and the final outcome of the disease in these patients. Beyond that this kind of leukemia research will help to clarify the pathobiological basis of human leukemia and to develop new specific therapeutic modalities.

DNA synthesis in thymic-acute lymphoblastic leukaemia

Deoxyribonucleoside triphosphate (dNTP) concentrations were measured in bone marrow and peripheral blood leucocytes from seven patients with acute Thy-lymphoblastic leukaemia (Thy-ALL), 12 patients with acute myeloblastic leukaemia and 15 patients with acute non-T, non-B lymphoblastic leukaemia (c-ALL), and in thymocytes from patients with myasthenia gravis. Labelled thymidine and deoxycytidine incorporation into DNA was also studied. In Thy-ALL, dNTP concentrations were markedly increased compared with those in the other acute leukaemias. The dNTP concentrations in thymocytes were, however, similar to those in Thy-ALL. 3H-nucleoside incorporation studies showed a marked difference in labelled deoxycytidine incorporation and particularly in the deoxycytidine/thymidine DNA labelling ratio between Thy-ALL and the other cell types. We conclude that the pathways of DNA synthesis in Thy-ALL blasts are different from those in the cells from acute acute leukaemias and some but not all these differences may correspond to differences between normal cortical thymocytes and bone marrow cells.

Adenosine deaminase and purine nucleoside phosphorylase activities in peripheral lymphocytes from patients with solid tumours

Adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) levels of peripheral blood mononuclear cells were measured in 34 patients with various types of solid tumours. The mean ADA activity was found to be significantly lower than in controls (P less than 0.005). Patients with nonresectable tumour or with recurrence after radical surgery showed low ADA levels, while patients operated upon and without recurrence had enzymatic activity not different from that of normal controls. The mean value of PNP activity was similar to that of normal controls; no differences were observed between operated patients without recurrence and cases with nonresectable tumour or with recurrence after surgical treatment. No effects on ADA and PNP levels appeared to be induced by chemotherapy.