inosinic-acid and Precursor-Cell-Lymphoblastic-Leukemia-Lymphoma

Methotrexate is widely administered with mercaptopurine, a prodrug requiring activation into thioguanine nucleotides (TGN) to exert antileukemic effects. In vitro, methotrexate enhances TGN formation, but in vivo, such enhancement has yet to be demonstrated. We investigated whether TGN concentrations were related to methotrexate concentrations in children with acute lymphoblastic leukemia who received a weekly intravenous methotrexate (40 mg/m(2)) dose combined with daily mercaptopurine (75 mg/m(2)). A total of 141 erythrocyte TGN concentrations were measured with erythrocyte methotrexate polyglutamates (MTX-PG) concentrations in 87 patients. Average TGN concentrations ranged from 137 to 958 pmol/8 x 10(8) cells (median 389), average total MTX-PG concentrations (MTX- PG(1-7)) from 0.60 to 97.7 pmol/10(9)cells (median 29), and average long chain polyglutamate concentrations (MTX-PG(5-7)) from 0 to 8.35 pmol/10(9) cells (median 2.43). Higher TGN concentrations correlated with higher MTX-PG(5-7) concentrations (P = 0.002). These data support the practice of administering methotrexate with mercaptopurine during continuation therapy of acute lymphoblastic leukemia.

Topics: Algorithms; Antimetabolites, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Biotransformation; Child; Drug Administration Schedule; Erythrocytes; Humans; Hypoxanthine Phosphoribosyltransferase; Inactivation, Metabolic; Injections, Intravenous; Inosine Monophosphate; Mercaptopurine; Methotrexate; Methyltransferases; Neoplasm Proteins; Nucleotides; Polyglutamic Acid; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Prodrugs; Thioguanine; Thionucleotides; Xanthine Oxidase

Topics: Biotransformation; Carbon Radioisotopes; Cell Division; Cell Line; Cell Survival; Humans; IMP Dehydrogenase; Inosine Monophosphate; Leukemia-Lymphoma, Adult T-Cell; Mercaptopurine; Mycophenolic Acid; Precursor Cell Lymphoblastic Leukemia-Lymphoma

Adenylic acid (AMP) deaminase is a "catabolic enzyme" involved in nucleotide degradation, transforming AMP into inosinic acid (IMP). We present a simple method for the determination of the enzyme activity, which combines high sensitivity with requirement of low quantities of lymphocytes. Human lymphocytes were isolated with a Lymphocyte Separation Medium from FLOW and sonicated. After centrifugation at 2,000 rpm x 10 min and treatment with Norit A, the cells were incubated at 37 degrees C with ATP 0.8 mM and 14C-AMP 0.1 mM (specific activity 12 microCi/mumole) in potassium phosphate 100 mM (pH 7.4). 14C-IMP and 14C-AMP were separated through HPLC by an isocratic elution, with 20 mM KH2PO4 (pH 5.5) at a 1.5 ml/min flow rate. Identification of the nucleotides was carried out through retention time, coelution with internal standards: their evaluation by determining the radioactivity of the collected peaks. The enzyme activity is decreased in patients affected by CLL: the decrease is evident only when data are referred to the single cells and not when they are referred to the protein.

Topics: AMP Deaminase; Humans; Inosine Monophosphate; Inosine Nucleotides; Lymphocytes; Nucleotide Deaminases; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Purines