Biomaterial Database

Polymorphic thiopurine methyltransferase in erythrocytes is indicative of activity in leukemic blasts from children with acute lymphoblastic leukemia. 1995

H L McLeod, and M V Relling, and Q Liu, and C H Pui, and W E Evans

Pharmaceutical Department, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.

The activity of thiopurine methyltransferase (TPMT) exhibits genetic polymorphism, with approximately 1 in 300 individuals inheriting TPMT deficiency as an autosomal recessive trait, and about 11% having intermediate activity (ie, heterozygotes). Patients with TPMT deficiency accumulate excessive concentrations of 6-thioguanine nucleotides (TGNs) and develop severe toxicity when treated with standard dosages of mercaptopurine. High TPMT activity has been associated with lower concentrations of TGNs, yielding a higher risk of treatment failure in children with acute lymphoblastic leukemia (ALL). As the biochemical basis of these pharmacodynamic relationships has not been fully elucidated, we investigated the variability and relationship of TPMT activity in erythrocytes and lymphoblasts from children with ALL. A 58-fold range of erythrocyte TPMT activity was found among 119 patients receiving ALL chemotherapy (0.6 to 34.9 U/mL packed erythrocytes), but relatively low intrapatient variability (coefficient of variation, 13.5%) was observed over 1 year. A 27-fold range in TPMT activity was observed in leukemic blasts obtained from 42 patients at initial diagnosis (3.3 to 88.9 U/1 x 10(9) cells). TPMT activity in leukemic blasts at diagnosis was significantly correlated with TPMT in erythrocytes before therapy (rs = .75, P < .0001, N = 13). These data document extensive interpatient variability of TPMT activity in ALL blasts and establish its linkage to polymorphic TPMT activity in erythrocytes, providing a new mechanism by which erythrocytes serve as prognostic markers of mercaptopurine metabolism and TPMT activity in children with ALL.

UI	MeSH Term	Description	Entries
D008214	Lymphocytes	White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.	Lymphoid Cells,Cell, Lymphoid,Cells, Lymphoid,Lymphocyte,Lymphoid Cell
D008297	Male		Males
D008727	Methotrexate	An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.	Amethopterin,Methotrexate Hydrate,Methotrexate Sodium,Methotrexate, (D)-Isomer,Methotrexate, (DL)-Isomer,Methotrexate, Dicesium Salt,Methotrexate, Disodium Salt,Methotrexate, Sodium Salt,Mexate,Dicesium Salt Methotrexate,Hydrate, Methotrexate,Sodium, Methotrexate
D008780	Methyltransferases	A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1.	Methyltransferase
D009363	Neoplasm Proteins	Proteins whose abnormal expression (gain or loss) are associated with the development, growth, or progression of NEOPLASMS. Some neoplasm proteins are tumor antigens (ANTIGENS, NEOPLASM), i.e. they induce an immune reaction to their tumor. Many neoplasm proteins have been characterized and are used as tumor markers (BIOMARKERS, TUMOR) when they are detectable in cells and body fluids as monitors for the presence or growth of tumors. Abnormal expression of ONCOGENE PROTEINS is involved in neoplastic transformation, whereas the loss of expression of TUMOR SUPPRESSOR PROTEINS is involved with the loss of growth control and progression of the neoplasm.	Proteins, Neoplasm
D011110	Polymorphism, Genetic	The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.	Gene Polymorphism,Genetic Polymorphism,Polymorphism (Genetics),Genetic Polymorphisms,Gene Polymorphisms,Polymorphism, Gene,Polymorphisms (Genetics),Polymorphisms, Gene,Polymorphisms, Genetic
D011379	Prognosis	A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.	Prognostic Factor,Prognostic Factors,Factor, Prognostic,Factors, Prognostic,Prognoses
D012074	Remission Induction	Therapeutic act or process that initiates a response to a complete or partial remission level.	Induction of Remission,Induction, Remission,Inductions, Remission,Remission Inductions
D001853	Bone Marrow	The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.	Marrow,Red Marrow,Yellow Marrow,Marrow, Bone,Marrow, Red,Marrow, Yellow
D002648	Child	A person 6 to 12 years of age. An individual 2 to 5 years old is CHILD, PRESCHOOL.	Children