CHARACTERIZATION OF A MYELOPEROXIDASE MRNA(-LEUKEMIA CELL-LINE (EU-1() ACUTE LYMPHOBLASTIC)ALL) ESTABLISHED FROM A CHILD WITH AN APPARENT CASE OF ALL/

A myeloid-antigen-positive acute lymphoblastic leukemia (My+ ALL) cell line (EU-1) was established from the bone marrow cells of a child wit h apparent ALL. By morphology, cytochemistry and fluorescent-antibody phenotyping, EU-1 cells appeared to be lymphoblastic (L1 morphology, T dT+, CD10+, CD19+). However, by a sensitive immunocytochemial assay, E U-1 cells additionally displayed several myeloid antigens (CD13, CD14, CD33) not detected by flow-cytometry. Furthermore, EU-1 cells were cy tochemically and immunocytochemically negative for myeloperoxidase (MP O) but positive for MPO mRNA by Northern blot analysis. After incubati on with dimethylsulfoxide (DMSO), myeloid cell surface antigens were d etected on EU-1 cells by flow cytometry, and a marked decrease in MPO mRNA expression was observed. These results demonstrate that EU-1 is a unique ALL cell line representing a significant subset of pediatric A LL patients who also express myeloid antigens and have poor prognosis.