USE OF MYELOPEROXIDASE MESSENGER-RNA AS A MARKER FOR MYELOID LINEAGE IN ACUTE LEUKEMIAS

Background.-Positivity for myeloperoxidase is considered the diagnosti c hallmark of myeloid lineage and is the major criterion in the classi fication of acute leukemias. Early myeloid precursors, however, may be cytochemically negative for myeloperoxidase enzymatic activity or pro tein, but positive for myeloperoxidase mRNA. Objective.-To evaluate th e expression of the myeloperoxidase gene in leukemic blasts at the mRN A level and correlate the expression with blast cytochemistry and immu nophenotyping. Patients and Methods.-Sixteen cases of acute myelogenou s leukemia and six cases of acute lymphoblastic leukemia were studied retrospectively using cellular material from Wright-stained and unstai ned archival smears of peripheral blood and bone marrow aspirate and a reverse-transcription polymerase chain reaction procedure for detecti on of myeloperoxidase mRNA. Results.-Positivity in leukemic blasts was found in all acute myelogenous leukemia cases, including cases of M0, M1, and M5 that were cytochemically negative, equivocal, or weakly po sitive for the enzyme. None of the acute lymphoblastic leukemia cases showed positivity for myeloperoxidase mRNA. Conclusions.-The procedure is a highly specific and sensitive method for diagnosis of myeloid li neage in leukemic blasts.