EXPRESSION OF AML1 MTG8 TRANSCRIPTS IN CLONOGENIC CELLS GROWN FROM BONE-MARROW OF PATIENTS IN REMISSION OF ACUTE MYELOID-LEUKEMIA WITH T(8-21)/

Patients in long-term remission of acute myeloid leukaemia (AML) M2 wi th t(8;21) after chemotherapy, with or without bone marrow transplanta tion, are known to retain residual cells which express AML1/MTG8 trans cripts in bone marrow, detectable by RT-PCR. In order to determine whe ther these residual cells are clonogenic, we have grown remission bone marrow samples in standard semi-solid culture and picked individual C FU-GM and BFU-E colonies which were then analysed for the expression o f AML1/MTG8 transcripts using a rapid specific RT-PCR technique. Nine patients were tested in remission, six between 1 and 83 months post ch emotherapy, one 103 months post autologous bone marrow transplant and one 41 months post allogeneic bone marrow transplant, One of these pat ients also had quantitation of AML1/MTG8 transcripts on five occasions after recovery from each course of chemotherapy and at the end of tre atment. There was a significant correlation between the percentage of positive colonies and the level of AML1/MTG8 transcripts. Between two and 80 CFU-GM and between two and 21 BFU-E colonies were analysed from each patient sample; 0-23% CFU-GM and 0-17% BFU-E colonies were found to express AML1/MTG8 transcripts suggesting that these residual cells are clonogenic in vitro and that the cell of origin is a multipotent myeloid progenitor.