PERSISTENCE OF BCR-ABL MESSENGER-RNA-EXPRESSING CELLS IN LONG-TERM CULTURES ESTABLISHED FROM CHRONIC MYELOID LEUKEMIC BONE-MARROW OR BLOOD

Long-term cultures (LTC) established from chronic myeloid leukemic (CM L) bone marrow or blood contain bcr-abl mRNA-expressing cells, as demo nstrated by the polymerase chain reaction (PCR). Bcr-abl sequences wer e detectable in cultures from all of nine patients investigated. In LT C from two patients, in which a cytogenetic conversion from Ph(+) to P h(-) was noted at day 20 and 40, respectively, the PCR for bcr-abl rem ained positive, at least up to day 112 and 245, respectively, in vitro . The differences between the results of cytogenetic and PCR analyses was explained by the fact that the metaphases studied were obviously d erived from spontaneously EBV-transformed bcr-abl mRNA-negative B cell s, which may become the dominating cell type very early in LTC from bo ne marrow or blood. LTCs cloned for EBV-transformed B cells which no l onger harbor admired macrophages are bcr-abl mRNA negative. In conclus ion, bcr-abl mRNA-expressing cells may show long-term persistence in L TC established from CML bone marrow or blood.