Persistence of bcr-abl mRNA-expressing cells in long-term cultures established from chronic myeloid leukemic bone marrow or blood.

Long-term cultures (LTC) established from chronic myeloid leukemic (CML) bone marrow or blood contain bcr-abl mRNA-expressing cells, as demonstrated by the polymerase chain reaction (PCR). Bcr-abl sequences were detectable in cultures from all of nine patients investigated. In LTC from two patients, in which a cytogenetic conversion from Ph+ to Ph- was noted at day 20 and 40, respectively, the PCR for bcr-abl remained 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 derived from spontaneously EBV-transformed bcr-abl mRNA-negative B cells, which may become the dominating cell type very early in LTC from bone marrow or blood. LTCs cloned for EBV-transformed B cells which no longer harbor admixed macrophages are bcr-abl mRNA negative. In conclusion, bcr-abl mRNA-expressing cells may show long-term persistence in LTC established from CML bone marrow or blood.