Co-expression of c-abl and c-myb oncogenes in Philadelphia chromosome-negative, bcr-negative chronic myeloid leukaemia.

Three cases of Philadelphia (Ph) chromosome-negative, bcr-negative chronic myeloid leukaemia (CML) have been investigated for oncogene expression by Northern blot and cytoplasmic RNA dot blot hybridization. Considerably high levels of expression of c-abl and c-myb were observed in all cases. In the Ph-negative cells the normal 6.0 and 7.0 kb c-abl and 3.8 kb c-myb transcripts were found. No amplification of c-abl or c-myb oncogenes was detected in the DNAs of Ph-negative CML cells. Data suggest that co-operation between the overexpressed c-abl and c-myb oncogenes is causally related to Ph-negative bcr-negative CML.