Simultaneous establishment of myeloid and B-lymphoid cell lines with identical chromosome abnormalities from Philadelphia chromosome-positive chronic myelogenous leukaemia.

Two continuously growing cell lines, designated YOS-M and YOS-B, were established simultaneously from a patient with Philadelphia (Ph1) chromosome-positive chronic myelogenous leukaemia (CML) in myeloid blast crisis. Both YOS-M and YOS-B had the Ph1 chromosome and identical additional chromosome abnormalities, which were not detected in the chronic phase. Cytochemical analysis showed that YOS-M was significantly positive for peroxidase, whereas YOS-B was entirely negative. YOS-M expressed myeloid-associated antigens (CD14, CD33) as well as CD4, CD25 and CD34. The surface phenotype of YOS-M was identical to that of the leukaemic blasts found in the patient. On the other hand, YOS-B expressed mature B-cell markers, CD19, CD20, CD21 and surface immunoglobulin, but not myeloid-associated antigens. These two cell lines showed an identical rearrangement pattern of the break point cluster region on chromosome 22, but rearrangement of the immunoglobulin heavy chain gene was detected only in YOS-B. These findings provide definite evidence that CML cells still have the capability to differentiate and mature along different haematopoietic cell lineages even after blast crisis.