Erythroid differentiation in CGL cells from a patient with blast crisis

A 60-year-old patient with Ph1 + ve CGL presented with blast crisis. The leukaemic blast cells resembled erythroblasts and had 51 chromosomes with two Ph1. Cells obtained from peripheral blood, marrow and a pleural effusion were cultured under a variety of conditions. After 2-3 weeks in culture, the model 51-chromosome line persisted but many of the cells displayed erythroid morphology and differentiated to resemble mature normoblasts, strongly positive on o-tolidine +ve staining. Haemoglobin analysis by starch gel and globin synthesis studies demonstrated only fetal haemoglobin (HbF) synthesis in the cultured cells whilst the patient's reticulocytes synthesized very little HbF. Restriction enzyme mapping of DNA from the cultured cells showed that beta-globin genes were still present in these cells even though they were not expressed.