STI571 also appeared to specifically target bcr–abl expressing cells, as results from colony forming assays using the surviving cell fraction from STI571-treated peripheral CD34+ chronic myeloid leukaemia blast cells, indicated a reduction in the expansion of colonies of myeloid lineage, but no effect on normal colony formation. The gene discussed is CD34; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.