Megakaryocyte colony formation in chronic myeloid leukemia and myelofibrosis

Colony formation by megakaryocytic progenitors from the blood or bone marrow was studied in 22 patients with chronic myeloid leukemia (CML) and in 17 patients with idiopathic myelofibrosis (MF). Thirteen of the 22 CML patients showed megakaryocytic colony formation, when PHA-LCM and plasma of a patient with aplastic anemia were used as a source of colony stimulating activity. Twelve of these 13 patients also showed spontaneous megakaryocytic growth, i.e. colony formation when PHA-LCM was omitted and normal plasma was used instead of aplastic plasma. All the untreated CML patients exhibited both stimulated and spontaneous growth. Each patient without any megakaryocytic colony formation had recently received cytotoxic treatment. Thirteen of the 17 patients with MF grew megakaryocytic colonies and ten of these 13 patients also showed spontaneous megakaryocytic growth. The colony numbers were roughly similar in the stimulated and non-stimulated cultures. The present study shows that spontaneous megakaryocytic colony formation, previously shown to be common in PV and ET, is also seen in many patients with CML and MF.