Erythropoietin-independent erythroid colony formation in patients with erythroleukaemia (M6) and related disorders.

In vitro erythropoietin (Ep) responsiveness of human bone marrow mononuclear cells was determined in 12 normal human volunteers and four patients with erythroleukemia (EL), two patients with refractory anaemia with excess blasts (RAEB), and one patient with de novo acute myelogenous leukaemia (AML). The bone marrow cells were cultured in a microtitre methylcellulose system containing 30% human AB serum and human urinary Ep in concentrations ranging from 0 to 2 units/ml. Erythroid colony growth from normal marrow cultures was Ep-dependent. It was augmented by added Ep and inhibited by Ep antiserum. Marrow cells from one patient with EL and one patient with RAEB after transformation to AML had no erythroid colony formation with or without added Ep. All of the remaining patients formed 'spontaneous' or endogenous erythroid colonies (EEC) without the addition of Ep. In three of these (two with EL and one with de novo AML), the erythroid colony formation was augmented by added Ep. In three other patients (one with EL and two with RAEB), erythroid colony growth was unaffected by added Ep or Ep antiserum, and thus appeared to be Ep-independent.