A comparison of the growth supporting capacities of fresh and cultured leukemic blast cells.

Clonogenic progenitors of the blast population in acute myeloblastic leukemia (AML) grow exponentially in suspension in the presence of a source of growth factors (media conditioned by the continuous cell line HTB9) and provided a high cell density is maintained. We investigated this latter requirement by comparing blasts freshly obtained from patients to others that had been maintained in culture. We found that cultured cells lost their growth-promoting capacity. Further, membranes from fresh cells but not cultured cells were active in stimulating growth. Repeated additions of fresh cells to suspension cultures prolonged the exponential phase but did not permit continuous culture.