In vitro biology of human myeloid leukemia.

For about 40 years, the biology of human myeloid leukemia (ML) has been studied in different in vitro systems. Throughout this time, semisolid colony assays, Dexter-type long-term cultures and liquid suspension cultures have contributed to our understanding of the mechanisms involved in the origin and progression of this hematological disorder. By using such systems, it has been possible to identify the cells in which leukemia originates; to recognize a functional hierarchy within the hematopoietic system of leukemia patients; to identify factors, soluble and cell-associated, that regulate leukemic growth; and to study the effects of different antineoplastic drugs. Furthermore, in vitro systems for purging of leukemic cells have been developed. Still, many questions and problems remain unsolved regarding the biology of myeloid leukemia in vitro. This article presents a comprehensive review on the behavior of leukemic stem and progenitor cells, both from acute and chronic myeloid leukemia, in the different culture systems mentioned above.