Growth of a cultured leukemia subline was promoted by conditioned medium of thymic reticuloepithelial-like cells (B6TE)

Established leukemia cell lines: their role in the understanding and control of leukemia proliferation

For investigation of mechanisms of leukemogenesis and control of proliferation of leukemia cells, various preleukemic hematopoietic progenitor cell lines and leukemia cell lines have been established. The role of these established cell lines in understanding leukemogenesis and control of leukemia cell proliferation is described. The results of studies on biological characteristics of numerous human leukemia-lymphoma cell lines suggest that the heterogeneity in various markers of the cell lines reflects different patterns of normal hematopoietic cell differentiation. Then, recent studies on the control of proliferation of leukemia cells by induction of terminal differentiation with the use of established leukemia cell lines both in vitro and in vivo are described. Therapeutic significance of the results obtained with these leukemia cell lines is also discussed.

Isolation and characteristics of a leukemia-growth-promoting factor from calf thymus

Leukemia-growth-promoting factor (LGPF) as we previously reported stimulates the growth of a murine leukemia subline (L17R) extensively. LGPF was isolated and 10(4) fold purified from calf thymuses by a combination of ammonium sulfate precipitation, Sephadex G-100 chromatography, hydroxylapatite chromatography, and Mono S-fast protein liquid chromatography (Mono S-FPLC). The mol. wt of LGPF was estimated to be approximately 25,000 a.m.u. from the elution pattern of Sephadex G-100 chromatography. The activity had high affinity for Mono S beads which are cation exchangers. Mono S fractions of LGPF are effective at a low concentration of 5 ng/ml. The activity was inactivated by heat (56 degrees C, 30 min), 1 mg/ml trypsin (37 degrees C, 1h), and 50 mM dithiothreitol (20 degrees C, 1h). The growth L17R leukemia cells are not only stimulated by LGPF, but also by pituitary and brain fibroblast growth factor (FGF). These data strongly suggest that LGPF is a heat sensitive cationic protein(s) acting as a member of FGF family.