Characterization of growth inhibitory factors for mouse monocytic leukemia cells.
Growth inhibitory (GI) factors for mouse monocytic leukemia cells were previously found in conditioned medium (CM) of a clone of mouse myeloblastic leukemia Ml cells (R1-GI factor) and in CM of mouse lung tissue (L-GI factor). In the present study, the effects of these GI factors on the growth of variant cell lines (Mm-A, Mm-P and Mm-S2) of mouse monocytic line Mm-1 cells were examined. Mm-A are highly leukemogenic to syngeneic SL mice, Mm-P cells are moderately leukemogenic, while Mm-S2 cells have little or no leukemogenicity. The R1-GI factor markedly suppressed the growth of Mm-A cells, whereas it inhibited the growth of Mm-P and Mm-S2 cells only moderately. Recombinant mouse interferon beta (IFN beta) had similar target specificities to those of the R1-GI factor on these variant cells. Moreover, anti-mouse IFN beta antibody completely neutralized the GI activity of the R1-GI factor on Mm-A cells. These results show that the R1-GI factor and mouse IFN beta are very similar and probably identical proteins. The L-GI factor had different target specificities from the R1-GI factor: it showed strongest GI activity on Mm-P cells, moderate GI activity on Mm-S2 cells and weak GI activity on Mm-A cells. Recombinant human interleukin 6 (IL-6) had similar target specificities to the L-GI factor on these Mm-1 variant cells. Furthermore, the L-GI factor could support the proliferation of IL-6-dependent MH60.BSF2 cells. Anti-mouse IL-6 antiserum neutralized the GI activity of the L-GI factor on Mm-P cells. Thus the L-GI factor and mouse IL-6 seem to be closely related and possibly to be identical proteins.
Kasukabe
T
T
Department of Chemotherapy, Saitama Cancer Center Research Institute, Japan.
Okabe-Kado
J
J
Honma
Y
Y
Hozumi
M
M
Matsuda
T
T
Hirano
T
T
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D006131:Growth Inhibitors / Q000302:isolation & purification*; D066298:In Vitro Techniques; D016899:Interferon-beta / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000473:pathology*; D051379:Mice; D014407:Tumor Cells, Cultured
D006131:Growth Inhibitors; D015850:Interleukin-6; D016899:Interferon-beta