ONCOSTATIN-M IS A MEMBER OF A CYTOKINE FAMILY THAT INCLUDES LEUKEMIA-INHIBITORY FACTOR, GRANULOCYTE COLONY-STIMULATING FACTOR, AND INTERLEUKIN-6

Oncostatin M (OSM), a glycoprotein of M(r) almost-equal-to 28,000 produced by activated monocyte and T-lymphocyte cell lines, was previously identified by its ability to inhibit the growth of cells from melanoma and other solid tumors. We have detected significant similarities in the primary amino acid sequences and predicted secondary structures of OSM, leukemia-inhibitory factor (LIF), granulocyte colony-stimulating factor (G-CSF), and interleukin 6 (IL-6). Analysis of the genes encoding these proteins revealed a shared exon organization, suggesting evolutionary descent from a common ancestral gene. Using a panel of DNAs from somatic cell hybrids, we have shown that OSM, like LIF, is located on human chromosome 22. We have also demonstrated that OSM has the ability to inhibit the proliferation of murine M1 myeloid leukemic cells and can induce their differentiation into macrophage-like cells, a function shared by LIF, G-CSF, and IL-6. We propose that OSM, LIF, G-CSF, and IL-6 are structurally related members of a cytokine family that have in common the ability to modulate differentiation of a variety of cell types.