Oncostatin

Oncostatin M (OSM) is a cytokine of the interleukin-6 (IL-6) family. It was first identified for its effects on cell growth and later recognized as a multifunctional mediator of inflammation, development, and tissue remodeling. In humans, the protein is encoded by the OSM gene and is produced by a variety of cell types, including activated T cells, macrophages, neutrophils, and some tumor cells. Expression levels increase in inflammatory contexts.

OSM is a relatively small secreted protein (~22 kDa) that signals through gp130-containing receptor complexes. In most cells, it binds to a heterodimer consisting of gp130 and the OSM receptor beta (OSMRβ); in a subset of cell types, it can also signal via a gp130–LIF receptor (LIFR) complex. Receptor engagement activates intracellular pathways such as JAK/STAT (notably STAT3), MAPK, and PI3K, leading to changes in gene expression and cellular behavior.

The biological actions of OSM are pleiotropic. It influences inflammation, hematopoiesis, development, bone remodeling, liver regeneration, and tissue repair. OSM can induce hepatic acute-phase responses, affect adipogenesis, promote osteoblast differentiation, and modulate endothelial and neural cell function. In the tumor microenvironment, its effects on cancer cell growth and metastasis are context-dependent, sometimes promoting and other times inhibiting tumor progression.

Clinical relevance of OSM is explored in inflammatory diseases, cancer, and liver injury, where it may contribute to pathology or tissue remodeling or serve as a potential therapeutic target. Its diverse actions reflect the complex, context-specific roles of IL-6 family cytokines.