M-CSF (or CSF-1) is a hematopoietic growth factor that is involved in the proliferation, differentiation, and survival of
monocytes,
macrophages, and bone marrow progenitor cells. M-CSF affects macrophages and monocytes in several ways, including stimulating increased phagocytic and chemotactic activity, and increased tumour cell cytotoxicity. The role of M-CSF is not only restricted to the monocyte/macrophage cell lineage. By interacting with its membrane receptor (
CSF1R or M-CSF-R encoded by the c-fms proto-oncogene), M-CSF also modulates the proliferation of earlier hematopoietic progenitors and influence numerous physiological processes involved in immunology, metabolism, fertility and pregnancy. M-CSF released by
osteoblasts (as a result of
endocrine stimulation by
parathyroid hormone) exerts
paracrine effects on
osteoclasts. M-CSF binds to receptors on
osteoclasts inducing differentiation, and ultimately leading to increased plasma
calcium levels—through the
resorption (breakdown) of bone. Additionally, high levels of CSF-1 expression are observed in the endometrial epithelium of the pregnant uterus as well as high levels of its receptor
CSF1R in the placental
trophoblast. Studies have shown that activation of trophoblastic CSF1R by local high levels of CSF-1 is essential for normal embryonic implantation and placental development. More recently, it was discovered that CSF-1 and its receptor
CSF1R are implicated in the mammary gland during normal development and
neoplastic growth. == Clinical significance ==