Growth factors typically act as
signaling molecules between cells. Examples are
cytokines and
hormones that bind to specific
receptors on the surface of their target
cells.
Growth factor is sometimes used interchangeably among scientists with the term cytokine.[3] Historically, cytokines were associated with
hematopoietic (blood and lymph forming) cells and
immune system cells (e.g.,
lymphocytes and tissue cells from
spleen,
thymus, and
lymph nodes). For the
circulatory system and
bone marrow in which cells can occur in a liquid suspension and not bound up in solid
tissue, it makes sense for them to communicate by soluble, circulating protein
molecules. However, as different lines of research converged, it became clear that some of the same signaling proteins which the hematopoietic and immune systems use were also being used by all sorts of other cells and tissues, during development and in the mature organism.
While growth factor implies a positive effect on
cell proliferation, cytokine is a neutral term with respect to whether a molecule affects proliferation. While some cytokines can be growth factors, such as
G-CSF and
GM-CSF, others have an inhibitory effect on
cell growth or cell proliferation. Some cytokines, such as
Fas ligand, are used as "death" signals; they cause target cells to undergo programmed
cell death or apoptosis.
Individual growth factor proteins tend to occur as members of larger families of structurally and
evolutionarily related proteins. There are many families, some of which are listed below:
For the last two decades, growth factors have been increasingly used in the treatment of
hematologic and
oncologic diseases[4][5] and cardiovascular diseases[6][7] such as:
^Cottler-Fox M, Klein HG (April 1994). "Transfusion support of hematology and oncology patients. The role of recombinant hematopoietic growth factors". Archives of Pathology & Laboratory Medicine. 118 (4): 417–20.
PMID7909429.