Growth factor is sometimes used interchangeably among scientists with the term cytokine. Historically, cytokines were associated with hematopoietic (blood 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 the hematopoietic and immune systems used 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 division, cytokine is a neutral term with respect to whether a molecule affects proliferation. In this sense, some cytokines can be growth factors, such as G-CSF and GM-CSF. However, some cytokines have an inhibitory effect on cell growth or proliferation. Yet others, such as Fas ligand are used as "death" signals; they cause target cells to undergo programmed cell death or apoptosis.
While growth factor implies a positive effect on cell division, cytokine is a neutral term with respect to whether a molecule affects proliferation. In this sense, some cytokines can be growth factors, such as G-CSF and GM-CSF. However, some cytokines have an inhibitory effect on cell growth or proliferation. Yet others, such as Fas ligand are used as "death" signals; they cause target cells to undergo programmed cell death or apoptosis.
Example of growth factors
Individual growth factor proteins tend to occur as members of larger families of structurally and evolutionarily related proteins. There are dozens and dozens of growth factor families such as TGF-beta (transforming growth factor-beta), BMP (bone morphogenic protein), neurotrophins (NGF, BDNF, and NT3), fibroblast growth factor (FGF), and so on.
Several well known growth factors are:
1Transforming growth factor beta (TGF-β)
2Granulocyte-colony stimulating factor (G-CSF)
3Granulocyte-macrophage colony stimulating factor (GM-CSF)
4Nerve growth factor (NGF)
5Neurotrophins
6Platelet-derived growth factor (PDGF)
7Erythropoietin (EPO)
8Thrombopoietin (TPO)
9Myostatin (GDF-8)
10Growth differentiation factor-9 (GDF9)
11Acidic fibroblast growth factor (aFGF or FGF-1)
12Basic fibroblast growth factor (bFGF or FGF-2)
13Epidermal growth factor (EGF)
14Hepatocyte growth factor (HGF)
Individual growth factor proteins tend to occur as members of larger families of structurally and evolutionarily related proteins. There are dozens and dozens of growth factor families such as TGF-beta (transforming growth factor-beta), BMP (bone morphogenic protein), neurotrophins (NGF, BDNF, and NT3), fibroblast growth factor (FGF), and so on.
Several well known growth factors are:
1Transforming growth factor beta (TGF-β)
2Granulocyte-colony stimulating factor (G-CSF)
3Granulocyte-macrophage colony stimulating factor (GM-CSF)
4Nerve growth factor (NGF)
5Neurotrophins
6Platelet-derived growth factor (PDGF)
7Erythropoietin (EPO)
8Thrombopoietin (TPO)
9Myostatin (GDF-8)
10Growth differentiation factor-9 (GDF9)
11Acidic fibroblast growth factor (aFGF or FGF-1)
12Basic fibroblast growth factor (bFGF or FGF-2)
13Epidermal growth factor (EGF)
14Hepatocyte growth factor (HGF)
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