Control of cell division by growth factors

Basically, cell division (mitosis) can be controlled
by stimulation or inhibition. In the absence
of stimulation or with active inhibition,
no mitosis occurs. Growth factors have an effect
not only on specific types of cells, but also on
defined phases of the cell cycle. The most
frequently controlled phase of the cell cycle is
the transition from G0 to G1. The growth factor
group includes growth factors for epidermal
cells (EGF), for nerve cells (NGF), for connective
tissue or mesenchymal cells (fibroblasts, FGF),
and for thrombus-forming cells in the inner lining
(endothelium) of blood vessels (PDGF).
Their stimulating effect may be opposed by an
antagonistic effect (e.g., TGF!, transforming
growth factor, or TNF, tumor necrosis factor).
The function of each growth factor is mediated
by a specific receptor.