Transforming growth factor

Transforming growth factor (sometimes referred to as Tumor growth factor, or TGF) is used to describe two classes of polypeptide growth factors, TGF&alpha; and TGF&beta;.

The name "Transforming Growth Factor" is somewhat arbitrary, since the two classes of TGFs are not structurally or genetically related to one another, and they act through different receptor mechanisms. Furthermore, they do not always induce cellular transformation, and are not the only growth factors that induce cellular transformation.

Types

 * TGF&alpha; is upregulated in some human cancers. It is produced in macrophages, brain cells, and keratinocytes, and induces epithelial development.


 * TGFβ exists in three known subtypes in humans, TGF&beta;1, TGF&beta;2, and TGF&beta;3. These are upregulated in some human cancers, and play crucial roles in tissue regeneration, cell differentiation, embryonic development, and regulation of the immune system. Isoforms of transforming growth factor-beta (TGF-β1) are also thought to be involved in the pathogenesis of pre-eclampsia. TGF&beta; receptors are single pass serine/threonine kinase receptors.

Function
These proteins were originally characterized by their capacity to induce oncogenic transformation in a specific cell culture system, rat kidney fibroblasts. Application of the transforming growth factors to normal rat kidney fibroblasts induces the cultured cells to proliferate and overgrow, no longer subject to the normal inhibition caused by contact between cells.