About Transforming Growth Factor:
The term “transforming growth factor” is a little arbitrary. This is because the two classes of transforming growth factor (often referred to as tumour growth factor or just TGF) are not structurally or genetically related. They act through different receptor mechanisms and they do not always induce cellular transformation. Furthermore, they are not the only growth factors which induce cellular transformation.
Types of Transforming Growth Factor
There are two main forms of TGF.
● TGF alpha (TGF-α) is upregulated in certain human cancers. It is produced in macrophages, brain cells and keratinocytes. It induces epithelial development.
● TGF beta (TGF-β) exists in three subtypes in humans. These are TGF-β1, TGF-β2 and TGFβ-3. These are upregulated are Marfan’s syndrome, a genetic disorder of the connective tissue, and several human cancers. It plays a crucial role in tissue regeneration, embryonic development, cell differentiation, and the regulation of the immune system. Isoforms of TGF beta (TGF-β1) are thought to be involved in the pathogenesis of pre-eclampsia. TGF-β receptors are single pass serine/threonine kinase receptors.
TGF alpha is a protein that is encoded by the TGFA gene in humans. It’s a member of the epidermal growth factor family, making it a mitogenic polypeptide. The protein activates when bound to receptors capable of protein kinase activity for cellular signalling.
TGF alpha is a transforming growth factor that is a ligand for the epidermal growth factor receptor. It activates a signalling pathway for cell proliferation, differentiation and development. The protein may act as a transmembrane-bound ligand or alternatively, a soluble ligand. The gene has been associated with many different types of cancers and it’s possible it can be involved in cases of cleft lip/palate.
The transforming growth factor beta superfamily is a group of structurally related cell regulatory proteins. Since its discovery in 1983, many proteins have been described as members of the TGF beta superfamily in a variety of different species. This includes vertebrates as well as invertebrates. It has since been categorized into 23 distinct gene types that fall into four major groups:
● The TGF beta subfamily
● The decapentaplegic Vg-related (DVR) related subfamily
● The activin and inhibin subfamily
● A group of various divergent members
Transforming growth factor proteins were first characterized by their ability to induce oncogenic transformation in a specific cell culture system, rat kidney fibroblasts. Since then, application of the transforming growth factors to normal rat kidney fibroblasts induces the cultured cells to proliferate and overgrow. THey no longer became subject to the normal inhibition caused by contact between cells.