text: Transforming growth factor (, or TGF) is used to describe two classes of polypeptide growth factors, TGFα and TGFβ.
  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.