Paracrine action of transforming growth factors.
Polypeptide growth factors form a class of regulatory molecules which exert their effects by binding to specific receptors present on the cell surface. Most of the time the exact role of these factors in the healthy body is unknown. Some, like PDGF and TGF beta, seem to be involved in wound healing. Others, like EGF, promote epithelial cell growth and differentiation. The site of synthesis of most polypeptide growth factors is unknown. Their target can be identified by detecting the cells which present the specific receptors at their surface. It is though that polypeptide growth factors have a paracrine mode of action. Many different cancerous cells produce polypeptide growth factors and the appropriate receptors. Thus, they are able to stimulate their own growth in an autocrine fashion. Recently, some polypeptide growth factors and receptor genes or cDNAs have been molecularly cloned. Growth factor genes and messengers are much more complex than would be expected from the size of the polypeptide. Some cDNAs have been introduced into bacterial expression vectors and large amounts of the factors have been produced by bacteria. New tools, such as molecular probes and specific antibodies, are thus now available to investigate the production of the growth factors and their receptors. The same tools will facilitate the identification and understanding of the molecular mechanism whereby cancerous cells produce the growth factors and the appropriate receptors simultaneously. The importance of growth factors and receptors in cancer is stressed by the finding that three oncogenes are in fact the genes coding for one growth factor and two receptors. Finally, the molecular probes and the specific antibodies raised against these molecules can be used to identify precisely the growth factor(s) and receptor(s) produced abnormally in cancers. Antibodies that inhibit specifically the interaction of this very growth factor with its receptor could then be developed, thus allowing human tumour cell growth to be controlled.
D000818:Animals; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D004702:Endocrine Glands / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000502:physiology; D066246:ErbB Receptors; D006133:Growth Substances / Q000502:physiology; D006801:Humans; D009369:Neoplasms / Q000503:physiopathology; D009857:Oncogenes; D010455:Peptides / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology; D017479:Receptors, Platelet-Derived Growth Factor; D015291:Transforming Growth Factors
D006133:Growth Substances; D010455:Peptides; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D015291:Transforming Growth Factors; D066246:ErbB Receptors; D017479:Receptors, Platelet-Derived Growth Factor