Growth factor is a type of polypeptide that binds to specific, high-affinity cell membrane receptors and regulates multiple effects such as cell growth and other cellular functions. It is a cytokine secreted by a variety of cells, acting on specific target cells, regulating cell division, matrix synthesis, and tissue differentiation. Growth factors are present in platelets and various adult and embryonic tissues and most cultured cells, and have certain specificity for different types of cells. Generally, the growth of cultured cells requires the coordination of multiple growth factor sequences, and the tumor cells are characterized by independent growth independent of growth factors. In terms of secretion characteristics, growth factors mainly belong to autocrine and paracrine. Many growth factors have been purified and their structural composition determined. For example, platelet-derived growth factor (PDGF) is a thermostable, highly positively charged protein composed of dimers containing disulfide bonds with a molecular weight of around 30,000 Daltons. In another example, epidermal growth factor (EGF) is a thermostable polypeptide containing 53 amino acid residues with a molecular weight of about 6000 Daltons. Various growth factors have their corresponding receptors and are transmembrane proteins that are ubiquitous on the cell membrane. Many receptors have kinase activity, especially tyrosine kinase activity.
Figure 1. Protein structure of growth factor.
There are many types of growth factors, such as platelet growth factor (platelet-derived growth factor, PDGF; osteosarcoma-derived growth factor ODGF), epidermal growth factor (epidermal growth factor EGF, transforming growth factor TGFα and TGFβ), fibroblast growth. Factor (αFGF, βFGF), insulin-like growth factor (IGF-I, IGF-II), nerve growth factor (NGF), interleukin growth factor, red blood cells Auxin, colony stimulating factor (CSF), and so on. Since growth factors are secreted by normal cells, neither drug-toxic nor immune response, some of them have been tested for clinical treatment while studying their physiological mechanisms. For example, interleukin-2 has been used to treat cancer, and has obvious effects on kidney cancer and melanoma; it is also used in immunomodulators and diseases related to home immunity. Interleukin-3 is used to treat indications such as bone marrow failure and thrombocytopenia. Epidermal growth factor is used for human burns, wounds, diabetic skin ulcers, acne, varicose skin ulcers and corneal damage to promote wound healing.
Growth factor is an active protein or polypeptide substance that exists in an organism and has a broad regulatory effect on the growth and development of the organism. Its general characteristics are that it can bind to cell membrane specific receptors, regulate cell growth and development, regulate immunity, hematopoiesis, tumorigenesis, inflammation and infection, wound healing, blood vessel formation, cell differentiation, apoptosis, and morphology. Occurrence, embryo formation and other aspects have an important regulatory role. Cytokine is widely present in various tissues in the body, including mature tissues and embryonic tissues, and regulates proliferation and differentiation of various cells by autocrine and or paracrine means. Many cells cultured in vitro also release growth factors.
In the past two decades, growth factors have been increasingly used to treat blood and tumor diseases and cardiovascular diseases, such as: Neutropenia, Myelodysplastic syndrome (MDS), leukemia, Aplastic anemia, Bone marrow transplantation, Angiogenesis of cardiovascular disease.
Growth factor receptor
Growth factor receptor is a receptor which binds to growth factor. Growth factor receptors are the first stop in cells where the signaling cascade for cell differentiation and proliferation begins. Growth factors, which are ligands that bind to the receptor are the initial step to activating the growth factor receptors and tells the cell to grow and/or divide. These receptors may use the JAK/STAT, MAP kinase, and PI3 kinase (Figure 2) pathways.
Figure 2. Protein structure of Phosphoinositide 3-kinases.
1. Cottler-Fox M.; et al. Transfusion support of hematology and oncology patients. The role of recombinant hematopoietic growth factors. Archives of Pathology & Laboratory Medicine. 1994, 118 (4): 417–20.
2. Aaronson SA. Growth factors and cancer. Science. 1991, 1254 (5035): 1146–53.