Epidermal growth factor (EGF) is a heat-resistant single-chain low-molecular-weight polypeptide consisting of 53 amino acid residues. After EGF specifically recognizes and binds to the EGF receptor on target cells, a series of biochemical reactions occur, which can ultimately promote DNA synthesis and mitosis in target cells. EGF is a sugar-free site, very stable, heat and acid resistant, and is widely present in body fluids and various glands. It is mainly synthesized by the submandibular gland and duodenum. The content of sera and semen increased specifically, but the concentration in serum was low. EGF has a wide range of effects and is of great significance in estimating tumor prognosis, selecting treatment options, and treating gastric ulcer and liver failure. Clinically, radioimmunoassay (RIA) or double antibody enzyme-linked immunosorbent assay (ELISA) can be used to determine the EGF content in serum or body fluids.
Figure 1. Protein structure of EGF.
Epidermal growth factor assays can be used to diagnose a variety of tumors and ulcers.
Elevation: Many tumors have abnormal expression of EGF and its receptors, and are closely related to tumor metastasis and patient prognosis, such as gastric cancer, liver cancer, breast cancer, and melanoma. In patients with gastric cancer, the lower the degree of differentiation of gastric cancer cells, the higher the EGF level; the serum EGF level in patients with advanced gastric cancer is higher than that in early patients. EGF and its receptors are also significantly increased in liver cancer tissues and precancerous lesions.
Decrease:EGF has a wide range of biological effects on the digestive system, can stimulate target cell DNA synthesis, regulate cell defense and gastrointestinal secretion, can act on parietal cells, inhibit gastric acid and pepsin secretion, so EGF may be a natural gastrointestinal mucosa Growth-promoting factors are related to the occurrence of peptic ulcers. The gastric fluid and serum EGF content in patients with duodenal ulcers are significantly reduced.
The binding of EGF to EGFR results in cell proliferation, differentiation and survival. Salivary EGF appears to be regulated by inorganic iodine in the diet and also plays an important physiological role in maintaining the integrity of the esophagus and stomach tissues. The biological effects of saliva EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, stimulation of DNA synthesis, and damage to intraluminal damage factors (such as gastric acid, bile acid, pepsin, and trypsin), as well as physical and chemical mucosa Protective and bacterial agents.
Figure 2. Protein structure of EGFR.
EGF works through high affinity binding to epidermal growth factor receptor (EGFR) on the cell surface. This stimulates ligand-induced dimerization, activating the receptor's intrinsic protein-tyrosine kinase activity (see the second figure). The tyrosine kinase activity in turn triggers a signal transduction cascade, which leads to various biochemical changes in the cell-increased intracellular calcium levels, increased glycolysis and protein synthesis, and increased expression of certain genes, Including EGFR-ultimately leads to DNA synthesis and cell proliferation.
Figure 3. Diagram showing key components of the MAPK/ERK pathway.