| Gastric cancer is one of serious gastrointestinal cancers affecting human health. In recent years, the incidence rate decreased, but it is still the world second death caused by cancer, there are 750,000 people died each year due to stomach cancer. A number of studies have shown that the occurrence and development of gastric cancer are closely related to inflammation. Chronic inflammation can activate chemokines, growth factors, reactive oxygen and other substances, which can activate inflammatory cells in the gastrointestinal tract, increase cell cycle, prevent tumor suppressor pathway, activate oncogenes and further lead to tumorigenesis. Once tumor forms, inflammation will promote the proliferation and differentiation of tumor cells, inhibit its apoptosis, promote angiogenesis and metastasis which lead to further tumor development. Many animal models have demonstrated that the occurrence and development of gastric cancer has close relationship with chronic inflammation.Phospholipase A2 (PLA2) is a broad categorie of enzymes that catalyze the hydrolysis of fatty acid at the sn-2 position of glycerophospholipid on cell membranes, which can decompose the arachidonic acid that produced by phospholipids, further metabolism to produce cycloxygenase (COX) and prostaglandin E2 (PGE2), then trigger inflammation, so PLA2 is the trigger point of inflammation, located upstream of the inflammatory response, also has the title of death switch. Studies have shown that the occurrence and development of a variety of tumors have a direct or indirect relationship with the progression of PLA2. Comparing with normal gastric mucosa, patients with gastritis and gastric cancer had also showed high expression of PLA2.We also screened out PLA2 in preliminary work by the way of metabolomics, and found that the development of gastric cancer have a close relationship with it. According to its function and distribution, it can be divided into five categories, in which cytoplasmic PLA2 (cPLA2) can hydrolysis membrane phospholipids then produce arachidonic acid involved in a variety of inflammatory reactions. The cPLA2-IVA or cPLA2a, (gene PLA2G4A), was first identified. It is also the most abundant and most closely related to inflammation. It’s speculated that as a pro inflammatory cytokines, cPLA2a plays an important role in regulating biological function in gastric cancer. COX-2 is a downstream product of PLA2, inflammatory cytokines, is a hot topic in the research of cancer especially in the gastric cancer. NASID, the inhibitor of COX-2, can reduce initiation of colon cancer. High expression of COX2 is also closely associated with stomach cancer differentiation and Lauren type, it suggests that COX2 can be used as a new prognostic indicator of gastric cancer.The traditional Chinese herbal Glycyrrhizic acid (GA) is extracted from licorice roots and stems. It has the following functions:antiarthritic, antiallergic, antiviral, antihepatotoxic, anticholinergic, antiestrogenic and anti-inflammatory. GA can be generated to glycyrrhetinic acid through metabolic processes which is the main form to play the role in human body. Studies show that glycyrrhetinic acid can suppresse the activation of cPLA2/AA pathway then prevent inflammation to treat various inflammatory diseases. Magnesium isoglycyrrhizinate (MgIG) is the fourth generation of glycyrrhetinic acid derivatives. Therefore we speculate whether magnesium isoglycyrrhizinate can prevent gastric cancer by intervening the expression of cPLA2a and reducing expression of COX-2. So we have two parts, the first part:We will discuss the effect of different concentrations of magnesium isoglycyrrhizinate on proliferation of murine gastric cancer MFC cell lines by reducing the expression of cPLA2a and COX-2 in vitro; Second part: we study the effect of magnesium isoglycyrrhizinate on the intervention of gastric cancer development in vivo.PART 1 Effects of Magnesium Isoglycyrrhizinate on the Proliferation of MFC Cell Line in VitroObjective:After magnesium isoglycyrrhizinate treating the MFC cell lines, we observe the inhibitory effect of magnesium isoglycyrrhizinate in the concentration range and detect the mRNA and protein level of cPLA2a and COX-2. Further to do the preliminary discussion to its potential mechanism.Methods:After treating the MFC cell line by variable dose of magnesium isoglycyrrhizinate, we selected suitable concentration for subsequent experiments by cell proliferation assays and observed the inhibition of cell proliferation by tablet cloning experiments. We detected the effects of drug on cell cycle and apoptosis by flow cytometry. And we detected the mRNA and protein level of cPLA2a and COX-2 by RT-PCR and Western blot analysis.Result:Compared with the control group the proliferation capacity of MFC cell line in the experimental group diminished and promote cell apoptosis. Colony formation was significantly decreased. mRNA and protein expression levels of cPLA2a were significantly reduced, with showing a concentration-dependent manner. But the mRNA and protein expression of COX-2 had no significantly change.Conclusion:Isoglycyrrhizinate magnesium can inhibit proliferation and promote apoptosis of murine gastric cancer cell line MFC through down-regulating of expression of inflammatory cytokines cPLA2a.PART 2 Inhibitory Effects of Magnesium Isoglycyrrhizinate on the Development of Gastric Cancer in VivoObjective:Subcutaneous tumor-bearing mice were randomly divided into six groups. After giving different concentrations of anti-inflammatory drugs, magnesium isoglycyrrhizinate, or combined with chemotherapy drugs. By comparing the weight and size of tumor, and period of survival time to investigate the effects of magnesium isoglycyrrhizinate on the development of gastric cancer in subcutaneous tumor-bearing mice. Also morphological changes of tumor tissue were observed after HE staining. Immunohistochemistry and western blot were used to detect the expression of inflammatory cytokines cPLA2a and COX-2 in each group.Methods:Establish the tumor-bearing model with MFC cell line,615 mice were divided into six groups randomly. Groups were tumor-bearing mice with saline control group, tumor-bearing mice with low doses of magnesium isoglycyrrhizinate (50mg/kg) treatment group, tumor-bearing mice with high doses of magnesium isoglycyrrhizinate (200mg/kg) treatment group, tumor-bearing mice treated with chemotherapy drugs group, tumor-bearing mice with chemotherapy treatment combined with magnesium isoglycyrrhizinate low dose (50mg/kg) group, tumor-bearing mice treated with chemotherapy treatment combined with magnesium isoglycyrrhizinate high dose (200mg/kg) group. After 14 days of drug administration, we discussed the effects of the magnesium isoglycyrrhizinate on tumor activity by measuring the size and weight of the tumor tissue, and observed the expression of cPLA2a and COX-2.Result:After 14 days of drug administration, comparing tumor-bearing with high doses of magnesium isoglycyrrhizinate (200mg/kg) treatment group, tumor-bearing mice treated with chemotherapy drugs group, tumor-bearing mice with chemotherapy treatment combined with magnesium isoglycyrrhizinate low dose (50mg/kg) group, tumor-bearing mice with chemotherapy treatment combined with magnesium isoglycyrrhizinate high dose (200mg/kg) group compared with the control group, the rumor weight (p<0.05) and size(p<0.01) reduced survival time prolonged (p<0.05). The expression of cPLA2a and COX-2 were significantly lower than that of control group. And HE staining of tumor tissue did not change significantly.Conclusion:Magnesium Isoglycyrrhizinate can interfere with the development of gastric cancer in vivo, which may be related to suppress the expression of inflammatory cytokines cPLA2a and COX-2. |
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