Inhibitory Effect Of AMPK To The Expression Of TGF-β1 In Gastric Cancer

Background and Objectives:With the increasing environmental pollutants,the accelerated industrialization,and new chemical substances,combined with the adverse lifestyle and behavioral habits,cancer has became one of the major diseases that endangers human life and health.Nationally retrospective surveys of death in China have revealed that the morbidity and mortality of malignancy have significant increases in past two decades,lung cancer,liver cancer and gastric cancer are among the top three.The main cause of death are the widespread metastasis and recurrence without effective treatments.In addition to the uncontrolled growth,cancer cells also can invade surrounding normal tissue locally and even migrate to other parts of the body through the circulatory system or lymphatic system.There are two prerequisites for the cancer cell migration:acquired abilities of invasion and migration through epithelial cells to mesenchymal cells(EMT),and acquisition of stem cell characteristics,achieving self-renewal and rapid proliferation.Transforming growth factor-β1 is an important induction factor of EMT,which is essential for tumor metastasis,angiogenesis,pathologic stage and prognosis.In a variety of solid tumors,TGF-β1 is over-expressed,accompanied by higher expression or activation of downstream molecules.The active TGF-β1 signal can promote the progression from early to advanced stages.It has been reported that the high expression of TGF-β1 in gastric cancer plays an important role in invasion and lymph node metastasis,therefore,high level of TGF-β1 plays a crucial role in tumor metastasis and recurrence.Taken together,inhibition of TGF-β1 expression in gastric cancer may provide a good curative effect for cancer therapy.AMPK is known as a tumor suppressor gene.Many have shown that AMPK activators(represented by metformin,AICAR,phenformin,A769962)can inhibit the proliferation and migration of cancer cells.Our previous immunohistochemical study indicated that p-AMPK is lower than normal tissue adjacent to gastric cancer,while TGF-β1 is higher.Meanwhile,AMPK activation inhibits TGF-β1 signal transduction.Thus,in the present study we attempt to explore whether the activation of AMPK can inhibit the expression of TGF-β1.This study will provide new horizons on the clinical applications of AMPK activators for inhibiting tumor metastasis.Research methods:1.To examine AMPK activity and TGF-β1 level in gastric cancer tissues,59 cases of different clinical stages of gastric cancer specimens were collected from the First Affiliated Hospital of Nanchang University.Statistical analysis of AMPK activity and TGF-β1 level was used to evaluate.2.To examine the TGF-β1 levels in serum of patients with type 2 diabetes treated with metformin,other type 2 diabetes patients,and normal subjects’ significance and correlation,Milliplex MAP cytokines detection method was used.In this study we selected 44 normal subjects,48 diabetic patients without other glucose lowering drugs,and 40 diabetic patients treated with metformin.3.To examine the effect of AMPK activators on the TGF-β1 m RNA level in gastric cancer cell lines.The magnetic beads method and quantitative PCR were used.4.To examine the effect of metformin on TGF-β1 promoter activity plamids were transfected into gastric cells and firely luciferase reporter was measured.5.To test if metformin inhibited TGF-β1 expressionin gastric cancer cells,Western Blotting was performed.Results:1.They displayed a negative correlation in different clinical stages of gastric cancer specimens.The p-AMPK expression was higher but TGF-β1 level was lower in gastric tissues adjacent to carcinoma.2.The expression of TGF-β1 in Type II diabetes patient serums was significantly higher than patients with metformin and normal subjects.3.AMPK activators inhibited the TGF-β1 m RNA level in gastric cancer cells.4.TGF-β1 promoter activity ingastric cancer cellls,which was enhanced by TGF-β1 and was suppressed by metformin.5.Likewise,metformin also reduced protein levels of TGF-β1 in gastric cancer cells.Conclusion:1.Lower AMPK activity and higher TGF-β1 level was found in gastric cancer tissues.Meanwhile,the expression of TGF-β1 was decreased after metformin treatments in serums of Type II diabetes patients.2.AMPK activation inhibited the promoter activity,leading to suppression of TGF-β1 expression.3.Our study suggest that metformin could be a promising therapeutic drug target for advanced gastirc cancer.