| Background:Gastric cancer(GC)is the fifth leading cause of cancer morbidity worldwide and is the leading cause of cancer-related death.In China,gastric cancer is one of the most common malignancies.The mortality rate of GC is high,behind lung cancer and liver cancer.Metastasis and invasion are still the main causes of high mortality.Therefore,it is very important to study the molecular mechanism of gastric cancer migration and invasion.MicroRNAs(miRNAs)are a kind of small noncoding RNAs,which play important roles in the tumorigenesis and development of tumor.Studies have shown that aberrant expression of miRNAs can function as tumor suppressor or oncogenes by targeting other genes involved in GC cell migration,invasion and proliferation.Let-7 was found as one of the first known human miRNA.Its family members are highly conserved across species in sequence and function,including nine mature let-7 miRNAs in the human.Studies have shown that let-7 miRNAs were involved in the occurrence and development of multiple tumors.miR-let-7c-5p as a member of the let-7 family,its clinical significance in gastric cancer and the impact on the development of gastric cancer is not clear.MTDH(Metadherin)was also named AEG-1(Astrocyte Elevated Gene-1),located in chromosome 8q22.MTDH was first identified in primary human fetal astrocytes exposed to HIV-1 in 2002.MTDH is highly expressed in a variety of tumors and functions as an oncogene to regulate tumor progression,angiogenesis,metastasis,invasion and chemotherapy resistance.MTDH can be used as an independent prognostic indicator of various cancers,which is of great significance in judging the clinical prognosis of cancers.The epithelial-mesenchymal transition(EMT)was proposed by Greenburg and Hay early in 1982.EMT is a complex process,which promotes invasion and migration of cancer cell through allowing cells to transit from epithelial to mesenchymal phenotype.Epithelial biomarkers include E-cadherin and so on,mesenchymal cell biomarkers include N-cadherin,vimentin and so on.Objective:We will investigate the expression of miR-let-7c-5p in gastric cancer and analyze the correlation between miR-let-7c-5p expression and clinicopathological datas.Moreover,we will observe the effect of miR-let-7c-5p on the function of gastric cancer cells and research the molecular mechanism of MTDH and EMT involved in miR-let-7c-5p regulating the development of gastric cancer.Methods:1.The expression of miR-let-7c-5p in gastric cancer tissues and cells was determined by real-time PCR,and the pathological features were analyzed.2.Up-regulated and down-regulated miR-let-7c-5p cells were constructed by lentiviral transfection.The invasion and metastasis of gastric cancer cells were observed by Wound-healing assay and Transwell invasion and migration experiments.3.Western blot was used to detect the expression of EMT-related markers in gastric cancer cells.4.Double-luciferase reporter assay was used to detect binding sites of miR-let-7c-5p and MTDH-3'UTR.5.Restore experiment and Western blot were used to detect the change in expression of EMT-related markers in gastric cancer cells.6.To observe the effect of miR-let-7c-5p on gastric cancer function in vivo.Results:1.MiR-let-7c-5p is down-regulated in gastric cancer tissues and cell lines and downregulation of miR-let-7c-5p is correlated with GC progression.2.MiR-let-7c-5p inhibits gastric cancer cells migration and invasion.3.MiR-let-7c-5p regulates EMT phenotypes in gastric cancer cells.4.MTDH is a direct target of miR-let-7c-5p.5.MTDH is involved in miR-let-7c-5p-mediated EMT progression.6.MiR-let-7c-5p suppresses metastases of GC cells in vivo.Conclusion:MiR-let-7c-5p inhibited the migration and invasion of GC cells by targeting MTDH and suppressing EMT... |
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