| Summary: | 碩士 === 國立陽明大學 === 解剖學及細胞生物學研究所 === 99 === Gastric carcinoma is one of the most common malignancy cancers worldwide, and ranks as the sixth-highest cause of cancer-related deaths in Taiwan. To date, the regulatory mechanism of its aggressiveness in gastric cancer has not been clearly characterized. MicroRNAs (miRNAs) are small non-coding RNAs that regulate the expression of target genes by transcriptional inhibition or translational repression. Increasing evidence implicates that miRNAs may exhibit as an oncogene or tumor suppressor to modulate gastric tumorigenesis. Previously, it had been demonstrated that activation of Notch2 pathway promotes gastric cancer progression. Based on the results of miRNA microarray screening, we found that miR-301a was significantly down-regulated by activation of Notch pathway in human stomach adenocarcinoma SC-M1 cells. Due to the Notch pathway and miRNAs may function as an oncogene or tumor suppressor, herein, we sought to address whether miR-301a is involved in gastric cancer progression. Using miRNA real-time PCR, miR-301a was indeed down-regulated by the forced expression of activated Notch2 receptor (N2IC) in SC-M1 cells. To study whether miR-310a is involved in the tumorigenesis of human gastric cancer, the recombinant adenovirus expressing miR-301a was established. Colony-forming ability, cell proliferation, migration and invasion were also inhibited by miR-301a in SC-M1 and AZ521 cells. Furthermore, miR-301a suppressed the colony-forming ability, migration and invasion abilities enhanced by Notch2 pathway in SC-M1 cells. Additionally, miR-301a induced morphological change and affected Epithelial-mesenchymal transition (EMT) marker expressions, including E-cadherin, r-catenin, and N-cadherin in SC-M1 and AZ521 cells. Using an in silico search, we found that there are putative miR-301a-binding sites in 3’untranslated region (3’UTR) of CDK2, cyclin D1 and E2F1 mRNAs. Expressions of CDK2, cyclin D1 and E2F1 were inhibited by miR-301a in gastric cancer cells. Interestingly, N2IC and cyclin D1 expressions were inversely correlated with miR-301a expression. Furthermore, miR-301a inhibits activities of luciferase reporter genes containing 3’UTR of cyclin D1 and E2F1 mRNA. Taken together, these results suggest that miR-301a suppresses the tumorigenesis of gastric cancer.
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