| Background:Gastric cancer (GC) is the third most common cancer in the world, and GC is also the third most common cause of death from cancer in China. Gastric cancer is a serious threat to human life and health. In contrast to normal differentiated cells that depend on aerobicoxidation for energy production, cancer cells use aerobic glycolysis as the main source (Warburg’s effect).The M2 splice isoform of pyruvate kinase(PKM2) is a key regulator of aerobic glycolysis as an enzyme that catalyzes the later step of glycolysis. As the four known isoforms of pyruvate kinase, as PKL and PKR are encode by PKLR gene, PKM1 and PKM2 derive from an alternative splicing of the same PKM2 gene. PKM1 is expressed in the skeletalmuscle and brain; In addition to embryonic cells and adults stem cells, PKM2 is also a major isoform expressed in cancer cells. PKM2 exists as either a low-activity dimeric or high activity tetrameric form, normal proliferating cells express the high-activity tetrameric form whereas cancer cells predominantly express the low-activity dimeric form of PKM2, it can cut off the glycolytic pathway in the upsteam of pyruvate, assemble the intermediate and promotes the synthesis biological macromolecule, beneficial to tumor growth and angiogenesis.MiR-let-7a was detected early and which was first identified in C.elegans as a heterochronic gene. Let-7a regualtes the cell proliferation and apoptosis in mammals and also plays a key role in cell cycle regulation. MiR-let-7a act as tumor suppressors in many cancers include gastric cancer. We start our study from let-7a, analyze the potential mechanisms between let-7a and PKM2, investigate the biological mechanisms of let-7a/PKM2 pathway invoved in the proliferation in gastric cancer.Objective:In this study, we will investigate the let-7a and PKM2 expression levels in gastric cancer tissues and cells, analyze the correlation between them. We will focuses on discussing let-7a inhibit cell proliferation, migration, and invasion by down-regulating PKM2 in gastric cancer, investigates the role of let-7a/PKM2 pathway plays in the growth of gastric cancer. The study will help us expicit the effect of let-7a/PKM2 pathway in gastric cancer, may provide new ideas for gastric cancer molecular therapy in the future.Methods:1. Real time PCR was used to detect the expression of let-7a and PKM2 in gastric cancer cancer tissues and cells, and analysis the pathologic characteristics.2. Let-7a up-regulated and down-regulated cell model was established by a lentivirus system.3. Real time PCR was used to detect the expression of c-Myc, hnRNPAl and PKM2 after the transfection of PKM2. Observe the proliferation, migration and invasion of gastric cancer cells.4. PKM2 up-regulated and down-regulated cell model was established by a lentivirus system.5. Real time PCR was used to detect the expression of let-7a, c-Myc and hnRNPAl after the transfection of PKM2. Observe the proliferation, migration and invasion of gastric cancer cells.6. Verify the inhibition of let-7a/PKM2 on the proliferation, migration and invasion of gastric cancers by the nude mouse transplantation tumor experiment.Results:1. miR-let-7a expression is negatively correlated with the PKM2 levels in both gastric cancer tissues and cell lines;2. miR-let-7a interfere the expression of c-Myc/hnRNPAl/PKM2 in gastric cancer cells;3. miR-let-7a inhibit cellular proliferation, migration and invasion;4. PKM2 is involved in the regulation of cell proliferation, migration and invasion by miR-let-7a;5. miR-let-7a suppresses the tumorigenicity in vivo.Conclusion:Let-7a inhibited the proliferation, migration and invasion through reguates the expression of c-Myc and hnRNPAI to downregulated the level of PKM2. |
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