A Preliminary Study About The Expression And Function Of LARP7 In Lung Cancer Cell

In the global top 10 malignant tumors,the incidence and mortality of lung cancer is the highest.Lung cancer is the most common cancer in China,with both incidence and mortality topping any other country in the world.Previous studies have shown that LARP7 plays an important role in gastric cancer,breast cancer,cardiac hypertrophy and other diseases.LARP7 plays an important role in the process and development of tumor through regulating P-TEFb and telomerase activity,which in turn affects transcription in tumorgenesis.In this project,the lung cancer cell line A549 and the A549-based LARP7-knockout cell line were used as the research platform.A series of different commonly used biochemical methods,such as Western blot,PCR,plasmid constructing,gene editing and mass spectrometry were adopted to study the function and mechanism of LARP7 in Lung cancer cell tumorgenesis.The main experiments are as follow:(1)Overexpressing LARP7 in lung cancer cell A549 inhibited the growth and proliferation rate of cells.The wound-healing results showed that the migration ability of cells was inhibited.Overexpression of LARP7 also resulted in a decrease invasion ability of cells in transwell experiments.Meanwhile,many markers of EMT were up-regulated and down-regulated.(2)We used gene editing technology CRISPR/Cas9 to knockout LARP7 in A549 cells.The LARP7-KO cells became narrow and synaptic,which is consistent with the characteristics of cell movement and transfer ability enhancement.At the same time,the growth and proliferation of cells as well as the migration and invasion ability enhanced significantly after the depletion of LARP7.Many markers of EMT were up-regulated and down-regulated respectively.(3)The effect of knocking-out LARP7 on transcription was also investigated.We found that the phosphorylation of serine 2 on RNA polymerase ?CTD increased,which very likely promotes transcription elongation.(4)In addition,the mass spectrometry-based proteomics studies showed that the 7SK snRNP complex was disrupted after LARP7-KO,leading to the release of P-TEFb which was further transferred to the super elongation complex(SEC)to promote gene transcription.Also,WB was used to confirm some of the quantitative MS results.We found that in KO cells the NF-?B reduced,Akt phosphorylation increased,p53 expressed at an abnormally high level,indicating the observed cell metastatic features in KO cells might probably regulated through the NF-?B and Akt signaling pathways.To sum up,we found that LARP7 is an important suppressor in lung cancer cells.It affects the migration and invasion ability of lung cancer cell by regulat:ing transcription elongation process and some relevant factors of signal transduction pathways.