Research On The Mechanism Of Cathepsin A Affecting The Development Of Lung Adenocarcinoma

Objective:Lung cancer has the highest morbidity and mortality among all types of cancer,and is the leading cause of tumor death.The most common histological subtype is adenocarcinoma.Despite advances in the diagnosis and treatment of lung cancer in recent decades,survival rates have not improved significantly.Lung metastasis is the leading cause of death of lung adenocarcinoma(LUAD).Therefore,further research is urgently needed to reveal the molecular mechanisms affecting LUAD metastasis to identify potential cancer therapeutic targets.Cathepsin is a key acid hydrolase in lysosomes and a major effector of protein catabolism and autophagy.Studies have shown that the abnormal expression of members of the cathepsin family is related to a variety of tumors,which play an important role in the development and treatment of tumors.In multisystem tumors,the abnormally high expression of members of the cathepsin family is related to the proliferation,invasion and metastasis of tumor cells,and has guiding significance for patients with poor prognosis.Cathepsin A(CTSA)is a serine protease member of the cathepsin family.It is a lysosomal protease with carboxypeptidase,deaminase,and esterase activities.It also has the function of regulating biologically active peptides.Abnormally high expression in cancer.However,the role of CTSA in LUAD is unclear.This article aims to investigate the effects of CTSA on the occurrence and development of LUAD,the molecular regulatory mechanisms that may be involved,and the exploration of biological functions.Methods: The Cancer Genome Atlas(TCGA)database was used to obtain m RNA data sets of 515 cases of lung adenocarcinoma and 59 cases of normal lung tissue.The data were integrated to extract the CTSA gene expression profile,and CTSA in LUAD and normal lung tissue samples were analyzed m RNA expression differences.In order to explore the effect of CTSA on the biological function of LUAD cells,CTSA si RNA was used to transiently transfect A549 cells,while NC si RNA was used to transfect A549 cells as a control group.Transfection efficiency of CTSA m RNA and protein levels were verified by q RT-PCR and Western blot,respectively.CCK8 cell proliferation experiments,flow cytometry,cell scratching experiments,and Transwell invasion experiments were performed on A549 cells and control cells that silenced CTSA to determine the proliferation,invasion,migration ability,and cell cycle changes of A549 cells after transfection.Western blot detection of cell cycle and epithelial-mesenchymal transition(EMT)key protein expression levels.Results: The results of TCGA database download analysis showed that CTSA m RNA expression in LUAD tissues increased significantly compared with normal lung tissues(P <0.001).Transiently transfecting A549 cells with CTSA si RNA,CTSA m RNA and protein levels were significantly down-regulated(P <0.01,P <0.01).CCK8 cell proliferation assay was used to detect the effect of silent CTSA on the proliferation ability of A549 cells.The results showed that the proliferation ability of the A549 cells with silent CTSA was significantly reduced compared with the negative control(P<0.01).Cell cycle distribution was analyzed by flow cytometry.The results showed that the number of cells in the G0 / G1 phase of the silent CTSAA549 cell group increased(P<0.05)and the number of cells in the S phase decreased(P <0.05),compared with the negative control group.Western blot was used to detect changes in cell proliferation and cell cycle-related protein expression levels.The results showed that in the silent CTSA A549 cells the expression of Proliferating Cell Nuclear Antigen(PCNA)was reduced(P <0.05)and the expression levels of p53 and p21 was increased(P <0.05,P <0.05)compared with the negative control.The effect of silent CTSA on the migration ability of A549 cells was tested by cell scratch test.The results showed that the migration capacity of the silent CTSAA549 cells was significantly reduced compared with the negative control(P <0.01).The effect of silent CTSA on the invasion ability of A549 cells was tested by Transwell cell invasion experiment.The results showed that the invasion ability of the A549 cells with silent CTSA was significantly reduced compared with the negative control(P <0.01).The expression of key proteins involved in epithelial-mesenchymal transition(EMT)was detected by Western blot.The results showed that compared with the negative control group,the expression level of E-cadherin in the silenced CTSAA549 cell group increased(P <0.001),and the expression levels of N-cadherin(P <0.05)andβ-catenin(P <0.01)decreased.Conclusion: CTSA was abnormally highly expressed in LUAD.Silencing CTSA inhibits the proliferation,migration,and invasion of A549 cells,blocking the cell cycle at the G0/ G1 phase.Affect the expression of key EMT proteins and cell cycle related proteins.This study revealed for the first time that CTSA may be a tumor promoter of LUAD,and enhance the malignant progress of LUAD by promoting tumor cell proliferation,migration and invasion.Our data indicate that CTSA is expected to become a new target for LUAD and participate in guiding the treatment of LUAD.