| In recent years,the incidence of lung cancer is rising rapidly in the world,which is becoming the leading cause of cancer deaths worldwide.Each year about 1 million and 800 thousand new cases of lung cancer around the world are diagnosed,more than one million people died of lung cancer every year.Lung cancer mortality rose nearly 10 times during the past 40 years.Non-small cell lung cancer(NSCLC)is the most common type of lung cancer,accounting for about 80%of lung cancer.At present,the treatment of NSCLC includes:early surgical treatment,radiotherapy and chemotherapy,targeted therapy,biological therapy,local interventional therapy,and so on.There were no clinical symptoms in patients with early lung cancer,more than 60%of patients with advanced or poor cardiopulmonary function can not be surgery.For those patients who can be treated with radiotherapy and chemotherapy,local interventional therapy and palliative treatment,the 5 year survival rate is low.With the continuous development of medical technology,targeted therapy of lung cancer mutation gene has become a new treatment for lung cancer,but targeted therapies are not always effective,and these patients eventually develop resistance.Therefore,it is of great significance to explore more effective early diagnosis marker for lung cancer.If we can find new tumor markers,early intervention in lung cancer will be employed to prevent its further development,and will eventually decrease the mortality.The etiology and pathogenesis of lung cancer is still not clear.It is believed that the incidence of lung cancer is related to the following factors:1.Smoking:Smoking is an important risk factor for lung cancer,cigarettes contain various carcinogens,including benzo pyrene as carcinogenic as main material.2.Occupational carcinogenic factor:The occupational factors that have been identified in human lung cancer include:Asbestos,including inorganic compounds,chromium and its compounds,incomplete combustion of coal,oil and other polycyclic aromatic hydrocarbons have been recognized as a cause of lung cancer.3.Air pollution:Including indoor environment and outdoor environment.4.Ionizing radiation:High dose ionizing radiation can cause lung cancer.5.Diet and nutrition:Carotene,vitamin A and its derivatives inhibit tumor induced by chemical carcinogens.6.Others:The risk of developing lung cancer in patients with tuberculosis is 8-10 times higher than the normal population.In addition,viral infection,mycotoxins,immune function disorders and family genetic factors on the occurrence of lung cancer may,also play a comprehensive role.7.Heredity and gene change:it is believed that lung cancer may be the result of the interaction between external environmental factors and genetic factors.External factors can induce malignant transformation of cells and irreversible gene alterations,including activation of some oncogenes,inactivation of tumor suppressor genes,and inhibition of apoptosis,leading to uncontrolled cell growth.This process involves multiple genes,pathways,and the involvement of cytokines.The PI3K/AKT signaling pathway plays an important role in the occurrence and development of lung cancer,and it's over activation will promote the proliferation,invasion,metastasis of lung cancer cells.AKT(protein kinase B/PKB)is a serine/threonine protein kinase involved in PI3K/AKT signaling pathway,which is indicated in the regulation of cell proliferation,survival,differentiation,adhesion,movement and other cell functions.AKT can be activated by several transmembrane receptors such as EGFR,After binding to it's ligands,EGFR recuit PI3K to the cell membrane,PI3K phosphorylation of phosphatidylinositol two phosphate on the cell membrane to produce phosphatidylinositol three phosphate,the latter is combined with AKT,promotes the activation of AKT and interacts with a variety of effector proteins to transfer the signal from the cell membrane into the cell.AKT continuous activation is an important prerequisite for promoting cell proliferation and inhibiting cell apoptosis.PI3K/AKT signaling pathway may participate in the occurrence and development of tumor through multiple pathways,including:activation of mTOR,p21cipl,GSK-3,CREB and TSC2 in cancer cell proliferation;The apoptosis of tumor cells was inhibited by Bcl-2 family,apoptosis inhibitory protein,forkhead transcription factor,aspartic acid specific cysteine protease family and so on;Activation of mTOR/p70S6K is involved in the movement,invasion and metastasis of cancer cells.p-AKT is the activated form of AKT,p-AKT was not found in normal tissues,but its expression is significantly increased in non small cell lung cancer,suggesting that the activation of AKT play an important role in the process of cell canceration.However,the molecular mechanism of abnormal activation of AKT in NSCLC is not clear.y-synuclein(also known as breast cancer specific protein)is a molecular marker of breast cancer,has 55.9%and 54.3%homology with the ?-synuclein and(3-synuclein.Recent studies have shown that y-synuclein is also highly expressed in lung cancer,ovarian cancer,bladder cancer,digestive tract cancer and other malignant tumors.The expression was especially significant in the late stage of the tumors.Aberrant methylation of CpG island in the promoter region of y-synuclein is the main cause of abnormal expression of y-synuclein in tumor.Overexpression of ?-synuclein leads to abnormal cell division by inhibiting the function of the important kinase BubRl in mitotic checkpoint,and promotes the occurrence,development,invasion and drug resistance of tumor.The study of the expression of y-synuclein in non-small cell lung cancer tissue and normal lung tissue showed that the positive rate of lung cancer was 46.7%,and the positive rate of normal lung tissue was about 0.However,it's molecular mechanism of tumorigenesis is not fully understood.Some proteins bind to AKT and regulate its kinase activity.For example,in the neuronal cells,?-synuclein binds to AKT and promotes AKT activation,thereby protecting neurons from the toxic effects of rotenone.?-synuclein and ?-synuclein are members of the family of synuclein proteins and have high homology.However,the relationship between y-synuclein and AKT is not clear,and it's role in the development of non-small cell lung cancer need to be further studied.In our study,the expression of ?-synuclein,AKT and p-AKT in non-small cell lung cancer tissues and normal controls were examined.It was found that the expression of y-synuclein and p-AKT in non-small cell lung cancer tissues increased significantly.We found that?-synuclein binds to the kinase domain of AKT and activates AKT.Further experiments showed that y-synuclein enhanced EGF-mediated phosphorylation and activation of AKT,promoted cell proliferation,and inhibited cell apoptosis induced by STR.It is confirmed that ?-synuclein can promotes cell proliferation and survival viaactivating AKT.In conclusion,we investigated the role of y-synuclein and AKT in NSCLC,and illustrated the molecular mechanism of ?-synuclein/AKT pathway in the proliferation and survival of lung cancer cells.Our study layed the experimental basis for the earlydiagnosis and treatment of lung cancer.Part ? Expression and relationship between?-synuclein and AKT in NSCLCObjectiveTo assess the expression of y-synuclein and p-AKT in NSCLC tissues and control tissues,and clarify the relationship between y-synuclein and AKTMethods1.The expression of AKT,p-AKT and y-synuclein in NSCLC tissues and normal tissues were detected by Western blot.2.The relationship between ?-synuclein and AKT in lung cancer tissues detected by Co-immunoprecipitation.3.The relationship between ?-synuclein and the full-length or different fragments of AKT detected by GST pull-down.4.After y-synuclein overexpression,AKT activity detection kit and Western blot were used to detect the changes of AKT phosphorylation and activity.5.After ?-synuclein knock-down,AKT activity detection kit and Western blot were used to detect the changes of AKT phosphorylation and activity.Results1.The expression of p-AKT and y-synuclein in NSCLC group was higher than that of normal control group.The expression of total AKT was not significantly changed compared with normal control tissue.2.y-synuclein binds AKT in NSCLC tissues.3.?-synuclein binds to full-length AKT and the N-terminal aa.1-408 fragment of the AKT but does not bind to aa.1-108 fragment of AKT,indicating ?-synuclein binds to the kinase domain of AKT.4.Overexpression of y-synuclein enhanced AKT phosphorylation and activation.5.Knockdown of y-synuclein decreased AKT phosphorylation and activation.Conclusion1.y-synuclein binds to the kinase domain of AKT.2.y-synuclein promotes AKT phosphorylation and activation.Part ? ?-synuclein promotes NSCLC cell survival and proliferation through activating AKT pathwayObjectiveTo further investigate the molecular mechanisms of y-synuclein in the proliferation and survival of NSCLC by activating AKT.Methods1.The y-synuclein expression of H157 cells was silenced by siRNA,then we examined the changes of EGF-mediated cell proliferation by MTT assays and PCNA expression by Western blot.2.After the overexpression of ?-synuclein in H157 cells,we examined the changes of STR-induced cell apoptosis by MTT assays and caspase-3 expression by Western blot.3.After knockdown of AKT expression,we examined the change of ?-synuclein on cell proliferation by MTT assays.4.After knockdown of AKT expression,we examined the effect of ?-synuclein on cell survival by MTT assays.Results1.?-synuclein deletion decreased the expression of EGF-mediated cell proliferation and proliferation marker PCNA.2.Overexpression of y-synuclein attenuated STR-induced caspase-3 activity anddecreased cell activity.3.AKT deletion abolished the pro-proliferative effect of y-synuclein.4.AKT deletion abolished the protective effect of y-synuclein against staurosporine-induced loss of cell viability.Conclusion1.?-synuclein promotes proliferation and survival of NSCLC.2.?-synuclein promotes proliferation and survival of cancer cells via activating AKT. |
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