The Role Of STING On The Progression Of Lung Adenocarcinoma And Its Underlying Mechanism

Background and objective:Lung cancer is one of the most common malignant tumors seriously endangering human health.Non-mall-cell-lung-cancer(NSCLC)is the most important pathological type,including adenocarcinoma and squamous cell carcinoma.Lung adenocarcinoma accounts for about 40% of all lung cancer.Because it is difficult to detect early,most patients are diagnosed at an advanced stage.Lung cancer remains the primary cause of cancer related death,despite the progress of chemotherapy,radiotherapy and the emergence of new therapies.This high mortality is closely related to the continuous proliferation of lung cancer cells.Therefore,understanding the regulation mechanism of lung cancer proliferation are crucial to improve the prognosis of NSCLC patientsInterferon gene stimulator(STING),a 379 amino acids transmembrane-protein anchoring in endoplasmic reticulum(ER),is a new protein found in the natural immune signaling pathway.It's a signalling molecule associated with the endoplasmic reticulum(ER)and is essential for controlling the transcription of numerous host defence genes,including type ? interferons(IFNs)and pro-inflammatory cytokines,following the recognition of aberrant DNA species or cyclic dinucleotides(CDNs)in the cytosol of the cell.STING signalling has now been shown to play an important role in host defense against viral infection.At present,some studies have shown that tumor cells can also express STING and play different roles in the development of tumor.However,the role of STING in tumorigensesis is complicated.Most of the tumor cells show low expression of STING,and the defective STING signaling pathway in tumor may assist immune cecape of tumors.On the contrary,studies have shown that tumor cells can promote the growth and metastasis of tumors by overexpressing STING,and STING play an important role in promoting tumor growth in these tumors.Therefore,STING may be a two-way regulatory factor.The expression of STING in lung cancer and its clinical significance are not clear.In the current study,we first explored STING expression in lung adenocarcinoma,and dectected its relationship with clinicopathology and prognosis.In addition,the effect of abnormal expression of STING on the proliferation of lung adenocarcinoma cells was investigated in vitro,and the possible molecular mechanisms were explored.Finally,the aim of this study was to provide a theoretical basis for the pathogenesis of lung adenocarcinoma and the development of new drug targets.Methods:1.Clarify the expression of STING in lung adenocarcinoma and its relationship with clinicopathological features and prognosis.Thiry cases of lung adenocarcinoma were collected and total RNA and protein were extracted.The mRNA and protein expression levels of STING in lung adenocarcinoma and paired normal lung tissues were detected by qRT-PCR and Western blot,and the difference between the two groups was compared.Tissue microarrays(TMA),including 90 cases of lung adenocarcinoma and para cancerous tissue,was used to detect the expression of STING by immunohistochemistry(IHC)).According to the IHC score of STING,the relationship between STING expression and clinicopathological data(i.e.,tumor size,lymph node metastasis,pathological type,TNM staging,etc.)was analyzed.We further explored the association between STING protein and the prognosis of patients with lung adenocarcinoma using Kaplan–Meier survival analysis.2.Explore the biological function and mechanism of STING in lung adenocarcinomaThe common lung adenocarcinoma cell lines were cultured.The expression of STING was detected by qRT-PCR and Western blot.The lung cancer cell lines with high expression and low expression of STING were screened.Through interference and overexpression of STING,the effects of abnormal expression of STING on cell proliferation and metastasis were detected by MTT,flat clones and Transwell methods.The effects of knockdown and over expression of STING on apoptosis were detected by flow cytometry.Finally,the possible mechanism of STING expression on the biological function of lung adenocarcinoma cells was explored.Results:1.STING overexpression in primary lung adenocarcinoma tissues and the relationship with clinicopathological characteristics and prognosis of lung adenocarcinoma patients.Real-time PCR,Western blot and tissue microarray(TMA)were used to detect the STING expression of mRNA and protein in cancer tissues.The results showed that the expression of STING in lung adenocarcinoma tissue was significantly higher than adjacent normal lung tissues.Moreover,the expression of STING was significantly correlated with tumor size and TNM stages.Survival analysis indicated that the 5 years overall survival time of patients with high expression of STING was significantly lower than that of STING low expression group.2.Explore the biological role and potential mechanism of STING in lung adenocarcinoma cellsThe results indicated that STING showed high expression in the three lung adenocarcinoma cell lines(H1975,H1650,H1299).STING was knocked down by siRNA in H1975 and H1299 cell lines,and STING was overexpressed in the A549 cell line by lentivirus infection.The results showed that the abnormal expression of STING can significantly affect the growth and proliferation of lung adenocarcinoma cells.The invasion and metastasis capacity of the adenocarcinoma cells had no effect.High expression of STING may affect the growth and proliferation of lung adenocarcinoma cells by regulating the NF-?B pathway.Conclusion:This study showed for the first time that STING was highly expressed in lung adenocarcinoma and was closely related to tumor size and TNM stage.STING expression level could be used as an independent predictor of prognosis in patients with lung adenocarcinoma,and high expression indicates poor prognosis.STING may affect the proliferation of lung adenocarcinoma cells by regulating the NF-?b pathway.The abnormal expression of STING has no effect on the metastasis and invasion of lung adenocarcinoma cells.