The Expression And Analysis Of PD-L1 In Peripheral Blood Circulating Tumor Cells Of Lung Cancer

Objective:Recurrence and metastasis of lung cancer after treatment is the main cause of death,CTC（circulating tumor cells）has been considered to be the most direct factor leading to the recurrence and metastasis of malignant tumors,and its number and the type of epithelial-mesenchymal transition（EMT）are closely related to the prognosis.PD-L1 is an important intervention target for non-small cell lung cancer（NSCLC）immunotherapy,however,it’s clinical significance and biological function in CTC of NSCLC need to be explored in depth。The purpose of this study was to enrich,identify and analyze CTC in the peripheral blood of NSCLC patients,and to detect the different types of EMT and PD-L1 expression levels based on them,and to explore the correlation with the clinicopathological characteristics and treatment efficacy of the patients.Method:In this study,Canpatrol^?CTC typing detection technology was used to collect 271 NSCLC patients from December 2015 to October2019 based on membrane filtration,multiple m RNA in situ hybridization technology was used to identify CTC and used RNA probe detects the expression of PD-L1 gene on CTC.Clinical data including histopathological type,smoking,smoking index,tumor location,tumor size,degree of differentiation,TNM stage,distant metastasis,tumor marker test results,blood routine test results,adjuvant treatment methods,and RECIST efficacy evaluation results were collected.Correlation analysis between CTC count,different molecular types and PD-L1 gene expression and clinical indicators.Result:Among 271 NSCLC patients,261 patients tested positive for CTC（96.31%）,and a total of 5308 CTC were detected.Phenotypic analysis found that patients with CTC showed obvious phenotypic differences in epithelial,mixed and mesenchymal types.Among them,there were 925 epithelial CTC（17.43%）,1139 mesenchymal CTC（21.45%）,and 3244 mixed CTC（61.12%）.The difference in the number of CTC among the three subtypes was statistically significant（P<0.001）.In the studies related to clinicopathological characteristics of patients,univariate analysis results showed that there were significant differences in histological types,smoking index,tumor location,T stage,M stage,clinical stage,distant metastasis and the number of CTC.NSE and neutrophilic results correlate with the total number of CTC,epithelial type and mixed type CTC,but the two factors are not correlated in mesenchymal type.Regression analysis of all factors that affect the expression of PD-L1 in CTC found that smoking index,pathological diagnosis and clinical stage are independent factors that affect PD-L1 expression.Analyze the expression of PD-L1 in different types of CTC under different pathological parameters,among them,the expression level in mixed type is statistically different from different clinical stages（I,II,III,IV）（P=0.040）.First-line chemotherapy and targeted therapy can affect the number of CTC in patients.However,there was no significant difference in the expression level of PD-L1 in CTC before and after treatment with different treatment methods.Conclusion:The Canpatrol^?CTC typing detection technology used in this study not only achieves the separation of peripheral blood CTC from NSCLC patients,but also enables simultaneous EMT typing.In addition,Canpatrol^?CTC typing detection technology can also detect the expression level of PD-L1 on CTC.The detection of CTC and its PD-L1 expression levels in peripheral blood is helpful for the auxiliary diagnosis of patients with NSCLC.The expression of CTC and its PD-L1 are affected by a variety of factors in vivo and in vitro,more clinical application significance of CTC remains to be explored.