Expression And Prognostic Value Of Tumor-infiltrating Lymphocytes And PD-L1 In Hepatocellular Carcinoma

Backgrounds and Objective HCC is one of the most common malignancies in the world.Surgical resection has always been the preferred and most important treatment for HCC.The outcome of surgical treatment is strongly related to clinical staging.In the early stages,patients who undergo radical resection of liver cancer have a 5-year survival rate of about 70 percent.Unfortunately,despite advances in prevention and diagnosis in recent years,the majority of patients at the time of diagnosis are in the middle and late stages,and have lost the opportunity for radical surgical resection,so the prognosis remains poor.Therefore,in addition to early diagnosis,timely treatment based on prediction of patient prognosis can also help prolong survival.Further studies are urgently needed to identify tumor biomarkers with higher sensitivity and specificity in HCC.Through a better understanding of the mechanism of cancer recurrence,new therapeutic targets may be discovered to determine the best treatment regimens and reduce recurrence.Recently,large amounts of data from many tumors have demonstrated that TILs can be used to predict clinical outcomes.In addition,treatments targeting immune checkpoints have been introduced into the clinic to improve the effectiveness of immunotherapy for HCC.Immune checkpoints mainly included PD-1、PD-L1 and CTLA-4.These checkpoints somewhat enhance anti-tumor immunity and enhance the activation of the immune system.Among the available immunosuppressants,PD-1 inhibitors are currently considered to be the most promising.To date,there is no clear evidence that PD-L1 is a predictive immunobiomarker that can help select patients who are more likely to receive treatment or who are more likely to have adverse events.This is an open question for all solid tumors,because earlier studies on the predictive power of PD-L1 have not shown consistency in predicting anti-tumor immune responses.Therefore,it is of great clinical significance to investigate the distribution of TILS and PD-L1 in liver cancer tissues and paracancerous tissues and their influence on prognosis.Objective :(1)To explore the difference in distribution proportion of TILs and PD-L1 in primary hepatocellular carcinoma and its adjacent tissues.(2)To investigate the relationship between the expression of CD8~+T cells and PD-L1 and clinically relevant pathological parameters and prognosis.(3)Verify that CD8~+T cells and PD-L1 may serve as potential biomarkers for the prognosis of HCC patients,and also contribute to the in-depth study of immunotherapy for HCC patients.Methods Liver cancer and paracancerous tissue samples were collected from 72 patients who underwent radical hepatectomy between December 15,2017 and January 9,2019.Flow cytometry was used to detect the distribution of TILs and PD-L1.The experimental data were analyzed by SPSS 22.0 statistical software.The data of continuous variables were expressed by((?) ± s),and the differences between paired samples(liver cancer tissues and paracancerous tissues)were tested by Nonparametric Test.The cut-off values of CD8~+T cell and PD-L1 were determined according to the ROC.The cut-off values are 42.6 and 5.8.According to this cut-off value,CD8~+T cell and PD-L1 were divided into high expression groups and low expression groups.Kaplan-Meier method was used to analyze the survival time of the two groups,and the Log-rank method was used to test the survival rate.Univariate and multivariate Cox regression analysis was used to analyze the independent prognostic factors.The difference was statistically significant(P < 0.05).Results: The distribution proportion of CD3~+T cells in liver cancer tissues was significantly higher than that in paracancerous tissues,the proportion of CD4~+T cells in all CD3~+T cells in liver cancer tissues was significantly higher than that in paracancerous tissues,and the distribution proportion of PD-L1 in liver cancer tissues was significantly higher than that in paracancerous tissues,the differences were statistically significant(t=3.021,8.607,4.209,P <0.001).The proportion of CD8~+T cells in all CD3~+T cells in liver cancer tissues was significantly lower than that in paracancerous tissues,the difference was statistically significant(t =7.052,P<0.001).The ratio of CD4~+T cells to CD8~+T cells in liver cancer tissues was significantly higher than that in adjacent tissues,the differences were statistically significant(t=4.209,P<0.001).The distribution proportion of CD8~+T cells in liver cancer tissues was statistically different in tumor diameter(P=0.002)and TNM stage(P=0.015).The expression of PD-L1 in liver cancer tissues was statistically different in tumor stages(P=0.029).Univariate analysis showed that the degree of tumor differentiation(P<0.001),TNM stage(P=0.001),CD8~+T cells(P=0.001)and PD-L1 expression(P=0.021)were correlated with disease-free survival(DFS).Multivariate Cox regression analysis showed that the degree of tumor differentiation(P<0.001),the expression of CD8~+T cells(P=0.013)and PD-L1(P=0.039)were independent influencing factors of postoperative DFS.Kaplan-Meier survival curve analysis showed that DFS in the high expression group of CD8~+T cells was significantly higher than that in the low expression group,and DFS in the low expression group of PD-L1 was significantly higher than that in the high expression group(all P <0.05).Conclusion:1.The functional subsets of TILs and the distribution proportion of PD-L1 in liver cancer tissues were changed compared with those in adjacent tissues,resulting in the abnormal number of TILs and changing the local immune microenvironment of tissues.2.The expression of CD8~+T cells in liver cancer tissues is related to tumor size and stage,which further proves that TILS infiltration is an important factor in the occurrence of tumor immunosuppression.It also suggested that low immunity was one of the important factors for tumor growth,recurrence and metastasis.The high expression of CD8~+T cells was an independent factor affecting the postoperative prognosis of liver cancer patients,and the DFS of the group with high expression of CD8~+T cells was significantly higher than that of the group with low expression.3.The expression of PD-L1 in HCC tissue is related to the clinical stage of the patients,and PD-L1 is an independent influencing factor for the postoperative prognosis of HCC patients.The DFS of the group with high PD-L1 expression is significantly lower than that of the group with low PD-L1 expression,PD-L1 may also be used as a prognostic biomarker for HCC.