Characteristics Of PD-L1 Expression In Tumor Cells And Tumor Microenvironment Of DLBCL With MYD88 L265P Mutation

Objective:To explore the effect of MYD88 L265P mutation on the expression of PD-L1 in tumor cells and tumor microenvironment in diffuse large B-cell lymphoma(DLBCL),and analyze the influence of relevant factors on the prognosis of DLBCL,and explore the cutoff value of PD-L1 expression in DLBCL tumor cells and tumor microenvironment,to provide a theoretical basis for immunotherapy and prognosis judgment.Methods:The first part:the Ventana automatic immunohistochemical platform was used to detect PD-L1(22C3)and PD-L1(SP142)in 261 DLBCL samples,survival analysis was performed on 138 patients with complete clinical and follow-up data,and the relationship between PD-L1 expression level and various clinicopathological factors was analyzed.The second part:Multiplex ligation-dependent probe amplification(MLPA)and FISH were used to detect the frequency of MYD88 L265P mutation and related gene abnormalities in 72 cases of DLBCL.To observe the expression of PD-L1 in tumor cells and tumor microenvironment,and to analyze the relationship between MYD88 L265P mutation and the expression of PD-L1 in DLBCL tumor cells and tumor microenvironment.Results:The first part:1.The expressions of PD-L1(22C3)in tumor cells and PD-L1(SP142)in the tumor microenvironment were detected in 261 cases of DLBCL,and the results showed that 84 cases(32.18%)of tumor cells were positive for PD-L1(22C3),and 177 cases(67.82%)were negative.172 cases(65.90%)were positive for PD-L1(SP142)in the tumor microenvironment,and 89 cases(34.10%)were negative.2.Among the 138 samples with complete 5-year follow-up data,88 patients(63.77%)were survived and 50 patients(36.23%)were died;the positive rate of PD-L1(22C3)in tumor cells in the survival group(21.29%)was significantly lower the positive rate in the death group(42.00%)(P=0.0184);the positive rate of PD-L1(SP142)in tumor microenvironment in the survival group(69.32%)was higher than that in the death group(54.00%),but no statistical difference(P=0.0970);the five-year survival rate(27.27%)of PD-L1(22C3)positive in tumor cells and PD-L1(SP142)negative in tumor microenvironment was significantly higher than that(76.27%)of PD-L1(22C3)negative in tumor cells and PD-L1(SP142)positive in tumor microenvironment(P=0.0028);PD-L1(22C3)positive in tumor cells and PD-L1(SP142)negative in tumor microenvironment suggest a poor prognosis of DLBCL(P=0.0359;P=0.0774).3.The analysis of 138 samples with complete 5-year follow-up by X-tile software showed that the cutoff value of PD-L1(22C3)positive expression in tumor cells was>2%(P=0.0207);The cutoff value of PD-L1(SP142)positive expression in tumor microenvironment was>1%(P=0.5950).The second part:Of the 72 DLBCL with genetic results,MYD88L265P mutation was detected in 15(20.8%)cases.Nine cases with JAK2 amplification were excluded,and the remaining 63 cases of DLBCL were divided into MYD88L265P mutant group(n=14)and MYD88L265P wild-type group(n=49).The positive rate(50%)of PD-L1(22C3)in tumor cells of the MYD88L265P mutant group was significantly higher than that in the MYD88L265P wild-type group(18.4%)(P=0.017);The positive rate(28.6%)of PD-L1(SP142)in the tumor microenvironment of the MYD88L265P mutant group was significantly lower than that of the MYD88L265P wild-type group(77.6%)(P=0.001);the frequency of the "starry sky phenomenon" in the MYD88L265P mutant group(78.6%)was significantly higher than that in the MYD88L265P wild-type group(12.2%)(P<0.0001);MYD88L265P mutation was not associated with patient age,gender,tumor site,Ann Arbor stage,IPI score,bone marrow involvement and Han’s classification;Survival analysis showed that MYD88L265P mutation and "starry sky phenomenon" were poor prognostic factors in DLBCL(P=0.0285;P=0.0445).Conclusion:The expression level of PD-L1 in DLBCL tumor cells and tumor microenvironment is related to the prognosis of patients;MYD88 L265P mutation may play a role in the regulation of PD-L1 expression in DLBCL tumor cells and tumor microenvironment.