Study Of Immune Checkpoint Molecules In Diffuse Large B-cell Lymphoma

Background: Diffuse large B-cell lymphoma(DLBCL)is an aggressive non-Hodgkin's lymphoma,which manifests a worser clinical course when combined with pathogenic Epstein-Barr virus(EBV)infection.B7-H4 and B7-H1,members of the B7 family,are negative costimulatory molecules of immune checkpoint that regulate T cell anti-tumor effects.Nevertheless,the roles and their mechanisms of biomarkers,such as B7-H4 and Programmed death receptor 1(PD-1)/ Programmed death ligand 1(PD-L1;B7-H1),in diffuse large B-cell lymphoma remain unclear.Objective: To explored the relationship between the expression of immune checkpoint molecules,B7-H4 and B7-H1(PD-L1),in tumor tissues of EBV-positive diffuse large B-cell lymphoma(EBV+DLBCL)and gene mutation of PD-1 in diffuse large B-cell lymphoma and pathogenic mechanisms of apoptosis,invasion and prognosis of tumor.Medthods: The clinical features of patients with diffuse large B-cell lymphoma in our hospital were retrospectively analyzed.The apoptosis and invasion of diffuse large B-cell lymphoma cell lines were detected.The expression of EBER,B7-H4 and B7-H1 was examined by immunohistochemistry.Proteins and signaling pathways involved in apoptosis were identified by Western blots.The mutations in SNP loci of PD-1 and expression of micro RNAs were checked by sequencing and real-time PCR.Results: Overall survival rates and progression free survival rates were significantly lower in EBV+DLBCL patiens than in EBV-DLBCL patiens and the proportion of overexpressed B7-H4 was significantly increased in EBV+DLBCL cohort.Consistently,the transformation of DLBCL cell line(Pfeiffer)by EBV increased the expression of B7-H4.B7-H4 promoted cell viability by inhibiting apoptosis in EBV transformed DLBCL cell line(Pfeiffer)via Erk1/2 and Akt pathway.In addition,the expression levels of B7-H4 and B7-H1 in tumor tissues of EBV+DLBCL were negatively correlated.And tumor cell invasion assay confirmed that DLBCL cell lines highly expressing B7-H1 had strong invasive ability.The most mutation type of B7-H1 receptor(PD-1)in DLBCL is single nucleotide polymorphism(SNP).The six SNP loci of B7-H1 receptor(PD-1)in our study are closely related to each other and are associated with CD10,Mum-1,Ki-67,hypertension,liver dysfunction,and clinical stage I-IV staging.The expression of mi R-101-3p and mi R-15b-5p in the peripheral blood of patients with DLBCL are positively correlated and increase in the poor clinical prognosis cohort.Conclusion: Our study demonstrates that B7-H4 is highly expressed in EBV+DLBCL which showed a more aggressive clinical course than EBV?DLBCL.B7-H4 inhibits apoptosis in EBV transformed DLBCL cell line via Erk1/2 and Akt pathway.The expression of B7-H4 and B7-H1 examined in tumor specimens of EB virus-positive diffuse large B-cell lymphoma are mutually exclusive.The dominant factor of EBV+DLBCL progression is usually B7-H1 expression which enhances tumor invasion.However,B7-H4 may become the dominant factor of EBV+DLBCL progression which inhibits tumor cells apoptosis when the expression of B7-H1 is reduced.The six SNP loci of B7-H1 receptor(PD-1),mi R-101-3p and mi R-15b-5p may hanve some effects on the prognosis of diffuse large B-cell lymphoma.