The Significance Of PD-L1 Molecule In The Diagnosis And Treatment Of Non-Hodgkin's Lymphoma

Background and PurposeNon-Hodgkin lymphoma is a malignancy involving various lymphatic tissues.The PD-1/PD-L1 signaling pathway plays an important role in the immune evasion mechanism of tumors.Elevated levels of soluble PD-L1 in peripheral blood was observed in patients with many malignant tumors,which of significance in the assessment of prognosis,although relevant research in NHL is limited and yet the application value remains controversial.Chidamide and lenalidomide are two novel drugs for NHL therapy with undetermined mechanism,so the necessity of studying their impact on PD-1/PD-L1 signaling pathway,or the potential synergistic effects with PD-1/PD-L1 inhibitors would be granted.The study consisted of two parts.The first part examined the expression level of sPD-L1 in the peripheral blood in patients with different subtypes of NHL,their correlation with PD-L1 level in tumor microenvironment,and their relationship with the prognostic index and the therapeutic response,to further investigate the clinical value of evaluating the prognosis and therapeutic efficacy,the value of dynamic monitoring the disease,and thevalue of discovering minimal residual disease.In the second part,the effect of chidamide and lenalidomide on PD-L1 was discussed in vitro experiments,seeking the potential mechanism behind the clinical targeted application.MethodsThis study included the newly diagnosed patients at Peking Union Medical College Hospital between May 2016 and May 2017.The level of sPD-L1 in peripheral blood of these patients before treatment and after 4 courses of chemotherapy was examined by ELISA.We compared the differences of sPD-L1 level between the patients and healthy people,and among the subgroups with differents pathological subtypes,different clinical characteristics,and differents treatment responses.We also analysed the change of sPD-L1 level after treatment.The level of PD-L1 in tumor microenvironment was obtained by immunofluorescent double staining of the pathological tissue slides,and its correlation with the level of sPD-L1 in peripheral blood was analysed.PD-L1 high expression cell lines were established by IFN-y induction,and then were treated by chidamide or lenalidomide.Using FACS,qRT-PCR and Western-blot,we tested the PD-L1(+)cell ratio,mRNA and protein level of chidamide or lenalidomide treated cells.Results97 patients with NHL were included in this study.Their sPD-L1 level in peripheral blood was higher than that of healthy people(Median:106.2pg/mL vs.2.910pg/mL,p<0.0001).When cut-off is set as 50.80pg/mL,the sensitivity and specificity were 82.47%and 92.54%respectively.The peripheral blood sPD-L1 level in T-NHL was higher than that in B-NHL.No difference of this level was found between DLBCL(non-GCB)and DLBCL(GCB).There were significant differences of peripheral blood sPD-L1 level in the following subgroups:LDH<250U/L vs.LDH>250U/L,IPI 0-2 vs.IPI 3-5,and EBV+ vs.EBV-.The peripheral blood sPD-L1 level in patients with NHL was positively correlated with the ratio of PD-L1(+)cells in tumor.There was no significant change of peripheral sPD-L1 level after treatment.The PD-L1(+)cell ratio,mRNA and protein level were higher in the experimental cells treated by chidamide than in the cells in control group.The mRNA and protein level were higher in the experimental cells treated by lenalidomide than in the cells in control group,but the the surface PD-L1(+)cell ratio decreased after lenelidomide treatment.ConclusionsThe sPD-L1 level in peripheral blood of patients with NHL was elevated(higher in T-NHL than in B-NHL).The peripheral blood sPD-L1 level in patients with NHL was positively correlated with the ratio of PD-L1(+)cells in tumor,indicating tumor cells are one of the sources of sPD-L1 in peripheral blood.And sPD-L1 level in peripheral blood may be an indicator for tumor burden.Serum LDH level,IPI score,and EBV infection affected sPD-L1 level in peripheral blood.Patients with worse progonosis had higher sPD-L1 level.Both chidamide and lenalidomide up-regulated PD-L1 mRNA and protein level,while chidamide increased surface PD-L1(+)cell ratio but lenalidomide decreased it.