Prognostic Significance of Tumor Infiltrating Lymphocytes (TILs) and Programmed Cell Death-Ligand 1 (PD-L1) in Nasopharyngeal Carcinoma

Abstract

Purpose/Objective(s)The role of PD-L1 and different subtypes of TILs in nasopharyngeal carcinoma (NPC) are till poorly studied. The purpose of this study is to evaluate the prognostic significance of TILs and immune checkpoint protein expression in NPC.Materials/MethodsA total of 125 NPC patients consisting of 68 patients with favorable prognosis (Group 1) and 57 patients with unfavorable prognosis (Group 2) treated between 2010 to 2014 were included. Archival tumor tissues of selected patients were retrieved and a tissue microarray (TMA) was conducted. The TMA was stained with CD3, CD4, CD8, Foxp3, CK, PDL1 and DAPI by using multiplexed quantitative fluorescence. The marker CD3 was used to defined T cells, subtypes of T cells were defined by the combination of different markers: cytotoxic T lymphocytes (CTLs, CD3+CD8+), CD4+ effector T cells (CD4+ Teff, CD3+CD4+Foxp3-), regulatory T cells (Treg, CD3+CD4+Foxp3+). The counts and densities of every marker and labelled cells were calculated. High density was defined as higher than the median value for each marker. The density differences and association with survival of PD-L1 and TILs were analyzed between two groups.ResultsPD-L1 positive tumor cells (TCs-PDL1) were observed in 96% of patients and PD-L1 positive immune cells (ICs-PDL1) were observed in 90.4% of patients. ICs-PDL1 were significantly correlated with high infiltration of CD3+ TILs, CD4+ Teff, CTLs, and Treg. Patients with high PDL1+ Treg had unfavorable overall survival (OS, HR 2.093, 95% CI 1.038-4.222, P = 0.035) and progression-free survival (PFS, HR 2.501, 95% CI 1.421-4.403, P = 0.001). High TCs-PDL1 expression was associated with a trend approaching significance for improved OS (P = 0.055) and PFS (P = 0.078). High density of Treg, Treg/CTL ratio and Treg/CD4+ Teff ratio were significantly associated with poor survival of PFS (P = 0.027, P = 0.001 and P = 0.004 respectively). Patients with lower Treg/CTL ratio presented better OS, but did not reach statistical significance (P = 0.082).ConclusionHigher density of Treg, Treg/ CTL and Treg/CD4+ Teff ratio were associated with worse survival of NPC which may contribute to the formation of immunosuppressive microenvironment. The role of PD-L1 and different subtypes of TILs in nasopharyngeal carcinoma (NPC) are till poorly studied. The purpose of this study is to evaluate the prognostic significance of TILs and immune checkpoint protein expression in NPC. A total of 125 NPC patients consisting of 68 patients with favorable prognosis (Group 1) and 57 patients with unfavorable prognosis (Group 2) treated between 2010 to 2014 were included. Archival tumor tissues of selected patients were retrieved and a tissue microarray (TMA) was conducted. The TMA was stained with CD3, CD4, CD8, Foxp3, CK, PDL1 and DAPI by using multiplexed quantitative fluorescence. The marker CD3 was used to defined T cells, subtypes of T cells were defined by the combination of different markers: cytotoxic T lymphocytes (CTLs, CD3+CD8+), CD4+ effector T cells (CD4+ Teff, CD3+CD4+Foxp3-), regulatory T cells (Treg, CD3+CD4+Foxp3+). The counts and densities of every marker and labelled cells were calculated. High density was defined as higher than the median value for each marker. The density differences and association with survival of PD-L1 and TILs were analyzed between two groups. PD-L1 positive tumor cells (TCs-PDL1) were observed in 96% of patients and PD-L1 positive immune cells (ICs-PDL1) were observed in 90.4% of patients. ICs-PDL1 were significantly correlated with high infiltration of CD3+ TILs, CD4+ Teff, CTLs, and Treg. Patients with high PDL1+ Treg had unfavorable overall survival (OS, HR 2.093, 95% CI 1.038-4.222, P = 0.035) and progression-free survival (PFS, HR 2.501, 95% CI 1.421-4.403, P = 0.001). High TCs-PDL1 expression was associated with a trend approaching significance for improved OS (P = 0.055) and PFS (P = 0.078). High density of Treg, Treg/CTL ratio and Treg/CD4+ Teff ratio were significantly associated with poor survival of PFS (P = 0.027, P = 0.001 and P = 0.004 respectively). Patients with lower Treg/CTL ratio presented better OS, but did not reach statistical significance (P = 0.082). Higher density of Treg, Treg/ CTL and Treg/CD4+ Teff ratio were associated with worse survival of NPC which may contribute to the formation of immunosuppressive microenvironment.