The programmed cell death protein-1/programmed cell death ligand 1 expression, CD3+ T cell infiltration, NY-ESO-1 expression, and microsatellite instability phenotype in primary cutaneous melanoma and mucosal melanoma and their clinical significance and prognostic value: a study of 89 consecutive cases

We evaluated the expression of programmed cell death protein-1 (PD-1), programmed cell death ligand 1 (PD-L1), and NY-ESO-1 antigen; the infiltration of CD3+ T cells; and the microsatellite instability (MSI) phenotype, as well as the relationship of each factor to survival in malignant melanoma patients. Malignant melanoma samples from 89 patients were stained by immunohistochemistry to evaluate PD-1, PD-L1, CD3+ tumor-infiltrating lymphocytes (TILs), NY-ESO-1, and MSI. PD-1 and PD-L1 were expressed in 19.1 and 32.6% of the 89 samples, respectively. There was a significant correlation between PD-1 and PD-L1 expression (r = 0.207, P = 0.046). High infiltration of CD3+ T cells was observed in 41.6% of the samples, and increased cell infiltration was associated with increased PD-1 expression (P = 0.001). NY-ESO-1 antigen was detected in 13.5% of all samples, and the expression of NY-ESO-1 was positively correlated with the expression of PD-1 (P < 0.001). In our research, MSI was detected in 18 samples (20.2%). Survival analysis showed that a high infiltration of CD3+ T cells was related to longer progression-free survival (PFS) [24.0 months, 95% confidence interval (CI): 7.4-40.6 vs. 11.0 months, 95% CI: 7.1-12.9, P = 0.031], similarly, the median overall survival (OS) of the CD3+ T cell high-infiltration patients was also longer (53.0 vs. 38.0 months), but with no statistical significance (P = 0.200). The results for the immune markers mentioned above provide a theoretical basis for the prognosis and immunotherapy selection of malignant melanoma patients.