Prognostic Value of Programed Cell Death-1 Ligand Expression in Colorectal Cancer and Its Correlation with Cytotoxic Tumor-Infiltrating Lymphocytes

Background: colorectal cancer (CRC) is a major cause of cancer-related death worldwide. In recent years, targeting the programed cell death (PD-1)/ programed cell death-1 ligand (PD-L1) immune checkpoint signaling has been tested as a novel promising treatment strategy in several tumors. Aim of the work: the present study aimed to examine expression of PD-L1 and CD 8+ T cells in CRC and to evaluate the relationship between their expressions and the different clinicopathological features. Material and methods: expression of PD-L1 in tumor cells (TC) as well as in tumor infiltrating immune cells (TIMC) was separately evaluated in 85 cases of CRC by the immunohistochemistry, in addition, CD8+ T cell count was assessed. Results: 12.9 % of cases showed PD-L1 expression in TC while, 28.2% showed PD-L1expression in TIMC. PD-L1 expression in TC was significantly associated with higher tumor grade (P =0.001), lymph node metastasis (LNM) (P =0.006) and lymphovascular invasion (LVI) (P > 0.001). On the other hand, PDL-1 expression in TIMC was significantly associated with low tumor grade (P=0.016), negative LVI (P = 0.004), high tumor infiltrating lymphocytes (TILs) count (P <0.0001), as well as high CD8+ T cells count (P = 0.002). High intra CD8-positive T cells was significantly associated with absence of LNM (P =0.013) and negative LVI (P =0.035). Conclusion: these findings indicated that expression of PD-L1 can be used as a new biomarker to predict the prognosis of colon cancer and may provide a clue for immunotherapy in the adjuvant treatment of CRC patients.