PD-L1 expression in colon cancer and its relationship with clinical prognosis

Objectives: PD-L1 is closely associated with tumorigenesis and development. However, expression of PD-L1 protein in colon cancer and its significance in clinical prognosis are yet to be fully clarified. This study examined the relationship between PD-L1 expression with the clinicopathological features and prognosis of colon cancer. Methods: This study collected cases of primary colon cancer that had not undergone preoperative chemotherapy and had complete clinical data. Eighty specimens each were obtained from cancer tissues, paracancer tissues, and normal tissues. Immunohistochemical assays were performed to detect PD-L1 expression. The relationship between PD-L1 expression and clinicopathologic features was compared. This was combined with follow-up data, to analyze the relationship between positive or negative PD-L1 expression and prognosis. Results: Among 80 tumor specimens, 22 cases (27.5%) showed high PD-L1 expression, 24 cases (30.0%) showed moderate expression, and 34 cases (42.5%) showed weak or no PD-L1 staining. High expression of PD-L1 in paracancer and normal tissues were 9 (11.3%) and 5 (6.3%) cases, respectively. PD-L1 expression was also positively correlated with TNM stage (P=0.009), lymph node metastasis (P=0.000), distant metastasis (P=0.014). There were no significant differences in different age, gender, histologic grade, and tumor size groups (P>0.05). Regression analysis revealed that poorer tumor differentiation, later TNM stages, presence of lymph node metastasis, and positive PD-L1 expression were factors that influenced prognosis. Multivariate analysis indicated that late TNM stage and positive PD-L1 expression were independent risk factors that influenced prognosis. Conclusion: PD-L1 expression is significantly elevated in colon cancer tissues, and is closely associated with lymph node metastasis, prognosis, and survival.