Programmed death-1 (PD-1) ligand 1 and PD-1 ligand 2 expressions and their clinical relevance in colorectal cancer

ABSTRACT

PURPOSE: Programmed death-1 and its ligands (PD-L1 and PD-L2) can induce T-cell apoptosis in many solid tumors, although there is limited information regarding their roles in colorectal cancer.METHODS: We used immunohistochemistry to retrospectively examine expressions of PD-L1 and PD-L2 in paraffin-embedded specimens from 104 patients with colorectal cancer.RESULTS: Among the 104 included patients, 31 patients (29.8%) had positive PD-L1 expression and 73 patients (70.2%) had negative PD-L1 expression. Positive PD-L2 expression was observed in 83 patients (79.8%) and negative PD-L2 expression was observed in 21 patients (20.2%). Positive PD-L1 expression group showed higher overall survival rate (OS) and disease-free survival (DFS) than negative PD-L1 expression group. However, the overall survival and DFS were not significantly different between positive and negative PD-L2 expressions group. The multivariate analyses revealed that short OS was independently associated with positive PD-L1 expression (hazard ratio [HR], 2.781; 95% confidence interval [CI], 1.284–6.026; P=0.01), regional lymph node status (HR, 2.611; 95% CI, 1.258–5.418; P=0.01), and distant metastasis (HR, 4.279; 95% CI, 1.449–12.638; P=0.009). In addition, short DFS was independently associated with positive PD-L1 expression (HR, 2.846; 95% CI, 1.393–5.815; P=0.004) and regional lymph node status (HR, 2.310; 95% CI, 1.122–4.758; P=0.023).CONCLUSION: Although prospective multi-center studies are needed to validate our findings, we found that PD-L1 expression predicted OS and DFS among patients with colorectal cancer.