High PD-L2 Expression Is Associated with Better Disease-Free Survival in Patients with Intrahepatic Cholangiocarcinoma

PD-L2 is expressed in various cancer tissues. Currently, the value of PD-L2 expression in intrahepatic cholangiocarcinoma (ICC) tissues remains unclear. This study investigated the prognostic and clinical significance of PD-L2 expression in ICC. This research employs The Cancer Genome Atlas (TCGA) database to examine the expression profiles of PD-L2 in ICC and to evaluate its prognostic significance. Immunohistochemistry detected PD-L2 expression in 66 postoperative ICC tissues and paired adjacent tissues. Correlations between PD-L2 expression and clinicopathological data were analyzed. Kaplan-Meier survival analysis and Cox proportional hazards regression model were used to evaluate the prognostic value of PD-L2. Bioinformatics analysis shows that high expression of PD-L2 dominates in early ICC patients and is closely associated with tumor recurrence. High PD-L2 expression is associated with longer progression free survival (PFS) (P=0.015). Immunohistochemistry confirmed that the expression of PD-L2 was significantly increased in tumor tissue compared to surrounding tissue. Overexpression of PD-L2 is associated with early TNM staging (P=0.014). Univariate analysis identified preoperative symptoms, number of tumors, tumor size, tumor differentiation, peritumoral integrity, surgical margins, TNM stage, and preoperative CA125 level as associated with overall survival (OS) (all P < 0.05). Preoperative symptoms, number of tumors, peritumoral integrity, surgical margins, TNM stage, preoperative CA125, and PD-L2 expression were associated with disease-free survival (DFS) (all P < 0.05). Multivariate analysis determined tumor differentiation and TNM stage as independent prognostic factors for OS (both P < 0.05). Surgical margins and PD-L2 expression levels were independent prognostic factors for DFS (both P < 0.05). PD-L2 expression is predominantly high in patients with early-stage ICC. PD-L2 expression serves as an independent predictor of DFS in patients with ICC following hepatectomy. ICC patients with elevated PD-L2 expression levels exhibit delayed relapse.