a qRT–PCR analysis of PD-L2 mRNA expression in 25 oesophageal cancer samples of matched normal epithelium and cancer. High PD-L2 expression was observed in the tumour part compared with normal epithelium (P = 0.048). b Immunohistochemistry of PD-L2 expression in oesophageal cancer tumour sections. In PD-L2-positive cases, PD-L2 was stained in the cytoplasm and/or membrane of cancer cells. Original magnification, ×200. c Kaplan–Meier curves for overall survival in oesophageal cancer patients according to PD-L2 expression status. The PD-L2-positive group showed a significantly shorter overall survival than the PD-L2-negative group (log-rank P = 0.011). d Relationship between PD-L2 and overall survival. Loge (hazard ratio) plots of overall survival rate in PD-L2-positive and PD-L2-negative groups are shown. The effect of PD-L2 was not significantly modified by age, sex, tobacco, comorbidity, location, pathological stage or recurrence (P > 0.14 for all interactions).