BACKGROUND

Gastrointestinal diffuse large B cell lymphoma (GI DLBCL) is the most common gastrointestinal lymphoma. However, there has not been a comprehensive investigation into the expression patterns of programmed cell death 1 (PD-1) and programmed cell death ligand 1(PD-L1) in GI DLBCL tissues.

METHODS

PD-1 protein expression in tumor-infiltrating lymphocytes (TILs) was evaluated by immunohistochemical staining, and expression of PD-L1 was evaluated by using PD-L1/PAX5 immunohistochemical double staining in 92 GI DLBCL specimens.

RESULTS

The prevalence of positive PD-L1 expression (PD-L1 + ) in GI DLBCL cells and positive PD-L1 expression in non-cancer cells of the GI DLBCL microenvironment (microenvironmental PD-L1, mPD-L1) were 11.96% (11 of 92) and 41.98% (34 of 81), respectively. PD-L1 expression in GI DLBCL was significantly associated with involvement of extranodal sites ≥ 2 (P = 0.034) and mPD-L1 expression was significantly associated with ECOG performance status (score ≥ 2) (P = 0.041). PD-L1 expression and mPD-L1 expression had no prognostic significance (P > 0.05) on disease outcome. PD-1+ TILs were significantly lower in patients with extranodal site involvement (P = 0.011) and the quantity of PD-1 + TILs correlated positively with the level of PDL1 expression in non malignant microenvironment cells (P = 0.001). Patients with high levels of PD-1+ TILs had better prognosis (P = 0.0005).

CONCLUSIONS

The expression patterns of PD-L1 in patients with GI DLBCL are different from patients with common DLBCL. Immunotherapies that target the PD-1/PD-L1 pathway may have therapeutic potential in GI DLBCL.