PD-L1 gene promoter methylation represents a potential diagnostic marker in advanced gastric cancer

Gastric cancer is one of the most prevalent malignant tumors worldwide. Immunological checkpoint inhibitors of the programmed death 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) signaling pathway are effective in the treatment of various malignant tumor types, but the potential of such immunotherapeutic techniques for the treatment of gastric cancer is yet to be elucidated. The purpose of the present study was to investigate the methylation of the PD-L1 gene promoter and its clinical significance in advanced gastric cancer, as this may suggest the use of PD-L1 promoter methylation as a novel biomarker for gastric cancer progression. In a total of 70 samples, the methylation rate of the PD-L1 gene promoter region was significantly higher in gastric cancer tissues compared with adjacent tissues. A high level of PD-L1 promoter methylation was associated with lymph node staging, and resulted in poorer prognoses in patients with advanced gastric cancer. A total of 26 patients exhibited highly methylated PD-L1; in this group, the median progression-free survival time of patients receiving platinum/fluorouracil chemotherapy was 4.2 months longer than those receiving paclitaxel/fluorouracil chemotherapy, and the risk of disease progression in patients receiving paclitaxel/fluorouracil chemotherapy was 5.009 times higher compared with patients who received platinum/fluorouracil chemotherapy. Additionally, PD-L1 promoter methylation was significantly correlated with PD-L1 expression, and the progression of advanced gastric cancer. In conclusion, high methylation levels of the PD-L1 promoter region may be a faciliatory mechanism enabling gastric cancer tumorigenesis, and may also represent an independent prognostic factor for chemotherapeutic efficacy in patients with advanced gastric cancer.