Expression and clinical significance of PD-L1 and infiltrated immune cells in the gastric adenocarcinoma microenvironment

Programmed death-ligand 1 (PD-L1) is a crucial negative costimulatory molecule expressed on both tumor and immune cells. It binds to programmed death-1, facilitating tumor escape. Tumor-infiltrating immune cells play a vital role in this process. However, the clinical relationship between PD-L1 expression and tumor-infiltrating immune cells remains uncertain. Immunohistochemistry (IHC) was utilized to assess PD-L1 expression and TIIC markers (CD3, CD4, CD8, CD19, CD31, CD68, CD11c, CD56, and α-smooth muscle actin) in gastric adenocarcinoma tissues from 268 patients. The aim was to explore the prognostic significance of PD-L1 and the infiltration of different immune cell types. The study analyzed overall survival and the correlations between PD-L1 expression, immune cell infiltration, and clinicopathological characteristics. Among the 268 patients, 52 (19.40%) exhibited high PD-L1 expression on tumor cells (TPD-L1), while 167 (62.31%) displayed high PD-L1 expression on immune cells (IPD-L1). Patients with high IPD-L1 expression showed improved survival compared to those with low IPD-L1 expression (P = .028). High TPD-L1 expression associated with various clinicopathological features, such as larger tumor size, poorer differentiation, deeper invasion depth, and higher tumor stage. Conversely, patients with high IPD-L1 expression exhibited shallower tumor invasion and lower mortality rates. Univariate analysis indicated that superficial tumor infiltration, absence of lymph node and distant metastasis, low tumor stage, high IPD-L1 expression, and elevated CD8 and CD19 expression were associated with a reduced risk of tumor progression. Multivariate analysis revealed that patients with high IPD-L1 and CD8 expression or high TPD-L1 and low CD31 expression experienced significantly better overall survival than patients with other combinations. The findings indicate that patients with high PD-L1 expression in immune cells have a substantially improved prognosis. Additionally, the combination of PD-L1 with CD8 or CD31 expression status can serve as an indicator of prognosis in patients with gastric adenocarcinoma.