The landscape of immune microenvironment in lung adenocarcinoma and squamous cell carcinoma based on PD-L1 expression and tumor-infiltrating lymphocytes.

Aims: The aim of this study was to investigate the tumor microenvironment immune types (TMIT) based on tumor cell programmed cell death ligand 1 (PD-L1) expression and tumor-infiltrating lymphocytes (TILs) distribution and whether distinct TMIT subtypes (TMIT I, PD-L1 /TIL ; TMIT II, PD-L1 /TIL ; TMIT III, PD-L1 /TIL ; and TMIT IV, PD-L1 /TIL ) differentially affect clinical outcomes of patients with lung adenocarcinoma (LAC) and squamous cell carcinoma (SCC).

Methods And Results: Immunohistochemistry (IHC) was applied to evaluate the expression of PD-L1 and the spatial distribution of programmed cell death 1 (PD-1) and CD8 TILs on the surgically resected specimens from 205 cases of LAC and 149 cases of SCC. PD-1 and CD8 TILs were more frequently distributed in SCC than those in LAC, regardless of their infiltrating in the tumor islets or stroma. The density of TILs was a poor prognostic factor in LAC but a favorable one in SCC. PD-L1 levels and its clinical prognostic significance differed in LAC vs SCC. LAC patients with TMIT III and SCC patients with TMIT I had the longest survival, respectively (P = .0197 and .0049). Moreover, TMIT stratification based on tumor cell PD-L1 expression and stromal CD8 TILs could be considered as an independent prognostic factor of SCC patients' survival as determined by both univariate and multivariate analysis.

Conclusion: Our study indicates that different type of TMIT provides its specific microenvironment with diverse impact on survival of LAC and SCC patients and highlights the importance of the integrative assessment of PD-L1 status and TILs' spatial distribution to predict patients' prognosis.