HLA class I antigen expression is associated with a favorable prognosis in early stage non‐small cell lung cancer

Human leukocyte antigen (HLA) class I displays a repertoire of endogenously processed peptides to CD8+ T lymphocytes. The present study assessed correlations between HLA class I expression, clinicopathologic factors, and tumor‐infiltrating immune cells in human non‐small cell lung cancers (NSCLC). Expression of HLA class I was assessed in 161 resected primary NSCLC by immunohistochemistry using EMR8–5, a novel monoclonal anti‐pan HLA class I heavy chain antibody. Expression of HLA class I was classified into three categories: strongly positive, weakly positive, or negative. Tumor‐infiltrating CD8+ lymphocytes and CD56+ natural killer cells within cancer nests and stroma were also counted. Expression of HLA class I was strongly positive in 50 tumors, weakly positive in 57 tumors, and negative in 54 tumors. Down‐regulation of HLA class I was significantly correlated with male sex, history of smoking, non‐adenocarcinoma histology, and moderate‐/low‐grade differentiation. The density of cancer nest‐infiltrating CD8+ cells in HLA class I‐negative tumors was significantly decreased compared to that in HLA class I strongly positive tumors (P