We sought to identify peripheral blood markers associated with two immune-related factors —programmed cell death-ligand-2 (PD-L2) and indoleamine 2,3-dioxygenase-1 (IDO1)—that are expressed on tumor cells in primary lung adenocarcinoma (AD) specimens. We randomly selected 448 patients (70%) from 640 consecutive patients with resected stage I–III primary lung AD, who had been treated at that point with surgery alone. Expression of PD-L2 and IDO1 in these patients was assessed by immunohistochemistry, and evaluated with respect to peripheral blood markers measured before surgery, including white blood cells, absolute neutrophil count, absolute lymphocyte count, absolute monocyte count (AMC), absolute eosinophil count (AEC), serum C-reactive protein, and serum lactate dehydrogenase levels. Membrane PD-L2 expression and cytoplasmic IDO1 expression were defined by tumor proportion score (TPS); samples with TPS < 1% were considered negative. Logistic regression models were used to identify variables associated with the immune-related factors. Advanced stage (P = 0.0090), higher AMC (P = 0.0195), and higher AEC (P = 0.0015) were independent predictors of IDO1 expression. PD-L2 expression was not associated with any tested peripheral blood markers. Peripheral blood markers, especially AMC and AEC, could potential predict IDO1 expression in lung AD. This study should be replicated in another cohort; further efforts to explore other biomarkers that predict PD-L2 or IDO1 expression are also warranted.
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