Quantitative Assessment of CD200 and CD200R Expression in Lung Cancer

SIMPLE SUMMARY: Most patients with advanced non-small cell lung cancer (NSCLC) do not respond to programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis blockade, highlighting the need for the identification of new targets for immune checkpoint inhibition. In this study, we used quantitative immunofluorescence to characterize the CD200/CD200R immune checkpoint in lung cancer. We described a careful validation of antibody probes for this pair and found CD200 and CD200R to be overexpressed in 29.7% and 25% of NSCLC patients, respectively; stromal expression of CD200R was significantly increased in patients with squamous histology. Additionally, we showed that PD-L1 was moderately correlated with CD200 but only weakly correlated with CD200R. As new drugs targeting the CD200/CD200R interaction enter into clinical trials in humans, this work identifies this immune checkpoint as a potential target for patients with NSCLC and lays the groundwork for the development of a clinical companion diagnostic test. ABSTRACT: CD200/CD200R is an immune checkpoint with broad expression patterns and a potential target for immune therapy. In this study, we assess both CD200 and CD200R expression in solid tumors, with a focus on lung cancer, and evaluate their association with clinicopathologic characteristics, mutation status, outcome, and programmed death-ligand 1 (PD-L1) expression. We used multiplexed quantitative immunofluorescence (QIF) to measure the expression of CD200 and CD200R in a total of 455 patients from three lung cancer cohorts. Using carefully validated antibodies, we performed target measurement with tyramide-based QIF panels and analyzed the data using the PM2000 microscope and AQUA software. CD200 tumor positivity was found in 29.7% of non-small cell lung cancer (NSCLC) patients and 33.3% of lung large cell neuroendocrine carcinoma (LCNEC) patients. CD200 demonstrated notable intratumoral heterogeneity. CD200R was expressed in immune cells in 25% of NSCLC and 41.3% of LCNEC patients. While CD200R is predominantly expressed in immune cells, rare tumor cell staining was seen in a highly heterogeneous pattern. CD200R expression in the stromal compartment was significantly higher in patients with squamous differentiation (p < 0.0001). Neither CD200 nor CD200R were associated with other clinicopathologic characteristics or mutation status. Both biomarkers were not prognostic for disease-free or overall survival in NSCLC. CD200 showed moderate correlation with PD-L1. CD200/CD200R pathway is frequently expressed in lung cancer patients. Differential expression patterns of CD200 and CD200R with PD-L1 suggest a potential role for targeting this pathway alone in patients with NSCLC.