e14525 Background: Immunotherapy has shown promising results in multiple forms of cancer including lung cancer patients. Treatment targeting alternative immune checkpoints may demonstrate value for specific cancers or in combination therapy with other immunotherapies or chemotherapeutic agents. While adenosine has physiological importance in preventing excess inflammatory reactions and inhibiting autoimmunity, it is generated through an enzymatic cascade in the tumor microenvironment whereby AMP is ultimately dephosphorylated to adenosine by CD73 on tumor cells. Previous studies have shown that increased tumor CD73 expression correlated with increased metastasis, worse prognosis and chemotherapy resistance. Methods: Genomic data from the CCLE and TCGA database were evaluated for CD73 expression in lung cancer. The specificity of an anti-CD73 antibody (Cell Signaling) was confirmed by Western blotting in lung cancer cell lines. Immunohistochemistry (IHC) was performed for FFPE lung cancer cell lines and a NSCLC patient cohort. CD73 expression data was correlated with patient demographic data including outcomes. Results: CD73 mRNA was expressed in lung cancer cell lines (70/126, 55.6%) and did not correlate with other immune checkpoint ligands including PD-L1, GAL-9, and B7H4 in NSCLC. Review of the TCGA database identified CD73 expression is highest in thyroid carcinoma and significant in lung cancer. The prevalence of CD73 protein expression by IHC in NSCLC cell lines was 84.8% (39/46) and 15.4% (6/39) in SCLC cell lines. We also evaluated CD73 protein expression in a NSCLC cohort with a prevalence of 32.1% (36/112), with no significant correlation to patient clinical characteristics or outcomes. Conclusions: We evaluated the expression of the immune checkpoint, CD73, in lung cancer cell lines and tissues. Both genomic data and protein expression by IHC demonstrated CD73 was significantly expressed. However, there was no correlation with other immune biomarkers or patient demographics or outcomes. CD73 is a new target for immunotherapy and current clinical studies with CD73 inhibitors may prove beneficial to lung cancer patients.
P33.02 Comparison of PD-L1 Protein Expression Between Primary and Metastatic Lesions in Lung Cancer Patients
