Differential Expression of Immune-Regulatory Protein C5AR1, NLRP3 and CLEC4A on Peripheral Blood Mononuclear Cells in Early-Stage Non-Small Cell Lung Cancer Patients

Background: Previous studies from our group reported paracrine signal-induced peripheral mononuclear cell (PBMC) gene upregulation in various cancer types through epigenetic regulation. We speculated protein expression on circulating T- lymphocytes which might represent T-lymphocyte trafficking before infiltrating into tumor microenvironment. The possibility to use protein expression on circulating T-lymphocytes as a biomarker to discriminate early stage lung cancer has been explored.Methods: PBMC gene expression was explored, using 4 independent gene expression microarray datasets (GSE12771, GSE13255, GSE20189 and GSE3934). We selected 3 candidate proteins, C5AR1, NLRP3 and CLEC4A, based on their significant protein expression in tumor-infiltrating lymphocytes but not in normal lymphoid tissue. A validation study using automated flow cytometry was conducted in 121 participants including 44 treatment-naïve early stage non-small cell lung cancer patients (NSCLC), 19 non-malignant pulmonary diseases and 62 healthy individuals. Results: The ratio of C5AR1, NLRP3 and CLEC4A specific antibody staining to CD3 positive was significantly higher in early stage NSCLC compared to healthy control. Median ratio of C5AR1, NLRP3 and CLEC4A expression in early stage NSCLC were 0.65 [range 0.27-0.96; 95% CI: 0.55-0.70], 0.83 [range 0.27-0.99; 95% CI: 0.73-0.86] and 0.75 [range 0.21-0.98; 95% CI: 0.65-0.81], respectively. While, median ratio of C5AR1, NLRP3 and CLEC4A expression in healthy control were 0.21 [range 0.05-0.81; 95% CI: 0.23-0.42, p-value <0.001], 0.32 [range 0.04-0.94; 95% CI: 0.28-0.46, p-value <0.001] and 0.22 [range 0.04-0.97; 95% CI: 0.27-0.48, p-value < 0.001], respectively. This led to 87.5-100% sensitivity, 50.9-64.7% specificity and 71.4-75% accuracy. However, those PBMC protein expressions could not discriminate early stage NSCLC from malignant-mimic inflammation and infection.Conclusions: Our proof-of-principle findings strengthen the hypothesis that malignancies generate distinctive protein expression fingerprints on circulating T-lymphocytes. Trial registration: This trial was registered with clinicaltrials.in.th, Number TCTR20190508003.