Multi-analyte study of circulating cytokines in smokers, with or without chronic obstructive pulmonary disease, and with or without lung cancer, using biochip array technology

Cytokines are naturally occurring small regulatory proteins produced by variouscell types. They act as external controlling elements in haematopoiesis and also mediateand control immune and inflammatory responses. Changes in cytokine levels havebeen reported in chronic obstructive pulmonary disease (COPD), a common inflammatorydisease of the airways. Similarly, changes in circulating cytokine levels havebeen reported in other pulmonary disorders including lung cancer, but the specificnature of these changes is poorly defined. Because cytokines normally function as partof a complex interacting network, the use of a multiplexed approach for their determinationis important. Biochip array technology enables such an approach and cangenerate a cytokine profile from a single sample, at a single point in time. The aimof this study was to determine twelve cytokines simultaneously in the plasma ofnon-smokers and smokers with or without COPD and with or without lung cancerusing Evidence biochip array technology. The cytokines IL-1a, IL-1b, IL-2, IL-4, IL-6,IL-8, IL-10, VEGF, IFNc, EGF, MCP-1 and TNFa were quantified by simultaneous chemiluminescentimmunoassays on the biochip array. The biochip represents the solidphaseand the vessel where the immunoreactions take place in discrete test sites.The Evidence analyzer was used for all determinations. Serum samples from 55non-smokers, 54 smokers without COPD and 48 smokers with COPD were analyzed.The Kruskal-Wallis test with a false discovery rate (FDR) of 0.10 was used to identifycytokines that were differentially expressed across the 5 groups. For the cytokinesthat met the FDR criterion, post-hoc comparisons were made using Dunn’s methodwith a family-wise error rate 0f 0.05.Four cytokines appeared to be differentially expressed across groups: IL-6, IL-8,VEGF and MCP1. Results of the post-hoc pairwise comparisons suggest plasma cytokinelevels are significantly different between the following groups: non-smokers vs.adenocarcinoma (IL-6, IL-8); non-smokers vs. squamous cell cancer (IL-6, IL-8, VEGF);non-smokers vs. smokers with COPD (MCP1); smokers without COPD vs. adenocarcinoma(IL-6); smokers with COPD vs. squamous cell carcinoma (IL-6); smokers withoutCOPD vs. squamous cell carcinoma (IL-6, IL-8, VEGF) and adenocarcinoma vs.squamous cell carcinoma (VEGF, IL-8). The biochip array enables the simultaneousassessment of 12 cytokines in a single sample and shows differences between severaldistinct clinical groups. This represents