Expansion of myeloid-derived suppressor cells in chronic obstructive pulmonary disease and lung cancer: potential link between inflammation and cancer

Background Chronic obstructive pulmonary disease (COPD) is a risk factor for lung cancer (LC). Myeloid-derived suppressor cells (MDSCs) down-regulate the T cell receptor zeta chain (TCR zeta) through l-arginine deprivation and lead to T cell dysfunction and deficient antitumor immunity. We hypothesized that abnormally high levels of MDSCs in COPD patients may alter tumor immunosurveillance. Methods We compared the proportion of circulating MDSCs (Lin-HLA-DR-/CD33+/CD11b+) (by flow cytometry), arginase I (ARG I) serum levels (by ELISA), and expression levels of TCR zeta on circulating lymphocytes (by flow cytometry) in 28 patients with LC, 62 subjects with COPD, 41 patients with both LC and COPD, 40 smokers with normal spirometry and 33 non-smoking controls. T cell proliferation assays were performed in a subgroup of participants (CFSE dilution protocol). Results We found that: (1) circulating MDSCs were up-regulated in COPD and LC patients (with and without COPD); (2) MDSCs expansion was associated with TCR. down-regulation in the three groups; (3) in LC patients, these findings were independent of COPD and tobacco smoking exposure; (4) TCR zeta down-regulation correlates with T cell hyporesponsiveness in COPD and LC patients. Conclusions These results suggest that tumor immunosurveillance might be impaired in COPD and may contribute to the increased risk of LC reported in these patients.