Heteroatom-tagged proteomics of lung cancer and chronic obstructive pulmonary disease human serum reveal alterations in selenoproteins

Heteroatom-tagged proteomics allows the absolute quantification of selenoproteins using the heteroatom as a "tag" into a selective and sensitive atomic detector instead of a molecular one. Using this analytical method, about 90% of total selenium in human serum/plasma can be measured as selenoproteins and total selenometabolites and thus, the status of selenium can be determined. Herein, we determined the absolute concentration of selenoproteins in human serum patients with lung cancer (LC) and chronic obstructive pulmonary disease (COPD), a competing cause of morbidity and mortality in smokers as well as an independent risk factor for LC. We conducted an observational study of 154 human serum samples obtained from LC and COPD patients with varying severity of disease, including COPD patients who developed LC during follow-up and healthy controls (HC). Using heteroatom-tagged proteomics, we determined extracellular glutathione peroxidase (eGPx), selenoprotein P (SELENOP), and selenoalbumin (SeAlb). Associations between selenoproteins were also studied as potential biomarkers of disease. The concentration of eGPx was significantly higher in the all-inclusive COPD cohort compared to HC, COPD patients with LC, or those with mild obstructive lung disease, while SELENOP concentration was significantly decreased in LC patients compared to HC and COPD. We found an inverse correlation between SELENOP and SeAlb in HC, but also in LC patients, and especially in patients with COPD and LC. Moreover, we found that eGPx and selenometabolite concentrations were positively associated with LC human serum. Selenoprotein concentrations were altered in COPD and LC when compared to healthy controls suggesting a potential role of the selenoproteome in the diagnosis and/or treatment of these tobacco -related diseases.