Can free DNA be detected in sputum of lung cancer patients?

Free DNA is present in the serum of cancer patients in a higher concentration than that in non-cancer patients. Free DNA in sputum may originate from malignant or inflammatory diseases. The aim of the study was to examine the presence of free DNA in sputum and the relationship to lung cancer. The contribution of inflammatory cells was established as well. The amount of free and cellular DNA in sputum was determined using real-time beta-globin PCR in 28 lung cancer patients and 68 controls. Free DNA was present in sputum samples of the cancer patients and controls. We found no differences in DNA concentration in sputum of patients with and without lung cancer. For all patients combined the amount of free DNA was related to the amount of inflammation. Further, we found increased hypermethylation of RASSF1A in lung cancer patients compared to controls to show that tumour related DNA is present in sputum. In conclusion, free DNA can be detected in sputum of lung cancer patients. The amount of free DNA is related to the amount of inflammation, but not to the presence of lung cancer.