The focus of the current investigational study was to examine whether
circulating nucleic acids (i.e.,
DNA and
microRNAs) have the potential to become suitable blood-based markers for diagnosis and progression of
lung cancer. The concentrations of
cell-free DNA and four circulating
microRNAs (miR10b, miR34a, miR141 and miR155) as well as the
caspase activity were measured in serum of 35
lung cancer patients (19
non-small-cell lung cancer, 8
small cell lung cancer patients and 8 patients with indefinite
cancer type), 7 patients with benign lung
tumors and 28 healthy individuals by
PicoGreen, TaqMan
MicroRNA, and
Caspase-Glo®3/7 assay, respectively. The data were correlated with the established risk factors for
lung cancer progression. The concentrations of
cell-free DNA (p = 0.0001), serum
microRNAs (p = 0.0001) and
caspase activities (p = 0.0001) significantly discriminated
cancer patients from healthy individuals. Serum
DNA,
caspase activities and
RNA levels could not distinguish between patients with benign
lung disease and
cancer patients. However, the levels of miR10b (p = 0.002), miR141 (p = 0.0001) and miR155 (p = 0.007) were significantly higher in
lung cancer patients than those in patients with benign disease. As determined by the Spearman-Rho test, high levels of
cell-free DNA significantly correlated with elevated circulating
caspase activities (p = 0.0001). In
lung cancer patients high serum miR10b values associated with
lymph node metastasis (p < 0.03) and elevated levels of TPA (
tissue polypeptide antigen, p = 0.01), whereas high serum miR141 values associated with elevated levels of uPA (
urokinase plasminogen activator, p = 0.02). The findings of our pilot study suggest that the assays for
circulating DNA,
microRNAs and
caspase activities in blood might become novel minimally invasive diagnostic tools for detection and risk assessment of
lung cancer, provided that their clinical utility can be confirmed in larger prospective trials.