Parallel assessment of circulatory cell-free DNA by PCR and nucleosomes by ELISA in breast tumors

Objectives: In order to assess the potential biomolecules for breast cancer, we analyzed in parallel the levels of cell-free glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and cell-free nucleosomes in serum samples from patients with benign and malignant breast tumors. The levels of cell-free DNA obtained by quantitative PCR were compared with those obtained by enzyme-linked immunosorbent assay (ELISA). Methods: Twenty-three patients with benign breast tumors, 27 patients with breast cancer, and 32 age-matched healthy women were recruited. The amounts of serum nucleosomes were analyzed by ELISA and the levels of cell-free GAPDH were measured by real-time quantitative PCR. The correlation between nucleosome and cell-free GAPDH levels was examined using the Spearman rank test. Results: The levels of cell-free GAPDH were significantly higher in the serum samples of patients with benign and malignant breast tumors than in those of the control group (median 37,966 GE/mL, range 3,802-130,104 versus 11,770 GE/mL, range 2,198-73,522, p=0.035 and median 40,698 GE/mL, range 3,644-192,482 versus 11,770 GE/mL range 2,198-73,522, p=0.001). The concentration of cell-free GAPDH correlated significantly with the quantities of nucleosomes in serum samples (r=0.451, p=0.000). There was, however, no significant difference between healthy individuals and women with benign breast tumors or breast cancer in terms of nucleosomes determined by ELISA. Conclusion: Our data suggest that the cell-free serum GAPDH DNA assayed by quantitative PCR is a better biomarker than nucleosomes assayed by ELISA in patients with breast tumors.