Clinical Significance and Prognostic Value of Serum Dickkopf-1 Concentrations in Patients with Lung Cancer

BACKGROUND: Dickkopf-1 (DKK1), a secreted protein, is known as a negative regulator of the Wnt signaling pathway, which has been implicated in the development of several types of cancers. Clinical significance of serum DKK1 in lung cancer remains to be determined. METHODS: A novel time-resolved immunofluorometric assay was developed. By use of this method, we investigated the serum concentrations of DKK1 in 592 patients with malignancies, 72 patients with benign lung disease, and 120 healthy controls. Serum cytokeratin 19 fragment and neuron-specific enolase values were obtained. RESULTS: Serum DKK1 concentrations were significantly higher in patients with lung cancer than in patients with other malignant tumors or benign lung diseases and healthy controls. Serum concentrations of DKK1 were decreased significantly in groups of patients with gastric cancer, colorectal cancer, ovarian cancer, and cervical adenocarcinoma compared with healthy controls. Application of both DKK1 and cytokeratin 19 fragment increased sensitivity, correctly identifying 89.6% of the non-small cell lung cancer patients as positive. The use of both DKK1 and neuron-specific enolase increased sensitivity to detect small cell lung cancer to 86.2%. DKK1 concentrations increased with stage, tumor class, and presence of lymph node and distant metastases, regardless of histology and patient age and sex. Patients with a DKK1 concentration of 22.6 microg/L or higher had a statistically significantly diminished survival compared with patients whose DKK1 values were lower. CONCLUSIONS: DKK1 was preferentially expressed in lung cancer. Increasing concentrations of DKK1were significantly associated with tumor progression and decreased survival in patients with lung cancer. .