Oxidative DNA damage plays crucial roles in the pathogenesis of numerous diseases including cancer. 8-hydroxy-2′-deoxyguanosine (8-OHdG) is the most representative product of oxidative modifications of DNA, and urinary 8-OHdG is potentially the best non-invasive biomarker of oxidative damage to DNA. Herein, we developed a sensitive, specific and accurate method for quantification of 8-OHdG in human urine. The urine samples were pretreated using off-line solid-phase extraction (SPE), followed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. By the use of acetic acid as an additive to the mobile phase, we improved the UPLC-MS/MS detection of 8-OHdG by 2.7−5.3 times. Using the developed strategy, we measured the contents of 8-OHdG in urine samples from 142 healthy volunteers and 84 patients with colorectal cancer (CRC). We observed increased levels of urinary 8-OHdG in patients with CRC and patients with tumor metastasis, compared to healthy controls and patients without tumor metastasis, respectively. Additionally, logistic regression analysis and receiver operator characteristic (ROC) curve analysis were performed. Our findings implicate that oxidative stress plays important roles in the development of CRC and the marked increase of urinary 8-OHdG may serve as a potential liquid biomarker for the risk estimation, early warning and detection of CRC.

Potential application of the oxidative nucleic acid damage biomarkers in detection of diseases Potential application of the oxidative nucleic acid damage biomarkers in detection of diseases

Colorectal cancer (CRC) is a common malignant neoplasm worldwide. It is important to identify new biomarkers for the early detection of CRC. In this study, magnetic beads and the Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) platform were used to analyse CRC and healthy control (HC) serum samples. The CRC diagnosis pattern was established to have a specificity of 94.7% and sensitivity of 92.3% in a blind test. The candidate biomarker serine/threonine kinase 4 (STK4, also known as MST1) was identified by Tandem mass spectrometry (MS/MS) and verified with western blotting and enzyme-linked immunosorbent assay (ELISA). The results indicated that there was a higher concentration of MST1 in HC subjects than stage I CRC patients for the early detection of CRC and a lower concentration in stage IV patients than in other CRC patients. The sensitivity and specificity of MST1 combined with carcinoembryonic antigen (CEA) and faecal occult blood test (FOBT) in diagnosis of colorectal cancer were 92.3% and 100%, respectively. Additionally, low MST1 expression was associated with the poor prognosis. These results illustrate that MST1 is a potential biomarker for early detection, prognosis and prediction of distant metastasis of CRC.