Abstract
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.
Highlights
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
To assess the association between oxidative DNA damage and risk of colorectal cancer (CRC), here we developed an enhanced ionization method for highly sensitive determination of 8-OHdG in human urine by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis combined with a solid-phase extraction (SPE) procedure
A QC sample was measured every fifteen urine samples to monitor whether the system was still stable after hundreds of injections. The parameters such as retention time, peak symmetry and accuracy were checked and the results showed good system stability. All these results proved that the developed SPE combined with UPLC-MS/MS method using CH3COOH as mobile phase additive was sensitive, accurate and reproducible to analyze 8-OHdG in urine samples
Summary
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. 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. An imbalance between the production and scavenging of ROS, known as oxidative stress, will lead to the damage of cellular proteins, lipids and nucleic acids[4,5]. The levels of 8-OHdG in DNA isolated from gastric carcinoma tissue were significantly higher than that from normal gastric tissue, and consistent results were obtained in peripheral blood mononuclear cells of cancer patients compared with healthy controls. Reduction of urinary 8-OHdG level in cancer patients after surgical operation was observed[22] All of these findings prompt us to propose that 8-OHdG is a potential biomarker for cancer risk estimation, early detection, treatment and prognosis
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