癌症近年來依然在國人死因排行榜上佔有一席之地，而大部分人類癌症的產生，與環境因素或生活型態有密切關係，也因此癌症的預防更顯得的重要。DNA adducts被認為是化學致癌過程中最早的基因傷害，而各種烷基化DNA adducts中又以7-methylguanine（7-MG）的量為最多。當基因傷害來不及被體內修復機制所修補，則細胞複製時便易發生錯誤，導致突變。過去分析DNA adducts或7-MG的方法受限於化學專一性及敏感度，往往無法準確的定量DNA adducts。若能尋求一種具有高度敏感性及專一性的分析方法，應用在生物偵測相關分析上，對於癌症早期發現定有相當的幫助。本研究目的在建立一氣相層析儀串連質譜儀配合同位素稀釋法，以分析內生性與外生性的7-MG，並利用此方法探討化學致癌物Dacarbazine(DTIC)所誘發基因傷害。DTIC 分別溶於水中與Dimethyl Sulfoxide (DMSO)中，經腹腔以30 mg/kg及100 mg/kg的DTIC注射處理小白鼠。經過暴露六小時後，處理的老鼠肝臟7-MG含量分別為1.119 ± 0.331、3.993 ± 0.634 pmol/μmol Guanine，較控制組0.111 ± 0.078 pmol/μmol Guanine為高。而DMSO實驗中亦是如此。由結果顯示，此氣相層析加質譜儀方法可成功的分析7-MG，同時具有非常高的的專一性及敏感性，。; In Taiwan, cancer has been an important causes of death. Factors have been considered to be associated with environmental exposures and life styles like pollutants in air and water, cigarette smoking, toxic chemicals in our daily diet. DNA adduct is considered to be one of early events of DNA lesions in chemical related cancer development. If these DNA lesions cannot be repaired, occurrences of mutations may raise to a higher probability during DNA replication so that DNA adducts are considered as risk-associated biomarkers. Analysis of DNA adducts has been limited by specificity and sensitivity of detect methods. In this study, we present an Isotope-dilution GC/MS method to quantitate 7-methylguanine (7-MG), an DNA alykylation adduct. Dacarbazine (DTIC) , an known carcinogen in animals, was dissolved in water and dimethyl sulfoxide (DMSO). Mice were treated with 30 and 100 mg/kg DTIC through i.p. injection for 6 hours. 7-Mg was quantitated with our GC/MS with excellent specificity and sensitivity. Tthe content of 7-MG in liver DNA was 1.119 ±0.331 pmol/μmol guanine and 3.993 ±0.634 pmol/μmol guanine, respectively. These numbers were significantly higher than those in control mice. The dose-related increase in 7-MG content was also observed for mice treated with DTIC dissolved in DMSO. In conclusions, this Isotope-dilution GC/MS Method is able to detect ultra trace of 7-MG with excellent specificity and sensitivity.
