Aim: To investigated the mechanism of Chloroethylnitrosoureas (CENUs) leading to secondary tumors after therapy, three kinds of CENUs, namely, Nimustine (ACNU), Carmustine (BCNU) and Semustine (MeCCNU) were used to investigated drug-induced DNA interstrand crosslinks(ICLs). Method: The alkaline comet assay was adopted to compare DNA damages induced by CENUs under different concentrations. Results: With the increase of drug’s concentration, DNA migration exhibited a positive concentration-dependent relationship in all three drugs. ACNU was shown to cause significant crosslinking. The other two drugs also induced crosslinking, but this could not be analyzed at high concentrations due to the high cytotoxicity of the drugs which caused cells death.

The single cell gel electrophoresis is a common technology for the detection of DNA damage.It has the advantages of high sensitivity,economic,easy and fast.Nearly three decades,this technology is widely used in genetic toxicology,environmental monitoring,medical diagnostics and nutrition research.The single cell gel electrophoresis technique not only is capable of detecting DNA damage but also can detect DNA crosslinks,UV-induced pyrimidine dimers,oxidized bases and alkylation damage after joined fragmenting agent or specific endonuclease.Recently,single-cell gel was widely used in many fields by combining with fluorescence in situ hybridization.This article reviewed the conventional and unconventional single cell gel electrophoresis methods,and the prospects were also discussed.

The relationship between carcinogenicity and DNA interstrand cross-links of nitrosoureas is poorly defined. 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3- (2-chloroethyl)- 3- nitrosourea (ACNU, nimustine) is one of nitrosoureas used in the treatment of high-grade gliomas. It has the capability of causing DNA interstrand cross-links (ICLs) to kill cancer cells. But it can also cause the generation of secondary tumors with carcinogenic side effects. In present study, we investigated DNA interstrand cross-links, DNA double-strand breaks and cell cycle phase in NIH/3T3 cells from the primary mouse embryonic fibroblast cells induced by ACNU. This result indicated that the concentration of 60 and 75μg/ml of ACNU could be detected significantly ICLs, and the γ-H2AX has the ability to be a biomarker for DNA damage associated with ICLs induced by ACNU. The subgroup of nitrosoureas (CNUs) including 1-(4-amino -2-methyl-5- pyrimidinyl) methyl-3 -(2- chloroethyl) -3- nitrosourea (ACNU, nimustine), 1,3- Bis(2- chloroethyl)- 1- nitrosourea (BCNU, carmustine), 1-(2- chloroethyl)- 3- cyclohexyl- nitrosourea (CCNU, lomustine),

[Objective] The aim was to determine whether the concentration and addition sequence of DNA breaking agent have effect on DNA crosslinking detection in Single Cell Gel Ectrophoresis(SCGE).[Method] Carmustine(BCNU),a tumor drug,was used as DNA crosslinking agent,and tert-butyl hydroperoxide(tBHP) as DNA breaking agent.The effect of addition sequence and concentration of tBHP on BCNU DNA crosslinking was assessed by the Tail-length in SCGE.T-test was performed to indicate statistical significance.[Result] There was no significant difference between the tBHP pre-treatment and post-treatment in tail-length.Moreover,the DNA fracture was increased with the rise of tBHP concentration,and 400 μmol/L showed a marked DNA breaking effect.[Conclusion] tBHP addition sequence has no effect on DNA crosslinking detection,and concentration 400 μmol/L was the best dose in DNA breaking.

All over the world,cancer has become a major public health problem.Epidemiological studies have shown that about 80%~90% of human cancers are caused by the environment;the most important cancer-causing factors are chemical factors.Di-region theory,one mechanism of chemical carcinogens,pointed out that environmental carcinogenic agents were metabolized into a specific bi-functional alkylation agent,then induced DNA interstrand cross-linking and final caused cancer.Although there are many methods to detect DNA interstrand cross-linking,its mechanism that causes normal cells to become tumor is still unclearly,and has also become the focus of attention.Based on the structure,formation process and detection methods of DNA interstrand cross-linking,the research progress on the relationship of DNA interstrand cross-linking and cancer was reviewed in this paper.It hopes to provide some ideas for the research on the mechanism of environmental carcinogens.