Exploration Of Esophageal Cancer Etiology Using Comprehensive DNA Adduct Analysis (DNA Adductome Analysis)

Yukari TOTSUKA, National Cancer Center Research Institute, Japan
LIN Y. 2 , KATO M. 3 , ELZAWAHRY A. 3 , TOTOKI Y. 4 , SHIBATA T. 4 , MATSUSHIMA Y. 5

1 Div. Carcinogenesis & Cancer Prevent., Natl. Cancer Ctr Res. Inst.
2 Dept. Publ. Health, Aichi Med. Univ. Sch. Med.
3 Dept. Bioinformatics, Natl. Cancer Ctr Res. Inst.
4 Div. Cancer Genomics, Natl. Cancer Ctr Res. Inst.
5 Dept. Applied Biol. Chem., Tokyo Univ. Agricul.

China has the highest incidence and mortality rate of esophageal cancer in the world. Ci Xian, one of the high-risk areas in China, demonstrates a much higher incidence when compared with other urban areas in China. To address the etiology of esophageal cancer in Ci Xian, we carried out a comprehensive DNA adduct analysis (DNA adductome) using surgical specimens collected from esophageal cancer patients living in high- and low-risk areas. The results of principal component analysis showed that several DNA adducts were present in tissues among patients in the high-risk area. By referring to the DNA adducts database, N2-(3,4,5,6-tetrahydro-2H-pyran-2-yl)deoxyguanosine (THP-dG), which was derived from N-nitrosopiperidine (NPIP), emerged as a major DNA adduct. In order to confirm the DNA adduct diagnosed as being highly correlated to the high-risk area, we synthesized authentic 15N-THP-dG and analyzed it by quantitative LC-MS/MS apparatus. A peak corresponding to THP-dG, eluted at the same position of authentic 15N-THP-dG, was observed in the surgical specimens collected from the high-risk area. Based on the whole exome/genome analyses of esophageal cancer patients living in the high-risk area and Salmonella strains exposed to NPIP with metabolic activation systems, G:C to A:T transition was predominant in both human and bacteria samples. Furthermore, the carcinogenicity of NPIP has been investigated using F344 male rats, and esophageal tumors were observed at a high incidence.
We are now analyzing the THP-dG levels using biological samples collected from subjects residing in both high- and low-risk areas. Moreover, mutational profiles of esophageal tumors in the rats fed NPIP are also being investigated.