Title: Examination of whole blood DNA methylation as a potential risk marker for gastric cancer

Whole blood DNA methylation analysis has been proposed to be a risk marker for cancer that can be used to target patients for preventive interventions. To test this, we examined whole blood DNA methylation of 16 CpG island promoters and LINE1 repetitive element in gastric cancer (GC) patients and control subjects. Bisulfite pyrosequencing was used to quantify the methylation of 14 CpG island promoters (MINT25, RORA, GDNF, CDH1, RARAB2, ER, CDH13, MYOD1, SFRP1, P2RX7, SLC16A12, IGF2, DPYS, and N33) and LINE1 from 72 GC, 67 control, and 52 healthy young individuals. Quantitative methylation-specific real-time PCR (qMSP) was also performed for 3 CpG island promoters (MINT25, MYO3A, and SOX11). Among all sites tested, only a marginal increase in the methylation of the SFRP1 promoter was observed in the blood of GC patients when compared to the control group (11.3% vs. 10.5%; age-adjusted p value: p=0.009), and this association was also seen in a validation set of 91 GC patients (11.5% vs. 10.5%; age-adjusted p value: p=0.001). The methylation of 9 sites (GDNF, CDH1, RARAB2, CDH13, MYOD1, SFRP1, SLC16A12, DPYS, N33, and LINE1) and their mean Z score was correlated with higher age (R=0.41, p<0.0001) and marginally with telomere shortening (R=-0.18, p=0.01) but not with gastric cancer risk (other than SFRP1 methylation). Variability in whole blood DNA methylation of cancer markers is primarily associated with aging, reflecting turnover of white blood cells, and has no direct link to GC predisposition. SFRP1 methylation in whole blood may be associated with gastric cancer risk. Cancer Research. on June 19, 2017. © 2013 American Association for cancerpreventionresearch.aacrjournals.org Downloaded from Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on August 13, 2013; DOI: 10.1158/1940-6207.CAPR-13-0034