Xue Cao, Tim Holland-Letz, Qiuqiong Tang, Xiaomeng Li, Melanie Gündert, Katarina Cuk, Sarah Schott, Jörg Heil, Michael Golatta, Christof Sohn, Andreas Schneeweiss and Barbara Burwinkel
Breast cancer is the most frequent malignancy with high mortality among woman around the world. Global DNA methylation has been investigated by multiple studies and suggested as a screening biomarker for cancer. DNA methylation for two repetitive elements, LINE1 and Alu, was investigated in whole blood DNA from 229 breast cancer patients and 151 controls by using MassARRAY EpiTyper assay. Results showed that the mean methylation level of investigated CpG sites of LINE1 in peripheral blood from breast cancer patients was lower than that in controls (P=8.78E-06), especially for one specific CpG site (LINE1_CpG_1 with P=3.64E-10). ROC curve analysis of LINE1_CpG_1 methylation and LINE1 mean methylation was used to estimate the potential clinical utility of LINE1 methylation, area under the curve (AUC) was 0.73 (95% confidence interval (CI): 0.68-0.79) and 0.68 (95% CI: 0.62-0.74), respectively. In addition, the highest increased risk was observed in the lowest quartile of LINE1_CpG_1 methylation and LINE1 mean methylation (odds ratio (OR)=38.47 and 5.94; 95% CI: 8.77-168.64 and 2.94-11.98; P for trend=1.42E-07 and 1.33E-05 respectively). For Alu, significant hypomethylation of Alu_CpG_13 and Alu_ CpG_14 in peripheral blood of breast cancer cases compared to controls was observed (P=0.002 and P=0.006). For the combined analysis, the AUC of the 10 most important CpG sites of LINE1 and Alu is 0.77 (95% CI: 0.72-0.83). Our study indicates that hypomethylation of specific CpG sites in LINE1 and Alu elements in peripheral blood DNA could be potential biomarkers for breast cancer risk. Further multicenter prospective studies are needed to verify these results.
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